Ziebel’s answer products are based around state of the art Distributed Fiber Optic technology.
The DAS and DTS systems are an advanced variant of Optical Time Domain Reflectometer (OTDR) instrumentation that monitors the coherent Rayleigh backscatter noise signature in a fiber optic cable as pulsed light is sent into the fiber. The coherent Rayleigh noise generates fine structure in the backscatter signature of the fiber cable. The system focuses on the Raleigh component to increase its prominence in the backscatter trace.
The interrogator has been optimized to measure small changes in the coherent Rayleigh noise structure that occur from pulse to pulse. Since the coherent Rayleigh noise structure is generated interferometrically within the fiber by the relative locations and strengths of local scattering centers intrinsic to the structure of the glass, very small physical (acoustic or vibration) disturbances at a point in the fiber can make detectable changes in the interferometric signal. Ziebel sets the DAS pulse width to give 15’ resolution with a vertical sampling rate of 2.2’. For the DTS we typically use one minute averaging combined with proprietary processing to enable detecting of changes as low as 0.01⁰.