基于色散补偿光纤的高速光纤光栅解调方法

本文提出并论证了一种光纤光栅高速解调的新方法, 利用色散补偿光纤的色散效应, 将光纤光栅的波长漂移信息转换成时域信息. 采用脉冲激光器作为光源, 仅需一个光脉冲可获取单根光纤上所有光纤光栅的反射光脉冲, 再根据各个光栅反射回光脉冲的延时变化即可实现波长的解调. 本方法可用于准分布光纤光栅传感网络解调, 系统采用全光纤结构, 无需波长扫描, 大大提高了解调速度. 本文搭建了测试系统进行实验验证, 对3个光纤光栅组成的准分布式传感网络进行了解调, 实验结果表明, 解调出的光纤光栅布喇格波长线性度好, 解调速度最高可达1 MHz, 采样数据取10次平均后解调线性度可达0.9969, 解调误差约为27.8 pm.

A demodulation method of high-speed fiber Bragg grating based on dispersion-compensating fiber

Fiber Bragg grating sensing is one of the most attractive researches in the field of optical fiber sensing. It has made considerable progress due to its advantages in high multiplexing, high precision, small size, light weight, good corrosion resistance and immunity to electromagnetic interference. However, the traditional fiber Bragg grating demodulation technology can hardly achieve high-speed demodulation of multiplexing gratings, which seriously limits its extensive application. A novel high-speed fiber Bragg grating demodulation method is proposed and demonstrated in this paper. Large dispersion will be generated when light going through the long-distance dispersion compensation fiber. Based on the dispersion effect of dispersion compensation fiber, a light beam of different wavelength will generate different time delay, and the wavelength shift of the fiber Bragg grating sensor is then transformed into time domain, and ultimately the fiber Bragg grating wavelength demodulation can be realized by measuring the delay of grating reflective light pulse. The reflective light pulse train of all the cascade fiber Bragg grating sensors can be obtained only through one pulse of light source. This method can be applied in all-fiber structure without wavelength scanning so that it can promote the demodulation speed greatly and can be applied to the demodulation of quasi-distributed fiber Bragg grating sensor network. Disturbing influence of dispersion compensating fibers can be eliminated by introducing the reference grating, and the demodulation process is immune to light intensity disturbance. A test system is set up to demodulate a quasi-distributed sensor network which is made up of three fiber Bragg grating sensors. Results show that the linearity of the demodulated wavelength is good and the demodulation speed can be up to 1 MHz. The demodulation linearity is about 0.9969, and the error is about 27.8 pm after 10 times average. The novel demodulation method proposed in this paper has been tested through theoretical analysis and experimental demonstration, its feasibility to realize high-speed demodulation of fiber grating has been proved, but significant improvements still can be made in the demodulation system. The next step of research work will focus on how to realize decoupling between the location information and the wavelength, to avoid the influence of temperature disturbance on wavelength demodulation, so as to further improve the wavelength resolution and demodulation accuracy.