What are Optical Fiber and Fiber Optic Cable?

With the development of science and technology, the demand for large-scale communication construction is increasing. The fiber optic cable industry has developed rapidly and has formed a complete industrial chain from fiber preform, optical fiber, fiber optic cable, sensors, optoelectronics, and components.

Fiber Optic Cable Definition

To get clear what is fiber optic cable here starts from the fiber optic cable definition. Also known as optical fiber cable, fiber optic cable is a copper cable-like component that contains one or more optical fibers that used to carry light. Individually coated with plastic layers, the fiber optic components are contained in a protective tube suitable for the environment in which the cable will be deployed. With the different types, fiber optic cables are used for different applications, such as long-distance communication, or to provide high-speed data connections between different parts of a building.

Optical Fiber Structure

Optical fiber structureThe basic structure of optical fiber consists of three parts: the core, the cladding, and the coating or buffer. Light propagates mainly along the core which is a cylindrical rod of dielectric material that conducts no electricity. Generally made of glass, the core is surrounded by a layer of material called the cladding. Even though light will propagate along the fiber core without the layer of cladding material, the cladding does perform some necessary functions.

The cladding layer is made of a dielectric material. Generally made of glass or plastic, cladding performs the following functions: reducing the loss by returning of light back to the core, reducing scattering loss at the surface of the core, and preventing the core of fiber from absorbing surface contaminants.

 

Optical Fiber Types

Optical fiber types can be commonly divided into single mode and multimode optical fiber. With a diameter of 8.3 to 10 microns, single mode fiber is a single strand of glass fiber, which has one mode of transmission. Single mode fiber has a relatively narrower diameter, through which only one mode will propagate typically at 1310 or 1550nm. Although carrying higher bandwidth than multimode fiber, it requires a light source with a narrower spectral width. Multimode fiber has a little bit bigger diameter, with a common diameter in the 50-to-100 micron range for the core. Then how do we distinguish the single mode and multimode fibers?

Core diameter

The main difference between the multimode and single mode fibers is that the former has a larger diameter (usually the core diameter of the 50 or 62µm), and the typical single mode fiber has the core diameter of 8 and 10µm. The cladding diameter of both is 125µm.

 

A comparison of optical fiber core diameters
Figure: A comparison of optical fiber core diameters
Light source

Both lasers and LEDs are usually used as light sources. The laser source is much more expensive than the LED light source, because its light needs to be precisely controlled and has a higher power. The light produced by the LED light source is more dispersed (many modes of light), and these light sources are mostly used in multimode optical fiber jumpers.

Bandwidth

Because multimode fiber has a larger core size than single mode fiber, it supports multiple transmission modes. In addition, like multimode fiber, the single mode fiber also has mode dispersion caused by multiple spatial modes, but the mode dispersion of the single mode fiber is less than that of the multimode fiber. For these reasons, the single mode optical fiber has much higher bandwidth than the multimode optical fiber.

The color of the jacket

According to the TIA-598C standard, for nonmilitary purposes, single mode optical fiber adopts yellow outer jacket, and multimode optical fiber adopts orange or aqua outer jacket.

Mode dispersion

Multimode fiber has a higher pulse expansion rate than single mode fiber, which limits the information transmission capacity of multimode optical fiber.

Fiber Optic Cable Advantages and Disadvantages

As we all know, at present, the application of optical fiber in communication can be seen everywhere. So, what are the advantages and disadvantages of fiber optic cable?

Advantages of Optical Fiber Cable:
  • Greater Bandwidth – Besides with immunity to electromagnetic interference, fiber optic cables have much greater bandwidth and are much thinner and lighter than metal cables.
  • Larger Capacity – As the most secure medium available for carrying sensitive data, fiber optic cables have a larger capacity and greater tensile strength than copper.
  • Lower Power Loss – An optical fiber offers low power loss, which allows for longer transmission distances.
  • Lower Cost – The raw materials for glass are plentiful, unlike copper which means glass can be made more cheaply than copper.
Disadvantages of Optical Fiber Cable:
  • Difficult to Splice – The optical fibers are difficult to splice, and there is a loss of the light in the fiber due to scattering. They have a limited physical arc of cables.
  • High Price to Install – The optical fibers are more expensive to install, and they have to be installed by the specialists.
  • Can’t Be Curved – Besides, the fiber optic cables can’t be curved, because the fibers can be broken or have transmission losses when wrapped around curves of only a few centimeters radius.

Fiber optic cable has both advantages and disadvantages. However, in the long run, optical fiber will replace copper. Nowadays, widely used, fiber optic cable becomes more popular than before.

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Author: Far Li

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