Routing Code and Spectrum Assignment (RCSA) in Elastic Optical Networks

Elastic optical networks (EONs) are an attractive solution for backbones due to the offered potential flexibility and spectral efficiency. In EONs, an optical connection is allocated by solving the problem of routing and spectrum assignment (RSA). Based on the RSA output, a portion of spectrum-whose width depends on transmission parameters (e.g., bit rate and modulation format)-is assigned to an optical connection along a computed route. New emerging techniques for distance adaptation, that exploit variable code, are under investigation. In this case, the code rate (or redundancy) is tuned depending on the required optical reach. In EONs, transponders supporting distance adaptation permit to trade off between optical reach and required bandwidth (e.g., through the adaptation of modulation format), so that the spectrum occupied by a connection can be minimized while guaranteeing the required optical reach. This paper presents the concept of code selection in RSA for EONs, by proposing a routing, code, and spectrum assignment (RCSA) for dynamic set up. According to RCSA, a path, a code, and a portion of spectrum are selected for a connection request while guaranteeing quality of transmission. RCSA considers transmission impairments (e.g., amplified spontaneous emission) and filtering effects.