Online ISSN
1350-911X
Print ISSN
0013-5194
Electronics Letters
Volume 23, Issue 10, 7 May 1987
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Volume 23, Issue 10
7 May 1987
Higher-density single-mode optical fibre cables than 1 fibre/mm2, containing hundreds of fibres
- Author(s): Y. Katsuyama ; S. Hatano ; K. Hogari ; T. Kokubun
- Source: Electronics Letters, Volume 23, Issue 10, p. 481 –482
- DOI: 10.1049/el:19870349
- Type: Article
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A slotted-rod structure was investigated to obtain the maximum fibre density of high-fibre-count cables. A 500-fibre cable with a fibre density of 1.5 fibres/mm2 was designed and manufactured. The manufactured cable was composed of 10-fibre ribbons inserted into the designed slots. The optical losses of the cabled single-mode fibres were confirmed to be stable at 1.3 and 1.55 μm. This cable has the highest fibre density of existing optical cables.
Instabilities in numerical inversion of Laplace transforms using Taylor series approach
- Author(s): R. Unnikrishnan and A.V. Mathew
- Source: Electronics Letters, Volume 23, Issue 10, p. 482 –483
- DOI: 10.1049/el:19870350
- Type: Article
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p.
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–483
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Recently Chung and Sun reported a technique for the numerical inversion of Laplace transforms using Taylor series. In the letter we point out that the implementation of this method involves the inversion of an n × n Hilbert matrix. This results in numerical instability and makes the algorithm unreliable. Alternative approaches which give a least-square fit for the solution are also identified.
Case study of line-of-sight microwave multipath propagation
- Author(s): K.H. Craig and G.R. Kennedy
- Source: Electronics Letters, Volume 23, Issue 10, p. 483 –484
- DOI: 10.1049/el:19870351
- Type: Article
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A case study of multipath fading on a microwave line-of-sight link is presented. Concurrent measurements by an aircraft-mounted refractometer are shown. Strong vertical and horizontal refractivity gradients are observed due to ground-based layering. Ray tracing shows three rays with subnanosecond separation and an angle-of-arrival spread of 0-4°. The fade is non-minimum-phase.
All-optical switching in prism coupling to semiconductor-doped glass waveguides
- Author(s): G. Assanto ; A. Gabel ; C.T. Seaton ; G.I. Stegeman ; C.N. Ironside ; T.J. Cullen
- Source: Electronics Letters, Volume 23, Issue 10, p. 484 –485
- DOI: 10.1049/el:19870352
- Type: Article
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Optical switching was observed within a pulse train during prism coupling into a nonlinear potassium-ion-exchanged semiconductor-doped-glass waveguide with modified composition. An interpretation of the observed phenomenon is given in terms of a slow (probably thermal) nonlinearity.
Low-threshold GaAs/GaAlAs buried heterostructure laser with an ion-beam-etched quarter ring cavity
- Author(s): P. Sansonetti ; H. Riboth ; J. Brandon ; L. Menigaux ; L. Dugrand ; N. Bouadma
- Source: Electronics Letters, Volume 23, Issue 10, p. 485 –487
- DOI: 10.1049/el:19870353
- Type: Article
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–487
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GaAs/GaAlAs buried quarter ring lasers with a constant stripe shape along the cavity were fabricated by ion beam etching. Threshold currents of 23 mA were obtained for 2 μm-wide and 430 μm-long cavities on a wafer, for which the broad-area threshold current density was l.7 kA/cm2. This structure leaves the rest of the wafer free for optoelectronic integration.
Channel reallocatable onboard baseband switch
- Author(s): S. Suzuki ; M. Yabusaki ; T. Arita ; F. Ishino
- Source: Electronics Letters, Volume 23, Issue 10, p. 487 –488
- DOI: 10.1049/el:19870354
- Type: Article
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The letter proposes a novel single-buffer single-stage time switch architecture enabling channel reallocation with no bit dropout for onboard baseband switches. By applying dedicated LSIs to the breadboard model, a baseband switch having 104 channels, a scale of 30 × 30 × 30cm, a weight of 25kg and a power consumption level of 30W can be achieved.
Differential phase contrast acoustic microscopy using tilted transducers
- Author(s): M. Nikoonahad
- Source: Electronics Letters, Volume 23, Issue 10, p. 489 –490
- DOI: 10.1049/el:19870355
- Type: Article
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A differential phase contrast reflection acoustic microscope is reported. In this system the lens is illuminated by two beams, tilted with respect to the lens axis. This leads to two adjacent off-axis foci at the focal plane of the lens. The phase difference between the signals received from these two foci provides the image contrast. Experiments at 10MHz are described and illustrated by preliminary results.
Hybrid optical bistability based on increasing absorption in depletion layer of an Si Schottky seed device
- Author(s): D. Jäger ; F. Forsmann ; H.-C. Zhai
- Source: Electronics Letters, Volume 23, Issue 10, p. 490 –492
- DOI: 10.1049/el:19870356
- Type: Article
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We report novel experimental results of cavityless optical bistability in the depletion layer of an Si Schottky SEED with CW light of 1.06μm at room temperature, where the induced absorption is largely enhanced by electrooptical feedback.
Pressure dependence of threshold current and carrier lifetime in 1.55 μm GaInAsP lasers
- Author(s): K.C. Heasman ; A.R. Adams ; P.D. Greene ; G.D. Henshall
- Source: Electronics Letters, Volume 23, Issue 10, p. 492 –493
- DOI: 10.1049/el:19870357
- Type: Article
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The threshold current and carrier lifetime were measured as a function of pressure in oxide stripe and IRW GaxIn1−xAsyP1−y 1.55 μm lasers. The results indicate that intervalence band absorption is a more important loss mechanism than the combined effects of Auger recombination, loss over the barrier and recombination through defects.
Laser recrystallised SOI with periodical seeding filled by selective epitaxial growth
- Author(s): J.L. Regolini ; D. Dutartre ; D. Bensahel ; L. Karapiperis ; G. Garry ; D. Dieumegard
- Source: Electronics Letters, Volume 23, Issue 10, p. 493 –494
- DOI: 10.1049/el:19870358
- Type: Article
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A periodic seeding technique for obtaining thin silicon films on an insulator (SOI) by laser recrystallisation is described. Two types of seed structure as well as their orientations relative to the scan direction are discussed. Geometrical parameters are optimised to obtain 35μm-wide defect-free SOI stripes across 4in (101-6mm) silicon wafers.
Identity-based conference key distribution system
- Author(s): K. Koyama
- Source: Electronics Letters, Volume 23, Issue 10, p. 495 –496
- DOI: 10.1049/el:19870359
- Type: Article
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We propose an identity-based key distribution system to generate a common secret conference key for three or more users. Users are connected in a ring so that each user sends messages to the neighbouring user to generate a conference key. These messages are authenticated using each user's identification information.
Combined space and adaptive correlation diversity in the CD900 system
- Author(s): W.H. Lam and R. Steele
- Source: Electronics Letters, Volume 23, Issue 10, p. 496 –498
- DOI: 10.1049/el:19870360
- Type: Article
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The CD900 multiple-access system is enhanced by employing adaptive correlation diversity coupled with either switched or combining diversity. The residual average probability of symbol error is eliminated for probability of symbol error Pe>10−5, and the channel SNR is within 5 dB of that for the AWGN channel when Pe=10−3.
Novel method for realising lossless floating immittance using current conveyors
- Author(s): M. Higashimura and Y. Fukui
- Source: Electronics Letters, Volume 23, Issue 10, p. 498 –499
- DOI: 10.1049/el:19870361
- Type: Article
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A novel method for realising lossless floating immittance using second-generation current conveyors (CCIIs) is proposed. By introducing the nullator-norator technique, many simulation circuits can be derived systematically.
Validity of kL evaluation by stopband method for λ/4 DFB lasers with low reflecting facets
- Author(s): J. Kinoshita
- Source: Electronics Letters, Volume 23, Issue 10, p. 499 –501
- DOI: 10.1049/el:19870362
- Type: Article
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The validity of the kL values estimated from the subthreshold stopband width of λ/4-shifted DFB lasers with low reflecting facets is discussed quantitatively. The misestimation probability is calculated by varying the phase of the residual field reflectances at both facets. The results show that the residual reflectivity should be less than 0.05% to estimate the kL value validly when the true value of kL is less than 2.0.
