Optimal design and characteristics analysis of a polymer electro-optic switch with seven vertical-turning serial-cou- pled microrings

A novel 1 x2 polymer electro-optic （EO） switch based on seven vertical-mining serial-coupled microrings is proposed for dropping crosstalk and obtaining fiat boxlike spectrum. The device structure, theory and formulation are presented, and the microring resonance order and coupling gaps are optimized. The switching voltage of the device for obtaining crosstalk lower than -30 dB under through state is decided to be about 1.86 V. Under the operation voltages of 0 V （drop state） and 1.86 V （through state）, the switching performance is characterized, and the output spectrum is ana- lyzed. The calculation results show that the crosstalk at through state and that at drop state are -30.2 dB and -53.2 dB, respectively, while the insertion losses are 0.86 dB and 3.18 dB, respectively. Owning to the seven serial-coupled mi- crorings resonance structure, the proposed switch reveals the favorable boxlike spectrum compared with the simple device with only one microring, and thus the crosstalk under drop state is improved from -26.8 dB to -53.2 dB. Due to the low crosstalk, this device can be used in optical networks-on-chip for signal switching and routing.     

Optimization design of optical waveguide in Mach-Zehnder electro-optical polymer modulator

In order to reduce transmission loss of the optical waveguide in Mach-Zehnder (M-Z) electro-optical (EO) polymer modulator,the basic iterative formula of semi-vector finite-difference beam propagation method (FD-BPM) is obtained from the scalar wave equation. The transition waveguide is combined with S-type bend branch waveguide for the M-Z EO modulator in the branch waveguide. The effects of structure parameters such as ridge width,length of the branch waveguide and interferometer spacing on the transmission loss are systematically studied by using the semi-vector FD-BPM method. The structure is optimized as an S-sine bend branch waveguide,with rib width w=7μm,length of branch waveguide L=1200μm and interferometer spacing G=22 μm. The results show that the optimized structure can reduce transmission loss to 0.083 dB,which have a certain reference value to the design of optical waveguide in M-Z polymer modulator.     

A High Efficiency Fully Integrated OOK Transmitter for WBAN

A 2.4 GHz high efficiency radio frequency(RF) transmitter for wireless body area network(WBAN) in medical applications is presented in this paper. The transmitter architecture with high energy efficiency is proposed to achieve a high data rate with low power consumption. In conventional transmitters,the oscillator and power amplifier are turned off when the transmitter sends 0. The required time for turning oscillator ON/OFF is longer than the other blocks of the transmitter. In the proposed transmitter, the low power oscillator is on all the time while the power amplifier and modulator are turned off when "0" data is sent. The transmitter consumes 3.2 mW at 0.5 dBm output by 285 Mbps data rate and the energy consumption per transmitted bit with 0.5 dBm output power is 10pJ/(bitmW). The proposed transmitter was designed in0.18 μm CMOS technology.     

Design of Track/Hold （T/H） Circuit of Broad Bandwidth and High Speed Pipeline Structure ADC Based on the Super Frequency Application

A track/hold （T/H） circuit of broad bandwidth high speed pipeline structure ADC based on the super frequency application is designed in the paper. Some main factors affecting SNR of high speed ADC, such as aperture uncertainty, switch capacitor, and MOS switch, are analyzed. In the circuit, the full-differential structure and the bottom plate sampling technique are adopted to optimize the switch capacitors and MOS switches. The result based on the Spectre simulation on 0.35pm Bi- CMOS technology indicate that the aperture uncertainty, charge-injection, and non-linearity of clock feed-through are considerably restrained and the performance of T/H circuit is enhanced     

Low loss optical waveguide crossing based on octagonal resonant cavity coupling

A waveguide crossing utilizing a high index contrast material system is presented. The structure is based on coupling with an octagonal resonant cavity inserted at the waveguide junction. It also employs four identical square metal strips placed at the four comers of the waveguide crossing. The spectral response of the structure calculated using the method of line numerical technique, in general, shows a high power transmission in the forward arm with sufficiently low crosstalk and fraction of radiated power.     

An ultra-compact cross/bar optical routing switch using two polymer electro-optic microrings

A 2×2 cross/bar polymer electro-optic(EO) routing switch is proposed,which is composed of two passive channel waveguides and two active EO polymer microrings with bending radius of only 13.76 μm.Detailed structure,theory and formulation are provided to characterize the output power of the switch.For obtaining fundamental mode propagation,small bending loss and phase-matching between channel waveguide and microring resonator(MRR) waveguide,the structural parameters are optimized under the wavelength of 1550 nm.Analyses and simulations on output power and output spectra indicate that a switching voltage of 5 V is desired to realize the exchange between cross state and bar state,the crosstalk under cross state and that under bar state are about 28.8 dB and 39.9 dB,respectively,and the insertion losses under these two states are about 2.42 dB and 0.13 dB,respectively.Compared with our four EO switches reported before,this device possesses ultra-compact size of 0.233 mm×0.233 mm as well as low crosstalk and insertion loss,and therefore it can serve as a good candidate for constructing large-scale optical routers or switching arrays in photonic network-on-chip(NoC).     

