Showing papers in "Electronics Letters in 1980"
TL;DR: In this paper, the authors proposed a method by which 50 kHz resolution can be obtained for measuring the spectrum of stabilised semiconductor laser with high spectral spread, and the principle, experimental set up and results are described.
Abstract: The spectral spread of the best stabilised semiconductor lasers has been reduced to several megahertz. Conventional spectroscopy techniques cannot offer a spectral resolution fine enough for measuring such a sharp spectrum. The letter proposes a novel method by which 50 kHz resolution can be obtained. The principle, experimental set-up and results are described.
917 citations
TL;DR: In this article, the authors describe new single-mode fiber optic devices which are completely equivalent to fractional wave plates of classical optics and employ a very simple configuration which uses the stress birefringence induced by bending the fibre.
Abstract: We describe new single-mode fibre optic devices which are completely equivalent to fractional wave plates of classical optics. They employ a very simple configuration which uses the stress birefringence induced by bending the fibre. Several devices can be combined to control the polarisation inside any single-mode fibre.
541 citations
TL;DR: In this paper, a technique for the fabrication of singlemode fiber optic directional couplers is presented for the single-mode optical fiber optic (SOMO) directional coupler.
Abstract: A technique is presented for the fabrication of single-mode fibre optic directional couplers. Properties of couplers made using this technique include stability and durability, continuous tunability to a power transfer of 70%, less than 10% loss, high insensitivity to polarisation, and high directivity.
318 citations
TL;DR: In this paper, a majority carrier rectifying device is demonstrated which is made in gallium arsenide by molecular beam epitaxy and exhibits thermionic transport with positive and negative bias.
Abstract: A new majority carrier rectifying device is demonstrated which is made in gallium arsenide by molecular beam epitaxy. It exhibits thermionic transport with positive and negative bias and the barrier height and degree of asymmetry in the I/V characteristic can be continuously varied. The device also shows a constant capacitance with bias.
261 citations
TL;DR: In this paper, it was shown that in multilayered heterojunction structures the effective impact ionisation rates for electrons and holes can be very different, even if they are the same in the basic bulk materials.
Abstract: Calculations are reported showing that in multilayered heterojunction structures the effective impact ionisation rates for electrons and holes can be very different, even if they are the same in the basic bulk materials. The reason for this is the difference in the band-edge discontinuities for electrons and holes and the lower phonon mean free path for holes in quantum well structures.
240 citations
TL;DR: A method of image enhancement by computer using the fuzzy set theoretic approach that involves extraction of fuzzy properties corresponding to pixels and then successive application of fuzzy operator `contrast intensification´ on the property plane is reported.
Abstract: A method of image enhancement by computer using the fuzzy set theoretic approach is reported. The algorithm involves extraction of fuzzy properties corresponding to pixels and then successive application of fuzzy operator `contrast intensification´ on the property plane. System performance with different indexes of fuzziness is demonstrated for an English script input.
132 citations
TL;DR: In this paper, a class of high sensitivity fiber-optic magnetic sensors has been developed and successfully tested in the laboratory for the first time, using magnetostrictive jacketing materials in conjunction with conventional single-mode optical fibres.
Abstract: A class of high sensitivity fibre-optic magnetic sensors has been developed and successfully tested in the laboratory for the first time. The magnetic sensors employ magnetostrictive jacketing materials in conjunction with conventional single-mode optical fibres. An all-fibre Mach-Zender interferometer was used to detect the magnetically induced changes in optical path length which arise because of strains transferred to the fibre from the magnetostrictive jacket.
126 citations
TL;DR: The first m.e.f.t. structure was reported in this paper, in which the channel near pinch-off is occupied by a two-dimensional electron gas accumulated at the interface of a GaAs(N)-AlxGa1−xAs (N) heterojunction.
Abstract: The first m.e.s.f.e.t. structure is reported in which the channel near pinch-off is occupied by a two-dimensional electron gas accumulated at the interface of a GaAs(N)-AlxGa1−xAs(N) heterojunction. Experimental data are in good agreement with theoretical calculations.
123 citations
TL;DR: In this article, a new optical fiber technique was proposed for measurement of the spatial distribution of physical fields, and the location of anomalous features in single polarisation state monomode optical fibres.
