This guide covers what you need to know about IPC-A-640: the class system, key acceptance criteria, inspection requirements, and how it relates to other IPC standards. What is IPC-A-640?d suppliers of electrical construction services. Existence. Project: Date: Technician: Route Length: Fiber Type: Measuring Device: 1. Tier-1 / Attenuation Measurement (Standard Acceptance Measurement) 3. Tier-2 / OTDR (only if needed or requested) If the inline viewer fails, it will open the original. The Fiber Optic Association, Inc. They explain how to avoid common mistakes, clarify test reference methods, and provide visual guides.