We demonstrate a novel photorefractive device for adaptive demultiplexing over a very broad frequency range. Our device, shown in Fig. 1, requires very little a priori knowledge about the signal channels. It provides spatially fixed outputs for arbitrary carrier frequencies and carrier separations ranging from kilohertz to hundreds of terahertz. The device is a multimode ring resonator containing two photorefractive crystals, which is pumped, by a multimode fiber input signal. The resonator self-organizes through competitive and cooperative mode interactions such that different pump frequencies provide gain to spatially separate modes.1 Initial results using a carrier separation of 160 MHz show an output contrast ratio better than 5 to 1.
© 1991 Optical Society of AmericaPDF Article