What are the differences between transfer boxes, distribution boxes, fiber distribution boxes, etc. in engineering?

According to the definition of YD/T 988-2015, the optical cable transfer box is an interface device used to connect trunk optical cables and distribution optical cables outdoors. Optical cable junction boxes are often referred to as "optical junctions" and are often installed indoors (such as basements). Depending on the location in the ODN, optical switching is divided into "backbone optical switching" and "distribution optical switching". In some provinces, in order to distinguish the backbone optical exchange and the distribution optical exchange, the backbone optical exchange is called optical exchange, and the distribution optical exchange is called optical distribution (optical cable distribution box).

1.1 Backbone optical communication

The trunk optical traffic usually does not have an optical splitter, and the cores of the trunk optical cable and the distribution optical cable are connected through single-core fiber jumpers.

However, in some metropolitan area networks, in order to facilitate the access of peripheral services to the backbone optical switch, optical cables are directly connected to the backbone optical switch, and a small number of optical splitters are placed in the junction box. Correspondingly, the backbone optical switch adopts A model that places a small number of optical splitters.

In some metropolitan area networks, the backbone optical switching adopts a jump-free method to reduce fiber link attenuation. The so-called "jump-free" refers to the way in which the upstream optical cable and the downstream optical cable are connected not through fiber jumpers, but through pigtails (including optical splitter pigtails).

1.2 Wiring optical crossover

The main function of the distribution optical switch is to realize the connection of "distribution optical cable → optical splitter → drop-in optical cable". In order to reduce the number of active connections in the optical fiber link, the distribution optical switch mainly adopts the jumper-free method.

Optical splitters are mainly divided into two types: box type and plug-in type. Depending on the type of splitter installed, wiring optical switches can also be divided into two types.

One uses a box-type optical splitter, and uses the pigtail of the optical splitter to connect uplink and downlink optical fiber links. The splitter is usually placed on the side of the junction box.

Or place it in the top area of the transfer box.

The other uses a plug-in optical splitter, which uses the pigtails of the upstream and downstream optical cables to connect the ports of the optical splitter.

Distribution optical switches used for co-construction and sharing mainly use plug-in optical splitters. As shown in the figure below, the upper part of the box is divided into 3 areas. Each area is divided into terminals for distribution optical cables from each operator and corresponding optical splitters are installed. The lower part of the box is for incoming optical cables to be terminated. Shared by multiple operators.

It is an interface device used to connect incoming optical cables and butterfly optical cables indoors, outdoors, and in corridors, or to connect vertical optical cables and horizontal optical cables in buildings. The optical fiber distribution box contains optical cable terminals, optical fiber splicing or mechanical splicing protection units.

Optical fiber distribution boxes are usually equipped with plug-in optical splitters.

Only a small number of fiber distribution boxes use box-type optical splitters.

When ODN adopts the first-level optical splitting method, no optical splitter is installed in the optical fiber distribution box, and the fiber core of the incoming optical cable is directly terminated. This method was often used in early FTTH construction, but it is now rare.

The multimedia box is also called a comprehensive wiring box for broadband access. It is a box used to install active communication equipment such as ONUs, optical (electrical) cable terminals and other supporting facilities outdoors or in corridors to provide a normal working environment for communication equipment. Multimedia boxes are mainly used for FTTB access methods.

The multi-functional wiring box installed in a household is the dividing point between outdoor and indoor weak current (communications, television) lines. The butterfly optical cable that enters the home in a shared community usually terminates here, so the user's ONT is often installed here.