Learning objectives
At the end of the course the students will gain knowledge on light propagation in waveguides and optical fibers, and on the working principles of the main photonic components used in communication systems (lasers, modulators, couplers, amplifiers). Moreover, the students will be able to:
− analyze and describe a communication system based on optical fibers;
− analyze the properties of waveguides and optical fibers, and of the main photonic devices with simulations based on a numerical method;
− summarize and describe the main results of a numerical analysis, using a proper technical vocabulary;
− understand the technical specifications of optical fibers and photonic components, in order to properly use them in a laboratory setup;
− summarize and describe the main results of an experimental activity in laboratory.
Prerequisites
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Course unit content
The course provides the theoretical bases to study light propagation in waveguides and optical fibers, and the working principles of photonic devices used in communication systems. Conventional optical fibers are thoroughly described, with particular emphasis on the characteristics that make them suitable for optical communications. The main optical components and photonic devices used in modern communication systems, such as lasers, modulators, couplers and amplifiers, are presented in detail. Special attention is paid to the main research topics in the field of photonics for optical communications.
Some lessons of the course will be devoted to numerical simulations and to experimental activities in laboratory.
Full programme
Each class corresponds to 2 hours
CLASS 1: Main properties of light and of electromagnetic spectrum, with focus on modern photonic technologies
CLASS 2: Dielectric slab waveguide: TE and TM modes, plane waves, guided modes
CLASS 3: Dielectric slab waveguide: guided mode cut-off condition, field confinement,dispersion curve
CLASS 4: Dielectric integrated optics waveguides: different types (buried, strip-loaded, ridge, rib) and guided mode field distribution
CLASS 5: Standard optical fibers: geometry, materials, fabrication process, guiding mechanism, numerical aperture, single-mode regime
CLASS 6: Standard optical fibers: attenuation (absorption, scattering, micro and macro bending), single-mode and multi-mode fibers
CLASS 7: Guided modes in standard optical fibers: hybrid, TE and TM mode, dispersion curve
CLASS 8: Guided modes in standard optical fibers: weakly guiding approximation and pseudo-modes LP
CLASS 9: Dispersion in optical fibers: intermodal and intramodal dispersion, chromatic dispersion (material, guidance, polarization)
CLASS 10: Optical fibers for submarine communications
CLASS 11: Hollow-core fibers: different categories and guiding mechanisms, photonic crystals and their properties
CLASS 12: Optical fibers for Space-Division Multiplexing (SDM): multicore and few-mode fibers
CLASS 13: Power dividers and couplers: Y junction, directional coupler
CLASS 14: Power dividers and couplers: 3 dB coupler, multiplexer and demultiplexer
CLASS 15: Filters and interferometers: Fabry-Perot filter, multimodal interferometer (MMI)
CLASS 16: Filters and interferometers: Mach-Zehnder interferometer, arrayed-waveguide grating (AWG)
CLASS 17: Optical modulators: lithium niobate modulators, electro-absorption modulators
CLASS 18: Optical amplifiers: energy levels and photons, interaction electromagnetic waves-matter, main parameters
CLASS 19: Erbium-doped optical fiber amplifiers (EDFAs): main component, pumping schemes,
CLASS 20: Erbium-doped optical fiber amplifiers (EDFAs): propagation and population rate equations, optimum length, noise figure
CLASS 21: Laser working principle: Bohr's atom model, stimulated emission, resonant cavity, longitudinal and transversal modes
CLASS 22: Gas lasers and semiconductor lasers: III-V semiconductors for photonic devices, emission mechanism
CLASS 23: Solid state lasers and fiber lasers: scheme, pumping scheme, double-ckadding active fibers for high power lasers
CLASS 24: Photodetectors: thermal detectors and photon detectors based on the external (photoemissive devices) and internal (semiconductor devices: photoconductors, junction photodiodes) photoelectric effect
CLASS 25: Spectrum-based sensori: Fiber Bragg Gratings (FBGs)
CLASS 26: Insights on fiber laser and amplifier design
Numerical simulation activities:
CLASS 1: Introduction to numerical simulations of optical fibers and photonic devices
CLASS 2: Calculation of the guided modes in a dielectric slab waveguides and in silicon waveguides
CLASS 3: Calculation of the guided modes in a step-index fiber and of theie dispersion curve
CLASS 4: Calculation of the chromatic dispersion of the fundamental mode in an optical fiber
CLASS 5: Numerical analysis of the effective area and overlap integral, of guided modes in an optical fiber with Perfectly Matched Layers as boundary conditions
CLASS 6: Calculation of the guided modes in an anti-resonant hollow-core fiber and in a solid-core photonic crystal fiber
Experimental activities in laboratory and seminars:
CLASS 1: Introduction to laboratory activities with optical fibers: fiber end cut, splice, connectors,, instruments (tunable laser, optical spectrum analyzer, etc)
CLASS 2: Realization of simple experimental setups with optical fibers (i.e., attenuation measurement, sensing measurements with Bragg gratings)
2 seminars will be organized to celebrate the International Day of Light.
Bibliography
S. Selleri, L. Vincetti, A. Cucinotta, “Optical and Photonic Components”, Esculapio, 2015
B. E. A. Saleh, M. C. Teich, “Fundamentals of Photonics”, 3 rd Edition, Wiley, 2019
K. Okamoto, “Fundamentals of Optical Waveguides”, 3rd Edition, Academic Press, 2021
Scientific papers suggested during the lessons of the course.
Teaching methods
The teaching activities include lessons carried out using multimedia presentations, videos/images and web pages (52 hours). In addition, seminars (4 hours) and practice lessons are planned, with experimental activities in laboratory (4 hours) and numerical simulations carried out using COMSOL Multiphysics, a software for the analysis of the electromagnetic wave propagation at optical frequencies in linear and non-linear optical media (12 hours).
The slides of the presentations shown during the lessons are uploaded to the Elly web site of the course. The registration to the course is necessary to download the slides. Please notice that the presentations are considered an essential part of the teaching material.
Students who are not attending to the course should periodically check the teaching material and the information provided by the instructor on the Elly web site.
Further information about the lessons will be provided just before the beginning of the course.
Assessment methods and criteria
The learning assessment is made with:
− an oral exam with questions on the topics developed during the lectures, with the aim to verify the learning level of the student. The oral exam is evaluated in the range 0/30;
− an individual report on a numerical simulation activity carried on with COMSOL Multiphysics, used during the practice lessons. This individual activity concerns one of the kind of photonic devices or optical fibers presented during the laboratory lessons. Students can collect the text describing the activity during the final part of the course, or later by appointment with the professor. A Word template in .docx is available on the Elly web-site of the course. Students are encouraged to use it to prepare the report. The .pdf file of the report must be sent by email to the professor no later than three days before the date of the oral exam. The report is evaluated according to accuracy, completeness and clarity, in the range 0/30.
The mark of the oral exam is communicated to the student at the end of the oral test. The mark of the report is announced to the student just after the end of the oral exam. At the same time, the student can view the report with the corrections. The final mark is calculated as the average of the ones obtained for the oral exam and the report, which are both in the range 0/30. The honors are given to the students who obtain the maximum score for both the oral exam and the report.
The online registration to the exam is mandatory and it is possible until three days before the exam date.
Further information about the examination procedure will be given to the students during the lessons and made available on the Elly web-site of the course.
Other information
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