Gigabit-Capable Passive Optical Network

Gigabit-capable Passive Optical Network or also known as GPON as one of the optical technologies for telecommunication. This technology allows data communication between the headend and client with a speed of minimum 1 Gbps. According to ITU, GPON can have a coverage of at least 20 km and 60 km with a logical reach. It can also support various bitrate optios such as symmetrical 622 Mbps, symmetrical 1.25 Gbps, and 2.5 Gbps downstream – 1.25 Gbps upstream using the same protocol.

Picture taken from: http://www.fttxtra.com/ftth/gpon/extending-gpons-reach/

One of the reasons why a telco company implements this technology is because of the speed they can get with a long distance. This is the advantage than using LAN which can only have a switch/router with a coverage of 100 meters only. By using GPON, the system needs only to have 1 OLT (typically 4 or 8 ports), a splitter and ONT units. Of course the business model for this system is for corporate or high rise buildings. It is not feasible to put this technology in the residential area because of the high cost (except combined with other technology). Typically one ONT can be installed into a router or switch to cover a smaller area of coverage such as a floor in a building or a cluster of houses, or into another smaller ISP.

As said above, the basic system of GPON consists of OLT, Splitter and ONT. OLT is the headend of the system. ONT is installed on the client and is a passive unit. It works just as a hub. The splitter is used to split one core into many lines and is a passive unit. This is used when multiple ONTs needs to be connected to only a single port. There are currently a 1:2, 1:4, 1:8, 1:16, 1:32, 1:64 and even 1:128 splitter. If a 1 Gbps link (OLT-splitter link) is splitted to 4 customers using a 1:4 splitter, than each link (splitter-ONT link) of the users are 0.25 Gbps (assuming evenly distributed).

I hope this short blog can make you aware of the basic GPON technology.