Review Of All-Fiber Phase And Polarization Modulators

For at least ten years now workers have been contributing techniques for modulating light signals in optical fibers1'2'3'4. These techniques have been of the phase, polarization and frequency variety. However, whereas the phase and polarization modulation techniques can be accomplished in a very efficient manner in what is referred to as the "all-fiber" approach (i.e., an unbroken or unspliced fiber), frequency modulation schemes have not been very efficient (under 2%) using an all-fiber techniques '6. To date, practical frequency modulation is limited to accomplishment in bulk Bragg Cell media external to the fiber. Hence discussion of frequency modulation within an optical fiber is premature at this time. This paper therefore will survey those signal modulation techniques which apply to demonstrated in situ optical fiber modulation techniques, i.e., all-fiber phase and polarization modulation.