The Study On Performance Of Phase-Locked Loop Based On Mode-Locked Fiber Laser

For high-speed optical communication systems, the active mode-locked fiber laser is oneof the most attractive sources for generating transform-limited, ultra-short pulse train with ahigh repetition rate. Especially, the ultrahigh speed active mode-locked of erbium-doped fiberlaser received great attention because it can steadily operate in the1550nm wavelengthregion--the minimum loss region of optical communication, but the main impedance of theapplication is its instability. It is thereof key point how to make it operate stably if active mode-locked fiber laser willbecome available optical source. At present, the scholars at home and abroad are activelydeveloping this research work. They had proposed many practical schemes. The problem ofstability because of its long cavity can be overcome by using a regenerative mode-lockingtechnique, which is an effectual method to improve performance of fiber laser. Thisregenerative Mode-locked fiber laser both can produce high quality pulse train, and excellentresults, simple structure, easy to realize et al. Phase-locked technique has become one of theattractive mode-locked techniques. Whereas high-speed communication systems have a strong desire to gain a signal sourceof high quality. That is to say, it is necessary to gain ultrahigh speed, high purity and highstability optical pulse signal sources. However it is of great difficulty to accomplish ourpurposes using ordinary PLL. It proposed strict performance requirements for PLL, not onlyhigh stability, good tracking performance and lower phase jitter, but also large acquisitionrange and achieving locking fast. However, there are some difficulty in designing excellentPLL, its performance was sometimes dissatisfied. In particular, puzzles was problems of theacquisition performance for input signal and jitter of output signal in PLL designing,furthermore these performances interacted, such PLL designing was faced with newchallenges. This paper mainly found methods and approaches to improve PLL performancebased on existing theory and analysis methods. On the one hand, the super structures ofsub-module circuit were introduced based on basis PLL, embodied on the new phase/frequency detector, loop filter and VCO. On the other hand, it was no longer limited byexisting structures of PLL, gain PLL, nonlinear PLL and current PLL had been studied yet, sostability of the active mode-locked fiber laser were improved .