An Optical Time-Domain Reflectometer (OTDR) is used to test the integrity of fiber optic cables by sending pulses of light into the cable and measuring the reflected light. It can detect breaks, bends, and splice losses in fiber. For copper cabling such as Cat 6, a cable tester or certifier is the proper tool to measure decibel loss (attenuation) along the length of the cable. A cable tester can ensure that the cable is functioning correctly and can measure the signal loss, which is measured in decibels. A spectrum analyzer is used to view the frequency spectrum and is more applicable to wireless network analysis. A multimeter can measure electrical properties but is not designed to quantify decibel loss of data signals on network cables.