Numerical simulation and temporal characterization of dual-pumped microringresonator-based optical frequency combs

Dual-pumped microring-resonator-based optical frequency combs(OFCs) and their temporal characteristics are numerically investigated and experimentally explored. The calculation results obtained by solving the driven and damped nonlinear Schr?dinger equation indicate that an ultralow coupled pump power is required to excite the primary comb modes through a non-degenerate four-wave-mixing(FWM) process and, when the pump power is boosted, both the comb mode intensities and spectral bandwidths increase. At low pump powers, the field intensity profile exhibits a cosine variation manner with frequency equal to the separation of the two pumps, while a roll Turing pattern is formed resulting from the increased comb mode intensities and spectral bandwidths at high pump powers. Meanwhile, we found that the power difference between the two pump fields can be transferred to the newly generated comb modes, which are located on both sides of the pump modes, through a cascaded FWM process. Experimentally, the dual-pumped OFCs were realized by coupling two self-oscillating pump fields into a microring resonator. The numerically calculated comb spectrum is verified by generating an OFC with 2.0 THz mode spacing over 160 nm bandwidth. In addition, the formation of a roll Turing pattern at high pump powers is inferred from the measured autocorrelation trace of a 10 free spectral range(FSR) OFC. The experimental observations accord well with the numerical predictions. Due to their large and tunable mode spacing, robustness,and flexibility, the proposed dual-pumped OFCs could find potential applications in a wide range of fields,including arbitrary optical waveform generation, high-capacity optical communications, and signal-processing systems.

Dual-pump Control Algorithm of Two-speed Powershift Transmissions in Electric Vehicles

A high-speed motor in a drive system causes several challenges to the reliability of the mechanical parts of electric vehicles and leads to issues with noise,vibration and harshness(NVH).Thus,a two-speed powershift transmission is considered an effective way to improve the dynamic,economic and comfort performance of electric vehicles.A newly designed dual-pump hydraulic control system for a two-speed powershift transmission with two wet clutches is presented,in which the mechani-cal oil pump is linearly affected by the vehicle speed and the electric oil pump is controllable.By integrating the dynamic model of the hydraulic system into one of the powertrains with a two-speed transmission,a co-simulation dynamic model is proposed.To satisfy the flow and pressure demand of the hydraulic system,a dual-pump control strategy is presented,in which the electric oil pump is controlled by the mechanical oil pump following the minimum energy consumption principle.The World Light Vehicle Test Procedure(WLTP)cycle simulation results show that the energy consumption of the proposed hydraulic system can be reduced by 58.2%compared to the previous single-pump system developed by the authors with a constant main-line pressure control strategy.On the basis,the best configuration of the two pumps can further reduce the energy consumption of the hydraulic system by 23.2%compared to that of two-oil pumps with preset displacement.