On 13-02-01 22:52, Owen DeLong wrote:
Since the discussion here is about muni fiber capabilities and ideal greenfield plant designs, existing fiber is irrelevant to the discussion at hand.
Not so irrelevant. If the municipality wishes to attract as many competitive ISPs as possible, it wants to build a "standard" last mile that ISPs can easily interface to. One which is compatible with other FTTH systems. Currently, the standard is GPON (even though there are many variations to the theme). Sone may say that having L1 service with each ISP having their OLT with splitters at the CO is an advantage. It also means that each ISP has to have its own ONTs in homes and they can all choose different configs for OLTs and the light in the fibre. Greater flexibility to differentiate between ISPs. (one may choose RFoG for TV with DOCSIS for data while the other is an all data link with IPTV.) But for an end user, switching ISPs would mean switching the CPE equipment too since the ONT installed by ISP-1 may not be compatible with OLT used by ISP-2. Requiring an ISP to have its own OLT at the CO with its own splitter also raises startup costs and reduces the chances of having competitive ISP environment. Providing L2 service means that ISPs connect to a municipal OLT, so they do not have to purchase OLTs and bother with splitters. At that point, it si simpler and cheaper to deploy splitters in neighbouhoods. It also reduces number of splices. When you do 1:1, you may have a big cable with lots of strands leaving the CO, but you'll have a JWI in neighbouhood where you cross connect the strands from CO to the strand that uses the pre-fab cable to the backyards of homes served. So in all the calculations made on dB loss, the number of splices was not factored in. You're not going to get a continuous cable from the CO to the telephone pole behind a home. If you put the splitter at the CO you get the losses from the splitter, and then losses from a splice at the neighbouhood where trunk from CO connects to cables that runs through backyards. When you put the splitter in the neighbouhood, it performs both the splitting and the connection of the cable from CO to the backyards. So you eliminate one splice.