Large-core Fibers
Acronym: LCF
Definition: optical fibers with relatively large fiber core
More general term: optical fibers
German: Fasern mit großem Kern
Category: fiber optics and waveguides
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Author: Dr. Rüdiger Paschotta
A large-core fiber is an optical fiber having a fiber core which is relatively large. It can be a multimode fiber or a single-mode fiber.
Large-core Multimode Fibers
Large-core multimode fibers have a core diameter which is well above the typically used 50 μm or 62.5 μm of telecom fibers – for example, 100 μm or even 400 μm. The core is often not much smaller than the fiber cladding (see Figure 1). The cladding diameter may substantially go beyond the usual 125 μm in order to realize even larger cores. The number of guided fiber modes is then usually very high.
Frequently, such fibers have a pure silica fiber core (rather than e.g. a germanosilicate core) and a fiber cladding with somewhat reduced refractive index, e.g. achieved with fluorine doping. For realizing a high numerical aperture, however, one may still use fibers with germanosilicate core.
Typical applications of large-core multimode fibers are the passive transport of light e.g. in the context of illumination, laser material processing or optical pumping of solid-state lasers.
Large-core Single-mode Fibers
If a large-core fiber is a single-mode fiber, it also has a large effective mode area. Here, the term large mode area fiber is more common and more appropriate, since the large mode area is a particularly important property: it results in reduced nonlinear effects combined with a high beam quality.
Suppliers
The RP Photonics Buyer's Guide contains 15 suppliers for large-core fibers. Among them:
NKT Photonics
Our Crystal Fibre portfolio of specialty fibers spans from nonlinear fibers optimized for octave spanning supercontinuum generation, over the World’s largest single mode ytterbium gain fibers for high power lasers and amplifiers, to advanced hollow core fibers guiding the light in air. Our single-mode LMA fibers are also available as patch cords with standard termination in our aeroGUIDE product range.
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See also: fibers, large mode area fibers, effective mode area
and other articles in the category fiber optics and waveguides
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