Effect of pre-chirped pulses in WDM optical communication systems and application of multi-state transmitted
| Autor: | Ko-Yuan Hsiung, 熊克原 |
|---|---|
| Rok vydání: | 2002 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 90 The applications of pre-chirped pulse on high-speed and ultralong distance WDM optical communication system with dispersion management are studied. Pre-chirping technique can be applied to compensate for fiber dispersion for the system of several hundreds of kilometers. For the system of several thousands of kilometers, pre-chirping is not able to compensate for fiber dispersion but enhance pulse broadening in stead. Utilizing this phenomena, we can reduce the effect of fiber nonlinearities on signal because signal peak power is low owing to pulse broadening. The distorted pulse shape can be recovered with proper dispersion compensation at receiver if fiber nonlinearities are effectively reduced. First we consider a dispersion managed WDM system of 10 Gb/s and 7,500 km, in which fiber dispersion is compensated with dispersion compensation fiber with a period of 500 km and the signal format is chirped return-to-zero (CRZ). Dispersion compensation for every channel is incomplete. It is found that, recovered signal quality can be significantly improved with pre-chirping when incomplete dispersion compensation is high. For the channels with nearly dispersion compensation, pre-chirping does not improve their qualities. As pre-chirping broadens signal spectrum and reduces spectrum usage efficiency, we propose three-state signal format instead of conventional two-state (on/off) signal format so that transmitted information contents can be increased 50%. As higher signal power is required, the considered transmission distance is shortened to 3,000 km for maintaining high signal quality. It is also found that signal quality also can be significantly improved with pre-chirping for the channel of poor dispersion compensation. Therefore, signal qualities with the proposed three-state format are also high for the considered CRZ WDM system when proper pre-chirping is used. The optimal powers of signal states are also studied. For the considered system, the optimal powers are 0.7mW and 1.96mW for middle power state and highest power state. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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