A polymer electro-optic modulator with ultra wide-band and low driving voltage

In this paper, a polymer electro-optic modulator is designed and simulated using the full vectorial finite element method. First order edge elements are used in finite element implementation, and the finite element technique is used to obtain modulator response thoroughly. From the numerical analysis, frequency dispersions of modulator’s important parameters, such as microwave effective index nm , microwave characteristic impedance ZC and microwave loss a, are extracted. Our design exhibits elec...     

高性能的电吸收调制器

A 100-μm-long electroabsorption modulator monolithically integrated with passive waveguides at the input and output ports is fabricated through ion implantation induced quantum well intermixing, using only a twostep low-pressure metal-organic vapor phase epitaxial process. An InGaAsP/InGaAsP intra-step quantum well is introduced to the active region to improve the modulation properties. In the experiment high modulation speed and high extinction ratio are obtained simultaneously, the electrical-to-optical frequency response （E/O response） without any load termination reaches to 22 GHz, and extinction ration is as high as 16 dB.     

基于级联微环谐振器的集成化可重构光学上下路插分复用器

We report on an eight-channel reconfigurable optical add-drop multiplexer based on cascaded microring resonators with a high tuning power consumption and a compact footprint. Microheaters are fabricated on top of the microring resonators and can be modulated using the thermo-optic effect to achieve the reconfigurable functionality of the device. We demonstrate the reconfigurable add-drop multiplexing functionality for channel spacings of 100 GHz and 50 GHz, with the centre wavelengths of the channels aligned to International Telecommunication Union grid specifications. The crosstalk for channel spacings of 100 GHz and 50 GHz are less than..22:5 dB and..15:5 dB, respectively. The average tuning efficiency is about 4.5 mW/nm, and the response speed is about 13.0 kHz.     

A digital input class-D audio amplifier with sixth-order PWM

A digital input class-D audio amplifier with a sixth-order pulse-width modulation(PWM)modulator is presented.This modulator moves the PWM generator into the closed sigma–delta modulator loop.The noise and distortions generated at the PWM generator module are suppressed by the high gain of the forward loop of the sigma–delta modulator.Therefore,at the output of the modulator,a very clean PWM signal is acquired for driving the power stage of the class-D amplifier.A sixth-order modulator is designed to balance the performance and the system clock speed.Fabricated in standard 0.18 m CMOS technology,this class-D amplifier achieves 110 dB dynamic range,100 dB signal-to-noise rate,and 0.0056%total harmonic distortion plus noise.     

应用于2.4GHz无线传感网的超低功耗射频接收前端设计

This paper presents the design of an ultralow power receiver front-end designed for a wireless sensor network （WSN） in a 0.18 μm CMOS process. The author designs two front-ends working in the saturation region and the subthreshold region respectively. The front-ends contain a two-stage cross-coupling cascaded common-gate （CG） LNA and a quadrature Gilbert IQ mixer. The measured conversion gain is variable with high gain at 24 dB and low gain at 7 dB for the saturation one, and high gain at 22 dB and low gain at 5 dB for the subthreshold one. The noise figure （NF） at high gain mode is 5.1 dB and 6.3 dB for each. The input 1 dB compression point （IPldB） at low gain mode is about -6 dBm and -3 dBm for each. The front-ends consume about 2.1 mA current from 1.8 V power supply for the saturation one and 1.3 mA current for the subthreshold one. The measured results show that, comparing with the power consumption saving, it is worth making sacrifices on the performance for using the subthreshold technology.     

Design of a Silicon Based High Speed Plasmonic Modulator

In this paper, we propose a silicon-based high-speed plasmonic modulator. The modulator has a double-layer structure with a 16 μm long metal-dielectric-metal plasmonic waveguide at the upper layer and two silicon single-mode waveguides at the bottom layer. The upper-layer plasmonic waveguide acts as a phase shifter and has a dielectric slot that is 30 nm wide. Two taper structures that have gradually varied widths are introduced at the bottom layer to convert the photonic mode into plasmonic-slot mode with improved coupling efficiency. For a modulator with two 1 μm-long mode couplers, simulation shows that there is an insertion loss of less than 11 dB and a half-wave voltage of 3.65 V. The modulation bandwidth of the proposed modulator can be more than 100 GHz without the carrier effect being a limiting factor in silicon. The fabrication process is also discussed, and the proposed design is shown to be feasible with a hybrid of CMOS and polymer technology.     

Novel Design for High Speed and Resolution Delta-sigma A/D Converter

The delta-sigma converter is one of the high speed and resolution analog-to-digital modulators. Its implementation needs the low oversampling technique and the multi-bit D/A converter. The noise induced by the multi-bit D/A converter becomes one of the key factors deteriorating the signal-to-noise rate of the delta- sigma A/D converter. A novel structure with signal unity transfunction, dynamic element matching（DEM） and noise-shaping is discussed. The method is investigated to design converter based on the proposed structure. The behavior simulation indicates that the structure and the design method are feasible.     

