Zuxiang Li

Seven-bit reconfigurable optical true time delay line based on silicon integration

We design, fabricate, and characterize a 7-bit reconfigurable optical true time delay line consisting of Mach-Zehnder interferometer (MZI) switches on the silicon photonics platform. Variable optical attenuators (VOAs) are embedded to suppress the inter-symbol crosstalk caused by the finite extinction ratio of switches. The device can provide a maximum of 1.27 ns delay with a 10 ps resolution over a wide wavelength range. Eye diagram measurement of a 25 Gbps 2(51)-1 pseudo-random bit sequence (PRBS) signal reveals the power penalties only increase 0.17 dB and 0.77 dB after transmission through the shortest (reference) and the longest (1.27 ns delay) paths, respectively.

4 × 4 Nonblocking Silicon Thermo-Optic Switches Based on Multimode Interferometers

We experimentally demonstrate a silicon 4 × 4 nonblocking thermo-optic (TO) switch using a generalized Mach-Zehnder interferometer constructed on multimode interferometers. All the 24 switching states for nonblocking switching are characterized. The device fabricated using CMOS technologies has a footprint of 2.8 × 0.65 mm2. The measured average on-chip insertion loss is 9 ± 2 dB and the crosstalk for all switching states is better than -12 dB. The average TO switching power consumption is 109 mW. The switching functionality is verified by transmission of a 40-Gb/s quadrature phase-shift keying optical signal.

Broadband 4×4 non-blocking optical switch fabric based on Mach-Zehnder interferometers

We demonstrate a silicon 4×4 non-blocking Benes switch fabric consisting of three stages of tunable Mach-Zehnder interferometers. Measurements show that the insertion loss is around 10 dB and the crosstalk is below -10 dB over a 40 nm wide wavelength range.

50 Gb/s silicon QPSK modulator with single-drive push-pull traveling wave electrodes design

We demonstrate a silicon QPSK modulator consisting of two nested Mach-Zehnder interferometers with 3.5 mm long traveling-wave electrodes. 50 Gb/s QPSK modulation is achieved with power consumption of 9.3 pJ/bit.

Silicon large-scale optical switches using MZIs and dual-ring assisted MZIs

We report our recent progress on high-throughput 16×16 silicon non-blocking optical switches based on Mach- Zehnder interferometers (MZIs) and dual-ring assisted MZIs (DR-MZIs). TiN microheaters and p-i-n diodes are both integrated in each switch element for thermo-optic phase error correction and GHz-speed electro-optic switching, respectively. The MZI switch exhibits a broad optical bandwidth and low crosstalk. The DR-MZI switch exhibits low electrical switching power but with a narrower optical bandwidth. The two types of switches are designed to have a chip size of 12.1 mm × 4.6 mm mainly restricted by the chip package requirement. The DR-MZI chip can potentially have a smaller footprint due to its much more compact switch element, suitable for high-density on-chip optical data exchange.

4×4 strictly non-blocking optical switch fabric based on cascaded multimode interferometers

We experimentally demonstrate a 4×4 strictly non-blocking silicon thermo-optic (TO) switch fabric consisting of three stages of tunable generalized Mach-Zehnder interferometers. Measurements show that the worst crosstalk of all switching states is -7.16 dB. The average TO switching power consumption is 104.84 mW.

4×4 Silicon non-blocking electro-optic switches based on double-ring assisted Mach-Zehnder interferometers

We demonstrate a 4 × 4 silicon switch using double-ring assisted Mach-Zehnder interferometers. The maximum electro-optic switching power consumption is 1.38 mW, with phase correction power consumption 22.37 mW. The on-chip insertion loss is <;5.8 dB and crosstalk <;-18 dB.

64 Gb/s silicon QPSK modulator with single-drive push-pull traveling wave electrodes

We demonstrate a silicon QPSK modulator consisting of two nested Mach-Zehnder interferometers with 3.5 mm long traveling-wave electrodes. 64 Gb/s QPSK modulation is achieved with an EVM of 24.4% and power consumption of 7.1 pJ/bit.

Silicon-based tunable optical delay lines and switches for next generation optical telecommunications

We report our recent progress on reconfigurable optical true time delay lines (RTTDL) and optical switches. The RTTDL is composed of 8 stages of MZIs connected by 7 waveguide pairs with an incremental length difference. Variable optical attenuators are inserted in the delay waveguides to suppress crosstalk caused by the residual signals from noise paths. Transmission of a 25 Gbps PRBS signal confirms the signal fidelity after a maximum of 1.27 ns delay. The optical switch is based on a Benes architecture with Mach-Zehnder interferometers (MZI) as the switching elements. Both p-i-n diodes and silicon resistive micro-heaters are integrated in the MZI arms for electrical tuning and phase correction, respectively. The measured on-chip insertion loss of the 4×4 switch is < 8 dB. Transmission of a 50 Gb/s quadrature phase shift keying (QPSK) optical signal verifies its switching functionality.