Gain and noise penalty for detuned 980 nm pumping or erbium-dopedfiber power amplifiers

The impact of altering the fiber length and pump wavelength on the gain and noise performance of erbium-doped fiber power amplifiers pumped in the 980-nm band is examined. A gain penalty of <0.5 dB was experimentally observed over an 18 nm pump wavelength range. Theoretical analysis indicates that increasing the numerical aperture (NA) from 0.15 to 0.25 significantly improves the tolerance for a given gain penalty but has little effect on the noise figure. For a given fiber length, the noise figure increases by 0.1 dB for each 3 nm the pump wavelength deviates from 979 nm     

不同抽运方式下掺Yb3+光纤放大器的增益和噪声特性

为了探讨不同抽运方式下掺Yb3+光纤放大器的增益和噪声特性,对910nm掺Yb3+光纤放大器进行数值模拟。结果表明,抽运方式对增益影响较小,但对噪声特性影响较大,光纤达最佳长度时,正向和双向抽运方式的掺Yb3+光纤放大器要优于反向抽运方式。这一结果对掺Yb3+光纤放大器的试验设计具有重要的作用。     

Dependence of performance of saturated in-line erbium-doped fiberamplifiers on pump wavelength around 1480 nm

The effect of pump wavelength around 1480 nm on the performance of saturated erbium-doped fiber amplifiers (EDFAs) suitable for use as in-line amplifiers for terrestrial and submarine systems is investigated experimentally. The results show that for high-gain amplifiers (25 dB) with high output powers (15 dBm), operating around 10 dB in compression, the performance is relatively insensitive to pump wavelength. However, for lower gain amplifiers (12 dB), pumped at low (15 mW) powers, the compression of the amplifier is found to decrease significantly with increasing pump wavelength, while the noise figure shows a weak minimum for a pump wavelength near 1480 nm     

Spectral dependence of gain and noise in erbium-doped fiberamplifiers

A two-level model of the erbium-doped fiber amplifier is used to analyze the dependence of the amplifier gain saturation, saturated output power, and excess noise factor on pump and signal wavelengths. Measured data are presented confirming that the dependence of the gain, output saturation power, and noise of erbium-doped fiber amplifiers on the signal and pump wavelength can be described by simple equations derived from the model     

Tm-doped fiber amplifiers for 1470-nm-band WDM signals

We describe the gain characteristics of thulium-doped fiber amplifiers (TDFA) for wavelength division multiplexing (WDM) signals. We optimized the TDF length and the ratio between the forward and backward pump power to realize efficient amplification. The TDFA achieved a gain of over 20 dB and a noise figure of less than 6 dB in the 1353-1483 nm wavelength region at a total pump power of 300 mW for WDM signals input at a total power of -7 dBm.     

Comparison of temperature dependence in C-band and L-band EDFAs

Temperature-dependent gain and noise characteristics of conventional band and long wavelength band erbium-doped fiber amplifiers are compared. Gain variations and noise figure penalties are shown for 980- and 1480-nm pump wavelength bands at different average inversion levels when the erbium coil temperature is cycled from -10°C to 80°C. Experimental results demonstrate that the L-band exhibits greater temperature-dependent gain and noise figure excursions compared to the C-band. Furthermore, it is shown that the impact of erbium coil temperature in the L-band is comparatively less dependent upon pump wavelength     

Numerical Modeling of S-Band EDFA Based on Distributed Fiber Loss

A numerical model for the analysis and design of S-band erbium-doped fiber amplifiers has been developed. The model is able to accurately predict the amplifier performances by taking into account the amplified spontaneous emission suppression due to the bending, as well as leakage losses of the fiber used as active medium. The model has been validated by comparing numerical and experimental data of bending loss, amplifier gain, and noise figure of an S-band optical amplifier based on a depressed-cladding erbium-doped fiber. A good agreement has been verified by varying fiber bending radius, input signal power, and wavelength. The model has been then applied to the optimization of the amplifier performances for wavelength-division multiplexer applications. The numerical results show that 20–25 dB gain can be achieved over a 25–30 nm range centered in a different part of the S-band from 1460 to 1525 nm, just by changing the bending radius and the length of a depressed-cladding fiber.      

