Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 20, Issue 17, 16 August 1984
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Volume 20, Issue 17
16 August 1984
Transmission experiment at 3 Gbit/s with close-spaced wavelength-division-multiplexed single-frequency lasers at 1.5 μm
- Author(s): N.A. Olsson ; R.A. Logan ; L.F. Johnson
- Source: Electronics Letters, Volume 20, Issue 17, p. 673 –674
- DOI: 10.1049/el:19840460
- Type: Article
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We report the first fibre-optic transmission experiment employing close-spaced wavelength division multiplexing and high-bit-rate modulation. Experimental results from transmission at 3 Gbit/s over 60 km of single-mode fibre using two wavelength-multiplexed single-frequency distri-buted-feedback lasers are described. The lasers, operating at 1.55 μm and with a wavelength separation of only 2.9 nm, are each modulated at 1.5 Gbit/s giving a total system capacity of 180 Gbitkm/s.
Ultra-low-distortion current-conversion technique
- Author(s): A. Fabre and P. Rochegude
- Source: Electronics Letters, Volume 20, Issue 17, p. 674 –676
- DOI: 10.1049/el:19840461
- Type: Article
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The generalised schemes of two different current-current convertor circuits (CCCS) each using a translinear input cell and two current mirrors are given. The distortion figures of these networks are presented and discussed for transfer current ratio values of unity.
Comment: Low-dispersion single-mode silica fibre with undoped core and three F-doped claddings
- Author(s): P.L. Francois ; F. Alard ; J.F. Bayon
- Source: Electronics Letters, Volume 20, Issue 17, page: 676 –676
- DOI: 10.1049/el:19840462
- Type: Article
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Reply: Low-dispersion single-mode silica fibre with undoped core and three F-doped claddings
- Author(s): H. Etzkorn and W.E. Heinlein
- Source: Electronics Letters, Volume 20, Issue 17, p. 676 –677
- DOI: 10.1049/el:19840463
- Type: Article
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Influence of metal-covered area on performance of solar cells
- Author(s): A.R. Es-Slassi ; P.H. Nguiyen ; J. Bottin ; T. Easwarakhantan ; S. Ravelet
- Source: Electronics Letters, Volume 20, Issue 17, p. 677 –678
- DOI: 10.1049/el:19840464
- Type: Article
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Analytical expressions are proposed showing that the efficiency and fill factor of solar cells depend on the three normalised parameters rm, rL and g. These expressions are obtained with a new theoretical model, representing the metal-covered area of the solar cell.
Monolithically integrated array of GaAlAs electroabsorption modulators
- Author(s): D.L. Robinson ; W.K. Marshall ; J. Katz ; J.S. Smith ; A. Yariv
- Source: Electronics Letters, Volume 20, Issue 17, p. 678 –680
- DOI: 10.1049/el:19840465
- Type: Article
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The operation of an eight-element monolithic array of GaAlAs electroabsorption modulators has been demonstrated. The single-mode waveguide modulators are implemented in a reverse-biased p-π-n heterojunction configuration, with centre-to-centre spacing of 9 μm between adjacent channels. This device may be useful for intensity modulation in high (spatial) resolution applications.
Computation of fundamental-mode spot size from far-field pattern of single-mode optical fibres
- Author(s): P.J. Samson
- Source: Electronics Letters, Volume 20, Issue 17, p. 680 –681
- DOI: 10.1049/el:19840466
- Type: Article
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It is shown how the mode spot size of a single-mode fibre can be computed from the far-field pattern. The method is accurate as it makes no Gaussian assumptions and holds for all fibre profiles. Comparisons are presented between our results and earlier empirical formulas.
Radiation characteristics and generation of higher-order modes of circular microstrip antennas
- Author(s): G. Kumar and L. Shafai
- Source: Electronics Letters, Volume 20, Issue 17, p. 681 –683
- DOI: 10.1049/el:19840467
- Type: Article
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p.
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The characteristics of higher-order modes of circular micro-strip antennas, such as radiation pattern, directivity, bandwidth, efficiency, and location of the feedpoint to match a 50Ωline, are studied, and the effects of varying the substrate parameters are investigated. A multifeed technique to generate any particular mode is also presented.
Novel architecture for a digital switching network
- Author(s): A. Jajszczyk
- Source: Electronics Letters, Volume 20, Issue 17, page: 683 –683
- DOI: 10.1049/el:19840468
- Type: Article
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A method for the design of economic PCM switching networks composed of uniform time-space elements is proposed. This method makes it possible to design switching networks having in many cases fewer stages and fewer elements than known networks.
High-speed optoelectronic sampling with semiconductor-laser pulsed coplanar photoconductor
- Author(s): P. Schmid and H. Melchior
- Source: Electronics Letters, Volume 20, Issue 17, p. 684 –685
- DOI: 10.1049/el:19840469
- Type: Article
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A semiconductor-laser strobed photoconductive sampling gate for the measurement of ultra-high-speed electronic signals on coaxial lines is reported. For the short response (<100 ps) and high responsivity (>0.1 A/W) at the 830 nm laser wavelength the sampling gate uses a miniaturised (8×8×1 μm) epitaxial GaAs photoconductor on a broadband tapered coplanar 50 Ω microwave structure.
