Douglas Walsh

Photonics laboratory experiments for modern technology-based courses

The modern photonics and optical communications industries have placed ever increasing demands on the supply of skilled graduates who are competent in the design, installation and operation of photonics systems. In response to this demand, we have developed a range of photonics laboratory teaching experiments to support accompanying lecture courses by underpinning fundamental principles with hands-on experimental experience. These systems enable students and trainees to investigate experimentally the basic principles, characteristics, and design of optical waveguides, optical communications systems, optical amplifiers and fault location techniques for optical networks, with additional scope for open-ended investigation of real technical issues such as mode spectrum analysis in optical waveguide and optical pulse dispersion/bit rate limits in fiber communications systems. The educational and overall system design philosophies, hardware,and experiments are reported in this paper.

SIMULTANEOUS RECOVERY OF STRAIN AND TEMPERATURE FIELDS BY THE USE OF TWO-MODED POLARIMETRY WITH AN IN-LINE MODE SPLITTER/ANALYZER

We report the simultaneous recovery of temperature and strain through measurement of polarization changes in the LP(01) and LP(11) modes of Andrew Corporation elliptical-core fiber. This technique required the development of an in-line mode splittery/analyzer, which is also described. The scheme has been demonstrated to be sensitive to changes of 1 degrees C and 5 microepsilon and is compatible with white-light multiplexing methods to provide quasidistributed information.

In-line mode splitter applied to a dual polarimeter in elliptical core fibre

Many attempts have been made to use optical fibres to measure strain or temperature. However, since fibres are sensitive to both strain and temperature, practical strain measurements require that the effects of temperature are simultaneously measured or compensated for. This necessitates the measurement of two parameters which respond differently to changes in strain and temperature, a condition which may be met using fibres operating in the dual mode regime.

Photonics laboratory teaching experiments for scientists and engineers

In response to industrys need for scientists and engineers skilled in the design, manufacture and operation of photonics systems, Strathclyde University and OptoSci Ltd. have developed a suite of Photonics Educator Kits, which enable students to experimentally investigate all of the major technical features, principles and design issues of optical waveguides, optical communications systems, erbium doped fiber amplifiers and lasers. To support these applications experiments we have recently added a range of kits enabling students to experimentally investigate the basics of physical optics covering reflection, refraction, polarization, diffraction, coherence and interference. In this paper, we will describe the educational objectives and the design philosophies behind the development of these kits. To illustrate these, full details of the experimental procedures, the results and the benefits to the student will be discussed for the recently upgraded optical communications kit and the erbium doped fiber amplifier (EDFA) system, in particular addressing the crucially important noise characteristics of optical amplifiers.

Student laboratory experiments on erbium-doped fiber amplifiers and lasers

The Erbium Doped Fiber Amplifier (EDFA) has now replaced optoelectronic repeaters as the primary design option for extending the range and capacity of the Worlds fiber optic telecommunication systems. In a broader sense, optical amplifiers are the basis of all lasers. It is therefore essential that students of science and engineering have a broad appreciation of, and practical familiarity with, optical amplifiers in general, EDFAs in particular and their applications in lasers. To achieve these objectives, Strathclyde University in collaboration with OPTOSCI LTD. have developed an EDFA/Laser educator kit which enables students to experimentally investigate the gain and noise characteristics of an EDFA, including issues such as signal and pump saturation, gain efficiency, amplified spontaneous emission and optical beat noise. With a simple extension to the basic amplifier kit the students are able to construct an erbium doped fiber ring lasers and to investigate its power characteristics (threshold and slope efficiency) as a function of output coupling ratio and intra-cavity loss. The experimental objectives, design philosophies, hardware, experimental procedures and results will be examined in detail in this paper.

Microwave subcarrier optical fiber strain sensor

At present, there is an acute need for techniques in monitoring civil engineering structures, and optical fiber sensors are acknowledged to be amongst the best candidates. For more than ten years, interferometric optical fiber sensors have been widely investigated and now provide a rich extended basis for measuring strains experienced by structural elements. However, because of their periodic response, those sensors need extending measuring techniques to fulfill civil engineering requirements. Amongst different methods, Thomson-CSF and the University of Strathclyde have recently employed a microwave subcarrier system [1]. A specific sensor dedication to the arena of large civil engineering structures has been designed and tested.

Practical bit error rate measurements on fibre optic communications links in student teaching laboratories

In this paper we describe the principles and design of a fibre optic communications teaching package and a cost effective extension module to this kit which enables students to investigate the effects of noise, attenuation and dispersion on the bit error rate at the receiver of laser and LED based digital fibre optic communication systems.

Practical Introduction to Optical WDM Components and Systems in Student Teaching Laboratories

In this paper we describe a new family of teaching packages designed to offer a practical introduction for graduate students of Science and Engineering to the topic of wavelength division multiplexing (WDM) in fibre optics. The teaching packages described here provide students with the background theory before embarking on a series of practical experiments to demonstrate the operation and characterisation of WDM components and systems. The packages are designed in a modular format to allow the user to develop from the fundamentals of fibre optical components through to the concepts of WDM and dense WDM (DWDM) systems and onto advanced topics covering aspects of Bragg gratings. This paper examines the educational objectives, background theory, and typical results for these educational packages.

Student laboratory experiments exploring optical fibre communication systems, eye diagrams and bit error rates

Optical fibre communications has proved to be one of the key application areas, which created, and ultimately propelled the global growth of the photonics industry over the last twenty years. Consequently the teaching of the principles of optical fibre communications has become integral to many university courses covering photonics technology. However to reinforce the fundamental principles and key technical issues students examine in their lecture courses and to develop their experimental skills, it is critical that the students also obtain hands-on practical experience of photonics components, instruments and systems in an associated teaching laboratory. In recognition of this need OptoSci, in collaboration with university academics, commercially developed a fibre optic communications based educational package (ED-COM). This educator kit enables students to; investigate the characteristics of the individual communications system components (sources, transmitters, fibre, receiver), examine and interpret the overall system performance limitations imposed by attenuation and dispersion, conduct system design and performance analysis. To further enhance the experimental programme examined in the fibre optic communications kit, an extension module to ED-COM has recently been introduced examining one of the most significant performance parameters of digital communications systems, the bit error rate (BER). This add-on module, BER(COM), enables students to generate, evaluate and investigate signal quality trends by examining eye patterns, and explore the bit-rate limitations imposed on communication systems by noise, attenuation and dispersion. This paper will examine the educational objectives, background theory, and typical results for these educator kits, with particular emphasis on BER(COM).

OptoSci educator kits: an immediate solution to photonics teaching laboratories

The burgeoning growth of the worldwide photonics and optical communications industry has imposed ever increasing demands on the supply of suitably skilled engineers and scientists who can design, install and operate modern photonics systems. In recognition of this need OptoSci, in collaboration with university academics, has commercially developed a series of hardware based teaching packages in optics, optoelectronics and optical communications. Each educator kit is fully self-contained, including all of the optoelectronic hardware and comprehensive literature support. This saves the academic tutor considerable development time and enables the kits to be immediately installed in the photonics teaching laboratory to support accompanying lecture courses. A fundamental design objective of our educator kits is to provide students with hands-on practical experience of photonics components, instruments and systems and allow them to investigate essential physical principles and key technical issues relevant to their lecture courses. This paper will outline the design philosophy behind the products to meet the desired educational aims, and then examine the specific educational objectives and topics investigated in each educator kit.