Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 15, Issue 23, 8 November 1979
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Volume 15, Issue 23
8 November 1979
Modal dispersion of optical fibres with a composite α-profile graded-index core
- Author(s): A. Weierholt
- Source: Electronics Letters, Volume 15, Issue 23, p. 733 –734
- DOI: 10.1049/el:19790524
- Type: Article
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It is shown that refractive-index profiles with different values of a in different annular regions of the core cross-section make it possible to achieve an almost flat r.m.s. spectral response over a spectral region of several hundred nanometres.
Mode dispersion of trapezoidal cross-section dielectric optical waveguides by the effective-index method
- Author(s): J.G. Gallagher
- Source: Electronics Letters, Volume 15, Issue 23, p. 734 –736
- DOI: 10.1049/el:19790525
- Type: Article
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The mode dispersion of dielectric optical waveguides is calculated by the effective-index method and is compared with previously reported experimental and theoretical finite-element results for trapezoidal cross-section waveguides. Agreement between experimental and predicted results is very good. This is significant because it means that stripe waveguides can be designed with specific modal propagation properties using the much simpler effective-index method even though the waveguide cross-section is not rectangular.
Optimal radix for monolithic memories
- Author(s): E. Seevinck
- Source: Electronics Letters, Volume 15, Issue 23, p. 736 –737
- DOI: 10.1049/el:19790526
- Type: Article
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Multivalued storage elements are of interest in the quest for higher information density of monolithic memories. The optimal radix to be used is a compromise between information content and cost factors such as silicon-chip area. Formulas are developed which enable the optimal radix to be found. Some recently proposed multivalued storage elements are evaluated for optimal radix by means of the derived formulas.
Tee-coupler for single-mode fibres
- Author(s): E. Weidel and D. Gruchmann
- Source: Electronics Letters, Volume 15, Issue 23, p. 737 –738
- DOI: 10.1049/el:19790527
- Type: Article
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A new concept for an end face tee-coupler with single-mode fibres is described. The outer surfaces of the two fibres are ground and polished on one side and then fixed together. A third fibre is then butt-jointed. The dividing ratio between the two fibres can be chosen arbitrarily. The total loss is about 2 dB. The coupler is polarisation-independent.
Picosecond optical pulse generation from an r.f. modulated AlGaAs d.h. diode laser
- Author(s): Hiromasa Ito ; Hiroyuki Yokoyama ; Shigeru Murata ; Humio Inaba
- Source: Electronics Letters, Volume 15, Issue 23, p. 738 –740
- DOI: 10.1049/el:19790528
- Type: Article
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AlGaAs d.h. lasers with relatively low d.c. bias were demonstrated to be quite feasible for generation of a train of 30 ps optical pulses at a modulated frequency of below the GHz range. The pulse envelope width was measured by an s.h.g. correlation method as well as an ultrafast streak camera; the results agreed fairly well.
Compact dual-hybrid-mode feeds with low crosspolar radiation
- Author(s): S.C.J. Worm
- Source: Electronics Letters, Volume 15, Issue 23, p. 740 –741
- DOI: 10.1049/el:19790529
- Type: Article
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Results of experimental dual-hybrid-mode feeds are described. The hybrid modes are generated at a corrugated step discontinuity. The electrical length of the feeds is substantially reduced compared with feeds developed earlier. The feeds yield high signal/noise ratios and show low crosspolar radiation. They are suitable for radio-astronomical applications and radio-relay links.
Improvement of intermodulation distortion in microwave m.e.s.f.e.t. amplifiers using gate-bias compensation
- Author(s): Ramesh K. Gupta ; Paul A. Goud ; Colin G. Englefield
- Source: Electronics Letters, Volume 15, Issue 23, p. 741 –742
- DOI: 10.1049/el:19790530
- Type: Article
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A simple technique is described for improving the intermodulation distortion performance of microwave m.e.s.f.e.t. amplifiers. The technique utilises transistor gate-bias compensation controlled by the input signal level of the amplifier. For a constant output power of 0 dBm, an improvement in third-order intermodulation distortion product of up to 10 dB has been observed. The advantages and limitations of the technique are discussed.
n-channel formation on semi-insulating InP surface by m.i.s.f.e.t.
- Author(s): Tsuyoshi Kawakami and Masamichi Okamura
- Source: Electronics Letters, Volume 15, Issue 23, page: 743 –743
- DOI: 10.1049/el:19790531
- Type: Article
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InP m.i.s.f.e.t.s using Fe-doped semi-insulating material surface have been fabricated. The devices, composed of sulphur-diffused n-type source and drain and c.v.d. Al2O3 gate insulator, exhibited n-channel normally-off behaviour and a source drain capacitance two orders of magnitude smaller than that of p-InP m.i.s.f.e.t.s with the same dimensions.
