Development of InP-based multichannel transmitters for application in WDM access systems

The influence of crystallinity on the resistive switching behavior of TiO 2

operated for J-PARC. The ion source has been providing a beam for approximately eight years without any serious trouble. A photograph of the present J-PARC ion source is shown in Fig. 1. The ion source consists of a cylindrical plasma chamber, a beam extractor and a large vacuum chamber with 2 turbo molecular pumps of 1500 L/s for differential pumping [1]. The source plasma is produced by an arc discharge and confined by a multi-cusp magnetic field produced by permanent magnets surrounding the chamber wall. The 50 keV negative hydrogen beam is extracted by applying about -50 kV to the beam extractor. The basic structure of the ion source has not been changed since the operation was started. The ion source has been operated in two different modes such as low current mode of 19 mA and high current mode of 32 mA. Continuous operation for about six weeks and about one week was achieved in low and high current mode, respectively. After the operation, we replace the filament by a brand-new one to prevent the filament from failing during the operation. The required time for the replacement including the filament degassing process, the vacuuming and the conditioning operation is about 15 hours. In this presentation, we will introduce the recent operation status of the J-PARC ion source.

The performance characteristics of a Multi-cusped Field Thruster depending on the magnetic field in the plume region were investigated. Five magnetic field shielding rings were separately mounted near the exit of discharge channel to decrease the strength of magnetic field in the plume region in different levels, while the magnetic field in the upstream was well maintained. The test results show that the electron current increases with the decrease of magnetic field strength in the plume region, which gives rise to higher propellant utilization and lower current utilization. On the other hand, the stronger magnetic field in the plume region improves the performance at low voltages (high current mode) while lower magnetic field improves the performance at high voltages (low current mode). This work can provide some optimal design ideas of the magnetic strength in the plume region to improve the performance of thruster.

The results of switching tests of a DC vacuum circuit-breaker designed for rated voltage 3.3 kV and rated current 3000A are presented. The circuit-breaker is intended for current interruption in the networks with fault currents up to 30 kA. To interrupt the direct current, the authors used a method of artificial current transition through zero in the electrical arc between the vacuum interrupter (VI) contacts by means of discharging a preliminary charged capacitor with countercurrent having the direction reverse to the one of the interrupted current. The countercurrent circuit was connected with the use of a triggered vacuum switch (TVS). The contacts in the VI were opened with an electromagnetic repulsion drive activated in the result of the preliminary charged capacitor discharge. The drive circuit was also controlled with the TVS. The contact opening time was 3 ms. The TVS switch-on time did not exceed several microseconds. Three test cycles were carried out for the cases of the current interruption in the mode similar to the normal one, in the fault current mode and in the low current mode. The tests proved that the circuit-breaker ensured safe current interruption in all those modes.

Low-voltage subthreshold CMOS current mode circuits: Design and applications

This paper presents an AC-excited argon discharge generated using a gas-liquid (two-phase) hybrid plasma reactor, which mainly consists of a powered needle electrode enclosed in a conical quartz tube and grounded deionized water electrode. The discharges in the gas-phase, as well as in the two-phase, exhibit two discharge modes, i.e., the low current glow-like diffuse mode and the high current streamer-like constrict mode, with a mode transition, which exhibits a negative resistance of the discharges. The optical emission spectral analysis shows that the stronger diffusion of the water vapor into the discharge region in the two-phase discharges boosts up the generation of OH (A–X) radicals, and consequently, leads to a higher rotational temperature in the water-phase plasma plume than that of the gas-phase discharges. Both the increase of the power input and the decrease of the argon flow rate result in the increase of the rotational temperature in the plasma plume of the water-phase discharge. The stable two-phase discharges with a long plasma plume in the water-phase under a low power input and gas flow rate may show a promising prospect for the degradation of organic pollutants, e.g., printing and dyeing wastewater, in the field of environmental protection.

Implantable biomedical sensors and continuous real time in vivo monitoring of various physiological parameters requires low-power sensor electronics and wireless telemetry for transmission of sensor data. In this article, generic blocks required for such systems have been demonstrated with design examples. Ideally neural or electro-chemical sensor signal monitoring units comprise of low noise amplifiers, current or voltage mode analog to digital domain data conversion circuits and wireless telemetry circuits. The low-noise amplifier described here has a novel open loop amplifier scheme used for neural signal recording systems. The design has been implemented using 0.5-μm SOI-BiCMOS process. The fabricated chip can work with 1 V supply and consumes 805 nA. The current mode analog to digital conversion signal processing circuitry takes the current signal as an input and generates a pulse-width modulated data signal. The data signal is then modulated with a high frequency carrier signal to generate FSK data for wireless transmission. The design is fabricated in 0.5-μm standard CMOS process and consumes 1.1 mW of power with 3.5 V supply.

This paper presents a low voltage, 1.6 GHz integrated receiver front-end which is implemented by the standard 0.35 μm, 3M2P CMOS technology. The receiver consists of a transconductance low noise amplifier (Gm-LNA), a down conversion current mode mixer and a voltage-controlled oscillator using accumulation-mode MOS varactor (A-MOS VCO). A current mode mixer is used to reduce the supply voltage to 1 V. A specially designed Gm-LNA converts RF input voltage to RF input current for the current mode mixer. This could eliminate an unnecessary I---V, V---I conversion and reduce the non-linearity contribution. Moreover, a low voltage A-MOS VCO, with a good phase noise and wide tuning frequency range, is used to generate a required oscillating frequency for the receiver. The integrated receiver front-end has a measured power conversion gain of 11.4 dB, an input referred third-order intercept point (IIP3) of 6.1 dBm, and a noise figure of 5.87 dB. The measured total power consumption is 40.9 mW with 1 V supply.

