Raman-based Distributed Temperature Sensing (DTS) utilizing fiber probes is an effective method to determine
temperature over distances up to 20km. Active Plug & Play is based on a full DTS solution (DTS system with
PerfectVision<sup>TM</sup>, Calibration Module, SensorTran DTS Commander software) using a dual laser approach with light
sources operating at different wavelengths to determine and compensate for the wavelength dependent local variations in
fiber attenuation. The wavelength values for the anti-Stokes Raman return of the primary light source is approximately
the same value as the Stokes Raman return of the secondary source. This solution enables the first auto-correcting
calibration for DTS.