. . . . . . . Connectorizing Fibers . . . . . . .
The following contains instructions of how to place a connector on a bare optical fiber
10 Steps to Connectorize a bare fiber:
- Parts of the Connectorizer
- The Connectorizer -top picture
- large washer
- Specialty chuck & little metal thing
- 1/2 coupler (for holding the connector)
- Hex screwdriver
- Actual connector pieces
- brass thing
- white jacket
- plastic tubing
- white shrink wrap
Step 1: Prepare fiber
- a) Strip (aka remove) the plastic jacket
- Using plastic gloves, strip about 4cm of the ends of the fiber using Dichloromethyl. Use thumbnail to remove the plastic jacket and expose the glass fiber underneath.
- b) Etch
- Place stripped end in 25% HF for 2-3 min. Rinse adequately and let dry.
- This actually helps the fiber fit through the connector. Verify that the length of the stripped fiber will fit through the connector comfortably. If you encounter a little bit of resistance, etch for 30 sec more. If you continue to push the fiber will break off in the connector and that connector will be ruined (they cost $4.25 each).
- c) Cleave
- Cleave off the tip of the fiber. Use a viewer to make sure you do not have any protruding glass on the surface ("hackles"). It needs to be as perfect as you can get. Use the cleaver that works for you.
Step 2: Place Fiber in Connectorizer
- *** IMPORTANT!! If you are putting connectors on both sides you need to slide the plastic tubing, shrink wrap, brass holder, and white thing on before putting the fiber in the connector. Otherwise your fiber will not have any protection.
- a) Insert connector
- Twist the connector into the coupler. Verify that the blue dot on the coupler (which is aligned with the key) is on the top.
- b) Place fiber in the specialty chuck
- Insert the fiber into the connector. Place the specialty fiber in the groove. Rest the fiber in the slit of the chuck. Secure with the metal strip. Be careful not to crimp the jacket on the edges of the chuck.
- c) Place the washer and screw in place
- But do not clamp down tight yet. You will still want to move the chuck around for aligning.
- d) Tape down remaining fiber
- There is plenty of room on the long metal plate of the Connectorizer. Prevent the rest of the fiber from snagging on anything.
Step 3: Align the Fiber Flat Side Up
- a) Focus the viewer
- Use the micrometers to move the objective lens forward until it just barely touches the end of the fiber. Make sure you can see the "D"- if not, move the other micrometers to center the fiber.
- b) Rotate Fiber
- Verify that the "D" is visible and that is is a good cleave. If it is not then remove from the connector and cleave again!
- Use the chuck to rotate the fiber until the D is flat side up and aligned with the blue dot.
- c) Screw securely into place
- Use the chuck to pull the fiber back until it is just barely sticking out of the end of the connector.
- You do not want it too far out or it may break off. If it is not out far enough you may have pulled it too far into the connector ferrule.
Step 4: Place in oven
- a) Turn on the oven
- Turn the knob to "ON" and close the door. Wait for it to heat up (~100C).
- b) Pull the objective away from the end of the fiber.
- The fiber holder may shift when the Connectorizer is moved. Make sure the objective is far enough away so that it will not break off the fiber tip.
- c) Place in oven
- Pick up the Connectorizer and place on the rack in the oven.
- c) Foil cover
- Since the door does not close (and it would heat up to incredible temps if it did. Leave the door open, but place a foil cover over the top.
Step 5: Glue & Cure
- a) Glue characteristics
- One packet of this adhesive is enough to connectorize quite a few fibers. However, the pot life only lasts about 4 hours. While the curing process for this adhesive is greatly accelerated by heat, it will cure with time as well. At the end of 4 hours you will be left with a chunk of hard orange-ish material. If heat cured it will be very red. It is also advisable not to get any adhesive on your skin or in your eyes. For more information consult the MSDS form for this glue.
- b) Mix the glue
- Remove the barrier between the solvent and the adhesive and mix until it has an even consistency and color. Cut off the end of the packet and squeeze a little bit out.
