الفهرس 
CHAPTER 1: INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The direct modulation characteristics of high-speed 1.55μm MQW semiconductor lasers were modeled and simulated in both cases of oscillations in single longitudinal mode and multimode. In the case of single-mode oscillation, the laser characteristics were investigated under both small-signal analog modulation and digital modulation. The small-signal modulation parameters included the small-signal response and the modulation bandwidth, while those of the digital modulation include the eye diagram and its vertical opening (or the on-off ratio). The small-signal modulation bandwidth was estimated not only by the analytical small-signal approximation but also by integrating the rate equations under small-signal sinusoidal modulation. Then the simulated results were used to introduce a new assessment of the tolerance of the small-signal approximation. Also, the study focused on predicting the modulation conditions required to achieve a modulation speed of 40 Gb/s. In addition and for the first time, correlation between the calculated modulation bandwidth and the maximum bit rate of the laser was presented as a function of the bias current and the modulation index.
In the case of laser oscillating in multi-longitudinal modes, the intensity modulation performance of the multimode MQW semiconductor was investigated. The single-mode model of high-speed laser dynamics was extended to the case of multimode oscillations and one-to-one correspondence was made between the induced laser dynamics and the modulation characteristics of the laser. The multimode model includes self-and cross-modal gain suppression mechanisms. The mode intensities were characterized in the time domain to demonstrate the mode coupling in both cases of with and without modulation. The impact of the injection current (or AGS strength) on the dynamics of the non-modulated case was explored, while the impact of the modulation parameters on the laser dynamics was examined. The small-signal modulation response of the laser was simulated and the associated bandwidth was calculated as functions of the bias current. The modulation responses of the strongest oscillating modes were compared with those of the total output. In addition, a single-mode version of the multimode model was used to predict the modulation response and bandwidth to assess the degree of tolerance of using this simpler single-mode model.
Finally, the present results were applied to design a point-to-point digital fiber link with speeds as high as 10, 20, 30, and 40-Gb/s utilizing the investigated single-mode MQW laser. The modulating current signal was assumed with a pseudorandom NRZ bit scheme. The link comprised a standard single-mode fiber and a PIN photodiode. The link performance was quantified in terms of BER exceeding 10-9. The upper limits of the fiber length set by the fiber attenuation and dispersion were assessed. The possibility of improving the fiber system performance by using dispersion-compensating fibers is examined by studying its impact to increase the limited length of the optical fiber.