Fiber optic sensors

A fiber optic sensing system comprising:

• an optical fiber having first and second terminal ends,
• a wavelength selective filter adjacent said second terminal end including numerous layers of dielectric materials directly deposited onto said fiber second end having the characteristic that said filter transmits light within a first range of wavelength and reflects light within a second range of wavelengths,
• first light emitting means for producing a reference light signal within said second range of wavelengths,
• second light emitting means for producing a sensing light signal of a wavelength different than that produced by said first light emitting means and within said first range of wavelengths,
• optical means for injecting said reference and sensing light signals into said first fiber end,
• a sensing tip fastened to said fiber second end and having measuring means for modulating said sensing light signal in response to a parameter to be measured,
• photodetector means for sensing the intensity of said reference and sensing light signals returned through said fiber, and
• controller and signal processing means for evaluating the intensity of said returned reference and sensing light signals and providing an output related to said parameter to be measured.

A beam separator assembly for a fiber optic sensing system of the type having a sensing tip with measuring means for sensing a parameter to be measured and modulating the intensity of a sensing light signal which is returned back through an optical fiber, comprising:

• light source means for generating a sensing light signal,
• first optical means for inputting said sensing light signal into an end of said optical fiber,
• a parabolic mirror having an aperture through which said sensing light signal passes before being injected into optical fiber,
• second optical means for enlarging the returned light signal exiting said optical fiber end and directing said returned signal onto said parabolic mirror around said aperture, said parabolic mirror having an optical axis tipped from that of said input and returned sensing light signal, and
• photodetector means for receiving and measuring the intensity of light focused by said parabolic mirror.

A beam separator assembly for a fiber optic sensing system of the type having a sensing tip with measuring means for sensing a parameter to be measured and modulating the intensity of a sensing light signal which is returned back through an optical fiber, comprising:

• light source means for generating a sensing light signal,
• first optical means for inputting said sensing light signal into an end of said optical fiber along an optical axis,
• second optical means for receiving said returned signal emitted from said fiber end along said optical axis and for expanding said returned beam to a diameter larger than said input light beam,
• a parabolic mirror positioned along said optical axis for receiving and focusing said returned light beam, said mirror having an optical axis inclined from said beam optical axis, and
• photodetector means for receiving and measuring the intensity of light focused by said parabolic mirror.

A fiber optic sensing system comprising:

• an optical fiber having first and second terminal ends,
• a wavelength selective filter adjacent said second terminal end including numerous layers of dielectric materials directly deposited onto said fiber second end having the characteristic that said filter transmits light within a first range of wavelength and reflects light within a second range of wavelengths,
• first light emitting means for producing a reference light signal within said second range of wavelengths,
• second light emitting means for producing a sensing light signal of a wavelength different than that produced by said first light emitting means and within said first range of wavelengths,
• optical means for injecting said reference and sensing light signals into said first fiber end,
• a sensing tip fastened to said fiber second end and having measuring means for modulating said sensing light signal in response to a parameter to be measured,
• photodetector means for sensing the intensity of said reference and sensing light signals returned through said fiber, and
• controller and signal processing means for evaluating the intensity of said returned reference and sensing light signals and providing an output related to said parameter to be measured, and further having means for controlling said first and second light emitting means to produce alternate pulses of light and for processing signals from said photodetector means to separate signals related to said returned reference light signal from signals related to said returned sensing light signal, and for comparing the intensity of said returned reference and sensing signals to provide an output related to said parameter to be measured.

A fiber optic sensing system comprising:

• an optical fiber having first and second terminal ends,
• a wavelength selective filter adjacent said second terminal end including numerous layers of dielectric materials directly deposited onto said fiber second end having the characteristic that said filter transmits light within a first range of wavelength and reflects light within a second range of wavelengths,
• first light emitting means for producing a reference light signal within said second range of wavelengths,
• second light emitting means for producing a sensing light signal of a wavelength different than that produced by said first light emitting means and within said first range of wavelengths,
• optical means for injecting said reference and sensing light signals into said first fiber end,
• a sensing tip fastened to said fiber second end and having measuring means for modulating said sensing light signal in response to a parameter to be measured,
• photodetector means for sensing the intensity of said reference and sensing light signals returned through said fiber, and
• controller and signal processing means for evaluating the intensity of said returned reference and sensing light signals and providing an output related to said parameter to be measured, and further for measuring the intensity of light outputted by said first and second light emitting means before said light signals are injected into said fiber for controlling the output of said first and second light emitting means.