Signal to noise ratio management

A vibration sensor system comprising:

• a light pulse generator apparatus configured to provide a plurality of optical pulses, the light pulse generator apparatus comprising:
• a light source configured to generate continuous-wave light;
• a first optical modulator configured to convert the continuous-wave light into the plurality of optical pulses having a predetermined frequency;
• an optical amplifier configured to amplify the plurality of optical pulses;
• an optical circulator having a first port configured to receive the optical pulses and provide the optical pulses to a second port that is optically coupled to an optical fiber, wherein the second port is also configured to receive a backscattering of Rayleigh traces and provide the backscattered Rayleigh traces to a third port that is in optical communication with the sensor;
• a first polarization controller configured to tune the continuous-wave light;
• a second polarization controller configured to tune the plurality of optical pulses;
• and
• a second optical modulator configured to operate substantially in synchronicity with the first optical modulator to enhance an extinction ratio of the optical pulses;
• an optical fiber having a predetermined length and configured to guide the optical pulses;
• and
• a sensor configured to determine a location and frequency of a vibration of the optical fiber at a location along the optical fiber, based on a normalized differential trace that is determined based on a plurality of backscattered Rayleigh traces.

A non-transitory computer storage medium encoded with a computer program, the program comprising instructions that when executed by data processing apparatus cause the data processing apparatus to perform operations comprising:

• controlling a light pulse generator apparatus to transmit a plurality of optical pulses through an optical fiber at a predetermined frequency, the transmitting comprising:
• generating, by a light source of the light pulse generator apparatus, continuous-wave light;
• converting, by a first optical modulator of the light pulse generator apparatus, the continuous-wave light into the plurality of optical pulses having the predetermined frequency;
• amplifying, by an optical amplifier of the light pulse generator apparatus, the plurality of optical pulses;
• directing the optical pulses to a first port of an optical circulator of the light pulse generator apparatus;
• directing, by the optical circulator, the optical pulses to a second port of the optical circulator of the light pulse generator apparatus in optical communication with the optical fiber;
• tuning, by a first polarization controller of the light pulse generator apparatus, the continuous-wave light;
• tuning, by a second polarization controller of the light pulse generator apparatus, the plurality of optical pulses;
• and
• enhancing, by a second optical modulator of the light pulse generator apparatus, configured to operate substantially in synchronicity with the first optical modulator, an extinction ratio of the optical pulses;
• controlling an optical receiver apparatus to determine a vibration frequency at a location along the optical fiber, the controlling comprising:
• digitizing, by the optical receiver apparatus, a plurality of backscattered Rayleigh traces from the optical fiber based on a vibration of the optical fiber at the vibration frequency at the location along the optical fiber;
• determining, by the optical receiver apparatus, a normalized differential trace based on the plurality of backscattered Rayleigh traces;
• determining, by the optical receiver apparatus, based on the normalized differential trace, the location along the optical fiber;
• and
• determining, by the optical receiver apparatus, based on the plurality of backscattered Rayleigh traces, the vibration frequency.