What should an OTDR operator do if distance measurement does not match cable jacket markings?

When an OTDR operator encounters a situation where the distance measurement does not match the cable jacket markings, adjusting the index of refraction settings is the appropriate solution. The index of refraction is a critical parameter used by the OTDR to calculate the distance to events along the fiber optic cable.

If the index is set incorrectly, the OTDR may misinterpret the time it takes for light to travel through the fiber, leading to inaccurate distance readings. By changing the index of refraction settings, the operator can ensure that the OTDR accounts for the specific characteristics of the fiber being tested. This adjustment can help align the distance measurements more closely with the physical markings on the cable jacket, providing accurate assessment and diagnostics.

Other choices, such as replacing the fiber or recalibrating the OTDR, may not directly address the immediate issue of the mismatch in distance readings. A full system reset may not change the fundamental settings that impact distance measurement. Therefore, modifying the index of refraction is the most effective and relevant response to the discrepancy observed.