EDFA中基孤子脉冲的传输及啁啾特性

文章数值分析了负色散掺铒光纤放大器(EDFA)中基孤子脉冲传输及啁啾特性,给出了一种利用EDFA获得线性啁啾的新方法.数值分析结果发现:增益系数μ>1时,基孤子脉冲在EDFA中传输能够获得很好的线性啁啾,并且啁啾的特性受选取的EDFA长度L的影响,L越大时线性啁啾越明显,线性啁啾所占的脉冲区域越窄.最后计算了输出脉冲在啁啾补偿后获得的压缩因子和基座能量比.     

线性源啁啾对孤子脉冲压缩的影响

通过线性源啁啾对孤子脉冲压缩影响的研究,发现泵浦脉冲和孤子脉冲的源啁啾参量地脉冲压缩产生重要影响,且孤子脉冲压缩存在最佳光纤长度。在泵浦功率一定的条件下,选取负啁啾的泵浦脉冲正啁啾的孤子脉冲可以获得高压缩因子的光脉冲;同时选取负啁啾的泵浦脉冲和正啁啾的孤子脉冲易于产生更短的压缩光脉冲。     

孤子对在EDFA中放大的数值研究

对孤子对在EDFA中的放大进行了研究.数值研究表明,孤子对在EDFA中能得到放大,但放大过程中孤子间距减小,孤子间形成小脉冲.引入非线性增益后,孤子对得到较大程度的放大,孤子间距减小程度降低,仍有小脉冲;引入初始啁啾后,孤子对得到放大,程度不如单独引入非线性增益时,孤子间距不变,无小脉冲产生;共同引入非线性增益和初始啁...     

掺铒光纤放大器中孤子脉冲获得线性啁啾的研究

为了研究孤子脉冲经掺铒光纤放大器演变后的啁啾特性,采用了对称分步傅立叶的数值方法,对孤子脉冲在不同增益条件下的演变和线性啁啾特性进行了数值仿真。数值计算的结果表明：当满足增益系数μ远大于1时,基孤子脉冲在放大器中传输能够获得很好的线性啁啾,且发现脉冲的啁啾特性受选取的放大器长度参量的影响;啁啾越明显的脉冲,线性啁啾所占的区域越窄。进一步研究还发现初始啁啾系数和孤子阶数对脉冲获得的线性啁啾均有很大影响,初始正啁啾系数和高孤子阶数均能增强输出脉冲的线性啁啾特性。因此,利用孤子脉冲在掺铒光纤放大器中传输的非线性效应能够获得良好的线性啁啾,这对实现高质量的脉冲压缩是很有帮助的。     

10GHz ps光孤子在G652光纤中的绝热传输实验

利用二次谐波频率分辨光学门(FROG)脉冲分析仪,实验研究了一阶啁啾ps光孤子在普通单模光纤(SMF)中长距离绝热传输时脉冲波形、脉宽和啁啾的变化规律。实验结果表明,在色散较大的标准SMF中,一阶啁啾孤子的稳定传输长度超过1000个色散长度,即很好地保持双曲正割波形不变(啁啾不影响孤子的波形),但啁啾孤子的脉宽展宽速度高于非啁啾孤子绝热传输的微扰结果;采取预加重措施,可以减小孤子脉宽的增大。因此,对于占空比较小的ps孤子脉冲,可以不必采用复杂的消啁啾和色散管理措施,就可以利用绝热方式进行稳定传输。     

基于拉曼放大对色散渐减光纤的绝热压缩效果的优化

数值研究了光纤损耗对色散渐减光纤中基孤子脉冲的绝热压缩的影响,并分析了利用分布式的拉曼放大来提高DDF的绝热压缩效果的方案.结果表明:光纤损耗严重破坏了DDF对基孤子绝热压缩的效果;采用分布式的拉曼放大能对DDF的绝热压缩起到很好的优化效果,获得更高的压缩因子和脉冲能量;当拉曼增益系数选取优化值0.27/LD时,脉宽为10 ps的基孤子脉冲压缩后可得到脉宽仅417fs、脉冲能量增至5.9倍、峰值功率增至136.3倍、基座能量比仅为2.8%的输出脉冲.     

初始啁啾和光纤损耗对皮秒脉冲孤子效应压缩的影响

运用分步傅立叶方法数值模拟了皮秒脉冲在单模光纤中的传输 ,计算和分析了初始啁啾和光纤损耗对皮秒脉冲孤子效应压缩的影响。结果表明 ,两者对具有一定峰值功率的脉冲孤子效应压缩的影响具有互补性 ,即两者对脉冲压缩的作用相反。进一步研究表明 ,对在损耗光纤中传输的皮秒脉冲 ,如果给其加适当大小的初始啁啾将得到很好的压缩效果     

单模光纤中啁啾脉冲的分裂机制

采用分步傅里叶算法数值求解非线性薛定谔方程,分析了单模光纤中不同情形下皮秒量级啁啾脉冲的分裂机制。结果表明,对于较短的脉冲(10 ps),啁啾脉冲分裂从高阶孤子压缩导致的脉冲塌陷开始;对于较长的脉冲(200 ps),脉冲分裂主要由调制不稳定性导致;对于介于两者之间的脉冲(50 ps),噪声使得脉冲分裂机制从高阶孤子压缩转向调制不稳定性。初始正、负啁啾能分别加速和延缓短脉冲分裂,而初始啁啾对长脉冲分裂影响很小。初始啁啾对脉冲分裂的影响与其分裂机制密切相关。     

