Abstract:

The United Nations “International year of light 2015” strives to highlight the importance of optical technologies in our everyday lives [1]. Fiber optic communication is one such technology: the growth of internet and its associated services, including e-commerce, video streaming and social networks, are enabled by the vast transmission bandwidth provided by optical networks. However, the general public is not well aware of the optical and electronic fundamentals of the underlying transmission systems. Here we present the development of a bachelor thesis in Telecommunication Engineering in which a small-scale fiber-optic link is built and the electronics required to transmit music over this link are implemented. The resulting system demonstrates, in a very intuitive way, how information is transmitted over an optical fiber.

The student was first tasked with designing and building the small scale fiber-optic link, consisting of a light emitting diode, lens, multimode fiber and photodetector. To constrain the design problem the specific elements were chosen in advance by the supervisor. The student had to apply knowledge acquired throughout his degree to calculate how the elements should operate and estimate the power transmitted through the system. An experimental phase followed, in which the student built the optical system in several steps, verifying, correcting and critically judging the accuracy and approximations in the previously carried out calculations. The conclusion of this phase was a system that demonstrates light transmission through an optical fiber.

In order to illustrate the transmission of information over this system, two approaches were explored. The first and more basic approach was to switch the light source on and off, thereby transmitting binary information (0 and 1). A more compelling albeit more complex approach was designing electric circuitry to modulate the transmitted light with an audio signal, and play the received signal on a speaker. The supervisor provided basic schematics for the electric circuits, which were then designed and implemented by the student. This phase was completed with a series of test ensuring the correct transmission of music through the complete system.

The system has so far been used successfully in two “open-door” events for future students of our University, both to illustrate optical communications and as a practical example of the skills that a telecommunication engineer acquires. Our university has furthermore proposed the project for presentation at the 2015 Researchers’ Night in Brussels.

From an educational perspective we believe that this particular project offers several key benefits. First, building a fully functional, practical system provides a strong motivation for both the student and the supervisor. Second, the “project-based” approach, where the supervisor provides clear goals and basic guidelines, fosters the student’s independence and problem-solving skills. Third, as any hard-ware development, numerous complications can (and probably will) arise; however the continuous interplay between design, implementation and testing provides a strong feedback, so that errors can be detected at an early stage. Given the overall success a follow-up project has been proposed for the next academic year.

This work was supported by the Universidad de Málaga, under project PIE13-120 and the Campus de Excelencia Internacional Andalucía Tech.

[1] www.light2015.org

Keywords:

Bachelor thesis, demonstration, optical communications.