BW January 2018

1/5: Micah showed me how to cut sci-fis with the Dremel, how to bundle fibers with the new collars, and how to polish them with the grinding wheel. I bottomed out bundle 403 to 0.008 inches with 400 grit paper. With the the 400 grit paper it should make a rhythmic sound, not constant but one with beats as the wheel turns.

1/8: I started polishing bundle 403 with 1000 grit paper. At first I was not pressing hard enough. I need to press hard enough that I can hear the fibers making contact with the paper.

I put too much glue on the 5 micron paper and had trouble removing the residue from the grinding wheel. I need to use a couple of very short bursts of glue. If there is too much and it won't come off, a clean sharp razor blade will be useful. I need to hold it so the plane of the blade makes a very small angle with the wheel, and it won't scratch the wheel.

The downstream unpolished ends of the bundles are closest to the colored rubber elastics.

1/9: I started polishing bundle 407 of light guides with 400 grit paper. Micah noticed that the cladding of one of the fibers was flaring, and dust from the polishing was getting caught between the cladding and the interior of the fiber. A white line was visible along the edge of the fiber when the end was facing towards me, and there was a curve of white from one corner to the other when you looked at the side of the fiber. I could barely see that curve, so we looked at it through the microscope. I eventually got a better glimpse of the flare looking at the end of the fiber, but not such a good look at the curve on the side of it.

Micah said we should polish with the 400 grit paper until the flare is gone. We may need to move the fibers forward in the collars to continue polishing after finishing with the 400 grit or 1000 grit. They are protruding around 0.016" beyond the collar, and we might want 0.032".

When Micah left I started polishing a bundle of sci-fis with 400 grit. I progressed to the point where the ends of the fibers seem to be all in one plane. For now that is as far as we want to take them because we aren't sure how long they should be.

1/10 I continued polishing the sci-fi bundle with 400 grit, but the cladding was flaring. I wondered if St. Gobain had any documentation about what to do with the ends after cutting fibers. I asked Jim about that, and he gave me a research paper from Fermi National Accelerator Laboratory about polishing optical fibers. However, the paper did not give me ideas for our situation.

Jim said I could be pressing the fibers too hard against the sandpaper, spinning the wheel too fast, or not changing the sandpaper enough. Something must be different because the fibers did not flare during the summer when Micah was polishing.

Later we asked Dr. Jones about the flaring and he did not think it was a problem the way it was happening. If the the cladding is peeled back for more than 1 mm along the fiber, it is a problem, but that was not our situation. I went ahead with polishing bundle 407 and bottomed it out to 0.016".