Low-loss single-mode wavelength-division multiplexing with etched fibre arrays
- Author(s): J. Hegarty ; S.D. Poulsen ; K.A. Jackson ; I.P. Kaminow
- Source: Electronics Letters, Volume 20, Issue 17, p. 685 –686
- DOI: 10.1049/el:19840470
- Type: Article
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A 9-channel single-mode grating wavelength-division multiplexing scheme is demonstrated at 1.5 μm with insertion losses as low as 1.5 dB. An array of fibres with core-to-core spacing of 36 μm acts as a channel concentrator giving a channel separation of 20 Å and channel width of 2 Å.
Thin-film integrated band-rejection filters
- Author(s): K.U. Ahmed
- Source: Electronics Letters, Volume 20, Issue 17, p. 686 –688
- DOI: 10.1049/el:19840471
- Type: Article
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p.
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The letter presents some design data for some new band-rejection (BR) filter configurations of the integrated exponential R-C-KR structure consisting of two nonuniform resistive films, one having per-unit-length (PUL) series resistance R(x)=R0exp (kx) and the other KR(x), insulated from each other by a nonuniform dielectric film having PUL shunt capacitance C(r)=C0 exp (−kx), where all the symbols have their standard meanings. It is shown that the frequencies of interest in the band-rejection region and the width of the band-rejection region may be controlled to suit designer's requirements by suitable combination of the parameters K and k.
Design of monomode quadruple-clad fibres
- Author(s): P.L. Francois ; J.F. Bayon ; F. Alard
- Source: Electronics Letters, Volume 20, Issue 17, p. 688 –689
- DOI: 10.1049/el:19840472
- Type: Article
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The design of quadruple-clad profiles, leading to (truly) monomode fibres is described: an explicit set of parameters is proposed. Experimental results are presented, concerning a fibre with a dispersion smaller than ±0.5 ps/km nm and an attenuation around 0.3 dB/km, over the 1.5–1.65 μm wavelength interval.
Improved heat-sink design for coherent laser arrays
- Author(s): M.T. Tavis and E.M. Garmire
- Source: Electronics Letters, Volume 20, Issue 17, p. 689 –690
- DOI: 10.1049/el:19840473
- Type: Article
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A heat sink with a cap whose lateral dimensions match the width of a laser array will remarkably improve the temperature uniformity in the array facilitating phase-locked operation.
Existence of a 2n FFT algorithm with a number of multiplications lower than 2n+1
- Author(s): P. Duhamel and H. Hollmann
- Source: Electronics Letters, Volume 20, Issue 17, p. 690 –692
- DOI: 10.1049/el:19840474
- Type: Article
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p.
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First we give a decomposition of an FFT of length 2n into a number of one-dimensional polynomial products. If these products are computed with minimum multiplication algorithms, we show that the 2n FFT can be computed with less than 2n+1 nontrivial complex multiplications. A variation of this algorithm is also shown to give the same multiplication count as the ‘split-radix’ FFT.
1.53 μm DFB lasers by mass transport
- Author(s): B. Broberg ; F. Koyama ; Y. Tohmori ; Y. Suematsu
- Source: Electronics Letters, Volume 20, Issue 17, p. 692 –694
- DOI: 10.1049/el:19840475
- Type: Article
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DFB lasers emitting at λ=1.53 μm made by mass transport have been demonstrated. Output power exceeding 5 mW/ facet was obtained when operated in CW at room temperature. Single-longitudinal-mode operation with a minimum threshold current of 26 mA was achieved. No degradation can be observed after aging at 5 mW continuous power at room temperature for more than 1000 h.
Transverse junction stripe lasers using Si-doped GaAs/AlGaAs grown by MBE
- Author(s): K. Mitsunaga ; K. Fujiwara ; M. Nunoshita ; T. Nakayama
- Source: Electronics Letters, Volume 20, Issue 17, p. 694 –695
- DOI: 10.1049/el:19840476
- Type: Article
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p.
694
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Transverse junction stripe (TJS) laser diodes on a semi-insulating substrate have been fabricated using Si-doped GaAs/AlGaAs double-heterostructure layers grown by MBE. Room-temperature CW operation of the TJS laser with a low threshold current (30 mA) has been achieved.
Phase-locked injection laser arrays with nonuniform stripe spacing
- Author(s): D.E. Ackley
- Source: Electronics Letters, Volume 20, Issue 17, p. 695 –697
- DOI: 10.1049/el:19840477
- Type: Article
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A new type of phase-locked injection laser array which utilises nonuniform spacing between the lasing stripes has been studied. The variation in spacing alters the stripe-to-stripe coupling which modifies the array mode selection. Arrays that operate with a single far-field lobe have been fabricated.