Monolithic integrated waveguide photodetector
- Author(s): S. Chandrasekhar ; J.C. Campbell ; A.G. Dentai ; G.J. Qua
- Source: Electronics Letters, Volume 23, Issue 10, p. 501 –502
- DOI: 10.1049/el:19870363
- Type: Article
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An InGaAs photodetector for detection in the 1.0–1.5μm wavelength range has been integrated at the end of and above a ridge waveguide in InP. The waveguides were in n−-InP/n+-InP and had an average propagation loss of 3dB/cm at 1.15μm. The reflection losses were 3dB and the coupling loss was 2dB. The photodetector was an InGaAs photoconductor lattice-matched to InP and exhibited a bias-dependent optical gain of up to 2.5 with a unity-gain quantum efficiency of 49% at 1.15μm. 25% of the guided light was absorbed by the photoconductor. The speed of the photoconductor was found to be bias-dependent, varying from 10 ns to 150 ns rise/fall times.
Multivalued dynamic circuits
- Author(s): J.L. Huertas ; A. Barriga ; G. Sánchez-Gómez
- Source: Electronics Letters, Volume 23, Issue 10, p. 502 –504
- DOI: 10.1049/el:19870364
- Type: Article
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A new family of multivalued logic circuits is presented. These circuits exhibit some appealing features: they are the first MV dynamic operators reported in the literature, they implement the Vranesic-Smith-Lee algebra (which is specially suited for arithmetic operations), and their performance has been found to be similar to binary counterparts by simulation.
Supercomplementary sets of sequences
- Author(s): S.Z. BudiŠin
- Source: Electronics Letters, Volume 23, Issue 10, p. 504 –506
- DOI: 10.1049/el:19870365
- Type: Article
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In the letter we propose a general method for generating a set of complementary sequences with special properties. In addition to autocorrelation function complementarity, these sequences exhibit complementarity of the crosscorrelation between the original sequence and the ‘deformed’ sequence. The consequence of this property is ambiguity function complementarity. Many known complementary sets of sequences are special cases of the presented class of sequences. Properties useful in radar applications are also discussed.
Single-polarisation single-mode guidance in stress-induced birefringence fibres with lossy stress-applying sections
- Author(s): K.S. Chiang
- Source: Electronics Letters, Volume 23, Issue 10, p. 506 –507
- DOI: 10.1049/el:19870366
- Type: Article
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When the refractive index of the stress-applying sections in a stress-induced birefringence fibre lies between the effective indices of the two polarisation modes, the polarisation mode with lower effective index is essentially guided by the stress-applying sections. Single-polarisation guidance can thus be achieved by introducing absorption loss in the stress-applying sections.
New pseudorandom encoding technique for shaft encoders with any desired resolution
- Author(s): E.M. Petriu
- Source: Electronics Letters, Volume 23, Issue 10, p. 507 –509
- DOI: 10.1049/el:19870367
- Type: Article
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A new pseudorandom, two-track encoding procedure for absolute-type shaft encoders with any number of disc sectors has been developed. For n-bit resolution the new method requires only n + m reading heads, where 2m-1 < n≤2m. This is notably better than the 2n–1 reading heads required by an earlier version.
Monolithic integration of a transverse-junction stripe laser and metal-semiconductor field-effect transistors on a semi-insulating GaAs substrate
- Author(s): J. Ohta ; K. Kuroda ; K. Mitsunaga ; K. Kyuma ; K. Hamanaka ; T. Nakayama
- Source: Electronics Letters, Volume 23, Issue 10, p. 509 –510
- DOI: 10.1049/el:19870368
- Type: Article
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–510
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A buried transverse-junction stripe laser diode and two metal-semiconductor field-effect transistors were monolithically integrated using two-step molecular beam epitaxy. This device had an almost flat surface well suited for the integration. High performance and high-speed operation (<1GHz) have been demonstrated in this integrated device for the first time.
Observation of two-colour gain saturation in an optical amplifier
- Author(s): R.M. Jopson ; K.L. Hall ; G. Eisenstein ; G. Raybon ; M.S. Whalen
- Source: Electronics Letters, Volume 23, Issue 10, p. 510 –512
- DOI: 10.1049/el:19870369
- Type: Article
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We have measured changes in small-signal gain spectra of an optical amplifier caused by the presence of a second signal at a different wavelength. The results are applicable to the use of amplifiers in wavelength-division-multiplexed systems. These spectra also provide a measurement of the spectrum of α, the linewidth-broadening factor.
