IEE Proceedings - Circuits, Devices and Systems
Volume 150, Issue 6, December 2003
Volumes & issues:
Volume 150, Issue 6
December 2003
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- Author(s): Arnab Bhattacharya
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 465 –466
- DOI: 10.1049/ip-cds:20031183
- Type: Article
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- Author(s): A. Jhunjhunwala
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 467 –472
- DOI: 10.1049/ip-cds:20031143
- Type: Article
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Fibre plays a major role in backbone networks, not only making it capable of carrying large amounts of traffic but also making it cost-effective. However, the decrease in backbone cost has so far been nullified by an increase in the cost of local loops. Fibre access networks in developing countries like India are set to play a major role in expanding the teledensity. In dense urban areas of India, fibre access is not only the most cost-effective access technology, but is also contributing to building a multiservice network integrating telephony, TV and video-on-demand services. - Author(s): S. Ramachandran
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 473 –479
- DOI: 10.1049/ip-cds:20030875
- Type: Article
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In-fibre devices enable a vast array of critical photonic functions ranging from signal conditioning (amplification, dispersion control) to network management (add/drop multiplexers, optical monitoring). These devices have become the mainstays of fibre-optic communication systems because they provide the advantages of low loss, polarisation insensitivity, high reliability, and compatibility with the transmission line. The majority of fibre devices reported to date are obtained by doping, designing or writing gratings in the core of a single mode fibre. Thus, these devices use the fibre only as a platform for propagating light – the device effect itself is due to some extraneously introduced material or structure (dopants for amplification, gratings for phase matching etc.). There exists another, relatively less explored degree of freedom afforded by fibres: the ability to co-propagate more than one mode. Each mode may have a uniquely defined modal dispersion and propagation characteristic. The author describes the variety of fibre devices enabled by few-mode fibres, i.e. fibres that typically support two to four modes with suitably tailored dispersive properties. It is shown that the unique dispersive properties of various modes in conjunction with the ability to couple between them with gratings lead to devices that offer novel solutions for dispersion compensation, spectral shaping and polarisation control, to name a few. - Author(s): S.K. Bhadra ; R. Sen ; M. Pal ; M.C. Paul ; M.K. Naskar ; S. Chatterjee ; M. Chatterjee ; K. Dasgupta
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 480 –485
- DOI: 10.1049/ip-cds:20031032
- Type: Article
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Rare-earth (Er, Yb, Nd etc.) doped alumino-germano-silicate preforms and fibres with extensive variation in rare-earth (RE) concentration, composition, and proportion of codopants as well as waveguide parameters were fabricated by the modified chemical vapour deposition (MCVD) process in combination with the solution-doping and sol–gel methods. The fibres were characterised for evaluation of the optical properties including refractive index profile, numerical aperture, spectral attenuation, cut-off wavelength, concentration and distribution of the RE, Giles parameters and also the optical gain. The fabricated fibres had Er ion concentrations varying between 100 and 1000 ppm and numerical apertures in the range 0.17–0.24. Some of the fibres are suitable for use in C-band optical amplifiers. - Author(s): K.S. Abedin and F. Kubota
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 486 –489
- DOI: 10.1049/ip-cds:20030906
- Type: Article
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A technique is presented for accurately measuring the dispersion in single-mode fibres about a kilometre in length. It uses a polarisation interferometer and is simpler and less expensive than techniques currently being used. The interferometer incorporates a phase modulator and a test fibre. The dispersion is determined from the interference fringe seen when a sweep RF signal is applied to the modulator. The equipment is less bulky than that currently used for testing, so it can easily be carried into the field. Chromatic dispersion was measured with ps resolution in a 1 km-long single-mode fibre at wavelengths from 1.50–1.58 μm. - Author(s): S. Bhandare ; D. Sandel ; R. Noé ; R. Ricken ; H. Suche ; W. Sohler
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 490 –494
- DOI: 10.1049/ip-cds:20030762
- Type: Article
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A LiNbO3-based integrated optical network analyser for polarisation-resolved longitudinal structure characterisation of optical fibre Bragg gratings is reported. The frequency-dependent complete reflectance Jones matrix is measured by interferometry and transformed into the time-domain impulse response. From the impulse response matrix the vectorial grating structure is determined by inverse scattering. Local dichroic reflectivity and birefringence were derived from this data. Knowledge of the vectorial nature of refractive index modulation depth and phase should allow an improvement of the ultraviolet (UV) illumination process and an effective correction of phase mask errors by longitudinally selective UV light post-processing, in order to fabricate chirped and/or apodised gratings which require the highest fabrication accuracy. - Author(s): I. Abe ; I. Abe ; H.J. Kalinowski ; R. Nogueira ; J.L. Pinto ; O. Frazão
