Hybrid transmission of PS-GS4QAM and QPSK data in the form of a PS-16QAM mm-wave signal enabled by optical asymmetrical dual-SSB modulation

The independent optical dual-single-sideband (dual-SSB) signal generation and detection can be achieved by an optical in-phase/quadrature (I/Q) modulator and one single photodiode (PD). The dual-SSB signal is able to carry two different information. After PD detection, the optical dual-SSB signal can be converted into an electrical millimeter -wave (mm -wave) signal. Therefore, the optical dual-SSB signal generation and detection technique can be employed in the radio -over -fiber (RoF) system to achieve higher system spectral efficiency and reduce system architecture complexity. However, the I/Q modulator's nonideal property results in the amplitude imbalance of the optical dual-SSB signal, and then the crosstalk can occur. Moreover, after PD detection, the generated mm -wave signal based on the optical dual-SSB modulation has a relatively low signal-to-noise ratio (SNR), which restricts the system performance. In this paper, we propose an optical asymmetrical dual-SSB signal generation and detection scheme based on the probabilistic shaping (PS) technology, to decrease the influence of the optical dual-SSB signal's amplitude imbalance and to enhance the system performance in the scenario of the limited SNR. The dual-SSB in our scheme is composed of the left sideband (LSB) in probabilistic -shaping geometric -shaping 4-ary quadrature amplitude modulation (PS-GS4QAM) format and the right sideband (RSB) in quadrature phase -shift keying (QPSK) format. The transmitter digital signal processing (DSP) generates a dual-SSB signal to drive the optical I/Q modulator. The I/Q modulator implements an electrical -to -optical conversion and generates an optical dual-SSB signal. After PD detection, the optical dual-SSB signal is converted into a PS-16QAM mm -wave signal. In our simulation, compared with the normal 16QAM scenario, the PS-16QAM scenario exhibits a similar to 1.2 dB receiver sensitivity improvement at the hard -decision forward error correction (HD-FEC) threshold of 3.8 x 10 - 3 . Therefore, in our experiment, based on the PS technology, we design a dual-SSB signal including a 5 Gbaud LSB-PS-GS4QAM at - 15 GHz and a 5 Gbaud RSB-QPSK at 20 GHz. After 5 km standard single -mode fiber (SSMF) transmission and PD detection, the dual-SSB signal is converted into a 5 Gbaud PS-16QAM mm -wave signal at 35 GHz. Then, the generated PS-16QAM signal is sent into a 1.2 m single -input -single -output (SISO) wireless link. In the DSP at the receiver end, the dual-SSB signal can be recovered from the mm -wave signal, and the PS-GS4QAM and QPSK data carried by the dual-SSB signal can be separated. The bit error rates (BERs) of the LSB-PS-GS4QAM and the RSB-QPSK in our experiment can be below the HD-FEC threshold of 3.8 x 10 - 3 . The results demonstrate that our scheme can tolerate the I/Q modulator's nonideal property and performs well in the scenario of a relatively low SNR. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement