Showing papers in "Electronics Letters in 1987"
TL;DR: In this paper, a 3m-long erbium-doped fiber was used for high gain amplification of up to 28 dB at a bit rate of 140 Mbit/s.
Abstract: High gain amplification of up to 28 dB has been observed in a 3m-long erbium-doped fibre. The amplifier has a spectral bandwidth of greater than 300GHz in the region of 1.536µm and a measured sensitivity of -42dBm at a bit rate of 140 Mbit/s.
901 citations
TL;DR: In this article, a solution-doping technique for the reproducible fabrication of low-loss optical fibres containing up to 4000 parts in 106 rare-earth ions is described.
Abstract: A solution-doping technique is reported for the reproducible fabrication of low-loss optical fibres containing up to 4000 parts in 106 of rare-earth ions. The method produces excellent dopant uniformity and is sufficiently versatile to allow codoping with different ions.
382 citations
TL;DR: In this article, the characteristics of a two-layer electromagnetically coupled rectangular patch antenna were investigated for s between 0.31λ0 and 0.37λ0, and the variations of pattern shape, 3 dB beamwidth and impedance bandwidth with spacing s between the two layers were studied.
Abstract: Experimental results on the characteristics of a two-layer electromagnetically coupled rectangular patch antenna are presented. The variations of pattern shape, 3 dB beamwidth and impedance bandwidth with spacing s between the two layers are studied for s between 0 and 0.37λ0. A relatively high-gain region is found for s between 0.31λ0 and 0.37λ0.
325 citations
TL;DR: In this article, a microstrip feedline on a substrate proximity-coupled to a rectangular microstrip patch on a covering superstrate is constructed, and a small open-circuit tuning stub is connected in shunt with the feed line.
Abstract: The letter presents experimental results for a proximity-coupled microstrip patch antenna capable of 13% bandwidth. The impedance match (VSWR ≤ 2), copolarised radiation patterns and crosspolarised radiation were measured over this bandwidth to confirm operation. The construction is quite simple, consisting of a microstrip feedline on a substrate proximity-coupled to a rectangular microstrip patch on a covering superstrate; a small open-circuit tuning stub is connected in shunt with the feed line.
301 citations
TL;DR: In this paper, three kinds of fiber Fabry-Perot (FFP) tunable filters are presented, each of which can cover a separate free spectral range interval as determined by its resonator length.
Abstract: We have made prototypes of three kinds of fibre Fabry-Perot (FFP) tunable filters, each of which can cover a separate free spectral range interval as determined by its resonator length. Free spectral ranges from hundreds of angstroms to tens of megahertz can be realised from the appropriate type. We have built FFPs with free spectral ranges of >1000 A, 25 GHz, 5 GHz and 2.5 GHz. Finesse up to 200 has been demonstrated. The devices are piezoelectrically tuned and are coupled to fibres in-line using standard rotary splices or ST connectors.
259 citations
TL;DR: In this paper, a two-probe feed was used to overcome the radiation pattern distortion, high crosspolarization and low efficiency due both to higher-order modes and surface-wave generation.
Abstract: In thick microstrip patches, probe inductance prevents matching of the patch impedance to the input connector. The probe inductance can be tuned out with a capacitive gap. To maintain simplified construction the gap is here etched on the patch surface. Bandwidths equal to or greater than that theoretically predicted are realised. Use of a single probe-compensated feed results in radiation pattern distortion, high crosspolarisation and low efficiency due both to higher-order modes and surface-wave generation. Two-probe feeding is used here to overcome these problems and to give a wide-band antenna with good radiation pattern control and high efficiency.
216 citations
TL;DR: In this paper, a printed circuit antenna element is coupled to a pair of microstriplines on another substrate via two orthogonal, rectangular apertures in a common ground plane.
Abstract: A new method for radiating dual or circular polarisation with a printed circuit antenna element is described. A square microstrip patch on one substrate is coupled to a pair of microstriplines on another substrate via two orthogonal, rectangular apertures in a common ground plane. Quadrature excitation of the system results in circularly polarised radiation.
209 citations
TL;DR: In this article, a new digital telephone system using a passive optical network is described, where downstream transmission is broadcast and optical time-division, multiple access (OTDMA) is used in the upstream path.
Abstract: A new digital telephone system is described using a passive optical network. Downstream transmission is broadcast and optical time-division, multiple-access (OTDMA) is used in the upstream path. The principle advantage of this approach is that exchange resources and fibres are shared between a large number of customers
204 citations
TL;DR: In this article, the effect of plasma excitation frequency on the deposition of amorphous hydrogenated silicon in a silane glow-discharge system is investigated, and a large increase in the deposition rate up to 21 A/s is observed in the range between 25 and 150 MHz.
Abstract: The effect of plasma excitation frequency on the deposition of amorphous hydrogenated silicon in a silane glow-discharge system is investigated. A large increase in the deposition rate up to 21 A/s is observed in the range between 25 and 150 MHz. Optical and electrical film parameters remain practically unchanged over this frequency range.
