In-Band Sensing and Communication for Optical Access Networks Using Δφ-OTDR With Simplified Transceivers

An in-band integration strategy is proposed by inserting a sensing probe signal over communication data by modulating the same wavelength channel for next-generation optical access network targeting wavelength-division multiplexing (WDM) point-to-point links. The integration is done by exploring the dc-balanced property of a Manchester-coded signal allowing an effective reduction of low-frequency components to accommodate an in-band Golay-coded lower frequency signal that acts as a sensing probe. The system is demonstrated for 10-Gb/s downstream data over a 20-km fiber with a simple direct-detection receiver in a mobile- or enterprise-fronthaul-based WDM link. Differential-phase-sensitive optical time-domain reflectometry is used to locate external perturbations by using the Golay-coded signal for channel estimation and a coherent receiver at the central office. The presented results show that the downstream data can be successfully retrieved from the integrated signal within a pre-forward error correction bit error rate limit of 10^-3 maintaining enough input optical power budget at the receiver side. Moreover, the backscattered signal is analyzed for accurate detection of two simultaneous events applied over the fiber maintaining a sensing spatial resolution of 2.1 m and a maximum acoustic bandwidth of 381 Hz with a strain sensitivity down to 15 nϵ_pp (peak to peak).