Study On Random Distributed Feedback Erbium Fiber Lasers

Randomly distributed feedback fiber laser(RDFFL) is a new kind of fiber laser developed in recent years. Differ from the conventional laser structure, RDFFL without a fixed reflective mirror. It can achieve a stable, spatially incoherent, continuous laser output. This new fiber laser is considered to be an important new light source which can be used for nonlinear optics, optical co mmunications and sensing and other fields. This work studied and implemented several random distributed fee d Back fiber lasers based on erbium-doped fibers:1. An erbium-doped fiber laser based on random distributed fee d Back through Rayleigh scattering in a long-distance(5–30 km) single-mode fiber(SMF) is demonstrated for the first time. Under the pump of a 1480 nm laser diode, typical random laser radiation is achieved with an obvious threshold behavior as a function of pump power. Thanks to the fiber Bragg grating(FBG)-based half-opened cavity design and the efficient gain from the pumped erbium-doped fiber, a low threshold power of 10 m W is achieved, which is approximately two orders lower in magnitude than that of previously reported conventional random fiber lasers amplified through distributed Raman effects. Dual-wavelength lasing operation is also achieved by using two FBGs with different reflection wavelengths to collaborate with the distributed Rayleigh output mirror.2. A tunable erbium-doped fiber(EDF) laser based on random distributed feed-back through backward Rayleigh scattering in a 20-km-long single-mode fiber and a tun-able fiber Fabry–Perot interferometer filter is demonstrated. It has a broad wavelength tuning range up to 40 nm(from 1525 to 1565 nm) with a narrow linewidth of ~0.04 nm.Due to the half-opened laser cavity design and the efficient gain from the pumped EDF, the measured threshold power is only 13 m W, and the pump efficiency is up to 14%.3. A random fiber laser is demonstrated based on a 25-mm-long multi-phase-shifted fiber Bragg grating fabricated in a highly Er/Yb-codoped fiber with the beam-scanning method. By inserting twenty phase errors with random amplitudes along the grating length and pumping it with a 980-nm laser diode, we achieved random laser output with high optical signal-to-noise ratio up to 65 d B. The laser can be operated at either single- or dual-wavelength modes with changeable lasing wavelengths depending on the power of pump laser. The pump threshold is only 28 m W and the output stability is greatly improved by immersing the active fiber in water. It is, to the best of our knowledge, the shortest random fiber laser reported so far, if only the effective part of the fiber is considered.