TECHNICAL FIELD

This disclosure relates to optical communications networks.

BACKGROUND

In an optical communications network, network nodes (e.g., computer devices) can exchange information using one or more of optical links (e.g., lengths of optical fiber) extending between them. For example, a first network node and a second network node can be interconnected by one or more optical links. The first network node can transmit data to the second network node by generating an optical signal, modulating the optical signal based on the data (e.g., using one more optical sub-carriers), and transmitting the optical signal over the one or more optical links. The second node can demodulate the optical signal to recover the data.

However, in some cases, one or more of the optical links of an optical communications network may be severed or otherwise rendered inoperable. For example, an optical link may be physically severed (e.g., due to a “fiber cut”), such that it cannot convey optical signals from one end of the optical link to the other. As another example, an optical link and/or the equipment coupled along the optical fibers (e.g., “line system components”) may be misconfigured or experience a malfunction, such that optical signals are not conveyed accurately (or not conveyed at all) through the optical communications network. Accordingly, the connectivity between nodes of the optical communications network may be interrupted, and the reliability of the communications network may be degraded.

SUMMARY

In an aspect, a system includes a first network device having first circuitry. The first network device is configured to perform operations including receiving data to be transmitted to a second network device over an optical communications network; and transmitting, to the second device: first information indicative of the data using a first communications link of the optical communications network, where the first information is transmitted using a first subset of optical subcarriers, and second information indicative of the data using a second communications link of the optical communications network, where the second information is transmitted using a second subset of optical subcarriers, and where the first subset of optical subcarriers is different from the second subset of optical subcarriers.

Implementations of this aspect can include one or more of the following features.

In some implementations, the first information and the second information can be identical.

In some implementations, the first information can be different from the second information.

In some implementations, the first communications link and the second communications link can form at least a portion of a communications ring that communicatively interconnects the first network device and the second network device.

In some implementations, the first subset of optical subcarriers can be selected from a plurality of optical subcarriers allotted to the first network device.

In some implementations, the optical subcarriers of the first subset of optical subcarriers can be associated with respective frequencies that are contiguous with one another in a frequency domain.

In some implementations, the second subset of optical subcarriers can be selected from the plurality of optical subcarriers allotted to the first network device.

In some implementations, the optical subcarriers of the second subset of optical subcarriers can be associated with respective frequencies that are contiguous with one another in a frequency domain.

In some implementations, the first subset of optical subcarriers can be associated with one or more first frequencies. The second subset of optical subcarriers can be associated with one or more second frequencies. In some implementations, the one or more first frequencies are not contiguous with the one or more second frequencies in a frequency domain.

In some implementations, the first subset of optical subcarriers can be associated with one or more first frequencies, the second subset of optical subcarriers can be associated with one or more second frequencies, and one or more additional optical subcarriers can be associated with one or more additional frequencies. The one or more additional frequencies can be disposed between the one or more first frequencies and the one or more second frequencies in a frequency domain.

In some implementations, the first subset of optical subcarriers can be associated with one or more first frequencies, and the second subset of optical subcarriers can be associated with one or more second frequencies. The one or more first frequencies and the one or more second frequencies can be separated from one another by one or more additional frequencies in a frequency domain.

In some implementations, a number of optical subcarriers in the first subset of optical subcarriers can be the same as a number of optical subcarriers in the second subset of optical sub carriers.

In some implementations, a number of optical subcarriers in the first subset of optical subcarriers can be different from a number of optical subcarriers in the second subset of optical sub carriers.

In some implementations, the first network device can be configured to transmit the first information and the second information by modulating an output of a laser to generate a modulated optical signal including the first subset of optical subcarriers and the second subsets of optical subcarriers; providing the modulated optical signal to an optical splitter; splitting the modulated optical signal into a first portion and a second portion, where each of the first portion and the second portion includes the first subset of optical subcarriers and the second subset of optical subcarriers; selecting the first subset of optical subcarriers from the first portion of the modulated optical signal; selecting the second subset of subcarriers from the second portion of the modulated optical signal; transmitting the first subset of optical subcarriers to the second network device using the first communications link; and transmitting the second subset of optical subcarriers to the second network device using the second communications link.

In some implementations, the first network device can be configured to select the first subset of optical subcarriers by selecting the first subset of optical subcarriers with a wavelength selective switch.

In some implementations, the first network device can be configured to select the second subset of optical subcarriers by selecting the second subset of optical subcarriers with the wavelength selective switch.

In some implementations, the first network device can include one or more hub network devices. The second network device can include one or more leaf network devices.

In some implementations, each of the optical subcarriers in the first subset of optical subcarriers and the second subset of optical subcarriers can be a respective Nyquist subcarrier.

In another aspect, a system includes a first network device having first circuitry and a second network device having second circuitry. The first network device and the second network device are configured to perform operations including receiving, by the first network device and the second network device, data to be transmitted to a third network device over an optical communications network; transmitting, by the first network device to the third network device, first information indicative of the data using a first communications link of the optical communications network, where the first information is transmitted using a first subset of optical subcarriers; and transmitting, by the second network device to the third network device, second information indicative of the data using a second communications link of the optical communications network, where the second information is transmitted using a second subset of optical subcarriers, and where the first subset of optical subcarriers is different from the second subset of optical subcarriers.

Implementations of this aspect can include one or more of the following features.

In some implementations, the first information and the second information can be identical.

In some implementations, the first information can be different from the second information.

In some implementations, the first communications link and the second communications link can form at least a portion of a communications ring that communicatively interconnects the first network device, the second network device, and the third network device.

In some implementations, the first subset of optical subcarriers can be selected from a plurality of optical subcarriers allotted to the first network device.

In some implementations, the optical subcarriers of the first subset of optical subcarriers can be associated with respective frequencies that are contiguous with one another in a frequency domain.

In some implementations, the second subset of optical subcarriers can be selected from the plurality of optical subcarriers allotted to the first network device.

In some implementations, the optical subcarriers of the second subset of optical subcarriers can be associated with respective frequencies that are contiguous with one another in a frequency domain.

