プラスチック光ファイバ・ブラッグ・グレーティングの歪感度の光波長依存性を解明した石川（M1）の論文が Japanese Journal of Applied Physics に掲載されました。
R. Ishikawa, H. Lee, A. Lacraz, A. Theodosiou, K. Kalli, Y. Mizuno, and K. Nakamura, “Strain dependence of perfluorinated polymer optical fiber Bragg grating measured at different wavelengths,” Jpn. J. Appl. Phys., vol. 57, no. 3, 038002 (2018).
We measure the strain dependence of multiple Bragg wavelengths (corresponding to different diffraction orders) of a fiber Bragg grating (FBG) inscribed in a perfluorinated graded-index polymer optical fiber (PFGI-POF) in the wavelength range up to 1550 nm. Based on this result, we show that the fractional sensitivity, which has been conventionally used as a wavelength-independent index for fair comparison of the FBG performance measured at different wavelengths, is dependent on wavelength in this range. The reason of this behavior seems to originate from the non-negligible wavelength dependence of refractive index and its strain-dependence coefficient. Using the wavelength dependence of the refractive index already reported for bulk, we deduce the wavelength dependence of the strain coefficient of the refractive index. This information will be a useful archive in implementing PFGI-POF-based strain sensors based not only on FBGs but also on Brillouin scattering in future.