Applications Of Pulse Position Modulation In Optical Label Switching Technology

Signal transmission and switching are two key technologies in the current optical fiber communication network. The huge bandwidth resources and the excellent transmission performances guarantee the high-speed and high-capacity signal transmission, but the electrical switching process is failing to catch up with the current development and is now becoming the technical bottleneck of communication network. Therefore transitional forms of switching between Optical Circuit Switching and Optical Packet Switching have emerged, such as Optical Burst Switching and Optical Label Switching. These forms combine the advantages of both electronic and photonic technology and manage the optical switching by electrical control.In this dissertation applications of Pulse Position Modulation (PPM) in Optical Label Switching (OLS) technology have been investigated. Several labeling methods employing orthogonal modulation are involved, including FSK/ASK, FSK/PPM, DPSK/PPM orthogonal modulation schemes. First the FSK/ASK scheme together with its Extinction Ratio (ER) problem are introduced and analyzed. Current researches are showing that the ER in a typical FSK/ASK system is limited to 6dB. Then the FSK/PPM simulation system is set up, and the ER value is shown to increase to 10dB without any signal corruption. The result presents the improvement to the current orthogonal modulation system brought by PPM format. In the mean while, a novel orthogonal DPSK/PPM optical labeling scheme is proposed, and is systematically analyzed by simulation. Investigations of Bit Error Rate (BER) versus received optical power are proving that with the high ER value of 18.5dB, successful receiving can be accomplished. At BER of 10-9 the power penalties of DSPK label and PPM payload for 60km fiber transmission are 2dB and 5dB respectively, and the fiber transmission span is composed of 50km Single Mode Fiber (SMF) and 10km Dispersion Compensation Fiber (DCF). Moreover, even by increasing the ER to 19dB, the received signals can still provide good eye opening and the power penalties are 3dB and 5dB, respectively. These outcomes clearly indicate the outstanding performance of combined orthogonally modulated optical labeling schemes using PPM technology, and thus revealing the potential and the fine prospects of PPM format in OLS applications.