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Digital communications

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Optical-fibre communications became commercially viable in the 1970s and innovation continues today. This free course, Digital communications, will illustrate how very high data rates can be transmitted over long distances through optical fibres. You will learn how these fibres are linked, examine the technology used and assess the future direction of this continually developing area of communication.

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;
  • draw up a power budget for an optical-fibre communication link and use it to estimate the maximum link distance;
  • do bandwidth and dispersion calculations on multimode and single-mode fibre links;
  • explain the differences between standard single-mode fibre, dispersion-shifted single-mode fibre and non-zero dispersion-shifted fibre, and explain what is meant by dispersion compensation;
  • explain the consequences of non-linearities in optical fibre, describe the sources of loss at a joint between two optical fibres, calculate the loss due to Fresnel reflections, summarise the steps involved in fusion splicing. Summarise the functions of cabling of optical fibre;
  • do power-level calculations on optical components;
  • describe the different technologies available for optical amplifiers;
  • describe the structure and uses of directional couplers, describe the structure and uses of erbium-doped fibre amplifiers;
  • explain the different characteristics of lithium niobate electro-optical switches and MEMS optical switches;
  • describe how wavelengths can be multiplexed and demultiplexed for WDM.

By: The Open University

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Digital communications

Introduction

Unit image

This unit is from our archive and it is an adapted extract from Digital Communications (T305) which is no longer in presentation. If you wish to study formally at The Open University, you may wish to explore the courses we offer in this curriculum area. [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)]

By using optical fibre, very high data rates (gigabits per second and higher) can be transmitted over long distances (tens of kilometres) without amplifiers or regenerators. Optical fibre has completely superseded copper wires as the primary medium for cabled transmission over long distances. As demand for capacity has risen, fibre is now being used even in LANs and the access network. An understanding of optical-fibre communications is therefore very important for anyone with an interest in digital communications.

This unit is from our archive and is an adapted extract from Digital communications (T305) which is no longer taught by The Open University. If you want to study formally with us, you may wish to explore other courses we offer in this subject area.

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