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. (These must have been from the "To be milled" bag.) 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 "Too be milled" 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".

1/11: Micah showed me how to remove excess material from the collars and bundling tools that were printed recently. I did that and sanded them in the morning. I polished the bundle of "To be milled" sci-fis with 1000 grit paper.

One lesson from today is that I need to use a light touch with fine grits such as 5 micron and below. The fibers should not even squeak against the wheel. If you press them too hard, the fibers will smear and get a little sticky on the ends.

Another problem today is how to hold the fibers - how hard to press down on the bundling tray and how to twist it. It should be a gentle twist. I was twisting too hard.

I think that when you twist the tray it is hard to reach some areas of the bundle with the sandpaper. Maybe some don't get touched at all. That seemed to be happening when I was polishing the sci-fis. One side was polished but the other was not when I was twisting the tray. I might have reached those fibers more readily by reversing the spin direction and the twist direction, but I did not want to do that because it would also change the direction of the striations.

1/12: It may be helpful to remove scratches and smears by moving the bundle to the left or right of center and finish polishing at the center of the wheel.

When polishing fibers, it is best to twist the plate in the same direction always, no matter which way the wheel is turning. That is how to achieve a flat surface across the end of the bundle. If fiber ends are rounded, they scatter light more, so they should be flat instead.

During polishing, we should avoid letting the wheel push the fibers up. We should put them against the wheel so that whichever way it is turning it is going sideways or down where it touches the fibers. With this practice we can make the platform most effective at stabilizing the fibers. If the wheel is going up where it touches them, it is fighting the stabilizing force of the platform.

1/16: To put the blade on the Dremel, you need to push it on and turn it clockwise. I need to remember to put weights on the fibers and put the foam rubber under the Dremel when cutting.

I cut five bundles of sci-fis today.

I started bundling sci-fis. The static electricity kept popping them out of place. I arranged one bundle under the weight in the bundling tool and Micah fastened the top of the collar to the bottom. I tried to put another bundle in a blue collar but it seemed to have a larger hole between the posts of the bundling tool and the corner of the collar where the corner fiber could slip down. I want to find a way to prevent the corner fiber from slipping into that crack.

I thought the static charge on the fibers might be from the plastic bags we are using, but when I tried to bundles some fibers without putting them in a bag, they still had the static charge pushing them apart. I am wondering if the gloves are part of the problem too.

1/18: Ann Marie taught Micah and me about fiber fusing, and Dr. Jones and Jim explained fiber testing. I can unplug the ethernet cable at the corner of the dark box to open it safely.

I cut the ends off some old practice light guides so I could improve my polishing technique. Micah said it would be a good idea to get rid of the flaring or chipped ends to make them more like fibers we would use. The next step was to bundle them. I tried Micah's way of bundling by wrapping strips of paper around the fibers to stack them in layers. I found that method quite difficult, and eventually I resorted to stacking the fibers in the sci-fi bundling tool. Once they were in there, I put a collar around them and got the screws started into their threads. Then with one hand I could hold the fibers in the desired configuration and with the other I could finish tightening the screws in the collar.

Today I read about the fiber testing equipment in the Darkbox Fiber Testing Setup page and identified many components. I'm about ready to be tested for knowledge of the fiber testing apparatus. I do know also that I need to be filled in on some things too.

1/22: I read Micah's suggested steps to take. I took out light guide bundle 407 and looked at how far the screw was sticking out of the front collar. It looks like the screw is barely protruding from the collar if it is at all, so that screw seems to be the right length. There is a little plastic from tapping sticking out around the screw hole, but it doesn't seem likely to scrape against the wheel.

I need to learn the fiber numbering scheme being used in the lab, but for now I have my own, which involves placing the bundle on the styrofoam as if it were time to polish. The top of the bundle is then the uppermost side when the fibers are put against the wheel, and there are 6 rows and 5 columns. Looking at the end of the bundle to be polished, fibers 1 to 5 in my own scheme are in the top row from left to right, and each row below includes the next 5 fibers counted left to right. Therefore the bottom row consists of fibers 26 to 30. I need to translate my numbers into the standard system in the lab once I understand it.

I explained my way of numbering the fibers, and Jim said it would be all right as long as I document it with a diagram.

Using my personal numbering scheme, I can say that in bundle 407 fiber 15 has the most evident flaring. I think I have identified it as the one with three pale orange bands and one yellow band. It's hard for me to tell whether there is more than one shade of orange, though.

I polished bundle 407 with 1 micron grit by mistake, thinking it was 0.3 microns, and then went on to 0.3 microns. I finished off the bundle with copier paper and asked Jim to look at it. Jim said the fibers were well polished, but the front collar was not holding them right and some of them were pushed out of position and damaged. He told me to identify the color codes of the damaged fibers.

It appears that the USB camera for photographing the polished fibers is a Carson MM-840 eFlex. I installed the xploview software for it on my computer.

I took some pictures of the downstream polished end of bundle 407.

1/23: Micah wanted me to find which fibers in recently polished bundles have flared cladding. I reviewed his lab journal to find out which bundles we have polished this month. As I read the lab journal, we started with three collections of scintillating fibers:

“To be milled”: 40 “To be fused”: 36 “To be polished”: 18

Micah also calls one collection "To be end milled." I think this probably refers to the ones "To be milled." I will have to check.

From Micah's lab journal I see that we polished a bundle of 30 of the "To be milled" fibers as far as the 5 micron grit. Since the sci-fis don't have identifying bands, I can't distinguish one from another to identify which are flared. However, I can identify specific light guide fibers by their color codes.

From Micah's lab journal and the Sanding/polishing progress spreadsheet, it appears that we polished the downstream ends of bundles 403, 405, and 407. These are all light guides.

I looked at bundle 407 and identified fiber 15, which is flaring, in addition to the fibers I identified yesterday at Jim's request. I also found bundle 405 and looked for flaring. I saw at least one fiber flaring on the downstream end and four upstream. To identify them, though, I thought I should unbundle them, and I would want to do that on the conference room table. I thought I should get Jim's approval for that idea. I will also have to take out several more bundles to reach bundle 403.

I looked in the box of sci-fis that were there before this month's cutting. I saw the three bags, "To be milled," "To be fused," and "To be polished." As I expected, there are 10 in the "To be milled" bag. I think the other 30 are still in their collar on the sci-fi polishing plate. I will have to check whether they look polished. If we only got to the 5 micron grit, they either need more polishing on the same end or they need to be turned around and polished on the other end. Now that I think of it, I'm not sure whether we polished only one end or both ends of those sci-fis.

One thing I can do today is to practice polishing on the light guides I cut last week for the purpose.

1/24: I am ready to begin polishing the practice bundle. The gap between the wing of the plate and the slider is narrower on the left than on the right as I face the wheel. Therefore, I think I should twist the end to be polished right and the end farthest from the wheel left.