Classification and standards of optical fibres

single-mode fiber and multimode fiber

Single-mode fiber and multimode fiber are the most common classification methods. Single-mode fiber is a * * *, multimode fiber is orange.

Single mode fiber is generally divided into: conventional single-mode fiber and dispersion-shifted fiber.

There are 3 common multimode fiber types:OM1,OM2 and OM3. OM1 multimode optical fibers are not included in ITU-T recommendations , but in practice The use of OM1 fibers is quite common.

Compared with single-mode fiber, multimode fiber has a much shorter transmission distance, but multimode fiber also has significant advantages.

1) multimode fiber core is thicker, manufacturing is relatively easy, so the cost is lower. For the user, the most immediate benefit is the low price.

2) because the core is thicker, the light enters the core more easily.

3) easy to weld.

4) Low requirement for light source. Multimode fibers are less directional to light and can use LED light sources, while single-mode optical fibers must use a well-directed laser to transmit data, requiring lasers as light sources.

classification by refractive index

The transmission distance of multimode optical fiber is much lower than that of unicast fiber because of the existence of die colors dispersion. The principle of modulus colors dispersion is similar to multipath fading in radio communication, and is the main factor affecting transmission distance. In order to reduce the effect of colors, it is necessary to adjust the transmission path of light in optical fiber, and to achieve this goal by changing the refractive index of the fiber core.

According to the refractive index of the core, the fiber can be divided into 2 categories, namely: Step index fiber and graded refractive index fiber. The refractive index of the whole fiber core of the step index fiber is consistent, and the propagation path of the light inside the core is a polyline. In the graded refractive index fiber, the refractive index of the core is reduced gradually, and the propagation path of the light inside the core is similar to a sinusoidal curve.

standard for fiber optics

Fiber standards include: itu-t g.651.1 g.652 g.653 g.654 g.655 g.656 g.657 g.651.1

Note:ITU-T 's G - header standard content is "transmission systems and media, digital systems and Networks".

specifications of optical fiber

The inner layer of the fiber is the core, which is used to transmit the optical signal, and the outer layer is a core cladding (cladding), and the specifications of the fiber are defined by these two layers. The specifications of the fiber are based on the ratio of the core diameter to the diameter of the fiber core cladding.

Type core diameter (micron) fiber core cladding Diameter (micron) mode
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50/125 50.0 125 Multimode
62.5/125 62.5 125 Multimode
100/125 100.0 125 Multimode
7/125 7.0 125.0 Single mode

This article from "Network Workshop" blog, declined reprint!

Classification and standards of optical fibres