Optical fiber transmission based on the principle of total reflection in the interface between two kinds of available light. The mutant fiber, N1 fiber core refractive medium refractive index cladding rate, N2 medium rate, N1 is greater than N2, into the core of the light reaching the core and cladding interface (the core packet interface) when the incident angle is greater than the critical angle of total reflection C, total reflection can occur without light energy through the core, the incident light can be through countless times of total reflection at the interface of forward transmission. Original

When the fiber is bent, the interface is normal and the angle of incidence is small, so that the incident angle of a part of the light is less than C and cannot be reflected completely. However, the incident angle of the larger light can still total reflection, so the fiber bending time can still be transmitted, but will cause energy loss. Generally, when the bending radius is greater than 50 ~ 100 mm, the loss can be neglected. The small bending will cause severe micro bending loss.

The theory of electromagnetic wave is used to study the mechanism of optical fiber transmission. The optical packet propagating in the optical fiber contains a number of modes, each of which represents an electromagnetic field distribution and corresponds to a certain light described in geometric optics. The mode of transmission in the optical fiber is determined by the NA in the normalized frequency value of the fiber, which is related to the refractive index of the core and the cladding medium. Alpha is the core radius, as the wavelength of the light transmission. Fiber bending, occurrence mode coupling, a part of the energy transferred by conduction mode radiation mode, to the core loss.

Performance: the main parameters of optical fiber attenuation, bandwidth, etc..