Can't get switch to switch over SFP working

[Ericarthurc]

So here is my setup: 

A Cisco Catalyst 3750G to a Cisco SG350-52P

I have 1.25Gb SFP LC modules plugged into both. In between them is a pretty long 12 strand fiber run; maybe 300 meters. Then I have OM4 LC cables from the fiber cabinet on each side going into the SFP ports on the switches... It just isn't working... But the crazy thing is it was working for about a day then I lost the signal and can't get it back up. When it was working I was getting full gigabit lan. I tried new SFP LC modules for the switches but still no luck. My next step would be new LC cables. 

 

I checked the end of the LC cables with my phone camera and there is the laser coming through I can see it. 

 

Maybe someone has some advice? Or I am missing something? 

 

Side note: I didn't do the fiber line install, but the way it was ran is the "laser" was coming from the main switch down the same side as the laser coming out of the second switch. And I am pretty sure that's wrong, so I swapped the fiber lines around, so the laser comes down one side and the second switch shoots it's laser from the other side. Hopefully that's correct, sorry nooby here.

 

 

It's works when I plug it directly into the main switch straight from one LC cable up close, over about 3 meters. So maybe it's a distance issue?

[BSpendlove]

If what you've mentioned as the laser collides on the same fibre, you can potentially cause issues with the SFP if you accidentally do this. You've probably damaged the SFP and now it doesn't work more than x distance

[BSpendlove]

But yes, the TX part of the SFP will generate the actual laser and the receiving side would just kind of act passively and terminate that laser, so you're right in swapping them over.

[Ericarthurc]

5 hours ago, BSpendlove said:

But yes, the TX part of the SFP will generate the actual laser and the receiving side would just kind of act passively and terminate that laser, so you're right in swapping them over.

Then I am wondering if it's a distance issue. I was using multi-mode SX SFP modules for the switches with OM4 multi-mode cables. I just ordered some single mode LX SFP modules and some OS2 single mode cables. There rated for 10Km so I hope that works. 

 

I just don't have the documentation on what type of fiber was installed; all I know is it's 12 strand. 

 

Thanks btw

[Lurick]

If you're using multi-mode fiber then I think for the SFPs they can do anywhere up to 300m to 500m depending on the quality of the fiber in between. Single mode fiber can do anywhere from 2KM for "short" range SM fiber up to 40km+ (of course it gets more expensive then)

[mynameisjuan]

12 hours ago, BSpendlove said:

If what you've mentioned as the laser collides on the same fibre, you can potentially cause issues with the SFP if you accidentally do this. You've probably damaged the SFP and now it doesn't work more than x distance

This doesn't happen until you start 20km SFPs a few m apart.

[Ericarthurc]

13 hours ago, BSpendlove said:

If what you've mentioned as the laser collides on the same fibre, you can potentially cause issues with the SFP if you accidentally do this. You've probably damaged the SFP and now it doesn't work more than x distance

I changed out the SFP with new ones on both sides, still having the issue. I have LX singelmode ones coming Monday, so I will give those a try

[BSpendlove]

1 hour ago, mynameisjuan said:

This doesn't happen until you start 20km SFPs a few m apart.

I've had 2 clients do this and it broke the sfp. So it does happen. 

 

Edit:probably rarely, but it does happen. 

[Acedia]

On 6/14/2019 at 10:54 AM, BSpendlove said:

If what you've mentioned as the laser collides on the same fibre, you can potentially cause issues with the SFP if you accidentally do this. You've probably damaged the SFP and now it doesn't work more than x distance

That's not correct.

Just disconnect the strands at the end and swap them around. It's not damaging.

[BSpendlove]

2 hours ago, Acedia said:

That's not correct.

Just disconnect the strands at the end and swap them around. It's not damaging.

As I mentioned previously, it's rare and typically don't generate enough light to cause damage but it can in a 0.025% chance. It's happened to me with OM3/4 twice.

[Ericarthurc]

I checked out the fiber cable that was installed and this is most likely what it is:

https://www.anixter.com/en_us/products/012E8F-31131-29/CORNING/Indoor-Outdoor-Fiber-Optic-Cable/p/373-COR8.3-TBRD-12

So it's OS2 single mode

[Lurick]

12 minutes ago, Phoinix said:

I checked out the fiber cable that was installed and this is most likely what it is:

https://www.anixter.com/en_us/products/012E8F-31131-29/CORNING/Indoor-Outdoor-Fiber-Optic-Cable/p/373-COR8.3-TBRD-12

So it's OS2 single mode

That would explain why the MM modules didn't work over a distance

[Ericarthurc]

The fiber is single mode; LX SFP modules and OS2 LC cables arrived today and we got bandwidth now .

Thanks everyone.