基于中国自然科学基金网(NSFCNet)的400 km×10 Gb/s光传输链路实现了40 Gb/s光传输,没有出现误码率(BER)平台,说明在常规的中短距离10 Gb/s系统可以直接升级至40 Gb/s系统,而不需要升级传输链路。但是,由于相对10 Gb/s系统而言40 Gb/s系统的色散容限非常小,在升级时必须精确补偿原有链路的色散,在接收机前一般需要加可调色散补偿单元。同时,还分析了光纤注入功率对系统性能的影响,结果表明在设计这种由10 Gb/s向40 Gb/s升级的系统时,不仅要考虑信号带宽增加带来信噪比要求的提高,而且必须充分考虑光纤非线性的影响。

A 40 Gb/s optical transmission based on the NSFCNet 400 km×10 Gb/s system is realized without any bit error rate (BER) floor. It is shown that typical 10 Gb/s systems of middle or short distance can be upgraded to 40 Gb/s directly without change the transmission links. However, the chromatic dispersion must be compensated precisely when the system upgrades, because the dispersion tolerance of 40 Gb/s systems is much lower than that of 10 Gb/s system. Meanwhile, the influence of the optical power injected into the fiber links is also investigated. The results show that the effect of the fiber nonlinearity must be considered as well as the improvement of optical signal to noise ratio (OSNR) due to the enlarged signal bandwidth when the bit rate of transmission system is upgraded from 10 Gb/s to 40 Gb/s.