Delay-Line-Free Multi-Channel Chaotic Correlation Fiber Loop Ring Down Sensing

We propose and demonstrate a delay-line-free multi-channel chaotic correlation fiber loop ring down (MCCCFLRD) sensing based on time division multiplexing (TDM). The factors on the number of multiplexing channels are analyzed, such as the coupling ratio of the fiber coupler, the length of the fiber loop cavity, the length of the signal delay line, and the sampling time (ST) of date process system. The feasibility and stability of the demodulation for the multiplexing chaotic signals with delay-line-free are analyzed theoretically. The results show that the proposed chaotic signal demodulation with delay-line-free can reduce the impact of ST of date process system and achieve the maximum multiplexing number of the multi-channels in the fiber loop system. To verify the feasibility of the chaotic signal demodulation with delay-line-free, the four-channel chaotic correlation fiber loop ring down (CCFLRD) sensing is demonstrated experimentally. The peak finding and signal separation algorithm are used to identify the peak of the correlation coefficient of the multiplexing chaotic signals with delay-line-free. The Levenberg–Marquardt algorithm was used to fit the fiber loop ring down (FLRD) curves. The delay-line-free multi-channel FLRD system can improve the sampling accuracy of effective data points and increase the number of multiplexing channels. The signal demodulation of different channels does not interfere with each other in the external environment. The proposed multi-channel chaotic fiber loop sensing system with delay-line-free has the high multiplexing capacity and accuracy.