摘要:

A vector correction is derived to the propagation constants obtained from a polarised analysis of graded-index optical waveguides. This general formula is reduced to a form suitable for use with semiconductor rib and strip-loaded waveguides. Corrected propagation constants calculated for a range of semiconductor rib waveguide structures coincide with available results from a full vector approach. Moreover, the vector correction term is always small, underpinning the accuracy of the simple and fast polarised approach for the first time.

DOI:10.1049/ip-j.1993.0017

出版商:IEE    

年代:1993

数据来源: IET

摘要:

Sophisticated optical functionality can be obtained from the S-SEED by the use of simple optical control techniques. Two modes of operation are described in which the S-SEED combines the advantages of both relational and logical optical switching elements. Theoretical and experimental results of the S-SEED being used for possible applications in self routing switching fabrics are presented and discussed.

DOI:10.1049/ip-j.1993.0018

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The optimisation of an optical receiver is discussed and transient charcteristics of two basic simple integrated receivers in CMOS systems are analysed and compared in detail. In analysis, a maximum current parameter is developed and used for optimisation design. Among these two receivers, the low-impedance configuration is presented for high-speed operation. SPICE simulation and preliminary experimental results with discrete devices are also illustrated and discussed.

DOI:10.1049/ip-j.1993.0019

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The authors determine that the sensitivity of a D-fibre methane gas sensor can be improved by overcoating the flat surface of the fibre with a high index layer. Using the finite-difference/perturbation theory technique, the enhancement factor over uncoated D-fibre is computed. The results compare favourably with those obtained from analytical expressions and the matrix method for a planar waveguide structure which models the overcoated D-fibre. From the oretical results it is concluded that the sensitivity can realistically be improved by an order of magnitude over an uncoated fibre.

DOI:10.1049/ip-j.1993.0020

出版商:IEE    

年代:1993

数据来源: IET

摘要:

Propagation through eccentrically cladded three-layer anisotropic guides is treated analytically. The boundary value problem is solved by appropriately expressing the fields inside each layer in terms of the cylindrical wavesM, Nand a longitudinal waveQ. The propagation properties of such structures are then investigated by studying the characteristic determinant equation resulting from the satisfaction of the boundary conditions. The numerical results show that anisotropy, combined with eccentricity, increases the operational bandwidth of such guiding structures for monomode operation.

DOI:10.1049/ip-j.1993.0021

出版商:IEE    

年代:1993

数据来源: IET

摘要:

An expression for the optical field in a self defocusing nonlinear medium is proposed and used to analyse the propagation characteristics of TE0waves supported by a three-layer nonlinear waveguide with a self focusing nonlinear substrate and a self defocusing nonlinear film. Numerical results for propagation are illustrated for four kinds of guided waves whose fields in the film are expressed by different Jacobian elliptic functions. These reveal the relation between nonlinearity measure and normalised frequency for waves guided with various dielectric constant and nonlinear coefficient distributions. The properties of the propagation constant for waves with their peak of the field profile in the film or substrate are also discussed. Moreover, numerical results for dispersion relations of TE0waves are given, and the stability analysis using the beam propagation method is also presented.

DOI:10.1049/ip-j.1993.0022

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The use of an asymmetric MachZehnder interferometric amplitude modulator to measure a relatively low frequency electric field strength is described. The sensitivity of an electric field sensor using a Ti:LiNbO3optical modulator is strongly affected by the shape of a electrode (probe antenna). To measure the low frequency electric field, a probe antenna of wide effective area is more useful than the usual dipole antenna. As proof of this, the optical modulator was fabricated with a plate-type probe antenna and the usefulness of this antenna tested for measuring low frequency electric field strength. Measurements were performed in the range 0.1 V/cm to 60 V/cm at 60 Hz through 100 kHz. Using a probe antenna of 10 mm × 10 mm, the output voltage of 10−2mV was measured with respect to the electric field strength of 0.1 V/cm at 60 Hz. By increasing the effective area of the probe antenna, better sensitivity was obtained over the measured range.

DOI:10.1049/ip-j.1993.0023

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The evolution of an optical pulse in a graded-index (parabolic profile) single-mode nonlinear optical fibre is treated by means of differential equation techniques. Using a slowly varying envelope approximation and an averaging method over the transverse direction, a differential equation of the nonlinear Schrödinger type is obtained for the unknown envelope function of the electric field. The inverse scattering method is then applied, leading to the equivalent system of Gel'fand-Levitan-Marchenko coupled integral equations. A new iterative solution to these equations is presented. As an example, numerical results for a hyperbolic secant initial pulse profile of variable amplitude are obtained and the behaviour of both the soliton and the radiation part of the solution is examined. Finally, in the special case of reflectionless potentials, the well known analytical single and double solitons are recovered.

DOI:10.1049/ip-j.1993.0024

出版商:IEE    

年代:1993

数据来源: IET

摘要:

A novel optical fibre gyroscope, with a structure making use of the combination of a Sagnac interferometer with an active fibre ring-resonator, is proposed and analysed. It can be regarded as a generalised structure of the conventional Sagnac interferometric fibre optic gyroscope (SIFOG). Counter-propagating optical waves in the gyroscope can circulate many times in the sensing loop into which an optical amplifier is incorporated to compensate partially for optical losses of each circulation. The optical response is effectively the sum of the optical responses of a series of conventional Sagnac interferometric fibre optic gyroscopes having effective loop length equal to the fibre loop length multiplied by the number of circulations. We show that the sensitivity of the proposed gyroscope can be two orders of magnitude higher than that for a conventional SIFOG and that the minimum detectable nonreciprocal phase shift limited by the amplifier noise is nearly one order of magnitude smaller than that of conventional SIFOG limited by quantum noise. These performance enhancements cannot be obtained by incorporating an optical amplifier into the conventional SIFOG structure.

DOI:10.1049/ip-j.1993.0025

出版商:IEE    

年代:1993

数据来源: IET