IEE Proceedings - Optoelectronics
Volume 141, Issue 1, February 1994
Volumes & issues:
Volume 141, Issue 1
February 1994
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- Author(s): A. Yu and A.S. Siddiqui
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 1 –7
- DOI: 10.1049/ip-opt:19949806
- Type: Article
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We propose, and present a theoretical and experimental investigation of optical modulators using fibreoptic Sagnac interferometers. Several possible modulator configurations have been investigated and compared. An optical modulator using the ceramic material PLZT as the electrooptic modulating element has been experimentally demonstrated to show the feasibility of this new type of modulator structure. Preliminary experimental results show that the optical modulators using fibre Sagnac interferometer have a number of useful features such as input polarisation independence, readily adjustable phase bias, and suitability for forming fibre-to-fibre devices. - Author(s): A. Mecozzi ; A. Sapia ; P. Spano ; H. Burkhard ; S. Hansmann ; H. Hillmer
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 8 –12
- DOI: 10.1049/ip-opt:19949693
- Type: Article
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Distributed-feedback lambda /4-shifted laser diodes with index coupling factor kappa as high as 300 cm-1 have been tested. The linewidths have been compared with the results of two computer models of the device including nonlinear effects. The fundamental role of local intensity-dependent effects, which take place inside the cavity, is pointed out. It explains the absence of any saturation of the curve of the linewidth against inverse power that is usually expected in this kind of device at high injection levels. - Author(s): V. Jordan
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 13 –15
- DOI: 10.1049/ip-opt:19949912
- Type: Article
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The gain-measurement methods of Hakki-Paoli and Cassidy are investigated theoretically with respect to accuracy of gain evaluation and sensitivity to noise. The Cassidy method proves to be less sensitive to noise than the Hakki-Paoli method if an additional averaging procedure is introduced. The results presented permit easy establishment of the required performance of an appropriate measurement system. - Author(s): A. Hardy and M. Ben-Artzi
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 16 –20
- DOI: 10.1049/ip-opt:19949691
- Type: Article
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The problem of expanding a field over the set of waveguide modes is well known. Nevertheless, one may find small differences in the way this concept is used. Some employ a superposition of waveguide modes that include all field components, and a mode is considered as a single entity which propagates undisturbed along the structure. Others prefer to expand only the transverse-field components, whereas the longitudinal ones are derived from Maxwell's equations. It is shown that the latter is correct, at least for the important class of 2-dimensional structures. The two approaches coincide, however, if the structure is the waveguide for which the set of modes was calculated. The formal mathematical proof is restricted to a nonlossy medium. It is shown that the modes with real propagation coefficients squared suffice to construct a complete set. Depending on the boundary conditions in the longitudinal z direction, some or many of these modes may or may not be needed. - Author(s): L. Zhai ; A.J. Lowery ; Z. Ahmed
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 21 –26
- DOI: 10.1049/ip-opt:19949656
- Type: Article
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A diffraction grating model is developed for use with the transmission-line laser model to enable accurate simulation of grating-controlled mode-locked semiconductor lasers. The trade-off between accuracy and computational effort is examined. Asymmetrical detuning characteristics are investigated using the grating model. The pulsewidth and locking bandwidth are shown to depend on the bandwidth of the optical system, which is determined by the grating. - Author(s): P. Chakrabarti ; A. Chandra ; V. Gupta ; H.S. Shah ; Y. RaviKumar
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 27 –32
- DOI: 10.1049/ip-opt:19949692
- Type: Article
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The paper introduces an InGaAs/InP:Fe hetero-MIS structure which can be used as an optically controlled capacitor. A numerical model of the device has been developed to investigate the effect of illumination on the characteristics of the device. To generalise the model, the semiconductor has been assumed to be nonuniformly doped. The model takes into account the effects of the surface states and change in time constant of the minority carriers (electrons in this case) due to illumination. It has been found that the capacitance of the proposed structure can be precisely controlled by the incident optical power. The capacitor is expected to find useful applications in solid-state imaging and optical tuning. The model developed here can be used as a basic tool for analysing similar hetero-MIS structures with arbitrary doping profiles. - Author(s): D.S. George and M.W. McCall
