562
13 Fiber Optic Communication Networks
Fig. 13.42 Operation of a downstream time-division multiplexing process
Sending traffic in the upstream direction is more complicated because all users
have to time-share the same wavelength. To avoid collisions between the transmissions of different users, the system uses a time-division multiple access (TDMA)
protocol. Figure 13.43 gives a simple example of this. The OLT controls and coordinates the traffic from each ONT by sending permissions to them to transmit during
a specific time slot. The time slots must be synchronized because transit times vary
between ONTs (see Example 13.5).
Fig. 13.43 Operation of an upstream time-division multiple access protocol
13 Fiber Optic Communication Networks
Fig. 13.42 Operation of a downstream time-division multiplexing process
Sending traffic in the upstream direction is more complicated because all users
have to time-share the same wavelength. To avoid collisions between the transmissions of different users, the system uses a time-division multiple access (TDMA)
protocol. Figure 13.43 gives a simple example of this. The OLT controls and coordinates the traffic from each ONT by sending permissions to them to transmit during
a specific time slot. The time slots must be synchronized because transit times vary
between ONTs (see Example 13.5).
Fig. 13.43 Operation of an upstream time-division multiple access protocol