You often come across posts online about pretty strict requirements for splice and connector quality in PON networks. Some say you need specialized fusion splicers, others insist that every single joint should be checked with an OTDR right away. Since our company also runs a cable TV operation — where optical losses are quite critical — we've made it a rule from day one to keep splice loss below 0.03 dB per the splicer's reading.
That said, the splicer's loss estimate is only an approximation. Real-world measurements often give different numbers. So we also visually inspect every splice as it's being made. A bad splice is usually obvious right away — you'll see dark spots or black dots, which are air bubbles. The splicer doesn't always catch these properly, so it's better to play it safe and re‑splice any suspicious spot.
One thing to keep in mind: you're far more likely to run into high loss at a connector (through an adapter) than at a fusion splice. A single bad connector can ruin all your perfect splices along the line. I should also mention that the quality of pigtails and patch cords you buy these days is pretty hit‑or‑miss. I haven't found any real correlation between price and quality, or even between brands. Most of the time it's acceptable, but there's always an element of luck involved.
The big question during construction was how to connect the splitters into the line: should we splice them directly in, or use adapters (optical outlets)? With the first approach, we reduce loss by minimizing the number of connectorized joints. With the second, we gain flexibility — we can reconfigure or replace splitters to redirect power as needed, without having to do any extra work on the fiber itself. But it's hard to anticipate every possible distribution scenario, and this setup really only works well for bus‑type connections. Adding a subscriber at the far end, for example, would mean replacing every splitter along the line — and so on. There are so many nuances that it's tough to make the right strategic call. So in most cases, you simply can't avoid fusion splicing.
In our case, we could have done everything with splices, since we designed for 100% take‑rate and don't expect any changes to the signal distribution. But as I mentioned earlier, subscriber connections will be done using pre‑made patch cords — so using an outlet at the final drop is a must. The splitter itself is spliced to the incoming fiber on its input side. For the top‑level splitter — the one that divides the signal into major directions — we decided to go fully connectorized.
I'll explain why in the next post.
This article is a translation of the original Russian-language post.My journey of learning GPON