Abstract Various types of noise can affect the signal quality and degrade the system performance while using ultra-dense wavelength division multiplexing (UD-WDM) systems. Advanced modulation techniques can help to mitigate the effects of signal distortion caused by various noises, improving signal quality and boosting transmission rate. In this paper, we have designed a 400-channel UD-WDM system with a bit rate of 100 Gb/s per channel based on a spectral efficient advanced modulation technique named 8DPSK₂ASK. The performance of the 8DPSK₂ASK modulated UD-WDM system was analyzed at channel spacings of 12. 5 GHz, 25 GHz, 37. 5 GHz, and 50 GHz to investigate the impact of different noise types, including dark current noise, amplified spontaneous emission (ASE) noise, and thermal noise. Performance parameters, including bit error rate (BER), quality factor (Q-factor), eye closure, received crosstalk, and received output power, have been evaluated for all the aforementioned channel spacings by varying the number of channels, transmission distance, and the applied input power. Comparing the impact of thermal noise, ASE noise, and dark current noise on the performance of the 8-DPSK₂-ASK modulated UD-WDM system, the simulation results indicated that thermal noise had the least effect on system performance at a channel spacing of 50 GHz.
Rajeev et al. (2026) studied this question.