Simulation of nanosecond square pulse fiber laser based on nonlinear amplifying loop mirror

A nanosecond square pulse fiber laser based on the nonlinear amplifying loop mirror(NALM) is numeri-cally analyzed by the nonlinear Schrdinger equation. The fiber cavity with a NALM has a tendency to provide pulse shaping effect with nonlinearity increasing in the NALM,and the nanosecond square pulse is generated by the pulse shaping effect. The numerical results show that the stable square pulse can be obtained when the parameters of the NALM are chosen appropriately. The generated square pulses have flat top and no internal structure.     

基于多波长类噪声脉冲的掺铒光纤激光器

报道了一种基于多波长类噪声脉冲的被动锁模掺铒光纤激光器。采用980 nm半导体激光器作为泵浦源，2.5 m长的掺铒光纤作为增益介质。锁模机制为非线性放大环形镜(NALM)。通过自相关迹证明输出脉冲为类噪声脉冲。该类噪声脉冲的光谱3 dB带宽可达17.2 nm，边模抑制比为47.7 dB，重复频率为5.434 MHz，单脉冲能量为7.9 nJ。为了实现平坦的多波长输出，在NALM结构中加入Sagnac环干涉仪，获得了最大波长数为5的平坦多波长类噪声脉冲，平坦度为1.995。     

非线性放大环形镜“8”字腔光纤激光器实验研究

使用976 nm半导体激光器作为抽运源,对利用非线性放大环形镜（NALM）锁模运行的掺Yb3+光纤激光器进行了实验研究,获得了脉冲宽度43.6 ps,中心波长为1053.3 nm的锁模脉冲激光输出, 光谱宽度8 nm, 输出功率为0.2 mW, 重复频率为18.2 MHz, 经过放大, 通过光栅对腔外色散补偿,在腔外产生了宽度616 fs的脉冲激光.     

高消光比掺Yb3+锁模脉冲光纤激光器研究

报道了使用976 nm半导体激光器作为抽运源,利用非线性放大环形镜(NALM)锁模运行的掺Yb3+光纤激光器的实验研究.采用偏振相关隔离器代替偏振无关光隔离器、保偏光纤耦合器代替普通单模光纤耦合器,得到了高消光比的锁模脉冲输出,重复频率13.46 MHz,光谱宽度约2 nm,消光比高于25 dB.     

Low-power,phase-preserving 2R amplitude regenerator

We propose a modification of a NALM-based 2R regenerator of phase-encoded signals which operates at considerably lower input powers than was studied earlier. Our modification consists of replacing the core-matched and lossless fiber coupler in the NALM by a coupler with a propagation constant mismatch and loss asymmetrically distributed between the two cores. The performance of the modified regenerator and the one studied earlier is approximately the same.     

Analysis on the effect of nonlinear polarization evolution in nonlinear amplifying loop mirror

By considering the cross phase modulation (XPM) between the two orthogonal poparization components,the nonlinear birefringence and nonlinear polarization evolution (NPE) in highly-nonlinear fiber (HNLF),as well as the unequal evolutions of the state of polarization (SOP) between the clockwise (CW) and counter-clockwise (CCW) waves in a nonlinear amplifying loop mirror (NALM) are analyzed. It is pointed out that the traditional cosine expression is no longer valid for the power transmission of NALM due to uncompleted interference under the high power condition. The analytical expression considering NPE effect is derived, and the experimental result is presented.     

高速OCDM系统中的全光阈值技术分析

分析了高速OCDM系统中基于非线性光学环境(NOLM)和非线性放大(NALM)环境的全光阈值技术。考虑了NOLM环境输入脉冲峰值功率对其阈值判决功能的影响,数值模拟了由高非线性光纤构成的NOLM和NALM环境的脉冲整形和旁瓣抑制功能,并和实验结果进行了比较。结果表明基于NOLM和NALM环境的全光阈值技术都能有效地抑制40 Gbit/s的OCDM系统中的干扰噪声,最优的NOLM环境的脉冲峰值输入功率为2 W,而NALM环境只需要mW量级的脉冲峰值输入功率即能够更好地抑制干扰噪声。     

