Ultralong dispersion-shifted erbium-doped fiber amplifier and itsapplication to soliton transmission

Distributed, dispersion-shifted erbium-doped fiber amplifiers with doping concentrations as low as 0.1-0.5 p.p.m. (0.1-0.5×10^-4 wt.%) were fabricated and their grain characteristics studied for the purpose of soliton amplification. A 9.4-km dual-shape-core-type amplifier with a 0.5-p.p.m. concentration had a gain of more than 20 dB at 1.535 μm and 10 dB at 1.552 μm with a forward pumping configuration, and it could successfully amplify and transmit a 20-ps soliton pulse train at a 2.5-GHz repetition rate. The soliton transmission characteristics of an 18.2 km long fiber amplifier were studied using backward and forward pumping. It was found that A=1.5 soliton pulses with a pulse width of 20 ps could be amplified over 18.2 km at a repetition rate of 5 GHz, where soliton narrowing to 16 ps was observed     

Application of a λ/4-shifted DFB laser/electroabsorptionmodulator monolithically integrated light source to single-chip pulsegenerator with variable repetition rate

The authors have demonstrated the application of a 1.55-μm λ/4-shifted DFB laser/InGaAsP electroabsorption modulator monolithically integrated light source to a single-chip pulse generator with variable repetition rate for soliton transmission for the first time. Quasi-transform-limited pulses with a time-bandwidth product of 0.31 were successfully generated up to 8.6-GHz repetition rates by the sinusoidally driven integrated modulator having high modulation efficiency of 13 dB/V. No change of lasing wavelength was observed in the operation scheme of the integrated device as a pulse generator     

40-GHz pulse train generation using soliton compression of aMach-Zehnder modulator output

We demonstrate 40-GHz soliton pulse train generation using nonlinear compression of the output of a Mach-Zehnder modulator. This source generates transform-limited pulses at twice the RF drive frequency, requires less than V_π drive level, is tunable in wavelength (over the entire EDFA bandwidth), and is tunable in repetition rate     

10-GHz 11.5-ps Pulse Generation From a Single-Mode Gain-Switched InGaAs VCSEL at 1.1 $mu$m

We have successfully generated a 10-GHz 11.5-ps pulse train at 1.1 $mu{hbox {m}}$ by using a gain switching technique with a high-speed and single-mode vertical-cavity surface-emitting laser (VCSEL). The InGaAs-based VCSEL we used had a sidemode suppression ratio of more than 50 dB and a modulation bandwidth of 7.2 GHz. A nearly transform-limited Gaussian pulse was obtained after chirp compensation, and the repetition rate can be increased up to 16 GHz. We also demonstrated a 10-Gb/s return-to-zero data modulation for the generated 10-GHz pulse train.      

石墨烯被动锁模谐波阶数可调的掺铒光纤孤子激光器

采用石墨烯被动锁模的掺Er光纤(EDF)环形腔,获得稳定的谐波阶数可调的孤子脉冲激光。通过调节EDF环形腔中的偏振控制器(PC)改变光腔损耗,实现了锁模谐波从一阶至四阶的可控运转。连续锁模基频重复频率为3.873MHz,中心波长为1 557.6nm,谱线宽度为4.5nm,有明显孤子边带,信噪比(SNR)约为45dB,二、三和四次谐波锁模脉冲重复频率分别为7.745、11.618和15.491MHz。本文的实验结果可用工作于反常色散区锁模激光器的多孤子形成机理来解释。     

Stabilized Phase-Modulated Rational Harmonic Mode-Locking Soliton Fiber Laser

We realized the repetition rate multiplication in a phase-modulated soliton fiber laser with the rational harmonic mode-locking method. A modified pulse phase-locking method is used to stabilize the fiber laser at 10-GHz repetition rate with the rational harmonic order up to five (limited by the component performance). The laser showed an excellent stabilization performance in a long-term bit-error-rate test     

Pulse repetition rate multiplication in fibre laser using higher-order passive modelocking

A simple technique that allows for the repetition rate multiplication of optical pulse trains generated in passively modelocked fibre lasers is experimentally demonstrated. This is achieved by initiating higher-order passive modelocking by using both a dual-channel fibre Bragg grating and a Fabry-Perot filter inside the fibre cavity. Continuous dark pulse trains with a repetition rate of 60-GHz were generated, which is a four-fold multiplication of the Fabry-Perot free spectral range.     

