The Noise Analysis On The Optical Pulse Of Actively Mode-locked Fiber Laser

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 producing 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. So it is very valuable to study on it.This paper's main work is based on state National Nature Science Foundation of China fund project (No.60372061)"The study on the real-selfstart and stability of the ultrafast actively mode-locked fiber laser"and Science and Technology Development Planning project of Jilin Province ((2004) technology number (No.1271)) "The study on the mode control and stability of the ultrafast actively mode-locked fiber laser ". In this paper, we study the noise of the actively mode-locked fiber laser theoretically and based on it we study further the low- noise and short-delay compensation technology of the actively mode-locked fiber laser. The main work of this paper including:(1) The application of actively mode-locked fiber laser in optical communication system. Including the development of optical communication techniques, the production of ultra short light pulse, the mold-locked fiber laser's outline as well as the actively mode-locked fiber laser's research progress.(2) Studied the elementary theory of the actively mode-locked fiber laser. Mainly includes the typical structure of actively mode-locked fiber laser the principle of mode-locked, the establishment process of actively mode-locked.(3) We has analyzed the noise problem of the actively mode-locked fiber laser deeply. Including the amplitude noise and the phase noise. We analyzed the manifestation of the short-term instability and the long-term instability and the generation of the two problems. The solved method of the two instabilities. We studied the method deeply of using piezoelectricity ceramics feedback to compensate the cavity change and realizing actively mode-locked fiber laser's steady work. special noise of actively mode-locked fiber laser analyzed.(4) Mathematical noise model of actively mode-locked fiber laser was made. Completed the PZT driver circuit of the cavity compensation of the actively mode-locked fiber laser. This PZT driver has good dynamic response characteristics to the irregular signals, the frequency response range of this circuit is wide, the speed of the response is quick, the consumed power of the driver is small, so it is suit for cavity compensation system of the actively mode-locked fiber laser.(5) Based on original feedback system of my project, verified this system in system respects. Completed the light coherent experiment's theoretical analysis and the system builds. Elaborated with the principle of correlation demodulation, the experimental system structure and we designed the amplified circuit of the photoelectric current. In the experiment, we proposed a new way to measure the initial phase difference of the homodyne fiber interferometer. The experiments shows that this measurement is easy and feasible also may enhance along with the temperature controller precision increase measuring accuracy.The fundamental research and the experiment analyzes of this paper has great meaning for the practical application of the actively mode-locked fiber laser.