Reduction of amplified spontaneous emission from a transmittedsoliton signal using a nonlinear amplifying loop mirror and a nonlinearoptical loop mirror

The amplified spontaneous emission (ASE) from concatenated erbium-doped fiber amplifiers (EDFA's) in a 10 Gb/s 500 km soliton transmission system has been successfully reduced through the use of a nonlinear amplifying-loop mirror (NALM). By using the NALM the ratio of the signal peak to ASE was improved from 17.4:1 to 24.9:1. A similar result was obtained for a nonlinear optical-loop mirror (NOLM) with a 6:4 directional coupler. It is noted that pulse transmission through the NALM or the NOLM gives rise to frequency chirp, which means that these fiber devices are not appropriate for use at the midpoint of a long-distance soliton transmission. The chirp characteristics caused by the NALM were also described and the optimum condition for nonlinear switching was obtained     

Noise filtering with the nonlinear optical loop mirror

The operation of a nonlinear optical loop mirror as a passive and signal polarization independent noise filter, is investigated experimentally. Spontaneous emission not within the signal spectrum is rejected leaving a receiver noise limited solely by signal-spontaneous beat noise. The receiver power penalty caused by spontaneous emission (@BER=10^-9 (PRBS)) was improved from 3 dB to 0.4 dB by propagating a signal through the loop. A comparison between this nonlinear filtering: technique and a variable band-pass filter is also made     

掺Yb3+光纤放大器的自发辐射噪声分析

为了研究掺Yb3+光纤放大器中自发辐射噪声分布情况,利用离散化的方法求解掺Yb3+)光纤放大器的速率方程,理论研究了不同的抽运方式、端面反射率、抽运功率以及有无滤波等条件下,端面抽运掺Yb3+光纤放大器中自发辐射的功率放大特性.结果表明,不同边界条件下的自发辐射功率差异较大;通过减少光纤端面的菲涅耳反射和利用滤波技术等方法,可有效抑制光纤激光放大器中自发辐射噪声的功率放大.     

Suppression of relaxation oscillations in tunable fiber lasers witha nonlinear amplified loop mirror

The concept of relaxation oscillation damping in a tunable fiber laser with a nonlinear absorber or loss element is demonstrated, using a dual-cavity erbium-doped fiber laser. A nonlinear amplified loop mirror was employed as the nonlinear loss element to facilitate damping. Experimental results exhibiting complete elimination of relaxation oscillations are presented     

Self-switching with a nonlinear birefringent loop mirror

We investigate switching characteristics of the nonlinear birefringent loop mirror which consists of a symmetric directional coupler, a birefringent fiber, and a symmetry-breaking element that converts linearly polarized light to circularly polarized light, and vice versa. The condition for total reflection in the linear regime is obtained using the Jones matrix formalism, The switching curves have been obtained through numerical computations both in the nondispersive pulse regime and in the soliton-like pulse regime. Parameter values suitable for practical applications of our device as an intensity filter are obtained     

Bidirectional amplification with nonsaturable absorption and amplified spontaneous emission

A theory of bidirectional amplification is developed and applied to single-pass and double-pass laser amplifier configurations. The effects of nonsaturable absorption, longitudinal amplified spontaneous emission (ASE) gain saturation, and ASE line narrowing are included in a self-consistent formulation. An estimate of aperture scaling limitations due to transverse ASE is included. Laser performance is discussed for some conditions typical of large aperture, multikilojoule, rare gas halide (RGH) fusion amplifiers. This formulation permits tradeoff studies to be performed rapidly by altering variables spanning an eight-parameter space.     

Effect of partially polarized amplified spontaneous emission noise on Q-factor estimation using optical signal-to-noise ratio

We report on the effect of the partially polarized amplified spontaneous emission noise on the Q-factor estimation by using optical signal-to-noise ratio. The result shows that this effect is negligible even in a long-distance transmission system (number of spans: <40) as long as the polarization-dependent loss per span is smaller than 0.2 dB.     

Optimal loop length of a nonlinear optical loop mirror in switchingsolitons

The optimal loop length of a nonlinear optical loop mirror (NOLM) for switching solitons was investigated numerically for the case where the wavelengths of the control pulse and signal soliton straddle the dispersion zero. In our analysis, the Raman effect is also included because the wavelength difference between the control and signal pulses is within the Raman gainband. It was found that the control pulse not only imposes phase shift on the copropagating signal, but also transfers part of its energy to the signal. Furthermore, the broadening of the control pulse due to the combined effect of self-phase modulation and group velocity dispersion increases the switching power of the control pulse significantly. The broadening of the control pulse also introduces more uniform phase shift to the signal, thus resulting in a higher switching efficiency. Finally, our results show that the pulse distortion is minimal if a loop length equivalent to one soliton period is employed     

Optical sampling oscilloscope using nonlinear fibre loop mirror

An optical sampling system employing the nonlinear loop mirror is described. This enables the display of picosecond pulses on millisecond time scales thus performing the function of an all optical sampling oscilloscope.<>     

A walk-off balanced nonlinear fiber loop mirror switch

We have successfully demonstrated a walk-off balanced nonlinear fiber loop mirror (WBNFLM)-type all-optical switch for 10 Gb/s signal of 1.3-/spl mu/m wavelength with 1.5-/spl mu/m control pulses. This switching scheme, as compared with the conventional types of NFLM, allows the switching speed to go above the limitation imposed by walk-off effects and jitter tolerance to be maximum without degradation of on-off ratio.     

