Optical Frequency Comb Generation Using Ultralong SOA and Different Amplification Methods in MZM-based Optical Fiber Loops

Optical frequency combs have been explored in different applications from optical frequency measurements to optical communications. OFCs can be formed using numerous techniques such as optical modulation, laser mode locking and optical fiber recirculating loops. An optical frequency comb generator based on an optical fiber recirculation loop operating with a Mach-Zehnder modulator was experimentally investigated using different types of amplifiers as gain media. The idea is to compare the use of semiconductor optical amplifiers (SOAs) and erbium-doped fiber amplifiers (EDFAs) and their efficiency in aiding or contributing on the generation of spectral lines. The process efficiency associated with nonlinear effects, specially four-wave mixing, is the main advantage of using SOAs over EDFAs. Under the best operational conditions, an optical comb with up to 30 lines and spacing around 20 GHz was obtained by a SOA-based loop, where an ultralong SOA was used for the first time in such an application.