Dense waveguide division multiplexers implemented using a first stage fourier filter

A dense waveguide division multiplexer for demultiplexing an optical signal into a plurality of individual channels at various wavelengths, comprising:

• a first stage comprising a Fourier filter for receiving said optical signal having said plurality of individual channels at various wavelengths and for demultiplexing said plurality of individual channels onto a plurality of first stage output paths with first passbands;
• and
• a second stage comprising a plurality of Mach-Zehnder filters, wherein each said Mach-Zehnder filter is connected to a respective said first stage output path of said first stage Fourier filter for demultiplexing said channels received on said first stage output path onto a plurality of second stage output paths with second passbands.

A dense waveguide division multiplexer for multiplexing a plurality of optical signals at various wavelengths into an optical signal, comprising:

• a first stage comprising a plurality of Mach-Zehnder filters, wherein each said Mach-Zehnder filter is configured for receiving said plurality of optical signals at various wavelengths for multiplexing said plurality into bands onto a plurality of first stage output paths with first passbands, each output path corresponding to one of said Mach-Zehnder filters;
• and
• a second stage comprising a Fourier filter having an input path connected to each of said first stage output paths for receiving said bands and for multiplexing said bands onto second stage output path with second passbands, wherein said second passbands are narrower then said first passbands.