Dependence of in-band crosstalk penalty on the signal quality in optical network systems

The in-band crosstalk penalty induced at a different signal quality (optical signal to noise ratio [OSNR], extinction ratio) is investigated. When the OSNR changes from >40 dB to 29 dB, the power penalty at the 25 dB in-band crosstalk increases from 1.5 to 5.5 dB. By choosing an optimal value for the decision level of the receiver, the performance becomes quite tolerant to the varied signal quality as the power penalty induced at a signal having 25 dB of OSNR mixed with 20 dB of crosstalk is less than 2.7 dB.