非均匀光纤中暗孤子传输特性研究

由于变系数非线性Schrödinger方程的增益、色散和非线性项都是变化的, 根据方程这一特点可以研究光脉冲在非均匀光纤中的传输特性. 本文利用Hirota方法, 得到非线性Schrödinger方程的解析暗孤子解. 然后根据暗孤子解对暗孤子的传输特性进行讨论, 并且分析各个物理参量对暗孤子传输的影响. 经研究发现, 通过调节光纤的损耗、色散和非线性效应都能有效的控制暗孤子的传输, 从而提高非均匀光纤中的光脉冲传输质量. 此外, 本文还得到了所求解方程的解析双暗孤子解, 最后对两个暗孤子相互作用进行了探讨. 本文得到的结论有利于研究非均匀光纤中的孤子控制技术.     

光纤中的光孤子

叙述了光纤中光孤子形成的物理机理。即光纤中光孤子的形成是光纤中散射效应和相应调制效应相互制约、平衡的结果。     

Long-range interaction of picosecond solitons through excitation of acoustic waves in optical fibers

We present the theory of electrostrictional interaction of soliton pulses in optical fibers. Solitons excite acoustic waves propagating in the direction transverse to the fiber axis. Scattering of optical radiation on these waves leads to a timing jitter of the optical pulses arrival time. We consider this effect as nonlinear self-scattering of light on acoustic waves. Because of the fact that a value of acoustic lifetime can reach a value of about 100 ns self-scattering on acoustic waves can be observed for a single optical pulse as well as for an optical pulse sequence as a whole. The value of single soliton self-frequency shift due to excitation of acoustic waves as a function of soliton duration have been obtained. For soliton duration _sol > 14 ps an acoustic wave soliton self-frequency shift is larger than the Raman soliton self-frequency shift.The obtained theoretical results describe well the long-range interaction of soliton pulse trains in an optical fiber. The value of bit error rate due to electrostrictional interaction of optical pulses in high bit rate, ultra long soliton communication systems have been obtained.     

Small-amplitude solitons in nonlinear-saturation glass fibers

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Determining the time-frequency parameters of low-power bright picosecond optical pulses by using the interferometric technique

We present an approach to the characterization of low-power bright picosecond optical pulses with an internal frequency modulation simultaneously in both time and frequency domains in practically much used case of the Gaussian shape. This approach exploits the Wigner time-frequency distribution, which can be found for these bright pulses by using a novel interferometric technique under our proposal. Then, the simplest two-beam scanning Michelson interferometer is selected for shaping the field-strength auto-correlation function of low-power picosecond pulse trains. We are proposing and considering in principle the key features of a new experimental technique for accurate and reliable measurements of the train-average width as well as the value and sign of the frequency chirp of pulses in high-repetition-rate trains. This technique is founded on an ingenious algorithm for the advanced metrology, assumes using a specially designed supplementary semiconductor cell, and suggests carrying out a pair of additional measures with exploiting this semiconductor cell. Such a procedure makes possible constructing the Wigner distribution and describing the above-listed time-frequency parameters of low-power bright picosecond optical pulses. In the appendix, we follow one of possible avenues for deriving the joint Wigner time-frequency distribution via choosing the Weil's correspondence between classical functions and operators.     

拉曼散射与自陡峭效应对皮秒孤子传输特性的影响

通过求解包含拉曼增益和自陡峭效应的高阶非线性薛定谔方程, 运用MATLAB模拟了拉曼增益和自陡峭效应共同作用对孤子脉冲在各向同性光纤中传输特性的影响, 结果表明, 自陡峭效应会导致孤子产生时域位移, 而且会使高阶孤子产生孤子分裂现象. 与此同时, 拉曼增益改变了孤子的传输特性, 抑制了自陡峭效应, 从而导致脉冲宽度增大、脉冲偏移程度减弱、高阶孤子分裂成基阶孤子所需的传输距离增大.     

The mobility of nonlocal solitons in fading optical lattices

We study the soliton mobility in nonlocal nonlinear media with an imprinted fading optical lattice. The results show that the transverse mobility of solitons varies with the lattice decay rate and the nonlocality degree, which provides an opportunity for all-optical control of light.     

