A Wavelength-Selective Multiwavelength Ring-Assisted Mach–Zehnder Interferometer Switch

Abstract

Wavelength-selective switches have been proposed for datacenter use to enhance the scalability of their networks to help in meeting ever-increasing traffic demands. We have previously demonstrated a 4 × 4 ring-based crossbar silicon photonic switch in which each cross-point contained three ring pairs to partition the free spectral range (FSR) into three equal regions to reduce wavelength tuning range per ring pair—thereby reducing both the tuning power consumption and stress on the rings—while maintaining full routing flexibility. However, the question of scalability remains for such a crossbar switch in which 96 signal pads—one routed to each ring—are required to fully control it. In this article we present a 4-port silicon photonic ring-assisted Mach–Zehnder interferometer (RAMZI) switch with multiple-sized rings per switching elements in a Benes network configuration to reduce the number of electrical pads required to 36 signal pads for the equivalent number of wavelength-selective switch elements per switch cell. The switch is 500 μm × 3 mm in size and is packaged on a custom PCB. Another advantage the RAMZI switch has over the crossbar switch is that the loss through the switch is not path-dependent due to its balanced path configuration. In the crossbar switch, the difference between the shortest and longest paths is 2(N − 1) switching elements. Finally, we present results from the fabricated switch and the outlook for further scaling of the switch architecture.