Multiwavelength lasers based on semiconductor optical amplifiers

Stable multiwavelength lasing is demonstrated with a novel laser, in which a semiconductor optical amplifier offers optical gain and cascaded sampled fiber gratings serve as a comb filter. Five lasing lines are obtained with a fixed wavelength spacing of 0.8 nm. Optical power fluctuations among the lasing lines are improved by adjusting the reflectivity profile through the cascade of two sampled gratings     

Tunable multiwavelength Brillouin-erbium fiber laser with a polarization-maintaining fiber Sagnac loop filter

We demonstrate the generation of 12-wavelength comb with 14.5-nm tunable range in the Brillouin-Erbium fiber laser. This is achieved through tuning the gain profile of Erbium-doped fiber by a Sagnac loop filter with 18-cm polarization-maintaining fiber, in conjunction with modifying the wavelength of Brillouin pump. The experiment also demonstrates that the tunable range is closely equal to the 3-dB bandwidth of Sagnac loop filter due to its periodic transmission profile. Meanwhile, the effect of the 980-nm pump on the tunable multiwavelength generation is investigated. The power of 980-nm pump has a great effect on the wavelength number and the output power of the generated multiwavelength comb, but little on the tunable range. This technique may be applicable to multiwavelength operation lasers with a large tunable range.     

Two Different Operation Regimes of Fiber Laser Based on Nonlinear Polarization Rotation: Passive Mode-Locking and Multiwavelength Emission

We have proposed and demonstrated a nonlinear polarization-rotation-based fiber laser with two different operation states: passive mode-locking and multiwavelength emission. The intensity-dependent transmission or loss induced by nonlinear polarization rotation accounts for the distinct operation regimes. Our experiment results indicate that both passively mode-locked pulses and continuous-wave multiwavelength can be generated from the same fiber laser just through adjusting polarizations. Another characteristic of the current multiwavelength laser is that the used periodic filter is a birefringence fiber filter, which facilitates all-fiber integration of the fiber laser, so it is a potential multifunction laser source with all-fiber configuration and convenient manipulation.     

用于多波长激光器功率均衡的光纤光栅的理论研究

基于半导体光放大器的多波长激光器输出的激光普遍存在功率不均衡的问题 ,文中提出了一种采用光纤光栅梳状滤波器对其进行均衡的方法 ,并给出理论设计步骤及参数选取。结果表明 ,与自由振荡时相比 ,加入所设计的光纤光栅后 ,激光器可实现多路波长间隔稳定的激光输出 ,其功率获得了很好的均衡     

采用双Sagnac环滤波器的可切换多波长光纤激光器

提出了一种基于双Sagnac环滤波器的可切换多波长掺铒光纤激光器,该滤波器由基于保偏光纤和少模光纤的Sagnac环并联构成,结构简单,利用其梳状滤波特性,实现了掺铒光纤激光器的多波长输出。采用传输矩阵法详细分析了双Sagnac环的传输特性,进一步搭建了线性腔掺铒光纤激光器,实验中通过调节偏振控制器,改变腔内偏振态,在室温下得到稳定可切换的单、双、三波长激光输出,且激光器输出波长的位置可调。研究结果表明,输出激光波长的边模抑制比大于34 dB,稳定性测量中波长漂移量小于0.05 nm,具有良好的稳定性,可应用于波分复用及全光通信系统等领域。     

Stable and high-performance multiwavelength erbium-doped fiber laser based on fiber delay interferometer

In this paper, we proposed a novel scheme to realize the multiwavelength erbium-doped fiber lasers. By adding a length of dispersion shifted fiber (DSF) in the ring cavity, we can suppress the cavity mode competition resulting from homogeneous line broadening (HLB) effect. In addition, a comb filter based on fiber delay inter-ferometer (DI) is used for frequency selecting. To enhance the extinction ratio while maintaining the free space range (FSR), the proposed isolator-assisted double-pass DI is utilized into the laser cavity, and a stable 7-wavelength simultaneous lasing spaced at 21.5GHz is accordingly achieved with an extinction ratio of higher than 40 dB. The lasers are stable with a maximum power fluctuation per channel of less than 0.6 dB during an hour test.     

