摘要:

A simple explanation of inertial navigation is presented. The difference between ‘gimballed’ and ‘strapdown’ systems is explained. The performance requirements of a gyro for one nautical mile per hour aircraft IN system are derived.

DOI:10.1049/ip-j.1985.0049

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The historical origins of the differentiation between ‘inertial’ and ‘noninertial’ quality gyroscopes is explained and the use of ‘noninertial’ gyroscopes in vehicle systems is utlined. This encompasses use for vehicle stability, directional references and controls, sight line stabilisation and crude inertial navigation and guidance. This latter use emphasises why the terms above have been put in inverted commas. The applications require the vehicle positional attitude or the vehicle angular rate. Until recently, these have always been obtained by using position (or free) gyros and rate gyros, respectively, but the advent of high-speed computing has made it possible for rate gyroscopes to perform both tasks (but not, generally, vice versa). This has made it possible, in some cases, to replace two gyro systems by one system, with obvious savings, but the one system must combine the requisite qualities of the two it replaces. The qualities required of gyroscopes for the applications listed above are outlined and some typical parameters are quoted. The difference between 'iron' gyros and optical gyros in terms of their performance is emphasised, especially the noise and drift-rate characteristics. The importance of these characteristics with relation to the applications is discussed.

DOI:10.1049/ip-j.1985.0050

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The paper describes the behaviour of a serrodyne modulator in a closed-loop fibre-optic gyroscope. The general form of the driving waveform is described. A closed-loop computer model is used to investigate the behaviour of such a modulator and its associated errors in a gyroscope. Experimental results are included which show agreement with the model. It is concluded that certain of these errors affect the scale factor of the gyro and its linearity. To reduce the errors to acceptable levels it is necessary to control peak phase and minimise flyback time. The value of flyback time must be known to provide compensation in a closed-loop gyro.

DOI:10.1049/ip-j.1985.0051

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The paper discusses the feasibility of a novel heterodyne approach to the design of an all-fibre optical gyroscope. The IF is produced by source frequency modulation which also serves to reduce the effective source coherence. Such a technique offers distinct advantages in that the optical medium is completely passive, making it ideal for an all-fibre approach.

DOI:10.1049/ip-j.1985.0052

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Two signal recovery schemes are proposed and demonstrated for the fibre-optic gyroscope which allow it to be operated at very high rotation rates. Both techniques transpose the Sagnac phase shift into that of a low-frequency electronic carrier signal. Initial results are presented for both recovery schemes.

DOI:10.1049/ip-j.1985.0053

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The paper presents a new class of all-fibre devices based upon periodic coupling principles. The two basic devices which are described are a birefringent fibre polarisation coupler and a two-mode fibre transverse mode coupler. Both devices consist of a ridged plate which is used to periodically stress a fibre with a periodicity equal to the beat length of the modes to be coupled. This periodic stress has been shown to result in almost complete power transfer for both the devices described. These ‘in-line couplers’ have been shown to have several applications, e.g. amplitude modulators, notch filters, polarisers, mixers etc. One of the most important results of the work in this area was the development of an all-fibre frequency shifter based upon the principles of periodic coupling. More work needs to be done in the design and engineering of these devices, and there is still room for new ideas and approaches.

DOI:10.1049/ip-j.1985.0054

出版商:IEE    

年代:1985

数据来源: IET

摘要:

An optical-fibre frequency shifter is described that is based upon the serrodyne technique and uses a simple piezoelectrically strained fibre as the phase shifting element. Acoustic damping and electronic feedback techniques for improving the response of the phase shifter are reported.

DOI:10.1049/ip-j.1985.0055

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A method for coupling fibres to Ti-diffused waveguides in LiNbO3is described, by which ion-milled grooves in the LiNbO3substrate are used to locate the fibres. The coupling loss is analysed, and fabrication parameters optimised to minimise insertion loss due to modal mismatch. A net insertion loss of −2.6 dB has been measured for the coupler.

DOI:10.1049/ip-j.1985.0056

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The fabrication of very-low-loss single-mode optical-fibre couplers is described. The biconical fusion method has been used to investigate three types of single-mode fibre (i.e. depressed cladding, matched cladding and raised cladding), and losses of less than 0.05 dB have been obtained. Experimental evidence also shows that power transfer in the biconical fusion coupler cannot be supported by evanescent wave coupling between the cores of the fibres. The fabrication of polished-type couplers is also described for fixed and mechanically tunable output power splitting ratio couplers. Typically losses of less than 0.2 dB are possible.

DOI:10.1049/ip-j.1985.0057

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Polarimetric monomode optical-fibre techniques offer many advantages for sensing applications. Both line-integral and line-differential methods may be used. Special features of the polarisation behaviour of monomode fibres, which arise in a variety of sensors, are discussed, with particular reference to the separation of linear- and circular-birefringence components. Possible uses of nonlinear optical effects and the future requirements for specialised fibres are also discussed.

DOI:10.1049/ip-j.1985.0058

出版商:IEE    

年代:1985

数据来源: IET