High-efficiency quasimicrowave GaAs FET power amplifier
- Author(s): T. Nojima ; S. Nishiki ; K. Chiba
- Source: Electronics Letters, Volume 23, Issue 10, p. 512 –513
- DOI: 10.1049/el:19870370
- Type: Article
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A 1.7 GHz-based class-F GaAs FET amplifier is proposed. To achieve high-efficiency performance, a precisely adjustable terminating circuit constructed with lumped elements is introduced. Power-added efficiency of 68% at 1.5 W output is attained with the amplifier.
Polarisation-insensitive heterodyne detection using polarisation scrambling
- Author(s): T.G. Hodgkinson ; R.A. Harmon ; D.W. Smith
- Source: Electronics Letters, Volume 23, Issue 10, p. 513 –514
- DOI: 10.1049/el:19870371
- Type: Article
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Theoretical and experimental results are presented which demonstrate that polarisation diversity can be implemented by rapidly stepping the polarisation of an optical signal between orthogonal states prior to transmission through a birefringent medium.
SAW quartz cuts with low stress and temperature sensitivity
- Author(s): E. Bigler ; D. Hauden ; G. Theobald
- Source: Electronics Letters, Volume 23, Issue 10, p. 514 –516
- DOI: 10.1049/el:19870372
- Type: Article
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The effects on Rayleigh wave velocity of strains and displacement gradients induced by isotropic in-plane stresses are modelled for a thin plate of quartz crystal. The stress sensitivity of SAW devices is calculated as a function of the quartz anisotropy. Comparison with loci of zero first-order temperature coefficients leads to the expectation of quartz cuts for SAW oscillator applications with low sensitivity to stress and temperature.
Exciton electroabsorption at room temperature in InGaAs/InP multiquantum-well structures grown by atmospheric-pressure MOCVD
- Author(s): A.J. Moseley ; M.D. Scott ; P.J. Williams ; R.H. Wallis ; J.I. Davies ; J.R. Riffat
- Source: Electronics Letters, Volume 23, Issue 10, p. 516 –518
- DOI: 10.1049/el:19870373
- Type: Article
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Sharp excitonic absorption features have been observed in MOCVD-grown InGaAs/InP multiquantum-well structures via a study of the spectral dependence of the photocurrent characteristics of a PIN diode containing the multiquantum wells in the intrinsic region. The first observation of a shift of excitonic peak wavelength with an applied electric field is reported for this material system.
Properties of quarter-wave-shifted DFB lasers in the presence of a taper
- Author(s): L.D. Westbrook
- Source: Electronics Letters, Volume 23, Issue 10, p. 518 –520
- DOI: 10.1049/el:19870374
- Type: Article
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The deleterious effect of a taper on the properties of quarterwave-shifted DFB lasers is analysed to assess the tolerance of these potentially useful single-frequency lasers to variations in epitaxial layer thickness, composition or in the DFB grating period. The maximum tolerable variation in any of these parameters is shown to be relatively insensitive to the grating coupling strength. The maximum tolerable thickness variation depends principally on the derivative of the laser waveguide effective index with respect to epilayer thickness and, for typical diode parameters, lies in the range 150–1500 Å.
Design parameters for a 1.3μm connectorised low-cost laser package for subscriber loop using graded-index lenses
- Author(s): L.A. Reith and J.W. Mann
- Source: Electronics Letters, Volume 23, Issue 10, p. 520 –521
- DOI: 10.1049/el:19870375
- Type: Article
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A 1.3μm laser mounted in a low-cost compact disc package has been coupled to single-mode fibre using two graded-index lenses. Here we present results of calculations showing how to pick lens pitches for given coupling efficiency/sensitivity trade-offs. In addition, we note that the effective angular alignment can be quite sensitive, and propose a means of avoiding this difficulty.
Azimuthal filtering technique for effective LP11 cutoff wavelength measurement in optical fibres
- Author(s): J.M. Blondy ; A.M. Blanc ; M. Clapeau ; P. Facq
- Source: Electronics Letters, Volume 23, Issue 10, p. 522 –523
- DOI: 10.1049/el:19870376
- Type: Article
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Azimuthal periodicities vanish in the near- and far-field patterns when the LP11 mode reaches the cutoff point. This criterion leads to a simple, fast and accurate method for effective cutoff wavelength determination in monomode optical fibres.
