HOW POINT-TO-POINT AND PASSIVE OPTICAL FIBER NETWORKS ARE DIFFERENT

Every broadband installer should know about the different types of fiber networks. The two main ones are: point-to-point and passive optical network (PON).

 

Think of how a phone call works and you’ll get the gist of a point-to-point network. There’s a direct connection between two phones, or nodes, and the other phone only hears the call.

 

A PON, in contrast, is a point-to-multipoint network where a signal is shared.

 

In the case of fiber optic networks, the point-to-point architecture would involve a switch at the central office of the Internet Service Provider (ISP) connected by multi-fiber cable to an aggregation switch in a cabinet on the street.

 

These switches have multiple optical ports – each of which is connected by fiber to an optical network termination or ONT in an enclosure somewhere on or near the building. These connections are dedicated and full duplex, meaning that the download and upload speed and bandwidth are the same.

 

As the point-to-point architecture features dedicated fiber, it’s also able to deal with higher capacity and technology changes down the road.

 

HOW NETWORK TYPES AFFECT FIBER PRICING

Guess why a PON is a cheaper option? There’s a lot less fiber needed than a point-to-point network. The central office would have an optical line terminal (OLT), which connects by multi-fiber to a series of passive optical splitters that divide the signal up to 64 times! This reduces costs by sharing components including an expensive laser with multiple premises. The return data can be sent using a cheaper laser as the bandwidth is less and the splitter is bidirectional.

 

Sounds great, but there’s a drawback with this type of network: the bandwidth is shared so speed is limited. Also, download speeds are much higher than upload speeds, which can be a problem with video conferencing and file sharing.

 

The optical line terminal converts the signal from the ISP’s fiber backbone and also receives the uploaded data from the customer. The passive splitter divides the light signal into two or more signals. It is usually located somewhere fairly close to the customer so as to reduce the amount of fiber required. A 1 to 64 split ratio is common and can be achieved by combining different combinations of splitter. For example, a four way splitter can connect to another splitter located closer to the premises that splits the signal again into sixteen feeds. This saves running so much fiber back to the first splitter.

 

As fiber continues to be rolled out to cities across North America, it’s a good idea get familiar with the different types of PONs.

 

-Broadcast PON or BPON was the original method and used the standard telephone network protocol ATM or asynchronous transfer mode.

 

-Ethernet PON or EPON uses the IEEE Ethernet standard and is capable of 1 Gbps.

 

-Gigabit capable PON or GPON uses Internet protocol or IP and handles data up to 2.5 Gbps downstream and 1.5 Gbps upstream. It is also triple play, which means it can handle voice, data and video. It is the system most planned fiber to the premises (FTTP) will use. However, bandwidth requirements have already exceeded this standard so work is being done to improve it.

 

-A new standard NGPON2 is being developed that will be capable of 40 Gbps downstream and 10 Gbps upstream with the potential of those being doubled.