Influence Of Residual Stress On Post-fabrication Resonance Wavelength Trimming Of Long-period Fiber Gratings By Heating

摘要

Long-period gratings (LPGs) are written in the fibers un-preheated and preheated. The influence of residual stress on trimming resonance wavelengths by heating the LPGs is investigated comparing the post-heating changes of the transmission characteristics. It becomes evident that the residual stress relaxation shifts resonance wavelengths to shorter wavelengths quickly and the glass structure modification moves them to longer wavelengths slowly. The relaxation rate of the glass structure drops rapidly with the decrease in heating temperature, and the influence of the residual stress relaxation appears more strongly at the early stage of heating at a lower temperature. The trimming wavelength range can be broadened on the short wavelength side by decreasing the heating temperature. We could adjust resonance wavelengths without significant peak loss changes by the residual stress relaxation before writing LPGs, though the trimming range becomes narrow.