基于液体热光效应的FBG温度补偿方法

Temperature compensation method for FBG using the thermo-optic effect of liquid

为了降低光纤布拉格光栅（FBG）中心波长对温度变化的敏感度，提出了一种FBG温度补偿新方法。用石英玻璃管对栅区包层被部分腐蚀的FBG进行罐状封装，内部填充具有一定折射率和负热光系数的液体以充当环境包层。利用液体包层热光效应影响FBG中心波长紫移的特性补偿光纤热膨胀和热光效应产生的红移特性，提高了FBG中心波长的温度稳定性，并且在25～55℃的局部温度范围内获得了0．0022nm／℃的温度系数，使FBG中心波长的温度稳定性提高了近5倍，验证了方法的可行性。理论与实验研究表明，通过减小FBG包层厚度或选择具有较大折射率和热光系数的封装液体，可进一步提高封装后的FBG的温度稳定性。这种温度补偿方法简单可行，避免了胶粘材料封装固化过程中的光栅啁啾，拓展了FBG在光纤传感和通信中的功能化应用。

In order to reduce the sensitivity of wavelength-temperature dependence for fiber Bragg grating （FBG） ,we demonstrate an innovative temperature compensation method. Through packaging a thinner silica-cladding FBG with a quartz glass tube, in which the liquid with certain refractive index and negative thermo-optic coefficient, acting as ambient cladding, is filled, the temperature stability of Bragg wavelength shift is enhanced by utilizing the characteristic of Bragg wavelength blue shift,which is caused by the thermo-optic effect of ambient cladding liquid, to compensate the wavelength red shift resulting from the thermal expansion of fiber and its thermo-optic effect. In the temperature range from 25 ℃ to 55 ℃, the coefficient of 0. 002 2 nm/℃ is achieved, which means the temperature insensitivity is enhanced by more than 5 times and the feasibility of this kind of temperature compensation method is verified simultaneously. Further theoretical and experimental researches also demonstrate that the temperature stability of Bragg wavelength can be enhanced through decreasing the silica-cladding thickness or selecting the liquid with larger refractive index and thermo-optic coefficient. Compared with the conventional compensation method,the innovative method is easy to operate and avoids the chirps of FBG in packaging and curing process,which will supply guides for the functional applications of FBG in fiber sensing and communications.