Performance Comparison of Offset-16QAM and 16QAM for Nyquist WDM Superchannel With Digital Spectral Shaping

Abstract

We investigate 5-channel polarization division multiplexed (PDM) Nyquist WDM superchannel using offset-16QAM and 16QAM modulation format, under the condition of transmitter-side digital spectral shaping (TS-DSS) technique, respectively. The offset-16QAM scheme can greatly relax the implementation complexity, because the tap number of 35 is sufficient for the required finite impulse response (FIR) filter, compared with 81-tap FIR filter of the 16QAM scheme. About 1.3 dB back-to-back sensitivity improvement is obtained for the offset-16QAM scheme. In particular, the offset-16QAM scheme has better tolerance of DACs' constraints, including the untracked jitter, sampling rate, and resolution. Finally, practical implementation of offset-16QAM based Nyquist WDM superchannel with TS-DSS is evaluated, by taking the phase difference deviation among wavelength channels and phase noise into account. No more than 1.3 dB required-OSNR penalty can be obtained, in case the phase difference is varied from 0 to 360 degree. When the laser with a linewidth of 100 kHz is used, there still exists about 1 dB overall performance improvement, compared with the 16QAM scheme.Index Terms-Nyquist WDM, offset-QAM modulation, finite impulse response filter, digital to analog converter.

Performance Evaluation of a Tactical Data-Link System Based on MSK and 16QAM

“…QAM modulation includes 16-QAM, 64-QAM, 256-QAM, and other modulation methods. There are two main ways to generate QAM modulated signals: the compound phase shift method and the quadrature amplitude modulation method [30]- [32]. The modulation principle diagram of the quadrature amplitude modulation method is shown in Figure 7.…”