Modified DP-Q and MGF BER

Modified DP-Q and MGF BER

DOI: 10.4018/978-1-4666-6575-0.ch012


The optical return-to-zero differential phase shift keying system is analyzed in this chapter to determine the accuracy of the recently proposed differential phase Q method in estimating the bit error rate. It is found that this method consistently underestimates the bit error rate though it successfully predicts the qualitative behavior of single channel and wavelength division multiplexed systems for back-to-back and point-to-point configurations. A simple modification reduced the underestimation and produced highly accurate estimation.
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Simulation Details

The system model is shown in Figure 1. Each transmitted channel uses 33% duty cycle RZ pulses that are ideally phase modulated by a Mach-Zehnder modulator for RZ-DPSK. The channel bit rate is 40-Gb/s with assumed forward error coding (FEC) overhead of 6.7% yielding a total bit rate of 42.65-Gb/s. For back-to-back configuration, the multiplexed signal is sent directly to the receiver. A second order, super-Gaussian optical bandpass filter is used for WDM demultiplexing. All receivers are ideal with no shot and electrical thermal noise since the dominant noise in long-range systems is accumulated amplified spontaneous emission (ASE). A five-pole, Bessel postdetection electric filter is used with optimal bandwidth of 100 GHz. Three channels centered at 1550, 1551 and 1552 nm are simulated with results obtained from the center channel. Each channel is encoded by pseudo-random bit sequences of length 216-1 bits.

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