FO-4.3 revises fiber endface measurement procedure for single ferrule multifiber connectors

by Greg Sandels

TIA FO-4.3, the Passive Components Subcommittee, continues to meet the changing needs of the industry. Most recently, FO-4.3 overhauled and published FOTP 219A, “Examinations and Measurements-Polish Angle and Fiber Position on Single Ferrule Multifiber Connectors.”

FOTP 219A deals with the complexity of multifiber-ferrule, fiber-endface geometry measurements. The procedure analyzes the endface geometry of guide-pin-based multifiber rectangular ferrules and connectors. The primary areas of interest are the fiber position relative to the ferrule endface, either undercut or protrusion, and endface angle relative to the guide pins. The document also addresses core dip for multimode fibers.

A flat polished endface is desired on rectangular multifiber ferrules with the fibers protruding slightly and all in the same plane. In reality, the polishing process produces an endface with two different curvatures-one along the long axis and one along the short axis of the rectangular ferrule. The endface of the ferrule must be properly oriented relative to the guide pins and holes to achieve positive physical contact of the fibers.

FOTP 219A describes the measurement procedure including the equipment, measurement regions, and methods for analysis. The equipment required includes a ferrule holder, a positioning stage, and a 3D interferometer. The measurement regions are defined by four parameters: region of interest (ROI), extracting regions, fitting region, and averaging region. There are two additional parameters-core fitting region and annular area-which are particular to multimode core dip. The method for analysis is described in 12 steps utilizing the aforementioned measurement regions in order to accurately measure the fiber and ferrule geometry with repeatability. The details specified contain endface geometry in the x- and y-axes, individual fiber positions (undercut/protrusion), coplanarity, flatness deviation, and maximum core dip in multimode fibers. Annexes consist of formulas for calculating endface geometry, surface-angle sign convention, fiber-counting convention, coplanarity, and fiber-plane-angle determination.

FO-4.3 is also developing documents FOTP 1090, “Connector Seal Under Load”; FOTP 240, “Fiber Optic Cleaning System,” an FOTP for Adhesion Strength Test Methods; and a Technical Service Bulletin (TSB) on Connector/Cable Compatibility.

Greg Sandels is with OFS LLC and has been involved with standards since 1995. He is a former chair of FO-4.3.2, currently chairs FO-4.3, and a member of the U.S. delegation to IEC SC86B WG6 and JWG8. He may be reached at gsandels@ofsoptics.com.

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