Which parameter cannot be measured by optical time domain reflectometers (OTDRs)?

Optical Time Domain Reflectometers (OTDRs) are designed primarily to analyze and characterize fiber optic cables by sending pulses of light into the fiber and measuring the reflections that return. One of the key parameters that OTDRs measure includes fiber attenuation, which reflects the loss of signal strength as light travels through the fiber. They can also determine connector loss when a splice or connector leads to a reflection, helping technicians identify the integrity and performance of connections. Additionally, OTDRs are particularly useful for locating faults or breaks in the fiber because they can measure the distance to these faults based on the time it takes for the light signal to return after reflecting off a break or other imperfections.

In contrast, OTDRs are not equipped to directly measure transmitter or receiver power. This is typically performed with other optical measurement tools such as optical power meters, which precisely gauge the light levels at the output of a transmitter or the input to a receiver. Therefore, while an OTDR offers valuable insights into the performance characteristics of fiber optic links, it cannot evaluate the power levels of the optical signals being transmitted or received. This limitation is the reason why the measurement of transmitter and receiver power is not a function of OTDRs.