Fabrication and characterization of dye-doped polymer optical fiber as a light amplifier

The fabrication and characterization of a Rhodamine 6G-doped polymer optical fiber amplifier have been carried out. Two different schemes were employed to characterize the optical fiber: the stripe illumination technique to study the fiber as a gain medium and another technique to study its performance as an amplifier. We observed a spectral narrowing from 42 to 7 nm when the pump energy was increased to 6 mJ in the stripe illumination geometry. A gain of 18 dB was obtained in the amplifier configuration. The effects of pump power and dye concentration on the performance of the fiber as an amplifier were also studied.     

Gain and noise figure enhancement of Er+3/Yb+3 co-doped fiber/Raman hybrid amplifier

An Er/Yb co-doped fiber/Raman hybrid amplifier (HA) is proposed and studied theoretically and analytically to improve the gain and noise figure of optical amplifiers. The calculations are performed under a uniform dopant and steady-state conditions. The initial energy transfer efficiency for Er/Yb co-doped fiber amplifier (EYDFA) is introduced, while the amplified spontaneous emission (ASE) is neglected. The glass fiber used for both Er/Yb and Raman amplifiers is phosphate. Different pump powers are used for both EYDFA and RA with 1 μW input signal power, 1 m length of Er/Yb amplifier and 25 km length of Raman amplifier (RA). The proposed model is validated for Er/Yb co-doped amplifier and Raman amplifier separately by comparing the calculating results with the experimental data. A high gain and low noise figure at 200 mW Raman pump power and 500 mW Er/Yb pump power are obtained for the proposed HA as compared with the experimental results of EYDFA, Raman amplifier and the EDFA/Raman hybrid amplifier.     

高功率双包层Er3+/Yb3+共掺光纤放大器的动态响应

基于速率方程的离散算法,分析了双包层Er3 /Yb3 共掺光纤放大器的动态响应,显示了输出功率和增益的动态特征。当单个脉冲注入放大器时,输出脉冲的峰值功率不仅依赖于输入脉冲的峰值功率,而且依赖于泵浦功率;当脉冲序列注入时,输出脉冲的功率和增益最终将收敛于它们的稳态值。在双信道情况下,输入脉冲重叠时的输出功率和增益变得更陡峭。在连续波泵浦下,反向自发辐射输出功率(ASE-)首先快速地增加到峰值功率,然后单调下降到稳态值;在脉冲波泵浦下,反向自发辐射输出功率(ASE )与光纤长度成反比,而ASE-与光纤长度成正比。     

宽带碲基掺铒光纤放大器增益谱特性研究

建立了一个多信号共存情形下宽带碲基掺铒光纤放大器(EDTFA)四能级模型,系统研究了EDTFA 增益谱随着光纤激活长度、输入信号功率、泵浦功率和纤芯掺杂浓度的演变关系。研究表明,在输入信号功率减小、泵浦功率提高时,C 波段信号增益迅速增大;在光纤长度增长、掺杂浓度提高时,增益谱向 L 波段偏移;在小信号状态下,其 20dB 增益带宽大于 80nm。研究揭示了EDTFA 适合于作为 WDM 系统中的 L 波段和 C L 波段光纤放大器。     

新型两段光纤双向泵浦掺铒光纤放大器

运用工程化掺铒光纤放大器模拟理论方法，基于国产１４８０ｎｍＬＤ泵源和国产Ｅｒ＾３＋／Ａｌ＾３＋共掺杂光纤，从理论和实验上分析比较了新型两段级联泵浦与普通单段双泵两种结构ＥＤＦＡ的增益、功率和限幅特性。两段级联ＥＤＦＡ比单段ＥＤＦＡ的增益、３ｄＢ饱和输出功率和动态范围分别提高了５ｄＢ、１ｄＢ和１２ｄＢ，泵浦光转换效率改善了２０％。     

Basic performance of an organic dye-doped polymer optical fiber amplifier

A polymer optical fiber amplifier (POFA) of the graded-index (GI) type, with gain in the visible region, was successfully prepared for the first time, to our knowledge, with the interfacial-gel polymerization technique. An input signal of 0.85Wat 591 nm was amplified to 420W(27-dB gain) by injection of 690W of pump power at 532 nm into a GI POFA with a 0.5-m length. The efficiency of conversion of pump energy to signal amplification was more than 60%.     

Modeling and optimization of add-drop dynamics in gain-clamped fiber amplifiers

A new dynamic model for gain-clamped fiber amplifiers is presented. The model can simulate the transient behavior of a gain-clamped erbium-doped fiber amplifier as a function of its controlling parameters. Results show the detailed dependence of the amplifier gain dynamics on launched pump power and reveal the pump-power penalty incurred in implementing gain control with minimal transients to power disturbances. The effect on the transients of varying the laser cavity feedback coupling is also presented. Model accuracy is verified by the excellent quantitative agreement with dynamic measurements over a range of operating conditions. Results show how an increase in pump power can effectively suppress both the dynamic and the steady-state signal power transients in wavelength-division multiplexing channel add-drop operations.     

