복굴절 조합 기반 광섬유 다파장 필터의 스펙트럼 및 출력 편광 특성에 대한 연구

Abstract

An optical fiber multiwavelength filter based on birefringence combination was fabricated by incorporating a polarization-diversity loop structure. It was made of a polarization beam splitter, two half-wave plates (HWPs), and two polarization-maintaining fiber (PMF) segments. One of two PMF segments was chosen to be twice as long as the other, and they were concatenated with a 60° offset between their principal axes. The transmission spectra and output polarization characteristics of the filter were theoretically predicted and experimentally verified. By controlling two HWPs, the filter could be obtained including flat-top and lossy flat-top band modes, and the interleaving operation of the respective spectrum could be also achieved. In particular, it was revealed that the output state of polarization (SOPout) of the filter was a periodical function of wavelength, and the evolution period was different depending on transmission band modes. By controlling input polarization, the specific portion of a pass band could be passed or rejected. It was also theoretically predicted that the fine tuning of the pass band center was possible within a specific wavelength range.