How do I measure the concentricity of, or tune, an APC connector?
The short answer is you can’t measure concentricity with an APC connector end-face. Producing tuned APC terminations comes down to technique. Concentricity can only be determined with a PC tip. So, usually an APC connector is selected with a non-pre-angled step-ferrule. It’s terminated then polished PC, typically only up to the D1 step, and then measured with a concentricity set up. After tuning, the ferrule base will be assembled into the housing. The rotational placement of the ferrule base (4, 6 or even 8 positions) provided by the tuning step will optimize the fiber center placement with respect to an ‘ideal’ connector. Afterwards, the APC polish is done.
It should be noted the measured value at the UPC point isn’t valid anymore because of the ferrule exit hole angle. During APC generation, considerable ceramic material (as related to the fiber and fiber core) is removed, and this offset alters the actually concentricity.
However, even though the UPC concentricity numbers aren’t ‘valid’, APC tuning is still done to minimize insertion loss. By determining the offset at the PC level, ‘tuning’ it so the fiber center is at the same spot as the OD center, selecting good ferrules (tight fit with the SM fiber), minimizing material removable during the APC polish, you can get a low connection loss; on the order of less than 0.05 dB.
Answered by AskFOC Technical Team November 27, 2017
Have a technical question for Fiber Optic Center?
Please email your question to AskFOC@focenter.com and we will respond ASAP.
In addition to replying, we will post your question and our answer here on the AskFOC page. Everyone remains anonymous when we post so feel comfortable asking your questions. You can also search to see if your question has already been answered in the FAQs section below.
- FOC Tips: cables hanging in existing masts vs. installing ducts in the ground - June 20, 2018
- Fiber Optic Center AskFOC: are there Standards on the amount of contamination for multi-fiber end-faces? - June 18, 2018
- FOC Tips: “transition point” where buffered fiber is stripped away to reveal the bare fiber - June 15, 2018
- Fiber Optic Center AskFOC: where can I get a little bit of Teflon? - June 14, 2018
- FOC Tips: dual asymmetric centrifuge - June 13, 2018
- Fiber Optic Center AskFOC: contamination of fixture affecting precision - June 11, 2018
- FOC Tips: cross sectioning and detailed failure analysis - June 8, 2018
- Fiber Optic Center AskFOC: is there a way to avoid wasted epoxy? - June 7, 2018
- FOC Tips: 2-stage heat cure - June 6, 2018
- Fiber Optic Center AskFOC: what are the key differences between copper and glass optical fiber we need to be aware of? - June 4, 2018