Optical fibres characteristics

In connectors light source to optical fibre, power losses result from different space characteristics of the light source and the fibre. Each light source emits a beam in its typical shape whereas a fibre can accept only these rays within the acceptance cone. Some typical losses are presented in Figure 2. 

The prevalently used waveguides are optical fibres. Fibre technology is standard in the UV to near-IR, but also some fibres for light transport in the mid-IR have been developed. An overview of different IR fibre materials and their characteristic performance parameters is given in Table 1. More details can be found in a number of reviews focused on the material properties of IR transmitting optical fibres26 31. For some applications, as an alternative to optical fibres also hollow waveguides may be used. 

James, S. W. Tatam, R. P., Optical fibre long period grating sensors characteristics and application, Meas. Sci. Technol. 2003, 14, R49 R61... 

Brakel A (2004) Sensing characteristics of an optical fibre long-period grating Michelson refractometer. Ph.D. thesis, Rand Afrikaans University, p 317... 

Optical scattering in paper is an extrinsic property that depends on how the paper has been produced. For example, a sample of paper can be calendered differently and will have different optical scatter characteristics. Thus, it is not possible to quote an absolute scatter value for a particular type of paper fibre or mineral filler pigment. It is only possible to quote a value for the system of fibre and filler under a very particular set of production parameters, and to track how the value changes as the system and production parameters are changed. 

The principle developed here is to integer multiple optical fibre loops and curves within a thin textile substrate, the light being released by macrobendings, as illustrated in Fig. 4.12. With embroidery, the patterns described by the fibres (curves, loops, zigzags etc.) and the substrates (textile, membrane, paper etc.) to which they are stitched define the characteristics of the light emitted by the whole fabric. 

Several technologies able to be used for the development of communicative textile devices have been presented. Some of them are already used for the development of textile displays. Their emission of reflective characteristics allow their use for different types of applications. Emissive devices such as luminescent stmctures or optical fibres are preferred for high-visibility outfits for personal safety, for art and fashion design or for advertising events. Reflective devices offer a softer, more discreet colour change, which could preferentially be used for everyday applications such as communicative clothes, home furnishings or fashion. 

James, S.W. and Tatam, R.P. Optical fibre long-period grating sensors characteristics and application. Meas. Sci. Technol. 14(2003), pp. R49-R61 Farahi, F. Simultaneous Measurement of Strain and Temperature Using Fiber Grating Sensors. Proc. 11th Eng. Mechanics Conf. Fort Lauderdale, Conf. vol. 1 (1996), 351-354... 

The coupled mode theory is often used to describe the polarization characteristics, or modes coupling in optical fibre, and the reflection spectra of FBG sensors. When the optical response of an optical fibre is analysed based on the coupled mode theory, the electric field is normalized as j j E ( E (dxdy = 1. Based on the perturbation approach, the slowly varying amplitudes c are determined by the following coupled mode equations ... 

Optical fibres with high transparency allow signal transmission over long distances (up to 1000 m) without loss of quality. This characteristic is valuable in particular for long-distance measurements where the instrument cannot be placed near the sensor. 

Optical fibres can be used in the transmittance and ATR mode (a special ATR application is the remote sensor), and even in the reflectance mode. The development of special optical fibres for transmission, transflection or diffuse reflectance measurements favours on-line analysis of problematic product streams and reaction mixtures (solutions, suspensions, emulsions, melts, solids). Both quartz and fluoride (ZrF4-based) glass fibres are used, with the former having poor transmission characteristics above 2000 nm. 

Karabourniotis, G., Bornman, J.F., and Liakoura, V., Different leaf surface characteristics of three grape cultivars affect leaf optical properties as measured with fibre optics possible implication in stress tolerance, Aust. J. Plant Physiol, 26, 47, 1999. 

Simply stated, fibre-optic cable allows for the transfer of light from one point to another without going in a straight line, and as such their use in process analytical applications is highly seductive. In a likely NIR process application there may be multiple sample stream take-offs, each with different sample characteristics, located in positions spread around a process unit, with the only apparently convenient analyser location some distance away. 

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