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 495 –500
- DOI: 10.1049/ip-cds:20031068
- Type: Article
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Bragg gratings written in high-birefringence fibre optics are a key element in the simultaneous measurement of transversal strain components and temperature, and they have several applications as single polarisation optical filters for wavelength division multiplexing (WDM) applications. Precise determination of grating characteristics is needed to aid device design, particularly taking into account the polarisation of the illuminating light. The authors report results concerning the production and characterisation of Bragg gratings in high birefringence fibre. Birefringence is measured by the wavelength dependence of the beat length, and from the Bragg grating reflection bands, for three common high birefringence fibres. Characterisation of the gratings when subjected to transversal strain and temperature is described, as well as results of the use of the grating to measure, simultaneously, those two parameters. - Author(s): H. Halbritter ; M. Aziz ; F. Riemenschneider ; P. Meissner ; M. Strassner ; A. Tarraf ; O.P. Daga
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 501 –505
- DOI: 10.1049/ip-cds:20030896
- Type: Article
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Wavelength division multiplexing has become a leading technology for long-haul transmission systems which operate at 1550 nm wavelength. The recent slump in the fibre optics industry has put a strong focus on the development of new flexible and tunable components, as well as cost effectiveness and reliability. Two-chip micromachined devices are very promising candidates to fulfil these demands. A tunable optical filter structure is discussed, which uses a simple bulk-micromachining process based on low-cost dielectric Bragg mirrors. The tuning is achieved by current-induced thermal heating of the membrane suspensions. This concept combines the advantages of low-cost dielectric mirror processing and the simple actuation principle by current flow to create a best-of-breed two-chip solution. The alignment process of the two-chip cavity has been simplified to the point where a simple place-and-fix strategy can be applied. Based on this concept, a tunable two-chip resonant-cavity light-emitting diode (RC-LED) is presented, which utilises the same bulk-micromachined chip. This validates that these micromachined tunable membranes can serve as basic building blocks for a wide variety of tunable components for wavelength division multiplexing systems, such as optical filters, receivers and vertical-cavity surface-emitting lasers (VCSELs). - Author(s): L. Potì ; M. Luise ; G. Prati
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 506 –511
- DOI: 10.1049/ip-cds:20031001
- Type: Article
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An overview of the most promising optical clock recovery techniques for all-optical ultrafast communication is presented. A step towards a system view for the various techniques is taken, transferring the clock recovery concepts available from the electronic domain into the optical domain, and leading to block diagram interpretation for both open-loop and closed-loop systems. This is essential for future system analyses that will permit design and comparison of different techniques using established analytical tools. - Author(s): P. Ghelfi ; A. Bogoni ; L. Potì
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 512 –515
- DOI: 10.1049/ip-cds:20030999
- Type: Article
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p.
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Noise reduction techniques, such as all-optical 3R regeneration, can be realised using ultrafast saturable absorbers, both for the clock recovery block and for the reshaping block. Electroabsorption modulators (EAM) can be used as saturable absorbers when they are traversed by a strong pump optical pulse, which can reduce the absorption experienced by a second probe signal that propagates along the device together with the pump: this feature is called cross-absorption modulation (XAM). The authors present a novel numerical model to evaluate the dynamic behaviour of a quantum well EAM absorption, that can be applied in all-optical signal processing schemes for ultrafast transmission systems. The effects of both electric field screening and exciton saturation are taken into account. Numerical results agree with the experimental device behaviour reported in the literature. - Author(s): P. Manohar ; P. Manohar ; A. Padmanath ; S. Singh ; D. Manjunath
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 516 –520
- DOI: 10.1049/ip-cds:20031142
- Type: Article
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A wavelength routed optical network is considered for which the traffic matrix and possibly the physical topology are different during different periods of a time horizon. The optimal virtual topology for each of the periods will be different. Rather than using the best topology in every period and incurring a possibly significant reconfiguration cost, it is necessary to consider the optimum sequence of virtual topologies that will minimise the sum of the operating and reconfiguration costs over the entire horizon. The presence of short-term cycles in the traffic pattern and the possible evolution of resources and demand in the network motivates this work. The approach adopted is to find a ranked set of virtual topologies for each period and then define a shortest path problem to obtain the optimum sequence. Examples on a 10 node section of the NSFNET topology are presented. - Author(s): R. Fehse ; I. Marko ; A.R. Adams
