Novel FWM-Based Spectral Amplitude Code Label Recognition for Optical Packet-Switched Networks

We propose and demonstrate a novel architecture for four-wave mixing (FWM)-based recognition of spectral amplitude code (SAC) labels in optical packet-switched networks. With a proper code design, a unique FWM idler for each SAC label, referred to as a label identifier (LI), is generated in a nonlinear medium. A serial array of fiber Bragg gratings is then used to reflect the LI wavelengths. Each LI is associated with a unique amount of delay between two optical signals received at two photodiodes (PDs). Label recognition is then achieved by measuring this unique time delay (referred to as the characteristic delay). The main advantages of the proposed method include the following: no serial-to-parallel conversion is required, simple label extraction is achieved, variable-length packets are supported, and the number of PDs used in the label recognition module is reduced. Moreover, the LI wavelengths do not need to exhibit any periodicity or match a particular wavelength grid; this results in a less challenging code design with smaller spectral occupancy for label generation. An experiment is conducted, where two variable-length data packets are transmitted over a 50-km dispersion-compensated span and switched at a forwarding node. The SAC labels are successfully recognized, and we obtain error-free transmission for the switched packets with less than 0.3-dB penalty.