Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 16, Issue 18, 28 August 1980
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Volume 16, Issue 18
28 August 1980
Channelled substrate lasers prepared by combination of organometallic pyrolysis and liquid-phase epitaxy
- Author(s): J.P. Noad ; C.M. Look ; A.J. Springthorpe
- Source: Electronics Letters, Volume 16, Issue 18, p. 685 –686
- DOI: 10.1049/el:19800486
- Type: Article
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Channelled substrate planar (c.s.p.) GaAlAs-GaAs d.h. lasers with p-type blocking layers have been prepared using a combination of organometallic pyrolysis and liquid-phase epitaxy. The use of o.m.p. to prepare the channelled blocking layers allows the growth of thin first confining layers necessary for good mode control. Devices produced in this manner are both linear and single-mode to power levels in excess of 14 mW.
Probabilistic approach to multiplexer logic circuit design
- Author(s): A.B. Ektare and D.P. Mital
- Source: Electronics Letters, Volume 16, Issue 18, p. 686 –687
- DOI: 10.1049/el:19800487
- Type: Article
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A new approach, based on the theory of probability, is suggested to select the control variables for a multiplexer logic circuit. The method is suitable when the number of variables and minterms involved are large. Moreover, the method usually leads to a design with a minimum number of multiplexers.
Radiation characteristics of helix antenna with parasitic elements
- Author(s): H. Nakano and J. Yamauchi
- Source: Electronics Letters, Volume 16, Issue 18, p. 687 –688
- DOI: 10.1049/el:19800488
- Type: Article
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An antenna system consisting of a driven balanced helix and two parasitic helices is compared with a continuously wound balanced helix with the same total turns. The similarity in the radiation pattern, axial ratio and directive gain are found by theoretical investigation.
Single-ended fibre strain and length measurement in frequency domain
- Author(s): R. Kashyap and M.H. Reeve
- Source: Electronics Letters, Volume 16, Issue 18, p. 689 –690
- DOI: 10.1049/el:19800489
- Type: Article
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Changes in the received phase of a modulated signal propagating in an optical fibre can be used to monitor strain induced in the fibre with high sensitivity. Varying the frequency of the source allows the measurement of fibre length. A single-ended technique using a very stable frequency source is presented here.
Optimal excitation of multimode graded-index fibres in d.m.d. and d.m.a. measurements
- Author(s): J. Saijonmaa ; A.B. Sharma ; S.J. Halme
- Source: Electronics Letters, Volume 16, Issue 18, p. 690 –692
- DOI: 10.1049/el:19800490
- Type: Article
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A wave optics computational procedure to obtain optimally selective excitation in d.m.d. and d.m.a. measurements is presented. Good agreement with a Fourier optics approach is found. It is shown that for the optimal excitation of higher order mode groups (by increasing input beam offset) the beam spot size must be considerably reduced from that for the optimal excitation of the fundamental mode.
Optimised structure for preparing long ultra-low-loss single-mode fibres
- Author(s): B.J. Ainslie ; C.R. Day ; J. Rush ; K.J. Beales
- Source: Electronics Letters, Volume 16, Issue 18, p. 692 –693
- DOI: 10.1049/el:19800491
- Type: Article
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An optimised structure has been evolved for producing long lengths of ultra-low-loss single-mode fibre. Attenuation figures of 0.6 dB/km at 1.3 μm and 0.34 dB/km at 1.6 μm have been achieved in fibres up to 17.1 km in length. The absorption due to OH impurity has been reduced to <3 dB/km at 1.39 μm.
Effect of p-doping on carrier lifetime and threshold current density of 1.3 μm GaInAsP/InP lasers by liquid-phase epitaxy
- Author(s): W. Ng and Y.Z. Liu
- Source: Electronics Letters, Volume 16, Issue 18, p. 693 –695
- DOI: 10.1049/el:19800492
- Type: Article
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A correlation was found between the variation of the threshold current density and carrier lifetime with acceptor concentration in the active layer. An injected electron concentration of 2.5–3 × 1018/cm3, independent of the acceptor concentration in the active layer, was found at the lasing threshold.
Refracted power technique for cutoff wavelength measurement in single-mode waveguides
- Author(s): V.A. Bhagavatula ; W.F. Love ; D.B. Keck ; R.A. Westwig
- Source: Electronics Letters, Volume 16, Issue 18, p. 695 –696
- DOI: 10.1049/el:19800493
- Type: Article
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A technique to measure the local (2–3 mm) values of cutoff wavelength λc in single-mode waveguides is described. The technique, insensitive to the length of waveguide used, involves the spectral measurement of refracted power. The feasibility of using the cutoff wavelength determined by this technique to predict the zero dispersion wavelength is also studied.
