Low temperature spectrum of a fiber loop laser

Fiber-based multi-wavelength lasers have a variety of important applications in telecommunication and meteorology. We experimentally study fiber loop laser with an integrated Erbium doped (EDF). The output optical spectrum is measured as function the EDF temperature. find that below critical temperature about exhibits sequence narrow unequally-spaced peaks. An intriguing connection between peaks' wavelengths prime numbers discussed. hypothesis, which attributes comb formation to intermode coupling, explored.