In some implementations, the first subset of optical subcarriers can be associated with one or more first frequencies, and the second subset of optical subcarriers can be associated with one or more second frequencies. In some implementations, the one or more first frequencies are not contiguous with the one or more second frequencies in a frequency domain.

In some implementations, the first subset of optical subcarriers can be associated with one or more first frequencies, the second subset of optical subcarriers can be associated with one or more second frequencies, and one or more additional optical subcarriers can be associated with one or more additional frequencies. The one or more additional frequencies can be disposed between the one or more first frequencies and the one or more second frequencies in a frequency domain.

In some implementations, the first subset of optical subcarriers can be associated with one or more first frequencies, and the second subset of optical subcarriers can be associated with one or more second frequencies. The one or more first frequencies and the one or more second frequencies can be separated from one another by one or more additional frequencies in a frequency domain.

In some implementations, a number of optical subcarriers in the first subset of optical subcarriers can be the same as a number of optical subcarriers in the second subset of optical sub carriers.

In some implementations, a number of optical subcarriers in the first subset of optical subcarriers can be different from a number of optical subcarriers in the second subset of optical sub carriers.

In some implementations, the first network device can be configured to transmit the first information by modulating an output of a first laser to generate a first modulated optical signal including the first subset of optical subcarriers; and transmitting the first modulated optical signal to the third network device using the first communications link.

In some implementations, the second network device can be configured to transmit the second information by modulating an output of a second laser to generate a second modulated optical signal including the second subset of optical subcarriers; and transmitting the second modulated optical signal to the third network device using the first communications link.

In some implementations, each of the first network device and the second network device can include one or more hub network devices, and the third network device can include one or more leaf network devices.

In some implementations, each of the optical subcarriers in the first subset of optical subcarriers and the second subset of optical subcarriers can be a respective Nyquist subcarrier.

In another aspect, a system includes a first network device having first circuitry. The first network device is configured to perform operations including receiving data to be transmitted to a second network device over an optical communications network; transmitting, to the second device, first information indicative of the data using a first communications link of the optical communications network, where the first information is transmitted using a first subset of optical subcarriers; determining a fault in the first communications link; and responsive to determining the fault in the first communications link, transmitting, to the second network device, second information indicative of the data using a second communications link of the optical communications network, where the second information is transmitted using a second subset of optical subcarriers, and where the first subset of optical subcarriers is different from the second subset of optical subcarriers.

Implementations of this aspect can include one or more of the following features.

In some implementations, the first network device can be configured to determine the fault in the first communications link by determining that an optical fiber of the first communications link has been severed.

In some implementations, the first network device is configured to determine the fault in the first communications link by determining that a line system component of the first communications link is malfunctioning.

In some implementations, the first information and the second information can be identical.

In some implementations, the first information can be different from the second information.

In some implementations, the first communications link and the second communications link can form at least a portion of a communications ring that communicatively interconnects the first network device and the second network device.

In some implementations, the first subset of optical subcarriers can be selected from a plurality of optical subcarriers allotted to the first network device.

In some implementations, the optical subcarriers of the first subset of optical subcarriers can be associated with respective frequencies that are contiguous with one another in a frequency domain.

In some implementations, the second subset of optical subcarriers can be selected from the plurality of optical subcarriers allotted to the first network device.

In some implementations, the optical subcarriers of the second subset of optical subcarriers can be associated with respective frequencies that are contiguous with one another in a frequency domain.

In some implementations, the first subset of optical subcarriers can be associated with one or more first frequencies, and the second subset of optical subcarriers can be associated with one or more second frequencies. In some implementations, the one or more first frequencies are not contiguous with the one or more second frequencies in a frequency domain.

In some implementations, the first subset of optical subcarriers can be associated with one or more first frequencies, the second subset of optical subcarriers can be associated with one or more second frequencies, and one or more additional optical subcarriers can be associated with one or more additional frequencies. The one or more additional frequencies can be disposed between the one or more first frequencies and the one or more second frequencies in a frequency domain.

In some implementations, the first subset of optical subcarriers can be associated with one or more first frequencies, and the second subset of optical subcarriers can be associated with one or more second frequencies. The one or more first frequencies and the one or more second frequencies can be separated from one another by one or more additional frequencies in a frequency domain.

In some implementations, a number of optical subcarriers in the first subset of optical subcarriers can be the same as a number of optical subcarriers in the second subset of optical sub carriers.

In some implementations, a number of optical subcarriers in the first subset of optical subcarriers can be different from a number of optical subcarriers in the second subset of optical sub carriers.

In some implementations, the first network device can include one or more hub network devices, and the second network device can include one or more leaf network devices.

In some implementations, each of the optical subcarriers in the first subset of optical subcarriers and the second subset of optical subcarriers can be a respective Nyquist subcarrier.

In another aspect, a system includes a first network device including first circuitry. The first network device is configured to perform operations including monitoring for incoming optical signals on a first communications link and a second communications link of an optical communications network, where each of the first communications link and the second communications link communicatively interconnects the first network device and a second network device; receiving, by the first network device, at least one of: a first signal including first information indicative of data transmitted by the second network device using the first communications link and using a first subset of optical subcarriers, or a second signal including second information indicative of the data transmitted by the second network device using the second communications link and using a second subset of optical subcarriers, where the first subset of optical subcarriers is different from the second subset of optical subcarriers; and retrieving, by the first network device, the data from at least one of the first signal or the second signal.

Implementations of this aspect can include one or more of the following features.

In some implementations, the first network device can be further configured to perform at least one of: transmitting the data to a third network device, or transmitting the data to the third network device.

In some implementations, the first communications link and the second communications link can form at least a portion of a communications ring that communicatively interconnects the first network device and the second network device.

In some implementations, the optical subcarriers of the first subset of optical subcarriers can be associated with respective frequencies that are contiguous with one another in a frequency domain.

In some implementations, the optical subcarriers of the second subset of optical subcarriers can be associated with respective frequencies that are contiguous with one another in the frequency domain.

In some implementations, the first frequencies are not contiguous with the second frequencies in the frequency domain.

In some implementations, one or more additional optical subcarriers can be associated with one or more additional frequencies, and the one or more additional frequencies can be disposed between the one or more first frequencies and the one or more second frequencies in the frequency domain.