超短行波放大自发辐射的研究

用泵浦能量具有梯度分布的横向同步泵浦方案,产生超短行波自发辐射光脉冲。以N_2激光为泵浦源,获得约50ps的染料光脉冲输出,以锁模Nd:YAG倍频光作泵浦源,获得8～15ps光脉冲。用条纹照相机和光学多道分析器测量了脉冲波形和光谱。 计算机模拟了行波放大自发辐射的瞬态行为,计算结果与实验结果相符合。     

All-normal dispersion fiber lasers mode-locked with a nonlinear amplifying loop mirror

We review our recent progress on the design, modeling and construction of all-normal dispersion Yb-doped fiber lasers mode-locked using a nonlinear amplifying loop mirror. The all-fiber nature of the devices we consider permits accurate numerical simulations with minimal approximations or free-running parameters, and we describe in detail a refined numerical modeling scheme that combines generalized nonlinear envelope equations with analytically simulated gain dynamics. Guided by insights obtained from numerical modeling, we have experimentally realized robust, environmentally stable laser designs that offer flexible operation performance for a wide variety of applications. In particular, the unique all-PM-fiber design makes our devices ideally suitable for industrial laser micromachining applications.     

Spectral filtering using fibre bragg grating embedded sagnac loop mirror

An approach to achieve spectral filtering is proposed, using a fibre Bragg grating (FBG) embedded polarisation maintaining fibre Sagnac loop mirror (SLM) through temperature tuning. The opposite temperature sensitivities of the FBG Bragg resonance wavelengths and the interferometric peaks of the fibre SLM, as well as their pronounced difference in bandwidth, provide an opportunity to realise spectral filtering.     

Picosecond square pulse generation using nonlinear fibre loop mirror

Square pulses with controllable picosecond durations have been generated from a CW input signal in the region of 1.5 mu m by using switching in a nonlinear loop mirror. The square pulses are generated in synchronism with a pulsed driver which can be a noise burst. Shaped pulses have also been derived using this technique.<>     

铜蒸气激光器中的放大自发辐射研究

图1是振荡-放大装置的示意图。振荡器和放大器均由平均输出功率为25W的铜蒸气激光器组成。放电管采用φ=35mm,ι=1100mm的陶瓷管。振荡器采用非稳腔输出,以保证放大器的注入光具有良好的方向性。用一台主脉冲信号发生器发出的信号同时控制二台或     

掺铒光纤自发辐射谱的解析函数

利用980nm半导体激光器作为泵浦源,测量了25cm掺铒光纤的ASE(自发辐射)谱特性,采用L-M(莱文伯-马克特)算法和最小二乘法对实验数据进行拟合,得到了掺铒光纤ASE谱的经验公式。研究结果表明,掺铒光纤ASE谱双峰的中心波长分别为1 530.951和1 555.964nm,R-square(拟合优度)的值达到0.980 72,残差平方和值为4.447 69×10-9。     

Spectral properties of amplified spontaneous emission insemiconductor optical amplifiers

We present a theoretical investigation of the spectral properties of spontaneous emission in semiconductor optical amplifiers. We use an extended (3×3) transfer matrix formalism to derive in the spectral domain an expression for the total longitudinally averaged internal field, which is valid regardless of the levels of optical input and bias current. The material parameters are saturated not only by the monochromatic signal, but also by the amplified spontaneous emission, filtered into the resonance modes of the structure, and integrated over its whole spectral range     

Electrochemical control of amplified spontaneous emission in conjugated polymers

We present a method of electrochemically tuning the threshold intensity of the amplified spontaneous emission (ASE) of a semiconducting polymer thin film. This can be achieved in close contact with a conducting polymer electrode (PEDOT:PSS), if the latter is electrochemically tuned to an optically transparent redox state for the emitted wavelength of interest. This electrical switch between ASE and fluorescence hints that a new route to achieve electrically pumped laser is by combining an electrochemical device with a lasing conjugated polymer.     

染料超荧光的ps研究

用超短光脉冲激励染料溶液,进行超荧光的研究:1.超荧光光谱峰移动和光谱宽度;2.辐射谱精细结构的产生机理。     

Theory and experiment on the amplified spontaneous emission fromdistributed-feedback lasers

The amplified spontaneous emission (ASE) of a strained quantum-well distributed feedback (DFB) laser biased below laser threshold is used to extract the gain and refractive index spectra in a systematic manner. A modified Hakki-Paoli method is used to obtain the gain and differential gain spectra. The refractive index change due to carrier injection is obtained from the shift of the Fabry-Perot peaks in the ASE spectrum. The measured ASE spectrum, gain, refractive index change, and linewidth enhancement factor are then compared with our theoretical model for strained quantum-well lasers. Our model takes into account the realistic band structure and uses the material and quantum-well dimensions directly in the calculation of the electronic and optical properties. The theory agrees very well with the experiment