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Fiberstore (FS.COM) | Understanding Loss in Fiber Optic Page 1
Fiber optic transmission has various advantages over other transmission methods like copper orradio transmission. Fiber optic which is lighter, smaller and more flexible than copper can transmitsignals with faster speed over longer distance. However, many factors can influence theperformance of fiber optic. To ensure the nice and stable performance of the fiber optic, manyissues are to be considered. Fiber optic loss is a negligible issue among them, and it has been a toppriority for many engineers to consider during selecting and handling fiber optic. This article willoffer detailed information of fiber optic loss.
When a beam of light which carrying signals travels through the core of fiber optic, the strength ofthe light will become lower. Thus, the signal strength becomes weaker. This loss of light power isgenerally called fiber optic loss or attenuation. This decrease in power level is described in dB.During the transmission, something be happened and causes the fiber optic loss. To transmit opticalsignals smoothly and safely, fiber optic loss must be decreased. The cause of fiber optic loss locatedon two aspects: internal reasons and external causes of fiber optic, which are also known asintrinsic fiber core attenuation and extrinsic fiber attenuation.
Intrinsic Fiber Core Attenuation
Internal reasons of fiber optic loss caused by the fiber optic itself, which is also usually calledintrinsic attenuation. There are two main causes of intrinsic attenuation. One is light absorption andthe other one is scattering.
Light absorption is a major cause of fiber optic loss during optical transmission. The light isabsorbed in the fiber by the materials of fiber optic. Thus light absorption is also known as materialabsorption. Actually the light power is absorbed and transferred into other forms of energy like heat,due to molecular resonance and wavelength impurities. Atomic structure is in any pure material andthey absorb selective wavelengths of radiation. It is impossible to manufacture materials that aretotal pure. Thus, fiber optic manufacturers choose to dope germanium and other materials withpure silica to optimize the fiber optic core performance.
Scattering is another major cause for fiber optic loss. It refers to the scattering of light caused bymolecular level irregularities in the glass structure. When the scattering happens, the light energy is
Understanding Loss inFiber Optic
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scattered in all direction. Some of them is keeping traveling in the forward direction. And the lightnot scattered in the forward direction will be lost in the fiber optic link as shown in the followingpicture. Thus, to reduce fiber optic loss caused by scattering, the imperfections of the fiber opticcore should be removed, and the fiber optic coating and extrusion should be carefully controlled.
Extrinsic Fiber Attenuation
Intrinsic fiber core attenuation including light absorption and scattering is just one aspect of thecause in fiber optic loss. Extrinsic fiber attenuation is also very important, which are usually causedby improper handling of fiber optic. There are two main types of extrinsic fiber attenuation: bendloss and splicing loss.
Bend loss is the common problems that can cause fiber optic loss generated by improper fiber optichandling. Literally, it is caused by fiber optic bend. There are two basic types. One is micro bending,and the other one is macro bending (shown in the above picture). Macro bending refers to a largebend in the fiber (with more than a 2 mm radius). To reduce fiber optic loss, the following causes ofbend loss should be noted:
Fiber core deviate from the axis; Defects of manufacturing; Mechanical constraints during the fiber laying process; Environmental variations like the change of temperature, humidity or pressure.
Fiber optic splicing is another main causes of extrinsic fiber attenuation. It is inevitable to connectone fiber optic to another in fiber optic network. The fiber optic loss caused by splicing cannot beavoided, but it can be reduced to minimum with proper handling. Using fiber optic connectors ofhigh quality and fusion splicing can help to reduce the fiber optic loss effectively.
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The above picture shows the main causes of loss in fiber optic, which come in different types. Toreduce the intrinsic fiber core attenuation, selecting the proper fiber optic and optical componentsis necessary. To decrease extrinsic fiber attenuation to minimum, the proper handling and skillsshould be applied.
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Notice: This document is for informational purposes only and does not set forth any warranty, expressed orimplied, concerning any equipment, equipment features, or service offered or to be offered by Fiberstore.Fiberstore reserves the right to make changes to this document at any time, without notice, and assumes noresponsibility for its use. This information document describes features that may not be currently available.Contact a Fiberstore sales team for information on feature and product availability.
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