Effective data collection aperture in long-wavelength imaging systems
- Author(s): J.C. Bennett and S. Abdul-Jauwad
- Source: Electronics Letters, Volume 16, Issue 18, p. 696 –698
- DOI: 10.1049/el:19800494
- Type: Article
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A new configuration for the acquisition of data in long-wavelength imaging systems is described and is shown to optimise the data collection capabilities of the aperture used. The feasibility of the approach has been demonstrated at a free-space ultrasonic frequency of 40 kHz and typical imagery is presented.
Ultimately low OH content v.a.d. optical fibres
- Author(s): T. Moriyama ; O. Fukuda ; K. Sanada ; K. Inada ; T. Edahiro ; K. Chida
- Source: Electronics Letters, Volume 16, Issue 18, p. 698 –699
- DOI: 10.1049/el:19800495
- Type: Article
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Ultimately low OH content optical fibres with 1.2% refractive-index difference and 80 μm core diameter have been successfully obtained by dehydrating a v.a.d.-made porous preform under optimised conditions. The loss increase at 1.39 μm due to residual OH ions was only 0.04 dB/km. Accordingly, the measured attenuation curve can be resolved into contribution from the intrinsic loss mechanism with the additional low waveguide imperfection loss.
Fabrication of completely OH-free v.a.d. fibre
- Author(s): F. Hanawa ; S. Sudo ; M. Kawachi ; M. Nakahara
- Source: Electronics Letters, Volume 16, Issue 18, p. 699 –700
- DOI: 10.1049/el:19800496
- Type: Article
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An extremely low OH v.a.d. fibre has been fabricated. The attained minimum OH concentration is estimated to be 0.8 ppb and optical loss below 1 dB/km is realised in the extended wavelength range from 1.1 to 1.7 μm.
Tunable magnetostatic surface wave demultiplexing filter/switch
- Author(s): H. Sasaki and N. Mikoshiba
- Source: Electronics Letters, Volume 16, Issue 18, p. 700 –701
- DOI: 10.1049/el:19800497
- Type: Article
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A tunable frequency demultiplexing filter/switch has been realised on a magnetostatic surface wave delay line by employing both parallel-bar structure and meander line structure as output transducers together with a wideband single-line input transducer. Switching from one output terminal to the other has been obtained by changing the applied magnetic field from 57 Oe to 78 Oe at 1.1 GHz.
Low temperature diffusion process for fabricating optical waveguides in glass
- Author(s): C.W. Pitt ; A.A. Stride ; R.I. Trigle
- Source: Electronics Letters, Volume 16, Issue 18, p. 701 –703
- DOI: 10.1049/el:19800498
- Type: Article
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A thermal evaporation source provides a vapour stream of metallic dopant directed at a glass substrate. The metal atoms thermally diffuse into the glass surface and are accelerated through the substrate by an electric field. The doped glass forms an optical waveguide stripe.
Early voltage uniqueness test for bipolar junction transistors
- Author(s): B.L. Hart
- Source: Electronics Letters, Volume 16, Issue 18, p. 703 –705
- DOI: 10.1049/el:19800499
- Type: Article
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A technique is described for the direct visual comparison of the common emitter output characteristic—at a chosen collector current, in the forward active mode—of a junction transistor subjected alternately to base-emitter voltage drive and base current drive. The Early effect is characterised by a unique parameter, the Early voltage, only if the two curves can be shown to exhibit coincidence in the nonsaturated region.
High efficiency 90 GHz InP Gunn oscillators
- Author(s): J.D. Crowley ; J.J. Sowers ; B.A. Janis ; F.B. Fank
- Source: Electronics Letters, Volume 16, Issue 18, p. 705 –706
- DOI: 10.1049/el:19800500
- Type: Article
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High efficiency InP Gunn devices and oscillators have been developed for the millimetre wave range. At approximately 90 GHz, the highest c.w. efficiency measured was 4.7% and the highest pulsed efficiency was 6.3%. Output powers of 126 mW c.w. and 236 mW pulsed have been achieved.
Channelled substrate narrow stripe GaAs/(GaAl)As lasers with quarter-wavelength facet coatings
- Author(s): R.G. Plumb and J.P. Curtis
- Source: Electronics Letters, Volume 16, Issue 18, p. 706 –707
- DOI: 10.1049/el:19800501
- Type: Article
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Channelled substrate narrow stripe GaAs/(GaAl)As lasers with quarter-wavelength antireflection coatings are described. These devices have low thresholds, broad spectra, high external quantum efficiencies and operate up to 10 mW in the fundamental transverse mode.
