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What is an Optical Fiber Distribution Box?

Today, as the demand for higher data rates keeps increasing, optical fiber cables have been replaced with copper cables in FTTH(fiber to the home), FTTB(fiber to the building), and FTTC (fiber to the curb) networks. Optical fiber distribution boxes play a vital role in these wiring systems and thus are widely used in these cabling systems.

What is an optical fiber distribution box?

The optical fiber distribution box, also called the optical fiber distribution unit, optical fiber termination box, or optical fiber distribution point, is the intermediate node between the feeder cable of the distribution system and the bow-type drop cable leading to individual subscribers.

Figure 1: Feeder cable, drop cable, and fiber distribution box
Figure 1: Feeder cable, drop cable, and fiber distribution box

What’s the function of a fiber distribution box?

Used as a termination point, it links feeder cable to drop cable, integrating functions like fiber fixation, direct splicing, branching, straight-through, splitting, fiber termination, storage, solid protection, and better cable management in one unit; thus, it acts as a high-density fiber distribution box.

What’s the structure of the fiber distribution box?

Similar to ODFs, or fiber patch panels, fiber distribution boxes usually consist of appropriate space allowing for minimum bending radius, a bunch of fiber splice trays, fiber optic adapters, fiber optic splitters, fiber optic pigtails, several entrances, and exit ports, often made of PC-ABS materials with IP rating no less than IP65 and equipped with locking mechanism against theft or sabotage.

Typically, they’re lightweight and compact. The exit ports are much smaller than the entrance ports, as they’re used for connecting the pigtails or patch cords from the end-users.

Figure 2: structure of optic fiber distribution box
Figure 2: structure of optic fiber distribution box

FYI, PC-ABS is short for polycarbonate-ABS. It’s one of the most widely used industrial thermoplastics. It combines the superior strength and heat resistance of PC and the flexibility of ABS; thereby, it can fulfill the requirements of optical fiber systems. Meanwhile, its cost is moderate.

As for IP rating, refer to the IP code in Wikipedia. In short, it defines the level of protection offered by an enclosure against solids and liquids. IP65 rating means that it is protected from total dust ingress and protected against low-pressure jets of water from all directions, with limited ingress permitted.

Types of fiber distribution boxes

Fiber distribution boxes can be classified in terms of different standards. Generally speaking, we can divide them by mount type, cores, and integrity.

By mount type

There’re various mounting types of fiber distribution boxes. The most common mount type is the wall mount, while the pole mount is an alternative. The wall mount is preferred by FTTB, while FTTC prefers the pole mount.

By exit ports

According to the number of exit ports a fiber distribution box contains, we can name it as the corresponding cores distribution box, for instance, a fiber distribution box having 8 exit ports can be called as an 8-core distribution box. There’re 2-,4-,6-,8-,12-,16-,24-,36-,48-core and more distribution boxes. Among them, the 8- and 16-core types are the most common.

Loaded version versus unloaded version

A loaded fiber distribution box means a fiber distribution box is equipped with either a full set of accessories, including fiber pigtails, splitters, splice trays, and adapters, namely a full-loaded version, or just several of them.

Figure 3: loaded fiber distribution box
Figure 3: loaded fiber distribution box

The unloaded version indicates a bare chassis without these accessories described previously.

Figure 4: unloader fiber distribution box
Figure 4: unloader fiber distribution box

Each version has its advantages and disadvantages.

Firstly, let’s talk about their respective cost of them. The loaded version costs less, as a fiber distribution box with preinstalled accessories comes at a lower price than an unloaded fiber distribution box because all the accessories you have to buy one by one.

Secondly, let’s talk about their respective cost-effectiveness of them. The loaded version offers better performance, as the quality of factory-preinstalled accessories is guaranteed. Meanwhile, a loaded version spares your installation cost, as you needn’t spend time and labor to DIY. Furthermore, the performance test process is no more necessary. However, if any adapter’s port gets damaged, it’s dead forever. As these adapters’ ports are fixed, you can’t swap the defective port out for a new one. Thus it’s better to leave it alone other than replace the whole unit with a new one. Another point to consider, sometimes, you may want to upgrade your configuration of the fiber distribution box. In this case, the whole unit of the fiber distribution box has to be replaced.

In contrast, the unloaded version offers the best adaptability since it’s up to you to arrange all accessories as required. For instance, you may not be content with the configuration of the loaded version. Perhaps your specific project may not need splice trays because you plan to take the connector approach termination instead of using splice trays for fusion splicing with fiber pigtails. However, the DIY version may or may not affect the performance of these accessories, depending on whether you have enough technique and careful attention.

How to choose a fiber distribution box?

When you want to select one fiber distribution box, you’d better consider all the features mentioned above to find the most appropriate one.

You have to determine three things beforehand, i.e., the capacity of the fiber distribution box based on your projects, like an 8-core distribution box, the placement you want to deploy it, wall mount or pole mount, and finally, a loaded or unloaded version to buy.

What’s the difference between ODF (optical distribution frame), OFPP (optical fiber patch panel), and OFDB (optical fiber distribution box)?

I recently came across this question, as they are much alike in functions, sometimes even appearance. I observed there’re lots of guys also get confused by the relationship between these three pieces of equipment. Therefore, I want to talk a little about this question.

First, let’s summarize their similarities.

Figure 5: typical cabinet ODF
Figure 5: typical cabinet ODF

Similarities between ODF, OFPP, OFDB

Generally speaking, most of the functions they provide are similar, listed as below:

  • Termination: fusion splicing/mechanical splicing with fiber pigtails or a fiber connector approach.
  • Splitter, splitting an optical signal into more parts to branch.
  • Appropriate space for storage of excess patch cables or pigtails allows for minimum bending radius.
  • Protection of splice joints, adapters, and other components.
  • Better cable management.

Given the strong likeness between them, no wonder people mix them up with each other.

As we’re more concerned with the differences between ODF, OFPP, and OFDB, thus we’ll go into the distinctions between them.

Figure 6: typical 1U Rack Mount fiber patch panel
Figure 6: typical 1U Rack Mount fiber patch panel

Differences between ODF, OFPP, OFDB

Concisely, there’re two important aspects used for differentiating them. One is the usage environment, and one is the dimensions.

usage environment

Besides a considerable overlap of usage environments, ODFs are typically used in high-density cabling systems like data centers, service rooms, etc. Optical fiber patch panels are often used in intra-building wiring systems, typically used for LAN applications. OFDBs are often used in FTTH and FTTB networking systems to provide the local loop used for last mile telecommunications.


With some exceptions, ODFs are the biggest among them, and it even houses patch panels as accessories within it, while it’s hard to compare the last two pieces of equipment, as they all have lots of varieties of shape and sizes. The bigger the size, the larger the number of ports.

Figure 7: typical fiber distribution box
Figure 7: typical fiber distribution box


So, this is it. We’ve introduced the basics of the fiber distribution box, and it would be helpful for you to choose the best appropriate one. In addition, if you still have some questions about the fiber distribution box, feel free to leave a comment.

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