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End Face Geometry | Fiber Core Dip | Geometry Limit Parameters | MT Coplanarity

Minus Coplanarity (or Minus-Side Coplanarity) is one way to describe how “flat” or “co-planar” an array of fibers is. To guarantee the minimum optical performance requirements of the telecom world, it is vital to make sure that all fibers in a mated pair of connectors will have good contact. It is intuitive that if all fibers of both ferrules are exactly on the same horizontal plane, then all fibers will likely mate well when connected thus, coplanarity is achieved.

MT Interferometer GL16 Norland Products
MT Array Fiber View (Interferometer)

If you have ever tried to polish an MT ferrule, you know it is impossible to polish an array of fibers to EXACTLY the same heights. There will always be some deviation in height between fibers in the array. When the fibers and ferrule are mated, and under load, they undergo a degree of compression/distortion that allows for sufficient fiber-to-fiber contact to be achieved, as long as the fiber height variation is not TOO much. How much fiber height variation is “too much”? These are other characteristics that the standards bodies attempt to define (see IEC 61755-3-31:2015).

In the beginning, the fiber height variation specifications set forth by IEC (ref# IEC 61755-3-31:2015) involved only the max-min heights of all fibers and the height differences between adjacent fibers. Recently, Minus Coplanarity was added to the specification. Minus Coplanarity is simply the distance between the lowest fiber and the “best-fit plane” through the array of fibers (also called the “fiber line”). It is a measure of fiber height variation within an array of fibers. A lower number is better, with a value of “0” indicating the theoretical ideal that all fibers are EXACTLY the same height.

Mesurement Performance
minus coplanarity multi-fiber

After understanding what Minus Coplanarity is, then you will have a better focus on what you need to address if your product fails to meet the industry specification. Unfortunately, there is no one answer to that question since results vary significantly depending on your supplier of materials (ferrules and fiber), polishing consumables (lapping films or slurries), and, mainly, your polishing process (pressures, speeds, and times). Generally, fiber height variation increase as overall fiber heights increase. The lower your overall fiber height, the lower your fiber variation, and thus Minus Coplanarity will be vice-versa. Thus, if you have difficulty meeting Minus Coplanarity specifications, consider adjusting your process to lower the overall fiber heights across the array. Usually, this is a relatively simple adjustment that requires minimal changes to only one step of the existing polishing process. If you prefer to keep overall fiber heights high but struggle to meet Minus Coplanarity specifications, you’ll likely need to address the phenomenon of “profile rounding,” where the edge fibers (fibers #1 and #12 in a 12-fiber array) typically have the largest difference in heights from their adjacent fibers. Such variation is usually the major contributing factor to poor Minus Coplanarity measurements. Improving the heights of the edge fibers while maintaining the heights of the remaining fibers in the array will likely require much more comprehensive and complicated changes to your polishing process.

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Automated Connector Polisher with Touchscreen Technology & ASR Automated Stub Removal

With the ACP24/96, you can automate polishing times, pressure, & motor speeds for each step. Complete polishing procedures are stored inside the ACP24/96 to save time and ensure repeatability. Create, save, and recall custom polishing procedures for custom jobs. Polishing Procedures can be saved to a computer for easy backup or transferred to another ACP24/96.

The ACP24/96 utilizes our figure 8 polishing pattern found in all our MCP lines of polishers and is compatible with all MCP24 and MCP48 polishing fixtures.

The ACP24/96 includes the ASR System for automated stub removal. No more removing fiber stubs by hand. ASR works with Nanometer Tech’s polishing fixtures, reducing the need to purchase special fixture plates.

Nanometer Fiber Optic Polisher

With the ACP24, you can automate polishing times, pressure, and motor speeds for each step. Complete polishing procedures are stored inside of the ACP24 to save time and ensure repeatability. Create, keep, and recall custom polishing procedures for custom jobs.  Save polishing procedures to a computer for secure backup or transfer to another ACP24.

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