高温退火程式对光纤布拉格光栅热重生性能影响研究

光纤布拉格光栅（FBG）是一种广泛应用于光纤通信和传感领域的关键器件,具有灵敏度高、体积小及抗电磁干扰等诸多优点,但长时间工作在高温环境下其光栅特性会逐渐衰退甚至完全擦除,极大地限制了FBG在工业生产、石油电力、航空航天等一些特殊领域的应用。通过高温退火处理有望使FBG在高温擦除后重新生长出能在高温环境下稳定工作的热重生FBG（RFBG）。因此,研究高温退火程式对RFBG性能的影响具有重要意义。基于248 nm准分子激光器,以相位掩模法制作得到反射光谱中心波长为1 548.5 nm、反射率为97.8%、3 dB带宽为0.36 nm的初始FBG,再利用高温管式炉对初始FBG进行高温退火处理,发现FBG在950 ℃时实现热重生,得到反射光谱中心波长为1 546.7 nm、反射率为50.6%、3 dB带宽为0.19 nm的RFBG;进一步研究发现,在950 ℃实现高温热重生后退火程式对RFBG性能有很大影响,对RFBG采用急速冷却、缓慢冷却和自然冷却以及氩气气氛下自然冷却4种方式进行退火处理并与初始光栅进行对比,结果发现采用急速冷却方式处理的RFBG机械性能最佳,其保留了初始光栅约 50%的机械强度,优于缓慢冷却、自然冷却处理仅分别保留初始光栅22.2%和29.9%机械强度的RFBG,并发现在氩气中进行退火处理有利于RFBG机械强度的提升,同样是自然冷却,在氩气气氛中退火得到的RFBG保留了初始光栅43%的机械强度。进一步对采用急速冷却方式处理的RFBG进行热循环、热稳定性等测试。结果表明,RFBG在150~1 050 ℃内三次加热循环结果完全重叠,温度灵敏度为16.30 pm·℃-1,温度灵敏度相关系数R2为0.995 38,且在800 ℃温度下进行热稳定性测试7 h,波长总漂移量仅为0.08 nm,表明所制备的RFBG具备良好的测温性能和稳定性。该研究工作为RFBG高温传感器的实用化和工程化应用提供了一定的理论与实验依据。

Study on the High Temperature Annealing Process of Thermal Regeneration Fiber Bragg Grating

Fiber Bragg Grating (FBG) is a key device widely used in optical fiber communication and sensing. It has many advantages such as high sensitivity, small size and anti-electromagnetic interference. However, it will gradually decline and even be completely erased in a high-temperature environment for a long time, which greatly limits the application of FBG in some special fields such as industrial production, petroleum and electric power, aerospace, etc. Through high-temperature annealing treatment, it is expected that FBG can regenerate thermal regenerated FBG (RFBG), which can work stably in high-temperature environments after high-temperature erasure. Therefore, it is of great significance to study the influence of high-temperature annealing process on RFBG performance. In this paper, based on a 248 nm excimer laser, an initial FBG with a reflection spectrum center wavelength of 1 548.5 nm, a reflectivity of 97.8%, and a 3 dB bandwidth of 0.36 nm is produced by the phase mask method. It is found that FBG achieves thermal regeneration at 950 ℃, and an RFBG with a reflection spectrum center wavelength of 1 546.7 nm, reflectivity of 50.6%, and 3dB bandwidth of 0.19 nm is obtained; further research found that the annealing program after high-temperature thermal regeneration at 950 ℃ has an effect on RFBG The performance has a great impact. The RFBG is annealed by four methods: rapid cooling, slow cooling, natural cooling, and natural cooling in an argon atmosphere, and compared with the initial grating. It is found that the RFBG treated with rapid cooling has the best mechanical performance. It retains about 50% of the mechanical strength of the initial grating, which is better than the slow cooling and natural cooling treatments, which only retain 22.2% and 29.9% of the mechanical strength of the initial grating, respectively. It is found that annealing in argon is beneficial to the mechanical strength of RFBG. The improvement is also natural cooling, and the RFBG annealed in an argon atmosphere retains 43% of the mechanical strength of the initial grating. Further tests on thermal cycling and thermal stability of the RFBG treated with rapid cooling. The results show that the results of the three heating cycles of RFBG at 150~1 050 ℃ completely overlap, the temperature sensitivity is 16.30 pm·℃-1, the temperature sensitivity correlation coefficient R2 is 0.995 38, and the thermal stability test is carried out at 800 ℃ for 7 h, the total wavelength drift amount is only 0.08 nm, indicating that the RFBG prepared in this article has good temperature measurement performance and stability. The research work in this paper provides a certain theoretical and experimental basis for the practical and engineering application of RFBG high-temperature sensors.