In this paper a novel microwave photonics beamformer device concept, for single side band (SSB) 40 GHz modulated signals, is presented. The proposed device comprises tunable lasers, flat-top arrayed waveguide gratings (AWG), a Mach Zender Modulator (MZM), an all-pass ring resonator and photodetectors. The device can be produced as a photonic integrated circuit. The signals from the lasers (one for each beamformer radiant element) are multiplexed by the first AWG, modulated, and passed through the all-pass ring resonator. The AWG channel spacing and the ring resonator Free Spectral Range (FSR) are both set to be equal to 100 GHz. The signal is demultiplexed by a second AWG and finally photodetected. By tuning each laser within its corresponding AWG passband, the phase difference between the optical carrier and the 40 GHz microwave modulated signal for each beamformer element can be controlled. The difference is determined by the phase response of the all-pass ring resonator. A critical part of the design is the alignment between the resonances of the ring resonator and both AWGs, but this can be alleviated by using a single AWG in fold-back configuration. The power provided to each beamformer element is different due to the intrinsic non-uniform losses of the AWGs and the ring resonators, but this can also be solved either by properly setting the lasers power, or by means of additional optical amplifiers. The presented analysis is independent of the integration technology. In Silicon photonics, the AWGs and ring resonator can be produced, while the (hybrid) integration of lasers, modulator, photodetectors (and eventually amplifiers) is a challenge. The device can be monolithically integrated on semi-insulating InP technology.

Date Published: 17 May 2010
PDF: 8 pages
Proc. SPIE 7719, Silicon Photonics and Photonic Integrated Circuits II, 77191J (17 May 2010); doi: 10.1117/12.853778

Published in SPIE Proceedings Vol. 7719:
Silicon Photonics and Photonic Integrated Circuits II
Giancarlo Cesare Righini, Editor(s)