Road traffic extraction for unknown anomaly detection using distributed fiber optic sensing
Aspects of the present disclosure describe DFOS systems, methods, and structures that advantageously extract road traffic from DFOS vibration patterns such that anomaly detection is possible. Sensed vibration data is represented accurately as a set of points, where each point is denoted as a tuple with elements indicating a time stamp, a location along a length of a DFOS optical sensing cable, and vibration strength detected at the location at the time. Traffic pattern detection is based on a progressive probabilistic Hough transform (PPHT) that exploits global information from an entire spatial-temporal data snapshot to assess a cause of detected vibrations.
1. A method for operating a distributed fiber optic sensing (DFOS) system including a length of optical sensing fiber in optical communication with a DFOS interrogator and anomaly detector, said method comprising:
providing the DFOS system wherein the optical sensing fiber is deployed proximate to a roadway;
operating the DFOS to obtain normal characteristics of the roadway including road traffic and other infrastructure vibration patterns proximate to the sensing fiber; and
determining, from waterfall images generated during operation of the DFOS, traffic patterns in the waterfall images through the operation of a probabilistic Hough transform (PPHT);
determining salient vibration points along the optical sensing fiber and using those determined salient vibration points in the PPHT operation to determine the traffic patterns; and
determining vibrational anomalies vibration patterns by removing the determined traffic patterns.
2. The method of claim 1 wherein the vibration patterns include sensed data represented in a group of vibration points {p i }, i=1, . . . , N, where each vibrating point is a tuple (t i , x i , v i ), where t i is the time-stamp, x i is the spatial location along the optical sensing fiber, and v i is the strength of vibration.
3. The method of claim 2 wherein a salient vibration point is determined by its vibration strength and is a salient vibration point if its vibration strength is more than 1.5 inter quartile range (IQR) above a third quartile which is represented by:
Salient Point> Q 3 +1.5 ×IQR,
and the IQR of vibrating strength {v i } is a difference between upper and lower quartiles, Q 3 -Q 1 .