2.4.3 Polarization mode distortion

Because light is an electromagnetic wave, it has a ‘state of polarization’, which, for light in single-mode fibre, is at right angles to the path of the fibre. If you've not encountered electromagnetic waves before, all you need to appreciate is that as light travels down the fibre the electromagnetic field has an orientation across the fibre (Author(s): The Open University

2.4.1 Multimode distortion

With multimode fibre, the main cause of pulses spreading is the multiple paths that signals can traverse as they travel along the fibre. This phenomenon of multimode distortion is illustrated in Figure 5.


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2.2 Fibre types

A strand of glass (or plastic, but the best performance comes from glass) has a core surrounded by a cladding, where the refractive index of the glass in the core is higher than that of the cladding (see the box on ‘Refractive index>’).

Light is contained within the core by <
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1.1 Uses of optical fibre in communication

Using optical fibres, very high data rates (gigabits per second and higher) can be transmitted over long distances (tens of kilometres) without amplifiers or regenerators. As a consequence, optical fibre has completely superseded copper wires as the primary medium for cabled transmission over long distances. Until recently, however, optical fibre has been used less in LANs, where twisted-pair copper cable has been dominant. Similarly, fibre has been slow to penetrate the access network, from
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Learning outcomes

After studying this unit you should be able to:

  • convert between wavelengths and frequencies;

  • describe the main differences between lasers and LEDs as used as light sources for optical-fibre communications systems;

  • describe the difference between direct and external modulation of a laser;

  • describe the difference in structure and performance of step-index multimode, graded-index multimode and single-mode optical fibres;

  • d
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Acknowledgements

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Grateful acknowledgement is made to the following sources for permission to reproduce material within this unit:


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Acknowledgements

Except for third party materials and otherwise stated (see terms and conditions), this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence

Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit:

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5.1 Phase and phase difference

In this section I am considering sine waves that have the same frequency, but are out of step with each other.

Suppose we have two detectors at fixed points, A and B. At this moment in time A is in a high pressure region and B in a low pressure region. If we were to look again shortly later B would now in a high pressure region and A in a low pressure region. The pressures at A and B would be out of step with each other. The pressure variation at B is not in phase with that at A. The ex
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1.1 Music and technology

Music technology in one guise or another is part of everybody's life, because music is a part of almost everybody's life. For instance, if you are an instrumental performer of music, professional or not, then your instrument, be it the harp or the rock'n'roll drums, will be the result of considerable technological expertise on the part of the instrument maker. On the other hand, if you are not a performer but like to listen to music, the chances are that most of your listening is done via a h
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10.3.1 Cats eyes and road conditions

Sometimes the discontent comes from the fact that there isn't a product to satisfy a particular need. Percy Shaw was a road mender who was aware of the dangers of driving along unlit, often fog-bound, roads. One night in 1933 he was driving his car near his home in the north of England when his headlights were reflected in the eyes of a cat. This inspired him to invent the cat's-eye reflector that, when embedded at intervals in the centre of the road, reflected a vehicle's headlights and made
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4.1 An explanation

I will now elaborate on my answer from Exercise 1. I'm doing this because my internet search revealed more than I've written in the above answer, and to show that the invention of the telephone and its use by consumers is not as plain and simple as you may think. You we
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1 Part 1 Investigating the innovation process

In Part 1 I invite you to look around at the technological products in your home or at work and consider their development history and their impact on the lives of you and your family. I then define the key concepts associated with the process of invention, design, innovation and diffusion.


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Introduction

This unit aims to provide an understanding of invention, design, innovation and diffusion as ongoing processes with a range of factors affecting success at each stage. You will gain an understanding of the factors that motivate individuals and organisations to invent, and the creative process by which individuals come up with ideas for new inventions and designs, and you will gain an understanding of the obstacles that have to be overcome to bring an invention to market and the factors that i
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1.1.3 Features of diagrams

As there is variety in the types of diagrams we can see and use we need to think more broadly about what diagrams are trying to represent. One distinction which follows on from the discussion above is:

  • Analogue representations: these diagrams look similar to the object or objects they portray. At their simplest they are photographs of real objects and at their most complicated they are colourful, fully labelled drawings of the inner workings o
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5.8 Additional treatment

As a result of strict standards set by the EU Directive on the Quality of Drinking Water, it is now often necessary for drinking water to have further treatment to remove components such as nitrates and trace of organics.


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2.1 Meanings of ‘imagination’

A natural starting point is to consider the ways in which ‘imagination’ and related terms such as ‘imagine’ and ‘image’ are used in everyday contexts.

Activity 1

  1. Imagine someone aski
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2.5 Why intentions?

Most of the rest of Grice's paper is dedicated to spelling out a way of identifying the meaning of an individual utterance ‘on an occasion’ with the content of the utterer's intentions (Step One). The hard task he faces is to say what type of intention creates meaning. If someone shouts ‘I saw a film last night’ extremely loudly at their brother with the intention of making this brother fall off his bike, this ‘utterance’ (if that is the right word) does not thereby mean fall o
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References

Brown, A. (1995) Organisational Culture, London, Pitman.
Crace, J. (2000) ‘Feel at home with a job abroad’, Guardian, 14 October.
Drennan, D. (1992) Transforming Company Culture, London, McGraw Hill.
Hofstede, G. (1980) Culture's Consequences: International Differences in Work Related Values, London,
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3.3 Deciding what to ask for

What you ask for will very largely determine what you receive. You are therefore faced with a crucial but complicated set of judgements and choices in translating your overall requirements into suitable ‘ask size’ chunks. Your global requirement for support has to be refined into a range of specific requests which it will be feasible and appropriate to direct to the particular cohort(s) of donors and supporters you seek to involve.

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4.2 Problem solving

Involving the whole team in the problem-solving process shows that you value their experience and knowledge in devising a solution. It may also be appropriate to involve other stakeholders and/or the project sponsor. If problems are solved jointly there is usually wider ownership of the solutions and their implications; and, if more resources are agreed to be needed or new procedures are put into place, there is also likely to be more support.

Problem solving can be broken down into a s
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