基于再生低反射率光纤光栅和饱和吸收体的高温光纤激光传感研究

High-Temperature Fiber Laser Sensing Based on Low-Reflectivity Regenerated Fiber Bragg Gratingand Saturable Absorber

针对再生光纤光栅因反射率低而无法直接用于实际工程中温度测量的问题,提出一种采用光纤激光传感器结合再生低反射率光纤光栅的方法,将再生光栅作为光纤激光器谐振腔的低反镜,采用未抽运的掺铒光纤(EDF)作为饱和吸收体,实现了线宽压缩,多纵模抑制。激光器输出激光的阈值电流为68.9mA。在150mA的电流下,300~800℃温度范围内,激光器输出激光稳定,且输出波长与温度呈良好的线性关系。在升降温测试下,相关系数均为0.99974,平均温度灵敏度为15.41pm/℃,且在700℃下,3h的稳定测试中,激光波长的最大变化量为0.032nm,而强度的最大变化量为0.409dB。实验结果表明,升降温过程中,信噪比均高于50dB,输出激光具有良好的稳定性,且没有跳模现象发生。

Regenerated fiber Bragg grating （RFBG） cannot be directly used in practical engineering for temperature measurement due to its low reflectivity, so a high-temperature fiber laser sensing method based on low-reflectivity RFBG is proposed. RFBG is used as one mirror of the resonant cavity, and a length of unpumped Er-doped fiber （EDF） as saturated absorber is adopted to compress line width and suppress multi-longitudinal mode of laser. The current threshold of fiber laser is 68.9 mA. At 150 mA, the output laser is stable and has a good linear relationship with temperature when temperature varies in the range of 300 to 800 ℃. In the temperature rising and falling test, the correlation coefficient is up to 0. 99974, and the average temperature sensitivity is 15.41 pm/℃. During 3 h of laser stability test at 700 ℃, the maximum variation of the laser wavelength and intensity is 0. 032 nm and 0. 409 dB, respectively. The results show that the signal-to-noise ratio is higher than 50 dB, the output laser is stable, and there is no mode hopping phenomenon in the temperature-rising and temperature-falling process.