Abstract: A proposed new optical fibre technique will allow measurement of the spatial distribution of physical fields, and will also allow location of anomalous features in single polarisation state monomode optical fibres such as are under discussion for very high bandwidth communication.
107 citations
TL;DR: In this paper, a temperature-dependent nonradiative carrier loss was identified in 1.27 μm (GaIn)(AsP)/InP d.h. lasers as being responsible for the high sensitivity of threshold current to temperature.
Abstract: A temperature-dependent nonradiative carrier loss is identified in 1.27 μm (GaIn)(AsP)/InP d.h. lasers as being responsible for the high sensitivity of threshold current to temperature. It varies according to an activation energy of between 0.09 and 0.13 eV and is superlinear in carrier concentration.
102 citations
TL;DR: In this paper, an a.f.c. (automatic frequency control) experiment using a Peltier cooling element is described, where the frequency fluctuation can be reduced to below 10 MHz.
Abstract: In the somewhat distant future, heterodyne-type optical communications will appear, increasing channel capacity and repeater separation. At present, the greatest difficulty is the frequency drift of lasers. The letter describes an a.f.c. (automatic frequency control) experiment using a Peltier cooling element; it is shown that the frequency fluctuation can be reduced to below 10 MHz.
TL;DR: The first operation of an integrated p-i-n-photodiode/f.t.-amplifier on a single wafer of In0.53Ga0.47 was reported in this article.
Abstract: The first operation of an integrated p-i-n-photodiode/f.e.t.-amplifier on a single wafer of In0.53Ga0.47As grown lattice matched to an InP substrate is reported.
TL;DR: In this paper, the authors proposed a method for the generation of short optical pulses from injection laser pulses for spectroscopy and high data rate communication for the maturing injection laser.
Abstract: Generation of short optical pulses from injection lasers is a topic of current interest. There is a great opportunity both in spectroscopy and high data rate communication for the maturing injection lasers.
TL;DR: In this paper, the extinction ratios up to 14 dB between orthogonal polarisations have been realized, by grinding off the cladding on one side of a singlemode fiber and evaporating metal onto the polished surface.
Abstract: A polariser is formed by grinding off the cladding on one side of a single-mode fibre and evaporating metal onto the polished surface. Extinction ratios up to 14 dB between orthogonal polarisations have been realised.
TL;DR: In this paper, an all-fibre Mach-Zehnder interferometer was used to detect the change in optical path length produced by the strain in the fibre.
Abstract: A sensitivity of less than 1 μg for a fibre optic accelerometer is demonstrated. The accelerometer measures the strain in the fibre when a mass is accelerated. An all-fibre Mach-Zehnder interferometer was used to detect the change in optical path length produced by the strain in the fibre.
TL;DR: In this article, a new refractive-index distribution for realising a single-polarization single-mode optical fiber is proposed, which features two pits, on either side of the core.
Abstract: 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%.
TL;DR: In this paper, the scattering process in single-mode optical fibres is considered in terms of wave optics rather than geometrical optics, which is inadequate in this case, and the result for the backscattering signal at the input end of the fibre is nearly the same as for multimode fibres.
Abstract: The scattering process in single-mode optical fibres is considered in terms of wave optics rather than geometrical optics, which is inadequate in this case. Surprisingly, however, the result for the backscattering signal at the input end of the fibre is nearly the same as for multimode fibres.
CNET1
TL;DR: In this article, 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.
Abstract: 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.
TL;DR: In this paper, an exact solution for the magnetic field intensity within a conducting cylinder in an oscillating external magnetic field parallel to the cylinder axis is presented, which implies that, in clinical hyperthermia, frequencies up to 13.56 MHz can be used without a major loss of depth penetration.
Abstract: An exact solution is presented for the magnetic field intensity within a conducting cylinder in an oscillating external magnetic field parallel to the cylinder axis. The numerical results given imply that, in clinical hyperthermia, frequencies up to 13.56 MHz can be used without a major loss of depth penetration.
TL;DR: In this paper, a combined method making use of the advantages of the stability-equation method and the Pade approximation method for finding stable reduced-order models is presented, and compared with the result in the current literature.
