Coherent-optical in-line add/drop of PDM tributaries of subcarrier multiplexed signals

We propose an extended coherent optical add/drop multiplexing scheme, in which an individual polarization tributary in a polarization-division multiplexed orthogonal frequency-division multiplexed signal is erased and added by frequency conversion in fiber, which is sequentially inserted in a transmission line. In the scheme, a polarization tributary can be inserted and replaced in a dual polarization spectrally overlapped ultra-dense multiplexed signal. In a proof-of-concept demonstration, we investigate the performance of the proposed optical add/drop multiplexing scheme. A 25-Gb/s quadrature phase-shift keying tributary within a dual-polarization three subcarrier orthogonal frequency division multiplexed signal is erased and added with negligible distortion of the orthogonal polarization tributary and the adjacent subcarriers.