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

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 C O2 laser 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 nmmε. 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.