Determination of the amplitude-frequency characteristics of W-type fiber waveguides

The results are given of theoretical and experimental investigations of the amplitude-frequency characteristics of fiber waveguides obtained using continuous optical radiation modulated by a microwave signal. A simple analytic expression is derived for the transfer function of an ideal fiber waveguide when a Gaussian light beam is coupled in and the numerical aperture of the fiber is considerably less than unity. The results are given of experimental determinations of the amplitude-frequency characteristics of quartz multimode fiber waveguides with a W-like profile of the refractive index, obtained in the modulation frequency range 800–1250 MHz. The amplitude-frequency characteristics determined in this way are compared with calculated results.