The transmission of fiber optic cable is based on the principle that available light is totally reflected at the interface between two media. Catastrophic 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 angle of incidence of the light entering the core when it reaches the interface between the core and the cladding (referred to as the core-clad interface) When it is greater than the critical angle of total reflection θc, total reflection can occur without light energy passing through the core, and incident light can be transmitted forward at the interface through countless total reflections.
Understands the transmission of fiber optic cable, so we should understand that when using fiber optic cable transmission, we need to pay attention: when the fiber is bent, the interface normal turns and the angle of incidence is small, so the angle of incidence of some light rays becomes less than θc and cannot be fully reflected. However, those rays with a large 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 is negligible. Tiny bending will cause serious “microbending loss”.
People often use electromagnetic wave theory to further study the transmission principles and mechanisms of fiber optic cables, and use the boundary conditions of fiber dielectric waveguides to solve wave equations. The light propagating in the optical fiber contains many modes, and each mode represents an electromagnetic field distribution, and corresponds to a certain ray described in geometric optics. The conduction mode present in the fiber depends on the normalized frequency ν value of the fiber. Formula: 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 transmitted light. When the optical fiber is bent, mode coupling occurs, and part of the energy is transferred from the conduction mode to the radiation mode, and is lost outside the core.
Optical fiber cable is the most promising medium in the communications industry. For newcomers, they should learn more about their basic knowledge. In this article, we will talk about the basic knowledge of fiber optic cable, I hope to help you just started.
Fiber optic cable is mainly divided into two categories: Single-mode fiber: general fiber optic cable jumper is indicated by yellow, the connector and protective sleeve are blue; the transmission distance is longer. Multimode fiber: Generally, the fiber jumper is shown in orange, and some is shown in gray. The connectors and protective sleeves are beige or black; the transmission distance is short. Attention to the use of optical fiber! The transmission and reception wavelengths of the optical modules at both ends of the fiber optic cable jumper must be the same, that is to say, the two ends of the optical fiber must be the optical modules of the same wavelength. The simple method of distinguishing is the color of the optical module. In general, short-wave optical modules use multimode optical fibers (orange optical fibers), and long-wave optical modules use single-mode optical fibers (yellow optical fibers) to ensure the accuracy of data transmission. Do not excessively bend or loop the fiber during use, as this will increase the attenuation of light during transmission. After using the fiber jumper, be sure to protect the fiber connector with a protective sleeve. Dust and oil will damage the coupling of the fiber optic cable.
Post time: Jul-12-2021