Repairing IPG Photonics YRL-4000 Fiber Laser

[BiD]

Hello!

I am slowly working towards repairing a  IPG Photonics Fiber Laser unit I had picked up for fairly cheap, its a 4000W unit.  Currently I am working to repair a severed fiber that's between a "coupler" unit and an optical switch.  I have access to a fusion splicer however I wanted to figure out what type of fiber optic I'm dealing with.

The cable.jpeg is what the cable looks like up close, it's terminated by a bayonet-type connector as seen in connector, that connector goes into the input of the optical switch.  The other end, the metal jacket with the yellow plastic terminates within the rack housing and the inner whiteish jacket continues onto a "coupler".  As far as I can tell all the fiber optic are fused-spliced, I assume this is due to minimize loss and not burnt fiber.  The severed fiber optic is between where metal jacket terminates and the coupler unit.

.  Measurement with the coating on is ~ 213um (coating.jpeg) and the cladding is 123um (cladding.jpeg).  I assume that this is a 125 um fiber optic based on the 123um measurement in cladding.jpeg.

I took the fiber optic and tried to put the cleaved end to be as parallel as possible to the microscope lens and shine incident light on the opposite end of the fiber to get the photo seen in core.jpg.  Based on the approximate pixel ratio of the cladding to the core diameter:  1271px/1598px, I computed the core to be: 125um * 1271/1598 = 99.4um ~ 100um.

This tells me that it's a 125um/100um fiber optic however this seems like an unusual size for a fiber optic. 

* Could someone shed some light on this?
* Am I measuring something incorrectly?
* Does anyone know why the fiber optic and the two copper interlock are free floating in the plastic tube instead of the fiber optic having it's own jacket like telecom fiber optic?