fiber optic cable "one way" ?

[ericinboca]

2003 996C4S

CDR 23

Bose

CD changer

No PCM

Here is the question, followed by the detail -

Do the individual fiber optic cables (2 of them) that run from the head unit to the amp and CD changer , transmit only one way?

Here is the detail -

My CDR 23 quit working. It would cycle on, then off, continuously (no matter what weather conditions). I pulled the head unit, the fuse was fine, as was the fuse in the main panel. I checked all the connections on the back and on the amp and CD changer too.

Durametric pointed to a faulty receiver, so I sent the head unit and the amp to becker auto sound for a bench test. They called yesterday and told me the amp and receiver work fine and they suspect the issue is in the fiber optic cable.

So to test, I did the following, and found the following -

With a light source on the cable where it connects to the head unit in the car, I can see light from ONE of the cables where it connects to the amp and same for where it connects to the CD changer.

With the light source on the end that connects to the amp, I can see light from ONE of the cables where it connects to the head unit. Same with the CD changer.

Now, there is a connector in the front trunk before the cable splits to go to the CD changer and amp. If I disconnect that connector, so I am only testing a fairly short piece that goes from the head unit into the front trunk, BOTH cables light up from the head unit to the connector, and back the other way.

Follow?

I'm trying to figure out if the behavior of the short cable is normal and if the behavior of the cable from the connector that splits and goes to amp and CD changer is normal.

Thanks.