Connecting a 100M switch to a 1G switch with fiber

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If you have one 100 meg switch and one gig switch does the fiber have to have converter so they can see each other.  Is a converter required?
Had a splicer come in to repair fiber between two building one 100 meg and the other is a gig switch
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Posted 2 years ago

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Drew C., Community Manager

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Hi Wayne, I've edited the title of this post for clarity.

As long as the 1G switch can negotiate down to 100M, you likely won't need to do any kind of conversion.  Unless you're using something other than OM3 or OM4, you should be fine.  You may need a mode-conditioning patch cord if you're mixing multi-mode and single-mode fiber.
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Nick Yakimenko

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Please provide correct models of both switches and models of SFP transceivers that you plan to use
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Erik Auerswald, Embassador

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Hi Wayne,

in general, 100M over fiber is not compatible with 1G over fiber. There exist combined SFPs that support both 100BASE-FX and 1000BASE-SX, but they are not often used because they cost as much or more then one 100BASE-FX and one 1000BASE-SX transceiver together.

100BASE-FX uses the same fiber cables as 1000BASE-SX (multi-mode fiber, MMF). You cannot passively convert between different fiber types, you would need an active converter (e.g. a switch with both types of transceivers).

Best regards,