An optical time-domain reflectometer, OTDR, apparatus is configured to measure a backscattered trace of a fiber link under test (FLUT). The OTDR apparatus includes at least one photo diode adapted to detect an optical signal reflected from points along the fiber link under test in response to an optical test signal generated by a laser of the OTDR apparatus and supplied to the fiber link under test. The reflected optical test signal is attenuated or amplified automatically such that the power of the optical signal received by the photodiode is limited to a predetermined power range.