分布拉曼光纤放大的实验研究

采用符合ITU-T标准的G波段40信道波分复用(WDM)光源对分布式拉曼放大器(DRA)的特性进行了实验研究。对不同抽运方式及不同光纤长度的分布式拉曼放大器性能作了较为详细的报道。在抽运功率相同的条件下，选用50km单模光纤对比研究了不同抽运方式的拉曼放大器增益和噪声。通过对不同光纤长度的分布式拉曼放大器的实验研究发现，在较低抽运功率且输入信号功率较低的情况下，随着光纤长度增加，拉曼增益也增加，有效噪声系数减小。研究了分布式拉曼放大器对波分复用通信系统信噪比的改善，实验发现不同抽运功率下，拉曼放大器对系统信噪比的改善随抽运功率增加而增加，但是不成线性关系，而且最终会出现饱和。     

980 nm和1480 nm LD混合泵浦两段级联掺铒光纤放大器实验研究

采用两段级联掺铒光纤、９８０ｎｍ和１４８０ｎｍＬＤ混合泵浦方式，实验分析比较了内插光隔离器和内插光隔离－耦合环光路结构掺铒光纤放大器（ＥＤＦＡ）的增益、噪声系数和输出功率特性。研制出内插光隔离－耦合环的ＥＤＦＡ，在信号波长１５５３．５ｎｍ处，小信号增益为４２．８ｄＢ，噪声系数为４．４ｄＢ，输出功率为１５．２ｄＢｍ。     

Performance of high-concentration Er3+-doped phosphatefiber amplifiers

The performances of high-concentration Er³⁺-doped phosphate fiber amplifiers are reported. The amplifiers are characterized in terms of gain, noise figure, and signal saturation power in a co-propagating pump configuration. A net gain of 21 dB and a gain per unit length 3 dB/cm are achieved in a 71-mm Er³⁺-doped phosphate fiber     

Performances of Erbium‐Doped Fiber Amplifier Using 1530nm‐Band Pump for Long Wavelength Multichannel Amplification

The performance of a long wavelength‐band erbium‐doped fiber amplifier (L‐band EDFA) using 1530nm‐band pumping has been studied. A 1530nm‐band pump source is built using a tunable light source and two C‐band EDFAs in cascaded configuration, which is able to deliver a maximum output power of 23dBm. Gain coefficient and noise figure (NF) of the L‐band EDFA are measured for pump wavelengths between 1530nm and 1560nm. The gain coefficient with a 1545nm pump is more than twice as large as with a 1480nm pump. It indicates that the L‐band EDFA consumes low power. The noise figure of 1530nm pump is 6.36dB at worst, which is 0.75dB higher than that of 1480nm pumped EDFA. The optimum pump wavelength range to obtain high gain and low NF in the 1530nm band appears to be between 1530nm and 1540nm. Gain spectra as a function of a pump wavelength have bandwidth of more than 10nm so that a broadband pump source can be used as 1530nm‐band pump. The L‐band EDFA is also tested for WDM signals. Flat Gain bandwidth is 32nm from 1571.5 to 1603.5nm within 1dB excursion at input signal of –10dBm/ch. These results demonstrate that 1530nm‐band pump can be used as a new efficient pump source for L‐band EDFAs.     

Hybrid fiber amplifiers consisting of cascaded TDFA and EDFA for WDM signals

The detailed gain characteristics of hybrid fiber amplifiers that consist of cascaded thulium-doped fiber amplifiers (TDFAs) and erbium-doped fiber amplifiers (EDFAs) are reported. The experimental results showed that the hybrid amplifiers have gains of over 20 dB with the bandwidth of more than 80 nm in the wavelength range between 1460 and 1560 nm. The low noise figure (NF) below 7 dB was obtained in 1460-1540 nm when placing a TDFA in the first stage followed by an EDFA and in 1480-1560 nm when placing amplifiers in a reversed order. The gain of TDFA and EDFA was optimized for minimizing the gain variation ratio (GVR=(maximumgain-minimumgain)/minimumgain: in the unit of decibels) of the hybrid amplifiers, and it could be minimized to less than 0.4 for the amplifiers that have gain in the wavelength region from 1460 to 1537 nm. The gain-equalization technique was applied, and the hybrid amplifier that had an average gain of 20 dB, a gain excursion of less than 2 dB, an output power of 14.5 dBm, and an NF of less than 7 dB in the 77-nm gain band was achieved.     

Dynamic properties of double-pass discrete Raman amplifier with FBG-based all-optical gain clamping techniques

The authors propose and implement a discrete fiber Raman amplifier configured in double-pass scheme together with fiber Bragg grating (FBG)-based all-optical feedback. The double-pass amplifiers achieve more than a 30-dB net gain with affordable pump power and guarantee a large margin for gain clamping. The all-optical gain clamping is provided by the lasing wavelength inside the cavity caused by the high reflectivity FBG and wide-band reflector. A stable gain is obtained for large input signal dynamic range of 30 dB. The gain variation is kept below 0.17 dB and the noise figure is flattened at the same time. Also, the authors investigate the Raman gain and noise figure as a function of signal wavelength with the proposed gain clamping technique.     