In this paper, two low component count Voltage Mode (VM) and Current Mode (CM) higher order filters are proposed. The higher order filters are derived from second order filter module, which are realised by using Second Generation Current Conveyors (CCII). Both the filter modules have low component count and lower sensitivity figure. Apart from this, both the modules provide the feature of cascadability, which is required for realisation of higher order filter function. Performances of all the proposed circuits are verified by PSPICE simulation using TSMC 0.25μm technology parameters.

A FGMTL (FGMOS Translinear) principle based current mode one quadrant squarer/divider circuit operating at low voltage in saturation region is presented. Squarer/divider is the key circuit which acts as a core building block for nonlinear signal processing functions. Low voltage square/divider can be constructed using FGMTL principle in place of MTL (MOS Translinear) principle in saturation. Multi-input nature of FGMOS transistor reduces the transistor’s threshold voltage which allows low voltage operation of the proposed circuit in saturation region. Proposed circuit is designed at a supply voltage of 0. 7V. It offers a bandwidth of 0. 5GHz when simulated in LTSPICE software using 0.18$\mu$m CMOS technology. THD of 2.3% to 4.7% is obtained for the sinusoidal peak to peak input current range from 1$\mu$A to 10$\mu$A at a frequency of 1KHz.

A low power low voltage current mode 9-bit pipelined a/d converter and 8-bit self-calibrated d/a converter to interface a DSP system are presented in the paper. The a/d converter is built of 1.5 bit stages with digital error correction logic. The self-calibrated d/a converter is composed of M LSBs fine and N MSBs coarse current mode converters. The a/d and d/a converters were designed in 0.35μm technology, then fabricated to verify proposed concept. Performances of both converters are compared to performances of known converter structures. Low power consumption and small chip area are advantages of the proposed converters.

A tunable fiber ring laser based on an in-line two-taper Mach-Zehnder interferometer (MZI) filter was realized, and the effect of beam waists of the tapers on performance of the laser was investigated with different beam waists of 70 μm, 49 μm, and 33 μm. Experimental results show that the tunable laser with MZI length of 1 m and beam waist of 49 μm can cover 16.1 nm with tuning steps of 0.07-0.5 nm, a bandwidth of 10 pm, and a side mode suppression ratio (SMSR) of 40-50 dB. Tuning range is not only determined by the number of the cladding modes but is also affected by the filter loss. Tuning step is determined by the differences of the effective refractive indexes between the cladding modes and the core mode. SMSR is determined by the balance between the extinction ratio of the filter and the cavity loss of the laser due to MZI filter.

A multiwavelength Ytterbium-doped fiber ring laser operating at 1030 nm region is demonstrated using a Sagnac loop mirror and a Mach-Zehnder interferometer. We report the Performance comparisons of multi-wavelength oscillations in Yb3+ doped fiber lasers (YDFL) with typical commercial ytterbium doped silica fibers. By adjusting the polarization controller (PC), a widely tunable laser range of 22 nm from 1030 nm to 1050 nm is obtained. The Mach-Zehnder interferometer (MZI) design has exhibited simplicity in the operation for controlling the smallest wavelength spacing compared to Sagnac loop mirror method. In our observations, the smallest achieved stable wavelength spacing in Sagnac loop mirror setup and MZI setup were 2.1 nm and 0.7 nm, respectively. In case of nine-wavelength operation with a MZI setup, the stability, Full Width at Half Maximum (FWHM) and side mode suppression ratio (SMSR) of laser lines are not affected by increasing pump power, While for above four wavelength operation, the laser stability with Sagnac loop mirror becomes worse specially for higher input pump power and the power fluctuation among the wave-lengths would be also slightly larger.

The high-energy ion nanoprobe LIPSION at the University of Leipzig has been operational since October 1998. The ultrastable single ended 3.5 MV SINLETRONTM accelerator supplies the H+ or He+ ion beam. A magnetic scanning system moves the focused beam across the sample. At present, a resolution of 150 nm in the low current mode and 300 nm at 5 pA could be achieved. The UHV grade experimental chamber is equipped with electron-, energy dispersive X-ray-, and particle detectors. They can be used simultaneously to analyse the sample by means of PIXE (particle induced X-ray emission), RBS (Rutherford backscattering) and in the case of thin samples STIM (scanning transmission ion microscopy). A goniometer allows the application of channeling measurements in single crystals in combination with these methods. The detection limits depend on the elements to be analysed and range from (1000⋯1) μg/g relative and (1⋯0.01) pg absolute. The analysis is nondestructive, but the sample has to be vacuum resistant. Applications of the nanoprobe in the field of semiconductor research, biomedicine, and archaeology will be described.

Based on ray optics technique we have analyzed the first-order backward coupling coefficient in a laterally tapered distributed feedback (DFB) laser diode. These tapered structures are designed to realize narrow beam divergence, low threshold current and high longitudinal mode selectivity. The coupling coefficient, κ, for three different laterally tapered waveguide distributed feedback laser diodes have been studied. It has been found that without changing the grating period and the material properties, the coupling coefficient can be altered by modifying the taper profile and waveguide dimensions while satisfying the adiabatic single-mode condition.