Abstract

We experimentally study an unequally-spaced optical comb (USOC), which is generated by a unidirectional fiber loop laser operated at low temperatures. The underlying mechanism responsible for USOC formation is explored using both close and open loop measurements. The role played by dispersion is investigated using radio frequency spectrum measurements. By integrating a saturable absorber into the loop, a lasing state is revealed, in which mode locking coexists with the USOC.