基于啁啾光纤光栅的五波长掺铒光纤激光器

提出并实验验证了一种新型的基于啁啾光纤光栅的全光纤的可切换的五波长掺铒光纤激光器,该激光器采用简洁的线性腔结构,使用一段高掺铒的光纤作为增益介质,利用一个内含宽带啁啾光纤光栅的萨格纳克环作为激光器的谐振腔腔镜,担当了一个梳状滤波器的作用,另一个腔镜由一个宽带光纤反射镜担当,适当调整环中的偏振控制器,可以获得最多五波长的激光输出,并具有4种不同的激光输出模式,所有激发线均具有大于32 dB的光学信噪比,小于0.6 nm的线宽以及小于8 dB的峰值功率差异。     

Tunable multiwavelength fiber ring lasers using a programmable high-birefringence fiber loop mirror

We demonstrate a comb filter with digitally tunable wavelength spacing using a programmable high-birefringence (HiBi) fiber loop mirror (FLM). We then use the HiBi-FLM to implement a tunable multiwavelength semiconductor optical amplifier (SOA)-based fiber ring laser and a tunable multiwavelength all-fiber Raman ring laser. Both lasers exhibit stable room-temperature operation and have a wavelength spacing that is digitally tunable between 1.6 and 3.2 nm. With the SOA-based configuration, we obtain six wavelengths with a spacing of 3.2 nm and 11 wavelengths with a spacing of 1.6 nm; with the all-fiber Raman-based configuration, we obtain four wavelengths with a spacing of 3.2 nm and five wavelengths with a spacing of 1.6 nm.     

Multiwavelength generation in an erbium-doped fiber laser using in-fiber comb filters

Simultaneous continuous wave multiwavelength operation of an erbium-doped fiber laser has been demonstrated using two types of recently developed in-fiber grating comb filters. The lasing wavelengths and linewidths were determined by the comb filter, which was inserted in a ring cavity with a single inhomogeneously broadened gain medium.     

基于萨格纳克环与光栅的双波长光纤激光器

报道一种基于保偏光纤的萨格纳克环与级联的光纤布拉格光栅的双波长掺铒光纤激光器,该激光器采用简单的线性腔结构,所用的萨格纳克环担当了梳状滤波器,光栅组构成了波长选择器件;在偏振烧孔的作用下,通过调整偏振控制器,激光器能够输出5种不同的激发模式,其中,双波长2种,单波长3种;所有的激发线具有小于0.3nm线宽,大于24dB的光学信噪比;同时,该激光器展示了较好的波长与峰值功率稳定性.     

Multiwavelength generation in a Raman fiber laser with sampled Bragg grating

Simultaneous continuous-wave multiwavelength operation of a Raman fiber laser is demonstrated with sampled Bragg grating (SBG) at room temperature. The characteristics of multiwavelength fiber ring laser can be easily controlled by adjusting the parameters of the SBG, including the sampling period and the sampling length. In the proposed fiber laser, stable four oscillating wavelengths with 100- and 50-GHz spacing has been achieved, respectively, as well as five oscillating ones with a wavelength spacing of only 25 GHz by varying the sampling period of the SBG.     

Multiwavelength erbium-doped fiber Fabry-Pe/spl acute/rot laser and its uniform spectral lines power operation

Multiwavelength erbium-doped fiber laser by means of phase modulation in a linear cavity configuration is presented. Stable multiwavelength lasing is achieved by applying any one of the waveforms of sine, square, sawtoothed, and triangular at a suitable frequency between 500 Hz to a few tens of kilohertz to the phase modulator. The output spectral lines power equalization is performed by adjusting the frequency to drive the all-fiber phase modulator and the polarization controller or dc offset voltage of a LiNbO/sub 3/ amplitude modulator, which is incorporated in a polarization-maintaining fiber Lyot-Sagnac filter.     

Waveband-switchable SOA ring laser constructed with a phase modulator loop mirror filter

An electrically tunable multiwavelength source has been developed using a birefringence-based optical comb filter in a semiconductor optical amplifier ring laser. The filter is constructed with an electrooptic phase modulator placed inside a fiber loop mirror. By controlling the birefringence of the modulator through the applied bias, the radio-frequency power, or the modulation frequency, we achieve a continuous shift of the spectral comb to access different interleaved wavebands. Electrical waveband switching has been successfully demonstrated for 21 wavelengths at 100-GHz grid spacing with an optical signal-to-noise ratio over 40 dB.     

High-power multiwavelength Er/sup 3+/-Yb/sup 3+/ codoped double-cladding fiber ring laser

A high-power simultaneous multiwavelength lasing in an Er/sup 3+/-Yb/sup 3+/ codoped double-cladding fiber (EYCDF) ring laser is demonstrated based on a wavelength-dependent filter through spatial mode beating within the multimode fiber section. We have investigated the relationship between the lasing wavelengths and the length of the EYCDFs. The experimental results indicate that both the number of lasing wavelength lines and the spacing between two adjacent lasing lines can be controlled by the changes of the lasing light polarization states.     

