“Performance Investigation of NRZ-DQPSK, CSRZ-DQPSK and MDRZ-DQPSK Modulation Techniques for 450 Channel UD-WDM System for Long Haul Communication: ANALYSIS OF MODULATION TECHNIQUES FOR LONG HAUL UD-WDM SYSTEM” (2023) Journal of Scientific & Industrial Research (JSIR), 82(08), pp. 870–884. doi:10.56042/jsir.v82i08.1053.