The working principle of optical fiber is: total reflection of light .
Causes of dispersion:
In an optical fiber, an optical signal is composed of many different components. Due to the different propagation speeds of each frequency component or mode component of the signal, after a certain distance through the optical fiber, there will be a time delay difference between different components, causing the transmission signal waveform Distortion, pulse broadening, this phenomenon is called fiber dispersion.
The effect of dispersion:
The existence of optical fiber dispersion distorts and broadens the transmitted signal pulse, resulting in intersymbol interference. In order to ensure the quality of communication, it is necessary to increase the inter-symbol interval, that is, to reduce the transmission rate of the signal, which limits the communication capacity and transmission distance of the optical fiber system.
Classification of dispersion:
According to the cause of dispersion, fiber dispersion can be divided into mode dispersion, material dispersion, waveguide dispersion and polarization dispersion.
The loss of optical fiber refers to the reduction of optical power due to absorption, scattering and other reasons after the optical signal is transmitted through the optical fiber.
scattering loss. Linear Scattering; Nonlinear Scattering; Structure Imperfect Scattering.
Other attenuation: microbending attenuation, etc. Optical fiber is soft and can be bent, but after bending to a certain extent, although the optical fiber can guide light, it will change the transmission path of light. The transmission mode is converted to the radiation mode, so that a part of the light energy penetrates into the cladding or passes through the cladding to become a radiation mode and leaks outward, resulting in loss. When the bending radius is larger than 5-10cm, the loss caused by bending can be neglected.
