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Wired Networks Thread, Fiber optic connection issue in Technical; Our main switch is a HP Procurve 4108GL - We have recently had a new fiber optic run from the ...
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    Fiber optic connection issue

    Our main switch is a HP Procurve 4108GL - We have recently had a new fiber optic run from the main switch over to a new switch/cab in the music area. Connecting the main switch to music is an OM3 patch cable which comes out of an SC port (J4131A) and into a new LC patch panel.

    The switch the other end is an HP 2910-48 with a HP J4858C GBIC module (SX-LC) inserted. The cable comes out of the fiber patch panel in music and into the HP GBIC module. Again this patch cable is OM3 (LC-LC).

    For some reason is just won't connect! I've checked and confirmed all of the ports both ends are working, so I just can't figure out what's wrong!

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    Often when I've had this the fibre pair is unintentionally or unknowingly swapped somewhere along the line - can you swap the pair round at one end?

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    BassTech (14th March 2014)

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    i connect oen end to the switch and take a piccy with my phone of the ends, one should be glowing red. Then do the same at the other end and the opposite will be red to check the run is most likely ok.

    Then if they are ok I swap the A and B round to check.

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    BassTech (14th March 2014)

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    Quote Originally Posted by Achandler View Post
    i connect oen end to the switch and take a piccy with my phone of the ends, one should be glowing red. Then do the same at the other end and the opposite will be red to check the run is most likely ok.

    Then if they are ok I swap the A and B round to check.
    This ^^!

    I called a cable company back to check what they'd done because of this... Man I felt stupid!

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    Quote Originally Posted by Achandler View Post
    i connect oen end to the switch and take a piccy with my phone of the ends, one should be glowing red. Then do the same at the other end and the opposite will be red to check the run is most likely ok.

    Then if they are ok I swap the A and B round to check.
    Ah, didn't know this - I did see the red lazer coming out both sides so I assumed the run was ok. So should I swap the SC connection A/B ends around?

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    Yeah defo, if you have the laser at each end the run should be fine.

    I can't emember which is active and no active but basically you have the laser go from one end to the other, obviously you don't have the lasers going through another one side of the run and the other one with no lasers in at all (if that makes sense). I think basically you go A (sender that shows laser) to B on both ends, so they cross at some point (but I don't actually know for definite.)

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    I'm trying to swap A/B around but I'm worried I'm going to damage the cable - how are you supposed to swap them?

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    you could force the datarate and duplex away from auto. this has helped me with no connects on new fiber.. I've also used a torch to test the fiber with my techie on the other end!

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    Usually from the fibre patch there is an A and a B, this shoudl be an ST end, two quite large ends.

    The other end is an LC end, usually two small connections, if you push them in on the patch bay they have retianing springs, so push and turn it, it shoudl pop off.

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    BassTech (14th March 2014)

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    Quote Originally Posted by Lee91 View Post
    I'm trying to swap A/B around but I'm worried I'm going to damage the cable - how are you supposed to swap them?

    SC and LC cables should just unclip from the thing that holds them together. I use a gentle twisting action to pop LC out and a small screwdriver to lever SC clips open so they can be removed backwards

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    BassTech (14th March 2014)

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    Quote Originally Posted by Lee91 View Post
    I'm trying to swap A/B around but I'm worried I'm going to damage the cable - how are you supposed to swap them?
    Generally speaking it's easier to unclip the SC end and reverse the pairs. Some very gentle pressure with a flat-blade screwdriver will do it. Go carefully and if it's the first time you're doing it, get a spare patch lead!

    Edited to add - there's a little plastic housing around the pairs that will unclip. Some are easier than other.

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    BassTech (14th March 2014)

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    Got any other gbics you can test? Way back when we had a 4108 we found it to be incredibly fussy with gbic versions, models and if you try and swap one type of gbic for another (such as an LX for an SX one for example) the switch wanted a reboot to pick it up. Was a right PITA. Chances are if you've got light on both ends then i'd put it down to either GBICs or switch software.

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    Managed to swap it now - swapped the LC end. Plugged it in and it connected straight away!

    Thanks all

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    I use a modified patch lead and a torch when checking our fibre as it's safer than looking at a laser.

    I've found in the past that one patch panel has accidently been wired in a different sequence to the other end, but as the connections are all ST it's easy enough to reorder them in our panels.

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    Yes Do be careful looking at lazers guys, I know of people who have been blinded by looking at fibre that hasn't been connected and someone connected it at the other end unknowingly...



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