single mode fiber - no link

[nflnetwork29]

hello i am trying connect 1 single mode fiber to the Meraki port 25 using 1GB SFP transceiver single mode. LC connector . I cannot get any link light on the Meraki switch. We have tested the line to patch panel and all seems ok . is there any trick on meraki side to get this going ? there is a lack of any commands to assist with any transceiver troubleshooting that i am aware of?  Switch is MS120-24P 

Transceiver is Cisco Meraki MA-SFP-1GB-LX10 Compatible 1000BASE-LX/LH SFP 1310nm 10km DOM Duplex LC MMF/SMF Transceiver Module

https://www.fs.com/products/39371.html

Patch cable is 1m (3ft) LC UPC to LC UPC Duplex OS2 Single Mode PVC (OFNR) 2.0mm Fiber Optic Patch Cable

https://www.fs.com/products/40191.html

[Slobs2]

Confirm the port is not disabled. Also see if on the port status (right below where you configure the port on the switch page) sees the transceiver. 

[GreenMan]

I assume so, but probably worth checking:   when you say one fiber, you really mean one pair of fibres (send and receive)?   Given you have structured fiber cabling, I'd also check that you have them patched properly: send to receive (try reversing the connnectors at one end).

[Brash]

Verify that the fibers in the pair are the correct way around. Try crossing them on one of the cables and see if the link comes up.

[Inderdeep]

@nflnetwork29 : Most of the time the issue is with the connecting TX/RX on both side. Check it is connected correctly on both end.

[GIdenJoe · Accepted solution]

Yeah I always enjoy fiddling those LC connectors out of their holder to switch em around 😉

[Inderdeep]

I saw most of the time issue related to that... 🙂 

[nflnetwork29]

this did the trick. much appreciated everyone who provided feedback!

[agionet]

Hey guys, I'm having the same issue here. Inverted the polarity of the fiber and it linked for a few seconds, was able to see the switch in Meraki dashboard but then it suddenly dropped off. Have tried other ports and swapping it around again to no avail, unable to get it to link up again. 

We've run a cable test on the fiber link and it's OK but no matter what SFP port or transceiver we use it won't link. I have tested the same SFP ports using RJ45 transceivers and they work fine. 

Any ideas? I did notice some RSTP events in the event log in between the time the link first came up and before it dropped off. 

[GIdenJoe]

You'll have to check if BPDU guard for example was on that port and disabled it.

[agionet]

How can I verify if that was the case? The SFP+ port on the primary switch still shows as enabled:

I've also tried multiple SFP ports on the secondary switch to no avail. 
The primary switch is set as bridge priority 4096 in switch settings. All other switches would have default bridge priority. 

[GIdenJoe]

And what is the switch and SFP on the other side of the fiber link?