基于超结构光纤光栅和非线性放大环镜的OCDM系统

实验研究了基于超结构光纤布喇格光栅的40 Gbit/s×2的光码分复用系统,利用非线性放大环镜对系统解码输出脉冲进行了整形和噪音抑制.在非线性放大环镜非线性开关特性的作用下,解码输出脉冲的宽度由7.7 ps压缩至3.6 ps,干扰噪音得到了有效地抑制,实验中环镜的输入功率约为6 mW.结果表明,采用非线性放大环镜能够提高超结构光纤光栅光码分复用系统的性能,这种有效抑制噪音的高速全光编解码还可以应用于光标签交换网络.     

A self-consistent model for a SOA-based fiber ring laser including the mode-locked pulse properties

In this paper, we present a self-consistent model of an optically mode-locked semiconductor fiber ring laser. The fiber laser uses a semiconductor optical amplifier (SOA) as the gain medium, while mode-locking is achieved by its gain modulation, via an external optical pulsed signal. We solved the model analytically developing a novel technique, where we have assumed double saturation of the SOA by both the mode-locked and the externally introduced pulsed signal. The study revealed the locus of the laser parameters to achieve mode-locking. In particular, it was found that SOA gain and energy of the externally introduced signal are two critical parameters that must simultaneously set properly for exact mode-locking. Another outcome of our analysis is that the study of the chirp parameter should be carried out keeping the nonlinear terms of the SOA gain. We have also investigated a slightly detuning regime of operation that revealed a fast change of the mode-locking process.     

All-fiber actively Q-switched fiber laser tuned by a pair of temperature controlled fiber Bragg gratings

We report an all-fiber actively Q-switched erbium-doped fiber laser, where the linear laser cavity mirrors are composed of two fiber Bragg gratings (FBGs). The laser oscillation wavelength could be tuned by this pair of temperature controlled FBGs. The Q-switching is achieved by an all-fiber phase modulation device. Using this system, we could obtain stable Q-switched laser pulses output, which could be optimized by tuning the reflection wavelengths of the two FBGs to be adjacent to each other. Instead of being modulated by the FBG filter in high-speed oscillation, this fiber laser system is operating in the Q-switched regime using an all-fiber phase modulator, producing a more stable laser output spectrum.     

Period-control and chaos-anti-control of a semiconductor laser using the twisted fiber

A novel semiconductor laser system is presented based on a twisted fiber.To study the period-control and chaos-anticontrol of the laser system,we design a type of optic path as a control setup using the combination of the twisted fiber and the polarization controller while we present a physical dynamics model of the delayed dual-feedback laser containing the twisted fiber effect.We give an analysis of the effect of the twisted fiber on the laser.We use the effects of the delayed phase and the rotation angle of the twisted fiber and the characteristics of the system to achieve control of the laser.The laser is deduced to a stable state,a double-periodic state,a period-6 state,a period-8 state,a period-9 state,a multi-period state,beat phenomenon,and so on.The periodic laser can be anti-controlled to chaos.Some chaos-anti-control area is found.The laser system is very useful for the study of chaos-control of the laser setup and the applications of some physics effects.     

Channel spacing-tunable sampled fiber Bragg grating by linear chirp and its application to multiwavelength fiber laser

We theoretically investigated the two methods for densifying the channel spacing of sampled fiber Bragg gratings (SFBGs), the multiple-phase-shift (MPS) method and the linear chirp method, and found that the two methods have similar principle and ability, although the chirp method has an advantage that the tuning of channel spacing is easier. Then we realized channel spacing-tunable SFBGs by use of deformation of ring and S-bend structures by 2- and 3-folds. Finally, we applied the chirp method to realize a wavelength spacing-tunable multiwavelength fiber laser.     

