Internal and External Optical Feedback Effect in Fiber Linear Lasers

In this paper, models of internal and external optical feedback effect in fiber linear lasers have been presented. The effects of optical feedback could be equivalent to the variation of laser cavity loss, and the output expressions of two models are deduced. According to the simulation results, the optical feedback system in fiber linear lasers has the same phase sensitivity as the traditional self-mixing effect in semiconductor lasers. The experimental results show a good agreement with the simulated results. Comparing the output of internal structure with that of external structure, we can conclude that the internal optical feedback system can get higher output gain and stripe depth, which reveals that the internal feedback structure has better sensing characteristics.