High Pass Filter Characteristics Of Saturated QDSOA And Its Application In Optical Packet Switching

With the current development of optical communication network, the transmission rate of single wavelength channel is growing, which has brought great pressure on the network switching nodes. There are restrictions on the electronic bottleneck to further improve the switch rate. Optical packet switch is introduced to solve the problem. Optical label and payload processing in optical packet switching technology is a key technology, whitch has been extensively studied. Quantum dot semiconductor optical amplifier(QDSOA) is a type of semiconductor optical amplifier based on quantum dot structure. Compared with traditional SOA, QDSOA have shorter carrier recovery time, high saturated gain, low threshold current, and saturated QDSOA have high pass filter characteristic. QDSOA have great potential in high-speed optical communications and all-optical signal processing. The high pass filter characteristics of saturated QDSOA and its application in the optical packet switching are investigated in this dissertation. The main research works are listed as follows:(1) With the three-level electron transition rate equations and the traveling-wave equations in QDSOA, a segmented numerical model of the active region is established. Based on this model, the frequency response characteristics of saturated QDSOAs are obtained and the impacts of input optical power, injection current, the active region length, the maximum modal gain and the carrier transition time on the 3 dB cutoff frequency and suppression ratio are investigated. The results show that the saturated QDSOA has a high pass filter characteristic with large bandwidth and high 3 dB cutoff frequency. By optimizing the QDSOAs’ parameters, the more excellent properties can be obtained than the traditional buck or quantum well semiconductor optical amplifiers.(2) A novel scheme to erase optical label using a saturated quantum dot semiconductor optical amplifiers is proposed, which mainly utilizes the high pass filter characteristic, and two improved scheme are proposed. The first improved scheme by adding continuous-wave assistant light can reduce the pattern effect on the output payload signal. The second improved scheme by adding label-duration assistant light can improve label suppression ratio. The waveforms and eye diagrams of the packets after the label erasure are demonstrated. The impacts on suppression ratio are analyzed, including optical power, injection current and active region length. We give methods for parameter optimization.(3) Starting from the basic principle of QDSOA cross gain modulation, combined with the high pass filter characteristics of saturated QDSOA, we propose an novel scheme to realize the optical label and payload separation, and study the feasibility of this scheme. The waveforms and eye diagrams of the input/output pump light and probe light are demonstrated. The impacts on suppression ratio are analyzed, including probe light power, optical packet peak power and injection current. Then an improved scheme which add label-duration assistant light are proposed. The impacts on extinction ratio of output probe light are analyzed, including probe light power and optical packet peak power. Then the two schemes are compared.