Distributed Optical Fiber Sensing Technology Based On Chaotic Brillouin Optical Correlation Domain Analysis

At present,distributed optical fiber sensing technology has been extensively researched at home and abroad,and has been widely used in safety monitoring fields such as underground tunnels and aerospace.As to the distributed optical fiber sensing technology's using optical fiber as a sensing element and transmission element,temperature and strain measurements at different locations along the entire fiber length can be achieved.Compared with other sensing technologies,distributed optical fiber sensing based on Brillouin scattering has the advantages of high spatial resolution and long sensing distance.It has a good application prospect and received extensive attention.Chaotic light has the characteristics of like-noise,wide spectrum,and short coherence length,and it is innovatively used as a probe signal of a distributed optical fiber sensing system in this paper.Chaotic Brillouin Optical Correlation Domain Analysis(BOCDA)technology is proposed for the first time.Since the spatial resolution of BOCDA system based on chaotic light depends only on the coherence length of the chaotic light,it can greatly improve the sensing distance of distributed optical fiber sensing under the premise of ensuring high spatial resolution,and thus effectively solving the problem.There is a problem of fuzzy distance in traditional related domain systems.The main research contents of this article include:(1)Theoretical analysis of the chaotic light generation mechanism and the reason why chaotic light contain time delay signature.The time delay signature of chaotic light has a certain influence on the sensing performance of the chaotic BOCDA system,the background noise of chaotic Brillouin gain spectrum will be increased.Therefore,theoretical analysis and experiments have proved that by adjusting the bias current and the feedback intensity of the chaotic semiconductor laser,the time delay signature of the chaotic light can be effectively suppressed within a certain range,and the sensing performance of the chaotic BOCDA system can be optimized.Finally,using the optimized chaotic BOCDA system,a spatial resolution of 7.4 cm was obtained on a 3.2 km sensor fiber,and a temperature coefficient of 1.23 MHz/°C and an uncertainty of ±1.2 MHz were obtained.(2)In the distributed optical fiber sensing experiment based on chaotic BOCDA,it is found that the time delay signature of the chaotic light has a great influence on the sensing performance of the system.Therefore,the Brillouin scattering effect of the optical fiber is further proposed.Suppresses the time delay signature of the chaotic light.The results show that when the average power of the injected chaos light is in the range of 400-1500 mW,the time delay signature of the chaotic light can be significantly suppressed by 0.5 km,2 km,4.5 km,or 6 km lengths of G.652 and G.655 fiber models.At the same time,during the 50 measurements,the suppression of the t time delay signature has a very stable effect.