GPON: 4‑Port Subscriber Enclosure

Good day, dear readers.

Today I'd like to start a short blog series on subscriber enclosures (distribution boxes or splice closures). As I mentioned earlier, subscriber connections are made in enclosures where the incoming cable is terminated with SC/APC connectors and matching adapters. So far, we've purchased enclosures from several suppliers, but there were only two design variants. Below, I've shown them in photos — with their contents, opened up, and with the splice tray removed and placed next to the lid. The rotating splice tray locks into place with a latch. In the open position, it provides easy access to the optical adapters.

Variant No. 1.

Variant No. 2.

Both variants side by side.

As you can see from the photos, the main difference between these enclosures is the splice tray design. In the second variant, it's much more convenient to work with, and there's space to install an optical splitter — which is quite important and desirable for GPON applications. I'd also note the more convenient holders for heat‑shrink splice protectors and their greater number. In the first variant, the protector size doesn't match the holders very well, and the splitter had to be placed in the bottom right corner of the box, squeezed between the adapter holder and the wall.

Overall, "Variant No. 2" gives a much better impression of a well‑made, user‑friendly product: the lid screw doesn't fall out when you open it, the key feels more solid, securing the central strength member is easier (a single screw), the adapter ports are numbered, the lid latches more securely, and a protective tube for the fibers is included.

As for drawbacks, I'd note the following for both enclosures: they can only be mounted to flat surfaces with screws — which makes pole mounting awkward. The seal for the subscriber cables is a single piece — when you need to add a new subscriber, you have to pull it out, feed the cable with the connector through, and re‑insert the seal over all the cables. It would be much easier if each entry had its own individual seal (or you could just cut this one into four pieces). I hope the manufacturers take note of these issues and update the design.

All in all, "Variant No. 2" suits us perfectly and has proven itself well in our passive optical network. It's also suitable for any FTTH application.

This article is a translation of the original Russian-language post.My journey of learning GPON