| With the increasing number of subscribers and the demand of bandwidth,WDM-PON is regarded as one of the preferred schemes for optical access network,because of its high backward-compatibility ability,low cost,convenient operation and maintenance,and the configuration of specific wavelength for each user,high network security and higher transmission rate.But configuring different transmitters for each ONU increases the complexity and cost of the system.RSOA has modulation and saturation high-pass filtering effect.The remodulation scheme based on RSOA use saturation high-pass filtering effect to erase downlink signal,simultaneously modulation uplink signal,structure simple,do not need extra light source,work band width,low cost,can realize colorless ONU.The traditional RSOA not only has small modulation bandwidth,but also the deep saturated RSOA will inevitably rewrite the uplink signal,which limits the development of this scheme.The R-QDSOA has higher modulation bandwidth,and the two-electrode R-QDSOA can improve the modulation performance by adjusting the current distribution of the two segments,so we propose to replace the R-QDSOA of RSOA.The main research contents are as follows:?1?Modulation characteristics of non-uniform current density of R-QDSOA are studied.The effect of length ratio and current density ratio on the two-electrode R-QDSOA gain is analyzed.The effects of length ratio and current density ratio on modulation bandwidth,modulation depth and modulation linearity is analyzed using two-electrode R-QDSOA scheme.The research results show that the more current density in the rear section and the length ratio of 1:1,the better the modulation performance,and the modulation bandwidth is up to 22GHz.Compared with the ordinary R-QDSOA,it not only improves the modulation bandwidth,but also improves the modulation depth and no loss modulation linearity.?2?The modulation characteristics of two-electrode R-QDSOA is studied by the way of front modulation that the front section is injected with the modulation current and the rear section is injected dc current and rear modulation that the front is injected dc current and the rear section is injected modulation current,respectively.It is found that when the current is allocated more in the rear section.the main modulation action is in the front section,and when the current is allocated more in the front section,the main modulation effect is in the rear section.The two modulation methods have the performance of equivalent or even better than the two-section modulation.?3?The high order modulation and remodulation based on two-electrode R-QDSOA are studied.The high order modulation and remodulation scheme of QAM is realized by four methods:the segment non-uniform modulation,the front modulation,the rear modulation and common modulation.The results show that under the same conditions,the high order modulation performance of the segment non-uniform modulation and the front modulation is superior to the post modulation and the ordinary modulation,and the QAM remodulation performance of the front modulation is the best.When the 16QAM modulation error rate is lower than the FEC threshold of 3.8×10-3,the modulation rate of40Gb/s can be achieved by using the front modulation scheme.At the same time,the modulation of the downlink NRZ signal and 10Gb/s modulation of the upstream 4QAM signal can be realized by using the front modulation mode. |
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