The principle of optical fiber cable transmission
AddTime£º26-07-2016 Author£ºadmin
The transmission of fiber optic cable is based on the principle of the total reflection of the available light at the interface of the two media. Mutation type optical fiber, N1 is the core medium refraction rate, N2 is packet layer medium refractive index N1 is larger than N2, into the core of the light reach the fiber core and cladding interface (referred to as the core package interface) when the incident angle greater than total reflection critical angle theta C can occur total reflection without light energy underscored the culture core, incoming light can at the interface by countless times the total reflection of forward transmission.
Understanding of the optical fiber and cable transmission. Therefore, we should learned using optical fiber cable transmission need to pay attention to: when the fiber bending, interface normal steering, small angle of incidence, so part of the light incident angle become smaller than theta C and not a full reflection. But the original incidence angle of the larger light can still be reflected, so the fiber bending time can still be transmitted, but will cause the loss of energy. Usually, the bending radius is larger than 50 ~ 100 mm, and its loss is negligible. Minor bending will cause serious "micro bending loss".
Electromagnetic wave theory is used to study the transmission principle and mechanism of fiber optic cable, and the wave equation is solved by the boundary condition of the optical fiber media. The optical packets propagating in the optical fiber contain many modes, each representing a kind of electromagnetic field distribution, which corresponds to a ray of light in geometrical optics. Existing in fiber transmission modes depending on fiber normalized frequency v value formula: Na for numerical aperture, it and the core and the refraction of the dielectric layer rate. Alpha is the core radius, lambda is the wavelength. Fiber bending, occurrence mode coupling, a part of the energy transferred by conduction mode radiation mode, to the core loss.