PON Networks Brief Introduction
Passive Optical Network
A passive optical network (PON) allows to eliminate all active components between the telecommunications service provider and the client, introducing in its place passive optical components to route traffic across the network. The use of these passive systems, whose main element is the optical splitter device- reduces the cost of installation and maintenance.
PON networks are the basis on which it is building the new networks for broadband access over fiber optics to the home. This new technological approach is known as FTTH (Fiber to the home).
Structure of a PON-FTTx network
A passive optical network is a multi-point network consisting essentially of:
- OLT (Optical Line Terminal)Located in the operator’s facilities.
- Singlemode fiber optic network with a tree-branch topology
- Optical splitter.
- ONTs (Optical Network Terminal),Located in the client’s home.
The transmission is performed between OLT and multiple ONTs using common fiber optic network. In this fiber network optic splitters are present which are responsible for routing the signal from the OLT to each of the ONT.
The downstream channel of a PON network uses a wavelength of 1490nm and behaves as a point-multipoint transmission system. In this environment the OLT sends signals and the optical splitter is responsible for providing to all the ONT. Once the information has come to the ONT can only be open those pieces of information to a specific ONT user. The rest of the information remains encrypted.
A PON’s upstream channel behaves in a model of point to point communication. Here, each ONT transmits content to the OLT at 1310nm. It is therefore necessary to use arbitration transmission channel models by use of TDMA (Time Division Multiple Access) for each ONT send the information in different times. This control is done from the OLT. At the same time, all users are synchronized through a process known as “Ranging.”
Advantages of passive optical networks
- More bandwidth for the user. The current GPON technology can provide up to 2.5 Gbps for each 64 users. Currently work is being done on standards to raise the bandwidth up to 10Gbps.
- Increased coverage and quality of service. From the operator’s network it is possible to extend a PON to a distance of 20 km. With DSL-based technologies a maximum 5.5-km are being reached. Furthermore, PON networks are immune to electromagnetic disturbances origin.
- Cost savings associated with network deployment. Besides the cost savings the use of optical fiber versus copper, the tree-branch topology of the fiber network, alongside the use of transmission systems monofibra, significantly reduces costs.