Dynamic optical waveguide sensor

Abstract

Methods and apparatuses that sense physical parameters, such as pressure and strain, using optical waveguide sensors are described. A light source emits light at a predetermined wavelength along an optical waveguide having a fiber Bragg grating optical sensing element. That sensing element reflects light in accord with a sloped -shape function of reflected light amplitude verses wavelength. A receiver converts the reflected light into electrical signals and an analyzer then determines a physical parameter based on changes of amplitude of the reflected light. The analyzer also maintains the wavelength of the light such that the wavelength corresponds to a slope wavelength of the shape function.

1 . An optical sensor comprising: 
 an optical waveguide with a first fiber Bragg grating having a first Bragg wavelength, a second fiber Bragg grating having a second Bragg wavelength, and a long period grating disposed between said first fiber Bragg grating and said second fiber Bragg grating;    a light source for emitting light at said first Bragg wavelength and at said second Bragg wavelength;    a first receiver for converting reflected light at said first Bragg wavelength into first electrical signals;    a second receiver for converting reflected light at said second Bragg wavelength into second electrical signals;    a coupler for coupling said light into said optical waveguide, for coupling reflected light at said first Bragg wavelength to said first receiver, and for coupling reflected light at said second Bragg wavelength to said second receiver; and    an analyzer for receiving said first and said second electrical signals and for using said first and said second electrical signals to determine a physical parameter applied to said long period grating.    
   
   
       2 . The optical sensor of  claim 1  wherein said physical parameter changes an amplitude of reflected light at said second Bragg wavelength.  
   
   
       3 . The optical sensor of  claim 2  wherein said physical parameter is stress.  
   
   
       4 . The optical sensor of  claim 2  wherein said physical parameter is strain.  
   
   
       5 . The optical sensor of  claim 2  wherein said physical parameter is pressure.  
   
   
       6 . The optical sensor of  claim 1 , further including a filter disposed between said coupler and said first receiver.