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 521 –528
- DOI: 10.1049/ip-cds:20030959
- Type: Article
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A compact review is given of the development of the device performance of GaAs-based long wavelength diode lasers with emission wavelengths from 1.3 to 1.55 μm. The main focus is on GaInNAs quantum wells and InAs quantum dot lasers. However, the Ga(In)AsSb material system is also briefly considered. The latest results of the present authors are discussed in relation to the trends observed in the review. These suggest that Auger recombination is an important intrinsic recombination mechanism in both 1.3 μm GaInNAs-based quantum well and InAs-based quantum dot lasers. - Author(s): D.N. Talwar
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 529 –536
- DOI: 10.1049/ip-cds:20030915
- Type: Article
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A comprehensive analysis of the Fourier transform infrared (FTIR) absorption and Raman scattering data on impurity modes is reported for the technologically important dilute ternary GaAs1−xNx, and GaP1−xNx (x<0.03) alloys grown on GaAs and GaP, respectively, by metal organic chemical vapour deposition (MOCVD) and solid source molecular beam epitaxy (MBE). For low nitrogen concentrations in GaAs1−xNx [GaP1−xNx] (i.e. x<0.015), most of the N atoms occupy the As [P] sublattice NAs [NP]. They prefer, however, to move out of their substitutional sites to more energetically favourable locations at higher x values. To comprehend the large width of the localised vibrational mode (LVM) in GaAs1−xNx near 470 cm−1, the possibilities of Ga isotopes (69Ga and 71Ga) and/or intrinsic defects participating with NAs in different configurations were studied. Theoretical results for the N-local modes and its isotopic shifts are found in good agreement with the FTIR data. Although, the presence of isolated N-interstitials. (Nint) in GaAs1−xNx is quite unlikely at higher compositions (0.03>x>0.015), the formations of nonradiative complex microstructures involving N and/or intrinsic defects are energetically favourable. The impurity modes for such complex centres were predicted and the possibility of observing them by optical spectroscopy was evaluated. - Author(s): D. Masanotti ; F. Causa ; J. Sarma
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 537 –541
- DOI: 10.1049/ip-cds:20030897
- Type: Article
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Optical sources that combine high power with high brightness are in great demand for various applications. Although sophisticated device designs have been demonstrated to have such desirable characteristics, to contain the device costs tapered geometry devices seem to provide attractive alternatives. Further, particularly for high-power operation, the bow-tie configuration is effective for further reducing the risk of catastrophic optical damage and for obtaining a good quality output beam. The authors present the detailed analysis that has been necessary to optimise both the material layer structure and the tapered laser geometry to achieve simultaneously high power and high brightness. Following the design guidelines, several 980 nm parabolic bow-tie lasers have been fabricated and characterised in-house, obtaining output powers in excess of 700 mW per facet in a diffraction-limited (2.7°) beam measured without the use of external lenses. - Author(s): T.C. Woo ; J. Sarma ; F. Causa
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 542 –547
- DOI: 10.1049/ip-cds:20031070
- Type: Article
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A quasi-analytic formulation based on Laguerre–Gauss functions (LG-Fs) that appears to be suitable to analyse vertical-cavity surface-emitting lasers (VCSELs) is described. The paper focuses on demonstrating the attractive feature of LG-Fs in solving for optical field propagation in both diffracting type and guided-wave type configurations, which is particularly advantageous for modelling present-day VCSELs. The paper also outlines the LG-F expansion formalism to solve for both the optical field and the carrier density distribution to achieve a self-consistent VCSEL model. - Author(s): A. Bogoni ; A. Bizzi ; L. Potì ; P. Ghelfi
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 548 –551
- DOI: 10.1049/ip-cds:20031126
- Type: Article
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In ultrafast all-optical signal processing schemes based on nonlinear effects in SOAs, the impact of the device spontaneous emission noise is not negligible. Therefore a numerical extended model is developed in order to predict SOA noise behaviour. The proposed tool takes into account all the gain recovery dynamics, the current-induced gain saturation, and the gain spectrum dependence on the injected current. The noise spectrum at the output of the device is investigated as a function of the injected current and of the input power, and the numerical results are experimentally validated. The importance of the ASE introduction in the numerical analysis of the SOA-based schemes for ultrafast all-optical processing is demonstrated studying two particular applications. In particular, the effects of high detuning FWM and of XGM are analysed in the presence and absence of ASE noise. - Author(s): V.K. Basavaraj ; A.G. Manoj ; K.S. Narayan
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 552 –555
- DOI: 10.1049/ip-cds:20030947
- Type: Article
