Fiber-optic sensor with two different wavelengths of light traveling together through the sensor head
First Claim
1. A fiber-optic sensing system comprising:
- a light source emitting light of at least a first frequency and a second frequency;
fiber-optic sensing head means, having channeling means comprising a single light path for both frequencies therethrough, for varying light of said first frequency channeled thereto as a function of an environmental parameter to which said fiber-optic sensing head means is subjected;
detection means for detecting light of both said frequencies channeled thereto and for generating a detection signal indicative of sensed variations in the detected lightsensing fiber-optic channel means for directing light of both frequencies from said light source to said fiber-optic sensing head means and for directing light from said fiber-optic sensing head means to said detection means;
coupling means in said fiber-optic channel means between said light source and said fiber-optic sensing head means to merge the light paths of said first and second frequencies of light into a single light path for both frequencies through said fiber-optic sensing head means;
reference fiber-optic channel means for directing light of both frequencies from said light source to said detection means without passing though said fiber-optic sensing head means; and
signal processing means coupled to said detection means for processing the signals generated from light channeled through said sensing fiber-optic sensing means and for processing the detection signal generated from light channeled through said reference fiber-optic channel means, said processing being carried out in order to generate an indicating signal that accurately indicates the value of said environmental parameter as a function of said variation in the first frequency of light received from said fiber-optic sensing head means as compared to said second frequency of light received from said fiber-optic sensing head means and to both frequency portions of light received through said reference fiber-optic channel means.
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Accused Products
Abstract
A fiber-optic system for measuring a desired environmental parameter, such as temperature, is disclosed. The system includes a fiber-optic sensing head that alters light of a prescribed frequency as a function of the environmental parameter to be measured. Light not of the prescribed frequency is not so altered. In a preferred embodiment of the fiber-optic sensing head, a semiconductor material is positioned between two substantially parallel optical fibers at a distal end of the fibers. One fiber serves as in input channel and the other fiber serves as an output channel. Both fibers approach the semiconductor material from the same direction. Light channeled to the semiconductor material is reflected at the distal end of the input fiber so as to pass through the semiconductor material, and then is reflected again at the distal end of the output fiber so as to pass back out the output fiber. The semiconductor material absorbs the light of the prescribed frequency as a function of temperature. By monitoring the intensity of the light of the first frequency at the output channel, a measurement of the temperature to which the fiber-optic sensing head is subjected can be determined. To remove the influence of input light intensities, fiber attenuation, and the like, from the temperature measurement, lights of two frequencies, only one of which is the prescribed frequency, are selectively directed to an optical detector through the fiber-optic sensing head and through a separate fiber-optic reference channel. The four measurements thus obtained at the optical detector--prescribed frequency through sensing head, prescribed frequency through reference channel, non-prescribed frequency through sensing head, and non-prescribed frequency through reference channel--are appropriately processed in order to generate a signal that has all variations or influences removed therefrom except the temperature variations of the sensing head.
