The Study Of Multi-wavelength And Narrow-line-width Fiber Laser Based On Polarization Effects

With the rapid development of our modern optical WDM communication system, communication capacity expansion becomes an issue needing taking care of desperately. The most effevtive way is to increase the number of the channels and the direct way to realize multi-channels is exploying many single fiber lasers. However, the increased complexity and cost it brings about when using many single fiber lasers is really upset everyone.Consequently, multi-wavelegnth fiber laser which could afford several source for different channels simultaneously becomes hot spot in recent years. This paper mainly focused on ring cavity multi-wavelengh and narrow-line-width fiber laser based on fiber polarization and birefringent. The following are the detail descriptions of the finished work:1. The main kinds of multi-wavelengh fiber laser and corresponding theory were introduced.2. A tunable multi-wavelength Erbium-doped fiber laser was proposed and analyzed. An analysis of the relation among transmission function T, wavelengthλand power P was done and we got the conclusion that the bigger the output ratio is, the higher the output power, the less fluctuation and less output number are. At the same time, we analyed the reasons caused above results. Up to 17 wavelenghs with 0.35nm wavelength spacing and -7dBm output power was realized when using 10% port as the output port.3. A dual-wavelength Er-doped fiber laser using multi-mode fiber mode beating was proposed. A full investigation against multi-mode fiber incluing the theory and experimental research of its mode beating was carried out. The results shows that mode beating could surpress EDF's uniform gain resulting in multi-wavelengh laser output. Plus, the wavelength spacing becomes smaller with the increasing length of the multi-mode fiber. A stable dual wavelength with 55dB extinction ratio, 53dB Side Mode Suppression Ratio and -2dBm output power is realized through the effects of PHB and polarization-dependent isolator (PDI) and polarization controller (PC).4. A stable narrow Line-width dual-wavelength fiber laser based on nonlinear polarization rotation with a high finesse ring filter was brought up. We studied the theory of the ring filter and simulated transmission spectrum of this ring filter through Matlab tools. Two output spectrums were given before and after we incorporated the high finesse ring filter. We also analyed the differences between the two spectrums and their reasons. The results indicated that two stable wavelengths were generated which both have about 18dB extinction ratio , 16dB side mode suppression ratio (SMSR) and 0.16nm 3dB line-width with the high finesse ring filter.The corresponding central wavelengths were 1565.1nm and 1567.4nm. Plus, less than 2 pm of the wavelengths shift and smaller than 0.4 dB of the optical power fluctuation when the system was operating in a room environment for a period of 40 minutes indicated that the ultra narrow line-width fiber laser is very stable.