Working Principle of Fiber Optic Distribution Box

Fiber optic distribution box is used for the wiring connection of optical cable and optical communication equipment. By using adapters inside the distribution box, optical signals are led out by optical jumpers to achieve optical distribution. It is suitable for protective connection between optical cables and wiring tail fibers, and also for optical fiber terminal points in optical access networks.

What is a fiber optic distribution box?

The fiber optic distribution box is designed and manufactured according to the communication industry standard YD/T 778. It can complete functions such as introducing, fixing, and protecting optical cables, fusion splicing and protection of optical fibers, storage of tail fibers, storage and management of jumpers, fixed connection and cross-connection of optical fibers, etc. At the same time, it can install value-added module units such as optical splitters and wavelength division multiplexers according to customer requirements. Welink Technology is one well-known China fiber distribution box factory that specializes in the manufacturing of fiber-optic products, supplying trustworthy and top-notch solutions for multiple sectors.

The principle of the fiber optic distribution box

Principle of optical fiber:

Optical fiber is a kind of fiber made of glass or plastic, which can be used as an optical conduit. The transmission principle is "total internal reflection of light".

  • Light is an electromagnetic wave

The visible light wavelength range is: 390~760nm. The part larger than 760nm is infrared light, and the part smaller than 390nm is ultraviolet light. The three types of light applied in optical fibers are: 850nm, 1310nm, and 1550nm.

  • Refraction, reflection, and total internal reflection of light.

Because the propagation speed of light is different in different materials, when light is projected from one substance to another, refraction and reflection occur at the interface of the two substances. Moreover, the angle of refracted light will change as the angle of incident light changes. When the incident angle of light reaches or exceeds a certain angle, the refracted light disappears, and all the incident light is reflected back, which is total internal reflection of light. Different materials have different refractive angles for the same wavelength of light (i.e. different materials have different refractive indices), and the same material has different refractive angles for different wavelengths of light. Optical fiber communication is based on the above principles.

  • The bare fiber of the optical fiber is generally divided into three layers:

The high refractive index glass core (usually with a diameter of 50 or 62.5um) in the center, the low refractive index silicon glass cladding in the middle (usually with a diameter of 125um), and the outermost layer is the resin coating for reinforcement. The light travels through the fiber core. When the angle of incidence of the light on the interface between the fiber core and the outer layer is greater than the critical angle of total internal reflection, the light cannot pass through the interface and is completely reflected back, continuing to propagate forward in the fiber core, while the cladding mainly serves to protect it.

  • The optical fiber is composed of two layers of glass with different refractive indices

The inner layer is the optical fiber core, with a diameter of several microns to tens of microns, and the outer layer has a diameter of 0.1~0.2mm. Generally, the refractive index of the core glass is 1% higher than that of the outer layer glass. According to the principles of light refraction and total internal reflection, when the angle of the light beam projected onto the interface between the core and the outer layer is greater than the critical angle of total internal reflection, the light beam cannot pass through the interface and is completely reflected.

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