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Cable modem, video phone, fiber optic transceivers...

Cable modem, video phone, fiber optic transceivers...

Cable modem, video phone, fiber optic transceivers...

Hi folks...

Here is a problem that I have been racking my brain trying to figure out for a week now...

We have a cable modem connected to Comcast.  When we directly connect a video phone to the Ethernet port on the cable modem, we are able to communicate using the phone.  The problem occurs when we try to run the Ethernet connection over fiber. The cable connection is in one building and we want to put the video phone in another.  

We leave the cable modem connected in the one building, connect a fiber optic transceiver to the Ethernet port on the cable modem, and connect a fiber optic transceiver in the other building to the video phone (same phone).  We get a connection on the Ethernet and the fiber ports, but no traffic is transferred over the fiber.  So, we moved the phone and the fiber transceiver back to the building where the cable modem is.  We connected the fiber transceivers together using a patch cable.  Still get a link on all ports, but we cannot make a phone call.  

This is single mode fiber. We have tried multiple fiber optic transceivers (and multiple patch cables).  We have rebooted the cable modem several times. We have tried using switches with fiber uplinks in them as well... still get a physical link but we cannot make a phone call.  Long story short, we can connect when the fiber is not in the picture.  Any ideas as to what could be causing this??  

RE: Cable modem, video phone, fiber optic transceivers...

Are you sure you have single-mode fiber?  Are you sure you are using single-mode converters with single-mode fiber?  Are you sure that there isn't a MDI-X/MDI switch on the Etherent side of the far-end converter?

Since it appears to work locally, but when you use the converters it doesn't - even with short cables, you have to look at the converters first.

Have you tried to use these converters with your regular network (attached to a network switch) - try extending a PC's connection as a test.

RE: Cable modem, video phone, fiber optic transceivers...

Those converters work with a different video phone.  It turns out the DLink phone (we tried two of them, same model) we were trying to use is a piece of junk. As I said in my original post, we tried several different transceivers... and yes, they all worked.  Yes, we have single-mode fiber, and yes, the transceivers were for single-mode fiber.  Thanks for your suggestion but it looks like the problem was the phone.  We tried a Sorenson and problem was resolved.  Go figure.

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