151 citations
TL;DR: The use of surface plasmon resonance measurements for the imaging of surfaces has been investigated in this paper, where images of dielectric patterns deposited on silver films are presented, with thickness sensitivity of about 3 A and a lateral resolution of about 25μm.
Abstract: The use of surface plasmon resonance measurements for the imaging of surfaces has been investigated. Images of dielectric patterns deposited on silver films are presented, with thickness sensitivity of about 3 A and a lateral resolution of about 25μm.
141 citations
NEC1
TL;DR: A 15 μm distributed Bragg reflector (DBR) laser with phase and Bragg wavelength control regions was newly developed over 720 GHz (58 nm) continuous frequency tuning with 2mW light output were achieved for the first time as mentioned in this paper.
Abstract: A 15 μm distributed Bragg reflector (DBR) laser with phase and Bragg wavelength control regions was newly developed Over 720 GHz (58 nm) continuous frequency tuning with 2mW light output were achieved for the first time
TL;DR: In this paper, a subcarrier multiplexed (SCM) optical communication system is described which transmits 60 frequency-modulated (FM) video channels over 18 km of single-mode fiber with a 56 dB weighted signal/noise ratio.
Abstract: A subcarrier multiplexed (SCM) optical communication system is described which transmits 60 frequency-modulated (FM) video channels over 18 km of single-mode fibre with a 56 dB weighted signal/noise ratio.
TL;DR: In this paper, a method of obtaining the exact solution to the nonlinear equations for eliminating several lower-order harmonics in the output voltage of a PWM inverter is illustrated.
Abstract: A method of obtaining the exact solution to the nonlinear equations for eliminating several lower-order harmonics in the output voltage of a PWM inverter is illustrated. This procedure permits the widespread use of this technique in the entire frequency range in power control.
TL;DR: An external electro-optic technique for characterising high-speed electrical signals in two-dimensional electrode structures of devices and integrated circuits fabricated on any substrate material has been described in this article.
Abstract: We describe an external electro-optic technique for characterising high-speed electrical signals in two-dimensional electrode structures of devices and integrated circuits fabricated on any substrate material A temporal resolution of less than 300 fs, corresponding to a bandwidth in excess of 1 THz has been achieved
TL;DR: In this article, a dry etching technique which is capable of producing low-damage, high-aspect-ratio structures on a nanometric scale in GaAs is described.
Abstract: A dry etching technique which is capable of producing lowdamage, high-aspect-ratio structures on a nanometric scale in GaAs is described. The reactive ion etching employs a mixture of methane and hydrogen; details of the optimum conditions are given.
TL;DR: In this paper, the authors present transmission measurements in a multi-wavelength optical network, using 18 channels spaced 2 nm around 1.55 μm, modulated at 1.5G bit/s and transmitted through 57.8 km of single-mode optical fiber.
Abstract: The letter presents transmission measurements in a multi-wavelength optical network, using 18 channels spaced 2 nm around 1.55 μm. Each channel was modulated at 1.5G bit/s and transmitted through 57.8 km of single-mode optical fibre. Experimental results demonstrate a bandwidth-distance product of l.56 Tbit s−1 km and a point-to-multipoint figure of merit of 21.5 Tbit s−1 km node.
TL;DR: In this article, a four-port optical tap that extracts efficiently from a fiber in which light containing several discrete wavelength bands is propagating only that light within one such band was proposed.
Abstract: A novel design is proposed for a four-port optical tap that extracts efficiently from a fibre in which light containing several discrete wavelength bands is propagating only that light within one such band. The same device can be used simultaneously to combine light of the same wavelength as the extracted light with the other, unselected, wavelength bands.
TL;DR: In this paper, the authors measured the effective length and wavelength selectivity of a second order susceptibility grating written into a fiber and achieved phase-matching by self-writing of defect centers in the fiber.
Abstract: Measurements of the effective length and wavelength selectivity of a second order susceptibility grating written into a fibre are reported. A weak non-phase matched second harmonic signal at 532nm is generated by the allowed quadrupole polarisation. This signal initiates the self-writing of an axially periodic pattern of defect centres in the fibre which lead to the growth of a chi (2) grating. Phase-matching is achieved automatically because the enhanced chi (2) is written periodically into the fibre at spatial locations where the second harmonic signal is the highest and is in phase with the pump. One particular chi (2) grating extends over 12cm of fibre and has a bandwidth of 0.24nm
TL;DR: In this article, a neural network implementation consisting of switches, capacitors and inverters is proposed, and a number of potentially attractive features of the implementation are pointed out, such as the ability of the network to learn from the inputs and outputs of the switches and capacitors.
Abstract: A neural network implementation is proposed, consisting of switches, capacitors and inverters. A number of potentially attractive features of the implementation are pointed out.
TL;DR: In this paper, the conversion of infra-red to visible light has been studied in a series of fluoride glasses doped with YbF3 and ErF3, and the frequency up-conversion efficiency is four orders of magnitude greater than that observed in doped oxide glasses, and compares very favourably with results obtained for Yb3+/Er3+-containing crystals.
