full duplex/half duplex on fiber

[ohalnet53]

the range of the transmission is expressed with hundreds meters if port is configured as half duplex but range increases up to kilometers on same fiber, same modul if transmission is full duplex.

how it happens?

tx in advance for answering

[Marvin Rhoads]

Imagine that in full duplex, the TX and RX queues are essentially working independently. One can keep pushing bits onto the fiber subject only to the higher level protocols' need for ack's. Connectionless protocols (e.g., UDP) don't require the ack's. The constraining factor becomes the propogation of light on the fiber - thus the km's of range.

In half duplex, one is constrained by the need to not flood the line in one direction so that the return direction can have a chance to transmit.

[tz535d]

This does bring up an issue I've always wondered about. Is there any scenario where one would actively want a fiber connection running in half duplex? I would think that fiber should always be running full duplex and it always struck me as odd that a half duplex option was available for fiber links.

[Marvin Rhoads]

In a switched network, I can't think of any reason why one would want to use half duplex operation. Hubs and repeaters are available with fiber interfaces (e.g., 10BaseFL, 100BaseFX). Some are still in use today. (In my old job we had a bunch of Synoptics 105 series that just never ever broke. The small segments were running just fine as shared media segments.) Those equipment types usually require half duplex operation mode.

Hope this helps. Please rate it if it does.

[tz535d]

I see now. Thanks!