newbie fiber question

[NetAdminMBC]

I've only dealt with fiber in labs, never on the job, so I'm not a newbie in general, but a newbie to fiber.  I'm hoping I'm just making some easily correctable rookie mistake here

Our LAN has two network closets, about 75 meters apart.  We've used the Cat5e backbone between them for years and ignored the fiber backbone, but now I need to use it due to a switch upgrade.  In TenGig5/0/7 and TenGig5/0/8 on the 9410's supervisor module, I first tried SFP-10GBase-LRM modules, and then  SFP-10GBase-SR - both report properly to the switch ("show int [etc]" list the type of module), but though everything is physically connected (I hear the click on all patch cables), "show int" tells me "Down (not connected)."   If I pull the patch cable from the premise wiring and (not looking directly at it!) try to shine it on my hand or the wall, I see no glow - it's dark.

Is there something I have to do to those port configuration to tell it to use the SFP?  Enable it somehow?

[Reza Sharifi]

Is the fiber Multimode or Singlemode?

SFP-10GBase-SR should be used with Multimode fiber.

HTH

[NetAdminMBC]

50 micron multimode

[Reza Sharifi]

Ok, great. So, you need to use SFP-10GBase-SR on both sides of the connection.

Is the fiber good? Do you have a tester to test the fiber by shining light on one side and seeing it on the other side (don't look at it directly)?

Also, if you are sure your fiber and SFPs are good, make sure the ports are not admin shut.

HTH

[chrihussey]

For starters, the light is not in the visible spectrum so it's not anything you can see. It can however cause retina damage, so going forward I wouldn't recommend trying to see light.

Also, when you have the fiber connection in place, if it was down down, then the next thing to try would be to flip transmit / receive on one end. It might be an issue as simple as that.

Hope this helps.

[chrihussey]

and sorry, I misread and thought you said you tried to see the light.

[acampbell]

Hi,

Here i a link to a nice document that shows pictures and good information.

https://www.cisco.com/c/en/us/td/docs/interfaces_modules/transceiver_modules/installation/note/78_15160.html

Make sure that along the line of your fibres you are not breaking the
length rules in Table 2 ( You will need to find the spec of your patch leads and cable)

Also remember that there needs to be a "cross" of the fibres in the length somewhere

TRANSMIT -------->>>------------ X -------------->>>----- RECEIVE

RECEIVE  --------<<<<----------  X ------------<<<<<<<--- TRANSMIT

Look a fig 1 -- It shows which strand is Transmit & Receive

[NetAdminMBC]

how would I flip transmit/receive?  the cables I'm using (TrippLiteN520-03M) have a molded connector at each end; I'm pretty sure I'd have to break it to exchange the strands.  Manufacturer's pic attached. I removed the white protectors from teh ends, of course.

[Reza Sharifi]

You can't do that for this type of cable. These are standard and you should not need to swap the stands.

Can you try it with regular fiber patch and the SPF+?

You need LC/LC MM fiber patch and the SFP+s

HTH

[NetAdminMBC]

These are my only fiber patch cables, so I can't try other cables. 

So, here's some more info: just for fun, I patched both ends of the cable to the same switch.  Both Te5/0/7 and Te5/0/8 immediately came alive.   Went to the other LAN closet and did the same, same results - lights up immediately.  So, I'm pretty sure it's not the SFP or the patch cable, right? 

Thinking it must be the premise wiring.  Will look an LED flashlight to see if anything comes through and look for other testers.

[chrihussey · Accepted solution]

The fiber jumpers by default go transmit to receive. Notice the yellow and white fiber bands are flipped on each end. So if each end is doing this you are essentially flipping it twice and are going TX-TX and RX-RX.

It's tough to tell from the picture of the jumper, but they generally snap together and you may be able to pry it apart.

What are you patching the fiber patch cables into from the switch? A fiber distribution box or panel? If so, just as a test, can you flip the fibers on one of the pairs between panels?

[Reza Sharifi]

Yes, it seems that there is something wrong somewhere with fiber backbone patches.

If you have a tester, you can simply shine it from one side and should be able to see the light on the other side if all patches are good. Again, never look into the fiber directly.

HTH

[NetAdminMBC]

Hey, one and all - it turns out that if you're careful, you can separate those strands from the plastic housing.  I did so, and patched them in, and it all came alive. 

Thanks to all for your help.

(here's a useful video link I got from elsewhere, in case anyone stumbles across this thread and need visual aids: https://youtu.be/-5VH2tZEoDQ?t=43s)