Homodyne coherent inter-satellite communications with IM/DD comparable DSP

The rapid development of low earth orbit (LEO) satellite communication networks imposes stringent bandwidth, cost, and power consumption requirements. Conventional intradyne detection (ID) architectures struggle with high Doppler frequency shifts (DFSs), necessitating excessive sampling rates and complex digital signal processing (DSP), resulting in elevated power consumption. This study proposes an inter-satellite polarization division multiplexing self-homodyne detection (PDM-SHD) architecture that compensates for DFSs in the optical domain by co-transmitting a polarization-orthogonal carrier light. The proposed architecture could achieve Nyquist sampling and half-quantization noise, leading to a 53.9% reduction in analog-to-digital converter power consumption under 40 Gbps 16-QAM transmission with a 16 dB signal-to-noise ratio. By demodulating I/Q axis signals independently with real-valued single-input single-output (SISO) processing, it requires only about 15% DSP complexity and achieves intensity-modulation and direct-detection comparable. SISO processing also has the potential to transmit I and Q components from separate devices or satellites, enabling a flexible satellite communication network. The results demonstrate that the proposed architecture achieves detection sensitivities of −40.8 dBm for 80 Gbps quadrature phase-shift keying transmission and −33.0 dBm for 160 Gbps 16-QAM transmission with Nyquist sampling, whereas the ID architecture can hardly work. The proposed architecture effectively balances satellite power constraints with DSP computational demands for high-speed mega-constellation communications.