Dian Chen

Phase-detection distributed fiber-optic vibration sensor without fading-noise based on time-gated digital OFDR

For a distributed fiber-optic vibration sensor (DFVS), the vibration signal extracted from the phase of backscattering has a linear response to the applied vibration, and is more attractive than that from the intensity term. However, the large phase noise at a random weak-fading-point seriously limits the sensors credibility. In this paper, a novel phase-detection DFVS is developed, which effectively eliminates the weak-fading-point. The relationship between phase noise and the intensity of backscattering is analyzed, and the inner-pulse frequency-division method and rotated-vector-sum method are introduced to effectively suppress phase noise. In experiments, two simultaneous vibrations along the 35-kilometer-long fiber are clearly detected by phase detection with the signal-to-noise ratio (SNR) over 26 dB. The spatial resolution approaches 5 m and the vibration response bandwidth is 1.25 kHz.

Fading-noise-free Distributed Fiber-optic Vibration Sensor Based on Time-gated Digital OFDR

A novel distributed fiber-optic vibration sensor based on phase detection method from TGD-OFDR is presented, where frequency shift method and weighted average method are utilized to eliminate phase demodulation errors caused by fading noise.

Fiber-optic distributed acoustic sensors (DAS) and applications in railway perimeter security

The paper introduces the DAS system based on advanced phase-sensitive optical time domain reflectometry (φ-OTDR) with fading noise suppressed. Besides, the DAS system based on time-gated digital optical frequency domain reflectometry (TGD-OFDR) and its improved systems are introduced. The application of DAS in railway perimeter security is introduced at the end of the paper.

Distributed fiber-optic vibration sensor with enhanced response bandwidth and high signal-to-noise ratio

A novel distributed fiber-optic vibration sensor (DVS) is proposed based on multi-pulse time-gated digital optical frequency domain reflectometry (TGD-OFDR), which can solve both the trade-off between the maximum measurable distance and the spatial resolution, and the one between the measurement distance and the vibration response bandwidth. A 21-kHz vibration is detected experimentally over 10-kilometer-long fiber, with a signal-to-noise ratio approaching 25 dB and a spatial resolution of 10 m.

Improving Spatial Resolution of Time-gated Digital Optical Frequency Domain Reflectometry using Diode Laser Sources

To improve the spatial resolution of time-gated-digital OFDR, a distributed feedback (DFB) diode laser with current tuning is used to provide a large laser frequency tuning range. The driving current of DFB laser diode is pre-distorted to commentate the tuning nonlinearity of laser, and 10-cm spatial resolution over 74-km fiber link is realized.