Research On Silica-on-Silicon Matrix Optical Switches Based On Planar Lightwave Circuit

Optical switch is a key component for OADM and OXC of all optical networks. PLC technology is compatible with Si-microelectronics techniques and is widely used in integrated light waveguide device. With the combination of matrix optical switch network construction and PLC technology, a small size and low loss PLC-based silica matrix optical switch is studied. Rearrangeable non-blocking constructions of matrix optical switches based on extended Banyan network are proposed and a kind of dynamic routing arithmetic of signals for this network is studied. With the extended Banyan network and optimized MZI switch units, a series of optical switches from 2×2 to16×16 are designed and fabricated.Firstly, the theory of light waveguide is introduced. Beginning with Maxwell equation group, the distribution of modal field of a three-layer planar waveguide is analyzed. Theoretical model of rectangle waveguide is obtained, and modal characters of rectangle waveguide are analyzed with effective refractive index method. The coupling coefficient and modal propagation constant of bi-waveguide direction coupler are deduced.Beginning with structure and theory of Mach-Zehnder interferometer optical switch, effect of 3dB coupler and waveguide arms on switch performance are analyzed. The performance of 3dB coupler is simulated and heating electrode structure is designed according to phase shifter theory. The length of optimized MZI switch unit is 4.6 mm. Two types of 2×2 optical switches are designed, one is unbalanced type, the other is balanced type, and the averaged insertion losses are 1.65 dB and 2.52 dB, respectively, maximum crosstalk are -21.82dB and -30.75dB, respectively, the averaged power consumption are 406mW and 410mW respectively.The networks of matrix optical switches are studied. Crossbar and Banyan network construction of matrix optical switch are analyzed and internal blocking characters of Banyan network are studied. Crossbar network is strictly non-blocking, however, it needs much switch units and linkings, and concludes 2N-1 stages of units for an N×N network; while Banyan network needs less switching units and includes stages of switching units for an log₂ N +1network, but it is a kind of internal blocking network. Based on the internal blocking characters of Banyan network, the condition of constructing rearrangeable non-blocking extended Banyan network is analyzed, and the briefest construction of rearrangeable non-blocking extended Banyan network is proposed. Three types of rearrangeable non-blocking extended Banyan network of BEBN-I type, BEBN-II type and SEBN type, which including switching units of 2 log₂ N -2, 2 log₂ N-2, and , respectively, are proposed.The rearranging process of signal routing of extended Banyan network is analyzed and a novel signal dynamic routing arithmetic is proposed. The arithmetic coded the switch unit and port address of network with binary code, and decided signal routing dynamically according to signals'destination addresses to realize routing rearranging of network.With the optimized MZI switch unit and extended Banyan network, the 4×4, 8×8 and 16×16 silica-on-silicon matrix optical switches are designed and fabricated in 4''wafer basing on PLC technology. The performance of optical switches are measured, the averaged insertion loss are 4.1dB, 4.5dB and 6.5dB respectively, maximum crosstalk are -32.55dB, -50.18dB and -32.95dB respectively, the ER are 30.6dB, 27.75dB and 39.52dB respectively, switching power of single channel are 1.5W, 2W and 2.5W, respectively.