Enhanced inline conversion of fiber Bragg grating spectra based on increased polarization controllability

Inline selection of transmission or reflection spectra of different fiber Bragg gratings using polarization-diversity loop

“…Additional filtering operations such as the selection of only transmission or reflection spectra of two FBGs are also investigated in the proposed filter. Furthermore, filter performances such as the IL, SMSR, and BRR are further improved compared with previous works [15,22].…”

“…This discussion can be quantitatively supported by using the Jones formulation [23], and the filter transmittance t filter can be obtained as follows with respect to linear input polarization with an azimuth angle of θ in by incorporating this matrix formulation, which is easily derived through the consideration of the formulation process of previous works [15,22]: 1 filter q q q q q q q q in 1 2 in…”

“…By adjusting the azimuthal orientation angles of quarter-wave plates (QWPs) contained in the PDLC without reconfiguration of a filter structure [15], the proposed switching filter could select the transmission or reflection spectrum of a single FBG without a IL difference. Recently, enhanced inline conversion was reported using a PDLC-based inline filter showing improved performance in the IL, the side-mode suppression ratio (SMSR), and the band rejection ratio (BRR) by increasing the degree of freedom in controlling states of polarization (SOPs) of light propagating through the polarization-diversity loop [22]. These previous studies were based on the PDLC focused on the inline conversion between transmission and reflection spectra of only a single FBG, but to the best of our knowledge there has been no research on the inline conversion associated with multiple FBGs.…”