色散缓变光纤中皮秒啁啾脉冲的孤子效应压缩

文章从描述皮秒光脉冲在色散缓变光纤（FSDD）中所满足的非线性Schroedinger(NLS)方程出发，数值模拟了高阶皮秒光孤子在不同的FSDD中的孤子效应压缩，并讨论了初始啁啾对其的影响，结果表明，利用FSDD和孤子效应压缩来压缩带有初始啁啾的高阶皮秒光孤子，可以得到更高的压缩比和品质因子，压缩后的脉冲的峰值功率明显提高，而且脉冲被压缩到最窄所需的光纤长度也大大缩短，最后讨论了初始脉宽的影响。     

啁啾孤子的传输研究

研究啁啾孤子在传输过程中的脉冲形状和频率啁啾的演化过程。分别分析了具有初始正、负啁啾孤子在传输过程中的脉冲展宽和压缩的全过程，总结出啁啾孤子对通信系统性能的影响。     

Special erbium fiber amplifiers for short pulse switching, lasers,and propagation

We show that specially tailored erbium-doped fiber amplifiers (EDFA's) can be useful for short-pulse soliton lasers, switching, and propagation. EDFA properties include group-velocity dispersion, birefringence, doping level, and doping distribution; and changing each of these properties enables novel applications. Polarization-maintaining EDFA's can Re used in erbium-doped fiber lasers to avoid intensity-dependent or temperature-dependent state of polarization. We have demonstrated a passively mode-locked erbium-doped fiber laser that generates nearly transform-limited 320 fs pulses with 40 pJ energy using a polarization-maintaining EDFA near the zero dispersion wavelength and a bulk InGaAsP saturable absorber. Moderately birefringent EDFA's can be used to control the walkoff and interaction between orthogonally polarized solitons in all-optical switches. For example, through numerical simulations, we design an all-optical cascadable logic gate with a fanout of 2.7 and energy contrast of 5.5 based on interactions in a soliton period long EDFA. Furthermore, distributed EDFA's can be used for long-distance soliton propagation to shepherd the pulse using bandwidth-limited gain. For picosecond soliton pulses, we show that soliton self-frequency shift and Gordon-Hans effects limit propagation to below 100 km even for low-dispersion fibers. Bandwidth-limited amplification in EDFA may counteract frequency shift due to the soliton self-frequency shift, while frequency filters may suppress the Gordon-Hans effect. Also, because the gain spectral profile for the three-level EDFA changes with pump intensity, complications arise from pump attenuation, and the corresponding changes in the gain spectral profile along the length of the fiber     

光纤中双脉冲传输的频率啁啾及脉冲压缩

对双脉冲在光纤中传输时所满足的非线性耦舍方程进行了理论分析和数值计算,求得了脉冲演化时啁啾参量的一般表达式。结果表明,利用交叉相位调制效应压缩光脉冲时,无论泵浦脉冲还是信号脉冲,其线性源啁啾都对光脉冲的压缩产生重要影响。在泵浦功率一定的条件下,选取负啁啾的泵浦脉冲和正啁啾的信号脉冲易于获得更短的压缩光脉冲。     

Simultaneous amplification and compression of ultrashort solitons in an erbium-doped nonlinear amplifying fiber loop mirror

A simple technique for simultaneous amplification and compression of ultrashort fundamental solitons is proposed. It is based on an erbium-doped nonlinear amplifying fiber loop mirror. Numerical simulations show that, unlike conventional erbium-doped fiber amplifiers in which nonlinear effects lead to serious degradation of pulse quality, the proposed device performs efficient high-quality amplification and compression of ultrashort solitons while nearly preserving the soliton nature of the input pulses. We have also studied the effects of loop characteristics, nonsoliton input pulses, and higher order fiber effects on the device performance and show that the proposed scheme is fairly insensitive to small variations in both the loop and input pulse parameters.     

Amplification of ultrashort solitons in erbium-doped fiberamplifiers

Pulse amplification in erbium-doped fiber amplifiers is studied by considering a general model that includes both gain saturation and gain dispersion. The effects of gain dispersion are studied numerically for the case in which a fundamental soliton is launched at the amplifier input. The results show that fiber amplifiers may be useful for simultaneous amplification and compression of weak optical pulses. Under high-gain conditions the input pulse is found to split into a train of amplified subpulses whose width and repetition rate are governed by the gain bandwidth. The numerical results are in qualitative agreement with recent experiments     

基于交叉相位调制的孤子脉冲压缩效应研究

在负色散区 ,基本孤子在光纤中传输时其波形与脉宽保持不变。提出一种在负色散区利用交叉相位调制效应压缩基本孤子脉冲的新方法。采用分步傅里叶方法对非线性耦合方程进行了数值计算与模拟。研究了不同抽运功率、不同抽运脉冲啁啾参数以及不同脉宽对基本孤子脉冲压缩的影响。发现基本孤子脉冲不仅能够被压缩 ,而且光纤存在最佳压缩长度。在抽运功率一定的条件下 ,选取负啁啾的抽运脉冲 ,可获得更高压缩比的压缩光脉冲。另外 ,不同的脉冲宽度对孤子脉冲的压缩产生较大的影响 ,一般情况下 ,选用较窄的抽运脉冲易于产生较短的压缩光脉冲