Inline Conversion Between Transmission and Reflection Spectra of Fiber Bragg Grating Using Polarization-Diversity Loop Structure

By incorporating a polarization-diversity loop structure, we have demonstrated an inline conversion between transmission and reflection spectra of a fiber Bragg grating (FBG) without reconfiguration of the filter structure containing the FBG. The proposed apparatus consists of a polarization beam splitter, an FBG, and two quarter-wave plates (QWPs). Without requiring rearrangement of input/output ports or additional optical switches, the spectral switching operation of the FBG was carried out through proper adjustment of the QWPs contained in the proposed filter.