The dedicated power communication network is used for the dispatch, operation, and management of power systems, with its key characteristics being high reliability and real-time performance. At present, the typical relay distance of the power communication network is 40 km. In order to further improve its reliability, the number of optical amplifiers can be reduced by increasing the transmission distance between two optical nodes, which reduces the potential fault points as well.

In this work, a high-fidelity digital transmission scheme based on Delta-sigma modulation is proposed. At the transmitter, over-sampling, noise shaping, and two-level quantization are used to map the original high-order modulation signal into Quadrature Phase Shift Keying (QPSK) optical waveform, which improves the tolerance of the link noise and fiber nonlinearity. At the receiver, the link noise is removed by symbol decision, and then the out-of-band quantization noise is suppressed by a low-complexity low-pass filter for the demodulation of the original signal.

In the proof-of-concept experiment, after unrepeated transmission through 160 km standard single-mode fiber and coherent detection, 50 GBaud polarization-division-multiplexed QPSK optical waveform can achieve error-free transmission. At 9-times over-sampling, the recovered Signal-to-Noise Ratio (SNR) of original signal can reach 33.0 dB, which satisfies the 32.0 dB SNR threshold and supports high-fidelity transmission of 1 024-Quadrature Amplitude Modulation (1 024-QAM) signals with a single-wavelength bitrate of 111 Gbit/s.

Experimental results demonstrate that the Delta-sigma modulation scheme can achieve an improvement in SNR through bandwidth broadening, effectively extending transmission reach and performance. This provides a potential solution for the next generation of low-cost and high-reliability dedicated power communication networks.