In the last few years, erbium-doped fiber amplifiers (EDFAs) have been investigated extensively both for their superior amplification characteristics and their applicability to future optical fiber communication systems. In the preamplifier configuration, a bandpass filter is required to reduce the amplified spontaneous emission (ASE) noise in order to provide satisfactory bit error ratios (BER). In this thesis we examine the influence of the filter characteristics on performance. A model is derived to predict the BER performance of a pre-amplified APD receiver. The model is shown to be consistent with the experiments conducted at 2.5 Gb/s and data collected for various bandwidths and signal levels. The model is also compared with a recently published model, and the results show a good match. If the bandpass filter (BPF) has a small bandwidth and the laser center wavelength varies, the filter will attenuate the signal and introduce power penalties. The tradeoff between the stability of the system and the BER performance is presented, including experimental results for various bandwidths and offsets. It is shown that for optimal performance, a filter with a bandwidth about four times the expected variation in center wavelength should be used. / Master of Science

Subcarrier multiplexing (SCM) on lightwave systems is an important technique for the near term implementation of broadband services by both telecommunication and cable TV companies. With advance in opto-electronics technology in the mid-1980s, lightwave SCM systems can now be practically implemented to provide a carrier platform for both digital and analog signals and (for short distance applications) are presently more cost effective than time division multiplexed systems. AM SCM systems are particularly attractive for multichannel video signal transmission due to their compatibility with the National Television Systems Committee Amplitude Modulated Vestigial Sideband (NTSC AM-VSB) TV format. However, AM SCM systems are generally recognized to have a limited system capacity due to large carrier-to-noise ratio (CNR) and low nonlinear distortion requirements. This research dissertation contains a comprehensive study of the system capacity of such systems based on theoretical analysis, experiment, and simulation. The practical performance of lightwave AM SCM systems are limited by the laser diode threshold-nonlinearity and laser relative intensity noise, the photodiode shot noise, and the receiver thermal noise. The practical system performance is evaluated and compared with that of the theoretical performance limit. The analysis indicates that AM SCM systems have sufficient system capacity for typical CATV loop distribution and supertrunking systems. It is shown that previous reported limits are generally overly conservative. A sensitivity analysis identifies the critical performance limiting parameters and provides system designers with achievable system performance as device characteristics improve. For 1550 nm AM SCM systems employing erbium-doped fiber amplifiers (EDFA) operating on the 1300 nm single-mode-fiber of telephone networks, there are additional sources of nonlinear distortion and noise to be considered. The nonlinear distortion produced by laser-chirp and fiber-induced-dispersion and the noise produced by the EDFA can significantly degrade the system performance. The analysis shows that the maximum link distance is limited by the composite-second-order (CSO) distortion, and the maximum number of subscribers is limited by the EDFA excess fluctuation noise. / Ph. D.

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Includes bibliographical references. / by David Michael Papurt. / Ph.D.

One of the obstacles to coherent fiber-optic communications is the unpredictable polarization drift which necessitates the use of an active polarization controlling system to match the polarizations of the signal and local oscillator. The polarization match must be maintained during the reset of any of the finite range components to prevent loss of data. We present a novel and practical system which uses three liquid crystal devices for the polarization matching process. Also, the required reset control algorithm and its derivation are described in detail.

Also issued as a Sc.D. thesis in the Dept. of Electrical Engineering, 1969. / Bibliography: p.105.

Based on a Ph.D. thesis in the Dept. of Electrical Engineering, 1970. / Bibliography: p. 122-123.

Also issued as a Ph.D. thesis in the Dept. of Electrical Engineering, 1969. / Bibliography: p.113-117.

Based on a Sc.D. thesis in the Dept. of Electrical Engineering, 1969. / Bibliography: p.112-113.

Thesis (M.S.)--Naval Postgraduate School, 2004. / Title from title screen (viewed Aug. 13, 2004). "March 2004." Includes bibliographical references (p. 71-73). Also issued in paper format.