摘要:

Upper and lower bounds are derived on error probability for direct-detection binary optical communication in the presence of jitter. Symbol-conditioned moment generating functions are employed, enabling the various stochastic impairments encountered, signal dependent compound Poisson statistics, coloured additive Gaussian noise and intersymbol interference, as well as timing errors in the signal elements or sampling instants, to be accommodated. The bounds are shown to be tight for a wide range of parameter values encompassing and extending significantly beyond those encountered in practical systems. They are then used to examine the influence of jitter on system performance.

DOI:10.1049/ip-j.1985.0059

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The concept of an ‘intrinsic’ mode has recently been devised as the basis for a systematic theory of wave propagation in slowly varying waveguides. An intrinsic mode is a self-consistent plane-wave spectrum which is approximated, to lowest order in the slow scale, by a more conventional adiabatic mode. However, where the adiabatic mode breaks down (at its transition from bound to cutoff behaviour) the intrinsic mode is uniform, and correctly predicts the radiation which occurs into the substrate or cladding. The object of this paper is to summarise the relevant theory and to present numerical computations of the intrinsic modes for a model problem consisting of a dielectric wedge with plane boundaries.

DOI:10.1049/ip-j.1985.0060

出版商:IEE    

年代:1985

数据来源: IET

摘要:

IRW lasers were examined by electroluminescence, photoluminescence, cathodoluminescence, X-ray topography and electron-beam-induced current imaging. Dark line defects were observed in some devices and were found to be associated with lattice dislocations. These defects could be forced to grow by aging the devices and are associated with poorly lattice matched epitaxial growth. Dark spot defects were also observed in some devices and could be generated by exposure to extremely high current densities. These observation techniques can be used to screen out wafers that may produce defective devices later in processing, and complement stringent individual device validation tests.

DOI:10.1049/ip-j.1985.0061

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The electromagnetic properties of optical disc resonators are analysed by the effective dielectric constant method. The assumptions inherent in this method are clearly defined, thus enabling the requirements of a complete electromagnetic model to be stated. The present formalism is applicable to structures where the radial boundary is defined by index and/or gain changes. An eigenvalue equation is obtained for the complex resonant frequency of the structure. Analytic solutions to the eigenvalue equation are obtained using material and device parameters relevant to disc resonators fabricated in III–V heterostructure semiconductor materials. The complex eigenvalue gives not only the resonant frequency (wavelength), but also the Q-factor of that resonant mode. An outline is given of the applicability of the device to optoelectronic integrated circuits, and also a brief discussion is given of a number of methods for tuning the resonator.

DOI:10.1049/ip-j.1985.0062

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Detailed calculations have been made to obtain the profiles of optical grating structures formed in a photoresist film lying on multilayer reflective substrates. Because of the multiple reflections from the various interfaces, the exposed resist profile has a complex form which can be changed by adjusting the layer thicknesses. Some comparisons with experimental results are presented.

DOI:10.1049/ip-j.1985.0063

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Optical propagation in semiconductor waveguides has been analysed in three ways: the semi-analytic ‘effective index’ method and two numerical methods based on variational techniques. Comparisons have been made using three semiconductor waveguide structures, and some fundamental limitations to accuracy have been identified. The techniques have also been used to calculate the transfer length for directional couplers.

DOI:10.1049/ip-j.1985.0064

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A time-dependent theory of optical bistability is developed and applied to laser amplifiers and passive semiconductor etalons. Results of the theory show an output intensity spike in switch-up which occurs after a time delay determined largely by the carrier recombination time, and before which the transition is unstable. Although for passive etalons the spike is rather broad (of order 1 ns for parameters appropriate to GaAs at 0.85 μm or InGaAsP at 1.55 μm) and of low amplitude, for amplifiers it is roughly an order of magnitude narrower and higher in amplitude. As a consequence, it is predicted that clock speeds for semiconductor bistable switching elements will be limited to rates commensurate with the carrier recombination time, not only for switch-down operations (as already well known) but also for switch-up operations.

DOI:10.1049/ip-j.1985.0065

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A vectorH-field formulation is used here for the solution of GaAs/GaAlAs rib waveguides. The material distribution and guide cross-section can be arbitrary, and dielectric constants are lossfree but arbitrarily anisotropic. The penalty method has been used to eliminate spurious solutions and to improve eigenvector quality. The effect of using infinite elements and the influence of artificial boundary conditions has been illustrated. Computed results are given and compared with the less accurate effective-index method and scalar variational method at 1.15 μm wavelength. For the finite element solutions we have introduced Aitken's extrapolation to speed up the convergence.

DOI:10.1049/ip-j.1985.0066

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The radiation pattern is evaluated of a travelling wave antenna situated on the interface between two dielectrics. When the dielectric constant is the same on either side, the beam emitted by the travelling wave has a narrow Gaussian profile, and is paraxial with its plane. As the dielectric becomes different on the two sides the paraxial beam property remains, but the discontinuity inhibits considerably the radiated power. Bearing in mind the beam-restricted nature of the bending loss from smooth curved optoelectronic waveguides, this suggests interference as a physical mechanism for reducing their bending loss. This confirms and justifies previous calculations using simpler boundary conditions. The range of dielectric constants for which the effect would operate is predicted.

DOI:10.1049/ip-j.1985.0067

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Partition noise from low-coherence lasers is shown to have a significant effect on the performance of a multimode fibre-optic system with chromatic dispersion. A relationship between the statistics of partition and the resulting system noise is derived and shown to be consistent with actual system performance.

DOI:10.1049/ip-j.1985.0068

出版商:IEE    

年代:1985

数据来源: IET