Investigation on noise characteristics of dual-pumped fiber optical parametric amplifiers based on photonic crystal fibers

The noise characteristics of dual-pumped fiber optical parametric amplifiers(FOPAs) induced by gain and loss in photonic crystal fibers(PCFs) are analyzed.A special photonic crystal fiber is designed.Its noise figure(NF) changes with structure parameters,and it decreases as the hole diameter decreases.Three factors including input-signal power,signal wavelength and pump separation which impact on the final noise figure are discussed with the designed PCF.     

Gain and noise properties of small-signal erbium-doped fiberamplifiers pumped in the 980-nm band

The authors have experimentally and theoretically investigated the effects of detuning the pump wavelength on the gain and noise properties of small-signal, erbium-doped fiber amplifiers codirectionally pumped in the 980-nm band. While the pump wavelength can be varied over a wide range with little impact on the gain, a noise penalty is incurred. For amplifiers saturated by amplified spontaneous emission, it is possible to increase the gain by detuning the pump wavelength     

WDM transmission system performance: influence of non-Gaussiandetected ASE noise and periodic DEMUX characteristic

This paper presents the first unified wavelength division multiplexing (WDM) transmission model for systems incorporating cascaded optical amplifiers and a realistic demultiplexing (DEMUX) characteristic with periodic transfer function. The bit error ratio (BER) is evaluated accounting in rigorous form for the influence of non-Gaussian detected amplified spontaneous emission (ASE) noise, noise correlation between stochastic noise samples in the receiver, the bandwidth of the electrical receiver noise filter, the gain tilt and effective noise figure of optical amplifiers (with as well as without optical ASE noise filtering), channel crosstalk, signal extinction ratio and a one-or two-stage DEMUX implementation. The model is compared to the Gaussian receiver model in realistic design cases providing important information as to the validity of the Gaussian model. Practical design results indicate the link budget dependence on the DEMUX design and the ASE noise filtering     

Characterization of efficient dual-wavelength (1050 + 800 nm) pumping scheme for thulium-doped fiber amplifiers

We report on the characterization of a recently introduced dual-wavelength pumping scheme for thulium-doped fiber amplifiers using 800 and 1050 nm. Using a counterpropagating pump configuration, 180 mW of total pump power yielded 27-dB small-signal gain and less than 5-dB noise figure. Furthermore, using optical frequency domain reflectometry, the distributed gain in this configuration was evaluated, allowing for optimization of the doped fiber length.     

A novel ASE self-pumping technique for gain-enhanced L-band erbium-doped fiber amplifiers

A novel method of enhancing gain in long-wavelength-band erbium-doped fiber amplifiers is described using the unwanted amplified spontaneous emission (ASE) self-pumping technique. The unwanted ASE from a first stage amplifier is recycled into a second stage amplifier as a secondary pump. Gain improvements in the vicinity of 0.4 and 1.2 dB are obtained in the wavelength range of 1570–1600 nm. This enables support for higher channels in multiwavelength systems with negligible noise figure penalties.     

一种宽带放大器用掺铒碲酸盐玻璃光纤的增益特性

研制了一种新型掺铒碲酸盐玻璃TeO2-ZnO-Na2O-Bi2O3,利用Judd-Ofelt和McCumber理论计算了Er3 离子的强度参数、自发辐射几率、吸收截面和发射截面等光谱参数.应用四能级粒子数速率-光功率传输方程模型,研究了以该掺铒碲酸盐玻璃光纤作为增益介质时光纤放大器的增益特性,模型综合考虑了Er3 离子的能量上转移、交叉驰豫、激发态吸收和放大自发辐射噪声.模拟结果显示,研制的碲酸盐玻璃光纤具有高的信号增益和宽的增益谱特性,在200 mW泵浦功率和多波长信号(-30 dBm× 56 channels)同时输入情形下,最大信号增益和20 dB增益带宽分别超过了40 dB和80 nm,增益谱覆盖了C L波段区域,预示这是一种较为理想的可用于宽带放大的增益介质.同时得出,碲酸盐玻璃光纤结构参数的选择对其增益特性具有重要影响.     

掺镱双包层光纤放大器的放大特性

从掺镱(Yb)光纤放大器的功率传输方程出发,利用有限差分法对小模场面积(SMA)和大模场面积(LMA)掺镱双包层光纤放大器的放大特性进行了分析比较.采用模场直径(MFD)6.5μm和20μm的双包层掺镱光纤作为放大器增益介质进行窄线宽连续信号的放大,在915 nm激光抽运下模拟计算了大、小模场面积输出功率随输入信号功率、抽运光功率和光纤长度的变化特性,特别是对于大模场面积光纤放大器,最优光纤长度的选择至关重要;讨论了模场直径不同时的最优抽运功率和光纤长度的选择,得出4 m光纤放大时的临界抽运功率为4 W,理论与实验结果基本一致.为实际应用中根据信号光、抽运光、增益和模式等要求而选择光纤长度和类型等优化设计提供了理论依据.