MS120-8 SFP Fiber troubleshooting

DonnyKC
Conversationalist

MS120-8 SFP Fiber troubleshooting

So I am trying to connect two buildings via single mode Fiber we just had installed. one MS120-8 to another MS120-8 If I have both MS120-8's in the main office connected via their Fiber SFP's (both recognized by the switches) and connected via an LC/LC SM DPX cable they connect just fine. I move one switch over to the new building, connect it to the fiber panel ports 1&2 and at the office I have the office switch connected to port 1&2 on the fiber panel, via the same LC/LC SM DPX cables and they don't connect. I am at my wits end. I have had the fiber installers back out to check the fiber and its fine, I double checked that my SFP's are working and compatible, and again in the office the connect just fine. Any suggestion on what else I might do to try and trouble shoot the situation?  I have verified the SFP's work. I have verified , LC/LC patch cable are good, and the fiber installers tested twice now and say everything looks good. The fiber run is about 304 meters. 

8 REPLIES 8
BrandonS
Kind of a big deal

Re: MS120-8 SFP Fiber troubleshooting

I didn’t see that you tried swapping pairs. One strand is transmit and one is receive. They need to connect transmit to receive and it sounds like your combination of patch cords and length of fiber may not be doing that. 

Inderdeep
A model citizen

Re: MS120-8 SFP Fiber troubleshooting

I agree with @BrandonS  try swapping the cables and see if u get success 

Regards
Inderdeep Singh
www.thenetworkdna.com
DonnyKC
Conversationalist

Re: MS120-8 SFP Fiber troubleshooting

Ok got back into the office this morning and made sure at the Office SFP I was B-W and at the remote SFP I was W-B, and still nothing. Any other suggestions?

DonnyKC
Conversationalist

Re: MS120-8 SFP Fiber troubleshooting

I figured it out, undid the cross over on the patch cables at the remote location and bam it was good. Thanks for your suggestions and help.

BrandonS
Kind of a big deal

Re: MS120-8 SFP Fiber troubleshooting

I’ve been there. Two crossovers cancel themselves out, so you have to think through all the cross connects from end to end. I do it often enough that I just try crossing over one side as the first step if a fiber link doesn’t come up. I’ll bet you will remember next time 😉

rbnielsen
Head in the Cloud

Re: MS120-8 SFP Fiber troubleshooting

An easy way to verify, is to check which one has light in the fiber. 

 

Now since that it's Lasers, you'll probably risk damaging your eyesight. Instead use the camera on your smartphone, in case you have such. 

DonnyKC
Conversationalist

Re: MS120-8 SFP Fiber troubleshooting

That is a great suggestion. I will keep that in my back pocket moving forward. Thanks again to everyone willing to help! It is much appreciated!

Inderdeep
A model citizen

Re: MS120-8 SFP Fiber troubleshooting

There's nothing to test the fiber directly, other than a separate fiber tester device like a light meter or an OTDR

 

What is usually done is to compare the optical TX and RX levels on both sides, to ensure the signal is within range, if its within range you should be OK.

 

If for example on the first side the optical levels show TX is 1 and RX is -5 and the facing side has TX 1 and RX -22 then the facing side is RX'ing a lot worse signal than the first side. The loss across in one direction is 6 dBm and the other way is 23 which would indicate a connection problem. Note; a -40 or -50 or -80 means no signal

 

Depending on what you see you troubleshot from there

Regards
Inderdeep Singh
www.thenetworkdna.com
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