Fiber optic monitor for railroad switch

Abstract

An improved railroad switch monitoring unit of the type that determines whether a mobile rail is brought into a closed state or an open state with respect to a stationary rail. The improvement comprises a fiber Bragg grating (FBG) included in the monitoring unit that is used to determine, based on stress able change in the resonant wavelength of the FBG, whether the mobile rail and the stationary rail are closed or open.

1 . An improved railroad switch monitoring unit of the type that determines whether a mobile rail is brought into a closed state or an open state with respect to a stationary rail, the improvement comprising: 
 a fiber Bragg grating (FBG) included in the monitoring unit to determine based on stress able change in the resonant wavelength of said FBG whether the mobile rail and the stationary rail are in any of the closed state, the open state, or neither.    
   
   
       2 . A method for determining whether a mobile rail and a stationary rail of a railroad switch are in a closed state or an open state, the method comprising: 
 providing a fiber Bragg grating (FBG) placed such that operation of the mobile rail with respect to the stationary rail stress ably effects the resonant wavelength of said FBG;    detecting the resonant wavelength of said FBG; and    determining based on the resonant wavelength of said FBG whether the mobile rail and the stationary rail are in the closed state, the open state, or neither.    
   
   
       3 . The method of  claim 2 , wherein said step of detecting includes: 
 defining a closed wavelength to be the resonant wavelength of said FBG when the mobile rail and the stationary rail are in the closed state;    defining an open wavelength to be the resonant wavelength of said FBG when the mobile rail and the stationary rail are in the open state;    directing a light beam including at least one of said closed wavelength and said open wavelength to said FBG via an optical fiber;    receiving any reflected portion of said light beam back from said FBG via said optical fiber; and    sensing whether said any reflected portion includes any of said closed wavelength and said open wavelength.    
   
   
       4 . An apparatus for monitoring operation of a railroad switch having a stationary rail and a mobile rail position able into a closed state or an open state with respect to the stationary rail, the apparatus comprising: 
 a fiber Bragg grating (FBG); and    a mount holding said FBG such that positioning of the mobile rail with respect to the stationary rail changes the resonant wavelength of said FBG.    
   
   
       5 . The apparatus of  claim 4  wherein a closed wavelength is defined to be the resonant wavelength of said FBG when the mobile rail and the stationary rail are in the closed state and an open wavelength is defined to be the resonant wavelength of said FBG when the mobile rail and the stationary rail are in the open state, and wherein the apparatus is comprised within a monitoring system including: 
 a light source to produce a first light beam including at least one of said closed wavelength and said open wavelength;    a light receiver to receive a second light beam and sense whether it includes any of said closed wavelength and said open wavelength; and    an optical fiber to direct said first light beam from said light source to said FBG and to return any said second light beam reflected from said FBG to said light receiver.    
   
   
       6 . The apparatus of  claim 4 , wherein said light source includes a laser.  
   
   
       7 . The apparatus of  claim 6 , wherein said laser concurrently produces a range of light wavelengths that encompass said closed wavelength and said open wavelength.  
   
   
       8 . The apparatus of  claim 6 , wherein said laser tune ably produces a specific light wavelength within a range of light wavelengths that encompass said closed wavelength and said open wavelength.