A document published by CommScope provides step-by-step guidelines for testing multimode and singlemode fiber-optic cabling systems in the field. It includes test procedures for systems with MPO connectivity as well as an appendix addressing the encircled flux launch condition, which CommScope points out is optional for field testing.
The document states, "IEC 61280-4-1 defines encircled flux to support testing of 50-micron multimode fiber solutions at 850 nm that are likely to operate at data rates at 1 G/s or higher. Although the standard was developed to support testing at the manufacturer, some test equipment providers are offering field encircled flux units. The unit could be incorporated within the test device, or as part of the test cord. At this time, CommScope does NOT require encircled flux testing in the field if mandrel wrapping is used." (Emphasis added.)
Despite the "optional" status of encircled-flux testing, CommScope's manager for training and technology Eric Leichter recently stated in a blog post, "For multimode optical fiber cabling, encircled flux is the latest improvement to be made for evaluating the loss performance of cable and assemblies in the factory ... Some misunderstand EF to be a compromise between LED and VCSEL testing." (Leichter may have been referring to this opinion and/or others like it.) Leichter continued, "The truth is that the encircled flux metric was based on obtaining the most repeatable measurements when evaluating typical 'critical' data links of the sort that would be used for applications seen and designed for today, such as 10, 40 and 100G Ethernet."
The document from CommScope, entitled "Structured Connectivity Solutions Field Testing Guidelines for Fiber-Optic Cabling Systems," is 25 pages in length and was published in August 2011 as an update to similar guidelines published in 2005. The document's introduction explains, "Systimax Solutions only requires testing of link attenuation for enterprise networks. While other fiber-optic cabling system parameters such as bandwidth are equally important, they are not normally affected by the quality of the installation and therefore, do not require field testing. This document describes how and where attenuation testing should be performed for enterprise systems." It also includes a section titled "Cable Plant Defect Detection and Resolution," which addresses causes and resolutions of optical-connection contamination.
