Nonlinear cross-talk reduction by spectrum shaping in subcarrier signaling WDM networks

Summary form only given. A key issue in developing WDM networks is how to implement the control channel for medium access control and network reconfiguration. The SCM signaling modulates the control channel at a microwave subcarrier and multiplexes with the high-speed payload data at base band, which provides a high-performance and low-cost solution for the signaling implementation in WDM networks. A major performance limitation of SCM signaling comes from various nonlinearities. These nonlinearities generate cross talk proportional to the product of base-band data and the subcarrier in the time domain. In the frequency domain, the cross talk appears as a (two-sided) replica of the base-band spectrum upconverted at the subcarrier frequency because of the spectrum convolution. Because the cross-talk spectrum is an upconverted data spectrum, if we shape the data spectrum to place a null at DC, the cross-talk spectrum will reproduce a null at the subcarrier frequency. Because the subcarrier is a narrow-band signal, the null centered at the subcarrier frequency suppresses the cross-talk penalty significantly. Several line-coding techniques can generate a DC-null spectrum. We focused on Manchester coding because of its simplicity and advantages in clock recovery and burst-mode data receiving.