Application of GPT to tanδ measuring apparatus fordistribution cable in hot line

A hot line tanδ measuring apparatus which uses the secondary voltage of GPTs (grounding potential transformers) existing at substations and other facilities has been developed. An error vector circle diagram method which allows one to determine the value of tanδ to an accuracy of 0.1%, notwithstanding the phase difference existing between the primary and secondary voltages of a GPT, is described. The method was used in field experiments with favorable results. The method is especially superior in terms of safety and operability because no contact with high-voltage portions is required     

GaInAsP/InP DH lasers with a chemically etched facet

We describe a new configuration and novel fabrication method for GaInAsP/InP DH lasers in which one of the facet mirrors is chemically etched and the other one is formed by cleaving. The etched facet is fabricated monolithically by wet chemical etching in a solution of HCl:CH3COOH:H2O2= (1:2:1). Broad-area contact lasers of this type operating at room temperature at a wavelength ofsim 1.3 mum have been demonstrated.     

Monolithically integrated eight-channel WDM modulator with narrow channel spacing and high throughput

We demonstrate an eight-channel wavelength division multiplexing (WDM) modulator module that monolithically integrates arrayed waveguide gratings and semiconductor optical amplifiers and electroabsorption optical modulators arrays. The compact module can generate individual optical signals for each WDM channel with low optical and electrical crosstalk. We show two configurations for the narrow channel spacing of 25 GHz and high throughput of beyond 80 Gb/s. Combining this WDM modulator with a multi-wavelength light source is a promising approach to creating a compact WDM optical transmitter.     

Highly strained GaInAs-GaAs quantum-well vertical-cavitysurface-emitting laser on GaAs (311)B substrate for stable polarizationoperation

We have realized high-quality GaInAs-GaAs quantum wells (QWs) with high strain of over 2% on GaAs (311)B substrate for a polarization controlled vertical-cavity surface-emitting laser (VCSEL). By increasing the In composition in GaInAs, the optical anisotropy in photoluminescence (PL) intensity was increased. The anisotropy of 50% was obtained at 1.15 μm emission wavelength. We have demonstrated edge-emitting lasers and VCSELs emitting at over 1.1 μm on GaAs (311)B substrate for the first time. The 1.15-μm edge-emitting laser showed a characteristic temperature of 210 K and the threshold current density of 410 A/cm². The threshold current and lasing wavelength of VCSELs are 0.9 mA and 1.12 μm, respectively. The orthogonal polarization suppression ratio was 25 dB and CW operation up to 170°C without a heat sink was achieved     

Lasing characteristics of InGaAs-GaAs polarization controlledvertical-cavity surface-emitting laser grown on GaAs (311) B substrate

We have demonstrated an oxide confinement polarization controlled vertical-cavity surface-emitting laser (VCSEL) grown on a GaAs (311)B substrate. The polarization state was well controlled along the [2¯33] crystal direction due to an anisotropic gain in the (311)B plane. We fabricated a small oxide aperture VCSEL with a threshold of 260 μA and realized single-transverse mode and single-polarization operation for the first time. The sidemode suppression ratio (SMSR) was 35 dB and the orthogonal polarization suppression ratio (OPSR) was 25 dB. In addition, we have measured polarization and transverse mode characteristics of multi- and single-transverse mode devices under high-speed modulation. In the multimode device of 12 μm×12 pm oxide aperture, we have achieved stable polarization operation of over 25-dB OPSR up to 10 Gb/s and have observed no power penalty due to polarization instability under 2.5-Gb/s pseudorandom modulation. The single-mode device showed stable single-transverse mode and polarization under the modulation conduction up to 5 GHz of sinusoidal modulation. SMSR and OPSR were over 30 and 10 dB, respectively     

Negative strand of hepatitis C virus RNA in the liver of patients with chronic hepatitis C after interferon treatment

In patients receiving interferon therapy for chronic hepatitis C, serum hepatitis C virus (HCV) RNA often reverts from an undetectable to a detectable form after completion of treatment. Detection of the negative strand of HCV-RNA in liver tissue is regarded as an index of viral proliferation. Therefore, we investigated changes in the hepatic negative-strand HCV-RNA following interferon therapy to determine whether this parameter could predict the long-term response to treatment. The subjects of this study were 27 patients with chronic active hepatitis C. Serum positive-strand and hepatic tissue negative-strand HCV-RNA were detected using polymerase chain reaction. At the completion of interferon treatment, serum HCV-RNA was not detected in 21 patients. One year following treatment it remained undetectable in 14 of these patients but it had reverted to a detectable form in seven. The 14 patients in whom hepatic negative-strand RNA was not detected between 2 weeks and 12 months after treatment, had not relapsed after another year. In the 13 remaining patients, negative-strand RNA was found in liver tissue and serum RNA either reverted to a detectable form or remained detectable throughout. From these findings, we conclude that the detection of negative-strand HCV-RNA in liver tissue 2 weeks after the completion of interferon therapy is useful for predicting the long-term effect of therapy.     

Distributed-index planar microlens array prepared from deep electromigration

Monolithic fabrication of a new distributed index planar microlens array by means of a deep electromigration technique in a glass substrate is reported. The array consists of distributed index lenses of 1.2 mm in diameter with 6.8 mm focal length. The focused spot is as small as 16 ?m for ?=0.63 ?m. The coupling efficiency of 60% to a multimode VAD fibre has been obtained.     

AlGaAs/GaAs multiquantum-well (MQW) surface-emitting laser

In the letter the lasing characteristics of a multiquantum-well surface-emitting injection laser with 100 wells at 77 K under pulsed condition is reported. The output light of the device was linearly polarised.<>     

Role of adsorption effects on absolute electron-molecule cross-section calibration using the relative flow technique

In this work, we report an experimental investigation on relative flow-rate determination for vapors. The mechanism of adsorption-desorption of vapors on surfaces is considered. In contrast to previous investigations, our study shows that the adsorption of vapors on surfaces may significantly affect the flow-rate determination and consequently the measured cross sections. Particularly, for water, it can result in an overestimation of 35% in the cross sections.