Two stage processing distributed fiber optic sensing (dfos) interrogator for acoustic modulated signals

Abstract

Distributed fiber optic sensing systems (DFOS) methods, and structures that employ DVS/DAS point sensors and a two-stage processing methodology/structure that advantageously enable point sensors to send sensor data at any time—thereby providing significant processing advantages over the prior art.

1 . A coded distributed fiber optic sensing (DFOS) system comprising:
 a length of optical fiber cable;   a DFOS interrogator system in optical communication with the length of optical fiber cable;   an intelligent analyzer configured to analyze DFOS sensing data received by the DFOS interrogator system;   the distributed fiber optic sensing system CHARACTERIZED BY
 a code sequence generator that generates a coded interrogation sequence; and 
 an out of band signal generator that generates an out-of-band signal (OOS), said OOS being combined with the coded interrogation sequence prior to introduction into the optical fiber cable; 
   wherein the OOS is not used by the DFOS system as part of any DFOS sensing data analysis.   
     
     
         2 . The DFOS system of  claim 1  FURTHER CHARACTERIZED BY the OOS is filtered out of any DFOS sensing data prior to its analysis. 
     
     
         3 . The DFOS system of  claim 2  FURTHER CHARACTERIZED BY the OOS is synchronized with the coded interrogation sequence such that the combination of the two signals is a signal exhibiting a constant amplitude waveform. 
     
     
         4 . The DFOS system of  claim 3  FURTHER CHARACTERIZED IN THAT the combined signals are output to the optical fiber and using the constant amplitude characteristic of the signal an equalized gain for the coded sequence is produced. 
     
     
         5 . The DFOS system of  claim 4  FURTHER CHARACTERIZED IN THAT the DFOS system is integrated in that the optical fiber simultaneously conveys non-sensory telecommunications optical signals. 
     
     
         6 . The DFOS system of  claim 5  FURTHER CHARACTERIZED IN THAT DFOS interrogation signals and the non-sensory telecommunications signals are wavelength-division-multiplexed into the optical fiber. 
     
     
         7 . The DFOS system of  claim 6  FURTHER CHARACTERIZED IN THAT the constant amplitude characteristic of the interrogation signals improves any nonlinear cross-talk characteristics with the telecommunications signals due to reduced cross-phase modulation—as compared with an operation using interrogation signals that did not exhibit the constant amplitude.