Monolithic fluoride-fiber laser at 1480 nm using fiber Bragg gratings

We report what we believe is the first monolithic fluoride-fiber laser making use of fiber Bragg gratings written directly in the doped fluoride-fiber core. The Tm(3+):ZBLAN fiber laser is upconversion pumped at 1070 nm and emits at 1480 nm. Using two different all-fiber cavities, we observed a threshold as low as 75 mW and a conversion efficiency of up to 40% with respect to launched pump power.     

1018 nm短波长掺镱光纤激光高功率自组织相干合成

搭建了两台高功率、低量子损耗的1018 nm短波长掺镱光纤激光器,进行了全光纤结构下两路光纤激光器的相干合成实验。获得了功率为55 W、合成效率为90.2%的相干输出,这是当前严格单模1018 nm光纤激光器的最高功率水平。同时,验证了Michelson腔自组织相干合成技术能够实现光纤激光器的高功率单模输出。     

Dual-wavelength continuous-wave cascade oscillation at 3 and 2 mum with a holmium-doped fluoride-glass fiber laser

We have demonstrated dual-wavelength continuous-wave oscillation at 3 and 2 mum with a Ho-doped ZrF(4)- BaF(2)- LaF(3)- AlF(3)- NaF fluoride-glass fiber laser by use of a cascade oscillation scheme. We have shown that the fiber laser operates with a high slope efficiency of 52% (at 3 and 2microm) with respect to the absorbed pump power. With a 6.5-m-long fiber we achieved an output power of 90 mW at each of the wavelengths that was limited only by the pump power, and the 3-microm output power is to our knowledge higher than any previously reported level with 3-mum Ho(3+) -doped fiber lasers.     

Vector soliton fiber lasers

We show by simulations that a nonlinear optical loop mirror with birefringent fiber can have intensity-dependent transmission of vector soliton pulses with a 50/50 coupler. Using this result we propose two mode-locked laser cavity designs.     

Binding widely-separated pulses with a passively mode-locked Yb-doped double-clad fiber laser

We have investigated the generation of widely-separated bound pulses with a high power passively mode-locked Yb-doped double clad fiber laser. We report on the emission of bound pulses of 5 ps whose separation can exceed 180 ps. Pulses are further compressed extra-cavity to 140 fs, leading to pulse separations that can reach approximately 1300 pulse widths, while pulses remain bound. Scenarios leading to these regimes are detailed. RF analysis shows an important reduction of the amplitude noise of the laser when pulses bind together. Finally, we report on a new regime of multiple pulse emission of this fiber laser: stable co-emission of a single-pulse and a pair of bound pulses in the same cavity round trip. PACS 42.55.Wd; 42.65.Re     

Emission Dependence on Length in a 1.48-mum Pumped Erbium-Doped Laser with an All-Fiber Configuration

We report a study on the main features of a 1.48-mum pumped erbium-doped fiber laser, such as threshold pump power, output power, and slope efficiency. In particular we have focused on its dependence on active fiber length. We employed an all-fiber laser configuration, which included mirrors directly coated onto the polished fiber endfaces. Launched pump power and laser output power were introduced and extracted, respectively, from the laser cavity by means of couplers. Our measure ments show the existence of an optimum erbium-doped fiber length, where threshold power reaches minimum and output power maximum.     

Multiple-Output Fiber-Ring Lasers and Amplifiers in a Hybrid CATV and ADSL Broadcasting Optical Fiber Communication System

In this article we propose two kinds of new fiber ring structure with a semiconductor optical amplifier. The first structure is a one-fiber-ring amplifier with an 8 × 8 fiber coupler and a semiconductor optical amplifier (SOA). The second fiber ring structure is a two-fiber-ring laser including an 8 × 8 fiber coupler, a 2 × 2 E/O modulator, and an SOA. The 14-output spectra of the fiber laser are measured. The gain coefficients of each port of the multiple-output-fiber-ring amplifiers are also measured. We apply these two kinds of fiber ring structures in a hybrid CATV and ADSL broadcasting optical fiber communication system. This application can develop a broadcasting system with large coverage area without using many laser diodes and optical amplifiers. The performance of such a system is also analyzed in this article.