IEE Proceedings - Optoelectronics
Volume 144, Issue 2, April 1997
Volumes & issues:
Volume 144, Issue 2
April 1997
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- Author(s): R.W.A. Scarr ; J.R. Collington ; W.A. Crossland ; M.P. Dames
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 2, p. 53 –60
- DOI: 10.1049/ip-opt:19970882
- Type: Article
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53
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The use of an optical crossbar provides a means of overcoming the intermodule interconnection problems of very large (terabit/s) electronic ATM switches. The operation of the hybrid electro-optic switching module (ETOSET) is described and the place of ETOSET in a network context is discussed. A novel control algorithm minimises contention for switch paths and gives a low control processing overhead. Performance is evaluated in terms of switch size, cell loss and control overhead. - Author(s): S. Oku ; Y. Shibata ; T. Takeshita ; M. Ikeda
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 2, p. 61 –68
- DOI: 10.1049/ip-opt:19970653
- Type: Article
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The paper describes a 4 × 4 laser diode optical gate switch made on an InGaAs/GaAs single quantum well GRIN-SCH wafer. The switches were made very compact (only 1.1 × 1.6 mm) by using a Y reflection type optical branching/combining circuit with wide-angle splitting. The light signal launched into an input port is transmitted to an output port through seven gate waveguides and six Y branching circuits. All of the paths between the input and output ports exhibit lossless switching operations when a current of 16 mA (average value) is injected into one gate. The excess loss of the Y branching circuit is estimated to be 0 dB for through coupling and 4 dB for crosscoupling. Good fabrication uniformity of the individual device elements (i.e. the gate waveguide and Y reflection type branching circuit) were confirmed in an area of 10 mm × 10 mm, which was one unit of the photolithography process used in the experiments. However, a significant difference in gain characteristics between the input–output paths in the 4 × 4 switches was observed. The disagreement between the uniformity of the individual elements and the scattering of the path gain characteristics can be explained by the zigzag propagation of the light beam eccentrically launched into the waveguides through the Y reflection type branching circuit. - Author(s): G.C. Gupta ; P.J. Legg ; D. Uttamchandani ; I. Andonovic
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 2, p. 69 –74
- DOI: 10.1049/ip-opt:19970754
- Type: Article
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69
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Coherence multiplexing exploits the coherence properties of optical sources so that many users may be multiplexed onto a single physical channel giving a secure, asynchronous mode of transmission, free of central network control. In the paper, for the first time, the system performance limitations owing to the impact of interference from unwanted users is presented and the suitability of LED, single-mode Fabry–Perot laser and DFB sources are considered. It is concluded that the single-mode Fabry–Perot is preferred, offering readily achievable interferometer length tolerances and near complete RF rejection of interferometric noise at the receiver. However, interferometric noise still limits the network capacity: a linewidth of 1 nm permits 17 users to be simultaneously offered a single video channel with a BER < 10-9. - Author(s): Y.R. Zhou ; L.R. Watkins ; J.S. Hornsby
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 2, p. 75 –82
- DOI: 10.1049/ip-opt:19970753
- Type: Article
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75
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Postdetection filtering strategies are investigated as a means of compensating the waveform distortion caused by the combined effect of chromatic dispersion and self-phase-modulation in intensity modulated, direct detection (IM/DD) systems. A design technique based on realisable filter models and a rigorous performance evaluation is introduced. In addition, a method of finding the theoretical optimum filter is given, providing a measure of the achievable system performance and the efficacy of the various filtering strategies. It is shown that the optimised postdetection filtering is effective in reducing the system power penalty, and the relative merits of different filters are quantified. The optimised filters are also shown to be tolerant to various system impairments, such as noise, timing jitter and perturbation of filter parameters. - Author(s): R. Orobtchouk ; A. Koster ; D. Pascal ; S. Laval
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 2, p. 83 –86
- DOI: 10.1049/ip-opt:19971037
- Type: Article
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A standard SIMOX substrate with 0.2 µm silicon film can be used for integrated optics. A lateral P+–I–N+ structure in the silicon film is proposed to obtain electro-optical phase modulation by carrier injection. Field confinement is ensured by a rib-loaded geometry. Simulations have been performed to estimate waveguide losses for such 2D-guiding structures suitable for phase modulation. Quasi-singlemode propagation with low losses in the doped regions and low additional loss under injection conditions is predicted. - Author(s): K. Suto ; T. Kimura ; J. Nishizawa
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 2, p. 87 –90
- DOI: 10.1049/ip-opt:19970755
- Type: Article
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Low-threshold semiconductor Raman lasers with a tapered waveguide structure with GaP core and AlxGa1-xP cladding layers have been operated in a quasi CW operation condition. It has been found that the first Stokes light output power nearly perfectly saturates when the pump power is increased, and this has been attributed to lasing of the second Stokes light. This effect will be useful for realising a low-noise light wave source. - Author(s): D. Rowland
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 2, p. 91 –96
- DOI: 10.1049/ip-opt:19970756
- Type: Article
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Conformally transforming the scalar Helmholtz equation for a step-index planar waveguide with a constant bend radius and assuming a bend radius large in comparison to the core half-width yields a differential equation whose solutions can be written in terms of Airy functions. A correct expansion of the leaky mode field in terms of these Airy functions and matching the field and its derivative across boundaries yields an eigenvalue equation whose complex roots give the leaky mode propagation constant and bend loss directly. This allows a second-order Taylor series expansion for the bend loss as a function of wavelength over the spectrum of a pulse to be determined. A comparison between bend loss for a cw wave and a pulse with the same carrier frequency is made. - Author(s): P.W. Leech ; M.F. Faith ; C.M. Johnson ; M.C. Ridgway ; M. Bazylenko
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 2, p. 97 –100
- DOI: 10.1049/ip-opt:19970782
- Type: Article
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p.
