Mode locked fiber lasers and their application in microwave signal generation

Abstract

An investigation of mode-locked fiber ring lasers and their applications in photonic generation of microwave signals is presented in this thesis. Both passive mode locking and active mode locking are investigated. For the passive mode-locking, a fiber laser with figure-eight structure that incorporates a nonlinear amplifying loop mirror as a saturable absorber is proposed and demonstrated. One application of the demonstrated passively mode locked fiber ring laser is to generate high-quality microwave signals. In this thesis, a microwave signal generated by beating the mode-locked longitudinal modes at a photodetector is realized. The results show that the generated microwave signal has low phase noise with high stability. Multiwavelength mode locked laser can find many applications in optical communications. In this thesis, a multiwavelength passively mode-locked fiber ring laser using cascaded fiber Bragg gratings is proposed and demonstrated. It is different from multiwavelength active mode locking in which the round-trip frequencies for all wavelengths must be identical; for passive mode locking, it is demonstrated theoretically and experimentally that the round-trip frequencies are not necessarily identical. A three-wavelength fiber ring laser that is passively mode locked with non-identical round-trip frequencies is demonstrated. (Abstract shortened by UMI.)