Wavelength demultiplexer in multimode fiber that uses optimized holographic optical elements.

A single-transmission holographic optical element capable of broadband five-channel demultiplexing in multimode fiber is described. A holographic optical element demultiplexer combines a hologram on dichromated gelatin with a computer-generated hologram. A design of the demultiplexer with a nonspherical wave front based on ray tracing and the optimization technique perfectly permits five cross-talk isolations by reducing the aberrations of multiple focused spots caused by a recording-readout wavelength shift. Such a system has a channel separation of 300 µm (20 nm in wavelength difference) between adjacent fibers in an operating laser diode wavelength region of 0.8-0.88 µm. Experiments demonstrating the feasibility of this demultiplexer with a 780-nm laser diode source are presented.