Microoptical modulators and switches for multimode fiber applications

External modulators and switches for multimode fiber transmission systems are required for a plenty of applications in optical metrology and communication systems. We show that a confocal arrangement of microlens arrays with certain filter elements in the common focal plane of the arrays, which are moved with the help of piezoelectrical actuators, is a very simple and flexible concept to meet the needs of a number of very different applications. The focal length, lens pitch and width of the arrays have to be chosen properly. We discuss which optical elements (collimation optics, microlens arrays, focussing optics) are required for certain applications. We present experiments for an intensity modulator.