Last Updated: April 13, 2022
View a training demonstration of How to do Geometry Testing (Interferometer).
After polishing, there are a series of tests typically done: geometry testing, insertion loss and return loss testing. And then a visual quality check of the end face of the fiber and ferrule. We recommend the use of an interferometer for your process qualification, for designing your process to tuning it to the industry standards that you’re trying to achieve, and for an ongoing verification of that process, whether it be in a small sampling basis, or on a per plate basis.
In some cases, your customer will require that you provide geometry testing 100% for your connectors. You may or may not need to produce a test report or at least save your geometry report in the database.
This particular interferometer is called the DORC ( Direct Optical Research Company), and is a non-contact interferometer. It’s automated focused so it’s very simple and quick to use, the operator would open up the fixture, unlock the chuck, place the chuck into position, and go up to the measure button, and do a left mouse click. You can see the fringes are already autofocusing. There is a range of criteria on the right hand side that are not visual to you right now. It is highlighting the most important aspects of geometry for this particular style of connector, which is a physical contact style connector.
The three most important things we’re checking are Radius of Curvature (which is how flat or how radius or steep this spherical dome is on the end of the ferrule), Apex Offset would be the second criteria that is describing the center of the fiber and the center of the fringe pattern, and it’s measuring the offset of those two. Theoretically, we would like the center of these fringes to be the center of the fiber. This would mean the peak of the dome would be centered onto the fiber. In a perfect world Apex Offset would be zero. The third item we’re checking, not in any order of importance, is the fiber height, which is how far above or below the surface of the ceramic that the fiber has been polished.
There is a range of default criteria entered into this interferometer already that just happens to be Telcordia GR 326. As you can see, there is a global pass fail here where it says that all the requirements have been passed, or have been met. So we know that at least the geometrical part of the polishing process was successful.
If you did not get the result that you desired fiber optic center can work with you to fine tune your process and to tailor it to your needs or to your customers needs.