Study Of Fiber-stabilized Laser For Optical Frequency Dissemination Over Fiber

Nowadays, an atomic clock, as the most accuracy time standard, is widelyused in many fields. The advent of frequency standard based on the atomic transitionmakes frequency the most accurately measured quantity, however, since the atomicclocks are not located in the same place, so in order to accurately compare andevaluate the performance of the atomic clock, high precise frequency disseminate ina long distance is needed, optical frequency dissemination over optical fibers is themost promising alternative. The fiber laser, which has a lot of advantages, is an idealchoice as the light source for frequency disseminationAs the present fiber laser has not yet reached the desired precision for opticalfrequency dissemination, a feedback loop with fiber interferometer is designed tostabilize the fiber laser, the main work in this thesis include:1. For the purpose of developing a ultra-low frequency noise laser, bytheoretical deducting and experimental measuring，some noise in the fiber-stabilizedlaser are evaluated and their expression are presented, besides, the cause of the noiseare discussed.2. The procedure of designing the feedback loop for the fiber laser isintroduced. We utilize a fiber interferometer with unequal arms to translate thefrequency fluctuation of laser to the phase fluctuation of interferometer output andconvert the optical frequency signal to RF signal. Considering the birefringence inthe fiber, the Michelson interferometer with Faraday-rotator mirrors (FRM) isapplied to compensate the change in the polarization state. In order to effectivelydetect beat frequency signal, we use a AOM to shift the frequency to a higher level,so as to eliminate the effect of the noise from the photodetector, besides, a tunablesynthesizer is designed to provide a suitable frequency shift. The interferometer isplaced inside an aluminum box which is designed by us, the aluminum box iscovered by sponge and set onto a passive vibration isolation platform. We alsodesign a PI controller to precisely adjust the feedback signal and make optimumperformance for the fiber-stabilized laser.