I have 2 Allied Telesis media converters hooked into a network, and all the lights are green, both link and flashing activity, but the far end gets the Limited or no connectivity message from the network adaptor. The signal comes from a Linksys 48 port switch, into the media converter, over the fiber, into the far end converter, and then into a netgear 8 port switch. I tried to use a laptop directly into far end converter, but it would not get an ip address and then I got the same message as above. The computers are all set to obtain an ip automatically on both sides of the fiber, so it is not a static ip issue. If I bypass the converters with a long(500 feet at least) cat5 it works just fine, although a little slow. Any ideas what I am missing?

Does the fiber type match that of the media converters? When you order this type of Allied Telesys product, they ask you to specify not only the connector type (ST or SC), but the fiber media as well (MM or SM).

Allied Telesys uses part number logic that will make it obvious as to what you've got.

The point is that you could have boxes that are mis-matched for each other or--more likely--units designed for the type of fiber that you're not actually using!

What are the unit's part numbers and what color is the jacket on the fiber feed, orange or yellow? You might also need to flip the fiber pairs at one end only.

And I almost forgot! If I remember right, there are one or two pushbutton switches on the front of these units. Make sure both of them are in the non-test mode.

make sure the fiber is connected correctly so the transmit on one end is going to the receive on the other, and vice versa. If these boxes have been in place for some time, and just stopped working, sounds like you might have a bad box.

I have ran into a similar problem in the past. Allied Telesis has an excellent tech line, once they answer it . If I remember correctly, one if not both of the devices needed to have the speed hard coded.
I can't remember what the model numbers of the ones we had trouble. We now use the next model up which handles everything automatically.

Thanks for the help, I got a hold of tech support and you are right DayTech, you have to tell the switch full duplex 100 meg on that port. The switch I was plugging onto was 10/100/1000 and the mc 101 can't handle that. They are sending me a fs-201-99 that auto negotiates the switch side and always sets the fiber side to 100 meg full duplex. Hope that works, sounds like it should.