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

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 Beneš 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.