Fiber SFP Question

[tom baker]

I have a Cisco SFP fiber module that is for single mode up to 80 KM (SFP is a small form pluggable fiber optic driver that plugs into a network switch)
Is there a minimum fiber loss that is required?
I had the SFP lighting a 3 mile run of single mode and changed to go to a 120 ft run. Is the 120 feet too short - not enough loss and will the SFP work on that short distance?

 

[lambertp]

I have a Cisco SFP fiber module that is for single mode up to 80 KM (SFP is a small form pluggable fiber optic driver that plugs into a network switch)
Is there a minimum fiber loss that is required?
I had the SFP lighting a 3 mile run of single mode and changed to go to a 120 ft run. Is the 120 feet too short - not enough loss and will the SFP work on that short distance?

Cisco's documentation states "...the minimum cable distance for all SFPs listed (multimode and single-mode fiber) is 6.5 feet (2 m)." The shortest length I have in production is about 20 feet between switches and have not seen any problems. I've used a 1 m 10Gig multi-mode jumper between devices in a test environment and it failed spectacularly.

 

[zbang]

I know I'm late on this....

There are different SFP modules for different distances and fiber types (single/multi-mode). If you have a ZX or EX module, you should replace it with LX/LH for short distances or insert an attenuator.