In some implementations, the first subset of optical subcarriers can be associated with one or more first frequencies, and the second subset of optical subcarriers can be associated with one or more second frequencies. The one or more first frequencies and the one or more second frequencies can be separated from one another by one or more additional frequencies in the frequency domain.

In some implementations, a number of optical subcarriers in the first subset of optical subcarriers can be the same as a number of optical subcarriers in the second subset of optical sub carriers.

In some implementations, a number of optical subcarriers in the first subset of optical subcarriers can be different from a number of optical subcarriers in the second subset of optical sub carriers.

In some implementations, wherein the first network device can be configured to retrieve the data from at least one of the first signal or the second signal by determining that the first signal was not received from the second network device; determining that the second signal was received from the second network device; and responsive to determining that the first signal was not received from the second network device and determining that the second signal was received from the second network device, retrieving the data from the second signal.

In some implementations, the first network device can be configured to monitor for incoming optical signals on the first communications link and the second communications link by tuning a receiver of the first network device to one or more first frequencies associated with the first subset of optical subcarriers, and responsive to determining that the first signal was not received from the second network device, tuning the receiver of the first network device to one or more second frequencies associated with the second subset of optical subcarriers.

In some implementations, the first network device can be configured to retrieve the data from at least one of the first signal or the second signal can include determining that the first signal was received from the second network device; determining one or more first quality metrics associated with the first signal; determining that the second signal was received from the second network device; determining one or more second quality metrics associated with the second signal; and retrieving, based on the one or more first quality metrics and the one or more second quality metrics, the data from one of the first signal or the second signal.

In some implementations, at least one of the one or more first quality metrics can include an indication of a latency associated with a transmission of the first signal using the first communications link.

In some implementations, at least one of the one or more first quality metrics can include an indication of a pre-forward error correction quality factor (pre-FEC Q) associated with a transmission of the first signal using the first communications link.

In some implementations, at least one of the one or more second quality can include an indication of a latency associated with a transmission of the second signal using the second communications link.

In some implementations, at least one of the one or more second quality can include an indication of a forward error correction quality factor (pre-FEC Q) associated with a transmission of the second signal using the second communications link.

In some implementations, the first network device can include one or more hub network devices, and the second network device can include one or more leaf network devices.

In some implementations, each of the optical subcarriers in the first subset of optical subcarriers and the second subset of optical subcarriers can be a respective Nyquist subcarrier.

In another aspect, an apparatus includes a digital signal processor that is operable to receive information signals including plurality of bits of information and provide a plurality of digital signals based on the information signals; digital-to-analog conversion circuitry operable to receive the digital signals from the digital signal processor and provide a plurality of analog signals based on the digital signals; driver circuitry operable to output drive signals based on the analog signals; a laser operable to provide an optical signal; and an optical modulator operable to modulate at least a portion of the optical signal based on the drive signals to provide a modulated optical signal. The modulated optical signal includes a first group of optical subcarriers and a second group of optical subcarriers. The first group of optical subcarriers includes a first optical subcarrier and the second group of optical subcarriers includes a second optical subcarrier. The first optical subcarrier carries first data and the second optical subcarrier carries second data. The first and second data are indicative of the plurality of bits of information.

Implementations of this aspect can include one or more of the following features.

In some implementations, the first data can be the same as the second data.

In some implementations, a guard band can spectrally separate first frequencies associated with the first group of optical subcarriers from second frequencies associated with the second group of optical subcarriers.

In some implementations, the apparatus can include an optical splitter. The splitter can have an input and first and second outputs. The input can be operable to receive the modulated optical signal. The first output can be operable to supply a first portion of the modulated optical signal. The second output can be operable to supply a second portion of modulated optical signal.

In some implementations, the first portion of the modulated optical signal can be a first power-split portion of the modulated optical signal and the second portion of the modulated optical signal can be a second power-split portion of the modulated optical signal.

In some implementations, the apparatus can include a wavelength selective switch that receives the first portion of the modulated optical signal.

In some implementations, the apparatus can include a first wavelength selective switch that receives the first portion of the modulated optical signal; and a second wavelength selective switch that receives the second portion of the modulated optical signal.

In some implementations, the first wavelength selective switch can supply the first group of optical subcarriers to a first optical communication path including a first optical fiber and the second wavelength selective switch can supply the second group of optical subcarriers to a second optical communication path including a second optical fiber.

In some implementations, each optical subcarrier in the first group of optical subcarriers can be a Nyquist subcarrier.

In some implementations, the apparatus can include a wavelength selective switch that receives the first portion of the modulated optical signal and the second portion of the modulated optical signal.

In some implementations, the wavelength selective switch can supply the first group of optical subcarriers to a first optical communication path including a first optical fiber, and the wavelength selective switch can supply the second group of optical subcarriers to a second optical communication path including a second optical fiber.

In some implementations, the apparatus can include an optical splitter. The optical splitter can receive the optical signal from the laser and supply said at least a portion of the optical signal to the modulator.

In another aspect, an apparatus includes a polarization beam splitter that is operable to receive a modulated optical signal. The modulated optical signal includes a plurality of optical subcarriers. The modulated optical signal includes a first group of optical subcarriers and a second group of optical subcarriers, The first group of optical subcarriers includes a first optical subcarrier and a second optical subcarrier. The second group of optical subcarriers includes a third optical subcarrier and a fourth optical subcarrier. The first optical subcarrier carries first data and the second optical subcarrier carrying second data. The third optical subcarrier carries third data and the fourth optical subcarrier carrying fourth data. The first data is indicative of a first plurality of bits of information and the third data is indicative of the first plurality of bits of information. The second data is indicative of a second plurality of bits of information and the fourth data is indicative of the second plurality of bits of information. The apparatus also includes optical hybrid circuitry operable to receive outputs from the polarization beam splitter and supply a plurality of optical mixing products; photodetector circuitry operable to supply electrical signals based on the plurality of optical mixing products; analog-to-digital conversion circuitry operable to provide digital signals based on the electrical signals; and a digital signal processor operable to output the first plurality of bits of information and the second plurality of bits of information based on digital signals.

