Backreflection is a process that occurs in a cable plant where light is reflected back towards its source. It is typically caused by a glass-air interface at a connector interface, which creates a reflection due to the difference in refractive indices between the two materials. Backreflection can cause several issues including increased noise on the line, reduced signal strength, and increased power consumption.
The amount of backreflection is affected by the quality of the connectors and the amount of splicing that is done in the cable plant. High-quality connectors with low insertion loss and return loss reduce the amount of backreflection. Additionally, the use of fusion splicing, which eliminates the glass-air interface, can reduce backreflection.
Backreflection is measured in decibels (dB), and any value above -36 dB is considered unacceptable, as it can cause signal degradation. The most common way to measure backreflection is with an Optical Time Domain Reflectometer (OTDR), which uses a pulse of light to measure the amount of backreflection in a fiber.
Overall, backreflection is an important factor to consider when designing a cable plant. It is important to use quality connectors and splicing techniques to reduce the amount of backreflection and ensure that the signal remains strong. Additionally, it is important to regularly check for backreflection with an OTDR to ensure that the cable plant is functioning properly.