Intended institutions and users:
Physics education in Medicine
How it works ...
Before a glass fibre can be used in real application outside the laboratories, it has to be fixed to a connector. The entire process of stripping, cleaving, cementing and polishing the entrance window of the fixed fibre is termed as preparing of the fibre. Stripping means the removal of the protective plastic cladding of the fibre. This is done by so called Miller pliers. Cleaving means the defined breaking of the fibre in such a way that the face of it is perpendicular and of optical quality after the process. This can be achieved by slightly scratching the fibre by means of a ceramic or diamond blade when it is bent and exposed to a defined force in direction of the fibre axis. For this process a variety of tools are available. In a next step the fibre is supplied with a connector. For a particular fibre the right connector must be chosen. The ready cut fibre is dipped in one component of a two compound glue and inserted into the ferrule of the connector which already is filled with the second compound of the glue. After a while the fibre is bonded to the ceramic ferrule of the connector. The protruding fibre is scratched and removed. The connector is now ground and polished. By means of a fibre inspection microscope the connector is inspected if the face of the fibre has the desired optical quality.
In this workshop the hand grinding and polishing of optical fibre is introduced and trained. This method is useful in research labs or other places with occasional requirements.
Remove the cladding
Clean the fibre I
Clean the fibre II
Prepare bonding I
Prepare bonding II
Prepare bonding III
Slip fibre to connector
Scratch and break I
Scratch and break II
Clean prior inspection
The fibre is protected by an acrylic buffer coating which needs to be removed using the miller pliers. They are just a more precise cable stripper tool and acts in the same way.
Clean with Isopropanol and KIM wipes
This is a very important step and should not be skipped. A KIM wipe is moistened with isopropyl alcohol ...
The stripped fibre is cleaned.
If this step is skipped, small particle from the acrylic buffer may adhere at the fibre and will prevent to slip the fibre into the ferrule, since there is only space of 1 µm.
Now we are testing if the fibre is sufficiently cleaned. The fibre is inserted into the connector as shown in the picture on the left. There should be no perceptible resistance.
We remove the fibre from the connector and perform the next step.
Fill the provided syringe with a bit of the “bond”.
Insert the needle of the syringe into the connectors until it stops. Now fill the ceramic ferrule from the back side with the bond until a small drop of the bond appears at the tip of the ferrule
Put the connector aside and dip the fibre into the accelerator.
Slip the fibre into the ferrule until it stops. Wait a couple of seconds and the bonding process is finished.
The protruding piece of fibre needs to be removed. For this purpose the cleaving tool is used. It has as very sharp and hard tungsten blade. Slightly above the bluish bond bump set the blade and transverse it along the fibre. With a small radial push the fibre will break.
The protruding fibre has been broken apart and we are now ready for the next step.
An underestimated, but important part is the so called “air polishing”. During the breaking process the fibre might not been broken perfectly and may have sharp peaks. These undesired parts will be removed by the air polishing as shown in the figure above. The connector is moved while gently touching the polishing paper.
In the next step the polishing support is prepared. On top of the acrylic plate we add a few drops of water at that spot where the polishing paper shall be placed and fixed.
Take the polishing jig and place it onto the polishing paper. Insert the connector into it and start with gentle polishing movements following a shape of an eight. After ten or so movements the connector may be touched in addition and gently pressed down (gently).
After another ten movements the first inspection of the fibre takes place.
Before inserting the connector into the microscope clean tip of connector carefully with a moistened (Isopropyl alcohol) wipe.
Place the fibre connector into the ferrule holder at the bottom of the microscope. Look into the ocular while pressing the knob to illuminate the fibre. Turn the knurled knob and adjust the focus for a clear picture. If you see such a fibre face, you made an excellent job. There are no scratches and digs.