All single-mode optical fibre wavelength-tunable WDM with very narrow pass/stopband separations
- Author(s): S.P. Shipley and A. El Fatatry
- Source: Electronics Letters, Volume 23, Issue 10, p. 523 –524
- DOI: 10.1049/el:19870377
- Type: Article
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A single-mode all-fibre wavelength-division multiplexer (periodic wavelength filter) exhibiting very narrow separations (̃1 nm) between adjacent pass- and stopbands has been fabricated. The wavelengths at which this device has stop- and passbands may be varied by means of an external electrical control while maintaining a nearly constant band separation. Stopband extinctions in excess of 20 dB are reported for band separations of ˜30nm.
Narrow-linewidth laser with a prism grating/GRIN rod lens combination serving as external cavity
- Author(s): J. Wittmann and G. Gaukel
- Source: Electronics Letters, Volume 23, Issue 10, p. 524 –525
- DOI: 10.1049/el:19870378
- Type: Article
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An external cavity laser transmitter module with only 20 mm cavity length is presented. A prism grating is used as a frequency-selective reflector. The coupling element between the laser diode and the prism grating is a permanently attached GRIN rod lens. Linewidths below 500 kHz at an output power of approximately 2mW have been reached with this compact set-up.
2.4 W CW 770 nm laser arrays with nonabsorbing mirrors
- Author(s): D.F. Welch ; W. Streifer ; R.L. Thornton ; T. Paoli
- Source: Electronics Letters, Volume 23, Issue 10, p. 525 –527
- DOI: 10.1049/el:19870379
- Type: Article
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Laser arrays have been fabricated with silicon-impurityinduced disordered nonabsorbing mirrors (windows) to enhance the maximum CW power output. The power output was thermally limited for a 100 μm-aperture device to 2.4 W CW while catastrophic failure occurred under pulsed conditions at 3.5 W in a 100 μs pulse and increased to 22 W for a 50 ns pulse. The emission wavelength of these diodes is 770 nm.
110 GHz high-efficiency photodiodes fabricated from indium tin oxide/GaAs
- Author(s): D.G. Parker ; P.G. Say ; A.M. Hansom ; W. Sibbett
- Source: Electronics Letters, Volume 23, Issue 10, p. 527 –528
- DOI: 10.1049/el:19870380
- Type: Article
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An indium tin oxide/GaAs photodiode is reported with a –3 dB bandwidth in excess of 110 GHz. This device exhibits an external quantum efficiency of > 25% (~0.2 A/W). The device is mounted enabling direct measurements of bandwidth to be made using external mixers and a high-frequency spectrum analyser.
Al0.45Ga0.55As/GaAs HEMTs grown by MOVPE exhibiting high transconductance
- Author(s): A.L. Powell ; P. Mistry ; J.S. Roberts ; P.I. Rockett
- Source: Electronics Letters, Volume 23, Issue 10, p. 528 –529
- DOI: 10.1049/el:19870381
- Type: Article
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We report results of Al0.45Ga0.55As/GaAs HEMTs grown by atmospheric-pressure MOVPE. The 1 μm-gate-length devices exhibited extrinsic room-temperature transconductances as high as 295mS/mm, which we believe to be the best DC performance to date for devices utilising such a high Al mole fraction.
New lossless tunable floating FDNR simulation using two current conveyors and an INIC
- Author(s): M. Higashimura and Y. Fukui
- Source: Electronics Letters, Volume 23, Issue 10, p. 529 –531
- DOI: 10.1049/el:19870382
- Type: Article
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Four new lossless tunable floating FDNR simulation circuits using two current conveyors (CCIIs) and a current-inversion negative immittance convertor (INIC) as active elements are proposed. The circuits have the following advantages: (i) use of only two CCIIs with the minimum number of passive elements; (ii) extremely low active sensitivities of realised FDNR; (iii) no requirements for component matching; (iv) tunability of the FDNR value through a single resistor; and (v) applicability for the simulation of higher-order immittance.
