Integrated communication and sensing system using a 7.6 MHz linewidth DFB laser with balanced delay self-coherent detection

To effectively suppress the impact of laser phase noise on the extracted phase signal as required for distributed vibration sensing, we propose and experimentally demonstrate, for the first time, to our knowledge, a self-coherent communication and sensing integrated system based on a balanced-delay architecture using a 7.6 MHz linewidth distributed feedback (DFB) laser. In the proposed scheme, identical delays are introduced at the transmitter and receiver to ensure precise optical path matching between the signal and the local oscillator (LO). This configuration effectively suppresses laser phase noise while retaining vibration-induced phase variations, thereby eliminating the need for costly ultra-narrow linewidth lasers. A 55.9 km weakly coupled seven-core fiber system is constructed, where the central core carries the LO and the six outer cores simultaneously transmit 14 Gbaud DP-16QAM signals, achieving multi-channel high-speed communication and distributed vibration sensing integration. The proposed system shares the same coherent transceiver, digital signal processing (DSP) modules, and spatial channels for both communication and sensing, enabling accurate detection of distributed vibration sensing with a frequency range of 900 Hz to 70 kHz. The system yields a phase responsivity of 0.235 rad/V at 10 kHz. This work provides a cost-effective and scalable approach toward highly integrated fiber networks for joint communication and sensing applications.