An erbium-doped tellurite fiber amplifier for WDM systems with dispersion-shifted fibers

This letter investigates the feasibility of an erbium-doped tellurite fiber amplifier (EDTFA) with a 1581- to 1616-nm amplification band for a wavelength-division-multiplexing transmission system in the L-band that employs dispersion-shifted fiber (DSF). A 10-Gbit/s, 40-channel-transmission from 1581 to 1616 nm in the L-band, where EDTFA's are employed as a post-amplifier, repeaters, and a pre-amplifier, is error-free through a 320-km DSF. The EDTFA can increase both the transmission capacity and the allowable maximum input power launched into a DSF.     

掺铒光纤放大器中孤子脉冲获得线性啁啾的研究

为了研究孤子脉冲经掺铒光纤放大器演变后的啁啾特性,采用了对称分步傅立叶的数值方法,对孤子脉冲在不同增益条件下的演变和线性啁啾特性进行了数值仿真。数值计算的结果表明：当满足增益系数μ远大于1时,基孤子脉冲在放大器中传输能够获得很好的线性啁啾,且发现脉冲的啁啾特性受选取的放大器长度参量的影响;啁啾越明显的脉冲,线性啁啾所占的区域越窄。进一步研究还发现初始啁啾系数和孤子阶数对脉冲获得的线性啁啾均有很大影响,初始正啁啾系数和高孤子阶数均能增强输出脉冲的线性啁啾特性。因此,利用孤子脉冲在掺铒光纤放大器中传输的非线性效应能够获得良好的线性啁啾,这对实现高质量的脉冲压缩是很有帮助的。     

Multi-stage erbium-doped fiber amplifier designs

Applications for erbium-doped fiber optical amplifiers have been multiplying in recent years, and increasingly complex structures have been introduced. We review characteristics and design parameters, the use of interstage elements, and various digital transmissions systems applications for multi-stage amplifiers. A notation is introduced to describe multi-stage fiber amplifiers     

Reflection insensitive erbium-doped fiber amplifier

It is experimentally and theoretically examined how the insertion of an isolator within the erbium-doped fiber influences the sensitivity of the fiber amplifier to external reflections. We examined the EDFA in various regions of saturation, and compared the configuration with the isolator to the traditional configuration without an isolator. The most significant improvements were found in the small-signal region, where the requirements to reflections may be relaxed by as much as 13 dB. This, together with an improved gain and noise figure, makes the configuration with the isolator very attractive for preamplifier applications     

An erbium-doped multimode optical fiber amplifier

The authors describe the first experimental study of an erbium-doped multimode fiber amplifier. The focus has been to characterize an intermediate core erbium-doped optical fiber, a fiber that is capable of propagating many guided modes at both the signal and pump wavelengths, and to determine the feasibility of using such an active fiber as a multimode fiber amplifier, by measuring its gain, noise, and pump power requirements. For a 2-m length of a 13-μm-core erbium-doped fiber, the authors measured gain as high as 16 dB at a signal wavelength of 1543 nm, with approximately 100 mW pump power (980 nm). For these same test conditions, the smallest excess noise factor β was 42     

宽带掺铒光纤放大器的研究

由于光通信系统对带宽的需求不断提高,掺铒光纤放大器（EDFA）C波段已经不能满足WDM系统对带宽的需求,为此有必要开发EDFA中L波段的带宽资源。文章分析总结了国外报道的各种提高L波段增益使其达到可实用阶段的方法,为未来WDM系统提供一种宽带EDFA。     

Broad-band erbium-doped fiber amplifier with double-passconfiguration

We demonstrate a broad-band silica-based erbium-doped fiber amplifier (EDFA) with double-pass configuration. The signal gain and noise figure are obtained more than 24 dB and less than 6 dB, respectively, for 1526-1562 nm and 1569-1605 nm. The same signal gain can be achieved with 53% less pump power and 45% shorter erbium-doped fiber length, compared to a conventional parallel type EDFA. Furthermore, the noise figure and power conversion efficiency are improved for the wavelength range     

