Theoretical And Experimental Research Of Dynamical Chromatic Dispersion Compensation In High-bit-rate Optical Fiber Communication Systems

The tolerable chromatic dispersion (CD) for a very high-bit-rate transmission system (40Gbit/s or above) is very low. And even after the long distance static CD compensation, the BER of the communication system will increase due to the time-varying residual CD caused by factors like network reconfigurations, temperature fluctuation, laser's wavelength drift and periodic repair/maintenance of fiber etc. Therefore the technology of dynamical CD compensation comes to be critical to the performance of very high-bit-rate transmission systems.In this dissertation, several reported tunable CD compensation and monitoring technologies are generalized and the needs for dynamical CD compensation of high-bit-rate transmission system are concluded. Theoretically, the transmission of Gaussian pulses in a CD media is analyzed including the influence caused by the initial chirp, laser line-width, and nonlinear effects. The influence of CD on the bit rate and bandwidth is also studied. A dynamical CD compensation sub-systems in 40Gbit/s RZ systems is established, which includes a tunable CD compensation module using DCFs cascaded with optical switch array, a CD monitoring module that based on narrow-band electrical power detecting and achieved by using devices such as microwave amplifiers, microwave filter and power detector, a controlling module with digital signal processor (DSP), and a controlling algorithm developed with adaptive searching. Tunable CD compensation method in 40Gbit/s systems based on the SPM and XPM effect of SOA is proposed and analyzed theoretically. A SOA based tunable CD compensation system is established in a 10Gbit/s system, which realized consecutive and small range tunable CD compensation.Major innovations of this dissertation:1. A cost-effective and simple CD monitoring method based on narrow-band electrical power detecting is proposed. A theoretical model is proposed and discussed focusing on the relationship between electrical power and CD at different frequency bands. The effects of factors such as modulation format, bandwidth and center frequency of microwave filter to the performance of this method are investigated. The detectable CD of 130ps/nm and resolution of 5.2ps/nm/dB are obtained experimentally within a frequency band centered at 12GHz in a 40Gbit/s system. 2. A dynamical CD compensation system is established based on DCFs cascaded with optical switch arrays and the electrical power detecting CD monitoring technique. The compensation range and resolution reaches 82ps/nm and 5ps/nm respectively. The maximal response time of the system is 0.52s.3. A consecutive tunable CD compensation method is proposed based on the XPM effect of SOA. The effects of tunable variable such as SOA inject current, optical power of clock pulse sequences and time delay between clock and signal sequences to CD compensation are analyzed theoretically and validated experimentally. The compensation range of 40ps/nm is indicated theoretically in 40Gbit/s systems.4. The 10Gbit/s consecutive tunable CD compensation based on SOA and DCF is tested,. A compensation range of -40 ~ 60ps/nm is achieved by using a serious chirped laser.