Fabrication and characterization of dye mixture doped polymer optical fiber as a broad wavelength optical amplifier

Rhodamine 6G and Rhodamine B dye mixture doped polymer optical fiber amplifier (POFA), which can operate in a broad wavelength region (60 nm), has been successfully fabricated and tested. Tunable operation of the amplifier over a broad wavelength region is achieved by mixing different ratios of the dyes. The dye doped POFA is pumped axially using 532 nm, 10 ns laser pulses from a frequency doubled Q-switched Nd: YAG laser and the signals are taken from an optical parametric oscillator. A maximum gain of 22.3 dB at 617 nm wavelength has been obtained for a 7 cm long dye mixture doped POFA. The effects of pump energy and length of the fiber on the performance of the fiber amplifier are also studied. There exists an optimum length for which the amplifier gain is at a maximum value.     

前后双泵铒镱共掺磷酸盐玻璃波导放大器增益特性

在铒镱共掺磷酸盐玻璃波导放大器系统的速率方程和传输方程中,考虑上转换效应,并引入描述波导中信号光和泵浦光光场相互作用的重叠因子,以此讨论前后双泵结构与单前泵结构中,Er/Yb共掺比、泵浦光和信号光功率、泵浦光模数等因素对信号光增益的影响,并得到信号光增益光谱和放大自发辐射光光谱.模拟结果表明,与单前向泵浦相比,相同功率条件下,前后双向泵浦中,泵浦功率密度低且均匀分布,上转换效应被有效抑制,1532nm处信号光增益增大约2dB/cm,放大自发辐射光总功率提高.前后双向泵浦同样可以减弱多模泵浦光对增益的负面影响.数值模拟结果与实验值基本一致.     

Performance analysis of BER optimization in WDM systems using EDFA

Wavelength division multiplexing (WDM) systems, which are widely used in telecommunication, have the advantages of huge bandwidth support and reliability. A performance analysis is presented of a WDM system using an erbium-doped fiber amplifier (EDFA), with specific emphasis on bit error rate (BER) optimization. EDFA parameters, including doped fiber length and pump power, are optimized and performance evaluating parameters for different modulation schemes are observed. Simulation results provide optimized BER, noise figure, and gain flatness values. The WDM system is modeled from 1546 nm to 1558 nm bandwidth to obtain maximum gain uniformity, low noise figure, and low BER. This wavelength range is selected to investigate the 1550 nm wavelength commonly used in the telecommunication industry. Also, that we are using a WDM grid, so multiple channels can be accommodated in this range.     

L波段掺铒光纤超荧光光源和放大器研究

通过优化铒光纤长度,获得了平坦谱宽达30nm(0.7dB)的L波段超荧光光源,该光源具有7.21dBm的输出功率。在此基础上,研究L波段放大器增益特性,通过对铒光纤长度的进一步优化,用1480nm激光器作前向泵浦源,实验上获得了波长从1565nm~1595nm范围平坦的增益带宽,小信号增益可达22dB。     

157 W all-fiber high-power picosecond laser

An all-fiber high-power picosecond laser is constructed in a master oscillator power amplifier configuration. The self-constructed fiber laser seed is passively mode locked by a semiconductor saturable absorber mirror. Average output power of 157 W is obtained after three stages of amplification at a fundamental repetition rate of 60 MHz. A short length of ytterbium double-clad fiber with a high doping level is used to suppress nonlinear effects. However, a stimulated Raman scattering (SRS) effect occurs owing to the 78 kW high peak power. A self-made all-fiber repetition rate increasing system is used to octuple the repetition rate and decrease the high peak power. Average output power of 156.6 W is obtained without SRS under the same pump power at a 480 MHz repetition rate with 0.6 nm line width.     

Extraction efficiency of saturated-gain high-power dye laser amplifiers: effect of nonlinear signal absorption

The effect of nonlinear signal absorption (NLSA) due to ground-state absorption and excited-state absorption in a transversely pumped high-power dye laser amplifier is theoretically examined with a one-dimensional steady-state model for a dye amplifier pumped by a copper vapor laser. A well-approximated analytical expression for the extraction efficiency is derived, from which the effect of NLSA in reducing the amplifier efficiency can be appreciated immediately and can also be interpreted in terms of certain characteristic lengths. The reduction in efficiency due to NLSA is found to be largely independent of the pump power, provided that the signal power is increased linearly with the pump power to continue to saturate the amplifier gain and suppress amplified spontaneous emission.     

分布式光纤拉曼放大器研制的进展

对分布式光纤拉曼放大器研究的历史、基本原理、优化设计以及现状和进展进行了讨论.对S波段的色散补偿型分布式光纤拉曼放大器以及采用光纤拉曼激光器作为抽运源,在前向抽运和后向抽运条件下,对5kmDCF-50kmG652光纤色散补偿型分布式光纤拉曼放大器增益光谱和噪声谱进行了研究.设计和制作了光纤光栅的增益平坦滤波器,取得了较好的增益平坦效果.FRA-1型分布式光纤拉曼放大器在校园网进行了应用试验,取得了较好的试验效果.     

