The ratio, in dB, of light launched into a component or link to light reflected back toward the source, stated as a positive number. Applied to a whole link it is called optical return loss, or ORL, and includes every reflection plus backscatter. A single UPC connector typically achieves 50 to 55 dB and an APC connector better than 60 dB; strong reflections disturb lasers and add noise on PON and analog video systems.
ORL on the video feed is only 32 dB, somebody left a UPC jumper or an open connector in that path.
Also heard as
- ORL
- optical return loss
Do not mix it up with
- Reflectance: Reflectance describes one reflective event as a negative dB value; return loss is a positive number usually applied to a whole link.
Related terms
Reflectance
The fraction of light reflected by a single event such as a connector, in dB, where more negative is better.
APC
Angled Physical Contact: a singlemode connector polish with an 8 degree angle that sends reflections into the cladding.
UPC
Ultra Physical Contact: a domed singlemode connector polish with no angle, color-coded blue.
Insertion loss
The optical power lost when a component or a whole link is placed in the light path, measured in dB.