In this paper, we demonstrate a high-sensitivity and real-time heterodyne coherent optical transceiver for intraplane satellite communication, without digital-to-analog converter (DAC) devices and an optical phase lock loop (OPLL). Based on the scheme, a real-time sensitivity of -49 dBm is achieved at 5 Gbps QPSK. Because DAC is not needed at the transmitter, as well as OPLL at the receiver, this reduces the system cost. Furthermore, the least required Rx ADC bit-width is also discussed. Through theoretical analysis and experimental results, our cost-effective transceiver satisfies the scenario and could be a promising component for future application.

A continuous-wave (CW) single-longitudinal-mode (SLM) Raman laser at 1240 nm with power of up to 20.6 W was demonstrated in a free-running diamond Raman oscillator without any axial-mode selection elements. The SLM operation was achieved due to the spatial-hole-burning free nature of Raman gain and was maintained at the highest available pump power by suppressing the parasitic stimulated Brillouin scattering (SBS). A folded-cavity design was employed for reducing the perturbing effect of resonances at the pump frequency. At a pump power of 69 W, the maximum Stokes output reached 20.6 W, corresponding to a 30% optical-to-optical conversion efficiency from 1064 to 1240 nm. The result shows that parasitic SBS is the main physical process disturbing the SLM operation of Raman oscillator at higher power. In addition, for the first time, the spectral linewidth of a CW SLM diamond Raman laser was resolved using the long-delayed self-heterodyne interferometric method, which is 105 kHz at 20 W.

A spectrally sliced heterodyne coherent receiver (SHCR) employing four balanced photodetectors and analog-to-digital converters with half of the signal bandwidth is proposed to complete the signal reception and field recovery. We first numerically characterize the performance of SHCR compared with an intradyne coherent receiver and then validate the principle of the SHCR in a proof-of-concept single-polarization experiment. A 60 GBaud 16-quadrature amplitude modulation transmission is experimentally demonstrated over 80 km standard single-mode fiber with a bit-error-rate of 8.5×10-4 below the 7% hard-decision forward error correction threshold of 3.8×10-3. The SHCR offers a low-cost, hybrid-free, and channel-skew-tolerant candidate for data center interconnects.