Measurement of optical fiber attenuation

Attenuation or fiber loss is the loss of power suffered by an optical signal when it is travelling through an optical fiber. The different techniques employed for this are cut-back technique, optical time domain reflectometer (OTDR) technique, time domain fiber dispersion technique, frequency domain fiber dispersion technique, refractive index profile technique, fiber numerical aperture measurement technique, fiber diameter measurement technique and measurement of signal attenuation in a splice connecter technique. Cutback technique and optical domain reflectometer technique are the most important techniques. Cutback method is a destructive method where both input and output ends are accessed during measurement. The experimental setup consists of a light source, lens, monochromator (prism or grating), lock-in amplifier, beam-splitter, mode scrambler, cladding-mode stripper and a photodetector. Optical time domain reflectometer is not a destructive method. Here access to one end of the fiber is enough for the measurement. Working principle is analogous to that of RADAR. The experimental setup consists of a laser source, directional coupler, photodetector and fiber connector.