40G Certifier Negative Loss of Fiber Testing

Knowledge Base - Solution

Testing with Viavi 40G Certifier fiber optic modules and the results are failing with negative loss readings.
Negative loss means the fiber under test is measuring less loss than what was recorded when the reference measurement was performed. This means there are poor reference conditions. Check the following things: 1. Make sure the proper reference type is selected (single jumper, dual jumper, etc..) 2. Make sure the fibers being used are reference quality. 3. After storing the reference preform an AUTOTEST on the reference fibers. It should have very minimal loss (.03db). 4. When performing a two or three jumper reference disconnect and reconnect the fibers and then run the AUTOTEST again. DO NOT REMOVE THE TX FIBERS CONNECTED TO THE LOCAL AND THE REMOTE.  Once the reference has been stored you may not touch the TX fibers on the unit! If  you cannot get consistently good AUTOTEST results on the reference jumpers when disconnecting and reconnecting the fibers then the reference fibers are suspect and should be replaced. Bulkhead connectors should be replaced as well as they can cause inconsistent results. Once you can consistently AUTOTEST the reference fibers after breaking and reconnecting the fibers then the negative loss values should no longer occur when testing.