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对正交频分复用无源光网(OFDM-PON)的上行通道物理层的吞吐量进行研究。OFDM-PON在光网络单元(ONU)端采用反射式半导体光放大器(RSOA)作为无色光源,实现双边带光强度调制,并在光线路终端(OLT)采用加半导体光放大器(SOA)前置放大的PIN光二极管做直接检测。基于一个RSOA的窄带相干积分模型,采用对有源区中载流子速率方程和光波传播方程的微扰解对RSOA的动态电光调制特性和频率啁啾特性进行理论与实验探讨,证明RSOA具有低通调制特性,其3dB截止频率关联于偏置电流和输入光功率。利用RSOA的频率啁啾和SOA的高通增益特性,并将RSOA与中心波长蓝移的光滤波器级联,实现光学均衡,把上行通道的3dB截止频率从1.5GHz扩展到2.2GHz。进一步采用自适应比特加载的调制格式,使通过一个RSOA的上行数据吞吐量可以达到4Gb/s以上,则一个包含10个ONU的OFDM-PON的上行吞吐量可达到40Gb/s。
The throughput of uplink physical layer in OFDM (Orthogonal Frequency Division Multiplexing) Passive Optical Network (OFDM-PON) is studied. OFDM-PON uses a reflective semiconductor optical amplifier (RSOA) as a colorless light source at the optical network unit (ONU) side to achieve double-sideband light intensity modulation. The optical line terminal (OLT) adopts a semiconductor optical amplifier Magnified PIN light diode to do direct inspection. Based on an RSOA narrow-band coherent integration model, the dynamic electro-optical modulation characteristics and frequency chirp characteristics of RSOA are studied theoretically and experimentally by using perturbation solutions of carrier velocity equations and light wave propagation equations in the active region. It is proved that RSOA has a low Pass modulation characteristics, the 3dB cutoff frequency associated with the bias current and input optical power. Taking advantage of the frequency chirp of RSOA and the high-pass gain of SOA, the RSOA is cascaded with the blue-shifted optical filter of the center wavelength to achieve optical equalization, and the 3dB cutoff frequency of the uplink channel is extended from 1.5 GHz to 2.2 GHz. The modulation format of adaptive bit loading is further adopted so that the uplink data throughput of one RSOA can reach more than 4 Gb / s, and the uplink throughput of an OFDM-PON comprising 10 ONUs can reach 40 Gb / s.