Modulation Characteristics Of Reflective Quantum Dot Semiconductor Optical Amplifiers And Research On Its Application

With the high-speed development of Internet, the requirement for the high capacity of data service is increased. Whereas, the traditional single wavelength channel does not increasingly meet the large capacity communication demand. The appearing of WDM-PON solves the problem. In this proposal, each user occupies a single wavelength channel. Based on this mode, it not only improves the safety performance, but also provides larger communication bandwidth for each user. Thus, it can meet the needs of growing large capacity of data service. However, the cost is the primary factor which restricts the development of WDM-PON. While the emergence of colorless ONU technology will largely save the cost of optical access network. The re-modulation technology based on the reflective quantum dot semiconductor optical amplifier (RQDSOA) is investigated in this dissertation. Compared with the traditional bulk and quantum well semiconductor optical amplifier, quantum dot semiconductor optical amplifier has the characteristics of short gain recovery time, high saturated gain and large modulation bandwidth. Therefore, the application of RQDSOA in re-modulation technology has great potential. The main research works are listed as follows:(1) The modulation characteristics of RQDSOA are studied by using the RQDSOA numerical model. The impacts of input optical power, the length of active region and the maximum modal gain on G-I characteristic are obtained. Based on these results, it can determine the linear modulation range of current. And then, the influence of input optical power, the length of active region, the maximum modal gain and the carrier transition time on the modulation bandwidth are obtained, it is observed that the modulation bandwidth of RQDSOA exceeds 10GHz and this result is much better than the traditional RSOA. The linearity of RQDSOA is also studied, the influence of the bias current and the modulation index on the harmonic distortion are achieved.(2) The high-pass characteristics of RQDSOA are studied by using the RQDSOA numerical model. The RQDSOA has the high-pass characteristics only if its gain saturated. Therefore, the characteristics of gain-saturation is investigated with the impact factors such as injection current, optical input power, active region length, and maximum modal gain. Consider the fact that high-pass characteristics is utilized to filter downstream signals in the RQDSOA re-modulation scheme, the impacts of optical input power, injection current, active region length, and maximal mode gain on the 3dB cut-off frequency of high-pass response are investigated. According to the simulation results, the 3dB cut-off frequency of high-pass response can reach 3-10GHz.(3) The application of RQDSOA on re-modulation scheme is proposed. In this proposal, the influence of the upstream signal data rate on the bit error rate is obtained. Moreover, it is confirmed that the RQDSOA can directly modulate the lOGbit/s upstream signal and the bit error rate of the system reaches 10"13. In order to investigate the impacts of the residual downstream signal on the re-modulated upstream signal, the influence of the downstream signal data rate and its extinction ratio on the bit error rate are achieved. The results represent that the bit error rate will be below 10-10 only if the extinction ratio of the downstream signal is under 7dB.