Reference cables must match the fiber size and loss specification.

• A. Fiber Size & Fiber Type
• B. Connector Type
• C. Fiber Size & Loss Specification
• D. Fiber Size & Jacket

Answer: (C)

Matching the fiber size and loss specification when using a reference cable ensures the baseline optical behavior is the same as the fiber under test. The core diameter (fiber size) determines how light couples and propagates, including mode shape and potential coupling losses. If the sizes don’t match, the reference cable can introduce extra or different losses just from how light distributes itself, skewing measurement results. The loss specification sets how much attenuation the reference itself contributes; if this doesn't align with the tested fiber, the reference portion will add or subtract attenuation that isn’t part of the device or connection you’re evaluating, leading to inaccurate readings. Keeping both parameters the same makes the reference a valid, neutral baseline, so any measured loss truly reflects the component or splice under test rather than differences in the reference cable. Other aspects like jacket or connector type can matter for physical compatibility, but they don’t guarantee the optical behavior needed for accurate reference measurements in the same way size and loss do.