Single-longitudinal-mode multiwavelength fiber ring laser

A single-longitudinal-mode multiwavelength fiber ring laser is proposed and demonstrated. The single-longitudinal-mode operation is realized using a fiber loop mirror with a saturable absorber. The fiber loop mirror acts as a passive self-tracking narrow multiband optical filter. Single-longitudinal-mode multiwavelength lasing is generated by using either a Lyot-Sagnac filter or a fiber grating array.     

基于NPR效应及NOLM的多波长SOA光纤激光器

为了获得具有超窄波长间隔的稳定多波长输出,设 计并实验验证了一种基于非线性偏振旋转(NPR)效应及NOLM的多波长SOA光纤激光器。利用 SOA的NPR效应,将SOA与其他偏振器件组合引起强度相关损耗(IDL)效应,从而抑制SOA均 匀加宽线宽内的模式竞争,实现稳定的多波长输出。Lyot-sagnac滤波器作为波长选择器件 ,选用71 m长保偏光纤(PMF)得到超窄波长间隔。另外NOLM作为功率 均衡器进一步抑制了模式竞争效应并且实现了功率均衡,提高了边模抑制比(SMSR)。通过调 节偏振控制器(PCs),最终在室温下实现了稳定且功率均衡的多波长输出,10 dB带宽内输出的波长数量为184,波长间隔为0.08 nm,SMSR高达22 dB。该激光器可作为DWDM光通信系统 中的光源。     

一种线形腔的多波长布里渊掺铒光纤激光器

布里渊掺铒光纤激光器(BEFL)是一种利用非线性效应——布里渊散射来实现多波长输出的激光器,波长间隔大约为0.088 nm(11 GHz).研究了一种多波长布里渊掺铒光纤激光器线形结构,通过引入反馈实现多波长输出.在布里渊泵浦功率为11 mW,980 nm泵浦功率为12 mW时获得了波长间隔为0.08 nm的34个波长的激光输出以及1 525～1 570 nm可调谐范围.并通过调节980 nm抽运光功率以及布里渊泵浦光波长,实现了可调谐的多波长输出.还研究了980 nm抽运光功率对产生的斯托克斯光波数的影响.     

Acousto-optic-induced cladding-mode reflection in a blazed-superstructure fiber grating

The coupling phenomenon between the cladding mode and the core mode in a blazed-superstructure fiber grating is experimentally demonstrated in this letter by applying both transverse and longitudinal acoustic waves. This is based on the difference between the cladding-mode wave vector and the core-mode wave vector, which is equivalent to the acoustic wave vector. By this means, a reflectivity-tunable multiwavelength switchable comb filter would be developed for the applications in fiber optics.     

基于光纤拉锥及相位调制的可切换多波长掺铒光纤激光器

研究了一种全光纤可切换多波长掺铒光纤激光器。该激光器利用一段缠绕在压电陶瓷上的单模光纤作为正弦相位调制器以及基于光纤拉锥的马赫-曾德尔干涉仪作为梳状滤波器,抑制由于掺铒光纤的均匀展宽效应引起的模式竞争,从而避免了在室温下不稳定的单波长激射,实现了多波长掺铒光纤激光器的稳定输出。实验中观察到稳定的5个波长的同时激射,相邻波长间隔为0.804 nm。信噪比大于40 dB,3 dB带宽约为0.023 nm,中心5个波长输出功率的平坦度为14 dB。同时,激光器具有灵活的波长可切换特性,通过调整驱动信号和偏振控制器的状态,实现了单波长、双波长、三波长以及更多波长的输出。该激光器可应用于大容量波分复用系统和光纤传感。     

一种基于取样光栅的Sagnac环滤波器的设计研究

为了探究更多新结构的梳状滤波器,采用了一种新型的基于取样光栅的Sagnac环滤波器的设计方案。利用Jones矩阵理论,建立了该滤波器的理论模型,并对其传输光谱进行了分析和数值仿真。通过选取不同的光纤光栅的长度L、光纤环臂差L和取样周期P等参量的值,可以得到6种具有分立谱线、高反射率、等间隔的窄带梳状透射谱,且具有良好的波长选择性和信道隔离度。结果表明,这种滤波器可应用于波分复用系统的多通道窄带滤波器、双波长的光纤激光器和分布式传感系统等,对结合光纤光栅和Sagnac环结构的滤波器的研究和应用提供了一定的参考。