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  1. #1

    Cisco Router for terminating SMF SC Interface

    Hi Gurus

    I have a requirement where one of our partner is planning to connect to our datacenter using a dedicated leased line.

    As per our partner, they will engage a Leased line vendor for this. This vendor will terminate the leased line ( Single mode fiber -- SC connector) to the Comm room of our Colocation provider.

    I have next to nothing knowledge about fiber connectivity and have few questions in this regard.

    Q1. If Single mode fiber is terminated at COLO's Comm room in form of SMF SC connector, what kind of cross connect should we request from COlo's comm room to our cabinet. ( SMF / MMF )

    Q2. How are these cross connects terminated in cabinet? Do Colo provider use some kind of fiber patch panel or they simply provide a fiber link with SC/LC connectors at the end of it?

    Q3. If cross connect needs to be SMF SC then which cisco routers support SMF SC interfaces? Do I need SC-LC patch cable?

    (I looked at the various option but could only find the following GLC-LH-SM or GLC-ZX-SM for SMF connectivity. I read about these and found that GLC-LH-SM is used for terminating single mode fiber that spans up to 10 km and GLC-ZX-SM is used for terminating single mode fiber that spans up to 70 km in length. It looks as if both of these support LC connectors. Are these the only two SMF connectivity options? Do I need SC-LC patch cable )

    Q4. Our partner only tells us that the terminated link will be terminated using SMF SC. How to figure out if GLC-LH-SM or GLC-ZX-SM is required.

    Last edited by New_Pro; 09-09-2009 at 10:10 PM.

  2. #2
    Join Date
    Mar 2007
    More than likely it will be single-mode (1000Base-LX), so the GLC-LH-SM. Confirm the wavelength with them - if you are not using any sort of intermediary media converter or switch, your fiber has to be the same mode as the other end. If you use an SFP, it will be LC. If you use a mini-GBIC, it'll probably be an SC connector. You can get a small patch cable and coupler to change the connector type. We get everything SC into a patch panel in the top of the cab, and use SC to LC patches when we need LC. It gives you the most flexibility.

    It sounds like you're in a bit over your head, it might be worth enlisting the help of someone. This is pretty basic networking.

  3. #3
    Join Date
    Feb 2002
    New York, NY
    As voipcarrier mentioned, it will probably be 1000Base-LX. Pretty much any switch or router that can take SFPs or GBICs should support it.

    The cross-connect would need to be SMF too, and your provider should be able to give you an SC or LC connection at your end. The more flexible option would be to have SC to a patch panel, then use an SC-SC or SC-LC patch cable as appropriate.
    Scott Burns, President
    BQ Internet Corporation
    Remote Rsync and FTP backup solutions
    *** ***

  4. #4
    Join Date
    Jun 2001
    Denver, CO
    Fiber can be confusing if you have not worked with it previously. You really have three things to be concerned about:

    1. Type of fiber.
    2. Type of GBIC/SFP
    3. Type of connector (SC / LC)

    These items are all interrelated, to some extent.

    You choose your GBIC/SPF based upon fiber type (SMF / MMF) and distance. You choose your connector typically based on if you are using a GBIC (SC connector) or SFP (LC connector).

    Typically, fiber is terminated into a LIU. If you get a fiber cross connect from your provider, they may or may not install a LIU into your cabinet. If fiber is going into an LIU, the LIU itself may be SC or LC connector; this matters only so far as determining if you need a SMF LC to SMF LC jumper or SMF SC to SMF LC jumper. If you are just going to be handed the tail end of a jumper, be sure to specify that your end needs to be LC or SC, depending on your use of GBIC or SFP.
    Jay Sudowski // Handy Networks LLC // Co-Founder & CTO
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  5. #5

    Cisco Router for terminating SMF SC interface


    Thanks a lot for your valuable inputs.
    It really cleared a lot of confusion.

    Only confusion left in my mind is regarding the two options available on selecting SFPs for Cisco router.

    What factors are taken into account for selecting GLC-LH-SM Vs GLC-ZX-SM for SMF connectivity. Is it only the distance?

    As per our partner the leased line will be a single mode fiber with SC connector. How should I make sure I am selecting the correct SFPs (GLC-LH-SM/GLC-ZX-SM) on our end of cisco routers. Are there any questions that should be asked to the leased line vendor to clear this up.

    Thanks again

  6. #6
    Join Date
    Feb 2002
    New York, NY
    Quote Originally Posted by New_Pro View Post
    Are there any questions that should be asked to the leased line vendor to clear this up.
    You really need to know whether the vendor is using 1000Base-LX or 1000Base-ZX. They operate at different wavelengths.

    Even if your client is outside of the LX distance limits, it's possible that the line vendor is using a switch or repeater somewhere in between, so there are no guarantees.
    Scott Burns, President
    BQ Internet Corporation
    Remote Rsync and FTP backup solutions
    *** ***

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