【作者】 刘爽；

【导师】 孙军强；

【作者基本信息】 华中科技大学 ， 电子科学与技术， 2010， 博士

【摘要】 WDM-PON是国际上近年兴起的全光接入网领域前沿热点研究方向。然而,阻碍其快速发展的“绊脚石”主要是WDM-PON成本居高不下,在目前的网络市场情况下运营商很难冒此风险大面积铺设WDM-PON接入网,这无疑对WDM-PON的研究发起了新的挑战。WDM-PON的高昂成本主要源于其中心局端及光网络单元大量光源的成本。为解决这一问题,目前采用的技术主要有宽带光源的光谱分割技术和在此基础上的注入锁定FP-LD(或RSOA)技术,但这两者均采用非相干光源从而引入较大的强度噪声限制了网络运行速度。多波长激光源作为WDM-PON中心化光源取代以上两种非相干光源技术,将有利于实现高速率运转的WDM-PON。本论文从理论和实验两方面对多波长光纤激光器及相关技术进行了较为深入细致的研究,并取得了若干创新性成果。主要内容包括：(1)对基于悬臂梁结构的多波长可调谐系统进行了理论及实验研究,并首次把多波长光纤叠层布拉格光栅应用于基于悬臂梁结构的多波长可调谐系统,并且得到了自由光谱范围可调谐的多波长滤波器,波长间隔可调谐范围为0.12nm,调制精度达到0.02nm/cm。(2)提出了一种新颖的马赫-泽德涉仪(MZI)的隔离器加强双通道结构。然后,通过详细的理论分析,我们对隔离器加强MZI结构与传统单通道MZI结构和直接双通道MZI结构的梳状滤波特性进行了比较研究。特别考察了MZI的耦合器分支耦合比和偏振相位差对三种MZI结构的滤波消光比及透射峰3-dB带宽的影响。利用三种MZI结构作为掺铒光纤激光器的多波长选模器件,我们分别获得三类多波长掺铒光纤激光器(单通道MZI多波长掺铒光纤激光器、直接双通道MZI多波长掺铒光纤激光器和隔离器加强双通道MZI多波长掺铒光纤激光器)。在直接双通道MZI情况下,我们获得了16个波长的稳定激射(波长间隔21.5 GHz)。然而,直接双通道MZI多波长掺铒光纤激光器通常有较低的激光消光比(仅-26 dB)且缩小波长间隔至单通道MZI多波长掺铒激射时的一半。因此,我们进而采用提出的隔离器加强双通道MZI作为多波长选模器件,获得了高激光消光比(>50dB)的多波长激射(10个振荡波长,间隔为43GHz)。特别地,相比单通道MZI多波长振荡的激射线宽0.0581nm,直接双通道MZI和隔离器加强双通道MZI情况能分别窄化激射线宽至0.031nm和0.037nm。而且,两种双通道MZI多波长掺铒光纤激光器都能保持非常好的稳定性。(3)对基于保偏光纤的光纤环镜进行了理论及实验研究,利用保偏光纤的双折射效应,并将其加入3dB耦合器中,入射光在光纤环镜内干涉叠加并在输出端会产生梳状滤波谱,因此使得这种特殊的光纤环镜具有了梳状滤波的特性。通过改变保偏光纤的长度,可以得到波长间隔为0.4nm和0.8nm的多波长滤波器。再利用高非线性光纤以及高非线性光子晶体光纤在光纤谐振腔中的四波混频效应抑制掺铒光纤放大器的均匀展宽引起的模式竞争,结合基于保偏光纤环镜的多波长滤波器,可以产生波长间隔为0.4nm以及0.8nm,至多15个波长同时稳定输出的多波长光纤激光器。(4)提出了两个不同波段基于SOA的多波长光纤激光器设计方案,并实验验证了多波长的稳定输出。实验中首先用基于SOA的环形腔结构实现了C+L波段的25个波长输出。之后又首次采用1060nm波段的SOA作为增益介质,并结合保偏光纤Sagnac环镜作为梳状滤波器,实现了11个波长的稳定输出。更多还原

