Under the consideration of the external input jitter and the internal phase noise

the optimization algorithm of the bandwidth for the PLL(Phase-Locked Loop) of OTU(optical transponder unit) can be deduced and obtained through improving the former calculation and analytical methods. The optimal bandwidth of the PLL can be obtained after analyzing to ensure the clock output of the OTU has a lower jitter noise. And then the optimization algorithm is applied in 2.5Gbit/s and 10Gbit/s of the OTU

the optimal parameters of the PLL and the output jitter value of the regenerator can be acquired by taking the quantitative and qualitative analysis of the loop parameters. The study shows the optimization algorithm is better suitable for the OTU and play an important role in the practical application.