[目的]高速无源光接入网络中存在光纤色散、非线性损伤和带宽限制等问题,导致传统强度调制和直接检测技术的功率预算损失较高,难以满足高速无源光接入网络的要求.[方法]为了更好地提升强度调制和直接检测光接入系统的速率和性能,文章在Volterra判决反馈均衡器(VDFE)的基础上,研究了基于递推最小二乘估计(RLS)算法的VDFE-RLS信道均衡方法.该均衡器采用RLS算法对其中的抽头系数进行更新.该均衡器包含了一、二、三阶Volterra级数,其中一阶Volterra级数对线性损伤进行补偿,二阶和三阶Volterra级数能够对非线性损伤进行补偿.文章将该均衡器应用于经过20 km传输后的单波长为200 Gbit/s的O波段强度调制和直接检测技术的下行光接入系统中.[结果]实验结果表明,RLS算法相比传统的最小均方(LMS)算法在均衡器中表现出来的性能更好.此外,VDFE-RLS可以实现>29 dB的功率预算.VDFE-RLS相比于传统的基于Volterra的前馈均衡器(VFFE),当VDFE-RLS和VFFE-RLS均衡器长度相同时,可以实现2.2 dB功率预算的提升.当VDFE-RLS的均衡器长度为VFFE-RLS的一半时,前者相比后者仍可以提升0.5 dB的功率预算.[结论]文章所述系统相比其他传统系统在能够缩短均衡器长度的同时,能提高系统的功率预算,还能最终恢复出准确度较高的信号.
[Objective]The optical fiber dispersion,nonlinear impairments and bandwidth limitation in high-speed passive optical access networks lead to high power budget loss in traditional intensity modulation and direct detection schemes,which are diffi-cult to meet the requirements of future high-speed passive optical access networks.[Methods]In order to improve the speed and performance of the intensity modulation and direct detection optical access system,based on the Volterra Decision Feedback E-qualizer(VDFE),this article studies the channel equalization method of VDFE-RLS based on Recursive Least Squares(RLS)algorithm.This equalizer uses RLS algorithm to update the tap coefficients.The equalizer includes a three-order Volterra se-ries,allowing it to compensate for both linear and nonlinear impairments.In this paper,VDFE-RLS is applied to the downlink optical access system with a single wavelength 200 Gbit/s based on O-band intensity modulation and direct detection scheme af-ter 20 km transmission.[Results]The experimental results show that the RLS has better performance than conventional Least Mean Square(LMS)algorithm in the equalization process.Besides,VDFE-RLS can achieve a power budget greater than 29 dB.When the length of the equalizer is the same,VDFE-RLS can increase the power budget by 2.2 dB compared with the conventional Volterra Feed Forward Equalization(VFFE)-RLS equalizer.When the length of VDFE-RLS equalizer is half that of VFFE-RLS,the VDFE-RLS can increase the power budget by 0.5 dB compared with the VFFE-RLS equalizer.[Conclu-sion]Compared with other traditional methods,the proposed method can shorten the length of the equalizer and increase the power budget of the system,and finally recover the signal with better performance.