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 33 –37
- DOI: 10.1049/ip-opt:19949797
- Type: Article
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Synchronous current modulation is investigated theoretically and experimentally as a method for enhancing or suppressing nearly degenerate four-wave mixing in a distributed feedback semiconductor laser amplifier. For modulation depths of 3% an enhancement of 200-300% in phase conjugate signal is observed. Expressions for the current modulation depth required to compensate the optical beat modulation are derived in the saturated and unsaturated case. Also, to enable experimental verification, the average intracavity intensity of the DFB amplifier for given input intensity is calculated. In the unsaturated case the square of the compensating modulation depth is seen to vary linearly with the product of intracavity intensities in accordance with theory. - Author(s): I. Bar-David
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 38 –42
- DOI: 10.1049/ip-opt:19949725
- Type: Article
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The phase-diversity mixing concept, originally applied in communication receivers to local-oscillator-aided reception, is here applied to the direct (i.e. local-oscillatorless) differential detection (D3) of phase-shift-keyed (PSK) transmissions. The received signal and its delay replica are first compared by means of a quadrature mixer, directly at the receiver front end, at the optical or microwave signal stage. The baseband phase-diversity signals thus obtained are linearly transformed in a baseband phase equaliser, and thus cancel out undesired, detrimental phase shifts which invariably occur in the wave-generating and wave-conveying components. The resulting D3PSK receiver is robust under variations in carrier frequency and in differential delay. Its development establishes coherent modulation methods, such as PSK and narrowband FSK, as viable alternatives to on/off keying, which at present is exclusively used in direct detection systems. - Author(s): S.J. Hewlett ; J.D. Love ; T. Tjugiarto
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 43 –48
- DOI: 10.1049/ip-opt:19949723
- Type: Article
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Polarisation-dependent coupling in a twin-elliptical-core optical fibre, whose cores possess both an arbitrary core eccentricity and orientation, is investigated. Exact numerical results are presented that determine the degree of form birefringence and permit the accuracy of standard approximation techniques to be evaluated. A comparison of the theoretical x- and y-polarisation coupling coefficients with experimental data suggests that stress-induced birefringence is dominant in practice. - Author(s): J. Arnaud
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 49 –52
- DOI: 10.1049/ip-opt:19949847
- Type: Article
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A simple expression for the linewidth of vertical cavity, periodic gain, laser diodes is reported. Quantum wells, spaced half a wavelength apart are assumed to be driven by time-independent electrical currents Jk, and to possess distinct phase amplitude coupling factors alphak. The usual linewidth formula is found to be applicable if the photon lifetime is defined as the round trip time divided by a factor of 6, and the averaging of the alphak is made with Jk as a weighting factor. Furthermore, half the spatial variance of alpha must be subtracted. The expression involves cross terms of the form alphai alphaj, i not=j. - Author(s): M.-S. Kao and T.-C. Lin
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 53 –61
- DOI: 10.1049/ip-opt:19949852
- Type: Article
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The implementation of a dense wavelength-division multiplexing (WDM) based wide-area network inevitably involves a large number of semiconductor lasers requiring particular temperature and driving current control. The concept of a novel multiwavelength network that uses only one laser source to generate all the carriers needed for the entire network is investigated. The central idea is to use a stable reference laser to generate two sets of optical carriers as the 'carrier supplies' for all network nodes: one set for signal transmission and the other for signal reception. A promising feature of the proposed network is the wavelength registration, that is, all carrier wavelengths are unambiguously identified. This special feature is of importance for a standard wide-area multiwavelength network. Optical phase modulation is extensively employed in the carrier generation as well as in information delivery. A 40-wavelength network is considered with each wavelength carrying 20 phase-modulated microwave subcarriers, a total throughput of 160 Gbit/s per single-mode fibre is estimated. - Author(s): T. Gryba and J.E. Lefebvre
