Development of Mass Production Technique of Optical Fiber Bragg Grating by All Solid-State Near-UV Laser

Abstract

We have developed a new laser that emits radiation at a wavelength of 335.5 nm for the fabrication fi ber Bragg gratings (FBGs) without the need to remove the polymer jackets which are covering fibers. Subsequently, we have investigated the effect of Ge concentration in the core using the laser. It was found that a Ge concentration of more than 6 7 mol% in the core is needed for practical writing of FBG. In spite of use of the laser, the polymer jackets were thermally damaged by cw irradiation. The intermittent irradiation was thus necessary, and we have clarifi ed the irradiation conditions for writing FBGs without removing the polymer jacket. The refl ectivity of FBG increased with the length of FBG. We estimated that a 16 19-mm long FBG has enough refl ectivity to fabricate a distortion monitoring device that can be widely used in the civil and architectural fi elds.