Fiber Polishing Procedure
Overview The non fused ends of each fiber must be polished to a mirrored finish. This allows the greatest amount of light transmission through the end of the fiber. Fibers are polished in their appropriate collars, SciFis in their 6x6 collar and light guides in their 5x6 collar. Polishing bundled fibers in their collars affords a number of advantages, the main ones being square fiber ends and minimal cladding flaring. Because the fibers are polished in their collars, it is important that the fiber ends are flush with one another. The scintillating fibers are easily made flush in their collar, but with light guides it is not so easy. For this reason, the light guides are polished as soon as they are returned from end-milling and while they are still in their collars. The end-milling process leaves the fiber ends flush with one another, and so that step can be skipped with the light guides.
Procedures
- Clean the table that you will be polishing fibers on. Any dust, sand, or dirt on the table will translate through the paper and scratch the fibers.
- Set out 2-4 pieces of clean copier paper in a stack, and tape them to the table on each corner.
Light guide fibers
- If polishing recently end-milled light guides, find the side that has the most fibers flush with one another. This is the side you will polish.
- Note: the end-milling process cuts the fibers about .5 mm from the end of the collar. This half of a millimeter protrusion of fibers will allow the fibers to make contact with the paper instead of the aluminum collar, allowing the fibers to be polished. This protrusion is an artifact of the end-milling process, and should be taken full advantage of.
- Remove the collar from the end of the fibers that is not being polished.
- Place the collar square on the paper and support the other end of the light guide fibers by holding them above your head for the entirety of the polishing process.
- The light guide is now ready to polish.
Scintillating fibers
- If polishing scintillating fibers, select the bag from the dark box with the bundle of fibers to be polished.
- Determine which end of the fibers has the flattest end-mill cut. This is the side that will be polished.
- Place the fibers carefully in their 6x6 collar, making sure that the fibers are square.
- Because these fibers have not just been end-milled, the person polishing the fibers will re-create the ~.5 mm protrusion of the fibers from the collar edge so that they may be polished.
- Place two .5 mm spacers underneath the collar but not underneath the fibers.
- Loosen the collar so that the fibers fall to the table while the collar is being supported by the spacer.
- Push on each individual fiber with a gloved finger, ensuring that the fiber end makes contact with the table.
- Without moving the collar, tighten it so that the fibers no longer move inside.
- Look at the table side of the fibers.
- If they are flush with one another they are ready to be polished.
- If they do not all look flush with each other, repeat the process with the spacers above until a relatively smooth polishing surface can be achieved.
Polishing
- Begin making small circular movements with the collar on the paper while applying even pressure downwards.
- The collar serves to maintain the fibers perpendicular to the paper at all times. This will minimize rounding of the fiber ends during polishing.
- After a while the paper will become smooth and its polishing properties will become reduced. When this occurs start to slowly move to another portion of the paper.
- Once the complete surface area of the polishing paper has been used the top sheet may be removed to expose the under sheet.
- Note: Maintain at least two (and no more than four) sheets of paper on the table at a time. Too few or too many sheets can result in possible cladding damage.
- Continue polishing until a mirrored surface is achieved.