Low-Loss Reconfigurable Non-Blocking Optical Switching Network Based on Phase-Change Materials

Objective Mach. Zehnder interferometer (MZI)-based optical switches are widely integrated into data-center optical switching networks owing to their exceptional performance in terms of bandwidth and temperature sensitivity. However, conventional electronically or thermally controlled MZI optical switches exhibit disadvantages of volatility, high insertion loss, and substantial footprint, thus complicating the scaling of the switching network. Hence, this study introduces a novel low-loss all-optical switch and an optical switching network structure based on nonvolatile phase-change materials to facilitate the implementation of large-scale data-center optical switching networks. Methods We propose a 2x2 all-optical switch structure based on nonvolatile phase-change material Sb2Se3 and an MZI [Fig. 1(a)]. By optically reconfiguring the state of Sb2Se3 within this structure, one can realize switching between the cross and bar states of this optical switch [Figs. 1( b) and 1(c)]. The 2x2 optical switches were interconnected by optimized low-insertion loss-crossing waveguides [Fig. 4(a)] to form an 8x8 reconfigurable nonblocking optical switching network based on the Benes topology (Fig. 3). To minimize loss in the optical switching network, the 2x2 optical switch and cross-waveguide structures were optimized using the Lumericalsimulation platform. Results and Discussions We constructed an 8x8 low-loss reconfigurable nonblocking optical switching network to simulate and verify the functionality of reconfigurable optical switching using the Lumerical INTERCONNECT simulation platform. Initially, we analyzed the state of each 2x2 optical switching unit of single-input light from ports I-1 and I-2 into the switching network from ports O-1, O-2,., O-8 (Table 1). Subsequently, we obtained the simulation results for the insertion loss and crosstalk noise in the 8x8 optical switching network under different input and output ports. The simulation results indicate that the overall insertion loss of the optical switching network ranges from 0.296 dB to 0.463 dB, whereas the crosstalk is between -64.33 dB and -49.6 dB (Fig. 5). We further analyzed the state of each 2x2 optical switching unit within the network by inputting light into all eight ports under various multi-input states (Table 2). Subsequently, we simulated the insertion loss of each output port under multiple multi-output states at an operating wavelength of 1550 nm (Fig. 6). Additionally, we simulated a single-channel eye diagram with a data rate of 25 Gbit/s and obtained the extinction ratio, rise time, and fall time (Fig. 7), which show relatively clear eye-diagram results under all states. Finally, we compared the proposed architecture with those of conventional 8x8 optical switching networks. The results show that the optical switching network based on Sb2Se3 - MZI features a low insertion loss, low crosstalk, a compact footprint, and nonvolatile static zero power consumption (Table 3). Conclusions We present a reconfigurable 8x8 low-loss nonblocking optical switching network based on nonvolatile phase-change material Sb2Se3 and an MZI. This network comprises 20 Sb2Se3-MZI-based 2x2 optical switches and 16 optimized crossing waveguides interconnected via the Benes topology. Notably, a 2x2 optical switch unit is achieved through optically controlled Sb2Se3 phase states, thus obviating the conventional method of using an external voltage to control the phase state of the upper and lower arms in the MZI via electrode patches. This design offers low loss, minimal power consumption, and a compact chip area. Simulation results indicate that the proposed optical switching network enables parallel data exchange among all nodes while maintaining low insertion loss and crosstalk noise. This advancement contributes significantly to the development of large-scale data-center optical switching networks.