Showing papers in "Electronics Letters in 1991"
TL;DR: In this article, a simple autocorrelation model for shadow fading in mobile radio channels is proposed, which is fitted to both large cells and microcells, and results show that the model fit is good for large to medium cells.
Abstract: A simple autocorrelation model for shadow fading in mobile radio channels is proposed. The model is fitted to both large cells and microcells. Results show that the model fit is good for large to m ...
1,557 citations
TL;DR: In this paper, a self-emitting CVD polycrystalline diamond film was observed to emit electrons with an intensity sufficient to form an image in the accelerating field of an emission microscope without external excitation.
Abstract: Thick (100 μm) chemical vapour deposited (CVD) polycrystalline diamond films have been observed to emit electrons with an intensity sufficient to form an image in the accelerating field of an emission microscope without external excitation (> 3 MV/m). The individual crystallites are of the order of 1–10 μm. The combined crystallite diameter and the electric field strength in these ‘self-emitting’ films are far below those typical for cold field emitters.
392 citations
TL;DR: In this paper, a new technique that incorporates synchronous shaping and retiming using a high speed optical modulator was proposed to overcome the Gordon-Haus limit, the accumulation of amplified spontaneous emission, and the effect of interaction forces between adjacent solitons.
Abstract: Soliton data transmission at 7.2–10 Gbit/s over one million kilometres has been successfully achieved by using a new technique that incorporates synchronous shaping and retiming using a high speed optical modulator. This technique enables the Gordon–Haus limit, the accumulation of amplified spontaneous emission, and the effect of interaction forces between adjacent solitons to be overcome. This technique is analogous to the synchronously pumped laser technique and can extend the soliton transmission distance almost infinitely.
345 citations
TL;DR: A new spread-spectrum code-acquisition technique for the navigation systems Navstar/GPS and Glonass is introduced that uses the FFT to compute the correlation function, thereby eliminating the time-consuming code phase shift process.
Abstract: A new spread-spectrum code-acquisition technique for the navigation systems Navstar/GPS and Glonass is introduced. This technique uses the FFT to compute the correlation function, thereby eliminating the time-consuming code phase shift process. Comparisons with existing systems show a theoretical reduction in acquisition time of about 2000 times.
334 citations
TL;DR: In this article, a nonlinear amplifying loop mirror was converted into a laser by feedback of the output to the input through a fiber-pigtailed optical isolator, and the pump powers were low enough that laser diodes could be used for pumping.
Abstract: A nonlinear amplifying loop mirror has been turned into a laser by feedback of the output to the input through a fibre-pigtailed optical isolator. After some optimisation, pulses as short as 314 fs were produced. The pump powers are low enough that laser diodes could be used for pumping.
320 citations
TL;DR: In this paper, an aperture shape that gives significantly improved coupling for an aperture coupled microstrip antenna is described, which consists of the usual rectangular slot, augmented with loading slots at each end.
Abstract: An aperture shape that gives significantly improved coupling for an aperture coupled microstrip antenna is described. This ‘dogbone’ aperture consists of the usual rectangular slot, augmented with loading slots at each end. Measured data show an increase of more than three for the resonant input impedance of an antenna using the dogbone-shaped aperture, as compared with the input impedance of the same antenna with a rectangular slot of the same overall length. The field distributions of both slots are also measured, and compared.
271 citations
TL;DR: In this paper, an all-optical feedback loop is demonstrated which effectively suppresses slow, signal-induced gain fluctuations in Er-doped fibre amplifers (EDFAs).
Abstract: An all-optical feedback loop is demonstrated which effectively suppresses slow, signal-induced gain fluctuations in Er-doped fibre amplifers (EDFAs). Gain control is achieved by operating the amplifier in a ring-laser configuration. The working principle is shown theoretically and experimentally by coupling a selected wavelength of the ASE at the output of the EDFA back to the input. Such a feedback loop, which can be fabricated out of all-fibre passive components, could be easily implemented in any system using EDFAs.
266 citations
TL;DR: In this paper, a polarisation-insensitive fiber optic Michelson interferometric sensor configuration is demonstrated based on the use of birefringence compensation in a retraced fibre path using Faraday rotator mirror elements.
