Narrow-bandwidth polarization-scrambling technique using delay-coupled binary phase pulse for carrier-distributed WDM networks

This paper proposes a novel polarization scrambler (PS) for the carrier-distributed wavelength-division multiplexing (WDM) networks based on the ring or the virtual single-star topology. In these networks, the WDM light source for an uplink transmission is located at the center node (CN) and the remote node (RN), or the optical-network unit (ONU) uses a modulator without any light sources. The PS is used to compensate the polarization dependence of the modulators. The proposed PS offers a narrow spectrum bandwidth, due to the use of delayed binary phase pulses coupled with an orthogonal polarization. The narrow bandwidth of the proposed PS is experimentally and analytically confirmed, in comparison to the conventional PS with an orthogonal phase modulation. An eye-pattern calculation for the proposed PS shows that the received eye diagram offers a sufficient margin to meet the transmitter eye-mask definition in IEEE 802.3. Its bit error rate (BER) performance shows that the received-power penalty at the BER of 10^-9 is within 1 dB, even for the worst eye diagram. A transmission experiment is conducted, and the feasibility of the proposed PS is confirmed.