Optical wavelength division multiplexed multiplexer/demultiplexer for an optical printed circuit board and a method of manufacturing the same

A method of forming an optical multiplexer/demultiplexer for an optical printed circuit board, the method comprising:

• on a support layer forming a first optical polymer waveguide for carrying a wavelength division multiplexed optical signal;
• on the support layer forming plural optical polymer second waveguides for carrying components of a said wavelength division multiplexed signal;
• during said step of forming the first and/or second optical polymer waveguides determining the relative location of a separator/combiner for separating/combining the optical signals wherein a common mask is used to define the waveguides and the relative location of the separator/combiner,
• wherein during the step of forming the first and/or second waveguides the separator/combiner is also formed, and
• wherein the separator/combiner is formed of the same material as that from which the first and plural second waveguides are formed.