摘要:

Imaging characteristics of Gaussian beams through a nonlinear defocusing GRIN rod lens are studied. Analytical solutions of the beam width parameter, the distance of the focal plane and the linear magnification, in terms of the beam power, diffraction and the rod dimensions, are obtained using the variational method and the ABCD law. It has been found that the beam power can change the optical characteristics of defocusing GRIN rod lenses. Some numerical results are given.

DOI:10.1049/ip-j.1992.0053

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The paper investigates the temporal response of a passive fibre optic ring resonator illuminated by an amplitude stabilised single mode pulsed laser light source of frequency ω0. The output pulse shape is found to depend on the input pulse shape, the ratio of the source coherence time τcto the resonator delay time τ, and also the ring resonator phase delay ω0τ. Under certain conditions, periodic oscillations in output intensity occur, and the paper provides a simple physical explanation of these in terms of the resonator phase delay.

DOI:10.1049/ip-j.1992.0054

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The characteristics of signal-feedback-induced intensity modulation of a laser diode in a fibre optic gyro system is investigated theoretically and experimentally. The effect of the feedback is to induce an additional modulation term in the laser output which has the same waveform as the Sagnac signal and is amplified in amplitude (maximum 16 dB). The influence of this intensity modulation on the performance of a two-dimensional frequency-division multiplexed gyro system is to introduce additional terms sin 2φsiand sin φsicos φsjif detection is at the first harmonic of the bias modulation of gyroi, where φsiand φsjare Sagnac phase shifts in gyroiand gyroj, respectively.

DOI:10.1049/ip-j.1992.0055

出版商:IEE    

年代:1992

数据来源: IET

摘要:

An optical processor realising the versatile Faddeev algorithm is programmable and can be used for several computations such as matrix multiplications, decompositions and inversions just by changing the structure of the data stored. Optical processors have round-off spatial errors and noise limiting the accuracy of computations. It is shown that the use of a preprocessed Faddeev algorithm on an optical processor can produce more accurate results than an optical processor realising the standard Faddeev algorithm. The procedure for preprocessing and possible optical realisations of the preprocessed Faddeev algorithm on optical processors are described. Simulation results show the improved accuracy of such preprocessed Faddeev algorithm based computations.

DOI:10.1049/ip-j.1992.0056

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The amplitude and phase or frequency modulation properties for pump current modulation of a near travelling-wave semiconductor laser amplifier are examined. The investigations are performed numerically in the time domain with large-signal analysis and in the frequency domain with small-signal analysis. It is shown that the modulation bandwidth is increased by high pump current or high input power and that the small-signal modulation efficiency is increased by low pump current or low input power. The validity of the simulations is supported by experimental results.

DOI:10.1049/ip-j.1992.0057

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Mathematical models for travelling-wave semiconductor laser amplifiers are compared in the steady state for a simplified case where the exact solution is easily obtained. The frequently used model with the photon density averaged over the length of the amplifier is examined together with a simple perturbation model and a new orthogonal function model. The photon density averaging model is the most accurate. The perturbation model is less reliable because of its simplifications. For the orthogonal function model, the complexity grows much faster than the accuracy and therefore this model is unpractical.

DOI:10.1049/ip-j.1992.0058

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The variational approach for the circular-core fibres, formerly discussed by the present authors, is extended to treat graded-index elliptic-core fibres. The paper demonstrates the effectiveness of the variational approach when studying complicated problems. In order to bring out this effectiveness, a less complex scalar problem is considered. This problem is solved for deformed, circular-core fibres with a central dip in the refractive index profile, by considering it as special case of a graded-index elliptic-core fibres. This method is also computationally fast.

DOI:10.1049/ip-j.1992.0059

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The results obtained in an inter-laboratory evaluation of theoretical modelling methods for single-mode optical fibres, developed in the framework of the COST 217 project, are presented. Values of transmission parameters computed from four different fibre designs are compared with the experimental values obtained in a previous interlaboratory measurement campaign. The consistency of the results obtained with different calculation methods and the accuracy of theoretical predictions are analysed for every one of the usual characterisation parameters of the fibres. The accuracy of the refractive index profile data appears to be the main factor affecting the agreement between theoretically predicted and measured values of the transmission parameters.

DOI:10.1049/ip-j.1992.0060

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The impurity content and photocarrier mobility of commercially-grown Bi12SiO20was characterised. The mobilities were 0.12 cm2/V-s and 0.04 cm2/V-s for samples containing the lowest and highest impurity content, respectively. The difference in mobility is attributed to the formation of deep trapping levels, which is consistent with photocarrier transport dominated by hopping conduction.

DOI:10.1049/ip-j.1992.0061

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The performance of frequency shift keying distribution systems incorporating semiconductor laser preamplifiers are discussed. Upper bound on the performance which provides an appropriate means of assessing system performance is presented and used to explore the degree to which widely adopted Gaussian approximation accurately predicts error rate performance.

DOI:10.1049/ip-j.1992.0062

出版商:IEE    

年代:1992

数据来源: IET