Densely Integrated Photonic 8×8 Broadcast & Select Space Switch for High-Capacity Interconnects

Optical interconnects bring fast and efficient data transfer to data centers and AI clusters. Optical switches can further boost this development by reducing network switch expenses with a significant reduction in power consumption. In order to build switches with a meaningful number of ports, increasing the density of large scale integrated photonic switch fabrics is a must. One density bottleneck are the SOAs, which requires a minimum spacing of 250 μm. This work shows the design, fabrication and characterization for a densely integrated 8× 8 photonic InP space switch using the broadcast-and-select topology. Experimental characterization confirms that an increase in SOA density by 4.2x has a limited impact on the optical performance. The measured on/off ratio is on average 53 dB, resulting in a low crosstalk. The fiber-to-fiber noise figure is 12 dB and the fiber-to-fiber insertion loss is 17 dB, which is a result of the short SOAs used on the chip. Compatibility with high-capacity interconnects is demonstrated using a four channel 100G LWDM transceiver, achieving a 1.25 dB power penalty and using a PAM-4 modulated single channel interconnect with a power penalty of 0.8 dB.