Implementations of this aspect can include one or more of the following features.

In some implementations, the first data can be the same as the third data.

In some implementations, a guard band can spectrally separate first frequencies associated with the first group of optical subcarriers from second frequencies associated with the second group of optical subcarriers.

In some implementations, the apparatus can include an optical combiner having a first input that receives a first portion of the modulated optical signal and a second input that receives a second portion of the modulated optical signal. The first portion of the modulated optical signal can include the first plurality of optical subcarriers and the second portion of the modulated optical signal can include the second plurality of optical subcarriers. The optical combiner can have an output that supplies the modulated optical signal.

In some implementations, the apparatus can include a first wavelength selective switch operable to be coupled to a first optical communication path including a first optical fiber. The first wavelength selective switch can be operable to receive the first portion of the modulated optical signal from the first optical communication path and supply the first portion of the modulated optical signal to the first input of the optical combiner. The apparatus can also include a second wavelength selective switch operable to be coupled to a second optical communication path including a second optical fiber. The second wavelength selective switch can be operable to receive the second portion of the modulated optical signal from the second optical communication path and supply the second portion of the modulated optical signal to the second input of the optical combiner.

In some implementations, the apparatus can include a wavelength selective switch operable to be coupled to a first optical communication path including a first optical fiber and a second optical communication path including a second optical fiber. The wavelength selective switch can be operable to receive the first portion of the modulated optical signal from the first optical communication path and supply the first portion of the modulated optical signal to the first input of the optical combiner. The wavelength selective switch can be operable to receive the second portion of the modulated optical signal from the second optical communication path and supply the second portion of the modulated optical signal to the second input of the optical combiner.

In some implementations, that apparatus can include a local oscillator laser that supplies light. At least a portion of the light can be supplied to the optical hybrid circuitry.

In some implementations, the apparatus can include an optical splitter that receives the light from the local oscillator laser and supplies to the portion of the light to the optical hybrid circuitry.

In another aspect, an apparatus includes a first digital signal processor that is operable to receive information signals including a first plurality of bits of information and provide a first plurality of digital signals based on the information signals; digital-to-analog conversion circuitry operable to receive the first plurality of digital signals from the first digital signal processor and provide a plurality of analog signals based on the digital signals; driver circuitry operable to output drive signals based on the analog signals; an optical modulator operable to modulate an optical signal based on the drive signals to provide a first modulated optical signal, the first modulated optical signal including a first group of optical subcarriers and a second group of optical subcarriers, the first group of optical subcarriers including a first optical subcarrier and the second group of optical subcarriers including a second optical subcarrier, the first optical subcarrier carrying first data and the second optical subcarrier carrying second data, the first and second data being indicative of the first plurality of bits of information; a polarization beam splitter that is operable to receive a second modulated optical signal, the second modulated optical signal including a third group of optical subcarriers and a fourth group of optical subcarriers, the third group of optical subcarriers including a third optical subcarrier and the fourth group of optical subcarriers including a fourth optical subcarrier, the third optical subcarrier carrying third data and the fourth optical subcarrier carrying fourth data, the third data being indicative of a second plurality of bits of information and the second data being indicative of the second plurality of bits of information; optical hybrid circuitry operable to receive outputs from the polarization beam splitter and supply a plurality of optical mixing products; photodetector circuitry operable to supply electrical signals based on the plurality of optical mixing products; analog-to-digital conversion circuitry operable to provide a second plurality of digital signals based on the electrical signals; and a digital signal processor operable to output the second plurality of bits based on the second plurality of digital signals.

Implementations of this aspect can include one or more of the following features.

In some implementations, each subcarrier of the first group of optical subcarriers can have a corresponding one of a first plurality of frequencies and each subcarrier of the third group of optical subcarriers can have a corresponding one of the first plurality of frequencies.

In some implementations, each subcarrier of the second group of optical subcarriers can have a corresponding one of a second plurality of frequencies and each subcarrier of the fourth group of optical subcarriers can have a corresponding one of the second plurality of frequencies.

In some implementations, each optical subcarrier of the first group of optical subcarriers, each optical subcarrier of the second group of optical subcarriers, each optical subcarriers of the third group of optical subcarriers, and each optical subcarrier of the fourth group of optical subcarriers can be a Nyquist subcarrier.

In some implementations, the first data can be the same as the second data and the third data can be the same as the fourth data.

In some implementations, a guard band can spectrally separate first frequencies associated with the first group of optical subcarriers from second frequencies associated with the second group of optical subcarriers.

In some implementations, the apparatus can include an optical splitter having an input that receives the first modulated optical signal, a first output that supplies a first portion of the first modulated optical signal and a second output that supplies a second portion of the first modulated optical signal.

In some implementations, the apparatus can include an optical combiner having a first input that receives a first portion of the second modulated optical signal including the third group of optical subcarriers and a second portion of the second modulated optical including the fourth group of the optical subcarriers.

In some implementations, the apparatus can include a first wavelength selective switch that receives the first portion of the first modulated optical signal and supplies the first group of optical subcarriers to a first optical communication path including a first optical fiber; and a second wavelength selective switch that receives the second portion of the first modulated optical signal and supplies the second group of optical subcarriers to a second optical communication path including a second optical fiber.

In some implementations, the apparatus can include a third wavelength selective switch operable to be coupled to the second optical communication path including the second optical fiber. The third wavelength selective switch can be operable to receive the first portion of the second modulated optical signal including the third group of optical subcarriers from the second optical communication path and supply the first portion of the second modulated optical signal to the first input of the optical combiner. The apparatus can also include a fourth wavelength selective switch operable to be coupled to the first optical communication path including the first optical fiber. The fourth wavelength selective switch can be operable to receive the second portion of the second modulated optical signal including the fourth group of subcarriers from the first optical communication path and supply the second portion of the second modulated optical signal to the second input of the optical combiner.

