Two stage processing distributed fiber optic sensing (DFOS) interrogator for acoustic modulated signals
Distributed fiber optic sensing systems (DFOS) methods, and structures that employ DVS/DAS point sensors and a two-stage processing methodology/structure that advantageously enable point sensors to send sensor data at any time—thereby providing significant processing advantages over the prior art.
1. An optical fiber sensing system comprising:
a length of optical fiber cable;
a fiber sensor interrogator in optical communication with the optical fiber, wherein said interrogator applies interrogation signals to the optical fiber and receives reflected/backscattered signals and generates data indicative of those received signals interrogator system with the length of optical fiber cable;
one or more point sensor elements positioned proximate to the optical fiber, said point sensor elements including a sensor that senses an environmental condition and produces a signal indicative of that sensing;
a modulator that modulates the indicative signal onto an acoustic signal;
wherein the interrogator is configured to provide a vibration detection state and point sensor signal demodulation state;
wherein the vibration detection state detects an abstracted vibration data/signal that is processed from the original, received signals; and
the point sensor demodulation state processes signals from the point sensor elements in a sample-by-sample manner to extract coded information; and
the interrogator uses the abstracted vibration data to determine whether there is a signal from a point sensor or not, and whether to enter demodulation state.
2. The optical fiber sensing system according to claim 1 wherein the point sensor generates an alarm signal for the interrogator to allow the interrogator to get ready for processing before sending modulated data such that the interrogator enters a demodulation mode upon detection of the alarm signal, before modulated data is sent.
3. The optical fiber sensing system according to claim 1 , wherein the point sensor generates and send modulated data whenever it has information to send, without alarm signal, the interrogator detects a vibration from the modulated data; and the interrogator includes a buffer to buffer and delay sample data for the duration of a vibration decision period and once a vibration detected, the interrogator demodulates the sample data buffered in the buffer.