利用自相位调制效应测量微结构光纤的非线性系数

报道了利用光纤中的自相位调制(SPM)效应对微结构光纤的非线性系数进行测量的实验.实验中采用半导体激光器作为脉冲光源,输出宽度为1.6 ps的双曲正割型脉冲,经掺铒光纤放大器(EDFA)放大后进入80 m的色散平坦微结构光纤,由于自相位调制效应,出射光谱得到展宽.通过测量输入微结构光纤的脉冲峰值功率和输出光谱,可以计算得到微结构光纤的非线性系数.该测量方法简单、准确,实验测量值与光纤的标称值误差小于1%.     

The compression of optical pulses using self-phase-modulation andlinearly chirped Bragg-gratings in fibers

We report the first demonstration of pulse compression in optical fiber using linearly chirped Bragg gratings as quadratic compressors for pulses spectrally broadened by self-phase modulation. With the system investigated an initial 2 ps, bandwidth limited pulse is compressed by a factor of >10. The experimental results are found to be in good agreement with analytical and numerical calculations. Such a system allows high quality compression of pulses in optical fiber for the first time     

Tapered photonic crystal fiber for supercontinuum generation in telecommunication windows

We numerically studied supercontinuum generation in a tapered photonic crystal fiber with flattened dispersion properties.The fiber was weakly tapered to have normal dispersion at wavelengths around 1.55 μm after a certain distance.We pumped 4 ps pulses with low peakpower and found that flatly broadened, wideband supercontinuum was generated in telecommunication windows.Furthermore, we also demonstrated the effects of tapered length and pulse width of the pump pulse on supercontinuum generation.     

利用光子晶体光纤实现10 Gb/s光传输系统的色散补偿

利用光子晶体光纤（PCF）在10Gb/s光传输系统中对普通单模光纤中传输的光脉冲进行了色散补偿，获得了很好的补偿效果。实验中，10Gb／s光脉冲序列经过2.163km普通单模光纤被展宽后．利用26m长光子晶体光纤对其进行色散补偿．补偿后脉冲基本恢复到了初始形状。进一步的理论计算表明，此光纤在C波段20nm波长范围内对普通单模光纤能够实现较好的色散斜率补偿，补偿后剩余色散小于5ps／nm。理论与实验结果表明光子晶体光纤在色散补偿方面具有很大的潜力．在未来光通信系统中将发挥重要作用。     

Dispersion compensation of 16 ps pulses over 100 km of step-indexfibre using cascaded chirped fibre gratings

The propagation of 16 ps data pulses over 100 km of step-index fibre using two cascaded chirped fibre gratings to achieve dispersion compensation is presented. At the output, the pulses are broadened slightly to 20 ps, indicating the potential for 50 Gbit/s operation     

Intensity effects on the stimulated four photon spectra generated by picosecond pulses in optical fibers

The intensity dependence of stimulated four photon mixing (SFPM) spectra generated in 15 m of a 4-mode optical fiber by 25- ps pulses has been investigated. Despite the shortness of pulses, the SFPM conversion was highly efficient due to the intrinsic phase matching condition. In addition to usual features of SFPM spectra generated by nanosecond pump pulses, picosecond SFPM spectra were broadened by self phase modulation (SPM) and cross phase modulation (XPM). At the highest pump powers, intensity saturated frequency continua, arising from the combined effects of SFPM, stimulated Raman scattering (SRS), SPM, and XPM were generated all over the visible spectrum.     

