Which of the following is not a feature of Optical Time Domain Reflectometers (OTDR)?

Optical Time Domain Reflectometers (OTDR) are primarily used for testing and characterizing fiber optic cables. They work by sending a pulse of light into the fiber and measuring the light that is reflected back, which allows for various assessments of the fiber's condition and performance.

Measuring transmission speeds is not a function of an OTDR. This device focuses on analyzing the fiber's characteristics through reflection patterns without directly measuring how fast data can travel through the fiber. In contrast, the other options align with the capabilities of an OTDR: identifying splice losses, performing fiber length measurements, and detecting physical defects in the fiber are core functionalities of this testing equipment. Each of these tasks helps determine the integrity and performance of fiber optic systems, which is critical for maintenance and troubleshooting.

Thus, option A is correctly identified as not a feature of OTDR, as it does not provide insights into the data transmission speeds of the fiber optic cables.