A passive optical network (PON) is a fibre broadband network in which one fibre from the operator's exchange is split, by a small device that needs no electricity, to serve 32 or 64 homes. It is the most common way that fibre broadband, often sold as FTTH or fibre to the home, reaches Indian homes. The common versions are GPON and the faster XGS-PON.
A PON has three pieces. The first is the OLT, or optical line terminal. It is a shelf of equipment in the operator's local exchange, and each of its ports sends light down one fibre. The second is the splitter, a small box in the street or in a building's basement. It divides the light from one fibre into 32 or 64 fibres, one for each home. The splitter has no power supply and no electronics, which is why the network is called passive. So nothing in the street can fail when the power goes out. The third is the ONT, or optical network terminal, in each home. The ONT turns the light back into data. In most Indian homes, it is built into the home gateway that also runs the Wi-Fi.
All the homes on one splitter share the same fibre, so they must take turns. Downstream, from the exchange to the homes, the OLT sends everyone's data on the fibre, and each ONT keeps only the data meant for it. The data is encrypted, so no home can read its neighbour's. Upstream, from the homes to the exchange, the OLT gives each ONT short time slots in which to send, so that two homes never send at the same moment.
Consider a housing society in Noida with 64 flats on one splitter. The fibre uses GPON, which carries 2.5 gigabits a second downstream, shared by all 64 flats. If all of them downloaded at full speed at once, each would get about 39 megabits a second. But at any moment, most flats are idle or using little. So the operator can sell each flat a 100 megabits-a-second plan and still deliver it nearly all the time. If evening use grows too high, the operator moves the society to XGS-PON, which carries 10 gigabits a second, by changing the equipment at the two ends. The fibre and the splitter stay the same.
Behind the OLT, traffic joins the operator's optical transport network. The fibre in the street is ordinary optical fibre cable, with a reach of up to about 20 kilometres from the exchange. How does PON differ from fixed wireless access? PON needs a fibre to every home but is the fastest and most stable. FWA needs no cable, but it shares the radio of a mobile tower. The other options are described in fixed broadband access.