低阈值高稳定性的全保偏锁模光纤激光器

报道了一种基于色散补偿的低阈值自启动的全保偏“9”字腔光纤激光器。在谐振腔结构中加入一段色散补偿光纤进行色散补偿,同时加入相移器提供非线性相移,产生超短脉冲输出。当泵浦功率达到80mW时,可实现自启动的孤子锁模,重复频率为2218 MHz,中心波长为1557nm,脉冲宽度为536 fs,信噪比为73dB。在该稳定锁模状态下的激光器输出平均功率为104mW,对应脉冲能量为0046nJ。该激光器结构简单,具有低阈值、自启动的优势,可作为种子源,广泛应用于太赫兹产生、生物医学成像、超快光谱学等领域。     

Generating 4 20 GHz and 4 40 GHz Pulse Trains From a Single 10-GHz Mode-Locked Laser Using a Tunable Planar Lightwave Circuit

We demonstrate a tunable pulse repetition rate multiplier using a silica-based planar lightwave circuit (PLC). The PLC is a six-stage lattice-form Mach–Zehnder interferometer which can be tuned thermally to generate 20- and 40-GHz output pulse trains from a 10-GHz input. We use a nonlinear optical loop mirror as a wavelength converter to perform intensity-to-field conversion to eliminate pulse-to-pulse phase fluctuations in the higher-rate output pulse trains. Moreover, we use wavelength multicasting (simultaneous wavelength conversion) to generate multiple pulse trains (4$,times,$ 20 GHz and 4$,times,$ 40 GHz in the example shown here) from a single 10-GHz input.      

基于电吸收调制晶体的超短光脉冲产生的数值模拟

数值模拟了基于电吸收调制晶体（ＥＡＭ）的超短光脉冲源的输出脉冲宽度及消光比与外加反向偏压、射频信号幅度之间的变化关系。数值模拟结果表明,在重复率为１０ＧＨｚ情况下,可以获得的最小脉宽约为１３ｐｓ,其消光比大于２０ｄＢ,脉冲波型接近ｓｅｃｈ＾２孤子波型。因此,基于ＥＡＭ的超短光脉冲源可以满足２０Ｇｂ／ｓ的光时分复用（ＯＴＤＭ）系统的需求,也适合于超长距离的光孤子通信系统。     

Gigabit optical pulse generation with FM mode-locked LiNdP4O12lasers

FM mode locking of an LiNdP4O12(LNP) laser with an intracavity modulator is reported. Mode-locked optical pulses with a pulse width of 49 ps at a repetition rate of 960 MHz, corresponding toc/2L(c:light velocity,L:cavity length), have been obtained. A pulse repetition rate as high as 2.88 GHz has been achieved with a multiple mode-locking technique.     

基于微结构光纤的10 GHz超过1100信道的平坦超连续谱光源

报道了一种基于微结构光纤的宽带、平坦超连续谱(SC)光源。利用锁模半导体激光器产生的1.6ps,重复率为10GHz的光脉冲,通过一段80m的色散平坦高非线性微结构光纤(HNL-MF),在1.55μm波长区域产生了谱宽超过100nm的平坦超连续谱。实验中采用的微结构光纤的非线性系数约为11W-1·km-1。光纤具有小的正常色散和平坦的色散特性,在1550nm波长处,光纤的色散值约为-0.58ps·nm-1·km-1,而在1500～1650nm波长范围内,光纤的色散值变化小于1.5ps·nm-1·km-1。实验中获得的宽带、平坦超连续谱在1503～1593nm宽达90nm的波长范围内,具有±2.5dB的平坦度。该宽带、平坦超连续谱能同时提供波长间隔为10GHz,超过1100路的多波长载波信道。通过对光谱滤波,获得了速率为10Gbit/s的多波长脉冲序列。这样的超连续谱光源在波分复用(WDM)光通信系统、光波长变换等方面都有重要的应用。     

80-160-GHz mode-locked fiber ring laser synchronized to external optical pulse stream

The authors present a novel scheme to generate ultrahigh repetition rate picosecond pulses synchronized to an optical pulse stream in an actively mode-locked fiber ring laser. A monolithic Mach-Zehnder interferometer with integrated semiconductor optical amplifiers serves as an 80-GHz optically controlled modulator. 80-GHz transform-limited 2.1-ps Gaussian pulse with low timing jitter, extinction ratios up to 25 dB, and 5 mW of average output power are demonstrated. The laser is wavelength tunable over more than 15 nm around 1555 nm. At 160 GHz, 2.5-ps pulse trains with 3-mW output power are generated by rational harmonic mode locking.     

Compact Nd:YVO/sub 4/ lasers with pulse repetition rates up to 160 GHz

We present a comprehensive study on multigigahertz repetition rate Nd:YVO/sub 4/ lasers, passively mode-locked with semiconductor saturable absorber mirrors. A brief review of Q-switching instabilities with special emphasis on high repetition rate is given. We then present basic design guidelines, and experimentally show that one can push the pulse repetition rate of a Nd: YVO/sub 4/ laser up to 157 GHz, reaching the fundamental limit to the repetition rate which is given by the pulse duration and thus by the amplification bandwidth. We also demonstrate an air-cooled diode-pumped 10-GHz Nd: YVO/sub 4/ laser with 2.1-W average output power and 13% electrical-to-optical efficiency, showing the potential of solid-state lasers generating multiwatt, multigigahertz pulse trains with high efficiency.     

