How many methods are included in standards for setting the OdB reference for loss testing?

• A. One
• B. Two
• C. Three
• D. Four

Answer: (C)

The OdB reference for loss testing is defined using three established methods. One uses a traceable absolute power reference to calibrate the measurement so loss is computed from known inputs and the measured output. A second method relies on a stable reference path or fixture to set a baseline, with unknown losses determined by comparing against that baseline. The third method is the cutback (or substitution) approach, where loss is found by comparing measurements from two different lengths of the same fiber, canceling out variations in the source and detector. These three approaches cover different practical setups and help ensure accurate loss measurements across varying laboratory and field conditions.