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Unit information: Optical Communications Systems and Data Networks in 2016/17

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Unit name Optical Communications Systems and Data Networks
Unit code EENGM2001
Credit points 10
Level of study M/7
Teaching block(s) Teaching Block 2C (weeks 13 - 18)
Unit director Professor. Yu
Open unit status Not open

Students preferably should have taken the ‘Optoelectronic Devices and Systems’ unit.



School/department Department of Electrical & Electronic Engineering
Faculty Faculty of Engineering


Optical fibre communication systems are central to modern information infrastructure and carry the bulk of the world’s internet data. This unit requires the basic knowledge about optical fibre and components that the students already gained in the unit ‘Optoelectronic Devices and Systems’. This unit will mainly deal with high data speed digital transmission technologies over optical fibre, including the digital modulation of light at the transmitter, the signal transmission characteristics over optical fibre, and the detection/demodulation of optical signals at the receiver. The main contents in the order of delivery include:

Setting the context: The structure of modern communications networks, the various data networks, and the role of optical communications.

Digital modulation of light wave carriers: intensity modulation and coherent modulation formats and their signal characteristics. Components and technologies for the realization of these modulation formats. Transmitted signal power and quality.

Demodulation and Detection: Intensity modulation and direct detection. Square law detectors. Receiver signal to noise ratio and sensitivity. Demodulation of coherent modulated optical signals formats.

Optical fibre data transmission: The propagation of modulated light waves in optical fibre. The impairments to optical signals in optical fibre including loss, dispersion, and nonlinear effects. The effects of these impairments on intensity and coherent modulated optical signals, including pulse broadening, phase distortion, and timing jitter. Power penalties. System power budget. Optical signal to noise ratio. Limitations to bandwidth and transmission distance.

The correction of impairments: Regeneration of optical signals (3R: Re-amplification, Re-shaping, and re-timing). Optical dispersion compensation. Electronic dispersion compensation. Optical amplification including principles, amplifier characteristics, noise and cascadability. Transmission encoding and forward error correction (FEC).

Multiplexing: Fibre bandwidth and spectral efficiency. Shannon limits in optical fibre transmission. Methods of increasing optical fibre transmission capacity. Time division multiplexing (TDM). Optical time division multiplexing (OTDM) and soliton transmission. Wavelength division multiplexing (WDM). WDM components including filters and (de)-multiplexers. Specific issues and limitations in WDM systems including linear crosstalk and nonlinear cross modulation.

Widening the View: Likely developments in future optical communications technologies. A brief introduction to optical networks.

Intended learning outcomes

On successful completion of this unit, students will be able to:

  1. Describe the key issues and building blocks in modern optical communications systems;
  2. Describe optical transmitters and receivers, or transceivers, methods of modulating light wave carriers with digital data, and methods of demodulation.
  3. Describe the main factors limiting the data transmission speed and distance in optical fibre communication systems;
  4. Describe methods of overcoming above limitations to achieve higher data speed, longer transmission distances, and larger overall transmission capacities.
  5. Describe and specify an optical communications system.
  6. Outline future directions of technological developments in optical fibre communications.

Teaching details


Assessment Details

Exam, 2 hours, 100% (All ILOs)

Reading and References

  • Gowar, J., Optical Communications Systems, 2nd edition, Prentice Hall, 1993, ISBN:0-1363-8727-6 (TK 5103.59 GOW)