Design and analysis of DPSK and DQPSK modulated UD-WDM system at different data rates for long-haul communication

Advanced modulation techniques play an important role in high-speed data transmission. For this research work, a 400-channel ultra-dense wavelength division multiplexed (UD-WDM) system is designed and simulated using 100 Gb/s and 160 Gb/s per channel transmission data rates along with channel spacing of 0.2 nm. The designed system is based on two highly spectral efficient modulation techniques, namely differential phase-shift keying (DPSK) and differential quadrature phase-shift keying (DQPSK). The performance of both modulation techniques is analyzed using some performance parameters such as received output power, Quality factor (Q-factor), and bit error rate (BER) with varying transmission distances from 100-2000 km. The results obtained from the simulation show that the DQPSK-based UD-WDM system performs better than the DPSK-based UD-WDM system in terms of Q-factor, BER, and received output power for both 100 Gb/s data rate as well as 160 Gb/s data rate because it is more tolerant to linear and nonlinear effects. At 100 Gb/s data rate for the DQPSK modulated system, the minimum BER value of 10-12, the output power of -36 dBm, and the Q-factor of 15 dB are reported. The minimum BER value of 10-8, maximum Q-factor of 12.2 dB, and the output power of -31 dBm are reported for DQPSK modulated system at 160 Gb/s data rate.