Zero dead-zone OTDR with high-spatial resolution for short haul applications

The existence of dead-zones is an important drawback for optical time-domain reflectometers (OTDR), specially in short haul applications with a large number of optical components. In this letter, we present an OTDR system with high spatial resolution based on the time-correlated single photon counting (TC-SPC) technique. This system overcomes the deadzone problem by monitoring the spontaneous Stokes Raman emission (SSRE) to avoid the intense Fresnel reflections. The high sensitivity of the TC-SPC technique (-120 dBm) permits a high-loss budget within reasonable measurement integration times.