The basic knowledge of optical fiber

the classification of the fiber

according to the material classification:

glass fiber, glass fiber core and cladding are, low dissipation factor, long transmission distance, high cost;

rubber set of silica fiber, fiber core is glass, the cladding for plastic, features with glass fiber, lower cost;

plastic optical fiber, fiber core and cladding are plastic, the loss is big, the transmission distance is short, the price is very low. Used in home appliances, audio, and image transmission of short distance.

according to the optimal transmission frequency window: conventional single-mode fiber and dispersion-shifted single-mode fiber.

the conventional type: fiber production house will be optical fiber transmission frequency optimization on a single wavelength of light, such as 1300 nm.

dispersion-shifted type: fiber production house will be optical fiber transmission frequency optimization on two wavelengths of light, such as: 1300 nm and 1550 nm.

fiber type

according to the light in the optical fiber transmission mode can be divided into:

multimode ( 多 模式) ( Hereinafter referred to as: MM)

single mode ( 单 模式) ( Hereinafter referred to as: SM)

multimode optical fiber: center glass core coarser ( 50 or 62. 5μm) , the light can pass various patterns. But its mode dispersion is bigger, this limits the transmission of digital signal frequency, and with the increase of the distance will be more serious. For example: 600 MB/KM optical fiber in 2 KM, only 300 MB bandwidth. Therefore, the multimode optical fiber transmission distance is near, usually only a few kilometers.

single-mode fiber: center glass core is fine, Core diameter is commonly 9 or 10 microns) , only the light of a pattern. Is actually step type optical fiber, is a fiber core diameter is very small, in theory allows only a single route of transmission of straight into the light incident to the optical fiber, and make linear propagation in the fiber core. Almost no broadening optical pulse. Therefore, dispersion between the mould is very small, for remote communications, but its chromatic dispersion plays a main role, so single-mode fiber have higher request for the spectral width and stability of light source, the spectral width is narrow, the stability is better.

mutant: optical center core to the refractive index of glass cladding is mutation. Its low cost, high modulus between the dispersion. Suitable for short-distance communication at low speed, such as industrial control. But dispersion between single-mode fiber due to mould is very small, so the step-index single-mode fiber are adopted.

graded-index optical fiber, optical fiber core center to the refractive index of glass cladding is gradually become smaller, can make the anti-embrittlement light transmission, the form of the sine dispersion between this can reduce the mold, improve optical fiber bandwidth and increase transmission distance, but the cost is higher, the multimode optical fiber for the gradient type optical fiber.