定义：
用于光纤通信中的光纤。

通信光纤是指用于光纤通信中的光纤。主要采用下面几种类型的通信光纤： 

• 熔融二氧化硅单模光纤，由于其损耗很低（0.2 dB/km）而通常用于长距离（几百千米）高数据容量的数据传输。 
• 熔融二氧化硅多模光纤则同于短距离传输，例如几百米：由于具有很大的纤芯面积，所以它们易于处理，但是模间色散限制了传输距离。 
• 塑料光纤（通常为多模），通常采用PMMA（聚甲基丙烯酸酯，也被称为有机玻璃）制成，这在短程数据传输中，例如家庭局域网，是最便宜的材料。 

典型的1300nm或者1500nm单模通信光纤为Corning公司的SMF-28，还有增强的型号为SMF-28e。模场直径在1310nm时约为9.2微米（有效模式面积为67平方微米），在1550nm时为10.4微米（85平方微米）。单模截止波长为1260nm。Lucent AllWave和Alcatel ColorLock公司的光纤具有类似的性质。 
另外的一些通信光纤对某些性质进行了改进，因此更适于应用到特定领域： 

• Corning提供了不同型号的Vascade光纤，例如Vascade L1000具有更大的有效模式面积，Vascade LS+则具有非零色散位移，Vascade LEAF光纤则是具有更大模式面积的色散位移光纤。 
• Lucent则提供了不同型号的TrueWave光纤，例如，TureWave-RS的色散斜率变小，而TrueWave-XL则具有更大的模式面积。 
• Alcatel则发展TeraLight光纤，这是另一种非零色散的光纤。（Alcatel后来与Lucent公司合并组成Alcatel-Lucent公司） 

由于玻璃光纤不够坚固因而不能直接放在楼中或者地上，所以需要被放在光缆中，需要不同的聚合物层甚至金属外壳对其进行额外的保护。而如果应用到室内时，接插电缆只需采用标准的光纤连接器。 

国际电信联盟标准要求的通信光纤 
国际电信联盟（ITU）对于应用到光纤通信中的不同种类的光纤制定了一些标准。一些最重要的标准如表1所示。 

表1：对通信光纤的重要ITU标准 

Definition: optical fibers for use in optical fiber communications

Alternative term: telecommunication fibers

Telecom fibers are optical fibers which are used in optical fiber communications. This is a huge application field for fibers; several hundred millions of kilometers of telecom fibers are currently fabricated per year.

Mainly the following types of telecom fibers are used:

• Fused silica single-mode fibers with very low propagation losses (e.g. 0.2 dB/km) are used for long-haul data transmission (tens or hundreds of kilometers) with very high transmission capacity. Those which are suitable for high data rates are often spun fibers, exhibiting much reduced polarization mode dispersion.
• Fused silica multimode fibers, often in the form of graded-index fibers, are suitable for shorter distances of e.g. hundreds of meters (e.g. within storage area networks): they are less critical to handle, essentially due to much larger core areas, but intermodal dispersion limits the transmission distance.
• Few-mode fibers are optimized for mode division multiplexing, i.e., for transmission of multiple signal channels through different fiber modes.
• Plastic optical fibers (usually multimode), typically made of PMMA (polymethyl methacrylate, also called acrylic), represent the cheapest solution for short-range data transmission, e.g. in home networks.

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:

• Corning offers Vascade fibers in different versions, e.g. the Vascade L1000 with an increased effective mode area, the non-zero dispersion-shifted Vascade LS+, and the Vascade LEAF fiber, a dispersion-shifted fiber with increased mode area.
• Lucent offers different versions of their TrueWave fiber, e.g. the TrueWave-RS with reduced dispersion slope and the TrueWave-XL with larger mode area.
• Alcatel developed the TeraLight fiber, another non-zero dispersion-shifted fiber. (Alcatel has later merged with Lucent to form the company Alcatel-Lucent.)

As glass fibers are not sufficient robust for directly laying them down in a building or even in the ground, they are incorporated into optical fiber cables, where various polymer layers and 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.

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. (See also the article on dispersion-shifted fibers.)
• For multimode fibers, the differential mode delay (DMD) is often the limiting factor for the achievable bandwidth–distance product. Carefully designed and fabricated parabolic-index fibers (e.g. of the OM4 class) promise the best performance.
• The strength of nonlinear effects in the fiber is mainly determined by the effective mode area, which can differ quite substantially between different telecom fibers, and less by the chemical composition of the fiber core. 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 fiber coating, such as its outer diameter and chemical composition, can also be relevant in various ways, e.g. when mounting fiber connectors or concerning temperature resistance.
• 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. However, telecom fibers are mostly drawn from large preforms, each one delivering many kilometers of fiber.

Bibliography