Experimental Study Of The Complexity Of Erbium-doped Chaotic Fiber Laser

Chaotic laser with the characteristics of the wide bandwidth, good randomness and strong anti-interference is widely used in the secure communication, ranging and sensing and the generation of random numbers and so on. Erbium-doped fiber laser can be used as a high quality light source because of its wide gain spectrum, low loss and high average power, especially it is safe to our eyes. Affected by the cavity length or delayed feedback, the output of chaotic laser always take along with some time–delay signatures. The existence of the time–delay signatures can affect the application of chaotic laser and is closely related to the complexity of the chaotic sequence. For example the time–delay signatures can affect the security of chaotic secure communication and the measuring precision of sensing or ranging, even it will cause rapid deterioration of the randomness of the bit sequence generated by the random number generator. Therefore, the analysis of complexity of the chaotic laser play a significant role in all aspects of its application.In the study, the experiments on the complexity of chaotic laser are carried out based on a erbium-doped fiber ring laser with loss controlling. the research work is mainly summarized as follows:1. The application of chaos light and its research status in erbium-doped fiber lasers were introduced simply. And the development of the complexity in chaotic time series is introduced briefly.2. Several common calculation method of chaotic sequence complexity are expounds in detail, also their advantages and disadvantages are analyzed.3. The different output in a loss-controlling erbium-doped fiber ring laser is experimentally studied, otherwise its complexity is analyzed in detail based on the autocorrelation function and permutation entropy function. The experimental results show that: with the increase of the loss, the permutation entropy complexity increases gradually and the time-delay signature shown in the autocorrelation curves can also be suppressed. When the time-delay signature of chaos is completely hidden, the complexity reaches a maximum, at the same time the output spectrum changes from double wavelength to a single wavelength. In addition, the output of the erbium-doped fiber ring laser with a Mach-Zander interferometer is studied. the study found that under the same attenuation, a higher complexity and output power of chaos can be obtained in this system.4. Using the chaos with a high complexity, a fiber ring cavity ring-down sensor is experimentally researched. We analyzed the autocorrelation coefficient curve of the output signal in the ring-down cavity after some pressure added on the fiber ring. The results show that the total loss in the ring-down cavity can be successfully obtained by the change of the autocorrelation coefficient curve, and then the loss caused by the environment can be estimated. Using this method we can achieve a more convenient way of stress sensing.