On the coexistence of distributed fiber optic sensing and IM/DD transmission via digital subcarrier multiplexing

The technology of integrated sensing and communication over fiber (ISACoF) has emerged as a key enabler for achieving high-speed communication alongside ubiquitous sensing capabilities in fiber-based short-reach networks. In this paper, we propose a digital subcarrier multiplexing (DSCM)-based ISACoF scheme for spectrally integrating the digital linear frequency-modulated (LFM) sensing signal into intensity modulation and direct detection (IM/DD) systems, enabling simultaneous sensing and communication through a shared IM transmitter. By jointly optimizing the bias voltage of the intensity modulator and the communication-to-sensing power ratio (CSPR), proof-of-concept experiments are carried out to evaluate the feasibility of the proposed DSCM-based ISACoF scheme. Experimental results demonstrate that the proposed DSCM-based ISACoF scheme is capable of transmitting a 16-Gbit/s 16-quadrature amplitude modulation (QAM)-DSCM signal over a 10-km IM/DD link. Simultaneously, distributed acoustic sensing with a sensitivity of 54 pε/Hz and a spatial resolution of 10 m can be achieved.