Abstract: A combined method making use of the advantages of the stability-equation method and the Pade approximation method for finding stable reduced-order models is presented. Comparisons with the result in the current literature are given.
TL;DR: In this paper, a correlation-based optical cable fault location technique using a 1.3 μm wavelength was proposed to detect a broken point 10 km distant from the source, which can be used for fault detection.
Abstract: The letter describes a correlation based optical cable fault location technique which, using a 1.3 μm wavelength, can detect a broken point 10 km distant from source.
TL;DR: In this article, three active RC synthetic floating inductance circuits are proposed which realize lossless f.i. and series and parallel RL impedance, respectively employing three and two second-generation current conveyors as active elements.
Abstract: Three new active RC synthetic floating inductance circuits are proposed which realise lossless f.i. and series and parallel RL impedance, respectively employing three and two second-generation current conveyors as active elements. The novel features of the new circuits are that (i) in contrast to available operational-amplifier circuits for f.i.s, the circuits presented here do not require component matching for the desired realisation; (ii) the new circuits employ a minimum possible number of passive elements (only two resistors and a capacitor); (ii) in all the new circuits, the inductance value is independently controllable through a single resistance.
TL;DR: In this paper, a single-mode operation of an AlGaAs double heterostructure semiconductor laser directly modulated at 500 Mbit/s data rate was realized by injection locking.
Abstract: Single-mode operation of an AlGaAs double heterostructure semiconductor laser directly modulated at 500 Mbit/s data rate was realised by injection locking. The power ratio of central injected mode to total spectrum power was 94%.
TL;DR: In this paper, a low-loss single-mode fiber pumped with a 1.3?m Q-switched Nd:y.a. laser was used to generate new waves at multiple wavelengths with total spectral range extended as wide as 660 cm.
Abstract: In a low-loss single-mode fibre pumped with a 1.3 ?m Q-switched Nd:y.a.g. laser, an injected weak (~ 1 mW) signal has been strongly amplified and mixed efficiently with the pump (~ 70 W) to generate new waves (?1 W) at multiple wavelengths with total spectral range extended as wide as 660 cm?1.
TL;DR: Deep levels in GaAs grown by molecular-beam epitaxy have been examined in this paper, where the dependence of both electron and hole trap densities on growth parameters such as growth temperature have been obtained.
Abstract: Deep levels in GaAs grown by molecular-beam epitaxy have been examined. Dependence of both electron and hole trap densities on growth parameters such as growth temperature have been obtained.
TL;DR: In this paper, the frequency modulated semiconductor laser signals are demodulated by optical heterodyne detection using an independently temperature stabilised laser local oscillator and a square law detector followed by electrical frequency discrimination circuitry.
Abstract: Frequency modulated semiconductor laser signals are demodulated by optical heterodyne detection using an independently temperature stabilised semiconductor laser local oscillator and a square law detector followed by electrical frequency discrimination circuitry. Beat frequency stability of the free-running semiconductor laser transmitter and local oscillator and characteristics of direct frequency modulation and optical heterodyne detection are delineated.
TL;DR: In this article, 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.
Abstract: 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.
TL;DR: In this article, the design of current conveyors using a minimum number of operational amplifiers was reported. But their performance was not compared with other realisations, and they used different configurations of the amplifiers.
Abstract: Some circuits for the design of current conveyors are reported. The new configurations use a minimum number of operational amplifiers. Experimental data on their performance is compared with other realisations.
TL;DR: In this paper, the experimental current/voltage characteristics for n+-n-n+ and n+p−n+n+ GaAs structures are described. And it is evident from the results that the electron transport is mainly ballistic in nature.
Abstract: Experimental current/voltage characteristics are described for n+-n-n+ and n+-p−-n+ GaAs structures. It is evident from the results that the electron transport is mainly ballistic in nature.
TL;DR: In this paper, the authors studied the visibility degradation of an AlGaAs double heterostructure laser with respect to visibility, and the maximum value of visibility measured by interference experiment with the injecting wave was 0.87.
Abstract: Injection phase locking of an AlGaAs double heterostructure laser was studied with respect to visibility. The maximum value of visibility measured by interference experiment with the injecting wave was 0.87. Causes of the visibility degradation were attributed to the light from a heat sink plane and to spurious modes other than the locked central mode.