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 62 –64
- DOI: 10.1049/ip-opt:19949913
- Type: Article
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A systematic study is presented of a multiple-quantum-well (MQW) acousto-optic modulator. The device utilises the electro-absorptive effects in quantum wells and the electric field induced by surface acoustic waves (SAW). The propagation of SAW in multilayered piezoelectric structures is studied and the electric field is calculated. The optical absorption coefficient in a MQW is calculated as a function of the applied electric field and the MQW parameters. A systematic approach for optimising the performance of a MQW acousto-optic modulator is presented. - Author(s): R. Hui ; I. Maio ; I. Montrosset
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 65 –68
- DOI: 10.1049/ip-opt:19949846
- Type: Article
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The all-electric automatic gain control of a travelling wave semiconductor laser amplifier through the error signal detected from its junction voltage is analysed. Three different control schemes are compared. The ability to suppress the optical gain variation caused by the polarisation fluctuation is particularly addressed. - Author(s): K.D. Leaver and G. Pagiatakis
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 69 –74
- DOI: 10.1049/ip-opt:19949848
- Type: Article
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A fibre directional coupler is described that comprises one fibre with a circular core coupled to one with a suitable rectangular core, which makes it possible in principle to couple 100% of the output of a semiconductor laser or laser amplifier into a single-mode communications fibre, and vice versa. The manufacture of such a coupler depends critically on the control of dimensions, because of the differing dispersion characteristics of the two fibres. This coupler was modelled using a finite element program in a preliminary attempt to study dimensional tolerances, with a view to optimising its design. Calculations are presented of the beatlength as a function of the sizes and the refractive indices of the two cores comprising the coupler, together with estimates of the dimensional tolerances, giving coupling losses under 1 dB. - Author(s): G.J. Sonek and E.R. Ranalli
- Source: IEE Proceedings - Optoelectronics, Volume 141, Issue 1, p. 75 –80
- DOI: 10.1049/ip-opt:19949849
- Type: Article
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The design and analysis of a guided-wave optical reflection filter, based on the use of a multiple quantum well polarisation convertor in an intracavity geometry, are reported. It is shown that quantum well dispersion and excitonic absorption in GaAs/AlGaAs quantum well structures can be used to produce filter linewidths and peak reflectances of <1 nm and approximately 95%, respectively, in the centre wavelength band of 865-885 nm. The use of dispersion engineering to tailor the filter response, via the quantum well parameters, is also described. Such optical filters should find widespread application as wavelength-selective components in fibreoptic network and communication systems.
Optical modulators using fibreoptic Sagnac interferometers
Nonlinearities in high-index-coupled lambda /4-shifted distributed-feedback semiconductor lasers
Gain measurement of semiconductor laser diodes: requirements for the wavelength resolution and sensitivity to noise
Expansion of an arbitrary field in terms of waveguide modes
Diffraction grating model for transmission-line laser model of actively mode-locked semiconductor lasers
Optically controlled characteristics of an ion-implanted hetero-MIS capacitor
Control of nearly degenerate four-wave mixing in a distributed feedback semiconductor laser amplifier via coherent electrical modulation
Direct differential detection of phase-shift-keyed signals: a local-oscillatorless DPSK receiver
Polarisation-dependent coupling in twin-core fibres with arbitrary elliptical cores
Linewidth of gain-coupled distributed feedback lasers
Conceptual survey of phase modulation based wavelength registered networks
Optimisation of MQW structures for acousto-optic absorption modulators
Analysis of the all-electrical automatic gain control of travelling-wave semiconductor laser amplifiers
Fabrication tolerances in fibre directional couplers designed to maximise coupling between fibres and diode lasers
Optical reflection filters based on intracavity quantum well polarisation convertors
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