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Final Examination of Xiaoxu Li for the degree of Doctor of Philosophy in Optics
Tuesday, November 03, 2009 1:00 PM to 3:00 PM CREOL Room 102
Dissertation title: WAVELENGTH-DIVISION-MULTIPLEXED TRANSMISSION USING SEMICONDUCTOR OPTICAL AMPLIFIERS AND ELECTRONIC IMPAIRMENTS COMPENSATION Abstract:Wavelength division multiplexing (WDM) technology has been widely used in fiber-optic systems. Among optical amplifiers for WDM transmission, semiconductor optical amplifier (SOA) is a promising candidate due to its broad bandwidth, compact size, and low cost. Due to relatively large noise figures of SOAs, high input powers are required to ensure reasonable optical signal-to-noise ratio after amplification. High input powers, however, force SOAs to operate in the saturated region. As a result, amplified signals suffer from SOA nonlinearity impairments including self-gain modulation (SGM) effect, self-phase modulation (SPM) effect, and inter-channel crosstalk effects such as cross-gain modulation (XGM), cross-phase modulation (XPM), and four-wave mixing (FWM).
In order to increase the reach of such WDM systems, SOA impairments must be compensated. In this dissertation, an electronic post-compensation scheme for SOA impairments is proposed using coherent detection and digital signal processing (DSP) techniques. To do so, a model for quantum-dot (QD) SOA amplification that can accurately predict the nonlinear impairments was developed. An on-off keying transmission over 100 km SSMF and three SOAs at 1.3 ?m was demonstrated experimentally with SOA impairment compensation (IC) and direct detection. The data pattern effect of the signal was compensated effectively. Both optimum launching power and Q-factor were improved by 8 dB.
For advanced modulation formats involve phase modulation or in transmission windows with large dispersion, coherent detection must be used and fiber impairments in the WDM systems need to be compensated as well. The proposed fiber impairment compensation is based on digital backward propagation. The corresponding DSP implementation is described and the required calculations as well as system latency are derived. Joint fiber and SOA IC was experimentally demonstrated for an amplitude-phase-shift keying (APSK) transmission.
MAJOR: Optics
EDUCATIONAL CAREER:
COMMITTEE IN CHARGE:
Approved for distribution by Guifang Li, Committee Chair, on Tuesday, October 22, 2009.
The public is welcome to attend.
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