question about Fiber Optic

jasonandashley1

I am having trouble understanding something about fiber. One the Tech exam notes i purchased it says:
The maximum length of a 100BaseFX link is 400 meters in half-dupex mode, 2000 meters in full-duplex mode.

I am not sure if half and full duplex are refering to single mode and multimode but if it is, doesnt a signal travel futher in single mode because data only goes one way.

D-boy

jasonandashley1 wrote:

I am having trouble understanding something about fiber. One the Tech exam notes i purchased it says:
The maximum length of a 100BaseFX link is 400 meters in half-dupex mode, 2000 meters in full-duplex mode.

I am not sure if half and full duplex are refering to single mode and multimode but if it is, doesnt a signal travel futher in single mode because data only goes one way.

This might be overkill but should answer your question:

http://www.arcelect.com/fibercable.htm

keenon

that would be refering to MM.

SM fiber can go up to 10km if i'm not correct

Webmaster

Half-duplex/full-duplex does not refer to single mode/multimode. The distances in the TechNotes are based on 100BaseFX over multimode fiber. Special solution exist that allow distances from 10-100KM for 100BaseFX on single mode. The latter is not important for the Network+ exam as it depends on the products being used. 400m for half-duplex and 2000m for full-duplex is what you need to remember for 100BaseFX cable lengths as those are the common and defined standard distances.

Single-mode Fiber

Single-mode fiber has a narrow core (9 microns) that allows light to enter only at a single angle. Such fiber has higher bandwidth than multimode fiber, but requires a light source with a narrow spectral width (for example, a LASER).

Multimode Fiber

Optical fiber with a core diameter of 62.5 or 50 microns. Dispersion of light is greater than single mode fiber so distances are less.

In case you doubt the numbers in the TechNotes, check out table 2 and the text above and below it onthis page at cisco.com.