In this communication we summarize the main characteristics of three optical fiber systems, namely HEXAFLEX, HEXAFLEX-II, and 2D-FIS, developed for performing simultaneous bidimensional spectroscopy of extended objects. They have been used at the 4.2m William Herschel (WHT) and the 2.5m Nordic Optical Telescope (NOT), which are sited at the Observatorio del Roque de los Muchachos. These systems have been used to observe the circumnuclear regions of several Seyfert galaxies. They show clear advantages over other instruments based on more classical techniques, at least for these complex objects of small angular size on the sky. Some examples will be given to illustrate this.