Simplified fiber-optic integrated sensing and IM/DD communication enabled by a frequency-swept laser

Intensity-modulation/direct-detection (IM/DD) optical networks require fiber-optic integrated sensing and communication (F-ISAC) schemes with low hardware complexity and negligible communication penalty. Here, we propose and experimentally demonstrate a simplified F-ISAC scheme enabled by a frequency-swept laser (FSL), which directly generates the periodically swept optical carrier and eliminates the external-modulation-based swept-carrier generation stage. With a single intensity modulator, the system supports 70-Gb/s six-level pulse amplitude modulation (PAM-6) signal transmission and distributed sensing. A sawtooth driving waveform with an inserted transition edge is used to stabilize the FSL output for accurate sensing demodulation. The proposed system retains almost the same forward transmitter and direct-detection receiver as a conventional PAM-based IM/DD link, with only an additional sensing receiver for Rayleigh backscattering detection. Compared with a conventional PAM-based IM/DD system, it increases the optimal launch power by approximately 4 dB and reduces the receiver power penalty by approximately 2 dB at the 7% hard-decision forward-error-correction (HD-FEC) threshold. A spatial resolution of 10 m and a strain sensitivity of 170 pε/√Hz are also achieved.