【作者】 王敏学；

【导师】 林金桐；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2010， 博士

【摘要】 全光信号处理技术是实现未来高速、大容量、高可信型全光网络的关键所在。近年来,半导体光放大器(SOA)以其体积小、功耗低、易于与其他光学器件集成等优势成为全光网络中实现全光信号处理技术的关键器件之一。本论文主要基于SOA的两种非线性效应,非线性偏振旋转(NPR)效应和交叉相位调制(XPM)效应,对全光网络关键技术进行了深入的研究。主要研究了全光波长变换,全光2R再生,全光开关键控一偏振位移键控(OOK-PolSK)码型转换,全光频率上变换,全光可调谐梳状滤波,同时多波道时分复用(OTDM)解复用技术等。论文首次提出并实现了一种基于SOA-NPR效应的偏振不灵敏的全光2R再生和同时正、反相波长变换技术。首先研究了线偏振态保持模式下,偏振不灵敏SOA的输出偏振态与探测光功率、泵浦光功率、偏置电流、泵浦光偏振态以及波长等参量的变化关系。计算得到了泵浦光输入SOA引起NPR效应时,适合进行2R再生的阶梯状(Step-Like)非线性功率传输函数。其次,实验中首次实现了仅在一支偏振分束器(PBS)两端口同时得到两路正、反相波长变换信号的实验结果,并且输出信号伴有2R再生效果。实验中,一方面测量了PBS两端口的偏振开关现象,证明了通过合理的调整泵浦光双电平的功率,单支PBS就能够同时输出两路正、反相的信号；另一方面,实验测量了输入、输出10Gb/s信号的时域波形图、光谱图、以及误码率(BER)值。与背对背的传输相比,BER为10-9时,加载ASE噪声后的信号功率代价为1.8dB,但是经过SOA-NPR效应转换后的信号功率代价有所减小,反相信号的功率代价降低了1.2dB,正相信号降低了0.8dB,证明了同时输出的正、反相两路信号得到了再生。该技术具有偏振不敏感,同时正、反相输出、信号可再生、且可应用于整个C波段的特点。论文首次提出并实现了基于SOA-NPR效应中线偏振态保持模式下的全光OOK-PolSK码型转换与波长变换技术。应用两支SOA级联的结构,消除了交叉增益调制(XGM)对输出功率波动的影响,相比采用单支SOA,功率波动由10dB以上降低至小于0.6dB,得到了功率均衡的输出信号,利用NPR效应完成了强度信息到偏振信息的转换。再经过起偏器进行偏振到强度的转换,得到的两路正、反相信号消光比(ER)大于30dB。该技术具有可处理偏振调制码型,以及整个C波段应用的优点。论文首次提出并实现了一种基于SOA-NPR效应的波长与波长间隔均可调的Lyot双折射梳状滤波器。该滤波器由两片偏振片夹着光纤型差分群时延线(DGDL)和一个SOA构成,具有波长及波长间隔均可独立进行调谐的功能。滤波器的波长间隔或自由光谱范围(FSR)可通过调整可编程DGDL进行调整,转换时间约为250μs,调节范围为±45ps。滤波器中心波长的调谐是基于SOA-NPR效应完成的。我们首次提出一种基于SOA-NPR效应的光控相位差连续可调技术,这种技术使用注入SOA的光束强度来控制SOA在产生NPR效应过程中,输入探测光TE和TM分量之间的相位差。实验证明,当输入光强从-10dBm到17dBm变化时,所产生的相位差从0到π具有连续可调的特性。实验中,通过改变输入SOA泵浦光的功率值,从而实现了Lyot双折射梳状滤波器快速而连续的中心波长调谐。在不同的滤波器波长间隔条件下,当泵浦光从-10dBm到17dBm变化时,该可调滤波器的波长调谐范围均能达到波长间隔或FSR的50%。论文首次提出并且实验验证了一种基于SOA-XPM效应的新型可级联全光串并变换技术,并将其应用到同时多波道OTDM解复用技术中。在泵浦-探测模式下,将复用信号作为探测信号,速率减半的时钟信号作为泵浦信号将同时注入SOA中。基于XPM效应,泵浦时钟的上沿将对探测信号调制一个负啁啾,相应的光谱将会产生红移；而泵浦时钟的下沿将对探测信号调制一个正啁啾,相应的光谱将会产生蓝移。因此,探测信号的两个信道能够通过XPM效应从光谱上分隔开来,再使用一个同时能将两个信道滤出的滤波器,就能够完成1：2解复用。对于20Gb/s OTDM信号进行了解复用验证性实验,使用阵列波导光栅(AWG)同时对称的滤出了并行的两路10Gb/s的信号。其中红移信道眼图的ER达到了9.65dB,蓝移信道的ER达到9.1dB。BER测试中,红移信道功率代价为1dB,蓝移信道为2dB。该方案具有结构简单、对称滤波、高速率、可级联和同时多波道输出的优点。更多还原

