| Title |
Wavelength-Tunable Optical Fiber Flat-Top Multiwavelength Filter |
| Authors |
Do-Kyung Kim ; Yong Wook Lee |
| DOI |
http://dx.doi.org/10.5207/JIEIE.2018.32.2.007 |
| Keywords |
Birefringence Elements ; Multiwavelength Filter ; Flat-Top Pass Band ; Polarization-Diversity Loop Configuration |
| Abstract |
Continuous wavelength tuning of optical multiwavelength filters, which is an essential functionality for flexible signal processing in optical network systems, has been challenging in high order filter structures with two birefringence elements(BEs) or more. Here, we propose a continuously tunable fiber flat-top multiwavelength filter with two BEs using a polarization-diversity loop configuration. The proposed filter consists of a polarization beam splitter, two half-wave plates, two quarter-wave plates, and two polarization-maintaining fiber(PMF) segments. One of the two PMF segments is coupled to the polarization beam splitter with an angle offset of 22.5°. First, the theoretical transmittance of the proposed filter was derived using Jones matrix formulation. Then, theoretical transmission spectra were obtained and displayed at eight orientation angle sets of the four waveplates where phase shifts of 0, π/4, π/2, 3π/4, π, 5π/4, 3π/2, and 7π/4 could be induced in the transmittance function. From theoretical spectral analysis, it was confirmed that a flat-top multiwavelength transmission spectrum could be continuously tuned. This theoretical prediction was also verified by experimental demonstration. |