采用啁啾光纤光栅补偿带啁啾的超高斯脉冲在光纤中传输的色散

利用啁啾光纤光栅,对带啁啾的超高斯脉冲的色散补偿特性进行了理论分析和数值模拟。数值模拟结果表明,光脉冲在普通单模光纤中传输了一定距离后,由于色散的作用,脉冲发生展宽,超高斯脉冲比高斯脉冲展得更宽。若初始脉冲含有啁啾,展宽后的脉冲还出现小调制。用啁啾光纤光栅进行色散补偿后,高斯型脉冲能够较好的恢复初始脉冲形状,带啁啾的超高斯脉冲的脉宽可恢复到接近初始脉冲的宽度,但脉冲形状发生了畸变,并出现了旁瓣,脉冲峰值功率与超高斯脉冲阶数和啁啾参数有关。     

亚皮秒电脉冲的产生及其在槽线上的传输特性

采用了飞秒光电导相关技术首次在以低温生长砷化镓(LT-GaAs)为衬底材料的槽线电极结构上产生亚皮秒电脉冲,并对其脉宽与传输特性进行了测量研究,得到电脉冲初始的半高全宽(FWHM)约为0.7ps,传输速度约为真空中光速的1/2.3倍;观察到电脉冲在传输过程中的强度衰减和脉冲的增宽,其衰减系数为20dB/mm,并测得脉冲传输至420后展宽至2.86ps.实验测量值与理论预期值相符.     

540 fs light pulses at 1.5 μm with variable repetition rateusing a tuneable twin guide laser and soliton compression in adispersion decreasing fiber

A novel and simple method to generate ultra short light pulses with variable repetition rate is demonstrated. A wavelength modulated tuneable twin guide laser, emitting blue-chirped light, together with pulse compression in a standard single mode fiber is used to generate light pulses of 3 ps width. Amplification and further compression in a dispersion decreasing fiber leads to Fourier transform limited pulses of 1.87 ps width or to 540 fs pulses with a small pedestal     

Temporal and spectral characteristics of rapidly gain-switched GaAs/GaAlAs buried-heterostructure lasers

The temporal and spectral output of GaAs/GaAlAs buried-heterostructure lasers under excitation with 60 ps electrical pulses is investigated for different DC bias conditions. Optical pulses comparable in width to the electrical pulses can be obtained only if the DC bias is below or close to threshold, where multimode emission is observed. For DC bias well above threshold the laser remains single-mode; however, the optical pulses are considerably broadened.     

Extremely transient pulses from a Brillouin fiber laser

Stable trains of Stokes pulses with the unusually short duration of ≈200 ps were obtained, using a simple Brillouin fiber ring laser with standard single-mode, Ge-doped fiber. They were achieved by confining the fiber in the resonator, which resulted in reduced threshold and increased output power. This threshold reduction nontrivially allowed substantially shorter pump pulses (500-100 ps) to be used, and, as a result, extremely short Stokes pulses were generated     

Competition of Rational Harmonic Mode-Locking and Continuous-Wave Lasing in Semiconductor Optical Amplifier Fiber Laser Under Optical Pulse Injection

Twentieth-order rational harmonic mode-locking (RHML) semiconductor optical amplifier fiber laser (SOAFL) pulses are demonstrated by using 1-GHz backward dark-optical comb injection. Maximum frequency detuning range of plusmn 300 Hz, broadened pulsewidth of 35 ps, and highest average power of 0.4 muW for twentieth-order RHML-SOAFL pulse are characterized. The extraordinary phenomena on the red-shifted wavelength from 1535.5 to 1541.5 nm and the corresponding spectral linewidth reduced from 12 to 3 nm are observed with the RHML order increasing to 8 or higher. Such a less pronounced RHML mechanism at higher orders occurred in the optically injection mode-locked SOAFL is mainly attributed to the weak mode-locking strength at high RHML orders as compared to continuous-wave lasing mechanism.     

