Performance evaluation of a DPSK/SCM combined modulation scheme for optical label switching

A combined modulation scheme for optical label switching using DPSK/In-bandSCM has been studied. We present simulations results for the performance of a system with payload data in DPSK modulation at 10 Gb/s and the label modulated on a subcarrier frequency SCM at bitrate of 155 Mb/s. Higher bit rates for the label signal have also been considered and its impact on the payload signal detection has been assessed. Moreover, by means of simulations and mathematical development we show that the frequency for the inband subcarrier that minimizes the crosstalk between the label and the payload is a frequency equal to half the bit rate of the DPSK signal. Furthermore, an optimum value for the modulation index of the subcarrier data label taking into account the induced power penalty over the payload data signal is given. The simulation results show that the proposed scheme is suitable for an OLS network because of its robustness against non-linear impairments in the transmission link and the simplicity of the independent detection of label and payload.