Vector Sensor for Seismic Application

An optical fiber vector sensor comprising:

• a vector mandrel having a first mandrel part and a second mandrel part, the first and second mandrel parts being spaced-apart from one another by a mandrel gap;
• a mandrel spring placed in the mandrel gap and being in contact with the first and second mandrel parts;
• and
• an optical fiber wound around the first and second mandrel parts to generate a plurality of optical fiber windings which span the mandrel gap.

An optical fiber vector sensor array comprising:

• a plurality of sensor housings, each sensor housing supporting a sensor pod, each sensor pod defining a sensor level;
• a plurality of optical fiber vector sensors supported by each sensor pod;
• a plurality of sensor pod connectors separating the sensor pods in spaced-apart relation to one another;
• a sensor pod clamping system for securing the sensor pods into contact with a borehole wall;
• an optical fiber;
• and wherein:
• each optical fiber vector sensor comprises a vector mandrel having a first mandrel part and a second mandrel part, the first and second mandrel parts being spaced-apart from one another by a mandrel gap;
• a mandrel spring placed in the mandrel gap and being in contact with the first and second mandrel parts;
• a first length of the optical fiber is wound around the first and second mandrel parts to generate a plurality of optical fiber windings which span the mandrel gap;
• and
• a second length of the optical fiber is disposed between each sensor pod.

A method comprising:

• providing an optical fiber;
• providing an optical fiber vector sensor comprising a vector mandrel having a plurality of windings of the optical fiber about the mandrel to produce an optical fiber point sensor;
• providing an optical input signal to the optical fiber such that the optical input signal is provided to the optical fiber point sensor;
• receiving an optical return signal from the optical fiber based on the optical input signal which was provided to the optical fiber point sensor;
• extracting from the optical return signal backscattered light information from the windings of the optical fiber wound around the mandrel;
• extracting from the backscattered light information output signals in a time domain;
• determining phase change information between the optical input signal and the optical output signals based on the backscattered light information contained within the output signals in the time domain;
• extracting from the backscattered light information amplitude information;
• and
• generating an output of amplitudes in the time domain representing events detected by the optical fiber sensor based on the backscattered light information generated by the optical fiber sensor.