- c) Glue
- Open oven door and, using a toothpick, place a drop of glue at the opening of the connector. Do not touch the fiber (it may pull out). Let the glue wick into the connector. Close door, replace foil, and wait until adhesive is red (~10 to 15 min. if oven temp is 110C or higher).
- If adhesive is sucked into the connector it does not hurt to place more glue on so that you can see it when it turns red.
- DO NOT get any adhesive under the silver part of the connector. This makes the connector very difficult to use.
Step 6: Attach other parts
- a) Remove from oven ... HOT!
- Use the orange gloves to remove from oven. Close door to retain heat.
- b) Unscrew chuck
- Use the screwdriver. It is still hot!
- c) Remove fiber from chuck.
- Be careful and use the tweezers. Careful not to crimp the fiber.
- d) slide the plastic shield and brass thingy to connector end. Glue and cure
- Be careful not to use too much glue at this point, it only needs a little bit at the point of the connection. Do not get any adhesive under the silver part of the connector!
- e) slide shrink wrap over white protector and place over brass thingy.
- This does not really need to be glued. The white holder will stay very securely. Use the heat gun to shrink the shrink wrap.
Step 7: Polish... Optional
- * This was part of the old steps. You can still use, but there may be the risk of breaking off the tip. We typically just try to get an amazing cleave, then not worry about polishing.
- a) Why polish?
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.
- b) Be careful!
- 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!
- c) 3 types of polishing paper
- 5um (white)- rough polishing. Used to grind down excess fiber sticking out of the connector.
- 1um (pink)- finer polish. Middle step to even out roughness caused by the 3mm polishing paper.
- 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.
- d) Polishing steps
- Place the puck on the 5um paper. Gently place the connectorized fiber into the hole of the puck. Do not push down, this will cause fiber to break. Let the connector just rest inside of the puck. With fingers on the puck. Remember-no pushing on the connector itself. Move the puck/connector in a figure-8 pattern across the polishing paper. Continue, periodically checking on how much the tip is worn down.
- When the exposed tip of the fiber is just barely visible change polishing paper to the 1um paper. Polish with puck in figure 8s until connector seems to move more smoothly
- Change polishing paper to .3um and continue to polish in figure 8s.
- e) Clean off polishing dust by using the Drag and Drop method.
- 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.
Step 8: Test the quality of your connection.
- a) Measure Single Mode Fiber (SMF) to D-fiber loss.
- This 1st method is used to characterize and label the Connectorized D-fiber. dB compares each of your connectorizations.
- * I could typically get ~3dB SMF to DF with the blue spool of fiber. Try to get better connections.
- The following diagrams show the general setup for testing:
- Diagram #1:
- -This setup allows us to label the loss of connectorized D-fibers consistently and allows for easy comparisons.
- -Always use a patchcord to protect the equipment.
- -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.
- 1) Measure the power through the Patch cord first (call "initial power" or IP).
- 2) Compare with power through the patchcord and connectorized fiber (call it the "final power" or FP).
- 3) Equation: Loss = 10*log(FP/IP) [dB]
- 4) Label the connector with this dB.
- b) Measure D to D loss.
- This 2nd method is used to determine the specific amount of loss that occurs
- * I could get ~1.8dB DF to DF. Try to get better connections.
- The following diagram allows us to measure the loss of 2 connectorized D-Fibers.
- Diagram #2:
- -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.
- -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.
- 1) Measure the power coming out of the patchcord (Initial Power or IP).
- 2) Compare with the power coming out at the second point noted below (First Coupler or FC).
- 3) Enter these values into the equation: BareFiber Loss = 10*log(FC/IP) [dB]. This is the loss due to that bare fiber adapter.
- 4) Couple the connectorized D-fibers together and measure the power at the 3rd point (Last Power or LP).
- 5) Enter the corresponding values into the equation: D2D Loss= 10*log(LP/FC) [dB]. This is the actual coupled D-fiber connectorization loss.