All-optical regenerative NRZ-to-RZ format conversion using coupled ring-resonator optical waveguide.

This paper proposes a scheme for format conversion from a distorted non-return-to-zero (NRZ) signal to a high-quality return-to-zero (RZ) signal, using the nonlinearity in a coupled ring-resonator optical waveguide (CROW) on a silicon chip. In this method, a distorted NRZ signal is amplified and fed into the CROW together with an RZ pulse train. The CROW performs as a nonlinear step gate for the RZ pulse train, which outputs amplitude-equalized RZ pulses inheriting the information from the NRZ signal. Clearly, the integration of the format conversion and regeneration simplifies the system. Our simulations performed at 10 Gb/s and 40 Gb/s verify the feasibility of our proposal.