PON technology – what is it and why is it needed?

Fiber optic, which used to be the domain of providers and large companies, is slowly becoming available to ordinary users. “Optics” in apartments and private houses appeared thanks to PON technology, which made it possible to reduce the cost of connection to values ​​acceptable for a private consumer. What is this technology?

What is PON
PON (Passive Optical Network) is a fiber optic network that uses inexpensive passive splitters to deliver traffic to the end (terminal) client.

They do not require power supply, complicated set-up, heated cabinets, etc.

This is the main difference from active networks, where traffic is redistributed to clients through an active device – a router.

This solution made it possible to significantly reduce the cost of laying a fiber-optic network. The low cost of splitters allows them to be installed on the backbone near each client, making the network topology closer to the bus with its minimum cable consumption.

Compared to the classic “star”, the cost of the cable is significantly reduced. This is especially noticeable when clients are not “clustered” in a small space, but are separated from each other by several tens of meters.

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Most often, it is the PON technology that should be thanked to the residents of cottage settlements for the fast Internet. And not only the Internet – the transmission channel in PON networks is divided into three ranges: reception – with a wavelength of 1490 nm, transmission – 1310 nm, and television – 1550 nm. Therefore, the provider usually provides IPTV along with the Internet.

Alas, nothing good comes for free. You have to pay for a low price:

A breakdown of the subscriber terminal can lead to the “fall” of the entire subnet: if the client’s transmitter starts to “light up” the line, this will lead to the loss of communication for the rest of the clients. In a similar situation with the AON network, nothing would have changed for other clients. PONs are less reliable and have more frequent disconnects.
PON networks are more vulnerable: each device on a subnet actually receives all of its traffic, including packets not intended for this device. Usually they are encrypted, however, the technology increases the risk of hacking “someone else’s” traffic.
Since the light signal in the splitter is simply divided without amplification, its power decreases with each division. Therefore, the size of PON networks is limited: a maximum of 128 subscriber devices (ONT / ONU – Optical Network Terminal / Optical Network Unit) are allowed per optical terminal (OLT – Optical Line Terminal).

At full load (128 active users), the real speed for “optics” is low – a maximum of 20 Mbps. However, for those who have rarely seen more than 2 Mbps via a 3G modem before, these values ​​may seem exorbitant. At least that’s enough for watching 4K video without stuttering. And when the load decreases, the minus turns into a plus: due to the fact that the splitters cannot be configured in any way, the provider cannot limit the channel width for each specific subscriber. And if only one client remains in the subnet of one OLT, the speed will increase to the maximum for the subscriber port – 1 Gbps. True, usually inexpensive standard client equipment is not designed for such speeds and rarely produces more than 350 Mbps, but you can easily replace it with your own – higher speed.

Subscriber GPON gateway Tenda G103
PON varieties
The first PON standards – APON and BPON – are practically not used today. Ten-gigabit 10G xPON networks are still poorly distributed, so for now the choice can only be between two standards – GPON and GEPON (EPON). The first is more modern and faster, but the equipment is more expensive for it.

End users usually don’t notice much of a difference between these standards. The speed is much more influenced by the loading of subnets, and differences in the composition of packets or, for example, the possibility of transmitting TDMA traffic for an ordinary user are unimportant and uninteresting.

In the future, GPON and GEPON networks will be replaced by ten-gigabit analogs – 10G-PON and 10G-EPON. These standards were developed already 10 years ago, but their ubiquity is hindered by two factors:

The mass user just doesn’t need such speeds yet.
10G-xPON networks use the same cable infrastructure as xPON. This undoubted plus of the technology, oddly enough, hinders the introduction of new standards – providers are in no hurry to buy expensive 10G equipment, hoping to switch to it later when it becomes necessary, because the technology allows such an “upgrade”.
Output

PON is a fiber-optic networking technology that has made the Internet more accessible to the general public. It is capable of delivering from 20 Mbps to 1 Gbps per client device. The characteristics make xPON-networks quite competitive in the urban environment, and outside the city PON, despite its disadvantages, may even be the only technology capable of providing “fast” Internet for everyone.