Synthesis and analysis of d.l.t.s. spectra from m.o.s. surface states
- Author(s): K.R. Whight
- Source: Electronics Letters, Volume 15, Issue 23, p. 744 –745
- DOI: 10.1049/el:19790532
- Type: Article
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Given Nss and σss as functions of energy and temperature, a procedure is developed to synthesise d.l.t.s spectra under arbitrary experimental conditions. Methods of analysis are then considered to determine Nss and σss from capture experiments.
Integrated-circuit fabrication flaw detected using the supply-current analysis technique
- Author(s): M.G. Rowlands
- Source: Electronics Letters, Volume 15, Issue 23, p. 745 –747
- DOI: 10.1049/el:19790533
- Type: Article
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A serious internal fabrication defect detected in a t.t.l. bipolar integrated circuit has been revealed by analysing anomalies in the supply-current dependence upon the logic input. The result strengthens the claim for using this approach as a quality and reliability screening method.
800 Mb/s fibre transmission test using low-loss and low-dispersion single-mode cable
- Author(s): Nakagawa Kiyoshi ; Hakamada Yoshiro ; Suto Koh-Ichi
- Source: Electronics Letters, Volume 15, Issue 23, p. 747 –748
- DOI: 10.1049/el:19790534
- Type: Article
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Error-rate performances of a single-mode fibre transmission system are evaluated at wavelengths of 1.18 and 1.31 μm. It is proven that longitudinal single-mode oscillation of the laser is important in a high-bit-rate system at a finite dispersion wavelength. At a low dispersion wavelength of 1.31 μm, repeater spacing at 800 Mb/s was extended to 40 km, by developing a low-loss single-mode fibre cable, a stabilised optical transmitter and receiver and a single-mode optical connector.
Gettering of epitaxial gallium phosphide using phosphosilicate glass
- Author(s): Bruce W. Wessels
- Source: Electronics Letters, Volume 15, Issue 23, p. 748 –749
- DOI: 10.1049/el:19790535
- Type: Article
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Chemically vapour deposited phosphosilicate glass films were used to getter epitaxial gallium-phosphide layers. Significant improvements in the electroluminescent efficiency of yellow light-emitting diodes fabricated from the gettered material were observed. Results suggest that the gettering removes compensating impurities as well defects which influence minority carrier lifetime.
Optical-fibre network system for air-pollution monitoring over a wide area by optical absorption method
- Author(s): Humio Inaba ; Takao Kobayasi ; Masayuki Hirama ; Mostafa Hamza
- Source: Electronics Letters, Volume 15, Issue 23, p. 749 –751
- DOI: 10.1049/el:19790536
- Type: Article
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A low-loss optical-fibre network system for monitoring air pollution and species concentrations in various environments utilising the differential absorption method is proposed and discussed as a sensitive and economical as well as nonhazardous method. Its feasibility and advantages are also described on the basis of the present state of the art of the relevant technology.
Surface reactance of corrugated planes
- Author(s): G.L. James
- Source: Electronics Letters, Volume 15, Issue 23, p. 751 –753
- DOI: 10.1049/el:19790537
- Type: Article
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The surface reactance of a corrugated plane illuminated by a plane wave is determined using a rigorous solution. This result is used to establish the range of validity of the usual approximate solution. The dependence of the surface reactance on slot period, depth and width, and the angle of the incident wave, is discussed.
Evidence of trapping in device-quality liquid-phase-epitaxial In1−xGaxAsyP1−y
- Author(s): P.K. Bhattacharya ; J.W. Ku ; S.J.T. Owen ; S.H. Chiao ; R. Yeats
- Source: Electronics Letters, Volume 15, Issue 23, p. 753 –755
- DOI: 10.1049/el:19790538
- Type: Article
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Traps have been identified in epitaxial n- and p-type In1−xGaxAsyP1−y for the first time. The activation energy, capture cross-section and density of several electron traps in the quaternary composition range from InP to In0.53Ga0.47As have been determined. An electron trap similar in some characteristics to the 0.83 eV electron trap present dominantly in bulk and v.p.e. GaAs was observed in an n-type In0.71Ga0.29As0.45P0.55(Eg=0.95 eV) layer. Hole traps were not observed.