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The light-detecting properties were studied for devices fabricated by a method involving screen-printing of an active semiconducting polymer layer. The active layer in the device is a blend consisting of an intrinsically n-type polymer poly(benzimidazobenzophenanthroline) dispersed in a matrix of intrinsically p-type polymer poly(3-octylthiophene). The anode in the device is a doped conducting polymer. The photocarrier generation efficiencies in the active layer are enhanced due to formation of donor–acceptor networks at small length scales. The solution processing is advantageous in forming devices on flexible and curved substrates. - Author(s): S.C. Jain and V.K. Tanwar
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 556 –558
- DOI: 10.1049/ip-cds:20031141
- Type: Article
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Ultrathin films of alkoxy alkyl amino silanes functionalised with photochromophore moieties have been grown on glass and quartz substrates by self-assembly (SA) techniques. The films have been selectively photodimerised with polarised UV light using photomasking to produce anistropic ordered structures locally. These ordered structures produce uniform planar orientation of nematic liquid crystals. Liquid crystals being birefringent (Δn=≈0.10–0.25), a high optical contrast is produced between uniformly aligned and non-aligned regions when viewed between crossed polarisers. This has given rise to the possibility of creating a new type of optical storage liquid crystal display. It has been possible to store line patterns with a line resolution of ≈20 μm by this technique. Such films can be used to record holographic gratings using UV polarised light. - Author(s): P. Prem Kiran ; G. De ; D. Narayana Rao
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 559 –562
- DOI: 10.1049/ip-cds:20031131
- Type: Article
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Nonlinear optical properties of Ag–Cu nanoclusters codoped in a SiO2 substrate prepared using the sol–gel technique are investigated under the influence of the second harmonic of a high-power nanosecond Nd:YAG laser. These films show self-defocusing nonlinearity and good nonlinear absorption behaviour. The nonlinear refractive index decreased with decreasing particle size. The nonlinear absorption, however, increased with increase in Cu concentration. The observed nonlinear absorption is explained through an interband absorption mechanism. Nonlinear scattering from the nanoparticles is also observed at higher intensities. - Author(s): C.P. Singh ; P. Sharma ; S. Roy
- Source: IEE Proceedings - Circuits, Devices and Systems, Volume 150, Issue 6, p. 563 –568
- DOI: 10.1049/ip-cds:20031069
- Type: Article
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A detailed and accurate analysis is presented of the low power spatial light modulation (SLM) characteristics of pharaonis phoborhodopsin (ppR) based on nonlinear intensity induced excited-state absorption. Amplitude modulation of probe laser read beam transmissions at 390 and 488 nm, corresponding to the peak absorption of ppRM and ppRL states of the ppR photocycle by write beam intensity-induced population changes at 498 nm, corresponding to the peak absorption of the initial ppR state, have been analysed using the rate equation approach. The SLM characteristics are shown to be sensitive to the normalised small signal absorption coefficient (β), the rate constants of intermediates and absorption cross-section of the ppR state at probe wavelength (σ1p). There is an optimum value of β for which maximum percentage modulation can be achieved. It is shown that for ppRM and ppRL states, at typical values, modulation up to 35.9% and 97.2% can be achieved for a laser write beam intensity of 5 mW/cm2 and 1 W/cm2 respectively. It is shown that 100% modulation of the read beam can be achieved for σ1p=0. SLM with ppR can be achieved at lower pump powers compared to wild type bacteriorhodopsin. The analysis demonstrates the usefulness of ppR for device applications due to its unique spectral characteristics, especially as a UV filter.
Editorial: Selected topics from Photonics 2002
Fibre access network for India as India poises for growth
Novel photonic devices in few-mode fibres
Development of rare-earth doped fibres for amplifiers in WDM systems
Measurement of chromatic dispersion in optical fibres using a common path polarisation interferometer
LiNbO3-based integrated optical network analyser for vectorial structure characterisation of fibre Bragg gratings
Production and characterisation of Bragg gratings written in high-birefringence fibre optics
Performance evaluation of WDM components based on tunable dielectric membrane technology
Ultrafast optical clock recovery: towards a system perspective
Numerical model of the dynamic absorption variation in QW-EAM for ultrafast all-optical signal processing
Multiperiod virtual topology design in wavelength routed optical networks
Long wavelength lasers on GaAs substrates
Characterisation of intrinsic and compensated defect microstructures in dilute III–V–N alloys
Design optimisation for high-power high-brightness parabolic bow-tie laser diodes
Adaptable method for modelling optical fields in VCSELs
Impact evaluation of the SOA spontaneous emission in ultrafast all-optical processing schemes
Solution processing of active semiconducting polymers and conducting polymer anodes for fabricating photodetectors
Photoresponsive self-assembled monolayer/photopolymer film for optical information storage using liquid crystals
Nonlinear optical properties of copper and silver nanoclusters in SiO2 sol–gel films
Spatial light modulation with pharaonis phoborhodopsin
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