Advantages of Elasticity versus Fixed Data-rate Schemes for Restorable Optical Networks

We investigate link restoration in optical networks carrying multiple data-rates. We compare rate-tunable opto-electronic interfaces (elastic) versus rate-specific (fixed) technologies and show the reconfiguration ability of elastic interfaces strongly reduces the required spare resources. Introduction A manner to increase the network's capacity, maintaining its structure as much as possible, is to replace transmission opto-electronic interfaces (OE) by new devices transporting higher data-rates. For this reason, recent studies have addressed the problem of migration from 10 to 40Gb/s1 or the introduction of 100Gb/s interfaces2, taking into account the different sensitivities of the various datarates to physical impairments. Recent trends in optical technologies such as coherent detection or Orthogonal Frequency Division Multiplexing (OFDM) opened up new horizons such as the possibility of "elastic" OE interfaces able to adapt the data-rate to the amount of data to be transported3. The advantages of this concept are, first of all, the use of a single technology for all OE interfaces of the network, instead of many depending on the desired data-rate to transport ­ e.g. On-Off Keying Non-Return-to-Zero for 10Gb/s, Differential Phase Shift Keying with differential detection for 40Gb/s and soon PolarizationDivision-Multiplexed Quaternary Phase Shift Keying for 100Gb/s channels2. The benefits of elastic technologies for the planning of optical networks with respect to single rate networks have been previously demonstrated4,5.