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2.6 Connecting and splicing fibres

There are two different types of fibre joint that need to be considered: permanent splices (the equivalent of soldered or crimped connections on copper cables) and demountable connectors.

Splices are used along a route to allow a link to be built up from convenient lengths of cable. The lengths are typically 2 km. Fibre is manufactured in lengths longer than this, but, once put in a cable, lengths longer than 2 km are difficult to transport and lay. Splices are also used t
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2.5 Non-Linearity

A linear system can be defined in two ways: (1) one which obeys the principle of superposition, and (2) one possessing the frequency-preservation property.

If we consider an optical fibre with electromagnetic field as the input and output, then provided that the power level of the input signal is not too great (less than 1 mW, which is 0 dBm), the fibre may be well modelled by a linear system for most purposes.

When fibre is used for a single point-to-point link to convey a digita
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Activity answers

Study Note: As outlined in the text I have not provided answers to all Activities. This is for two reasons:

  1. For some activities only you can devise the answer and any I gave would be distracting or unhelpful.

  2. For others in-text answers are given.


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6.3 Where is the complexity and what is it?

When I reflect on my experiences of child-support, I attribute the properties of mess, complex, or hard-to-understand to the situation. So, are mess, complex, and hard-to-understand the same thing? If they are, why is the course called Managing Complexity, rather than, say, Managing Messes? A glib answer is you might not have been attracted to it because of the everyday meaning of mess. Yet another answer is that complexity is a rich term whose everyday meanings have been further enriched by
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5.7 Being ethical

As outlined in Table 2, ethics within systemic practice are perceived as operating on multiple levels. Like the systems concept of hierarchy, what we perceive to be good at one level might be bad at another. Because an epistemological position must be chosen, rather than taken as a given, the choi
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3.5 The story so far

I have been discussing ethics as related to labelling things as ‘good’ and ‘bad’ or using more parochial words as substitutes. Different kinds of things could be said to be ‘good’ or ‘bad’, including means, ends, relationships, feelings, appearances, radiation levels and so on. The big ethical problem is how to combine this variety of things to reach a judgement, especially when combining them, it is possible that we end up with ambiguity or contradictions. I have explored the
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1.6 Final vocabulary

Any ethical analysis has to be grounded on something, otherwise the analysis has no end. And since reasons will be couched in words, I think it is helpful to look at what the philosopher Richard Rorty has called a ‘final vocabulary’. He suggests:

All human beings carry about a set of words which they employ to justify their actions, their beliefs, and their lives. These are the words in which we formulate prais
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1.4 What is ethics?

I'd like to introduce an idea of ethics based on the work of G. E. Moore, a Cambridge Don who died fifty years ago. Bearing in mind that concerns with ethics date back at least to the Ancient Greeks, you might not be surprised that I bring in some ideas from Moore's Principia Ethica, a text written over 100 years ago but articulated in a particularly clear and plain-speaking style. Moore's take on things is that when ‘good’ and ‘bad’ are involved, then we're in the realm of eth
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1.2 Ethical examples

But is this a tenable position? In other words, is it only the people who use the technologies who carry the ethical burden? Conversely, is ethics of any interest to engineers, programmers and scientists? What, in the first place, constitutes an ethical issue? To begin examining these questions, let's look at some examples.

Example 1: Th
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7.4 Depositing compounds

As well as conducting metal layers, device fabrication requires dielectric, insulating materials and these are mostly chemical compounds rather than simple elements or alloys. By far the most widely used of these is silicon oxide (either as a glass or as crystalline quartz), but other oxides and nitrides are also common, plus polymers and a selection of more exotic materials.

Such compounds generally have very high melting points, or decompose under heating, so cannot be deposited by ev
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3.1.5 Digital media for medical X-rays

Digital cameras have revolutionised the family album. However, the initial driver for CCD imagers in particular was specialised applications such as the capture of high-quality astronomical images, especially on remote satellites and space probes, from where it is unfeasible to collect film and from where continuous, real-time, high-bandwidth data streams are impractical. The CCD camera system, with its combination of high-sensitivity image capture, high-fidelity read-out and long-term storag
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4.8 Assess and review again

If you've been following the stages of our problem-solving map, then the chances are you're ahead of me here (Figure 19). Yes, if it works, hurrah; if it doesn't then off we go again, all the way back to ‘possible solutions’ and selecting the best of the rest. Or maybe even going back to the be
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4.7 Build prototype/demonstrator

The physical models we talked about earlier are prototypes or demonstrators of a sort. However, for the purposes of making a clear distinction in the process, I'm referring here to prototypes or demonstrators as functioning preliminary models of the essential finished product or construction or service, bringing together all the elements of the design that may or may not have been previously physically tested (Author(s): The Open University

5.1 Overview

The enquiry team set up by the Board of Trade, and sitting in Dundee Court House, held an initial session lasting several days starting on Saturday 3 January 1880. There were three members chaired by Mr Rothery, Commissioner of Wrecks. The others were Colonel Yolland, the Inspector of Railways, and Mr W H Barlow, president of the Institute of Civil Engineers, and a distinguished practising civil engineer.

Henry Rothery was a mathematics graduate but trained as a barrister. He had been a
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5.2 Vibrating string: speed of wave propagation

If standing waves are set up when two travelling waves moving in opposite directions interact, then how are standing waves set up on a string and why are they set up only at certain frequencies?

To help answer these questions, I want you first to imagine a length of string that is fixed at one end and held in someone's hand at the other. Suppose the person holding the string flicks their end of the string in such a way that an upward pulse is sent along the string.

As the pulse pa
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4.2 Frequency, wavelength and the speed of sound

The speed of sound has a joint relationship with both the wavelength and the frequency of the sound. To see why, recall that at the end of Section 2.5, in connection with the wave produced by a tuning fork, I said ‘in the time it has taken for the source to go through one cycle of oscillation, the wave h
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2.7 Summary

Pressure in the air is related to how closely packed the molecules are. Other things being equal, more closely packed molecules are at a higher pressure than more dispersed molecules. Sound is associated with fluctuations of the air pressure caused by local disturbance. Fluctuations of pressure travel outwards away from the disturbance, carrying energy imparted by the disturbance.

A simple form of local disturbance to air pressure is a vibrating tuning fork. It generates a pressure wave
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5.3 Purposeful and purposive behaviour

It is possible, as observers, to ascribe a purpose to what we or others do, the actions we take. How particular actions, or activities are construed will differ from observer to observer because of their different perspectives, which arise from their traditions of understanding. For example, in Author(s): The Open University

6 Part 2: 2 Immersing yourself in complexity

The first three activities in Figure 4 are to plan a strategy, then to immerse yourself in an example of complexity, and then represent that complexity through drawing a rich picture. I've selected a rich picture as the focus of this task because it is a means of bringing you into a r
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11.5.4 Analogy

Analogy draws on similar situations to provide ideas for invention and design. Alexander Graham Bell used the analogy of the human ear when designing telephone apparatus to receive sound. As mentioned above, his first receivers were much better than his transmitters where the analogy with the ear didn't work as well. When devising their flying machine, the Wright brothers used the analogy of soaring birds twisting their wings to restore balance. They designed the wings of their aircraft to be
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