The influence of actively mode-locked Erbium-Doped Fiber Laser(EDFL) cavity length variation on the noises of an optical pulse train is investigated, in theory and in MATLAB simulation. Using a simple model, the noise characteristics of the output pulse train are studied. The results show that the noises of the output pulse train increase with the increasing of the variation of the cavity length. The theory analysis and the simulation results agree well. This result is very significant for us to improve the reliability and the stability of the actively mode-locked fiber laser.
Different from the traditional way of using piezoelectric (PZT) phase shifter to measure phase difference,a new method is designed to calculate it between signals in the two arms of a homodyne fiber interferometer. A simple homodyne fiber interferometer system is then established to measure the interference photocurrent and the photocurrents from the two fiber arms generated by the signal power on a temperature control plat. The homodyne fiber interferometer system is composed of fiber and sensitive to the variation of temperature. Thus,is necessary to study the temperature characteristics in the phase measurement of homodyne fiber interferometer. The experimental results show that the variation of the phase difference of signals in the two fiber arms is proportional to the variation of temperature.
GAO Bo,TIAN Xiao-jian ,WU Ge,RU Yu-xing,WANG Qing College of Electronic Science and Engineering ,State Key Laboratory of Integrated Optoelectronics,Jilin University ,Changchun 130012,China
In this paper, we study the chaotic dynamics of the mode-locked fiber laser by numerical simulation. The structures of the passively mode-locked fiber laser and the actively mode-locked fiber laser are studied by modeling and analysis. By appropriately adjusting the small signal gain of the optical fiber amplifier, we observe the period-doubling bifurcations and route to chaos in the passively mode-locked fiber laser based on nonlinear polarization rotation effect. Chaos in the actively mode-locked erbium-doped fiber laser is obtained by adjusting the elliptic modulus parameter of the active modulator and the intra-cavity length. Simulation results have theoretical significance for the practical application of chaotic soliton communication.
A new Hash function based on the generalized Henon map is proposed. We have obtained a binary sequence with excellent pseudo-random characteristics through improving the sequence generated by the generalized Henon map, and use it to construct Hash function. First we divide the message into groups, and then carry out the Xor operation between the ASCII value of each group and the binary sequence, the result can be used as the initial values of the next loop. Repeat the procedure until all the groups have been processed, and the final binary sequence is the Hash value. In the scheme, the initial values of the generalized Henon map are used as the secret key and the messages are mapped to Hash values with a designated length. Simulation results show that the proposed scheme has strong diffusion and confusion capability, good collision resistance, large key space, extreme sensitivity to message and secret key,and it is easy to be realized and extended.
