FABRICATION AND CHARACTERISTICS OF PHASE-SHIFTED BEAT GRATINGS INDUCED BY CO_2 LASER

摘要

We propose and investigate a phase-shifted long-period fiber grating (LPFG) written by CO_2 laser in twisted single-mode fibers (SMFs). For the beating effect, two peaks of LPFG derived from phase-shift further split into two peaks, respectively. The evolution and characterization of the transmission spectra were investigated. The channel spacing of the phase-shifted LPFGs written in twisted Er-doped fiber could be much narrower than that of which written in twisted normal SMF. Polarization dependent loss of the phase-shifted beat-gratings is less than 0.6 dB. This type of gratings provides potential applications in optical communication systems, such as course wavelength division multiplexing devices.