Basic knowledge of the optical fiber

three layers structure of optical fiber:

(1) center high refractive index glass core Core diameter for 9 - commonly 10μm,( Single mode) 50 or 62. 5 ( Multimode) 。 The refractive index is higher, used to transmit light;

(2) the second layer, middle to low refractive index of silicon glass cladding ( Is 125 microns in diameter) 。 Refractive index is low, and the fiber core together to form the total reflection condition;

3. The outside is to strengthen with the resin coating. Strength is big, can bear bigger impact, protect the 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 classification: 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

size:

single mode fiber core diameter: 9/125 microns, 10/125 (microns cladding diameter 2 d) = 125 microns

a = 250 microns tail fiber coating diameter: 300 mu m

multimode fiber core diameter: 50/125 microns, European standard 62. 5/125 microns, American standard

industrial, medical and low-speed network: 100/140 microns, 200/230 mu m

plastic: 98/1000 microns, used in automobile control

fiber attenuation

fiber attenuation of the main factors are: intrinsic, bending, extrusion, impurities, uneven docking, etc.

eigen: is the inherent of the fiber loss, including: Rayleigh scattering, intrinsic absorption, etc. Bending:

fiber bending part inside of the light will be scattered and lost, caused by the wear and tear.

extrusion: fiber squeeze produced in small bending caused by the loss. :

impurities inside the fiber impurity absorption and scattering in optical fiber transmission of light, caused by the loss.

uneven: the loss caused by the uneven refractive index of optical materials.

docking: fiber butt when the loss, such as: no coaxial ( Single-mode fiber coaxial degree requirements less than 0. 8μm) , end face and the axis is not perpendicular to the face, heart size does not match the docking and poor welding quality.