What is duplex fiber optic polarity?

Most fiber optic channels use separate transmit and receive paths between the active equipment. On rare occasions a simplex channel is used. Therefore, it is important that the design of the fiber system ‘manages’ the path so the administrator cannot make a mistake when patching active equipment. There are two reasons for this. First is safety. If the design is not controlled there is a temptation for the technician when patching to look down an active fiber to identify which of the two connectors is the receive. This is not only a potential eye hazard but often fruitless as the 850 nm wavelength is only just in the visible spectrum for humans and longer wavelengths will not be seen at all. The second reason is that if plugged incorrectly at best it will not work and on some topologies, it can isolate parts of the network.
This video describes duplex polarity in fibre optic systems.
Learn even more at the Cabling Science Institute.

Written by James Donovan
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