Our understanding of fiber optic cables is not enough. There are many aspects of technology that have yet to be developed. As a communication cable, fiber optic cables consist of two or more glass or plastic fiber optic cores. These fiber optic cores are located in a protective cladding. inside, covered by a plastic PVC outer sleeve. Signal transmission along the internal optical fiber generally uses infrared rays. Let's take a look at the transmission distance and principle of single-mode optical fiber.
As the competition in the optical fiber and cable industry continues to intensify, mergers and acquisitions and capital operations among large optical fiber and cable enterprises are becoming more and more frequent, and domestic excellent optical fiber and cable manufacturers are paying more and more attention to the research on the industry market, especially the development environment of enterprises and customer demand trends. An in-depth study of change. Because of this, a large number of domestic excellent optical fiber and cable brands have risen rapidly and gradually become leaders in the optical fiber and cable industry!
Fiber transmission rate
So what is the basic principle of optical fiber transmission, we have made the following analysis:
Optical fiber transmission is based on the principle of total reflection of available light at the interface of two media. Mutant fiber, n1 is the refractive index of the core medium, n2 is the refractive index of the cladding medium, n1 is greater than n2, the incident angle when the light entering the core reaches the interface between the core and the cladding (referred to as the core-cladding interface) When it is greater than the critical angle θc of total reflection, total reflection can occur without light energy passing through the core, and the incident light can be transmitted forward at the interface through numerous total reflections.
It turns out that when the fiber is bent, the interface normal is turned and the incident angle is small, so the incident angle of a part of the light becomes smaller than θc and cannot be totally reflected. However, those rays with a larger incident angle can still be totally reflected, so the light can still be transmitted when the fiber is bent, but it will cause energy loss. Generally, when the bending radius is greater than 50-100 mm, the loss can be ignored. Small bends will cause severe "microbend losses".
People often use electromagnetic wave theory to further study the mechanism of optical fiber transmission, and solve the wave equation by the boundary conditions of optical fiber medium waveguide. Light propagating in an optical fiber contains many modes, each of which represents an electromagnetic field distribution and corresponds to a certain ray described in geometrical optics. The conduction modes present in the fiber depend on the normalized frequency ν value of the fiber.
where NA is the numerical aperture, which is related to the refractive index of the core and cladding medium. ɑ is the core radius and λ is the wavelength of the transmitted light. When the fiber is bent, mode coupling occurs, and a part of the energy is transferred from the conduction mode to the radiation mode, which is transmitted to the outside of the core and lost.
