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Telecom Fibers

Definition: optical fibers for use in optical fiber communications

German: Telekom-Fasern

Categories: lightwave communications, fiber optics and waveguides

How to cite the article; suggest additional literature

Telecom fibers are optical fibers which are used in optical fiber communications. Mainly the following types of telecom fibers are used:

A standard single-mode telecom fiber for the 1.3- or 1.5-μm wavelength region is the SMF-28 of Corning, and there is the enhanced version SMF-28e. The mode field diameter is ≈ 9.2 μm at 1310 nm (effective mode area = 67 μm2), or 10.4 μm at 1550 nm (85 μm2). The single-mode cut-off is at 1260 nm. The Lucent AllWave and the Alcatel ColorLock fibers have quite similar properties.

Other telecom fibers have somewhat modified properties, making them more suitable in certain areas:

As glass fibers are not sufficient robust for directly laying them down in a building or even in the ground, they are often incorporated into optical fiber cables, where various polymer layers are sometimes even metallic armors provide additional protection. For flexible indoor use, fiber patch cables with standardized fiber connectors are suitable.

Standards for Telecom Fibers

The International Telecommunications Union (ITU) has developed a number of standards for various types of fibers as used for optical fiber communications. Some of the most important of those standards are listed in Table 1.

NameTitle
G.650.1 (06/04)Definitions and test methods for linear, deterministic attributes of single-mode fibre and cable
G.651 (02/98)Characteristics of a 50/125 μm multimode graded index optical fibre cable
G.651.1 (07/07)Characteristics of a 50/125 μm multimode graded index optical fibre cable for the optical access network (pre-published)
G.652 (06/05)Characteristics of a single-mode optical fibre and cable
G.653 (12/06)Characteristics of a dispersion-shifted single-mode optical fibre and cable
G.654 (12/06)Characteristics of a cut-off shifted single-mode optical fibre and cable
G.655 (03/06)Characteristics of a non-zero dispersion-shifted single-mode optical fibre and cable
G.656 (12/06)Characteristics of a fibre and cable with non-zero dispersion for wideband optical transport
G.657 (12/06)Characteristics of a bending loss insensitive single mode optical fibre and for the access network

Table 1: Important ITU standards concerning telecom fibers.

There are various other standards for telecom fibers, e.g. from ISO and IEC.

Relevant Properties of Telecom Fibers

Many different properties of a telecom fiber can be relevant for the achievable performance (partly depending on details of the used fiber-optic links) or concerning other aspects of use:

  • The propagation losses (fiber attenuation) in decibels per kilometer (dB/km) are particularly important for long-distance links. For single-mode fibers operated in the 1.5-μm spectral region, they are often of the order of only 0.2 dB/km. Multimode fibers typically exhibit somewhat higher values in the 1.5-μm region, and substantially higher attenuation is obtained for operation at short wavelengths.
  • The chromatic dispersion is particularly relevant for single mode fibers in long-distance systems. It is not necessarily best to have a group velocity dispersion (GVD) is small as possible; certain dispersion management techniques work best for fibers with substantial GVD. The spectral slope of GDD (related to higher-order dispersion, particularly TOD) can also be very important for high-bandwidth wavelength division multiplexing. The zero-dispersion wavelength is sometimes of particular interest.
  • The differential mode delay (DMD) of multimode fibers is often the limiting factor for the achievable bandwidth–distance product. Carefully designed and fabricated parabolic-index fibers (e.g. of the OM4 class) promised the best performance.
  • The strength of nonlinear effects in the fiber is determined by the effective mode area, which can differ quite substantially between different telecom fibers. It is often an important parameter in a system design.
  • For some applications, the sensitivity to bend losses is important. This is particularly the case for indoor installations, it may be impractical to avoid tight bending. A manufacturer may e.g. specify the induced macrobend loss in some wavelength range for a few turns of fiber wound up on a mandrel with given bend radius of e.g. 15 mm.
  • The core–clad concentricity can be important for the possible quality (in terms of transmission losses) of fusion splices.
  • Details of the protective coating, such is its outer diameter and chemical composition, can also be relevant in various ways, e.g. when mounting fiber connectors.
  • There can be various environmental specifications, e.g. concerning the allowed temperature range, allowed tensile stress and increased transmission losses caused by high temperatures or water immersion.
  • The available fiber length per spool (often many kilometers) may be limited.

Bibliography

[1]W. A. Gambling, “The rise and rise of optical fibers”, IEEE J. Sel. Top. Quantum Electron. 6 (6), 1084 (2000)
[2]Standards of the International Telecommunication Union (ITU), see http://www.itu.int/

(Suggest additional literature!)

See also: fibers, fiber cables, single-mode fibers, multimode fibers, graded-index fibers, fiber patch cables, silica fibers, optical fiber communications, modal bandwidth, bandwidth–distance product, bend losses
and other articles in the categories lightwave communications, fiber optics and waveguides

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