We have a tellabs modem,CTU-S.Its PMA light shines off and on and our link is disconnected.what is the problem?

A Google search yielded the following:

DMA - Deferred Maintenance Alarm
PMA - Prompt Maintenance Alarm

I have no idea if this correct, so contact Tellabs for confirmation or visit Tellabs Portal and look for literature on the unit such as a service or user's manual. The datasheet wasn't that detailed.