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在用化学镀结合电镀方法对光纤布拉格光栅(FBG)进行金属化保护的过程中产生的应力直接影响到金属化FBG(MFBG)的传感精度。为此,基于应力产生的机制,对应力作用下化学镀和电镀过程中FBG的谐振谱变化进行了分析。实验发现化学镀后FBG谐振谱出现了较大的谱带展宽与峰值损耗减少。对化学镀产生的应力进行了理论及数值分析,结果显示热应力在FBG内部产生了扰动。通过延长化学镀后冷却时间的方法减少热应力,并通过充分搅拌化学镀液的方法减少应力的不均匀性,优化后的化学镀应力对FBG的影响很小。其后的电镀实验显示电镀过程是产生应力的主要原因。通过稳定较高的电镀温度、充分搅拌及采用双电极的方法达到了尽可能减少电镀过程应力对FBG频谱影响的目的。对优化化学镀和电镀条件后制成的MFBG进行温度传感实验表明,其回程误差小于已有的报道。
The stress generated during metallization of fiber Bragg gratings (FBGs) by electroless plating combined with electroplating directly affects the sensing accuracy of metallized FBGs (MFBGs). Therefore, based on the mechanism of stress generation, the resonance spectra of FBG during electroless plating and electroplating under stress are analyzed. The experimental results show that there is a large band broadening and peak loss reduction in the FBG resonance spectrum after electroless plating. The theoretical and numerical analysis of the stress caused by electroless plating showed that the thermal stress generated perturbations inside the FBG. By extending the cooling time after electroless plating to reduce thermal stress, and by fully mixing the electroless plating solution to reduce the stress non-uniformity, the optimized electroless plating stress has little effect on the FBG. Subsequent plating experiments showed that the plating process was the main cause of stress. By stabilizing the higher plating temperature, mixing and using two-electrode method to achieve the goal of minimizing the stress of the plating process on the FBG spectrum. The experiments of temperature sensing on the MFBG made by optimizing electroless plating and electroplating conditions show that the return error is smaller than that reported before.