Config12
23-Mar-2018 to 28-Mar-2018

Collet Fiber on one end, FC on the other; used to replace the output fiber on Config11. Collet marked "DO NOT TWIST"
The input fiber is still FC/FC, from FISH, number 31
This is in line PDBS with the PDBS and fold mirror removed.
Fiber is longer than the FISH fibers, it is Thorlabs F1038-BK and I labeled it with Orange Tape.
It was a little tricky to figure out how to modify the PDBS S/N 2 to connect to this fiber.
See the drawings on page 149 of MOBY NET NB 2.

The through output of the PDBS S/N 2 has lens "3 4  Vis" label. The lens is in a SM05L05 lens tube, this lens tube threads into the PDBS housing. The lens appears to be near or at the internal shoulder (i.e. all the way "in") the lens tube. A SM05L03 lens tube was threaded into the SM05L05 tube, and a second SM05L03 lens tube was threaded into it. Inside this part, again, all the way in, was the FC connector. It was spaced back from the shoulder a little bit with a group of very thin washers and a golden ring. It was held in place with a 0.5" retaining ring.

The collet fiber has external 0.535-40 threads, with a length of about 1". The issue was to get it at the correct distance from the lens. Since the FC fiber connector was near the bottom of the 0.3" long lens tube, I figured I should do the same with the collet end. I measured a distance of 12.1 mm from the back of the lens tube to the front face of the original FC fiber connector.

I assembled the Config12 as follows:
Removed FC fiber #21 from the PDBS and the PD2 FC connector
Removed the lens/FC connector assembly from the PDBS body
took apart the three SM05 lens tubes and saved the one with the FC (after I had taken out the FC to see how it was mounted and put it back.)
threaded the SM05L03 onto the end of the collet until it bottomed out on the inner shoulder (it seemed this distance was better than using the washers from the FC lens tube, but I need to measure to see if it is 12.1 mm as well)
threaded the "empty" SM05L03 onto the one on the collet
threaded these onto the SL05L05 with the lens, turing the lens tube, not the collet/fiber
threaded the assembled lens/collet fiber onto the PDBS body, turning the PDBS and not the fiber.
at the other end of the fiber, I
took the FC connector out of the SM01L05 lens tube that is holding the PD2 S2281
attached the end of the new fiber to the FC connector
threaded the SM01L05 lens tube onto the fiber until it bottomed out
arranged the fibers in the port plug so there aren't any gross bends
attached the BNC cable that goes to the preamp to the BNC on S2281.