【Abstract】 All-optical signal processing techniques play an important role in future high-speed, large capacity and highly trustworthy all-optical networks. All-optical signal processing based on semiconductor optical amplifiers (SOAs) has attracted considerable attention during the past years due to their features such as small footprint, low power consumption, and potential photonic integration with other optical components. In this dissertation, the key techniques in all-optical networks are studied based on SOA nonlinear polarization rotation (NPR) effect and cross-phase modulation (XPM) effect. Base on such nonlinearities, many useful applications have been applied, such as all-optical wavelength conversion (WC), all-optical 2R regeneration, all-optical On-Off Keying (OOK) to Polarization-Shift Keying (PolSK) format conversion, all-optical up-conversion, tunable birefringent Lyot filter and simultaneously multi-channel Optical Time Domain Multiplexing (OTDM) system demultiplexing.We have proposed and demonstrated a simultaneous inverted and non-inverted polarization-insensitive WCs with 2R regeneration based on SOA-NPR effect, at the frist time. We have characterized the NPR effect with linear polarization maintenance arising in polarization-insensitive SOAs in terms of probe and pump power, bias current, pump polarization, and wavelength. The step-like nonlinear power transfer function for 2R regeneration, during the pump-signal-induced NPR arising in SOAs, is obtained by calculated the measured results. The complementary WC with 2R regeneration is achieved at the two output ports of a single polarization beam splitter (PBS). The polarization switching phenomena is measured by complementary output powers of the probe light with respect to the pump light injection after passing through the PBS. Therefore, both the inverted and non-inverted WC can be achieved simultaneously by properly setting the binary power level of the pump light. The temporal waveforms, optical spectrum and bit error rate (BER) are further measured. The results have shown simultaneous power penalty reductions of 1.2 dB for inverted WC and 0.8 dB for non-inverted WC at a lOGb/s BER of 10-9 compared to the back-to-back result which has loaded the amplified spontaneous emission (ASE) noise source. Thus simultaneous inverted and non-inverted WCs with 2R regeneration based on SOA-NPR effect are approved. Moreover, this technique features polarization-insensitive and can be applied for the whole C-band.The NPR with linear polarization maintenance is applied to perform OOK to PolSK format conversion in conjunction with WC function, where the power fluctuation caused by the SOA cross gain modulation (XGM) is successfully mitigated using two cascaded SOAs. The power fluctuation of the converted PolSK signal is reduced to less than 0.6 dB, compared with 10 dB fluctuation in single SOA scheme. The power to polarization conversion is accomplished through the NPR effect. The extinction ratio (ER) of polarization modulation is maintained at larger than 30 dB which is measured after a polarizer. This technique can be applied in the whole C-band.We have proposed and experimentally demonstrated a tunable fiber-optical Lyot birefringent comb filter with independent tuning of the channel spacing and wavelength using NPR in an SOA, at the frist time. The filter configuration is based on sandwiching a fiber-optic programmable differential group delay line (DGDL) and a SOA between two polarizers. The channel spacing of the filter can be tuned by adjusting the programmable DGDL. The switching time of the programmable DGDL is around 250μs, while the tunable range is±45ps. Using the NPR effect in the SOA, we have proposed an optically controlled technique to continuously verify the phase shift. The phase shift from 0 toπbetween the transverse electric (TE) and the transverse magnetic (TM) components of the input probe beam can be adjusted by varying the power of the pump light from-10 dBm to 17 dBm. Hence fast and continuously wavelength tuning of the filter can also be achieved. The wavelength tuning range is up to 50% of the arbitrary channel spacing (or FSR) when the pump power is increased from-10 dBm to 17 dBm.We have proposed and experimentally demonstrated a novel structure of a cascadable photonic serial-to-parallel converter (SPC) based on the XPM effect in a SOA for simultaneous multiple-channel OTDM demultiplexing. The serial signal and the half rate clock signal are injected into an SOA as probe and pump, respectively. The two channels of the probe signals are set at the rise and fall slopes of the pump clock pulse, respectively. As the XPM effect arises in an SOA, the probe channel which interacts mainly with the leading edge of the pump pulse has a negative XPM-induced chirp and the spectrum has only red-shifted components, while the neighbouring channel which interacts with the trailing edge has a positive chirp and its spectrum is shifted towards blue. Thus the two channels are separated in frequency domain. Then a two channel narrow bandpass filter can be used to select each channel. Consequently, the simultaneous 1:2 serial-to-parallel conversion is achieved. A proof-of-concept experiment is carried out to demonstrate error-free operation of simultaneous two-channel demultiplexing for a 20 Gbit/s OTDM signal. A subsequent array waveguide grating (AWG) is used to symmetrically filtering the optical spectra. The red-shifted signal has an ER of 9.65 dB while the blue-shifted one has an ER of 9.1 dB. In the BER test, error-free 20 Gb/s simultaneous two-channel OTDM demultiplexing is experimentally demonstrated. The red-shifted signal has a power penalty of 1 dB while the blue-shifted one has 2 dB. The proposed SPC features cascadability, compact structure, symmetrically filtering, high-speed operation, and simultaneous two-channel operation.更多还原