Analysis and measurement of modal noise in an optical fibre
- Author(s): B. Daino ; G. de Marchis ; S. Piazzolla
- Source: Electronics Letters, Volume 15, Issue 23, p. 755 –756
- DOI: 10.1049/el:19790539
- Type: Article
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Modal noise in analogue and digital optical fibre systems has been demonstrated to be a significant effect. In this letter, we give some theoretical and experimental results concerning the behaviour of the signal-to-noise ratio in presence of modal noise considering the power from the exit face of a short sample of a graded-index multimode optical fibre.
Incorporation of bromine into Si-SiO2 interfaces and effects on interface state distribution
- Author(s): T.C. Poon and H.C. Card
- Source: Electronics Letters, Volume 15, Issue 23, p. 756 –757
- DOI: 10.1049/el:19790540
- Type: Article
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An experimental study has been made of the effects of bromine treatment of (111) silicon surfaces before thermal oxidation. A sharp peak in the Si-SiO2 interface state distribution at Ev+ 0.15 eV and an overall increase in density by as much as two orders of magnitude has been observed in m.o.s. structures with SiO2 thickness of ≈ 100 Å. In a.c. conductance against bias voltage measurements, two conductance peaks are observed rather than the customary single peak.
Low-loss optical Y-branch
- Author(s): D. Opielka and D. Ritich
- Source: Electronics Letters, Volume 15, Issue 23, p. 757 –759
- DOI: 10.1049/el:19790541
- Type: Article
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An optical Y-branch is described which, owing to its low losses, is suitable for use in both optical multiplexing systems and measuring equipment, Different methods of attenuation, temperature, near- and far-field measurements are given for the characterisation of the branch.
Depletion-type m.o.s.f.e.t.s for low-temperature operation
- Author(s): M. Kawashima ; M. Kanamori ; M. Matsumura
- Source: Electronics Letters, Volume 15, Issue 23, p. 759 –760
- DOI: 10.1049/el:19790542
- Type: Article
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Taking carrier freeze-out into account|a novel structure for depletion-type m.o.s.f.e.t.s suitable for low-temperature operation is proposed. Its channel consists of two regions; a relatively wide, low-impurity-density region and a relatively narrow, high-impurity-density region. It is estimated that the proposed structure has more square-law-like load character istics and higher current density than conventional ones.
Effects of drop size and temperature on forward and backward scattering of microwaves by raindrops
- Author(s): S.A.J. Upton ; B.G. Evans ; A.R. Holt
- Source: Electronics Letters, Volume 15, Issue 23, p. 760 –762
- DOI: 10.1049/el:19790543
- Type: Article
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An explanation is given for the peak sensitivity around 9–11 GHz to drop-size distribution and temperature of microwave attenuation due to a rain-filled medium. The sensitivity of radar reflectivity, differential radar reflectivity and differential radar cross-section to drop-size and temperature are also given. It is shown that at frequencies in excess of about 25 GHz the vertical radar cross-section of water drops can be greater than the horizontal.
Propagation constants of guided modes in graded-index fibre with polynomial-profile core
- Author(s): H. Ikuno
- Source: Electronics Letters, Volume 15, Issue 23, p. 762 –763
- DOI: 10.1049/el:19790544
- Type: Article
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Corrected propagation of the guided modes in a graded-index fibre with a polynomial-profile core are given in analytic form by using a modified Maslov's formula. The result coincides with one obtained by the evanescent-field theory.
Single-mode c.w. ridge-waveguide laser emitting at 1.55 μm
- Author(s): I.P. Kaminow ; R.E. Nahory ; M.A. Pollack ; L.W. Stulz ; J.C. Dewinter
- Source: Electronics Letters, Volume 15, Issue 23, p. 763 –765
- DOI: 10.1049/el:19790545
- Type: Article
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Single-mode c.w. operation at λ=1.55 μm has been achieved in ridge-wavelength lasers fabricated using InGaAsP quaternary alloys. These lasers are promising candidates for future long-distance optical communications systems.
Minimum dispersion at 1.55 μm for single-mode step-index fibres
- Author(s): C.T. Chang
- Source: Electronics Letters, Volume 15, Issue 23, p. 765 –767
- DOI: 10.1049/el:19790546
- Type: Article
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The single-mode step-index fibre parameters, relative index difference and core diameter, have been predicted to achieve first-order cancellation between material and waveguide dispersions at 1.55 μm. Our prediction by accurate solution of the characteristic equation results in fibre parameters different from those obtained by other investigators. The origin of this difference is examined.
Reply: Minimum dispersion at 1.55 μm for single-mode step-index fibres
- Author(s): K.I. White and B.P. Nelson
- Source: Electronics Letters, Volume 15, Issue 23, page: 767 –767
- DOI: 10.1049/el:19790547
- Type: Article
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