fiber splices (original) (raw)

Author: the photonics expert (RP)

Definition: joints between fibers for efficient transfer of light from one fiber to the other

Category: fiber optics and waveguides

• optics
  • fiber optics
    * fibers
    * fiber connectors
    * fiber-optic adapters
    * fiber couplers
    * fiber-optic pump combiners
    * fiber bundles
    * fiber endface inspection
    * cleaving of fibers
    * fiber cleavers
    * fiber joints
    * fiber splices
    * fusion splicing of fibers
    * mechanical fiber splices
    * fiber Bragg gratings
    * fiber cables
    * fiber coatings
    * fiber strippers
    * fiber recoaters
    * fiber coils
    * fiber collimators
    * fiber launch systems
    * fiber lenses
    * fiber loop mirrors
    * fiber patch panels
    * fiber shuffles
    * fiber-optic attenuators
    * fiber-optic plates
    * fiber-optic tapers
    * (more topics)

Related: fiber jointsmechanical fiber splicesfusion splicing of fibersfiber endface inspection

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DOI: 10.61835/z4d Cite the article: BibTex BibLaTex plain textHTML Link to this page! LinkedIn

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Contents

What are Fiber Splices?

Fiber splicing means joining two optical fibers (permanently or temporarily) such that light guided in one fiber and reaching the joint (splice) can be transferred into the second fiber with low insertion loss. Imperfect coupling means that some of the light coming from the first fiber gets into cladding modes of the second fiber, or that light is reflected at the splice.

There are two primary types of fiber splicing:

• Fusion splicing involves strongly heating the two fiber endfaces until the material becomes soft and then joining them so that they fuse together. This process results in a permanent splice, often with very low insertion loss.
• Mechanical splicing means firmly holding the accurately aligned fiber endfaces with suitable consumables, without fusing them. Between the fiber ends, one may apply some index-matching gel or adhesive.

Each method has its own techniques, advantages, and applications:

• Fusion splicing requires expensive equipment, but does not need consumables. It generally reaches lower insertion loss and very high return loss, i.e., the highest quality optical connections.
• Mechanical splicing can be done with comparatively simple equipment (although precision splicers can also be expensive), but one requires some consumables for each splice. The optical connection is often of lower quality, although that depends on the circumstances. Temporary connections can often be made.

Splicing can be performed with both single-mode fibers and multimode fibers, but tends to be more difficult to obtain with perfect quality in the former case. Fusion splicing is possible for glass fibers but (with adapted processes) also with plastic optical fibers. Special challenges arise for some specialty fibers, including photonic crystal fibers and fibers with non-common cladding diameters or shapes.

Insertion Loss for Dissimilar Fibers

In the ideal case, any light in guided modes of the first fiber will after the splice propagate in guided modes of the second fiber. This is obviously possible if both fibers have the same design and are well aligned. However, low-loss splicing does not necessarily require that situation. For example, single-mode-to-multimode light transfer (not vice versa) is often possible with low loss. The essential condition is that every relevant guided mode of the first fiber matches either a single mode of the second fiber, or a superposition of such guided modes. The coupling efficiency can be calculated using mode overlaps.

The article on fiber joints gives more details on optical losses and reflections which can occur with splices.

Removing the Fiber Coating

Fiber splices can be made only after removing any protective fiber coatings from the fiber ends, often using some fiber stripper. Therefore, they are often mechanically more sensitive than the original fibers, and should be properly protected. For example, mechanical splices are often put into splice trays, which do not only protect them against direct touching, but also to some extent against pulling the incoming fibers.

It is also possible to recoat fibers after splicing, using a fiber recoater.

Frequently Asked Questions

What is fiber splicing?

Fiber splicing is the process of joining two optical fibers so that light can pass from one to the other with minimal insertion loss and reflection. The connection can be either permanent or temporary.

What are the two main types of fiber splices?

The two main types are fusion splicing, which permanently melts and fuses the fiber ends together, and mechanical splicing, which uses a mechanical assembly to precisely align and hold the fiber ends.

How do fusion and mechanical splicing compare?

Fusion splicing requires more expensive equipment but typically achieves lower insertion loss and higher return loss, creating a high-quality permanent connection. Mechanical splicing is done with simpler tools but requires consumables and may result in a lower-quality connection.

Is it possible to splice two different fibers together with low loss?

Yes, but it depends on the fibers' properties. For example, transferring light from a single-mode fiber to a multimode fiber can have low loss, but the reverse connection is generally lossy due to mode field mismatch.

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