摘要:

One of the important deficiencies of semiconductor laser amplifiers, compared with fibre amplifiers, is the crosstalk that is created by four-wave mixing and gain saturation. If the electron density were controlled at all points along the amplifier, the crosstalk could be greatly reduced. The paper looks at the theory of optoelectronic feedback, using the spontaneous emission as a measure of the electron density and introducing both linear and differential feedback into the injected current, to control the electron density in an amplifier. The paper also examines the consequential reductions in four-wave mixing. It is concluded that it may be feasible to effect this, particularly in an integrated amplifier. Preliminary practical trials are under way.

DOI:10.1049/ip-j.1992.0018

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The paper deals with the problem of surface mode reflection from an abruptly terminated W-fibre. The problem is solved by use of the modified variational technique and the quasi-vector approximation. The results obtained are compared with those developed by the scalar optics theory and by the effective-refractive-index method. It is shown that the approximate techniques do not present a detailed description of the reflection characteristics.

DOI:10.1049/ip-j.1992.0019

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The authors have developed a set of equivalent circuit models for optical logic gates based on the saturable gain and saturable absorption phenemona, and have implemented them on the iSMILE circuit simulator. These models have been created with a highly modular design to facilitate the construction of complex logic functions. Several design issues, such as logic threshold and switching speed, have been addressed. Models for the AND, OR, NAND, NOR and NOT gates, are presented, as well as detailed simulation results.

DOI:10.1049/ip-j.1992.0020

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Vector normal modes are determined for a waveguide with a circular core and unbounded cladding in close proximity to a dielectric halfspace. This model is applicable to D-shaped or polished fibres and to a tapered fibre in contact with or in close proximity to a plane. Results are presented to quantify birefringence and cutoff, and to link with other numerical vector techniques.

DOI:10.1049/ip-j.1992.0021

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The coupling coefficients of dielectric optical waveguides with more than one grating and with a periodic perturbation of the loss and gain are calculated for TE and TM modes. Analytical expressions for the coupling coefficient are given for the case of an asymmetric trapezoidal-like grating profile. Results obtained using various approximations of the unperturbed waveguide are presented and compared.

DOI:10.1049/ip-j.1992.0022

出版商:IEE    

年代:1992

数据来源: IET

摘要:

We present a set of experiments in which optical fibres are prepared with three optical fields of different frequencies to produce second harmonic generation. The results obtained are shown to be inconsistent with directional photoionisation models for second harmonic generation in glasses.

DOI:10.1049/ip-j.1992.0023

出版商:IEE    

年代:1992

数据来源: IET

摘要:

New 3-point finite difference formulae with equally spaced grid points are given for the analysis of scalar or semivectorial fields in waveguides with discontinuous refractive index profiles. The new formulae lead to more accurate calculations for the modes than the previously known methods, irrespective of the location of the discontinuities with respect to the grid points and without averaging the permittivity over meshes.

DOI:10.1049/ip-j.1992.0024

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Decision threshold placement for optically preamplified receivers is studied, with particular emphasis on the implications for timing sensitivity. These receivers can require an optimum threshold that is depressed significantly below the midrange of the vertical eye opening; by incorporating a new signal-shaping filter design into the receiver, improved tolerance to alignment jitter and slightly better sensitivity are secured, compared with the widely adopted near-raised-cosine receivers. This is of special significance for multigigabit systems, for which even a small timing error can represent a substantial proportion of a signal time slot. Accordingly, results are presented relating to systems operating in the 1 Gbit/s-20 Gbit/s range.

DOI:10.1049/ip-j.1992.0025

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The III-V AlGaInAs quaternary is particularly well suited to conventional molecular beam epitaxy, and many devices based on this material system have already proved of interest in high-performance microelectronics. However, although this lattice-matched-to-InP quaternary covers the same wavelength range as the well known GaInAsP system, it was not until recently considered as a serious challenger for optoelectronic applications. This is no longer the case, because of theoretical considerations and because of recent device achievements, especially low-threshold MQW laser diodes and high frequency electro-optic modulators.

DOI:10.1049/ip-j.1992.0026

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The paper presents an analysis of the losses of the optical power and the microwave performance of semiconductor microstrip gaps, taking into account the contact resistance. A condition for high efficiency of optical/microwave interactions is given.

DOI:10.1049/ip-j.1992.0027

出版商:IEE    

年代:1992

数据来源: IET