Classes in fiber-optic communications, presented at Arizona State University (ASU) for four decades, have evolved in both content and delivery. Content updates followed the development of new components and network strategies, while delivery methods changed from blackboard-to-television-to-Internet. Evolution, evaluation, and future direction of these classes are described.
In the last few years, there have been more and more College and University engineering courses appearing on the Web. Most of the instructors producing these Web courses have not only never done so before, they have not even taken or viewed a Web class before. Because of this, it is helpful to share as many details as possible about Web courses actually presented. This paper describes a Web course on fiber-optic communications presented to a class of 55 students at the senior/first-year-graduate level.
Personal computers and the Internet have revolutionized the modern classroom in several ways. Many classes are now taught in technology-enhanced classrooms where computers are available to aid the instructor's presentation. Availability of the Internet further increases the instructor's options by providing convenient access to an abundance of outside material and by providing an effective means of distance delivery. Applications of these technologies to courses in optical fiber communications are described.
This paper describes the development of numerical simulation models of an Er-doped waveguide laser and a mode-locked fiber soliton laser. The Er-doped waveguide laser model is a simple and straight-forward but powerful dynamic model using time domain algorithm. It is based on (1) time dependent rate equations of a quasi-two-level-system for the population densities and (2) time-dependent traveling wave equations for the pump and signal power which are solved simultaneously in time-domain. The dynamic responses of population densities, pump and signal power are investigated. The model is used to study more sophisticated structure with cross-coupling from optical feedback of an etched grating. Another simulation model is developed to investigate the generation of sub- picosecond solitons in an active mode-locked fiber ring laser which consists of a polarization preserving Er-doped single mode fiber, an amplitude modulator and a phase modulator and has taken into account of dispersive spreading, self-phase modulation, finite amplification bandwidth, pump depletion, and Raman self-frequency shift. A newly developed numerical technique, Fourier series analysis technique, is used to solve the non-liner Schrodinger equation of soliton propagation. Time trace of the soliton pulse propagation and its spectrum can be obtained under a wide range of operation conditions.
This paper presents a unique approach to the production and display of a hologram movie. Motion was provided by rotating a 3D object in steps between exposures. Strip holograms were made on 70 mm AGFA 8E75 Holotest roll film. Each hologram was about 11 mm high and 55 mm wide. The object was rotated two degrees, while the film was advanced, between successive exposures. A complete rotation of the object was recorded on 180 holograms using the lensless Fourier-transform construction. The ends of the developed film were spliced together to produce a continuous loop. Although the film moves continuously on playback and there is no shutter, there is no flicker or image displacement because of the Fourier-transform hologram construction. The movie can be viewed for as long a time as desired because the object motion is cyclical and the film is continuous. The film is wide enough such that comfortable viewing with both eyes is possible, enhancing the 3D experience. Viewers can stand comfortably away from the film since no viewing slit or aperture is necessary. Several people can view the movie at the same time. Speckle is reduced due to the film motion.
Multichannel local-area networks can be constructed using fiber-optic wavelength-division-multiplexing (WDM) techniques. In this paper, WDM is applied to ring networks such as FDDI, token ring, slotted ring, and buffer insertion ring architectures. Crosstalk and insertion loss analyses of grating demultiplexers shows that the ratio of channel separation to channel width must be greater than four. Performance analyses of the multichannel WDM ring are formulated to determine the packet delay. The delay in the multichannel token ring is obtained by summing the remaining service time, token walk time, and the average service time of newly arrived messages. The remaining service time is estimated by approximating the system as a M/M/m queue. The multichannel slotted ring and buffer insertion ring are modeled by a non-preemptive head-of-the-line priority queuing system. By identifying that portion of the passing ring traffic having priority over local traffic, the delay of a tagged packet can be obtained as the sum of the residual service time and service times of local waiting packets and newly arrived ring packets. Two implementations are identified, one with parallel optical transmitters and receivers and protocol modules, and another using an array of laser diodes and photodetectors and a single protocol module.
Wavelength division multiplexing (WDM) is a technique that enables several light sources operating at different wavelengths to simultaneously transmit through a single medium and has been widely used in fiber optics industry [1,21. One can apply the WDM technique to read several tracks of an optical disc in parallel so as to increase the data transfer rate. In section 2, the operating principles and associated design parameters of the WDM optical readout system are examined. The properties of laser diodes (LDs) that limit the number of wavelength channels to be multiplexed are the spectral spread of the diodes and -peak emission wavelength deviations. These factors affect the minimum channel spacing. The insertion loss and the adjacent channel crosstalk of the wavelength demultiplexer (DEMUX) in the WDM readout system are needed to be minimized. Dependence of both parameters on the spectral spread of the light sources and channel spacing are addressed in section 2.