Salisbury's FTTH Blog

I had someone point out to me that I missed one important aspect of our network design in my post from this afternoon. I explained how the city had gone from using 32 way splitters to 16 way and how that change was going to allow the city to provide even higher bandwidth to our subscribers. But if you had paid really close attention, you would have noticed one interesting aspect of that discussion/

Earlier I explained what an OLT was and how one port, or connection, fed one splitter. This splitter could feed up to 32 homes/businesses if it was a 32 way splitter or 16 homes if it was a 16 way splitter. What maybe wasn’t quite as obvious is that this could lead to a much greater cost to the city.

Say we have 320 customers we want to sign up. If we use 32 way splitters, then we would need to use 10 ports on the OLT (again, each port can feed 32 homes/businesses). But if we use 16 way splitters, then we would need 20 ports. We haven’t bid out the GPON equipment yet so I can’t say what each port costs, but they are not inexpensive. So it would look like the 16 way splitters will almost double our costs. But what we are going to do is use 2 way splitters in the headend to feed two 16 way splitters in the field. This means we will effectively still be using 32 way splitters (one port on the OLT will feed a 2 way splitter that will then feed two 16 way splitters) in the beginning thus saving money. But once the number of subscribers grows or the demand for bandwidth increases, then we will be able to remove the 2way splitters. By this point we will have enough subscribers, and will be making enough money, to afford the costs of the extra OLT ports. This provides something similar to a “pay as you go (or grow)” plan.

I know this is more technical than most of you want to know, and I’ve tried to make it as easy to understand as I could. What I’m trying to show is that a lot of thought has gone into the design of the network and we’re trying to do this as inexpensively as we can. The network as it’s being built, can grow with the city and we can spread the cost over several years. Yet when we’re five or ten years into the project, the city will still have a state of the art network that will have the bandwidth the users want.

If you want to discuss this further, and I can’t believe anyone would, then let me know and I’ll do my best to confuse you even further. I’ll try not to make my next posts quite as boring.