Optical Technologies
Optical Access Networks

A main barrier of service provisioning by means of optical fibers directly to residential and business customers are costs of connecting subscribers to the central office. A large number of point-to-point connections could require many active components and a large number of optical fibers. This leads to enormous increasing of installation and maintenance costs. An attractive solution of these problems is the FTTx (Fiber To The x) architecture. The Passive Optical Network (PON) together with the FTTx allows some customers to share the same connection without any active components.

Optical access network architectures should be simply and the network should be simply from a viewpoint of the activity and services. It means that passive architectures without any switching and controlling are preferred to active architectures. Moreover, the optical network unit (ONU) should be very simply for decreasing of costs and for improving of the reliability. Components used in the ONU should be able to operate without any temperature controlling. These rules exclude a using of more sophisticated lasers and other optical components in the ONU. An equipment of the optical line termination (OLT) can be a little bit more sophisticated, because it is places in the controlling environment and costs are amortized between many subscribers.

Optical networks suggested for this application are together called passive optical networks PON. They use a particular form of passive components as the remote node. Their main advantages are reliability, simplicity of maintenance and an absence of power supplies. The passive optical networks PON divide a signal from one central transmitter between various outgoing fibers, each forwarding to the separated receiver in the particular customer location. Separated receivers from customer locations send signals to the central distribution point, so user share a total transmission capacity of the system. A key advantage of this approach is using only passive components in the outdoor distribution network.