In some implementations, the apparatus can include a first wavelength selective switch operable to receive the first portion of the first modulated optical signal and the second portion of the first modulated optical signal. The first wavelength selective switch can supply the first group of optical subcarriers to a first optical communication path including a first optical fiber. The first wavelength selective switch can supply the second group of optical subcarriers to a second optical communication path including a second optical fiber. The apparatus can also include a second wavelength selective switch operable to be coupled to the second optical communication path including the second optical fiber and can be operable to receive the first portion of the second modulated optical signal from the second optical communication path and supply the first portion of the second modulated optical signal including the third group of optical subcarriers to the first input of the optical combiner. The second wavelength selective switch can be operable to be coupled to the first optical communication path including the first optical fiber. The second wavelength selective switch can be operable to receive the second portion of the second modulated optical signal including the fourth plurality of optical subcarriers from the first optical communication path and supply the second portion of the second modulated optical signal to the second input of the optical combiner.

In another aspect, an apparatus includes a digital signal processor that is operable to receive a plurality of bits of information and provide a plurality of digital signals based on the plurality of bits of information; digital-to-analog conversion circuitry operable to receive the digital signals from the digital signal processor and provide a plurality of analog signals based on the digital signals; driver circuitry operable to output drive signals based on the analog signals; a laser operable to provide an optical signal; and an optical modulator operable to modulate at least a portion of the optical signal based on the drive signals to provide a modulated optical signal. The modulated optical signal includes a first optical subcarriers and a second optical subcarrier. The first optical subcarrier carries first data and the second optical subcarrier carries second data. The first and second data are indicative of the plurality of bits of information.

Implementations of this aspect can include one or more of the following features.

In some implementations, the first data can be the same as the second data.

In some implementations, the apparatus can include an optical splitter. The splitter can have an input and first and second outputs. The input can be operable to receive the modulated optical signal. The first output can be operable to supply a first portion of the modulated optical signal. The second output can be operable to supply a second portion of modulated optical signal.

In some implementations, the first portion of the modulated optical signal can be a first power-split portion of the modulated optical signal and the second portion of the modulated optical signal can be a second power-split portion of the modulated optical signal.

In some implementations, the apparatus can include a wavelength selective switch that receives the first portion of the modulated optical signal.

In some implementations, the apparatus can include a first wavelength selective switch that receives the first portion of the modulated optical signal; and a second wavelength selective switch that receives the second portion of the modulated optical signal.

In some implementations, the first wavelength selective switch can supply the first optical subcarrier to a first optical communication path including a first optical fiber and the second wavelength selective switch can supply the second optical subcarrier to a second optical communication path including a second optical fiber.

In some implementations, each of the first and second optical subcarriers can be a Nyquist subcarrier.

In some implementations, the apparatus can include a wavelength selective switch that receives the first portion of the modulated optical signal and the second portion of the modulated optical signal.

In some implementations, the wavelength selective switch can supply the first optical subcarrier to a first optical communication path including a first optical fiber, and the wavelength selective switch can supply the second group of optical subcarriers to a second optical communication path including a second optical fiber.

In some implementations, the apparatus can include an optical splitter. The optical splitter can receive the optical signal from the laser and supply said at least a portion of the optical signal to the modulator.

In another aspect, an apparatus includes a polarization beam splitter that is operable to receive a first modulated optical signal and a second modulated optical signal. The first modulated optical signal includes a first group of optical subcarriers and the second modulated optical signal includes a second group of optical subcarriers. The first group of optical subcarriers includes a first optical subcarrier. The second group of optical subcarriers includes a second optical subcarrier. The first optical subcarrier carries first data and the second optical subcarrier carrying second data. The first data is indicative of a plurality of bits of information. The second data is indicative of the plurality of bits of information. The apparatus also includes optical hybrid circuitry operable to receive outputs from the polarization beam splitter and supply a plurality of optical mixing products; photodetector circuitry operable to supply electrical signals based on the plurality of optical mixing products; analog-to-digital conversion circuitry operable to provide digital signals based on the electrical signals; and a digital signal processor operable to output the plurality of bits based on the digital signals.

Implementations of this aspect can include one or more of the following features.

In some implementations, the first data can be the same as the second data.

In some implementations, a guard band can spectrally separate first frequencies associated with the first group of optical subcarriers from second frequencies associated with the second group of optical subcarriers.

In some implementations, the apparatus can include an optical combiner having a first input that receives the first modulated optical signal and a second input that receives the second modulated optical signal. The optical combiner can have an output that supplies the first and the second modulated optical signals.

In some implementations, the apparatus can include a first wavelength selective switch operable to be coupled to a first optical communication path including a first optical fiber. The first wavelength selective switch can be operable to receive the first modulated optical signal from the first optical communication path and supply the first modulated optical signal to the first input of the optical combiner. The apparatus can also include a second wavelength selective switch operable to be coupled to a second optical communication path including a second optical fiber. The second wavelength selective switch can be operable to receive the second modulated optical signal from the second optical communication path and supply the second modulated optical signal to the second input of the optical combiner.

In some implementations, the apparatus can include a wavelength selective switch operable to be coupled to a first optical communication path including a first optical fiber and a second optical communication path including a second optical fiber. The wavelength selective switch can be operable to receive the first modulated optical signal from the first optical communication path and supply the first modulated optical signal to the first input of the optical combiner. The wavelength selective switch can be operable to receive the second modulated optical signal from the second optical communication path and supply the second modulated optical signal to the second input of the optical combiner.

In some implementations, the apparatus can include a local oscillator laser that supplies light, at least a portion of the light being supplied to the optical hybrid circuitry.

In some implementations, the apparatus can include an optical splitter that receives the light from the local oscillator laser and supplies to the portion of the light to the optical hybrid circuitry.

