Fiber-linked interferometric pressure sensor

Abstract

A fiber-optic pressure sensor is described which uses a diaphragm to modulate the mirror separation of a Fabry-Perot cavity (the sensing cavity). A multimode optical fiber delivers broadband light to the sensing cavity and returns the spectrally modulated light which the cavity reflects. The sensor's output spectrum is analyzed using It tunable Fabry-Perot cavity (the reference cavity) to determine the mismatch in the mirror separations of the two cavities. An electronic servo control uses this result to cause the mirror separation of the reference cavity to equal that of the sensing cavity. The displacement of the pressure-sensing diaphragm is then obtained by measuring the capacitance of the reference cavity's metal-coated mirrors. Relative to other fiber-optic sensors, an important advantage of this instrument is its high immunity to the effects of variations in both the transmissivity of the fiber link and the wavelength of the optical source.

<title>Fourier transform spectrometry for fiber-optic sensor systems</title>

“…by cos[2irvg(v)z0], and integrating with respect to z0, one obtains i(v)=--(vg(v))fI(z0)cos(27rvg(v)z0)dz0. (7) This equation allows the optical spectrum to be derived from the measured interferogram.…”

Demodulation algorithm for optical fiber fabry-perot interference sensor

“…After their successful production in 1988 [3] and 1991 [4] respectively, investigators have done substantial research on the sensor's structure, materials, preparation technology, and demodulation algorithm [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. And also, extrinsic OFFPI sensors are divided into diaphragm-free type [5][6][7][8] and diaphragm type [13][14][15][16][17][18]. Various demodulation algorithms are then constantly proposed in view of resolution of sensors [20][21][22][23].…”

Multiplexing optical fiber low coherence and high coherence interferometric system with large range and high resolution for on-line measurement

“…Hence there is a great amount of interest to employ them for the measurement of a large variety of parameters such as displacement, vibration, velocity, strain, pressure and temperature [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Compared to an optical fiber high coherence interferometric sensing system (OFH-CIS) which is illuminated with a high coherence laser source, an optical fiber low coherence interferometric sensing system (OFLCIS) which is illuminated with a broadband light source has the advantage of being capable of performing absolute measurement [9] which is remained an unsolved problem with OFHCIS that the value of the measurand can be obtained directly by comparing the measurand to the standard quantity.…”