1. a) Why polish?

   1. Polishing creates a uniform surface and prevents scattering from surface variation. It reduces the chances of the tip of the fiber breaking off inside of the connector during handling. It also gets rid of a slightly uneven cleave, or a shelf from a cleave, by polishing it down until then entire surface is smooth.

2. b) Be careful!
   1. This is the most likely time the tip will break off inside the connector. This is not good! The fiber needs to be even with the tip of the connector to provide the desired connection of the core to the source or detector. Most likely it will not be a clean break and it will not be able to be lined up with other fibers, sources, or detectors!
3. c) 3 types of polishing paper
   1. 5um (white)- rough polishing. Used to grind down excess fiber sticking out of the connector.
   2. 1um (pink)- finer polish. Middle step to even out roughness caused by the 3mm polishing paper.
   3. 0.3um (blue)- finest polish. To leave a smooth finish on the tip of the fiber. Reduces the effects of scattering by having an even surface.
4. d) Polishing steps
   1. Once the epoxy is completely hardened it is now cured and ready to be polished. Polishing requires precision as to not break the fiber inside the connector, especially under the epoxy bead.
5. Around one or two centimeters of fiber should stick out the end of the ferrule. Most of this fiber should be cleaved off. Several methods may be used to cleave the fiber about from about one mm or less from the end of the epoxy. (The Thor Lab polishing guide says 1 fiber diameter from the end of the epoxy bead).
6. Once this end has been cleaved, use a 5 micron (white) polishing pad to polish the fiber down until it is flush with the edge of the epoxy bead.
7. This may done by holding the polishing pad vertically, held with the middle finger and the thumb. The pointer finger should help to position the pad in an ‘S” shape. Using the other hand, gently polish the tip of the fiber, moving the connector up and down on the polishing pad until the fiber tip is flush with the epoxy bead.
8. The next steps require a lot of cleaning in order to create a good polishing job done in a timely manner.
9. 5 Micron Polishing (White Polishing Pad)
   1. Using Isopropyl alcohol, clean the polishing surface, both sides of the polishing pad, the polisher, and the ferrule tip.
   2. Dry the surfaces with compressed air.
   3. When everything is clean and dry, put two or three drops of distilled water on the polishing surface and place the polishing pad (shiny side (non-polishing side) facing the polishing surface. The water should create a suction which holds the pad securely in place.
   4. Hold the polisher in the air and place the connector into it. The ferrule should be able to stick out just a little when the connector is completely in place. Pull the connector back enough that the ferrule does not stick out of the polisher and place the polisher gently on the polishing pad. Gravity will cause the ferule to land on the polishing pad just the right amount.
   5. Applying just a little bit of pressure downward, polish the fiber using figure 8 motions. This should leave the shape of a figure 8 on the polishing pad. Depending on the size of the epoxy bead, this step should last between 15 and 50 figure 8s. Polish until the epoxy bead is almost completely gone.
   6. Warning: Do not over polish on this step! This could scratch the ferrule tip or get dirt, dust, or other residue jammed in the fiber. This can be very difficult to clean out or fix. If you over etch using the 5 micron pad, the fiber may appear like this upon inspection using a fiber microscope.
10. 1 Micron Polishing (Pink Polishing Pad)
    1. Using Isopropyl alcohol, clean the polishing surface, both sides of the polishing pad, the polisher, and the ferrule tip. Dry the surfaces with compressed air.
    2. When everything is clean and dry, put two or three drops of distilled water on the polishing surface and place the polishing pad (shiny side (non-polishing side) facing the polishing surface. The water should create a suction which holds the pad securely in place.
    3. Place 2-3 drops of distilled water in a vertical line on one side of the polishing pad. Place the connector in the polisher in the same manner as the 5 micron polishing step. Place the polisher on the polishing pad in the same manner as using the 5 micron polishing step as well.
    4. Polish the fiber using figure 8s that move from the wet end of the polishing pad to the dry end. This should take about 10-15 figure 8s. Check the tip using a fiber microscope.
    5. The fiber should appear smooth and the core visible. If it is not smooth, the fiber may be dirty or not complete ly polished. If this is the case, reclean and repolish the fiber using the 1 micron polishing pad. This pad may be used 3 or 4 times but needs to be replaced after several uses or when it gets dirty.
11. Fine Polishing 0.3 Micron Polishing (Blue Polishing Pad)
    1. This method of polishing is essentially the same as the 1 micron polishing. After cleaning all materials, place the connector in the polisher and place three drops of distilled water on the pad in a vertical line. This time, only polish using 3 or 4 figure 8s, moving from the wet portion of the polishing pad to the dry portion. Check using the fiber microscope. If there are not any scratches and everything is smooth on the fiber surface, this is ready to be keyed.
12. Clean off polishing dust by using the Drag and Drop method.
    1. Squirt some Isopropyl alcohol onto a laboratory wipe (it looks like a Kleenex). Drag the wet part gently across the top of the ferrule. Nitrogen gun it dry.

1. a) Measure Single Mode Fiber (SMF) to D-fiber loss.
   1. This 1st method is used to characterize and label the Connectorized D-fiber. dB compares each of your connectorizations.
   2. * I could typically get ~3dB SMF to DF with the blue spool of fiber. Try to get better connections.
   3. The following diagrams show the general setup for testing:
   4. Diagram #1:
      1. -This setup allows us to label the loss of connectorized D-fibers consistently and allows for easy comparisons.
      2. -Always use a patchcord to protect the equipment.
      3. -SMF stands for Single Mode Fiber. This fiber has a large(r) circular core, while the D-Fiber (DF) has a small elliptical core. This discrepency between the dimensions is the cause of this loss.
      4. 1) Measure the power through the Patch cord first (call "initial power" or IP).
      5. 2) Compare with power through the patchcord and connectorized fiber (call it the "final power" or FP).
      6. 3) Equation: Loss = 10*log(FP/IP) [dB]
      7. 4) Label the connector with this dB.
   5. 
2. b) Measure D to D loss.
   1. This 2nd method is used to determine the specific amount of loss that occurs
   2. * I could get ~1.8dB DF to DF. Try to get better connections.
   3. The following diagram allows us to measure the loss of 2 connectorized D-Fibers.
   4. Diagram #2:
      1. -The bare fiber adapter is apt to be a major loss of power. But it is easy to use, and easy to overcome this barrier by taking measurements in multiple places.
      2. -D to D fiber connections are apt to have less loss than SMF to D because the dimensions of the core are matched up and more compatible.
      3. 1) Measure the power coming out of the patchcord (Initial Power or IP).
      4. 2) Compare with the power coming out at the second point noted below (First Coupler or FC).
      5. 3) Enter these values into the equation: BareFiber Loss = 10*log(FC/IP) [dB]. This is the loss due to that bare fiber adapter.
      6. 4) Couple the connectorized D-fibers together and measure the power at the 3rd point (Last Power or LP).
      7. 5) Enter the corresponding values into the equation: D2D Loss= 10*log(LP/FC) [dB]. This is the actual coupled D-fiber connectorization loss.
   5. 

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