Periodic solitons in dispersion decreasing fibers with a cosine profile

Periodic solitons are studied in dispersion decreasing fibers with a cosine profile. The variable-coefficient nonlinear Schr¨odinger equation, which can be used to describe the propagation of solitons, is investigated analytically. Analytic soliton solutions for this equation are derived with the Hirota’s bilinear method. Using the soliton solutions, we obtain periodic solitons, and analyze the soliton characteristics. Influences of physical parameters on periodic solitons are discussed. The presented results can be used in optical communication systems and fiber lasers.     

Propagation of chirped nonlinear pulses in a lossy highly birefringent single-mode optical fibre

A new model of the nonlinear propagation of optical solitons with initial linear frequency chirp through lossy highly birefringent fibres, allowing the improvement of the practical results concerning the distortionless signal transmission in ultrahigh-speed communications, is presented within the framework of a system of coupled nonlinear Schroedinger (CNLS) equations. This model demonstrates the existence of bound chirped solitons in a lossy single-mode highly birefringent fibre.     

Polarization-dependence of optical spatial solitons in photoisomerization material

Experimental observation of spatial solitons in azobenzene-doped organic polymer is demonstrated in dye-doped polymer bulk material. Solitons cannot only be formed in this material with linearly polarized light, but also with circularly polarized light. An interesting phenomenon is revealed that the soliton is polarization-dependent. The solitons with the same intensity but with different polarizations have different widths. The experimental results are further theoretically explained with the dynamics model based on a photochemical process, namely photoisomerization.     

非局域克尔介质中空间光孤子的相互作用

研究了强非局域克尔介质中光束的演化规律，通过相位分析得到了空间孤子相互作用所满足 的非局域非线性薛定谔方程的简化近似模型，并获得了双光束传输的解析解.结果表明在传 输过程中相互作用的高斯光束的相位决定于它们的输入总功率.以振幅一强一弱共同传输的 高斯光束为例进行了具体研究，得到了强光和弱光的解析式，相位分析显示弱光在相当短的 传输距离之内能产生大的相移，可以通过对强光能量的调控来实现对弱光的相位调制. 关键词： 非局域克尔介质 空间光孤子 孤子相互作用 相位调制     

空间光孤子脉冲在平面光波导中的传输

分析研究了空间光孤子脉冲化后在反常群速色散的克尔非线性平面光波导中的传输特性和稳 定性.当空间光孤子脉冲的时间宽度等于某一临界值时，脉冲发生自陷，小于该值时，脉冲 发生扩散，大于该值时，脉冲发生塌陷.空间光孤子的阶数越高，这个临界值越小.当空间光 孤子脉冲的时间宽度等于某一特定值时，脉冲塌陷最快，与这个特定值相差越大，塌陷越慢 .空间光孤子的阶数越高，这个特定值越小.脉冲自陷后的峰值光强、时间和空间宽度与输入 时的值有明显的不同. 关键词： 脉冲自陷 脉冲塌陷 光孤子     

A volume holographic optical element for optical coupling to single-mode fibers

We propose and demonstrate a volume holographic optical element (VHOE) for signal-mode fiber coupling and the sending of conjugate waves of reference light for the construction of holographic elements. Given the inherent Bragg conditions of the VHOE, the angular tolerances of the conjugate reading light in both the horizontal and vertical directions are studied under different conditions.     

大芯径石英光纤中皮秒脉冲激光的自聚焦

本文报道了对大芯径石英光纤中皮秒脉冲激光自聚焦现象的实验研究和理论分析.文中测量了自聚焦先场的近场光强轮廓,研究了自聚焦光场的时域和频域性质,并对环形自聚焦光场的成因进行了解释.     

Ultraslow optical solitons in tunnel-coupled double semiconductor quantum well

This paper investigates the nonlinear evolution of the pulse probe field in an asymmetric coupled-quantum well driven coherently by a pulse probe field and two controlled fields. This study shows that, by choosing appropriate physical parameters, self-modulation can precisely balance group velocity dispersion in the investigated system, leading to the formation of ultraslow optical solitons of the probe field. The proposed scheme may lead to the development of the controlled technique of optical buffers and optical delay lines.     

Stochastic perturbation of Kerr law optical solitons

The soliton perturbation theory is used to study and analyze the stochastic perturbation of optical solitons, due to Kerr law nonlinearity, in addition to deterministic perturbations of optical solitons that is governed by the nonlinear Schrödingers equation. The Langevin equations are derived and analyzed. The deterministic perturbations that are considered here are of both Hamiltonian as well as of non-Hamiltonian type.