Cross-order arrayed waveguide grating design for triplexers in fiber access networks

An arrayed waveguide grating (AWG)-based multiplexer has many advantages, including small size, high reliability, and low cost. The commonly used wavelengths for triplexers in fiber access networks are 1310, 1490, and 1550 nm. Because of the wide spectral range and very unequal wavelength spacings, it is difficult to produce satisfactory results with a conventional AWG design. A novel cross-order AWG design particularly suitable for triplexers is presented. The spectral periodicity of the grating is utilized so that the first wavelength works at a different diffraction order and is transposed to a wavelength that is approximately in the middle of the second and third channels. This results in a reduced free-spectral range requirement and more equal distances between the output waveguides. Consequently, the AWG can operate at a higher diffraction order with a smaller overall size, compared to the one designed by conventional methods.