4 Gb/s soliton data transmission over 136 km using erbium dopedfiber amplifiers

The use of semiconductor-laser-pumped erbium-doped fiber amplifiers and an externally modulated mode-locked external-cavity semiconductor laser to obtain soliton data transmission at 4 Gb/s over 136 km of nondispersion shifted fiber is described. After 136 km of transmission and at low pulse powers, the ~80 ps fiber input pulse width was broadened to ~150 ps. At high pulse powers the output pulse width was maintained at 80 ps, as expected for N=1 solitons. N =3 solitons were also observed at lower data rates     

色散补偿法获得5GHz,6.8ps超短光脉冲

利用色散位移光纤压缩从１．５５μｍ增益调制ＤＦＢ激光器中出射的红移啁啾光脉冲。在最优光纤压缩长度下，光脉冲宽度由４２．６ｐｓ压缩至６．８ｐｓ，压缩比为６．３     

光脉冲色散展宽的光纤光栅透射补偿

分析讨论了利用变迹均匀光纤光栅的透射色散对光纤中传输的脉冲色散展宽进行压缩补偿。给出了啁啾高斯脉冲的补偿原理,计算了相关的曲线和光纤光栅的相应参数。通过选择光纤光栅的不同参数,可以使色散展宽的高斯脉冲经光栅后几乎完全恢复原状或受到进一步压缩。     

偏振模色散补偿的实验研究

实验研究了高斯脉冲在PMD系数为225Ps／km^1/2的光纤中传输,发现超高的偏振模色散引起脉冲分裂,并用基模的两正交偏振分量耦合走离解释了脉冲分裂的成因．用PSP法实验研究了超高PMD的补偿,使输入光脉冲的偏振态对准光纤的偏振主态,可以大大减弱光纤PMD对传输信号的影响。     

Correlated and uncorrelated timing jitter in gain-switched laserdiodes

The author describes correlated and uncorrelated timing jitter of gain-switched pulses generated from sinusoidally modulated laser diodes measured from photocurrent power spectra. It is found that if dc bias is decreased to obtain shorter pulses, then the root-mean-square (rms) value of uncorrelated timing jitter drastically increases to more than 2 ps, while correlated jitter remains constant at the drive circuit level of ~0.2 ps. By optimizing the bias condition and compression fiber length, total timing jitter of gain-switched pulses can be reduced to as low as ~0.5 ps, as their pulse width is kept less than 10 ps     

Generation of 2.5-ps light pulses with 15-nm wavelength tunabilityat 1.3 μm by a self-seeded gain-switched semiconductor laser

The generation of 2.5-ps pulses by a Fabry-Perot semiconductor laser with 15-nm wavelength tunability is demonstrated. A commercial laser is switched to single longitudinal mode pulse emission by self-seeding, using an external grating. The sidemode suppression ratio is better than 15 dB, with a peak value of 21 dB. The linearly red chirped pulses are compressed from 21-30 ps to 2.5-3.5 ps in a dispersion-shifted fiber. The simple experimental setup consists of a fiber coupler, a grating, and the dispersion-shifted fiber     

Flatly broadened supercontinuum generation at 10 Gbit/s using dispersionflattened photonic crystal fibre with small normal dispersion

Supercontinuum generation at 10 Gbit/s using a nonlinear dispersion-flattened photonic crystal fibre is experimentally demonstrated. The fibre has small normal dispersion with a variation smaller than 1.5 ps nm^-1 km^-1 between 1500 and 1650 nm. The supercontinuum with a flatly broadened spectrum of 92 nm (at 6 dB) in the 1.55 mum region is generated by injecting 1545 nm, 1.5 ps optical pulses into an 80 m-long fibre     

Generation of pedestal-free 22-fs ultrashort pulse using highly nonlinear fiber and reverse-dispersion fiber

We present an all-fiber system for generating pedestal-free 22-fs ultrashort pulses with a single-peak spectrum. High-power Raman soliton pulses and a normally dispersive highly nonlinear fiber are used to generate a smooth, broadened single-peak spectrum. Then, the higher order dispersion is compensated for using a hybrid fiber composed of a reverse-dispersion fiber and a standard single-mode fiber, which allows pedestal-free ultrashort pulses to be successfully generated. To our knowledge, this is the first demonstration of pedestal-free 20-fs-class ultrashort pulse generation without spectral distortion using an all-fiber configuration.