Asymmetric long period fiber gratings fabricated by use of CO₂laser to carve periodic grooves on the optical fiber

Abstract

An asymmetric long period fiber grating (LPFG) with a large attenuation of −47.39 dB and a low insertion loss of 0.34 dB is fabricated by use of focused CO₂laser beam to carve periodic grooves on one side of the optical fiber. Such periodic grooves and the stretch-induced periodic microbends can effectively enhance the refractive index modulation and increase the average strain sensitivity of the resonant wavelength of the LPFG to −102.89 nm/mε. The resonant wavelength and the peak attenuation of the LPFG can be tuned by ∼ 12 nm and ∼ 20 dB, respectively, by the application of a stretching force.