高温热重生光纤布拉格光栅制备及其性能研究

Study on Preparation and Properties of High Temperature Regenerated Fiber Bragg Gratings

通过高温(850~950℃)退火方法使光纤布拉格光栅在高温擦除后重新生长形成热重生光纤光栅,其能够在大于1 000℃以上的高温环境中稳定工作,但经高温退火处理后的热重生光纤光栅机械强度较一般光纤布拉格光栅显著下降.本文通过采用单模石英光纤进行实验,对光纤光栅的轴向应力和光纤光栅中石英分子组分的变化进行研究分析.结果表明,经过高温热退火后的热重生光纤光栅与未退火的光纤布拉格光栅相比,纤芯处压应力减少了80 MPa,远离纤芯的包层处拉伸应力由22 MPa逐渐减小;同时,随着热退火气氛中氧含量的增加,退火后生成的热重生光纤光栅SiO2逐渐增加,占比从52.99%上升至69.92%.虽然SiO2具有较高的密度,其机械强度大于Si2O3,但热退火后的热重生光纤光栅脆性仍增大,故推论:组分变化对热重生光纤光栅脆性增大无明显影响,脆性增大主要原因为高温导致的应力松弛.本文研究为提高热重生光纤光栅的机械性能,解决其脆性问题提供了可靠的理论与实验依据.

By annealing at high temperature(850~950℃),the fiber Bragg grating can be erased at high temperature and grow again to form a regenerated fiber Bragg grating,which can work stably in a high temperature environment of more than 1 000 ℃. However,the mechanical strength of the regenerated fiber Bragg grating after annealing at high temperature is significantly lower than that of common fiber Bragg gratings. In this paper, the axial stress of fiber Bragg grating and the change of quartz molecular components in fiber Bragg grating are studied and analyzed by single mode quartz fiber experiment. The results show that compared with the unannealed fiber Bragg grating,the compressive stress at the fiber core decreases by 80 MPa,and the tensile stress at the cladding far away from the fiber core gradually decreases by 22 MPa. At the same time,with the increase of oxygen content in the atmosphere of hot annealing,the regenerated fiber grating SiO2 generated after annealing gradually increased,and the proportion increased from 52.99% to 69.92%. Although SiO2 has a high density and its mechanical strength is greater than Si2O3,the brittleness of the regenerated fiber grating after hot annealing still increases. Therefore,it is inferred that the change of components has no significant effect on the increase of brittleness of regenerated fiber Bragg grating,and the main reason for the increase of brittleness is the stress relaxation caused by high temperature. This paper provides a reliable theoretical and experimental basis for improving the mechanical properties and solving the brittleness problem of thermal regenerated fiber Braggg ratings.