Abstract

Fault location and characterization in single-mode optical fibers by optical time domain reflectometry (OTDR) require the utmost in receiver sensitivity. Coherent detection is attractive for OTDR, particularly for long wavelengths (>1 µm), because it provides close to quantum-limited sensitivity. It also radically reduces the dynamic range of the electrical signal in the receiver compared with direct detection. Because of these advantages, rapid progress has been made in realizing a commercial instrument based on these principles.¹

© 1985 Optical Society of America