Mode coupling effects in a graded-index fiber cable.

Mode coupling coefficients and impulse response in graded-index fibers are investigated both experimentally and theoretically. Mode coupling coefficient measurements at lambda = 1.27 microm are made for fibers before and after cabling. The magnitude variation of the mode coupling coefficients due to cabling is found to be relatively small, and the behavior of the coefficients against the principal mode number remains almost unchanged. Slight decreases of 0.06 dB/km in transmission loss and 1.1% in 3-dB bandwidth have been observed (on the average) due to cabling, and the results are well explained theoretically using the experimental mode coupling coefficients. The length dependence of the 3-dB bandwidth changes little due to cabling.