As fiber connectivity continues to advance and address the need for next-generation transmission speeds to support emerging technologies, today’s data centers encompass more fiber links than ever before. And whether it’s a hyperscale, cloud, colo, or enterprise data center, multi-fiber push-on (MPO) connectors like the MTP have become the de facto interface.
Available in 8, 12, 16, 24, 32, 48, and even 72-fber interfaces, MPO connectivity is required for parallel optic transmission where data is simultaneously transmitted and received over multiple fibers. For example, high-speed parallel optic 400 Gig applications require 8-fiber connectivity with 4 fibers transmitting and 4 receiving at 100 Gb/s, or 16-fiber connectivity with 8 fibers transmitting and 8 receiving at 50 Gb/s. The IEEE 802.3 Beyond 400 Gig Ethernet Study Group has already identified objectives to support parallel optic 800 Gig applications over 16-fiber connectivity, with 8 fibers transmitting and 8 receiving at 100 Gb/s.
A key practice for today’s data centers that require maximum performance is to inspect and verify the quality, cleanliness, and geometry of fiber endfaces within connectivity—including multi-fiber MPOs with more endfaces to inspect. At the same time, there is also the need to improve the reliability, repeatability, and speed of the inspection process to keep costs down and reduce risk.
Why and What to Inspect
The quality, cleanliness, and geometry of fiber endfaces directly impacts how well connectors mate and how well light signals can transmit from one to another. Defects such as scratches and pits and dirt and debris fiber endfaces cause reflections and insertion loss that degrade network performance, while improper endface geometry can cause misalignments and air gaps that also increase reflectance and insertion loss. Poor endface geometry can even cause damage to fibers during mating—including those used within expensive transceiver equipment itself.
Industry standards define specific parameters for quality, cleanliness, and geometry. IEC 61300-3-35 uses specific grading criteria based on the number and size of defects and debris on a fiber endface to determine pass or fail. IEC 61755 standards define fiber endface geometry parameters such as radius of curvature (i.e., roundness), apex offset (i.e., core centricity), angle of polish (i.e., surface angle), core dip (i.e., how much the fiber core is recessed), and fiber protrusion height (i.e., how high the fiber core protrudes from the ferrule). When it comes to MPO connectivity, inspecting endfaces for defects, dirt, and debris is more complex since each fiber endface within the array needs to be inspected. And when it comes to inspecting endface geometry, every fiber within the MPO array also needs to be compared to all other fibers within the connector. For example, IEC standards specify protrusion height for each fiber in an MPO, as well and how each fiber compares to adjacent fibers and to all the other fibers within the connector (i.e., height differential).
Inspecting fiber endfaces for defects, dirt, and debris is common and best practice for all fiber connectors in any data center environment since it’s vital to performance. Inspecting endface geometry is a common practice in connector manufacturing and fiber assembly, and it has become best practice among large hyperscale and cloud data center providers (think Google, Amazon, and Facebook) and service providers (think Verizon and AT&T) who have a vested interest in ensuring proper endface geometry. Endface geometry inspection is conducted using an interferometer, either on a sampling or per connector basis. Repeatability and reproducibility in geometry inspection are integral to ensuring accurate results and improving the efficiency of the process, especially when inspecting on a sampling basis and/or inspecting multiple connector types. Due to the increased complexity of measuring fiber protrusion and core dip differential across multiple fibers in an MPO, it is recommended to use an interferometer calibrated with a high accuracy laser of less than 0.3nm.
Advanced Solutions for Advanced Technology
There is a variety of fiber inspection equipment available on the market for manually inspecting endface cleanliness—everything from simple hand-held microscopes to digital inspectors that provide cleaner, high-resolution images. While these might be adequate for inspecting a few fiber endfaces, the underlying problem with manual inspection is that it is always subject to human error—what one person sees versus another can vary based on skill, experience, eyesight, and even ambient lighting. The result is often inconsistent and inaccurate results. Even with a higher-end digital inspector, it’s common to manually inspect the same connector multiple times and get different results.
When it comes to inspecting fiber endfaces in today’s advanced data centers, manual processes are also extremely time consuming—especially when inspecting every fiber endface in multi-fiber MPO connectors. A single data center could be looking at needing to inspect tens of thousands of endfaces. Manual inspection of MPO connectivity therefore comes at a big cost with the potential to delay go-live goals, risk downtime, and not meet service level agreements. Data centers with high-speed, high-performance fiber links to support advanced technologies need far more advanced inspection equipment.
The good news is that CablesPlus has the solution! Our SmartCheck Auto-Analyze intelligent inspector is the answer to easily and quickly inspecting up to 72-fiber MPO connectors with superior repeatability. It automatically scans and analyze all endfaces of an MPO connector at once, detecting even the slightest defect and providing standards-based pass/fail results—completely eliminating any human factor. And it takes just 5 seconds to inspect a 12-fiber MPO! And if MPOs aren’t part of your network, it's also available in the AutoCheck single-fiber version.
For assembly houses, data centers, or service providers that need complete peace of mind in the quality of fiber endface geometry in either single-fiber or multi-fiber MPO connectors, our MT16/MTS automatic, non-contact fiber endface interferometer features a high accuracy 0.1nm laser for superior repeatability and reproducibility. Want to know more? Just contact us at firstname.lastname@example.org or 866-678-5852.