1. Propagation of light in optical fibers
For step-index fibers, due to the obvious boundary between the core and cladding refractive index distributions, the light waves from a total reflection at the interface
between the core and the cladding interface, and form a zigzag transmission path, guiding the fiber core to propagate forward…
For the graded-index fiber, since the refractive index is continuously changed at the interface, the refractive index at the center of the shaft is the largest, the refractive index
decreases along the radius of the core in a parabolic law, and the refractive index at the edge of the core is the smallest, so the light wave is Continuous refraction occurs in the
core, forming a refracting line similar to a sinusoidal wave passing through the axis of the fiber, directing the light wave to propagate forward along the core.
2. Loss and dispersion are the two most important transmission characteristics of optical fibers, which directly affect the performance of the optical transmission.
(1) Optical fiber transmission loss: Loss is one of the important factors affecting the transmission distance of the system. The loss of the optical fiber itself mainly
includes absorption loss and scattering loss.
Absorption loss is due to the fact that part of the light energy is converted into heat energy during transmission.
Scattering loss is caused by the uneven or defective refractive index of the material, distortion or roughness of the surface of the fiber.
Of course, there are some losses in the fiber-optic communication system that are not due to the fiber itself, including connection loss, bending loss, and microbend
loss. TThe magnitude of these losses will directly affect the length of the fiber transmission distance and the choice of relay distance.
(2) Optical fiber transmission dispersion: Dispersion is the time spread of the optical pulse signal transmitted in the optical fiber and reaching the output end.
The cause is the different frequency components of the optical pulse signal, different modes, and the waveform distortion caused by the different time at the end of the
transmission due to the different speeds.
Dispersion results: This distortion causes communication quality to degrade, thereby limiting communication capacity and transmission distance.
Disclaimer: All information indicated as other sources is transferred from other platforms, the purpose is to convey more information, does not represent the views and
positions of this site. Please contact us if there is any infringement or objection.