QUESTION: I have some pre-angled 24-fiber single mode mpo connectors that are producing good geometry.
However, with my current process I am using a “Multimode” non-angled fixture to effectively remove the epoxy in the 1st step.
Then, I am removing the ferrules and re-inserting them in an angled fixture to complete the rest of the remaining steps in the process.
Is this a necessary procedure with this type of connector?
ANSWER:
The short answer:
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Using the PC fixture, as you describe, is a common method, many do the same. Though not very efficient, it is a “tried and true” method.
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You CAN eliminate the PC fixture, but need to make sure epoxy bead is fully removed (so that none remain on the final product, which should have angle cut across about 90% of the ferrule surface, not all the way) and scribing processes are solid.
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Best option, if available, would be to use Pre-Angled ferrules
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Quicker polishing times—–MUCH quicker than using PC fixture to remove epoxy
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Less material needs to be removed from the ferrule—-thus preserving original end-face hole dimensions and locations (and preserving optimum optical performance).
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The long answer: Using a PC plate to first remove epoxy, and then changing to APC plate to complete the angle-generation and polishing, is a common way to polish these ferrule.
The risk with this (besides being labor-intensive) is removing too much material from the ferrule during the epoxy removal step—-you have to take care to not remove too much material, as the more you polish down, the less fiber holes will meet intended dimensions: The holes molded into the ferrules may very well not be consistent throughout the length of the ferrule. If you can visualize a hole that is not perfectly perpendicular to the ferrule end-face, you can see that the more material you remove, the result will be a fiber center moving more and more away from intended location.
This is one reason it is preferred to use pre-angled MT ferrules for APC application, if possible. Less ferrule material needs to be cut away. Not only do you save production time of loading into two fixtures, but you very likely improve performance (as there’s less chance for the holes at the ferrule end-face surface will deviate from their original, molded positions).
But—you don’t have pre-angled MT ferrules. So, yes—–using the PC plate first is reasonable. Is it “necessary”? Well, the goal of using the PC plate is to remove all the epoxy. If you can reduce the “footprint” of the epoxy bead so that you can remove it on the APC fixture while you generate the angle—–then you wouldn’t need to use the PC plate. (so the angle generation will also remove the epoxy). However, reducing the epoxy bead footprint likely also means reducing epoxy bead support of the fibers——-so you’d increase risk of fracturing fibers, since they’re less protected by epoxy bead. So you’d need to be careful with this option—-keep track of fiber crack / fracture failures, make sure there’s no significant increase.
Some people only use the APC fixture, and just apply very small amount of epoxy on the end-face. The thinking is that while this would increase chance of end-face cracks, the fact that we’re then going to cut an angle across the fiber section (removing quite a bit of ferrule material) is insurance that cracks won’t be a problem——it’s unlikely the cracks would propagate down the fibers so far.
We are always available by phone and email if you would like to discuss in more detail or if any clarification is needed at 508-992-6464 or sales@focenter.com
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