10-GHz 0.5-ps Pulse Generation in 1000-nm Band in PCF for High-Speed Optical Communication

We achieved the first 10-GHz subpicosecond pulses in the 1000-nm band by employing the higher order soliton effect in a 190-m photonic crystal fiber (PCF). We obtained 0.5-ps pulses at 1063 nm by compressing 11-ps pulses from a harmonically mode-locked Yb fiber laser with a 10-GHz repetition rate, which was stabilized with phase-locked-loop technology. This light source is attractive in terms of realizing a hundreds-of-gigabits-per-second optical-time-division-multiplexing transmission over a low-loss PCF in the 1000-nm band     

受激布里渊散射主被动混合调Q光纤激光器

基于瑞利散射和受激布里渊散射(RS-SBS)的被动调Q掺铒光纤(EDF)激光器的输出脉冲序列具有重复频率低、脉宽窄、功率高的特点,适合光时域反射(OTDR)系统对脉冲光源的基本要求,但是输出的脉冲序列不够稳定。提出在被动调Q激光腔中插入声光调制器(AOM)构成主被动混合调Q激光器。实验结果证明,这种混合调Q的方法既保持了声光调制器主动调Q激光器输出脉冲序列重复频率低而且稳定的特点,又发挥了瑞利散射和受激布里渊散射被动调Q机制动态速度快、输出脉冲宽度窄的优势。在120~200 mW的抽运功率条件下,得到的脉冲序列重复频率从30 Hz~90 kHz连续可调,脉冲宽度最小可达20 ns,峰值功率最高可达200 W,脉冲重复频率稳定度优于5%,脉冲幅度起伏不大于10%。脉冲峰值功率和脉冲宽度受抽运功率的影响不大,但随着调制频率增加,脉冲峰值功率降低而脉冲宽度加宽。     

耗散孤子和束缚态脉冲可切换的超连续谱产生

当超短脉冲进入高非线性光纤时,在色散和非线性效应的共同作用下,脉冲频谱中会产生一些新的频率分量,使得输出频谱比输入频谱宽得多。这种光谱被称为超连续谱。超连续谱光源具有光谱范围宽、方向性好、亮度高、空间相干性好等优点。在锁模激光器中,传统孤子、耗散孤子和类噪声脉冲可以作为种子源产生超连续谱。文中,笔者建立了一个NPR被动锁模光纤激光器来产生脉冲激光。然后,添加一段DCF以补偿腔中的色散,从而产生耗散孤子。同时,通过调节腔内PC,可以实现束缚态和耗散孤子的状态切换。输出脉冲经10 m单模光纤压缩后注入部分拉锥后的高非线性光纤以产生超连续谱。实验中,我们得到了脉宽为5.6 ps、重复频率为32 MHz、信噪比为52 dB的耗散孤子锁模脉冲,压缩后的脉冲宽度为868 fs,用作超连续谱产生。超连续谱的覆盖范围约为1200~2200 nm,其20 dB谱宽为357 nm。通过调节偏振控制器,实现耗散孤子脉冲与束缚态脉冲之间的切换,束缚态脉冲持续时间为1.4 ps,脉冲间隔为14 ps,信噪比为51 dB,产生1600~1870 nm的超连续光谱,20 dB的光谱宽度为135 nm。     

高重复率全光纤被动锁模飞秒激光产生研究

报道了高重复频率全光纤被动锁模飞秒激光产生的实验研究,采用全光纤环形腔结构和非线性偏振旋转可饱和吸收被动锁模机理实现了100MHz级掺铒光纤锁模飞秒激光的稳定运转,最高重复频率为99.91MHz,光谱带宽为25nm,中心波长为1570nm,脉宽最短为194fs,实验同时研究了在不同重复频率下的全光纤被动锁模激光器运转动力学特性。研究为高重复频率飞秒光纤激光器在光频梳产生技术中的应用提供了高集成、高稳定超快光源技术途径。     

Wavelength and duration tunable subpicosecond source usingadiabatic Raman compression

A wavelength and pulse duration tunable source of subpicosecond pulses has been demonstrated at a repetition rate of 10 GHz using adiabatic Raman compression of 10 ps pulses from an external cavity laser and an electro-absorption modulator     

2 ns pulse width high repetition rate short cavity acousto-optically Q-switched Nd:YVO/sub 4/ laser

With a specially constructed miniature acousto-optical Q-switch, 2 ns pulses with 10.3 muJ energy and 5.13 kW peak power at 80 kHz repetition rate were obtained in an end pumped short cavity acousto-optically Q-switched Nd:YVO₄ laser. This is believed to be the shortest pulse width obtained in a solid-state laser by acousto-optical Q-switching. At 500 kHz repetition rate, 10 ns pulses were generated