In optical transmission media, the optical return loss is calculated from the ratio of the light energy fed into an optical waveguide to the reflected light energy. The optical return loss is specified in decibels( dB).
Optical return loss (ORL) is the amount of light that is reflected back to the optical transmitter due to scattering in the optical fiber. Optical Return Loss (ORL) characterizes the quality of the optical fiber, splices and FO connectors. It is directly dependent on the precision in manufacturing, as inconsistencies in production directly affect it. The values for optical return loss can be improved by face coupling of the optical waveguides. This is then referred to as high return loss( HRL).
Optical return loss can take positive values between infinity and 1,000; a high dB value indicates good return loss. Typical values for multimode fibers are 20 dB, at wavelengths of 850 nm and 1300 nm, and 26 dB for single- mode fibers at 1,300 nm and 1,550 nm. For standard FO connectors, the return loss values are between 0.3 dB and 0.5 dB. To measure optical return loss, there is a special reference measurement adapter, the Optical Loss Test Set( OLTS), whose loss values are less than 0.2 dB for monomode fibers and less than 0.1 dB for multimode fibers.