Abstract: The conversion of infra-red to visible light has been studied in a series of fluoride glasses doped with YbF3 and ErF3. The frequency up-conversion efficiency of these bulk materials is four orders of magnitude greater than that observed in doped oxide glasses, and compares very favourably with results obtained for Yb3+/Er3+-containing crystals.
TL;DR: Several techniques are proposed for making possible analogue electronic neural networks with variable synapse strengths that take advantage of the variability of transistor conductance or transconductance with bias, and use capacitors for temporary storage of the required control voltage.
Abstract: Several techniques are proposed for making possible analogue electronic neural networks with variable synapse strengths. The techniques take advantage of the variability of transistor conductance or transconductance with bias, and use capacitors for temporary storage of the required control voltage.
TL;DR: Theoretical and experimental results as mentioned in this paper 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.
Abstract: 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.
TL;DR: In this paper, a simple formula is given for the maximum spot size achievable by downtapering a single-mode fiber, regardless of core profile when the fundamental mode field is approximately Gaussian.
Abstract: A simple formula is given for the maximum spot size achievable by downtapering a single-mode fibre, regardless of core profile When the fundamental-mode field is approximately Gaussian, the maximum taper angle associated with minimal loss of spot-size power on a finite-length taper is the classical diffraction angle for a beam passing through a circular aperture
TL;DR: In this article, the third-order susceptibility was evaluated to be x(3) = 7.8 × 10−12esuat 1.85μm wavelength on poly(p-phenylenevinylene) thin films.
Abstract: Third-harmonic generation (THG) measurements have been made on poly(p-phenylenevinylene) thin films. The third-order susceptibility was evaluated to be x(3)= 7.8 × 10−12esuat 1.85μm wavelength.
TL;DR: This work provides a ‘vector switching’ algorithm that reduces the expected signal distortion by suitably assigning code words to the codevectors in a given code-book, and generalises this to VQ.
Abstract: Gray-coding of signal amplitudes can protect PCM transmission of analogue signals from the effects of channel bit errors. We generalise this to VQ, and provide a ‘vector switching’ algorithm that reduces the expected signal distortion by suitably assigning code words to the codevectors in a given code-book.
TL;DR: In this article, a circular buried microcavity 7 μm long and 6 μm in diameter has been realized, with Ith = 6mA, ηd = 9% and peak power ≥ 1 mW at 20.5°C at single mode.
Abstract: A circular buried microcavity 7 μm long and 6 μm in diameter has been realised. We obtained Ith = 6mA, ηd = 9% and peak power ≥1 mW at 20.5°C at single mode. The first CW operation of a GaAlAs/GaAs surface-emitting laser with Ith = 4.5 mA at 77 K was also realised.
TL;DR: In this article, an ultrafast time-domain optical multi/demultiplexer utilizing the optical Kerr effect in two birefringent fibres concatenated with each fast axis crossed is proposed.
Abstract: An ultrafast time-domain optical multi/demultiplexer utilising the optical Kerr effect in two birefringent fibres concatenated with each fast axis crossed is proposed. Stable demultiplexing of an ultrashort 30 ps optical pulse train at 1.97 GHz from a gain-switched DFB LD has been successfully demonstrated using CW mode-locked Nd:YAG laser control pulses.
TL;DR: In this article, a tunable optical transmission filter for 1.5?n with a bandwidth of 12 A and a tuning range of at least 80 A was proposed based on wavelength-dependent polarisation conversion in a birefringent waveguide.
Abstract: We report a tunable optical transmission filter for 1.5?n with a bandwidth of 12 A and a tuning range of at least 80 A. The filter is based on wavelength-dependent polarisation conversion in a birefringent waveguide and employs a periodic electrode structure with interleaved birefringence tuning electrodes.
TL;DR: An InGaAs PIN photodiode was vertically integrated with an inverted optical rib waveguide in this article, achieving a responsivity of 0.81 A/W at 1.3?m wave-length.
Abstract: An InGaAs PIN photodiode was vertically integrated with an inverted optical rib waveguide in InGaAsP. Guided light was transferred to and absorbed by the photodiode at a rate of 0.07dB/?m. For detectors with sufficient length (>300?m) a responsivity of 0.81 A/W was achieved at 1.3 ?m wave-length.
TL;DR: In this article, an experimental study of intermodulation distortion in high-speed, long-wavelength GaInAsP lasers modulated up to 8 GHz was presented. And the authors used a simple theory to predict accurately the measured signal/noise ratio for each channel of a multichannel subcarrier system.
Abstract: We present an experimental study of intermodulation distortion (IMD) in high-speed, long-wavelength GaInAsP lasers modulated up to 8 GHz. It is found that three-tone distortion products are the dominant contribution to IMD interference when the number of subcarriers is large. These distortion data are used with a simple theory to predict accurately the measured signal/noise ratio for each channel of a multichannel subcarrier system.