Abstract
Abstract In recent year, optical communication becomes more and more important, especially in long distance network communication. The optical sources play an important rule in the system. Fiber optical transmission using a short optical pulse train is a fundamental technology in order to achieve a high-speed and long-distance global network. For ultra-high speed fiber optical communication, the characteristic of ideal transmission source is demanded to be stable (low amplitude jitter), widely tunable wavelength, transform limited, low timing jitter, adjustable pulsewidth, and high extinction ratio. Therefore, a mode-locked erbium-doped fiber lasers (ML-EDFLs) source with high repetition rate and short pulse width is good selection than semiconductor lasers for ultrahigh-speed communication system. Besides, these ML-EDFLs can produce higher output power and lower insertion loss in all fiber system. In recent paper, they mention some methods to solve the problem of stability of the optical mode-locked fiber laser systems, but it needs some more device or high frequency circuit. In this thesis, we use phase locked loop to make the system stable. And the final result improved by PLL.