Abstract: A polarisation-insensitive fibre optic Michelson interferometric sensor configuration is demonstrated. The approach is based on the use of birefringence compensation in a retraced fibre path using Faraday rotator mirror elements.<
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239 citations
TL;DR: The first integrated optical laser in LiNbO3, doped by an indiffusion of Er3+ prior to channel-guide fabrication by Ti diffusion is reported in this article.
Abstract: The first integrated optical laser in LiNbO3, doped by an indiffusion of Er3+ prior to channel-guide fabrication by Ti diffusion is reported. Pumped by a colour centre laser (λp = 1.477 μm), CW operation at λ = 1.532 μm (Δ~0.3 nm) with a threshold of ~8 mW absorbed power was achieved.
221 citations
TL;DR: The first demonstration of upconversion pumped lasing at green wavelengths in an Er3+-doped fluorozirconate fiber laser was reported in this paper, where 15 mW continuous wave emission at a wavelength of 546 nm was achieved for an absorbed pump power of 300 mW.
Abstract: The first demonstration of upconversion pumped lasing at green wavelengths in an Er3+-doped fluorozirconate fibre laser is reported. 15 mW continuous wave emission at a wavelength of 546 nm has been achieved for an absorbed pump power of 300 mW.
212 citations
TL;DR: In this paper, a continuous-wave, room temperature laser oscillation at 491 nm, 520 nm, 605 nm and 635 nm in a Pr3+-doped fluoro-zirconate fiber pumped simultaneously at 1.01 µm and 0.835 µm is reported.
Abstract: Continuous-wave, room temperature laser oscillation at 491 nm, 520 nm, 605 nm and 635 nm in a Pr3+-doped fluoro-zirconate fibre pumped simultaneously at 1.01 µm and 0.835µm is reported. An output power of 185mW has been measured for the 635 nm transition. The thresholds obtained suggest that laser diode-pumped operation of all four transitions should be possible in an optimised fibre.
TL;DR: In this article, the authors reported the generation of 320fs soliton pulses at 1560nm from an all-fibre, passively mode-locked erbium fiber.
Abstract: The generation of ultrashort 320fs soliton pulses at 1560nm from an all-fibre, passively mode-locked erbium fibre is reported. Repetition rates as high as 10GHz have been observed demonstrating the device's potential as a telecommunication soliton source.
TL;DR: In this article, a novel structure electroabsorption modulator/DFB laser integrated device is proposed and demonstrated, which consists of MQW structures with different quantum energy levels, which are automatically formed in the same MOCVD run by using a selective area growth technique.
Abstract: A novel structure electroabsorption modulator/DFB laser integrated device is proposed and demonstrated. Both functional devices consist of MQW structures with different quantum energy levels, which are automatically formed in the same MOCVD run by using a selective area growth technique. A fundamental modulation with a 12.6dB extinction ratio is demonstrated.
TL;DR: In this article, a new method for cloud attenuation calculation on an earth-satellite link is presented, which uses temperature and humidity profiles as input parameters, and has been applied to radiosonde measurements and to the gridded data of the numerical analyses of ECMWF.
Abstract: A new method for cloud attenuation calculation on an earth–satellite link is presented. The method uses temperature and humidity profiles as input parameters. The method has been applied to radiosonde measurements and to the gridded data of the numerical analyses of ECMWF.
TL;DR: In this paper, a self-starting, passively mode-locked erbium fiber laser is proposed based on the reflection properties of a nonlinear amplifying loop mirror and provides a stable source of picosecond pulses.
Abstract: A novel self-starting, passively mode-locked erbium fibre laser is reported The scheme is based on the reflection properties of a nonlinear amplifying loop mirror and provides a stable source of picosecond pulses
TL;DR: In this article, two fiber tapering systems are tested for correspondence with the results of a simple predictive model for taper shape, and a travelling gas burner system is found to imitate the model and should reproducibly realise any shape of taper, given an appropriate recipe from the model.
Abstract: Two fibre tapering systems are tested for correspondence with the results of a simple predictive model for taper shape. A travelling gas burner system is found to imitate the model and should reproducibly realise any shape of taper, given an appropriate recipe from the model.