In another aspect, an apparatus includes a first digital signal processor that is operable to receive a first plurality of bits of information and provide a first plurality of digital signals based on the first plurality of bits of information; digital-to-analog conversion circuitry operable to receive the first plurality of digital signals from the first digital signal processor and provide a plurality of analog signals based on the digital signals; driver circuitry operable to output drive signals based on the analog signals; an optical modulator operable to modulate an optical signal based on the drive signals to provide a first modulated optical signal, the first modulated optical signal including a first optical subcarrier and a second optical subcarrier, the first optical subcarrier carrying first data and the second optical subcarrier carrying second data, the first and second data being indicative of the first plurality of bits of information; a polarization beam splitter that is operable to receive a second modulated optical signal, the second modulated optical signal including a first group of optical subcarriers and a second group of optical subcarriers, the first group of optical subcarriers including a third optical subcarrier and the second group of optical subcarriers including a fourth optical subcarrier, the third optical subcarrier carrying third data and the fourth optical subcarrier carrying fourth data, the third data being indicative of a second plurality of bits of information and the second data being indicative of the second plurality of bits of information; optical hybrid circuitry operable to receive outputs from the polarization beam splitter and supply a plurality of optical mixing products; photodetector circuitry operable to supply electrical signals based on the plurality of optical mixing products; analog-to-digital conversion circuitry operable to provide a second plurality of digital signals based on the electrical signals; and a second digital signal processor operable to output the second plurality of bits based on the second plurality of digital signals.

Implementations of this aspect can include one or more of the following features.

In some implementations, each subcarrier of the first group of optical subcarriers can have a corresponding one of a first plurality of frequencies and each subcarrier of the second group of optical subcarriers can have a corresponding one of a second plurality of frequencies. The first optical subcarrier can have one of the first plurality of frequencies, and the second optical subcarrier can have said one of the first plurality of frequencies.

In some implementations, each of the first and second optical subcarriers can be a Nyquist subcarrier.

In some implementations, the first data can be the same as the second data and the third data is the same as the fourth data.

In some implementations, a guard band can spectrally separate first frequencies associated with the first group of optical subcarriers from second frequencies associated with the second group of optical subcarriers.

In some implementations, the apparatus can include an optical splitter having an input that receives the first modulated optical signal, a first output that supplies a first portion of the first modulated optical signal and a second output that supplies a second portion of the first modulated optical signal.

In some implementations, the apparatus can include an optical combiner having a first input that receives a first portion of the second modulated optical signal including the first group of optical subcarriers and a second portion of the second modulated optical including the second group of optical subcarriers.

In some implementations, the apparatus can include a first wavelength selective switch that is operable to receive the first portion of the first modulated optical signal and supply the first optical subcarrier to a first optical communication path including a first optical fiber; and a second wavelength selective switch that receives the second portion of the first modulated optical signal and supplies the second optical subcarrier to a second optical communication path including a second optical fiber.

In some implementations, the apparatus can include a third wavelength selective switch operable to be coupled to the second optical communication path including the second optical fiber. The third wavelength selective switch can be operable to receive the first portion of the second modulated optical signal including the first group of optical subcarriers from the second optical communication path and supply the first portion of the second modulated optical signal to the first input of the optical combiner. The apparatus can also include a fourth wavelength selective switch operable to be coupled to the first optical communication path including the first optical fiber. The fourth wavelength selective switch can be operable to receive the second portion of the second modulated optical signal including the fourth optical subcarrier from the first optical communication path and supply the second portion of the second modulated optical signal to the second input of the optical combiner.

In some implementations, the apparatus can include a first wavelength selective switch operable to receive the first portion of the first modulated optical signal and the second portion of the first modulated optical signal. The first wavelength selective switch can supply the first optical subcarrier to a first optical communication path including a first optical fiber. The first wavelength selective switch can supply the second optical subcarrier to a second optical communication path including a second optical fiber. The apparatus can also include a second wavelength selective switch operable to be coupled to the second optical communication path including the second optical fiber and operable to receive the first portion of the second modulated optical signal from the second optical communication path and supply the first portion of the second modulated optical signal including the first group of optical subcarriers to the first input of the optical combiner. The second wavelength selective switch can be operable to be coupled to the first optical communication path including the first optical fiber. The second wavelength selective switch can be operable to receive the second portion of the second modulated optical signal including the second group of optical subcarriers from the first optical communication path and supply the second portion of the second modulated optical signal to the second input of the optical combiner.

As another aspect, an apparatus includes a digital signal processor that is operable to receive a plurality of bits of information and provide a plurality of digital signals based on the plurality of bits of information; digital-to-analog conversion circuitry operable to receive the digital signals from the digital signal processor and provide a plurality of analog signals based on the digital signals; driver circuitry operable to output drive signals based on the analog signals; a laser operable to provide an optical signal; an optical modulator operable to modulate at least a portion of the optical signal based on the drive signals to provide a modulated optical signal, the modulated optical signal including a an optical subcarrier, the optical subcarrier carrying data indicative of the plurality of bits of information; and an optical splitter operable to receive the modulated optical signal, the optical splitter having first and second outputs, the first output supplying a first portion of modulated optical signal and the second output supplying a second portion of the modulated optical signal.

Implementations of this aspect can include one or more of the following features.

In some implementations, the first portion of the modulated optical signal can be supplied to a first optical communication path including a first optical fiber and the second portion of the modulated optical signal can be supplied to a second optical communication path including a second optical fiber.

In some implementations, the first portion of the modulated optical signal can be a first power-split portion of the modulated optical signal and the second portion of the modulated optical signal can be a second power-split portion of the modulated optical signal.

In some implementations, the apparatus can further include a wavelength selective switch that receives the first portion of the modulated optical signal and supplies the first portion of the modulated optical signal to an optical communication path including an optical fiber.

In some implementations, the apparatus can further include a first wavelength selective switch that receives the first portion of the modulated optical signal and provides the first portion of the modulated optical signal to a first optical communication path including a first optical fiber; and a second wavelength selective switch that receives the second portion of the modulated optical signal and provides the second portion of the modulated optical signal to a second optical communication path including a second optical fiber.

In some implementations, the optical subcarrier can be a Nyquist subcarrier.

In some implementations, the apparatus can further include a wavelength selective switch that receives the first portion of the modulated optical signal and the second portion of the modulated optical signal.

In some implementations, the wavelength selective switch can supply the first portion of the modulated optical signal to a first optical communication path including a first optical fiber, and the wavelength selective switch can supply the second portion of the modulated optical signal to a second optical communication path including a second optical fiber.

In some implementations, the optical splitter can be a first optical splitter, and the apparatus can further include a second optical splitter operable to receive the optical signal from the laser and supply said at least a portion of the optical signal to the modulator.