Surface passivation of inversion layer m.i.s. solar cells
- Author(s): Y.W. Lam ; M.A. Green ; L.W. Davies
- Source: Electronics Letters, Volume 16, Issue 18, p. 707 –708
- DOI: 10.1049/el:19800502
- Type: Article
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Inversion layer m.i.s. solar cells rely on the charge-inducing properties of antireflection (a.r.) coatings to achieve good device performance. It has previously been shown that these properties reduce with time due to build-up of an equilibrium charge density on the outside of the a.r. coating. Although devices can be designed to accommodate this, considerable relaxation in design constraints could be achieved if it were possible to develop techniques for preventing this effect. Results with a technique based on surfactants are described.
High frequency stability of laser diode for heterodyne communication systems
- Author(s): F. Favre and D. le Guen
- Source: Electronics Letters, Volume 16, Issue 18, p. 709 –710
- DOI: 10.1049/el:19800503
- Type: Article
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The emission frequency of a single-mode GaAlAs laser diode was locked to a Fabry-Perot interferometer reference by using a high sensitivity and fast response feedback loop controlling the injection current. Long-term fluctuations have been reduced to 8 MHz with a short-term jitter less than 1.5 MHz. These figures are consistent with the requirements of heterodyne communication systems above 140 Mbit/s.
Effect of edge region on crosspolar performance of dichroic plate
- Author(s): R. Cahill and E.A. Parker
- Source: Electronics Letters, Volume 16, Issue 18, p. 710 –712
- DOI: 10.1049/el:19800504
- Type: Article
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The influence of the edge region of a waveguide dichroic plate is examined through a series of experiments involving modifications to the ground plane surrounding the area occupied by the guides. Crosspolar levels as high as −23 dB can be produced by the edge but with proper design can be reduced below −33 dB.
Single-polarisation single-mode optical fibre with refractive-index pits on both sides of core
- Author(s): T. Okoshi and K. Oyamada
- Source: Electronics Letters, Volume 16, Issue 18, p. 712 –713
- DOI: 10.1049/el:19800505
- Type: Article
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A new refractive-index distribution for realising a single-polarisation single-mode optical fibre is proposed. This distribution features two pits, on either side of the core. The propagation characteristics are calculated by the two-dimensional finite-element method. The relative birefringence δβ/βav is 1 ∼ 2.5 × 10−4 when core/cladding index difference is 1%.
High sensitivity InP/InGaAs heterojunction phototransistor
- Author(s): J.C. Campbell ; A.G. Dentai ; C.A. Burrus ; J.F. Ferguson
- Source: Electronics Letters, Volume 16, Issue 18, p. 713 –714
- DOI: 10.1049/el:19800506
- Type: Article
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Back-illuminated InP/InGaAs heterojunction phototransistors are described. These devices exhibit a low-level optical gain of 40 at 1 nW of incident power which represents a 1000 × improvement in sensitivity over previously reported phototransistors. The maximum gain is 1000 at 5 μW input. The response is relatively flat from 0.95 μm to 1.65 μm wavelength.
Double-stimulus quality rating method for television digital codecs
- Author(s): T.A. White and J.W. Allnatt
- Source: Electronics Letters, Volume 16, Issue 18, p. 714 –716
- DOI: 10.1049/el:19800507
- Type: Article
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Results are presented showing the development of a subjective method for the assessment of television digital codecs which preserves many of the features of the existing single-stimulus method employed for television transmission impairments. Rating standards are found to be highly stable in the presence of changes in the general level of impairment.
InP/InGaAsP avalanche photodiodes with new guard ring structure
- Author(s): F. Osaka ; K. Nakazima ; T. Kaneda ; T. Sakurai ; N. Susa
- Source: Electronics Letters, Volume 16, Issue 18, p. 716 –717
- DOI: 10.1049/el:19800508
- Type: Article
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A new guard ring structure for InP/InGaAsP avalanche photodiodes is described, which makes use of the impurity concentration difference between two InP epitaxial layers. The guard ring effect gives a low dark current and uniform multiplication characteristics at λ = 1.29 μm.
Optimum antenna separation for space diversity in l.o.s. radio links over flat ground
- Author(s): J.A. Garcia-Lopez and V. Casares-Giner
- Source: Electronics Letters, Volume 16, Issue 18, p. 717 –718
- DOI: 10.1049/el:19800509
- Type: Article
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In line-of-sight radio links over flat terrain or water, a general formula to calculate the antenna separation for space diversity is not appropriate because of the risk of simultaneous fading. A method for determining such a separation is shown and its implementation is described exactly and approximately.
Erratum: Error rates of phase-modulated signals in multilink system with interference
- Author(s): I.M. Kostić
- Source: Electronics Letters, Volume 16, Issue 18, page: 718 –718
- DOI: 10.1049/el:19800510
- Type: Article
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Erratum: Multiplexer logic circuit design using cubical complexes
- Author(s): A.B. Ektare and D.P. Mital
- Source: Electronics Letters, Volume 16, Issue 18, page: 718 –718
- DOI: 10.1049/el:19800511
- Type: Article
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