TL;DR: In this article, a single-beam optical trapping of microscopic particles and biological cells was demonstrated by using higher-order mode Nd : YAG laser beams at 1.064 μm for the first known time.
Abstract: A single-beam optical trapping of microscopic particles and biological cells is demonstrated by using higher-order mode Nd : YAG laser beams at 1.064 μm for the first known time. A stronger trapping force by a TEM01* beam than that by a TEM00 beam was observed and 360° rotation of a trapped red blood cell with a TEM0n beam was achieved.
TL;DR: In this article, the realisation of singlemode rib waveguides in silicon-on-insulator (SOI) having a width and height of several micro-metres is reported.
Abstract: The realisation of singlemode rib waveguides in silicon-on-insulator (SOI) having a width and height of several micro-metres is reported. Measurements at a wavelength of 1.3 and 1.55 μm yield waveguide losses below 0.5 dB/cm and an excellent agreement of the near field intensity distribution with the one predicted by a BPM simulation.
TL;DR: In this article, a novel technique for the fabrication of domain reversed gratings in LiNbO3 by means of direct electron beam writing at room temperature without any static bias is reported.
Abstract: A novel technique for the fabrication of domain reversed gratings in LiNbO3 by means of direct electron beam writing at room temperature without any static bias is reported. The domain grating has been achieved not only at the – c surface of the crystal, but also for the entire region of the crystal. Such a structure should be useful for various nonlinear optic applications. A preliminary study on the second harmonic generation has also been demonstrated under the quasiphasematched condition with high efficiency.
TL;DR: In this article, a purely optical demultiplexing technique for high-speed time-division multiplexed data is proposed and demonstrated using optical fiber nonlinearity induced four-wave mixing with a data signal and a probe signal located at different wavelengths.
Abstract: A novel, purely optical technique for demultiplexing high-speed time-division multiplexed data is proposed and demonstrated. The technique uses optical fibre nonlinearity induced four-wave mixing with a data signal and a probe signal located at different wavelengths. Using only semiconductor laser light sources, 1:4 demultiplexing of 20 ps long, subpicojoule, 2/sup 15/-1 RZ pulses at a data rate of 16 Gbit/s with less than 1 dB penalty is demonstrated.
TL;DR: In this paper, a VLSI architecture suitable for 2D orthogonal wavelet tranforms is presented, which for the Daubechies wavelet implements the forward and inverse tranform without multipliers.
Abstract: The 2-D orthogonal wavelet tranform is proving to be a highly effective tool for image analysis. In particular, the four-coefficient Daubechies wavelet transform has excellent spatial and spectral locality, properties which make it very useful in image compression. A VLSI architecture suitable for 2D orthogonal wavelet tranforms is presented, which for the Daubechies wavelet implements the forward and inverse tranforms without multipliers. A sample implementation is described.
TL;DR: The algorithm called fast Golay correlation (FGC) performs the correlation of the input radar signal with the Golay sequence using only 2•log 2 (M) operations per input sample as opposed to M operations required by standard correlators.
Abstract: The highly regular structure of binary Golay complementary sequences of length 2 N makes possible a very simple correlator for these sequences. The algorithm called fast Golay correlation (FGC) performs the correlation of the input radar signal with the Golay sequence using only 2•log 2 (M) operations per input sample as opposed to M operations required by standard correlators. This algorithm is also valid for complex sequences of the same length. This fast correlator and the good autocorrelation properties of Golay sequences make them the ideal choice for high speed, long sequence pulse compression. Sequence agility on the pulse to pulse basis is also possible at the expense of some added complexity
TL;DR: In this paper, an unclad fiber was dipcoated with a thin layer of porous cladding within which a pH-sensitive dye was entrapped, and the performance of the pH sensor was reported and the potential of the technique for distributed and integrated optic sensing was discussed.