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Citations
38 Claims
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1. A fiber-optic sensing system comprising:
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a light source emitting light of at least a first frequency and a second frequency; fiber-optic sensing head means, having channeling means comprising a single light path for both frequencies therethrough, for varying light of said first frequency channeled thereto as a function of an environmental parameter to which said fiber-optic sensing head means is subjected; detection means for detecting light of both said frequencies channeled thereto and for generating a detection signal indicative of sensed variations in the detected light sensing fiber-optic channel means for directing light of both frequencies from said light source to said fiber-optic sensing head means and for directing light from said fiber-optic sensing head means to said detection means; coupling means in said fiber-optic channel means between said light source and said fiber-optic sensing head means to merge the light paths of said first and second frequencies of light into a single light path for both frequencies through said fiber-optic sensing head means; reference fiber-optic channel means for directing light of both frequencies from said light source to said detection means without passing though said fiber-optic sensing head means; and signal processing means coupled to said detection means for processing the signals generated from light channeled through said sensing fiber-optic sensing means and for processing the detection signal generated from light channeled through said reference fiber-optic channel means, said processing being carried out in order to generate an indicating signal that accurately indicates the value of said environmental parameter as a function of said variation in the first frequency of light received from said fiber-optic sensing head means as compared to said second frequency of light received from said fiber-optic sensing head means and to both frequency portions of light received through said reference fiber-optic channel means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17)
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16. An optical fiber coupler comprising:
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fiber-optic sensing head means for affecting one frequency portion of light channeled thereto as a function of an environmental parameter to which said fiber-optic sensing head means is subjected; input fiber-optic channeling means for directing light of a plurality of frequencies including said one frequency along a single light path from a light source remaining together through said fiber-optic sensing head means; and output fiber-optic channeling means for directing said light of a plurality of frequencies including said one frequency away from said fiber-optic sensing head means. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. In an environmental parameter measurement system that includes:
- (1) first and second light sources for generating light at first and second frequencies, respectively;
(2) an optical sensing head for varying light of the first frequency channeled therethrough as a function of an environmental parameter to which said optical sensing head is subjected, and wherein light of the second frequency channeled through said optical sensing head is not so affected; and
(3) optical detection means for detecting a desired parameter, such as intensity, of light directed thereto;
a method for accurately measuring said environmental parameter comprising the steps of;(a) placing said optical sensing head in an environment where the optical sensing head is subjected to the environmental parameter that is to be measured; (b) channeling light of both said first and second frequencies through a single path said optical sensing head to said optical detection means; (c) measuring at said optical detection means, the desired parameter of the light of said first frequency channeled through said optical sensing head; (d) measuring, at said optical detection means, the desired parameter of the light of said second frequency channeled through said optical sensing head; (e) channeling light of both said first and second frequencies through a reference channel, without passing said light through said optical sensing head, to said optical detection means; (f) measuring, at said optical detection means, the desired parameter of the light of said first frequency channeled through said reference channel; (g) measuring, at said optical detection means, the desired parameter of the light of said second frequency channeled through said reference channel; and (h) generating an environmental parameter measurement signal that comprises the product of the measurements of steps (d) and (f) divided by the product of the measurements of steps (c) and (g). - View Dependent Claims (29, 30)
- (1) first and second light sources for generating light at first and second frequencies, respectively;
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31. An optical sensing system comprising:
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a light source emitting light of at least a first frequency and a second frequency; sensing head means having channeling means comprising a single light path for both frequencies therethrough for varying light of said first frequency channeled thereto as a function of an environmental parameter to which said sensing head means is subjected; detection means for detecting light of both said frequencies channeled thereto and for generating a detection signal indicative of sensed variations in the detected light; first light direction means for directing light of both frequencies from said light source to said sensing head means and for directing light from said sensing head means to said detection means; coupling means between said light source and said sensing head means to merge the light paths of said first and second frequencies of light into a single light path for both frequencies through said sensing head means; second light direction means for directing light of both frequencies from said light source to said detection means without passing through said sensing head means; and processing means for processing the signals generated from by said detection means and for generating an indicating signal therefrom that accurately indicates the value of said environmental parameter to which said sensing head means is subjected. - View Dependent Claims (32, 33)
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34. An optical sensing system comprising:
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a broad band light source for generating light having a spectrum of frequencies therein including at least a prescribed first frequency and a second frequency; sensing head means, having channeling means comprising a single light path for both frequencies therethrough, for varying light of said first frequency directed thereto as a function of an environmental parameter to which said sensing head means is subjected; detection means for detecting light of both said frequencies directed thereto and for generating a detection signal indicative of sensed variations in the detected light; light direction means for directing light of said plurality of frequencies from said light source to said sensing head means and for directing light from said sensing head means to said detection means; coupling means between said light source and said sensing head means to merge the light paths of said plurality of frequencies of light into a single light path through said sensing head means; and processing means for processing signals generated from by said detection means and for generating an indicating signal therefrom that accurately indicates the value of said environmental parameter to which said sensing head means is subjected. - View Dependent Claims (35, 36, 37, 38)
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Specification