Both reflectance and ORL are in units of dB but reflectance is always a negative value while ORL is a positive value. Reflectance (which has also been called "back reflection" or optical return loss) of a connection is the amount of light that is reflected back up the fiber toward the source by light reflections off the interface of the polished end surface of the mated connectors and air. It is also called. Optical return loss for individual events, i. the reflection above the fiber backscatter level, relative to the source pulse, is called reflectance. Poor ORL is commonly caused by dirty connectors, poor splices, mismatched connector types, or damaged fibers.
