Phase-Sensitive Optical Time Domain Reflectometer with Dual-Wavelength Probe Pulse

A dual-wavelength pulse strategy is proposed to reduce the fading phenomenon in a phase-sensitive optical time domain reflectometer (ϕ-OTDR). The theoretical basis behind this dual-wavelength pulse strategy is presented and an experimental setup is described to help validate the proposed strategy. Through the experimental tests, a 37.79% improvement in detection for available points along the fiber is achieved when 1550.000 nm and 1550.138 nm wavelength signals are applied. The different wavelength tests show that at least a 0.012 nm or 1.498 GHz difference should be applied in a dual-wavelength pulse and an average 30% detecting improvement can be achieved when one wavelength changes from 1549.950 nm to 1550.100 nm. In addition, the dual-wavelength strategy makes the system response more stable and consistent along the sensing optical fiber.