EDFA对基孤子脉冲进行压缩与放大的数值研究

从描述光脉冲在掺铒光纤放大器(EDFA)中传输的非线性薛定谔方程出发,对基孤子脉冲在EDFA中的压缩与放大进行了数值研究,并对孤子脉冲在其中的压缩提出优化方案。结果表明,通过合理地选择EDFA的参数,可使无啁啾的基孤子脉冲实现绝热压缩和放大;对具有初始啁啾的基孤子脉冲,压缩过程将不再满足绝热条件;对于正啁啾的基孤子脉冲,可得到较好的压缩与放大;而对于负啁啾的基孤子脉冲,压缩效果却较差。     

Very flat gain erbium-doped fiber amplifier using samarium-doped fiber

A two-stage erbium-doped fiber amplifier (EDFA) with extremely flat gain (/spl plusmn/0.1 dB) over 17-nm bandwidth is demonstrated. The gain flatness is achieved by incorporating samarium-doped fiber in the mid section of the amplifier.     

Passive gain-equalized wide-band erbium-doped fiber amplifier using samarium-doped fiber

A passive gain-equalization technique of erbium-doped fiber amplifier (EDFA) using a samarium-doped fiber to obtain wide-band flattened gain operation is reported. In the wavelength range from 1529-1559-nm, small inter-channel gain variations can be achieved. This simple technique is suitable for multiwavelength wide-band in-line-amplifier cascaded transmission applications.     

Transmission line with distributed erbium-doped fiber amplifier

We show the advantages of distributed erbium-doped fiber amplifiers (EDFAs) over lumped EDFAs. Using the distributed EDFA for 50%-100% of the transmission line lessens the signal degradation compared to the conventional transmission line. We also show the feasibility of the gain-flattened d-EDFA transmission line. An experiment shows that the gain peak is shifted and flattened at low pump powers     

All silica S-band double-pass erbium-doped fiber amplifier

Double-pass (DP) and single-pass (SP) erbium-doped depressed cladding fiber amplifiers designed for S-band operation are evaluated under changes of the input optical power, pumping power, and fiber bending radius. The DP configuration employs the usual combination of a circulator and a Faraday rotator mirror while the SP is based on the copropagating scheme. The amplifiers were characterized in terms of gain and noise figure. It is demonstrated that the DP topology shows much improved gain performance compared to the SP configuration although the noise figure is slightly degraded by counterpropagating amplified spontaneous emission.     

Twin-core erbium-doped fiber amplifier with channel equalization

A twin-core erbium-doped fiber amplifier has been studied. We establish the theoretical model, propose the coupled-propagation equations, and then numerically simulate the characteristics of the amplifier. It is found that twin-core erbium-doped fiber amplifier can provide different gains for signals with different input powers and self-heal the extra channel loss between amplifying stages, thus equalizes the output signal level. The twin-core erbium-doped fiber amplifier is very suitable for the future wavelength-division-multiplexed and optical frequency-division-multiplexed fiber networks.     

Femtosecond soliton transmission characteristics in an ultralongerbium-doped fiber amplifier with different pumping configurations

The transmission characteristics of femtosecond optical solitons in an 18.2 km-long erbium-doped fiber amplifier (EDFA) have been investigated in detail by changing the pumping configuration. With backward pumping, a lossless transmission of 440 fs solitons at 1.55 μm has been realized with a pump power of 16 mW. The output pulsewidth is determined by the spectrum modified by the soliton self-frequency shift. In a bidirectional pumping configuration, 440-fs soliton pulses have been transmitted for a total pump power of 38 mW, where the output pulse width is determined by the original 1.55 μm spectrum. Although a femtosecond soliton is very weakly trapped in the EDFA-gain bandwidth of 1.55 μm and the soliton self-frequency shift inevitably occurs, the femtosecond pulse component still exists at 1.55 μm, and a pulse can be successfully transmitted with a gain of 11 dB and very little pulse broadening     

