A scalable AWGR-based optical switching fabric and its scheduling method are presented. The switching fabric consists of three stages: two stages (first and third) of AWGRs interconnected by a second stage of optical space switches. The optical switching system is named ASA for the technologies used to construct the three stages: AWGR, Space switching, and AWGR. The first stage and third stage portions of the switching fabric comprise up to N N×N AWGRs (N inputs and N outputs) and the middle stage N N×N optical space switches, wherein N is an odd integer. This makes the switch's total port count N2. Each port can transmit up to N packets of different wavelengths simultaneously. Thus the total capacity of the switch is around (N3×bandwidth of one wavelength channel).