In this article the performance of grey-coded advanced optical modulation formats is evaluated on a single-channel high-speed long-haul optical communication link and are compared to the respective differential-coded ...
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In this article the performance of grey-coded advanced optical modulation formats is evaluated on a single-channel high-speed long-haul optical communication link and are compared to the respective differential-codedmodulationformats. Polarisation division multiplexed optical in-phase quadrature modulator (IQM) structure and homodyne detection scheme are used to realise 100Gbps quadrature phase-shift keying (QPSK), 120Gbps 16-ary quadrature amplitude modulation (16-QAM), 360Gbps 32-QAM and 480Gbps 64-QAM modulationformats. advanced digital signal processing unit with various pre-processing and recovery stages such as direct current blocking, normalisation, low-pass Bessel filter, resampling, quadrature imbalance compensation, chromatic dispersion compensation, non-linear compensation, timing recovery, adaptive equalisation, down-sampling, frequency offset estimation, and carrier phase estimation is used at the receiving end to compensate for signal impairments during propagation. Maximum transmission distances of 7200, 1050, 560, and 360km have been achieved at an acceptable bit error rate for QPSK, 16-QAM, 32-QAM, and 64-QAM, respectively. The grey-coded systems outperformed the differential-coded systems regarding optical signal-to-noise ratio requirement, receiver sensitivity, and transmission distance.
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