This system represented our first effort to test our jacketed fiber without using the destructive, slow, and non-repeatable cutback method.

The initial concept came from a simple premise: instead of measuring the end emission of a few points along the fiber, what if we measured the side emission at many points? While this test method may not be as accurate due to impurities in the jacketing and fiber itself, I relied on adding more points to strengthen the trends and data.

The first iteration of this test method only consisted of a cardboard box with my phone camera poking through a hole. This dark box allowed us to isolate the light escaping the fiber. We then moved toward an Allied Vision camera which was enabled through a python script I wrote leveraging my experience in computer vision to edge detect the fiber and plot the light output along its length.

The final design of this fixture included a large box built by another engineer on the project. I was fully responsible for the script and image capture as well as analysis of each fiber. Additionally, I designed and built the pulley system on the bottom panel, which allowed us to set a rough position for the fiber and pull 5m portions through.

The script took about 1.5 minutes to run and measured 5m at a time. This was a 20x increase on the cutback method which took over an hour to measure 10m. We tested portions of the fiber with both methods and determined that the fixture’s accuracy was well within the tolerance we required for the fiber.

This test method was an extremely useful intermediate method between the cutback testing method and our eventually photodiode-encoder method; we were able to test over 90 30m fiber spools and setting combinations to isolate potential issues in the manufacturing process.