Abstract

Wavelength division multiplex (WDM) techniques are generally regarded as a key element in emerging broadband networks. Amongst the many passive device technologies being considered for wavelength selection, the arrayed-waveguide grating (AWG) [1] has multiplexing, demultiplexing and routing functionality. However, the non-rectangular passband characteristic of an AWG, due to die multiple convolution of input and output waveguide modes with the classical echelon transfer function of the waveguide array allows only a minimal wavelength-shift tolerance. In this paper we show how synthetic aperture techniques [2] can be employed to provide significant passband broadening and flattening. Figure 1 shows two possible geometries to achieve the desired phase control: either (I) profiling within the arrayed-waveguide, or (II) a geometric quasi-cycloidal deviation from the Rowland circle at the fan-out section.

© 1998 IEEE