The Study Of Dual-Wavelength Fiber Laser In High Speed Communication Systems

Recently different researches on high speed optical fiber communication system have been devoloped. High repetition rate ultrashort pulse is one solution to improve the transmission speed and capacity of the system. In order to get high repetition rate ultrashort pulse, a dual wavelength fiber laser is used as the initial light source, which will affect pulse characteristics of the achieved ultrashort pulse. Thus, it is significant to study dual-wavelength laser for the applications in high speed communication systems.In this thesis, based on the request of dual wavelength filter in dual wavelength fiber laser, we studied and analyzed the filtering characteristics of fiber gratings, and proposedπ-phase-shifted sampled grating with 75% duty cycle have dual wavelength filtering properties. This kind of sampled grating is applied into the dual wavelength fiber laser structure, and the output of it is studied. The detail as below:(1) Briefly introduced the principle of laser, and discussed how to get dual wavelength fiber laser with dual wavelength filter.(2) Based on the couple mode theory and transfer matrix theory, studied the spectrum properties of the fiber Bragg gratings, phase shifted gratings and sampled gratings.(3) Studied the sampled gratings to achieve dual wavelength filter property. The gratings withπphase shift and periodic structure satisfy the requirement of the dual wavelength filter. The results show thatπ-phase-shifted sampled grating has better property than multi-π-phase-shift grating.(4) Optimized the filtering profile ofπ-phase-shifted sampled grating. The sampled gratings with 75% duty cycle and shorter sampled length have larger side mode suppression ratio.(5) Proposed a dual wavelength fiber laser structure based on 75% duty cycleπ-phase- shifted sampled grating pair. Analyzed the effective length of sampled grating and discussed how to achieve the single longitudinal mode operation. Simulated the dual wavelength single longitudinal mode laser output without gain operation and with EDF gain operation.