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Chetan R

Question on "show interface fcx/y transceiver details"

Hello All


I would like to understand what does the following parameter mean when the command "show interface fcx/y transceiver details" is executed.

Note: The SFP type is a SFP+ (DS-SFP-FC8G-SW) 

Transmission medium is multimode laser with 62.5 um aperture (M6)
Supported speeds are - Min speed: 2000 Mb/s, Max speed: 8000 Mb/s
Nominal bit rate is 8500 Mb/s
Link length supported for 50/125mm fiber is 50 m
Link length supported for 62.5/125mm fiber is 20 m 


I understand the above output as follows

SFP+ (DS-SFP-FC8G-SW) with a MMF connected to it with a core size of 62.5/125mm at a nominal bit rate is 8500 Mb/s can have a max cable distance of 21 m (69ft).

The fiber term 62.5/125mm stands for diameter of the fiber cables core & to the diameter of the outside of the fiber cables cladding i.e. 62.5 stands for diameter of the fiber cables core & 125 stands for the diameter of the outside of the fiber cables cladding. 


Will the transceiver detect automatically the type of fiber connected to it? Does the above mean that a SMF cannot be connected to this transceiver?



Paresh Gupta
Cisco Employee

Each optics is supposed to be connected to a specific type of fibre. This is what the command says (It does not detect automatically) and this is what we should do. Technically, you can connect a SM fibre to a SW optics and it *may* work as well. But there are drawbacks for it. MMF have wide diameter. The optics is transmitting light to match that diameter. If you connect a narrow diameter SMF, loss of light would happen. I strongly recommend to go through this link:

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