Sensor apparatus with polarization maintaining fibers
AssigneeCorning Incorporated
InventorDaniel A. Nolan
Life of this patent
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Abstract
A distributed sensor (10) includes a plurality of stages (24, 28, 32, 36, 40) connected in series, each stage incorporating a length of polarization maintaining fiber (12) exposed to a phenomena such as mechanical deformation or temperature to be sensed. Inter-mode couplers are provided between the sensing fibers (26, 30, 34, 38) of the various stages. The overall transfer function of the device at a plurality of wavelengths is deconvoluted to determine the birefringence of each sensing region and does monitor plural phenomena independently of one another.
Claims35
Optical sensing apparatus for sensing a plurality of phenomena, the apparatus including a plurality of stages connected in series order from a first stage to a last stage, each said stage comprising:
- (a) a polarization-maintaining sensing fiber having different propagation constants for light in first and second polarization modes, said sensing fiber having input and output ends;
- (b) launching means for launching light in both of said polarization modes into said sensing fiber at said input end, whereby light will propagate in both of said polarization modes to the output end;
- (c) combining means for combining light propagated to the output end of the sensing fiber in both of said polarization modes into one or more common polarization modes, whereby the amplitude of the combined light will vary with the phase relationship between the light propagated in the first mode and the light propagated in the second mode at the output end of the fiber;
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- (d) exposure means for mounting the sensing fiber so that the sensing fiber is exposed to a phenomenon to be sensed and so that such phenomenon will alter the length of the sensing fiber, the difference between said propagation constants, or both, whereby said phase relationship and said amplitude will vary with the phenomenon to be sensed,
- the combining means of each stage other than the last stage being connected to the launching means of the next stage in said series so that combined light from each said stage other than the last stage in the series will be launched into the sensing fiber of the next stage in the series.
A unitary fiber including a polarization-maintaining sensing section having a uniform spin rate and having different propagation constants for light in first and second polarization modes, said sensing section having input and output ends, the unitary fiber further including a plurality of spin sections wherein the spin rate varies along the length of the fiber within each spin section, a first one of said spin sections being connected to the input end of the sensing section, a second one of said spin sections being connected to the output end of said sensing section whereby light supplied to said first spin section will be coupled into both polarization modes of said sensing section and light propagated along said sensing section in both polarization modes will be combined in one or more common modes in said second spin section.
A method of sensing a plurality of phenomena comprising the steps of
- (a) directing light at a plurality of wavelengths through a series of stages each including a polarization-maintaining sensing fiber having different propagation constants for light in the first and second polarization modes and a combiner for combining light propagated to an output end of the sensing fiber in both of said polarization modes into combined light of a single polarization mode, so that the light is launched into the sensing fiber of the first stage in both polarization modes and so that the combined light from each stage is launched into the sensing fiber of the next stage in both polarization modes until the light reaches the combiner last stage;
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- (b) exposing the sensing fiber of each stage to a phenomenon to be sensed so that such phenomenon to be sensed will alter the length of the sensing fiber, the difference between the propagation constants of such fiber, or both, whereby a relationship between wavelength of light and the amplitude of the combined light from the last said stage will vary with all of the phenomena to be sensed.
Dependencies are inferred from the claim text.