Measurements of Intermodal Dispersion In Graded Index Optical Fiber


The aim of this research is to examine experimentally the laser pulsetransmittance in graded index optical fiber. However attention is paid on the evaluationof intermodal dispersion. Four signals (λ=680nm and power= 0.1mW) of differentfrequencies (138.889, 277.778, 645.16, and 1369.863 Hz), of pulse widths (7.2, 3.6,1.55, and 0.73 ms) respectively are sent through a 400m multimode graded index fiber.A p-i-n detector is used to receive output signals. Intermodal dispersion has beennoticed and the pulse width broadening for each frequency is recorded. They are (7.22,3.61, 1.555, and 0.732 ms) that lead to frequencies of (138.504, 277.008, 643.08,1366.120 Hz) respectively. That change in frequency has to be taken into accountwhenever fiber optic dependence communication, guidance, or control systems areconsidered.