Real-time fiber optic interferometry controller
A modular fiber optic interferometry control system and method for extracting information from superimposed waves is disclosed. The system comprises a first module for converting a radio frequency input to a multiplexed binary data stream, a second module for correlating a pseudo random number (PRN) reference with a received PRN code modulated backscattered signal, and a third module comprising control logic. In some embodiments the system further comprises one or more of a fourth module for generating a power stream, a fifth module for event interrogation, and a sixth module for noise reduction.
1. A modular fiber optic interferometry control system to extract information from superimposed waves, the system comprising:
a first module comprising a radio frequency (RF) input comprising superimposed waves from at least one photo diode,
a first amplifier connected to a first programmable attenuator, wherein the first programmable attenuator is connected to a first mixer, operable to condition the RF input;
a second amplifier connected to a second programmable attenuator, wherein the second programmable attenuator is connected to a second mixer, operable to condition the RF input;
a local RF oscillator coupled to an RF splitter, wherein the RF splitter generates two outputs, wherein a first output of the two outputs is connected to the first mixer, and a second output of the two outputs is connected to the second mixer,
an analog to digital convertor (ADC) connected to an output of the first mixer and an output of the second mixer, wherein the outputs represent a pseudo random number (PRN) code modulated backscattered signal received from a fiber under test, and where the ADC output is a multiplexed binary data stream;
a second module comprising
at least one shift register correlator to correlate a PRN reference with the received PRN code modulated backscattered signal,
a processor to packetize and control communication;
a third module comprising control logic for the modular fiber interferometry controller, wherein the control logic includes a computer readable memory having executable instructions stored thereon, wherein the instructions, when executed by one or more processors, cause the one or more processors to perform operations comprising at least one of data logging, communications, memory management, and light source management.
2. The system of claim 1 , further comprising a fourth module for generating a power stream wherein the one or more processors perform operations comprising at least one of wild point smoothing, circle correction, vector determination, merge change in phase data, and merge power data.
3. The system of claim 1 , further comprising a module for event interrogation wherein the one or more processors perform operations comprising at least one of bandpass filtering and fast Fourier transform to output at least one of an audio stream and a data stream.
4. The system of claim 1 , further comprising a module for noise reduction wherein the one or more processors perform operations comprising at least one of Kalman filtering, Bayesian inferencing, Bayesian updating, Markovian prediction, bandpass filtering, Butterworth filtering, adaptive filtering, background subtraction, and model fitting.
5. The system of claim 1 , wherein the local RF oscillator generates a signal frequency equal to or different than the received signal to form an intermediate frequency signal.
6. The system of claim 1 , wherein the at least one shift register correlator determines a time delay of the PRN code modulated backscattered signal.
7. The system of claim 1 , wherein the third module control logic is configured to perform management operations for all modules connected to the modular fiber optic interferometry controller.
8. The system of claim 1 , wherein the PRN code modulated backscattered signals are generated from at least one of acoustic pressure waves, electromagnetic fields, mechanical strain or pressure, and thermal strain or pressure.
9. The system of claim 1 , wherein the fiber under test comprises at least one of a single-mode type, multimode type, and polarization preserving type fiber optic cable.
10. The system of claim 1 , wherein the fiber under test has a length L and the light source is a laser having the capability to generate a signal with sufficient stability to retain coherency in propagation along the fiber under test for a distance at least equal to two times the length L.
11. The system of claim 1 , wherein the fiber under test has a coating thereon made of a thermoplastic material having the combined characteristics of a low Young's modulus and a Poisson's ratio below that of natural rubber, wherein the coating enhances the longitudinal component of strain variation derived from an acoustic wave signal.
12. The system of claim 1 , wherein all signal splitters and signal couplers use signal attenuators on all unused ports.
13. The system of claim 12 , wherein the signal attenuator is a mandrel.
14. The system of claim 1 , wherein the light source is a laser.
15. The system of claim 14 , wherein the laser is one of continuous wave (CW) and pulse modulated CW.
16. The system of claim 1 , wherein the system is enclosed by a material conducive for vibration attenuation.
17. A method for extracting information from superimposed waves with a modular fiber optic interferometry control system, the method comprising:
using a first module configured to:
receive a radio frequency (RF) input comprising superimposed waves,
using a first amplifier connected to a first programmable attenuator, wherein the first programmable attenuator is connected to a first mixer, operable to condition the RF input;
using a second amplifier connected to a second programmable attenuator, wherein the second programmable attenuator is connected to a second mixer, operable to condition the RF input;
generating a local oscillator signal using a local RF oscillator coupled to an RF splitter, wherein the RF splitter separates the local oscillator signal into two outputs, a first output is connected to the first mixer, and a second output is connected to the second mixer,
outputting a multiplexed binary data stream using an analog to digital convertor (ADC) connected to the output of the first and second mixers, wherein the outputs represent a pseudo random number (PRN) code modulated backscattered signal received from a fiber under test;
using a second module configured to:
correlate a PRN reference with the received PRN code modulated backscattered signal,
perform control operations;
using a third module comprising control logic for the modular fiber optic interferometry control system configured to:
store executable instructions on a computer readable memory, the instructions, when executed by one or more processors, cause the one or more processors to perform operations comprising at least one of data logging, communications, memory management, and light source management.
18. The method of claim 17 , further comprising a fourth module for generating a power stream wherein the one or more processors perform operations comprising at least one of wild point smoothing, circle correction, vector determination, merge change in phase data, and merge power data.
19. The method of claim 17 , further comprising a module for event interrogation wherein the one or more processors perform operations comprising at least one of bandpass filtering and fast Fourier transform to output at least one of an audio stream and a data stream.
20. The method of claim 17 , further comprising a module for noise reduction wherein the one or more processors perform operations comprising at least one of Kalman filtering, Bayesian inferencing, Bayesian updating, Markovian prediction, bandpass filtering, Butterworth filtering, adaptive filtering, background subtraction, and model fitting.