【Abstract】 WDM-PON is a frontier and hot research subject in recent years. However, WDM-PON has not been commercially deployed, due to its ultra-high implementation cost. Although internet users would like to have considerably higher bandwidth, they do not want to pay subscription fee much higher than the current access networks. It is a big risk for the telecommunication operators to widely deploy WDM-PONs at present. The main cost of WDM-PON is the installing and maintaining of many wavelength-specific optical transmitters at the central office (OC) and optical network units (ONU). To address this issue, it is desirable to use wavelength independent (colorless) light sources to replace those wavelength-specific optical transmitters, for example, using the spectrum-sliced broadband optical sources technology or their injection-locked FP-LD (or RSOA) technology. However, both of the two technologies use the incoherent optical sources and induce some intensity noise, hence can only make a lower rate WDM-PON. Instead of the incoherent optical sources, multiwavelength lasers can provide the coherent sources, and have a significant potential to develop a cost-efficient and high-speed WDM-PON.The research work presented in this dissertation focused on the frontier area of multiwavelength lasers as the centralized optical sources of WDM-PONs. Considering the compatibility and integration between the centralized optical sources and all-fiber WDM-PON, high-performance multiwavelength fiber lasers are specially investigated, such as EDFA, SOA, based multiwavelength fiber lasers.The major achievements of this thesis are summarized as follows:(1)A novel FSR-tunable FPF based on two superimposed FBGs (SFBGs) with initially uniform periods but slightly different Bragg wavelengths, is proposed and demonstrated. The SFBGs were glued onto the lateral surface of a specially-designed cantilever beam and linearly chirped by the beam bending-induced strain gradient. As a result, their reflection bands overlapped and a grating-based FPF with a tunable FSR was formed. Finally, a continuous tuning range of 0.12 nm and a tuning rate of 0.04 nm/cm have been realized experimentally. (2) We have proposed a novel Mach-Zehnder interferometer (MZI) configuration, namely, isolator-assisted double-pass MZI. The filtering characteristics of the proposed isolator-assisted double-pass MZI are analyzed and examined theoretically in comparison with those of the single-pass and direct double-pass MZI. It is shown that the isolator-assisted double-pass MZI has some intriguing advantages, including the narrower 3-dB bandwidth per transmission peak and the higher extinction ratio. Using the three types of MZI configurations as a comb-like filter in the laser cavity, experimental investigations for generating multiwavelength oscillations are carried out. We have experimentally demonstrated high-performance multiwavelength EDFA-based fiber lasers with 8-wavelength simultaneous oscillations spaced at 43 GHz and high extinction ratio of more than 40 dB. The lasers have a good stability with a maximum power fluctuation per lasing channel of less than 0.6 dB.(3) We have proposed and demonstrated a novel and simple technique to generate stable multiwavelength oscillations in an EDFL. A multiwavelength erbium-doped fiber laser by incorporating a HNLF and PMF Sagnac filter has been presented. Over 16 wavelengths simultaneous lasing with a spacing of 0.4nm was achieved. The laser had a total output power of-3dBm, a bandwidth of 0.05nm and an extinction ratio of-50dB. The lasing states were observed to be very stable. The power fluctuation is less than 0.5dB when monitored over a period of an hour.(4) We have experimentally investigated SOA based multiwavelength fiber lasers at both C+L band and 1060nm band. We have proposed, for the first time to the best of our knowledge, the 1060nm band SOA based multiwavelength fiber laser by introducing a PMF Sagnac loop mirror. Using the linear cavity configuration, we realized multiwavelength lasing with narrow linewidth and stable power output. Up to 11 wavelengths with channel spacing of 0.39nm have been presented, and the output power stability is quite good.更多还原