Common bias-digital subcarrier multiplexing scheme for integrated sensing and communication in short-reach optical transmission systems

The integration of sensing and communication (ISAC) based on optical fibers has been a key enabling technique to achieve high-speed communication while ubiquitous sensing. In this paper, to ensure the coexistence of communication signal and sensing signal in low-cost optical access networks i.e., intensity modulation/direct detection (IM/DD) based short-reach optical transmission systems, a common bias-digital subcarrier multiplexing (CB-DSCM) scheme is proposed for ISAC signal generation. To assure distributed fiber acoustic sensing (DAS) signal having high spatial resolution and longer detection distance, linear frequency modulation (LFM) pulse compression technique, biased at the null point of the modulator, is used for sensing signal generation at the transmitter, and coherent detection is employed at the receiver. Then, due to the bias voltage at null point, asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) signal is utilized to carry communication signal in the IM/DD system. Therefore, both signals can be simultaneously transmitted using the already deployed modulator, enabling integrated sensing and communication in short-reach optical transmission systems. Experimental results demonstrate that, the proposed CB-DSCM scheme can achieve a net bit rate of 3.01 Gb/s with a bit error rate (BER) as low as 6 × 10^-4 over a 19.8 km fiber-optic transmission link, while it can successfully reconstruct various vibration signals with a spatial resolution of 1 m in short-reach optical transmission systems.