TECHNICAL FIELD

The present disclosure relates to data transmission through optic fiber and more specifically to transceivers for the data transmission and reception.

BACKGROUND

Datacenter (DC) traffic, of which >75% stays within the same DC, is growing steadily. This is generating immense need for fast inexpensive power efficient intra-DC optics operating over 10 km. Ethernet speed is envisioned to reach 1.6 Tb/s after 2020 thus spectrally efficient high order modulation is essential to push the capacity per channel or carrier and multiplex fewer channels to achieve aggregate capacity. Various low-cost >10 km demonstrations at >200 Gb/s per channel or color were achieved. In parallel, coherent detection used in metro and long haul links enables high spectral efficiency by giving access to all four degrees of freedom on the optical carrier while providing superior sensitivity relative to direct detection. Some of the existing solutions are regarded as too expensive and power hungry for short reach optics.

SUMMARY

There is provided a transceiver operative to transmit and receive optical signals. The transceiver comprises a laser operative to generate a continuous wavelength. The transceiver comprises a power splitter operative to receive the continuous wavelength from the laser and to split the continuous wavelength into a first portion and a second portion. The transceiver comprises a dual-polarization in-phase and quadrature modulator, DP-IQM, operative to receive the first portion of the continuous wavelength from the power splitter and to modulate the first portion of the continuous wavelength according to a modulation format, thereby producing a first modulated signal. The transceiver comprises a first circulator (C1, C3) operative to receive the first modulated signal from the DP-IQM and to transmit the first modulated signal through a full-duplex fiber. The transceiver comprises a second circulator (C2, C4) operative to receive the second portion of the continuous wavelength, which is the first unmodulated signal, from the power splitter and to transmit the first unmodulated signal through the full-duplex fiber. The first circulator (C1, C3) is further operative to receive a second unmodulated signal from the full-duplex fiber and the second circulator (C2, C4) is further operative to receive a second modulated signal from the full-duplex fiber. The transceiver comprises a first optical polarization controller, PC, operative to receive the second unmodulated signal from the first circulator (C1, C3), and to adjust a polarization state of the second unmodulated signal, thereby producing a polarization state adjusted unmodulated signal. The transceiver comprises a second optical polarization controller operative to receive the second modulated signal from the second circulator (C2, C4) and to adjust the polarization state of the second modulated signal, thereby producing a polarization state adjusted modulated signal. The transceiver comprises a dual-polarization coherent receiver, DP-CRx, operative to receive, through a signal port, the polarization state adjusted modulated signal and, through a local oscillator port, the polarization state adjusted unmodulated signal, the DP-CRx performing coherent detection of modulating information and generating four electrical output signals.

The DP-CRx may comprise a 90° hybrid connected to four balanced photodiodes, the 90° hybrid receiving the polarization state adjusted modulated signal and the polarization state adjusted unmodulated signal through the signal port and the local oscillator port respectively, and the four balanced photodiodes operative to output the four electrical output signals.

The transceiver may further comprise an electrical signal generator generating four electrical input signals for use as input to the DP-IQM, the four electrical input signals providing information symbols and further signals for determining a type of modulation to be performed by DP-IQM to produce the first modulated signal.

The four electrical output signals may correspond to dual polarization in-phase quadrature signals.

The transceiver may further comprise a clock and data recovery, CDR, unit receiving the four electrical output signals, the CDR being operative to recover a clock and to perform decisions about which information symbols are received through the optical signal.

The first and second PC may be controlled by a low speed polarization tracking electrical circuit which feeds a sub-clock from the recovered clock at a rate Rs/N, where Rsis the symbol rate and N is greater than 1000 at 50 Gbaud.

There is provided a system comprising a first transceiver and a second transceiver as described previously. The first transceiver is operative to transmit the first modulated signal, generated from a wavelength λ12, through a first fiber of a fiber pair of the full-duplex fiber; transmit the first unmodulated signal, generated from the wavelength λ12, through a second fiber of the fiber pair of the full-duplex fiber; receive the second unmodulated signal, generated from a wavelength λ21, through the first fiber of the fiber pair of the full-duplex fiber; and receive the second modulated signal, generated from the wavelength λ21, through the second fiber of the fiber pair of the full-duplex fiber. The second transceiver is operative to transmit the first unmodulated signal, generated from the wavelength λ21, through the first fiber of the fiber pair of the full-duplex fiber; transmit the first modulated signal, generated from the wavelength λ21, through the second fiber of the fiber pair of the full-duplex fiber; receive the second modulated signal, generated from the wavelength λ12, through the first fiber of the fiber pair of the full-duplex fiber; and receive the second unmodulated signal, generated from the wavelength λ12, through the second fiber of the fiber pair of the full-duplex fiber.

The transceivers provided herein present improvements to the way transceivers operate.