New accurate and simple equivalent circuit for circular E-plane bends in rectangular waveguide
- Author(s): P.L. Carle
- Source: Electronics Letters, Volume 23, Issue 10, p. 531 –532
- DOI: 10.1049/el:19870383
- Type: Article
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A new accurate and simple equivalent circuit for circular E-plane bends in rectangular waveguide is shown. It can be used for any curvature radius and waveguide type. The experimental results shown in the letter agree well with the computed frequency programme. Moreover, a value of curvature radius that involves minimum input reflection over a given frequency band is calculated.
Proposal of an optical triggering scheme for bistable semiconductor lasers: combination with photoconductors
- Author(s): H.-F. Liu ; Y. Hashimoto ; T. Kamiya
- Source: Electronics Letters, Volume 23, Issue 10, p. 532 –534
- DOI: 10.1049/el:19870384
- Type: Article
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A cascadable optical triggering scheme for a bistable injection laser is proposed. By combining a tandem-structure bistable semiconductor laser and a pair of photoconductors, both switch-on and switch-off operations can be performed optically. Bistable operation at a repetitive frequency of 100 MHz is demonstrated with discrete devices.
Simple explicit formula for calculating the LP11 mode cutoff frequency
- Author(s): Jiang Shijun
- Source: Electronics Letters, Volume 23, Issue 10, p. 534 –535
- DOI: 10.1049/el:19870385
- Type: Article
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Based on Cheby̅shev's technique, a very convenient and efficient formula for calculating the LP11 mode cutoff frequency is derived. It is applicable to arbitrary index profiles including discrete numerical data from index profile measurements. The implementation is simple enough to be carried out easily on any pocket calculator with satisfactory accuracy for engineering applications.
Dielectrically shielded microstrip (DSM) lines
- Author(s): K. Chang and J. Klein
- Source: Electronics Letters, Volume 23, Issue 10, p. 535 –537
- DOI: 10.1049/el:19870386
- Type: Article
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Microstrip lines can be shielded by a dielectric cover to reduce the radiation loss. Experiments carried out using ring resonators showed the insertion loss can be substantially reduced. The effective dielectric constant of these shielded microstrip lines was calculated by the variational method. The results agree very well with experiment.
Femtosecond soliton Raman ring laser
- Author(s): A.S. Gouveia-Neto ; A.S.L. Gomes ; J.R. Taylor
- Source: Electronics Letters, Volume 23, Issue 10, p. 537 –538
- DOI: 10.1049/el:19870387
- Type: Article
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Pulses as short as 100 fs have been generated in standard single-mode optical fibre using a high-order soliton compression mechanism of the Raman component, synchronously excited in a ring laser geometry, pumped by a CW mode-locked Nd: YAG laser at 1.32μm.
Direct two's-complement algorithm for xy ± z
- Author(s): S. Vassiliadis ; M. Putrino ; E. Swartz
- Source: Electronics Letters, Volume 23, Issue 10, p. 538 –540
- DOI: 10.1049/el:19870388
- Type: Article
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An algorithm for the direct computation of multiplication with add or subtract operations is described for two's-complement notation requiring no additional rows and no negative terms as compared to a direct array multiplier.
High-speed waveguide optical modulator made from GaSb/AlGaSb multiple quantum wells (MQWs)
- Author(s): T.H. Wood ; E.C. Carr ; C.A. Burrus ; R.S. Tucker ; T.-H. Chiu ; W.-T. Tsang
- Source: Electronics Letters, Volume 23, Issue 10, p. 540 –542
- DOI: 10.1049/el:19870389
- Type: Article
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We observe a large electroabsorption effect in a GaSb/AlGaSb MQW, and use it to make a waveguide modulator with a 10.5 dB on/off ratio and a 12dB insertion loss at a wavelength of 1.55μm. Our high-speed device has a 3dB rolloff frequency of 3.7 GHz.
Duplex-diplex optical transmission in the 1300 nm and 1500 nm fibre windows: an installed system
- Author(s): A.R. Hunwicks and P.A. Rosher
- Source: Electronics Letters, Volume 23, Issue 10, p. 542 –544
- DOI: 10.1049/el:19870390
- Type: Article
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p.
542
–544
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Results are presented from the first installed route in which two separate optical transmission systems have been combined using duplex and wavelength-division multiplexing (WDM) on a single fibre. Fused biconical couplers and wavelength-division multiplexers were used on a 30 km installed single-mode optical fibre route. Details of the observed receiver crosstalk penalties are presented.
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