This invention provides a flat dispersion frequency discriminator capable of having a substantially flat dispersion with either a positive or negative dispersion along the spectrum region of the discriminator. The reflectors are positionable to direct an optical signal from any one of the fiber inputs to any one of the fiber outputs. In some approaches the negatively-refractive focusing includes negatively-refractive focusing with a transformation medium, where the transformation medium may include an artificially-structured material such as a metamaterial. Each of a pair of bracing assemblies is pivotally coupled to each of the support bar and the trailer. The first predetermined value is set so that if the amplitude of the audio signal exceeds the predetermined value and the gain of the gain control unit is not reduced, the amplitude of the amplified audio signal exceeds a predetermined acceptable range.