Abstract: The sol-gel process for low temperature fabrication of porous glass has been used to entrap chemically-sensitive dyes for optical sensor applications. Evanescent wave excitation was used to examine the behaviour of an unclad fibre which was dipcoated with a thin layer of porous cladding within which a pH-sensitive dye was entrapped. The performance of the pH sensor is reported and the potential of the technique for distributed and integrated optic sensing is discussed.<
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TL;DR: In this article, a diode detector is used to provide amplitude feedback to guide the adaption of baseband circuits that correct for carrier leak, differential gain and phase mismatch errors.
Abstract: A technique for the automatic correction of errors in RF quadrature modulators is described. The method uses a diode detector to provide amplitude feedback to guide the adaption of baseband circuits that correct for carrier leak, differential gain and phase mismatch errors.
TL;DR: In this article, a fiber reflection grating incorporated in the fiber pigtail is used to determine the wavelength of the packaged DFB, which can be determined by the appropriate choice of fiber grating coupled to the antireflection coated facet of a 1.55μm BH laser.
Abstract: A narrow linewidth, low chirp, wavelength selectable, packaged alternative to current DFB structures has been developed which employs a fibre reflection grating incorporated in the fibre pigtail. The wavelength of the packaged device can be determined by the appropriate choice of fibre grating coupled to the antireflection coated facet of a 1.55μm BH laser. Linewidths of less than 50 kHz, sidemode suppression of more than 30 dB and chirp when modulated at 1.2 Gbit/s of <0.5 MHz have been demonstrated.
TL;DR: In this paper, a novel circuit configuration for the realisation of a current-mode first-order all-pass filter using a single four-terminal floating nullor with a grounded capacitor is proposed.
Abstract: A novel circuit configuration for the realisation of a current-mode first-order allpass filter using a single four-terminal floating nullor (FTFN) with a grounded capacitor, which is suitable for integrated circuit implementation, is proposed.
TL;DR: In this article, passive alignment of semiconductor lasers and single-mode fibres has been achieved using a micromachined silicon subtrate, which offers the potential for low-cost optoelectronic device packaging and a means for dense hybrid integration of optical components required for multifibre, multichip systems.
Abstract: Passive alignment of semiconductor lasers and singlemode fibres has been achieved for the first time using a micromachined silicon subtrate. Mechanical alignment features fabricated on the substrate surface were used to align the active regions of an InGaAsP/InP laser array to four single-mode fibres held in V grooves. Optical coupling efficiencies have been achieved that are comparable to values obtained using the conventional technique of active fibre manipulation. The approach, called silicon waferboard, offers the potential for low-cost optoelectronic device packaging as well as a means for dense hybrid integration of optoelectronic, electronic and optical components required for multifibre, multichip systems.
TL;DR: In this paper, the energy transfer efficiency from Yb3+ to Er3+, even under high inversion, is comparable to that in multicomponent glass fibres, with small signal gain of ∼45dB.
Abstract: Efficient 154 μm emission under 1064 nm excitation of Er3+/Yb3+ codoped silica fibre is reported The energy transfer efficiency from Yb3+ to Er3+, ∼95%, even under high inversion, is comparable to that in multicomponent glass fibres The small signal gain of ∼45dB is measured and power amplifiers with 145 mW output power demonstrated
TL;DR: In this paper, the Er-doped silica guided-wave laser operating around 1.6 μm was realized using a low-scattering-loss planar lightwave circuit with an Erdoped Silica core which was fabricated by flame hydrolysis deposition and reactive ion etching techniques on an Si substrate.
Abstract: The Er-doped silica guided-wave laser operating around 1.6 μm was realised using a low-scattering-loss planar lightwave circuit with an Er-doped silica core which was fabricated by flame hydrolysis deposition and reactive ion etching techniques on an Si substrate. CW lasing was achieved successfully with an incident threshold power of 49 mW for pumping at 0.98 μm.
IBM1
TL;DR: In this article, the switching mechanism is based on the thermally induced variation of the refractive index of crystalline silicon, which has been demonstrated at λ = 1.3 μm.
Abstract: Mach-Zehnder waveguide interferometers have been fabricated in silicon and operation has been demonstrated at λ = 1.3 μm. The switching mechanism is based on the thermally induced variation of the refractive index of crystalline silicon. Modulation depths of 40% were obtained for switching powers of 30 mW and switching times of 50 μs.