Signal conditioning unit for fiber optic sensors

Details Signal conditioning unit for fiber optic sensors Signal conditioning unit for fiber optic sensors

1995-02-28

1996-09-17

Gonzalez, Frank

Optics: measuring and testing

By particle light scattering

With photocell detection

356352, 25022727, G01B 902

Patent

active

055574068

ABSTRACT:
Apparatus and method (10, 50) for determining the value of a measurand measured by a fiber optic interferometer sensor (24, 72, 110) is provided. The apparatus includes a light source (16, 58, 102) emitting a light having a periodically modulated frequency which is injected into the interferometric sensor. A modulation cycle is initiated by the microcontroller's (12, 56, 116) generation of a trigger signal. A counter (42, 86) begins counting in response to the trigger signal. A first photodetector (20, 66) is coupled to the light source (16, 58, 102) and produces a first electrical signal proportional to the light. A second photodetector (36, 76, 114) is coupled to the fiber optic interferometer sensor (24, 72, 110) and produces a second electrical signal proportional to the light reflected by the sensor or passed through the sensor and affected by the measurand. A comparator (40, 82, 116) compares the second electrical signal with the first electrical signal and detects a crossing of the first and second electrical signals. The counter (42, 86) stops counting in response to a detected signal crossing. The microcontroller (12, 56, 116) then computes a measurand value from the count value for each modulation cycle.

REFERENCES:
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patent: 5452086 (1995-09-01), Bunn
patent: 5452087 (1995-09-01), Taylor et al.
Anthony Dandridge, et al., "Homodyne Demodulation Scheme for Fiber Optic Sensors Using Phase Generated Carrier", IEEE Journal of Quantum Electronics, vol. QE-18, No. 10, Oct. 1982, pp. 1647-1653.
D. A. Jackson, et al., "Pseudoheterodyne Detection Scheme for Optical Interferometers", Electronics Letters, 9th Dec. 1982, vol. 18, No. 25, pp. 1081-1083.
I. J. Bush, et al., "High Performance Interferometric Demodulation Techniques", SPIE vol. 1795 Fiber Optic and Laser Sensors X (1992), pp. 412-420.
Y. Yeh, et al., "In-Line Fabry-Perot Interferometric Temperature Sensor with Digital Signal Processing", SPIE vol. 1584 Fiber Optic and Laser Sensors IX (1991), pp. 72-78.
R. A. Atkins, et al., "Fiber-Optic Pressure Sensors for Internal Combustion Engines", Applied Optics, vol. 33, No. 7, 1 Mar. 1994, pp. 1315-1320.

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