What is POLAN (Passive Optical Local Area Network)

In the earlier times for telecommunication or for enabling an internet connection copper wires were used. Optical Fibre, later on, replaced the copper cables due to advantages such as greater bandwidth, faster speeds, reliability, the capability to carry information over long distances etc. here maybe two ways of splitting up the data and further transmitting it; they are an active optical network and passive optical network (PON). The network setups in a LAN (Local Area Network) where PON is used may be called as a POLAN (Passive Optical Local Area Network).
Optical Fibre uses light signals for the transmission of data. In order for the data to be retrieved at the proper destination, a way is needed to separate it.

In an active optical network, electrically powered switching elements are used. These elements manage the distribution of the signal to specific customers. These switching elements work in various ways to place the incoming and outgoing signals to a proper place.

A passive optical network, on the other hand, involves no electrically powered switching elements. They instead use optical splitters to separate and collect optical signals. Since these elements don’t require power, hence the name “passive”. Such networks require power only at the source and receiving the end of the signal.

A PON system consists of optical line termination (OLT) at the communication provider’s end and a number of optical network units (ONU) at the user’s end. The term "passive" simply means that there are no power requirements while the network is up and running. A POLAN implements point-to-multipoint architecture i.e. here unpowered fibre optic splitters enable a single optical fibre to serve multiple endpoints.
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An OLT is a device which serves as the service provider’s endpoint of a POLAN. An OLT performs a conversion between electrical signals used by the service provider’s equipment and the fibre optical signals used by the passive optical network. An ONU is situated at the customer’s end. It is a device which transforms incoming optical signals to electronic signals.


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