Enhanced functionalities for AWGs

Two new arrayed waveguide grating (AWG) architectures are presented, for flat-top multiplexing and for the generation of Nyquist sinc-shaped optical pulses. We demonstrate that an AWG, with a number of grating arms double with respect to a conventional configuration, and an input y-branch, is equivalent to a synchronized router, composed of a Mach Zehnder interferometer (MZI) and an AWG in tandem. The proposed device is more compact, with reduced losses and dispersion sensitivity, and a more flat-top frequency behavior. To generate and process a sinc-shaped optical pulse train, a new AWG is used, that implements the fractional Fourier transform (FrFT), followed by a dispersion compensating fiber (DCF).

We use the time-lens effect and the chirped modulation introduced by a fully passive FrFT-AWG to optically transform a sinc-shaped transfer function into a sinc-shaped impulse response, and vice versa. Detailed AWG design guidelines for wavelength division multiplexing (WDM) and orthogonal frequency division multiplexing (OFDM) multiplexing are also provided, evidencing the different roles played by the two slab couplers, in a signal processingframework.