基于啁啾光纤光栅的粮仓测温网络研究

Granary Temperature Measurement Network Based on Chirped FBG

为了解决传统光纤光栅测温系统中单根光纤上带光纤光栅探头数量少、回波光强弱以及复用能力差的问题,设计研究了基于啁啾光纤光栅的测温系统。通过啁啾调制技术提高了回波光的带宽,从而增强了信号的可处理性并大大提高了带探测点位的数量。推导了啁啾调制的光栅周期表达式,给出了调制方法及波长范围。实验采用LPT-102型宽带光源与F-P光纤解调仪等,调制带宽为1 535.0-1 555.0nm,并结合WR-201型温度传感器作标定。对20-60℃范围内每1℃改变进行测试,实验结果显示,传统光纤光栅探头与啁啾光纤光栅探头的测试温度误差相近,都符合设计要求。相比而言,啁啾FBG的测试数据对应的波长偏移具有较为明显的单调线性的特征,即数据稳定性更高,同时,采用啁啾FBG的系统带光纤光栅探头数量明显优于传统光纤光栅测温系统。由此可知,本系统在不增加光纤个数及不降低温度测试精度的基础上,实现了大幅提高带探测点位数量的设计要求。

In conventional optical fiber grating temperature measuring system,it can be loaded into a small number of fibers grating probe.At the same time,the intensity of back waves is relatively weak,and its multiplexing capability is poor.In order to solve these problems,temperature measurement system was designed based on chirped Fiber Bragg Grating.Its purpose is to obtain large-scale,multi-point temperature measurement data.The bandwidth of back waves was improved by chirp modulation techniques,so that available processing power of signal was increased,and the number of the chirped FBG probe in one fiber was greatly increased.Grating period expression was derived in chirp modulation,and modulation method and the wavelength range was provided.In the experiment,LPT-102 broadband light source and the FP optical fiber demodulator were used,and the modulation bandwidth of the system was from 1 535.0to 1 555.0nm.It used the WR-201 type temperature sensor as calibrated detector.Experimental results show that when the temperature changed by 1 ℃ from 20-60 ℃,the test temperature error would be closed with traditional Fiber Bragg Grating probe and chirped Fiber Bragg Grating probe,and they both meet the design requirements.In contrast,the wavelength shift data of chirped FBG was more monotone linear than the characteristic FBG,so its data was more stable.Meanwhile,in one fiber,the number of probes in the chirped FBG system was greatly more than the Uniform FBG system.In the original FBG system,without increasing the number of optical fiber or reduced the temperature measurement accuracy,design requirements for increase with the number of probe points in the system was achieved.