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 CONNECTOR CONTAMINATION UNDERSTANDING PRIMARY AND SECONDARY FIBER OPTIC CONNECTOR CONTAMINATION Advancing the Standards to Best Practices Number-2 in a Series Written by: Edward Forrest Abstract: To study The Sciences of Cleaning, students are taught three tenets: 1.) What are the debris, 2.) Where is it located, and 3.) What are the best means to remove it. (a) Additional subsets include knowledge of material substrates that might be damaged by the cleaning process and this is evaluated by test. Essential to successful soil removal, is the understanding of environmental, health and safety standards that impact the end result. For fiber optics, before the first standards were established, an inspection may have been performed using a jeweler’s loupe, then a direct view microscope that, improperly used, could cause eye damage. (b) THE CORE OF THE MATTER It is thought that early fiber optic inspection devices were “limited’ by 100x magnification. The first image, is a digital photograph of a complete 2.5mm end face. This is a three-dimensional view of what is often regarded in two- dimensional ‘diameter’. Image 1: End Face viewed by RMS-II digital photography. US Patent 10,578,847 Image-2 is end face viewed at 100x magnification by a conventional video scope. The circled area (1,2) is the diameter as currently standardized. It is the only surface area required to be cleaned. Noted in both images is debris outside of this surface area defined by IEC 61300-3-35. Image-1/2 suggests a recharacterization to five zones. Extensive research and practical experiences prove unseen debris may cross-contaminate. Because it is not seen, and, not considered, it is not removed. Understanding debris in Zone-4 (the total horizontal) and Zone-5 vertical surfaces is essential to future proof deployments. Over the last twenty years, inspection has evolved to higher levels between 200x and 400x. The higher the magnification, the less of the actual surface is seen. Image-3 is the same connector as viewed at 400x. Existing standards require cleaning the surface as noted within the IEC area (2). This is an important first-step; it is also a minimum requirement. (c) These images, from three different inspection devices, portray the ‘core’ or transmission fiber. No matter single mode or multimode, one fiber or multiples, direct contact or expanded beam, the prudent trainer, marketer, researcher and craftsperson accepts the three-dimensional nature of connector surfaces and plans cleaning methods and procedures accordingly. Multiple cleanings of the same surface will not resolve insertion loss, reflectance or misalignments. Always consider other sectors of the connector including alignment sleeves and adapters. PRIMARY AND SECONDARY CONTAMINATION     6 | highTECH NEWS | NOVEMBER/DECEMBER 2022 Likely you have seen this graphic: the surface area as defined by IEC 61300-3-35. This is the area of “PRIMARY CONTAMINATION”. Debris removal from this ‘Primary Surface’ area is critical. Each fiber is characterized in this way. Although defined and trained by IEC 61300-3-35 and multiple other standards(d), I consider this as a minimum requirement to best practice. Equally-critical are “Secondary Surfaces”. These are surfaces outside the field of view of IEC “Zone-D” in an approximately 250-400-micron diameter around the ‘core’ fiber(s) or IEC “Zone-A”. Continued on page 7  

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