利用从非归零(NRZ)信号中全光提取的时钟,采用太赫兹光非对称解复用器(TOAD)实现了10 Gbit/s非归零码到归零(RZ)码的码型转换。非归零信号采用半导体光放大器(SOA)进行时钟分量增强并用平面波导阵列(AWG)滤出相应的伪归零(PRZ)信号,然后采用半导体光放大器注入锁模光纤环形激光器进行时钟提取,提取的时钟信号和待转换的非归零信号分别作为抽运光和探测光输入太赫兹光非对称解复用器,在其中进行码型转换。转换后输出的归零信号的质量仅由恢复的时钟信号和非归零信号的质量决定,受太赫兹光非对称解复用器中半导体光放大器增益恢复时间的影响极小。实验测得转换后的归零信号消光比为8.7 dB,码型效应非常低,其光谱明显展宽,并且出现谱间隔为0.08 nm的多峰结构,与10 Gbit/s的比特速率相对应。该方法对时钟信号的码型效应有一定的容忍度。

10 Gbit/s all-optical non-return-to-zero (NRZ) to return-to-zero (RZ) conversion is demonstrated based on terahertz optical asymmetric demultiplexer (TOAD) using all-optically recovered clock from the NRZ signal. The clock component is enhanced in an semiconductor optical amplifier (SOA) and the pseudo-return-to-zero (PRZ) signal is filtered. The PRZ signal is input into an injection mode-locked fiber ring laser for clock recovery. The recovered clock and the NRZ signal are input into TOAD as pump signal and probe signal, respectively, and format conversion is performed. The quality of the converted RZ signal is determined by that of the recovered clock and the NRZ signal, whereas hardly influenced by the gain recovery time of the SOA. In the experimental demonstration, the obtained RZ signal has an extinction ratio of 8.7 dB and low pattern dependency. After conversion, the spectrum broadens obviously and shows multimode structure with spectral interval of 0.08 nm, which matches with the bit rate of 10 Gbit/s. Furthermore, this format conversion method has some tolerance on the pattern dependency of the clock signal.