摘要:

Rigorous analysis of polarization preserving optical fibres with three-layer elliptical cross-section is attempted, using Yasuura's mode-matching method with Bessel function expansion. The characteristics of the difference ΔBin the normalised propagation constants between two orthogonal dominant modes, which indicate the degree of polarisation-preservation, are investigated in detail for several combinations of the shapes of two boundaries, that is core-inner cladding and inner-outer claddings, with properly selected values of the refractive indices of the three regions in the cross-section. As a conclusion, better configurations for a polarisation-preserving single-mode fibre are discussed in detail for each three-layer dielectric optical fibre.

DOI:10.1049/ip-j.1991.0001

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The power in the core of a bent multimode slab is calculated on the basis of ray theory as a function of the angle round the bend, and as a function of the bend radius of curvature. The effect of cladding thickness is also taken into account. Measurement of the power in the core of a bent multimode fibre supports the validity of the two dimensional slab model used, and also the mechanism of refracting rays being responsible for the power transfer to and from the core of such bent fibres.

DOI:10.1049/ip-j.1991.0002

出版商:IEE    

年代:1991

数据来源: IET

摘要:

Free-carrier-induced index-antiguiding and thermal index-guiding effects in the proton isolated, (AlGa)As separate confinement hetero-structure laser diodes have been investigated in the pulse and CW conditions. The thermal index-guiding-induced far field narrowing has been used to evaluate the temperature rise in the active region during the laser pulse. The observed coincidence of strong thermal index-guiding with high series resistance and other unwanted properties of devices (which depend on H+-implantation parameters) indicated on a presence of defects in the stripe region. It has been found that proper post-implantation heat treatment of the hetero-structure slice can reduce thermal effects and improve laser characteristics. A proposed explanation is the heating-out of the implantation-induced defects in the stripe region.

DOI:10.1049/ip-j.1991.0003

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A general analysis is provided to evaluate the timing jitter performance of a delay and exclusive-OR type clock recovery circuit in an APD-based optical receiver. The contributions of the pattern noise and the jittery bit transitions owing to the finite slope of the received optical pulses in the presence of receiver noise to the timing jitter of the recovered clock are quantitatively assessed for various receiver parameters.

DOI:10.1049/ip-j.1991.0004

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A new field formulation to replace the usual Gaussian approximation for weakly-guiding single mode fibres in some special applications is presented. It enables the field far from the core axis to be represented accurately in a simple form, but maintains the advantages of the Gaussian approximation method. This formulation can be useful in applications such as twin-core fibres and fibre couplers where the evanescent behaviour of the modal field outside the core region is of prime concern. Our method shows a significant improvement over the Gaussian method when applied to cases such as twin-core fibre couplers where large core separations are required for long coupling length devices.

DOI:10.1049/ip-j.1991.0005

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The design of actively mode locked semiconductor lasers integrated onto a single substrate is studied using a new variation on the transmission-line laser model. The laser includes a distributed Bragg reflector to provide wavelength selective feedback. The behaviour of the device under various drive conditions is investigated. Pulses below 3 ps can be achieved by careful design of the Bragg region.

DOI:10.1049/ip-j.1991.0006

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The production of a narrow-band microwave modulated light beam by active mode-locking of a monolithic semiconductor laser diode is modelled. A self-consistent calculation of the light field, following a sinusoidal current injection into a restricted section of the component, allows evaluation of the microwave amplitude and phase response of the light emission as well as determining the stability of the solutions. We show that the propagation parameters inside the laser diode, such as the gain bandwidth and group velocity dispersion can be optimised to improve this response. The use of multisection laser diodes, similar to the devices presently developed to obtain cw tunable laser diodes, is proposed to engineer those propagation parameters.

DOI:10.1049/ip-j.1991.0007

出版商:IEE    

年代:1991

数据来源: IET

摘要:

Mode competition in three section DBR tunable lasers is studied with a simple Fabry-Perot like description. The problem is analysed from the point of view of tunable laser applications in multicarrier communication systems. The maximum power for single mode operation and the switching between adjacent modes are discussed.

DOI:10.1049/ip-j.1991.0008

出版商:IEE    

年代:1991

数据来源: IET

摘要:

Monolithic integration between an active and a passive waveguide directly butt-jointed in a single step of MOCVD is demonstrated at 1.5 μm. Buried ridge stripe (BRS) structures, consisting of a 250 μm long active region and a 1300 μm long passive waveguide, exhibit 25 mA threshold current, 60% coupling coefficient and an optical output power in excess of 5 mW.

DOI:10.1049/ip-j.1991.0009

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The paper analyses the applicability of the lumped and travelling-wave electro-optic interferometers as subsystems in the transmitter and receiver of the subcarrier-multiplexed (SCM) optical communication system. Signal-to-intermodulation-noise power ratio at the detector output is estimated when the interferometer is used as an optical modulator and as a down-converting mixer in the SCM optical communication.

DOI:10.1049/ip-j.1991.0010

出版商:IEE    

年代:1991

数据来源: IET