In another aspect, an apparatus includes a first digital signal processor that is operable to receive a first plurality of bits of information and provide a first plurality of digital signals based on the first plurality of bits of information; digital-to-analog conversion circuitry operable to receive the first plurality of digital signals from the first digital signal processor and provide a plurality of analog signals based on the digital signals; driver circuitry operable to output drive signals based on the analog signals; an optical modulator operable to modulate an optical signal based on the drive signals to provide a first modulated optical signal, the first modulated optical signal including a first optical subcarrier, the first optical subcarrier carrying data indicative of the first plurality of bits of information; a splitter operable to receive the first modulated optical signal, the splitter having first and second outputs, the first output being operable to provide a first portion of the first modulated optical signal and the second output being operable to provide a second portion of the first modulated optical signal; a polarization beam splitter that is operable to receive a second modulated optical signal and a third modulated optical signal, the second modulated optical signal including a group of second optical subcarriers and a group of third optical subcarriers, the group of second optical subcarriers including a second optical subcarrier and the group of third optical subcarriers including a third optical subcarrier, the second optical subcarrier carrying second data and the third optical subcarrier carrying third data, the second data being indicative of a second plurality of bits of information and the third data being indicative of the second plurality of bits of information; optical hybrid circuitry operable to receive outputs from the polarization beam splitter and supply a plurality of optical mixing products; photodetector circuitry operable to supply electrical signals based on the plurality of optical mixing products; analog-to-digital conversion circuitry operable to provide a second plurality of digital signals based on the electrical signals; and a second digital signal processor operable to output the second plurality of bits based on the second plurality of digital signals.

Implementations of this aspect can include one or more of the following features.

In some implementations, each subcarrier of the group of second optical subcarriers can have a corresponding one of a first plurality of frequencies and each subcarrier of the group of third optical subcarriers can have a corresponding one of a second plurality of frequencies. The first optical subcarrier can have one of the first plurality of frequencies, and the second optical subcarrier can have said one of the second plurality of frequencies.

In some implementations, each of the first optical subcarrier, the group of second optical subcarriers, and the group of third optical subcarriers can be a Nyquist subcarrier.

In some implementations, the second data can be the same as the third data.

In some implementations, a guard band can spectrally separate first frequencies associated with the first optical subcarrier from second frequencies associated with the second group of optical subcarriers.

In some implementations, the apparatus can further include an optical combiner having a first input that receives the group of second optical subcarriers and the group of third optical subcarriers.

In some implementations, the apparatus can further include a first wavelength selective switch operable to receive the first portion of the first modulated optical signal and supply the first portion of the first modulated optical signal to a first optical communication path including a first optical fiber; and a second wavelength selective switch that receives the second portion of the first modulated optical signal and supplies the second portion of the first modulated optical signal to a second optical communication path including a second optical fiber.

In some implementations, the apparatus can further include a third wavelength selective switch operable to be coupled to the second optical communication path including the second optical fiber, the third wavelength selective switch being operable to receive the second modulated optical signal including the group of second optical subcarriers from the second optical communication path and supply the second modulated optical signal to the first input of the optical combiner; and a fourth wavelength selective switch operable to be coupled to the first optical communication path including the first optical fiber, the fourth wavelength selective switch being operable to receive the third modulated optical signal including the group of third optical sub carriers from the first optical communication path and supply the third modulated optical signal to the second input of the optical combiner.

In some implementations, the apparatus can further include an optical combiner having a first and second inputs and an output; a first wavelength selective switch operable to receive the first portion of the first modulated optical signal and the second modulated optical signal, where the first wavelength selective switch supplies the first portion of the modulated optical signal to a first optical communication path including a first optical fiber, and the first wavelength selective switch supplies the second modulated optical signal to the first input of the optical combiner; and a second wavelength selective switch operable to receive the second portion of the second modulated optical signal and the third modulated optical signal, where the second wavelength selective switch supplies the second portion of the first modulated optical to a second optical communication path including a second optical fiber, and the second wavelength selective switch supplies the third modulated optical signal to the second input of the optical combiner, the output of the optical combiner providing the second and third modulated optical signals to the polarization beam splitter.

In some implementations, the apparatus can further include an optical combiner having a first input that receives the second modulated optical signal, a second input that receives the second modulated optical signal, and an output that provides the second and third modulated optical signals to the polarization beam splitter.

In another aspect, an apparatus includes a first transmitter and a second transmitter. The first transmitter includes a first laser operable to provide a first optical signal, and a first modulator operable to provide a first modulated optical signal based on the first optical signal and a plurality of data stream provided to the first transmitter, the first modulated optical signal including a first plurality of optical subcarriers, such that the first transmitter is operable to supply the first modulated optical signal to a first optical communication path, the first plurality of optical subcarriers being associated with the plurality of data streams. The second transmitter is operable to receive the plurality of data streams. The second transmitter includes a second laser operable to provide a second optical signal; and a second modulator operable to provide a second modulated optical signal based on the second optical signal and the plurality of data streams, the second modulated optical signal including a second plurality of optical subcarriers, such that the second transmitter is operable to supply the second modulated optical signal to a second optical communication path, the second plurality of optical subcarriers being associated with the plurality of data streams.

Implementations of this aspect can include one or more of the following features.

In some implementations, each optical subcarrier of the first plurality of optical subcarriers and each optical subcarrier of the second plurality of optical subcarriers can be a Nyquist subcarrier.

In some implementations, the apparatus can further include a first wavelength selective switch operable to receive the first plurality of optical subcarriers from the first transmitter and supply the first plurality of optical subcarriers to the first optical communication path; and a second wavelength selective switch operable to receive the second plurality of optical subcarriers and supply the second plurality of optical subcarriers to the second optical communication path.

In some implementations, the optical signal provided by the first laser can have a first wavelength and the optical signal provided by the second laser can have a second wavelength different than the first wavelength.

In some implementations, each of the first plurality of optical subcarriers can have a corresponding one of a first plurality of frequencies, and each of the second plurality of optical subcarriers can have a corresponding one of a second plurality of frequencies.

In some implementations, each of the first plurality of frequencies can be different than each of the second plurality of frequencies.