Optimal data transmission filters
- Author(s): K. Huber and L.F. Lind
- Source: Electronics Letters, Volume 20, Issue 17, p. 697 –698
- DOI: 10.1049/el:19840478
- Type: Article
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–698
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In the letter new closed-form formulas (in terms of the poles) for a class of optimal data transmission filters are derived. These formulas always put the main sample point at the peak value of the impulse response.
Cutoff wavelength determination in single-mode optical fibres by measurement of equalisation wavelength
- Author(s): J.L. McMillan and S.C. Robertson
- Source: Electronics Letters, Volume 20, Issue 17, p. 698 –699
- DOI: 10.1049/el:19840479
- Type: Article
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A simple interferometric method for indirectly determining a value for the cutoff wavelength of single-mode optical fibres is described. The technique is accurate and no stringent requirements are placed on the experimental equipment.
The magnetotransistor effect
- Author(s): A.G. Andreou and C.R. Westgate
- Source: Electronics Letters, Volume 20, Issue 17, p. 699 –701
- DOI: 10.1049/el:19840480
- Type: Article
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p.
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A new physical mechanism, active in the base region of dual-collector lateral bipolar tranistors in the presence of a transverse magnetic field, is described in the letter. This mechanism induces a differential current flow from the two collectors, and is also responsible for an increase in the overall current gain.
Groove-guide directional couplers with improved bandwidth
- Author(s): J. Meiβner
- Source: Electronics Letters, Volume 20, Issue 17, p. 701 –702
- DOI: 10.1049/el:19840481
- Type: Article
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p.
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An exact analysis of the coupling properties of uniformly coupled groove guides with unequal phase constants is developed and confirmed with measurements. The results are applied to the construction of directional couplers with considerably improved bandwidth.
Coherent FSK transmitter using a negative feedback stabilised semiconductor laser
- Author(s): S. Saito ; O. Nilsson ; Y. Yamamoto
- Source: Electronics Letters, Volume 20, Issue 17, p. 703 –704
- DOI: 10.1049/el:19840482
- Type: Article
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p.
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An electrical negative frequency feedback scheme is applied to a semiconductor laser to improve its direct frequency modulation performance in an FSK transmitter. An error signal caused by imperfect FM response is extracted through heterodyne discrimination detection with a stable master laser and fed back to the FM semiconductor laser.
Synthesis of monomode fibre profiles using multivariate optimisation
- Author(s): B.P. Nelson ; K.J. Blow ; N.J. Doran
- Source: Electronics Letters, Volume 20, Issue 17, p. 704 –705
- DOI: 10.1049/el:19840483
- Type: Article
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p.
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The letter describes a new approach to the design of mono-mode fibres where the index profile is synthesised rather than analysed. The method we have developed is one of multi-variate optimisation in which the index profile itself is treated as a variable in order to find the optimum profile function for particular fibre properties. We include some particular examples which justify the validity of this approach.
Travelling-wave laser amplifier experiments at 1.5 μm
- Author(s): R.P. Webb and W.J. Devlin
- Source: Electronics Letters, Volume 20, Issue 17, p. 706 –707
- DOI: 10.1049/el:19840484
- Type: Article
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The gain of a 1.5 μm semiconductor travelling-wave amplifier has been measured with signals in different polarisation states, and the amplifier has been used as a repeater in a phase-modulated coherent system.
1.2 Gbit/s optical fibre transmission experiment over 113.7 km using a 1.528 μm distributed-feedback ridge-waveguide laser
- Author(s): P.J. Chidgey ; B.R. White ; M.C. Brain ; R.C. Hooper ; D.R. Smith ; P.P. Smyth ; P.J. Fiddyment ; A.W. Nelson ; L.D. Westbrook
- Source: Electronics Letters, Volume 20, Issue 17, p. 707 –709
- DOI: 10.1049/el:19840485
- Type: Article
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Optical fibre transmission experiments at 1.2 Gbit/s are reported over distances up to 113.7 km of conventional nondispersion-shifted fibre. The experimental system comprises a DFB laser, a PINFET and a parallel-processing regenerator. System penalties are observed which may be partly attributed to transient wavelength chirping and chromatic dispersion. Experiments using 83 km of dispersion shifted fibre show no penalties.
Test of phase-retrieval holography on the Onsala 20 m radiotelescope
- Author(s): J. Ellder ; L. Lundahl ; D. Morris
- Source: Electronics Letters, Volume 20, Issue 17, p. 709 –710
- DOI: 10.1049/el:19840486
- Type: Article
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p.
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The phase-retrieval method for the radio holography of reflector antennas has been tested. The 22 GHz water vapour maser source in Orion was observed to measure the infocus and defocused antenna power patterns. The aperture phase distribution was then derived by the Misell algorithm. An RMS phase error of 0.13 rad was achieved (0.14 mm). The surface resolution was about 1.6 m (between half amplitude points).
Erratum: Nonabsorbing mirror (NAM) CDH-LOC diode lasers
- Author(s): D. Botez and J.C. Connolly
- Source: Electronics Letters, Volume 20, Issue 17, page: 710 –710
- DOI: 10.1049/el:19840487
- Type: Article
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