QUESTION: In looking up the IL effect of Return Loss, I found definitions in your FOC Glossary (https://focenter.com/foc-glossary/) for IL, IL/RL, RL. In addition to these definitions:
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Insertion Loss: The ratio between the power received at a specified load before and after the insertion of a filter at a given frequency. It is an indication of the attenuation provided by a filter.
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Return Loss: The Channel Return Loss (RL) is a measure of the consistency of the impedance down the length of not just the cable, but also the connections and the patch cables.
Can you provide any info on the IL effect of Return Loss?
ANSWER:
Regarding the IL effect of Return Loss, Return Loss in an connection is that part of the optical power reflected back to the source, usually expressed as how many dB less that the forward power. It is usually regarded as a bad thing, you want as much of the light to as possible to get to the receiver and reflections, if you are very unlucky can cause instability.
Reflectance or optical return loss (which has also been called “back reflection”) 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.
Based upon that definition a PC connector should not have any back reflection since PC stands for physical contact. But in reality the surfaces have some non-planarity and therefore the glass air glass interface follows the Fresnel equations.
A detailed description of the process and how it affects system loss is on the FOA website: https://www.thefoa.org/tech/ref/testing/test/reflectance.html
ADDITIONAL CONTENT & RESOURCES:
- Category Resource: FOC Test Page
- Find More Information in this Blog: Insertion Loss: How Offsets Can Give Unexpected Results (Gains)
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