97
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Low loss channel waveguides have been formed in silica-on-silicon by implantation with 5 MeV Si and Ge ions. In these experiments, the substrate was comprised of an undoped layer of silica (30 µm thick) which was grown by plasma enhanced chemical vapour deposition (PECVD). The optical loss characteristics of the waveguides, as measured at both λ = 1300 and 1550 nm, were independent of the implanted ion species. A minimum in the attenuation loss (α) of ~0.10–0.20 dB/cm was obtained following both a pre-implant (1050°C) and a post-implant (400–500°C) anneal of the waveguides. The ability to produce a minimum in α by pre-implant annealing has been attributed to the thermally induced relaxation of the densified structure in the as-grown layer. Only a comparatively small degree of compaction was measured for Si-implanted samples which did not receive a pre-implant anneal. In contrast, the much larger degree of compaction in the pre-implant annealed samples was similar in magnitude to that observed in fused silica. These are the first reported examples of ion-implanted waveguides using a substrate of silica grown by PECVD. - Author(s): G. Weitman and A. Hardy
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 2, p. 101 –103
- DOI: 10.1049/ip-opt:19970829
- Type: Article
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p.
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The coupling coefficient in corrugated rib waveguides with rectangular teeth is calculated as a function of the rib widths. For sufficiently wide ribs (a few wavelengths in the material) the coupling coefficient asymptotically approaches its slab waveguide limit. But for narrower ribs the coupling coefficient drops rapidly with the rib width, whereas the power filling factor is almost unaffected owing to the strong field confinement. The effect on the threshold conditions of DFB lasers is also considered. - Author(s): M. Wada ; H. Okamoto ; M. Kohtoku ; K. Kawano ; Y. Kadota ; Y. Kondo ; K. Kishi ; S. Kondo ; Y. Sakai ; I. Kotaka ; Y. Noguchi ; Y. Itaya
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 2, p. 104 –108
- DOI: 10.1049/ip-opt:19971019
- Type: Article
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p.
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Laser diodes monolithically integrated with spot-size converters operating at 1.3 µm, and having an almost circular narrow emitted beam, have been successfully fabricated using 2 inch (50.8 mm) full wafer fabrication technology. The spot-size converters consist of a lateral taper, thin-film guiding layer and ridge structure. The epitaxial structure is designed to have wide fabrication tolerance with no deterioration of device characteristics. The investigation of the coupling-loss dependence on the dimension parameters in the spot-size converters confirms that this device has a wide fabrication tolerance for these parameters. Furthermore, butt-coupling loss to fibre as low as –1.3 dB is attained with alignment tolerance wide enough for passive alignment. The overall device is as short as 450 µm, enabling high availability from one wafer. - Author(s): J. Hendrix ; G. Morthier ; R. Baets
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 2, p. 109 –114
- DOI: 10.1049/ip-opt:19971091
- Type: Article
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p.
109
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A static model for facet heating and thermal runaway in double heterostructure laser diodes leading to catastrophic optical damage (COD) has been implemented. This model has been used to investigate the influence of unpumped facet regions. It has also been shown how optimisation of the device parameters can result in a higher COD power level. With the results of this analysis, the parameter-set of a laser emitting at 780 nm has been improved, resulting in a COD power level that is 1.5 times higher. - Author(s): Y. Li
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 2, p. 115 –119
- DOI: 10.1049/ip-opt:19970522
- Type: Article
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p.
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The propagation and imaging of two orthogonally polarised Gaussian optical beams passing through a nonlinear graded-index rod lens are analysed using a variational approach, and it is concluded that there are two regimes of propagation, collapse and oscillation. The results show that the nonlinear interaction of two optical beams has great effects on the propagation and imaging characteristics of optical beams, and that one beam can control the propagation and imaging of the other beam. - Author(s): C. Juang ; C.B. Tsai ; J. Juang
- Source: IEE Proceedings - Optoelectronics, Volume 144, Issue 2, p. 120 –124
- DOI: 10.1049/ip-opt:19970830
- Type: Article
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p.
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A study of charge oscillations due to electron- and hole-coherent, and mixing tunnelling in coupled quantum well structures is given. The time-dependent picture of coherent tunnelling of an electron and hole wave packet is obtained by the application of the time-development operator of the time-dependent Schrödinger equation, and the time-dependent Schrödinger equation with the Luttinger Hamiltonian. Detailed physical mechanisms involving resonant coherent tunnelling on electrons, valence-band mixing effects on heavy- and light-hole tunnelling, spatial and mixing multiple tunnelling effects, in coupled quantum wells are described.
Highly parallel optics in ATM switching networks
Lossless operation of 4 × 4 laser diode optical gate switches using Y reflection type branching/combining circuits for large-scale integration
Capacity bounding of coherence multiplexed local area networks due to interferometric noise
Electrical filtering strategies to compensate waveform distortion in optically amplified IM/DD systems
Quasi-TE00 singlemode optical waveguides for electro-optical modulation at 1.3 µm using standard SIMOX material
Nearly perfect output power saturation of the semiconductor Raman laser
Nonperturbative calculation of bend loss for a pulse in a bent planar waveguide
Channel waveguides formed by ion implantation of PECVD grown silica
Reduction of coupling coefficients for distributed Bragg reflection in corrugated narrow-rib waveguides
Fabrication and coupling-to-fibre characteristics of laser diodes integrated with a spot-size converter having a lateral taper
Influence of laser parameters and unpumped regions near the facets on the power level for catastrophic optical damage in short wavelength lasers
Propagation and imaging of two orthogonally polarised optical beams in a nonlinear graded-index rod lens
Charge oscillations in coupled quantum wells
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