Manufacture tolerance analysis and control for a polymer-on-silicon Mach-Zehnder-interferometer-based electro-optic switch

To enhance the electro-optic (EO) modulation efficiency and realize the impedance-matching, a polymer-on-silicon multi-mode interference (MMI) Mach-Zehnder interferometer (MZI)-based electro-optic (EO) switch is designed and optimized. Under the central operation wavelength of 1550 nm, the driving voltages of the designed switch are 0 and ±1.375 V, respectively, with a short active region length of 5 mm, and the characteristic impedance of the electrode is about 49.6 ?. The manufacture tolerance is analyzed...     

New High Nonlinear and Dispersion Flattened Photonic Crystal Fiber

A new high nonlinear dispersion flattened photonic crystal fiber is proposed. This fiber has three-fold symmetry core. The doped region in the core and the big air-holes in the 1-st ring can make high nonlinearity in the PCF. And the small air-holes in the 1-st ring and the radial increasing diameters air-holes rings in cladding can be used to turn the dispersion properties of the PCF. We can achieve the optimized optical properties by carefully selecting the PCF's structure parameters. A PCF with flattened dispersion is obtained. The dispersion is within ±0.8 ps·nm-1·km-1 from 1.50 μm to 1.62 μm. The nonlinear coefficient is about 12.645 6 W-1·km-1, the fundamental mode area is about 10.257 9 μm2 and the birefringence is about 3.086 96×10-5 at 1.55 μm. This work may be useful for effective design and fabrication of dispersion flattened photonic crystal with high nonlinearities.     

Butt-Joint Monolithically Integrated DFB-LD/EA-MD Light Source for 10Gbit/s Transmission

This paper reports on the design,fabrication，and performance of an integrated electro-absorptive modulated laser based on butt-joint configuration for 10Gbit/s application.This paper mainly aims at two aspects.One is to improve the optical coupling between the laser and modulator;another is to increase the bandwidth of such devices by reducing the capacitance parameter of the modulator.The integrated devices exhibit high static and dynamic characteristics. Typical threshold current is 15mA,with some value as low as 8mA.Output power at 100mA is more than 10mW.The extinction characteristics,modulation bandwidth,and electrical return loss are measured.3dB bandwidth more than 10GHz is monitored.     

Simulation and experimental verification of off-axis fiber Bragg grating bending sensor with high refractive index modulation

Off-axis FBG simulations were performed in this paper using a finite element method in conjunction with the conformal mapping technique to study the bending sensing characteristics of the off-axis FBG with high index modulation. The refractive index (RI) increase of the grating region is taken into consideration for the mode field simulation. The influences of high RI increase and the offset distance of the grating on the bending sensitivity were analyzed. Off-axis FBGs with different offset distances were fabricated using femtosecond laser with phase mask technique in standard single-mode fiber. The simulation results were verified by the experiment. A bending sensitivity of 0.055 dB/m-1 was achieved with an offset distance of 4 μm. The simulation and experiment results suggest that the grating offset distance has a greater influence on the sensitivity of the off-axis FBG with high RI modulation than that with low RI modulation. The proposed sensor structure and simulation results can provide suggestion for the design and processing of off-axis FBG bending sensors.     

Highly sensitive and selective ethanol sensors based on flower-like ZnO nanorods

A simple and easy hydrothermal process has been employed to synthesize flower-like ZnO products consisting of numerous orderly oriented and bundled nanorods.The structure and morphology of the novel ZnO structure are characterized in detail.The flower-like ZnO-nanorod-based gas sensors are investigated for their ethanoi-sensing properties,and the results reveal that the sensors exhibit a high response of 143.6 to 1000 ppm ethanol and good selectivity at the optimal operating temperature of 250℃.The effect of the flower-like morphology on the response of the gas sensors to ethanol is also investigated.     

Design of an ultra-compact 3 dB MMI coupler

The design of an ultra-compact SOI-based 1×2 3 dB multimode interference（MMI） coupler is proposed.The symmetric multimode interference structure and deeply-etched parabolically tapered multimode waveguide are used in the device.The length of the device is reduced by about 87% compared with general multimode interference straight couplers.Based on effective index method（EIM） and two dimensional beam propagation method（2D-BPM）,the structure parameters are optimized and the fabrication tolerances are analyzed.The results indicate that the performance of the coupler is deeply affected by the coupler＇s width,etching depth and photolithography alignment error in perpendicular direction.     

Generation and transmission of dispersion tolerant 10-Gbps RZ-OOK signal for radio over fiber link

We proposed and demonstrated the generation and transmission of 10-Gbps return-to-zero ON/OFF keying (RZ-OOK) signal using a new technique without pulse carving at transmitter.The new technique is char...