The Study Of High-speed Digital Optical Fiber Transmission Using Sub-carrier Multiplexing

The study of optical pulse propagation in optical fibers is interesting from both fundamental and applied perspectives. Understanding the physics behind the processes that determine the evolution of optical pulse in single-mode fibers is essential for the design and performance analysis of optical fiber communication systems. Based on the understanding, the performance of high-speed optical fiber transmission using sub-carrier multiplexing is investigated deeply. A significant advantage of SCM is that microwave devices are more mature than optical devices; the stability of a microwave oscillator and the frequency selectivity of a microwave filter are much better than their optical counterparts. In addition, the low phase noise of RF oscillators makes coherent detection in the RF domain easier than optical coherent detection.In order to reduce the impact of fiber chromatic dispersion and nonlinear interference on SCM/WDM systems, a kind of facile carrier-suppressed optical single-side-band(SSB) modulation is used. Optical SSB modulation at the transmitter is employed to significantly decrease dispersion penalty and increase the optical bandwidth efficiency. Optical carrier suppression(CS) is applied to increase the modulation efficiency which can suppress nonlinear effect in optical fiber and eliminate intermodulation distortion which comes from nonlinear modulation characteristic of optoelectronic modulators simultaneously. A 10Gbit/s SCM test bed has been set up and the performance is investigated.The details are described as follows:1. Explore the formation mechanism and characteristic of group velocity dispersion(GVD) in single mode fiber from classical electromagnetism theory. The relations between GVD,bit rate and distance are presented. The optical pulse's evolution equation-Nonlinear Schrodinger Equation(NLSE) under the influence of GVD, SPM and loss is educed from Maxwell's equations with the introduction of non-linear constitutive relation. Then nonlinear pulse propagation in optical fibers is investigated through analyzing corresponding NLSE.2. Analyze nonlinear pulse propagation in optical fibers using joint time-frequency (TF) representation. The TF representation is demonstrated to be an extremely powerful tool for investigating pulse propagation dynamics in optical fibers, providing a clearer and deeper insight into the physical phenomena that determine the behavior of these systems.3. The performance of high-speed digital fiber-optic transmission using subcarrier multiplexing (SCM) is investigated. For SCM/WDM system, the nonlinear interference between subcarrier channels is severe because the channel spacing is very narrow, nonlinear crosstalk must be considered.4. In order to reduce the impact of fiber chromatic dispersion and nonlinear interference on SCM/WDM systems, a kind of facile carrier-suppressed optical single-side-band(SSB) modulation is used. Optical SSB modulation at the transmitter is employed to significantly decrease dispersion penalty and increase the optical bandwidth efficiency. Optical carrier suppression(CS) is applied to increase the modulation efficiency which can suppress nonlinear effect in optical fibers and eliminate intermodulation distortion which comes from nonlinear modulation characteristic of optoelectronic modulators.5. In order to optimize the system performance, tradeoffs have been made between data rate per subcarrier, levels of modulation, channel spacing between subcarriers, optical power, and modulation indexes. A 10 Gbit/s SCM test bed has been set up and the performance is investigated. The measured results agree well with the analytical prediction.6. Preview the system configurations of 40 Gbit/s digital optical transmission using SCM. The performance is investigated analytically. GVD,PMD,XPM,FWM on SCM/WDM systems are analyzed carefully and tradeoffs have been made between them.