파장-선택성 광섬유 필터의 특성조절 및 극저온 반응에 관한 연구

Abstract

This thesis investigates characteristic control of optical fiber wavelength-selective filters based on a polarization-diversity loop configuration (PDLC) and cryogenic temperature response of long-period fiber-gratings (LPFGs). The flexible tunability of wavelength-spacing or absolute wavelength in multiwavelength filters is very important. First, I have demonstrated absolute wavelength tuning in an optical fiber multiwavelength filter based on a PDLC by controlling electrical currents injected into enameled wires wound on polarization-maintaining fibers (PMFs), that is, adjusting Joule heat generated from current-flowing enameled wires. The proposed filter consists of a four-port polarization beam splitter, a half-wave plate, a quarter-wave plate, and PMFs. The wavelength shifts of spectral dips in the transmission spectra of the fabricated filter were investigated with the variation of the injection current. The absolute wavelength of the filter could be controlled in proportion to the square of the injection current with considerably good linearity, and the wavelength tuning sensitivity was evaluated as ~83.5 nm/A2 with respect to the injection current. And, I have also investigated the cryogenic temperature response of wavelength-selective filters based on LPFGs inscribed on standard photosensitive single-mode fibers without any polymeric coatings. The resonance wavelength of the fabricated LPFG, which was ~1530.778 nm at room temperature (296 K), was monitored under various temperatures ranging from 77 K to 296 K. The temperature sensitivity of the resonance wavelength was measured as ~402.4 pm/K, and the adjusted R-square value of the linear fit of the temperature response curve was evaluated as 0.98144.