Dongyu Geng

Single-PPLN-assisted wavelength-/time-selective switching/dropping/swapping for 100-GHz-spaced WDM signals

We propose an approach to implementing wavelength- and time-selective optical switching, dropping and swapping based on the sum-frequency generation (SFG) or cascaded sum- and difference-frequency generation (cSFG/DFG) in a periodically poled lithium niobate (PPLN) waveguide. Analytical solutions are derived, showing the parametric depletion effect for optical switching and the narrow-band operation due to quasi-phase matching (QPM) condition of PPLN. Using parametric depletion effect of SFG process, we demonstrate wavelength- and time-selective optical switching for ITU-grid compatible 40-Gbit/s wavelength-division multiplexed (WDM) signals with a channel spacing of 100 GHz. Less than 1-dB power penalty at a bit-error rate (BER) of 10(-9) is measured for the wavelength- and time-selective switching channel. Negligible impacts are observed on other channels of WDM signals. Using combined effects of parametric depletion and wavelength conversion of cSFG/DFG processes, we demonstrate wavelength- and time-selective optical dropping for ITU-grid compatible 100-GHz-spaced 40-Gbit/s WDM signals. Moreover, we demonstrate optical swapping between two 100-GHz-spaced 40-Gbit/s signals. The obtained theoretical and experimental results confirm single-PPLN-assisted wavelength- and time-selective optical switching, dropping and swapping for 100-GHz-spaced WDM signals, which might potentially be extended to WDM signals with narrower channel spacing.

Compact PSR Based on an Asymmetric Bi-level Lateral Taper in an Adiabatic Directional Coupler

We propose a compact silicon-on-insulator polarization splitter-rotator (PSR). The PSR consists of an asymmetric bilevel lateral taper in an adiabatic directional coupler and convert TM₀ mode to TE₀ mode directly without changing the input TE₀ mode. Compared to the previously reported PSR based on TM₀ -TE₁ polarization rotator connected to a TE₁-TE₀ spatial mode order convertor in series, the proposed PSR has a one-step mode conversion, and is inherently more compact. Beside, since the conversion is fully adiabatic, it preserves the benefits of large fabrication tolerance and operation bandwidth. The simulation results show that the TM₀-TE₀ polarization conversion loss is less than 0.5 dB from 1500 to 1700 nm and even less than 0.2 dB over the whole C-band. The TE₀ -TE₀ insertion loss is less than 0.01 dB from 1450 to 1750 nm. The polarization crosstalk is below -35 dB within 300-nm bandwidth.

Hybrid photonic Ethernet switch for datacenters

We demonstrate a photonic packet switch using a hybrid photonics-electronic approach. It uses compression, scrambling and packet size discrimination to allow for the photonic switching of native Ethernet frames.

Scalable photonic packet switch test-bed for datacenters

We demonstrate scaling photonic switch for a datacenter using arrays of fast silicon photonic space switches that are time-slot synchronized, despite the varying distance of interconnected nodes. A low latency scheduling algorithm allows high throughput, with latency comparable to electronic switches.

Photonic Switching of Native Ethernet Frames for Data Centers

We show new techniques of compression, scrambling, and packet size discrimination to implement a photonic-electronic hybrid switch that handle native Ethernet frames. The photonic switch is designed for a silicon photonic switch core.

Low Polarization-Dependent-Loss Silicon Photonic Trident Edge Coupler Fabricated by 248 nm Optical Lithography

Trident edge couplers were fabricated using optical lithography. TE and TM coupling loss with lensed fiber were improved by 0.2 dB and 0.3 dB compared to a single-taper coupler. PDL was improved by 0.1 dB.

Ultra-fine optical spectrum microscope using optical channel estimation and spectrum fusion technique

Ultra-fine optical spectrum microscope is demonstrated based on optical channel estimation using coherent optical OFDM signals and optical spectrum fusion technique. The frequency resolution and measurement range of this technique are 10.7-MHz and 250-GHz respectively.

Silicon Photonic Switch Subsystem With 900 Monolithically Integrated Calibration Photodiodes and 64-Fiber Package

Monolithic germanium photodiodes on every cell calibrate a 32×32 silicon photonic switch of 448 Mach-Zehnders in 10 minutes. 64 fibers permanently attached through a waveguide concentrator in a wire-bonded BGA achieve 2.9dB C-band TE fiber-to-die.

Ultra Low Loss Waveguide Transitions for Reticle-Scale Silicon Nanophotonic Routing

We report compact and low loss silicon nanophotonic waveguide transitions, to connect different cross-sections of routing waveguide in large photonic integrated circuits. 25-<inline-formula> <tex-math notation=LaTeX>

2×2 multimode interference coupler with low loss using 248 nm photolithography

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