Coherent OFDR Using Phase Decorrelated Lightwaves for Characterizing Optical Fiber Transmission Lines

Coherent optical frequency domain reflectometry (C-OFDR) using phase decorrelated lightwaves is demonstrated at a wavelength of 1.55 µm by employing a linewidth narrowed laser diode and an external electro-optical (EO) phase modulator. Rayleigh backscattering and Fresnel reflection from a 30-km-long optical fiber are observed, and a spatial resolution of 5 m is achieved at the far end of the test fiber. This is the best result to date using C-OFDR for such a long optical fiber.