| Nowadays, the information has become the world-wide sharing resources and influence humanity's progress, the people acquire the way of the knowledge and the experience is changing largely because of the information revolution. Along with the development of correspondence, the high communication system capacity is requiring increasingly. A stable optical pulse source with a high repetition rate is very important for realizing future ultra-high speed optical communication. The actively mode-locked erbium doped fiber laser is very attractive among those potential sources which can generate broadband tunable near transform-limited pulse with high repetition rate and has been used as the ideal optical transmitter and all optical clock source in the future long-distance communication systems. But the stability technique problem of the actively mode-locked fiber laser is not solved. So there is a distance of the practical application of actively mode-locked fiber laser. The prerequisite of actively mode-locked fiber laser stable work is that the modulation signal frequency must be the integral multiple to the cavity resonance frequency. Because the cavity of the actively mode-locked fiber laser is long (usually several dozens to several hundred meters), also in the cavity has the long fiber. Fiber lasers are very sensitive to environmental perturbations such as temperature fluctuations and mechanical vibrations due to their relatively long cavity length when the external environment changing . The cavity drifting produceing the phase noise and amplitude noise, this can cause the output pulse unstablely. When this is serious, the fiber laser will lost the mode-lock. For the modulation frequency and the cavity are very difficult to maintain matching, so it is difficult to guarantee the long time steady work of actively mode-locked fiber laser. It is a problem which must be solved that how to keep the actively mode-locked fiber laser working stably for long time. |
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