C+L波段掺铒光纤光源模拟算法

提出了利用打靶法模拟双级双程泵浦结构掺铒光纤宽带光源的算法,该算法通过对打靶法的初值校正部分进行改进,加入了阻尼因子与下降因子,并把这两个因子同时应用到初值校正中,从而克服了传统打靶法在铒纤长度较长时校正矩阵奇异造成的算法不收敛的缺点.结合宽带光源的理论模型,给出了算法的实际过程,模拟得到了在光纤最佳长度处的C L波段输出谱型,并通过实验证实了模拟与实验结果相符合.最后讨论了导致宽带光源输出谱型不是最佳的因素,随着光纤长度增加导致的损耗,以及两端泵浦功率的比值,并给出了在泵浦功率比是最佳和不是最佳两种情况下的实验谱型.     

宽带铋基掺铒光纤放大器增益及噪声特性研究

利用Er3 离子四能级结构速率方程组和光功率传输方程组,数值模拟了铋基掺铒光纤放大器(EDFA)的增益及噪声特性,模拟结果与实验报道结果取得了很好的一致。同时,详尽地分析了增益及噪声特性与光纤长度、泵浦功率和输入信号功率的关系,优化了放大器的性能,从理论上得出一个20dB增益带宽达76nm、噪声系数接近4dB的铋基EDFA。研究表明了铋基掺铒光纤放大器适合用作于现代DWDM系统中C L波段的光纤放大器。     

光纤拉曼放大器中级联的受激布里渊散射

在以25kmG652单模光纤为增益介质的光纤拉曼放大器中,观察到了级联的受激布里渊散射。光纤中的双瑞利折射作用导致了二阶布里渊散射光子的出现,加快了二阶布里渊散射的出现。在拉曼增益的作用下,随着二阶布里渊散射的饱和会出现级联的多阶布里渊散射,形成梳状光谱。该梳状光谱也具有明显的阈值特性。在拉曼泵浦功率是1200mW的时候,出现梳状光谱的阈值在1.5到2.5dBm之间。在传输系统中,级联的受激布里渊散射会导致放大器的增益饱和,严重恶化系统的信噪比,因此必须采用增加信号光的带宽或者对信号光进行调制等措施加以控制。但该现象也有可能被用来制造梳状光源。     

Gain characteristics of LaF3:Er, Yb nanoparticle-doped waveguide amplifier

Fundamental rate equations and power propagation equations were used to simulate the gain factors of LaF3:Er, Yb nanoparticle-doped waveguide amplifiers excited at 980 nm. The gain first increased and then remained nearly constant with pump power increasing. The gain and the threshold pump power increased with increasing concentration of Er3+. The calculated gain of the concentration 0.75 x 10(26) ions/m3 on a 4 cm long waveguide was 3.6 dB. An optimum waveguide length was found for the highest gain and it was getting larger with the increase of the pump power. When the lifetime decreases from the Judd-Ofelt calculated value of 13.34 ms to the measured value of 60 micros, the required pump power of a 0.5 dB gain increased one level. We obtained a longer 4I(13/2) lifetime (100 micros) through decreasing the proportions of Er3+ and Yb3+ in nanoparticles and found that the threshold pump power decreased more at the expenses of saturated gain.     

SOA-based multi-wavelength source

A simple fiber laser configuration based on a semiconductor optical amplifier (SOA) is proposed for obtaining multi-wavelength oscillation at room temperature, in which a Sagnac loop mirror is used as the wavelength selective component. The SOA has a flat gain of approximately 23dB within a bandwidth of 12 nm at a small input signal power. The loop mirror was constructed using a 3dB coupler and polarization maintaining fiber (PMF). The output spectrum of the proposed laser can be adjusted by controlling the bias current of the SOA and is quite stable at room temperature. At a bias current of 150 mA, six lines are obtained with at least ?40 dBm output power and 25dB signal-to-noise ratio (SNR). The channel spacing and number of lines is determined by the length of polarization maintaining fiber (PMF) used in the loop mirror. The channel spacing of the proposed laser is 1.49 nm with a PMF 3 m. The multi-wavelength comb output can also be tuned by adjusting the operating temperature of the SOA. The multi-wavelength laser has the advantage of a simple configuration, stability at room temperature, a broad wavelength band, and no need for optical pump lasers.     

Design,development and performance characteristics of a large aperture disc amplifier for high power Nd: Glass laser chain

A large aperture disc amplifier has been designed, set-up and characterized for its performance on small signal gain, spatial variation of gain, and thermal recovery time. This amplifier, consisting of three elliptical Nd: phosphate glass discs of size 214 × 114 × 20 mm mounted at Brewster angle and pumped by ten xenon filled flash lamps of 600 mm arc length, provided a small signal gain of 6 at electrical pump energy of 36 kJ (in a pulse of 450 μs) using an in-house developed dual-polarity capacitor bank based power supply. It was coupled to a high power Nd: phosphate glass laser chain and a maximum output pulse energy exceeding 100 J in a 1·5 ns (FWHM) pulse has been measured. A dry nitrogen gas based cooling system was developed for cooling the glass discs with a thermal recovery time of ∼ 20 minutes.