Reflection-mode fiber sensing devices

Abstract

Fiber sensors formed on side-polished fiber coupling ports based on evanescent coupling are described. Such sensors may be configured to measure various materials and may be used to form multi-phase sensing devices. A Bragg grating may be implemented in such sensors to form reflective fiber sensors.

1 - 14 . (canceled)  
     
     
         15 . A method, comprising: 
 providing a fiber sensor system having a plurality of reflective fiber sensors in a single fiber;    injecting a probe beam into the single fiber;    measuring reflected light from the fiber sensors; and    using timings of arrival of the reflected light to distinguish signals from different fiber sensors.    
     
     
         16 . The method as in  claim 15 , wherein the reflective fiber sensors are configured to operate at the same wavelength.  
     
     
         17 . A device, comprising: 
 a fiber having an input terminal to receive a probe beam;    a plurality of fiber sensors formed at different locations in the fiber, each fiber sensor located at a side surface formed on a side surface on an exposed portion of fiber core by removing a portion of fiber cladding and fiber core, each fiber sensor comprising a reflective Bragg grating which is within a reach of an evanescent field of guided light in the fiber to reflect guided light that satisfies a Bragg resonance condition, wherein the fiber sensors reflect the probe beam to produce optical reflected signals propagating against the probe beam;    an optical element in the fiber to couple the reflected signals out of the fiber;    an optical detector to receive the reflected signals from the optical element; and    a processing unit to process output from the optical detector to distinguish signals from different sensors based on timings of arrival of the signals and to extract information in each signal.    
     
     
         18 . The device as in  claim 17 , wherein the reflective Bragg is formed on exposed portion of the fiber core.  
     
     
         19 . The device as in  claim 17 , wherein each fiber sensor further comprises an optical overlay layer formed on the side surface to have an index greater than the fiber core, and wherein the reflective Bragg grating is formed on the optical overlay layer.