A Survey on OFDM-Based Elastic Core Optical Networking <s> 3) Data-Rate Elastic Optical Network <s> We propose a network model based on format-versatile transceiver for data-rate tunability. We estimate each format's resistance to degradations and dimension a backbone network accordingly, yielding 20% savings on resources compared to single-rate networks. <s> BIB001 </s> A Survey on OFDM-Based Elastic Core Optical Networking <s> 3) Data-Rate Elastic Optical Network <s> With the growth of traffic volume and the emergence of various new applications, future telecom networks are expected to be increasingly heterogeneous with respect to applications supported and underlying technologies employed. To address this heterogeneity, it may be most cost effective to set up different lightpaths at different bit rates in such a backbone telecom mesh network employing optical wavelength-division multiplexing. This approach can be cost effective because low-bit-rate services will need less grooming (i.e., less multiplexing with other low-bit-rate services onto high-capacity wavelengths), while a high-bit-rate service can be accommodated directly on a wavelength itself. Optical networks with mixed line rates (MLRs), e.g., 10/40/100 Gb/s over different wavelength channels, are a new networking paradigm. The unregenerated reach of a lightpath depends on its line rate. So, the assignment of a line rate to a lightpath is a tradeoff between its capacity and transparent reach. Thus, based on their signal-quality constraints (threshold bit error rate), intelligent assignment of line rates to lightpaths can minimize the need for signal regeneration. This constraint on the transparent reach based on threshold signal quality can be relaxed by employing more advanced modulation formats, but with more investment. We propose a design method for MLR optical networks with transceivers employing different modulation formats. Our results demonstrate the tradeoff between a transceiver's cost and its optical reach in overall network design. <s> BIB002
In BIB001 , a data-rate-elastic optical network architecture was proposed, to use a single type of novel rate-tunable transponder which can operate at various data rates to handle all types of traffic. This elastic optical network provides similar solutions as WDM with mixed line rate (MLR) BIB002 , but with increased flexibility, as it simplifies the design of the network and allows sharing of resources for different data-rate services. This elastic optical network architecture can employ multicarrier and single-carrier multiplexing technologies, while it differs from SLICE and FWDM by using a fixed-grid spectrum allocation. Even though this implies full compatibility with the current WDM network architecture, it fails to achieve flexible spectrum accommodation and high spectrum efficiency. Fig.  11 shows the differences in scopes between the three proposed architectures. In the following section, we will mainly address the OFDM-based elastic optical network architecture, as the subwavelength multiplexing and flexible spectrum allocation features of O-OFDM technology provide immense flexibility to support heterogeneous traffic demands and offer high spectrum efficiency. However, the key enabling technologies can be shared with multi-carrier (OFDM) and singlecarrier modulation based elastic optical network, such as data-rate/bandwidth-variable transponder, bandwidth-variable WXC, routing and spectrum allocation schemes, etc. (which will be discussed in detail in Section IV-C and IV-D).