Fig. 1. Diagram of wavelength routing of a 6×6  WR switch (N=2 and M=3). Six kinds of small blocks with different colors represent different wavelengths.

Fig. 2. Simulated ILs of (a) 2×2 crossings and (b) 3×3 crossings as a function of semi-major axis a and semi-minor axis b of the elliptical region.

Fig. 3. (a)–(c) Diagrams of three connecting cases when the fan-out angle (θ) is 0°, 45°, and 90°, respectively, and related parameters are marked. (d) Horizontal length (Lx), longitudinal length (Ly), and square area (S) of the connecting area as a function of θ.

Fig. 4. (a) Optimized interconnection network of the 12×12  WR switch. (b) Simulated port-to-port IL profiles of the conventional and the optimized interconnection networks.

Fig. 5. Microscope image of the fabricated 12×12 silicon WR switch and zoomed-in crossing structure.

Fig. 6. (a) Measured ILs of 3×3 AWG and 4×4 AWG. (b) Measured total IL of the 12×12 silicon WR switch for different transmission paths, reference interconnection network IL and AWG IL, which is given by subtracting the average reference interconnection network IL from the average total IL.

Fig. 7. Measured bit error rate (BER) curves at 10 Gb/s and eye diagram when received optical power is −20  dBm.