The basic principle of optical fiber cable

optical fiber transmission based on the available light on the surface of two kinds of medium, the principle of total reflection. Step-index fiber, n1 is the refractive index of fiber core medium, n2 for the refractive index of cladding medium, n1 is greater than the n2, the arrival of light entering the fiber core fiber core and cladding interface ( Referred to as 'core - Package interface) When the incident Angle is greater than the total reflection of critical Angle theta, c is total reflection can happen without light energy high fiber core, the incident light can forward by countless times total reflection at the interface between the transmission.

when optical fiber bending, original interface normal turned, the incident Angle is small, being part of the light of the incident Angle less than theta c but not total reflection. But the original incident Angle is bigger that light can still be total reflection, so the fiber bending moments can still transfer, but will cause energy loss. Usually, the bending radius is larger than 50 ~ 100 mm, the loss can be neglected. Tiny bending will cause serious 'microbend losses'.

people commonly used electromagnetic wave theory of further research on optical fiber transmission mechanism, the optical dielectric waveguide boundary conditions to solve the wave equation. Transmission of light in the optical fiber contains many patterns, each pattern represents a kind of electromagnetic field distribution, and the one described in geometrical optics correspond to the light. Existing in the optical fiber transmission mode depends on the normalized frequency argument value of the optical fiber. Formula:

type in NA as numerical aperture, it related to the refractive index of fiber core and cladding medium. ɑ as the fiber core radius, lambda is the wavelength of light transmission. Optical fiber bending, mode coupling, part of the energy transmission mode to radiation mode, outside to the fiber core loss. Performance: the main parameters of optical fiber attenuation, bandwidth, etc.