ABSTRACT
Before discussing optical access architecture, it is required to know about the basic access techniques used for networks such as local area network (LAN), wide area network (WAN) and metropolitan area network (MAN). The asynchronous TDM mechanism provides contention methods (or random-access schemes) and deterministic techniques. In random access contention methods are considered in networks having many users to transmit the messages to other stations through a common channel. The collision occurred in non-persistent carrier sense multiple access (CSMA) method is decreased in slotted non-persistent CSMA in which the function is same as that of the slotted ALOHA scheme. Distributed-control access methods are based on token-controlled process. The techniques are used in ring or bus topologies. Tokens are special bit patterns or packets, usually several bits in length roaming from one node to the other if there is no message traffic.
