A high-speed tunable optical filter using a semiconductor ring resonator for photonic packet switch

Large-capacity photonic packet switch using the wavelength division multiplexing (WDM) technology is proposed. In this switch, the optical buffers, consisting of the fiber delay lines, are shared in many input ports by using the WDM. Furthermore, to reduce the number of optical buffers, the speed-up effect in the optical switch part is investigated. A high-speed tunable optical filter incorporating a semiconductor ring resonator is a key device in the proposed packet switch because many optical filters are used. Optical ring resonators should be possible to fabricate them at a low cost because of their simple structure. To achieve a wide tuning range we designed a double-ring structure, in which two ring resonators are connected in series, and fabricated it using the InGaAsP-InP material system. This device exhibits a total free spectral range (FSR) of 1.7 THz and contrast ratio of 9.5 dB. The ring radii are 25.2 and 17.8 mu m, which correspond to FSRs of 340 and 425 GHz, respectively. The switching time of the device is 2.5 ns.