Proposal of PPM-RZ-mQAM scheme for suppressing nonlinear phase noise in high spectral ultra-DWDM system

• Published in: Optical and quantum electronics 2022, Vol.54 (1), Article 45
• Main Authors: Abdulzahrah, Abbas Sattar, Hmood, Jassim K.
• Format: Article
• Language: English
• Subjects: Bit error rate; Characterization and Evaluation of Materials; Computer Communication Networks; Dense Wavelength Division Multiplexing; Electrical Engineering; Lasers; Noise; Optical communication; Optical Devices; Optics; Phase noise; Photonics; Physics; Physics and Astronomy; Pulse position modulation; Quadrature amplitude modulation; Signal quality
• ISSN: 0306-8919; 1572-817X
• DOI: 10.1007/s11082-021-03418-5

In this paper, we propose combining a return-to-zero (RZ)-m-ary quadrature amplitude modulation (mQAM) with pulse position modulation (PPM) in ultra-dense wavelength division multiplexing (UDWDM) system for increasing the transmission capacity and reducing nonlinear phase noise(NPN). The proposed transmission scheme has a four-dimensional optical signal space with amplitude, phase, time, and wavelength dimensions, which has better sensitivity than conventional modulation scheme. In our scheme, firstly, each channel is optically modulated by mQAM modulator and subsequently coded with RZ and PPM formats. The envelope of resulting pulses has a sinc-like shape. The performance of the PPM-RZ-mQAM UDWDM system is numerically investigated and compared to the performance of the mQAM UDWDM scheme. The results indicate that both spectral efficiency and signal quality are elevated in the PPM-RZ-4QAM and PPM-RZ-16QAM UDWDM systems. The propagation distance of proposed scheme is lengthened by 55% compared with the 4QAM UDWDM scheme, for bit error rate (BER) of 1 × 10 –3 . Additionally, to achieve BER of 1 × 10 –3 , optical signal-to-noise ratios(OSNRs) are lowered by 2.6 dB and 4 dB, respectively; for PPM-RZ-4QAM and PPM-RZ-16QAM schemes in opposition to conventional systems.