FOA Certified Fiber Optic Specialist, Splicing (CFOS/S) Practice Exam 2026 - Free Fiber Optic Splicing Exam Questions and Study Guide

In single-ended loss measurement, the reference side defines the baseline for all losses by what connects to the instrument on the launch end. If you observe more loss in one direction, the issue often lies with the reference interface—not the device under test—so you want the reference to present the same, clean mating as the patch being measured. Attaching a connector to the reference ensures that the reference interface matches the patch cord’s connector type, providing a known and repeatable launch condition and canceling out or compensating for directional differences caused by the reference connection. A power meter or a source on the reference would not fix the directional mismatch, and a reference table on the patch isn’t a standard way to correct the measurement.