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Insertion Loss

Author: the photonics expert

Definition: power losses due to insertion of a device

Categories: article belongs to category general optics general optics, article belongs to category fiber optics and waveguides fiber optics and waveguides

Units: %, [[decibel|dB]]

DOI: 10.61835/yma   Cite the article: BibTex plain textHTML

If an optical device is inserted into a setup, some of the optical power may be lost in the device or at optical interfaces. Some examples:

The insertion loss (or attenuation) is usually specified in decibels, calculated as 10 times the logarithm of base 10 of the ratio of input and output powers. For fiber connectors, for example, it is often of the order of 0.5 dB. High-quality fusion splices may reach values like 0.02 dB.

For high-power devices, a high insertion loss is often unwanted not only due to the power loss but also because of possibly strong heating effects resulting from absorbed light.

A convenient method for measuring insertion loss is optical time-domain reflectometry. With that, the insertion loss of multiple optical elements along a fiber can be measured separately.

Optical Loss Testers

For use mainly in optical fiber communications, there are optical loss testers with which insertion losses can be quite conveniently measured.

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Questions and Comments from Users


Is there a significant difference between SMF insertion loss and MMF insertion loss? If so, which one is usually higher?

The author's answer:

Multimode fibers often have higher propagation losses than single-mode fibers. That, however, would not usually be called an insertion loss; that term is more commonly used for specific devices or splices.

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