Single-Course English 5 ECTS

Introduction to Fibre Optic Communications

Overall Course Objectives

To give students insight into the basic principles of point-to-point optical communication systems, the backbone of the Internet. The students will become familiar with: a) optical hardware such as transmitters (lasers and modulators), receivers, optical fibres, optical filters, optical amplifiers, b) simulation software to evaluate these systems, and c) simple digital signal processing software for coherent communication systems.

Learning Objectives

  • Formulate the basic propagation equation in an optical fibre including chromatic dispersion and attenuation.
  • Evaluate the impact of dispersion and describe how dispersion can be compensated using dispersion compensating fibre.
  • Explain how an optical transmitter (TX) and a receiver (RX) work, and how one can characterise the performance by bit error rate (BER); use datasheets for TX and RX to calculate how they impact the overall system performance.
  • Argue how an Erbium-doped fibre amplifier (EDFA) introduces gain and explain how amplified spontaneous emission (ASE) is encapsulated in the noise figure parameter.
  • Describe Wavelength-Division Multiplexing (WDM) systems and their key components; calculate crosstalk for different filter parameters and channel spacings; Describe how wavelength dependence of components such as EDFAs, TXs, RXs impact the total performance.
  • Argue how Quadrature Amplitude Modulation (QAM) differs from the simple on-off keying modulation; describe differences in transmitter and receiver equipment.
  • Compare the BER performance of an on-off keying system with a QAM system and argue pros and cons for the different modulation formats
  • Explain how Digital Signal Processing (DSP) is used to compensate for dispersion and phase noise; outline how the algorithms work.

Course Content

Optical fibre: structure, principle of light guiding, attenuation, material and waveguide dispersion, basic pulse propagation equation.
Laser: semiconductor physics, pn-junction, laser operation, rate equations, direct modulation.
Modulator: amplitude and phase modulators, nested modulators.
Photodiode: detection of optical signals, noise contributions.
Optical amplifier: EDFA structure and operation, gain characterisation, ASE, noise figure, Raman amplifier.
WDM: principle, ITU-grid, filter implementations, crosstalk, impact of wavelength dependent components.
Coherent modulation: TX and RX implementation, QAM modulation, BER performance.
Digital Signal Processing: dispersion and phase noise compensation, algorithm structure and implementation.

Recommended prerequisites

Teaching Method

Lectures, simulation exercises, one graded report with oral defense, self-assessment tests



This course is to some extent the theoretical counterpart of the experimental optical communication system course 34126 and 34129; the courses complement each other.

See course in the course database.





13 weeks




DTU Lyngby Campus

Course code 34121
Course type Bachelor
Semester start Week 5
Semester end Week 19
Days Fri 8-12

7.500,00 DKK