光孤子传输系统

阐述了光孤子传输系统主要特征及其关键技术,探讨了光孤子传输系统的构成及其实用方案,与传统的线性通信系统相比,被称为非线性通信系统的光孤子传统系统将逐步显示出优越的发展前景。     

碲酸盐掺铒玻璃光纤放大器的瞬态响应

建立了一个数值模拟碲酸盐掺铒玻璃光纤放大器(EDTFA)瞬态响应的理论模型,理论上研究分析了低频方波脉冲输入信号经过EDTFA后的瞬态输出响应.研究结果显示,对于输入信号功率的跃变, EDTFA存在着一个快速的瞬态响应过程,响应时间小于报道的硅基掺铒光纤放大器(EDFA),说明EDTFA适合于泵浦调制及全光纤开关方面的应用场合.通过对双通道信号传输情形下关闭一个信道后另一信道输出功率瞬态响应的研究,揭示了适时调节泵浦功率快速稳定剩余信道输出功率的可行性.     

Long-wavelength erbium-doped fiber amplifier gain enhanced by ASEend-reflectors

We use for what we believe is the first time narrow-band end-reflectors to reduce losses through short-wavelength amplified stimulated emission (ASE) in silica-based erbium-doped fiber amplifiers operating at wavelengths above 1570 mm. The end-reflectors feed a small fraction of the ASE, up to a few tenths of a milliwatt, back into the amplifying fiber. The reflected ASE compresses the short-wavelength gain and thus reduces the ASE-losses, from, e,g., 50 mW for a launched pump power of 110 mW at 980 nm without end-reflector to 10 mW with an optimized end-reflector. We investigate possible improvements of gain (around 5 dB) and output power (up to 17 mW), and the influence of the amount and wavelength of the feedback     

一种新型低噪声掺Er光纤放大器的研究

提出了一种新型的低噪声掺Er光纤放大器(EDFA)。将光波长交错器的输入端口与普通EDFA的输出端相连接,用于降低噪声,信号光由光波长交错器的偶信道端口输出。利用光波长交错器的梳状反射特性,抑制EDFA的放大自发辐射(ASE),改善EDFA的噪声特性,使其具有低噪声的特点。采用4m长的掺Er光纤(EDF)作为增益介质,小信号功率为-26dBm时,在1530～1560nm带宽范围内,测得低噪声EDFA的噪声系数低于3.83dB,仅比噪声系数的量子极限3dB大0.83dB。     

Optimum pumping scheme of dual-stage triple-pass erbium-doped fiber amplifier

The optimization of pump power for a new configuration of dual-stage triple-pass Erbium-doped fiber amplifier is successfully demonstrated. This configuration incorporates two-stage amplifiers with two independent 980-nm pump lasers. The first-stage amplifier consists of double-pass amplification to obtain high gains and the second-stage amplifier is single-pass amplification in backward pumping schemes. The maximum gain that obtained in the experiment does not have the minimum noise figure. Therefore, the optimum operating point is defined based on the ratio of gain to noise figure. The relationship between the pump-power distributions in the proposed configuration shows that the optimum pump ratio of the first-stage pump laser to the total pump power is around 0.3 to 0.5 depending on the signal powers.     

Fluoride-based erbium-doped fiber amplifier with inherently flat gain spectrum

We successfully developed a fluoride-based Er/sup 3+/-doped fiber amplifier (F-EDFA). An average signal gain of 26 dB was achieved for 8 channel wavelength division multiplexed (WDM) signals in the 1532-1560 nm wavelength region with a gain excursion of less than 1.5 dB at an input signal power of -20 dBm per channel. Furthermore, we studied the amplification characteristics of the F-EDFA for WDM signals. The following experimental results were obtained. (1) For an 8-channel WDM signal in the 1532 to 1560 nm wavelength region, the gain excursion between channels can be suppressed to within 1.5 dB. However, the wavelength region allowing a gain excursion of 1.5 dB, is between 1536-1560 nm for the silica-based Er/sup 3+/-doped fiber amplifier. (2) F-EDFAs have a flat gain region between 1534-1542 nm. The gain excursion of this region is less than 0.2 dB for WDM signals.