In some implementations, the first transmitter further can include a first digital signal processor operable to provide first digital signals based on the first plurality of data streams, first digital-to-analog circuitry operable to provide first analog signals based on the first digital signals, and first driver circuitry operable to provide first drive signals to the first modulator based on the first analog signals. The second transmitter can include a second digital signal processor operable to provide second digital signals based on the first plurality of data streams, second digital-to-analog circuitry operable to provide second analog signals based on the second digital signals, and second driver circuitry operable to provide second drive signals to the second modulator based on the second analog signals.

In another aspect, an apparatus includes a first receiver, a second receiver, and a selection circuit. The first receiver includes a first polarization beam splitter operable to receive a first modulated optical signal from a first optical communication path, the first modulated optical signal including a first plurality of optical subcarriers associated with a plurality of data streams, and a first digital signal processor operable to provide an output based on the first plurality of optical subcarriers, the output of the first digital signal processor including the plurality of data streams. The second receiver includes a second polarization beam splitter operable to receive a second modulated optical signal from a second optical communication path, the second modulated optical signal including a second plurality of optical subcarriers, each of which being associated with the plurality of data streams, a second digital signal processor operable to provide an output based on the second plurality of optical subcarriers, the output of the second digital processor including the plurality of data streams. The selection circuit is coupled to the first digital signal processor and the second digital processor. The selection circuit is configured to selectively supply one of the output of the first digital signal processor and the output of the second digital processor.

Implementations of this aspect can include one or more of the following features.

In some implementations, each optical subcarrier of the first plurality of optical subcarriers and each optical subcarrier of the second plurality of optical subcarriers can be a Nyquist subcarrier.

In some implementations, the apparatus can further include a first wavelength selective switch operable to the supply the first plurality of optical subcarriers to the first receiver; and a second wavelength selective switch operable to supply the second plurality of optical subcarriers to the second receiver.

In some implementations, the apparatus can further include a first laser operable to provide a first local oscillator signal; a first optical hybrid circuit operable to receive the first local oscillator signal and outputs from the first polarization beam splitter; a second laser operable to provide a second local oscillator signal; and a second optical hybrid circuit operable to receive the second local oscillator signal the outputs from the second polarization beam splitter.

In some implementations, the first local oscillator signal can have a first wavelength and the second local oscillator signal can have a second wavelength different than the first wavelength.

In some implementations, each of the first plurality of optical subcarriers can have a corresponding one of a first plurality of frequencies, and each of the second plurality of optical subcarriers can have a corresponding one of a second plurality of frequencies.

In some implementations, each of the first plurality of frequencies can be different than each of the second plurality of frequencies.

In another aspect, an apparatus includes a first transmitter, a second transmitter, a first receiver, a second receiver, and a selection circuit. The first transmitter includes a first laser operable to provide a first optical signal, and a first modulator operable to provide a first modulated optical signal based on the first optical signal and a first plurality of data stream provided to the first transmitter, the first modulated optical signal including a first plurality of optical subcarriers, such that the first transmitter is operable to supply the first modulated optical signal to a first optical communication path, the first plurality of optical subcarriers being associated with the first plurality of data stream. The second transmitter is operable to receive the plurality of data streams. The second transmitter includes a second laser operable to provide a second optical signal; a second modulator operable to provide a second modulated optical signal based on the second optical signal and the first plurality of data streams, the second modulated optical signal including a second plurality of optical subcarriers, such that the second transmitter is operable to supply the second modulated optical signal to a second optical communication path, the second plurality of optical subcarriers being associated with the first plurality of data streams. The first receiver includes a first polarization beam splitter operable to receive a third modulated optical signal from the second optical communication path, the third modulated optical signal including a third plurality of optical subcarriers associated with a second plurality of data streams, and a first digital signal processor operable to provide an output based on the third plurality of optical subcarriers, the output of the first digital signal processor including the second plurality of data streams. The second receiver includes a second polarization beam splitter operable to receive a fourth modulated optical signal from the first optical communication path, the fourth modulated optical signal including a fourth plurality of optical subcarriers, each of which being associated with the second plurality of data streams, and a second digital signal processor operable to provide an output based on the second plurality of optical subcarriers, the output of the second digital processor including the second plurality of data streams. The selection circuit is coupled to the first digital signal processor and the second digital processor. The selection circuit is configured to selectively supply one of the output of the first digital signal processor and the output of the second digital processor.

In some implementations, the apparatus can include a first wavelength selective switch coupled to the first and second optical communication paths, the first wavelength selective switch being operable to receive the first plurality of optical subcarrier from the first transmitter and supply the first plurality of optical subcarriers to the first optical communication path, and the first wavelength selective switch being operable to receive the third plurality of optical subcarriers from the second optical communication path and provide the third plurality of optical subcarriers to the first receiver; and a second wavelength selective switch coupled to the first and second optical communication paths, the second wavelength selective switch being operable to receive the second plurality of optical subcarrier from the second transmitter and supply the second plurality of optical subcarriers to the second optical communication path, and the second wavelength selective switch being operable to receive the fourth plurality of optical subcarriers from the first optical communication path and provide the fourth plurality of optical subcarriers to the second receiver.

In some implementations, each optical subcarrier of the first plurality of optical subcarriers and each optical subcarrier of the second plurality of optical subcarriers can be a Nyquist subcarrier.

In some implementations, the optical signal provided by the first laser can have a first wavelength and the optical signal provided by the second laser can have a second wavelength different than the first wavelength.

In some implementations, each of the first plurality of optical subcarriers can have a corresponding one of a first plurality of frequencies, and each of the second plurality of optical subcarriers can have a corresponding one of a second plurality of frequencies.

In some implementations, each of the first plurality of frequencies can be different than each of the second plurality of frequencies.

In some implementations, each of the third plurality of optical subcarriers can have a corresponding one of the first plurality of frequencies, and each of the fourth plurality of optical subcarriers can have a corresponding one of the second plurality of frequencies.

Other implementations are directed to systems, devices, and non-transitory, computer-readable media having instructions stored thereon, that when executed by one or more processors, cause the one or more processors to perform operations described herein.

The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.

