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1.9 Increasing complication, complexity and risk: summary

The three levels of change problem, simplicity, complication and complexity, can be associated with craft, engineering and systems engineering knowledge. The three categories of change problem represent different levels of uncertainty of what needs to be done and how to do it. The greater uncertainty brings increased risk. Although we tend to be risk averse we will take on greater risk if the returns are commensurate with doing so.

Human experience can be divided into three worlds. The
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Acknowledgements

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4.5 Fibre in LANs

Fibre has been slower to be exploited in LANs than in the core transmission network, for similar reasons to the delay in the use of fibre in the access network, but as the data rate demanded of LANs has increased, the case for using fibre has strengthened.

Although Ethernet specifications (IEEE 802.3 series) have contained standards for the use of fibre backbones for some time, it was with the development of Gigabit Ethernet and 10 Gigabit Ethernet (10 GbE) standards that fibre became t
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3.5 Wavelength multiplexing and demultiplexing

Wavelength multiplexers and demultiplexers are needed in order to be able to use wavelength division multiplexing. With just two wavelengths, the multiplexers and demultiplexers can be based on directional couplers because, as mentioned earlier in Section 3.2, couplers are naturally wavelength-de
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3.3 Optical amplifiers

Figure 22 shows in outline one possible structure for an Erbium-doped fibre amplifier (EDFA).

Figure 22
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3.2 Directional couplers

A simple yet valuable device is the directional coupler (Figure 19). A directional coupler can be constructed from two single-mode fibres by bringing them into close contact and heating so that the glass melts and the two fibres fuse. Light can then pass from one fibre to the ot
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3.1 Introduction

The basic optical-fibre link consisted of the source (laser or LED), the fibre and the detector, as was shown in Figure 1. Improvements in these components can increase the data rate, but the system is still a point-to-point transmission link and all signal processing, such as routeing
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2.7 Cabling

A distinction must be made between the optical fibre – a single strand of glass fibre – and the optical-fibre cable consisting of one or more strands of fibre and various protective coverings.

Bare optical fibre is fragile and vulnerable, and the cabling must provide the properties given below.

  • Tensile strength: The cable should prevent the fibre being strained when the cable is under tension. When the cable is being laid, for exampl
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2.6.1 Connectors

Many techniques have been used to design connectors that align the fibre ends accurately with high reliability and a long lifetime. The development of such components, at a low enough price, has been an important part of the overall development which has made fibre a feasible proposition for commercial transmission systems.

With fibre attenuation down to 0.2 dB km−1 (for single-mode fibre), the losses resulting from connectors and splices can be very significant over a whol
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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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Acknowledgements

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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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4.6 What matters?

When the laptop is confirmed to be uncompromised, it is interesting that none of the characters cheers, although they all seem to be relieved. In other words, when the statement comes up, ‘laptop is uncompromised’, people seem to think that is ‘good’, the outcome is fine. They seem to have forgotten that the technician is probably dead at the time. So, in their deliberations, a person's life is forgotten. I am sure that, if they were reminded of it, they would, of course, say that thi
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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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