High-gain coefficient long-wavelength-band erbium-doped fiberamplifier using 1530-nm band pump

A 1530-nm band has been studied as a pump wavelength for the long-wavelength-band erbium-doped fiber amplifier (L-band EDFA). The pump source is built using a tunable light source and cascaded conventional-band (C-band) EDFA. The L-band EDFA uses a forward pumping scheme. Within the 1530-nm band, the 1545-nm pump demonstrates 0.45-dB/mW gain coefficient, which is twice better than that of conventional 1480-nm pumped EDFA. The noise figure of the 1530-nm pump is at worst 6.36 dB, which is 0.75 dB higher than that of the 1480-nm pumped EDFA. Such high-gain coefficient indicates that the L-band EDFA consumes low power     

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.     

Comparative study on temperature-dependent multichannel gain andnoise figure distortion for 1.48- and 0.98-μm pumped EDFAs

Temperature dependence of multichannel gain flatness and noise figure (NF) was compared for different pump wavelengths of 1.48 and 0.98 μm on silica-based erbium-doped fiber amplifiers (EDFAs) through measurement-based numerical simulation. Owing to its temperature sensitive pump emission cross section, the 1.48-μm pumping showed greater temperature sensitivity (maximum 0.75-dB gain flatness distortion with 0.57-dB average gain level shift, 0.3-dB NF variation for 25°C change) than the 0.98 μm pumping (maximum 0.5-dB gain flatness distortion with 0.015-dB average gain level shift, 0.05-dB NF variation for 25°C change). However, it was also found that distortion ripple spectra mainly coming from the changes of signal cross sections and asymmetric gain temperature dependence necessitate compensation techniques in the EDFA link, irrespective of pump wavelength     

New pump wavelength of 1540-nm band for long-wavelength-band erbium-doped fiber amplifier (L-band EDFA)

A long-wavelength-band erbium-doped fiber amplifier (L-band EDFA) using a pump wavelength source of 1540-nm band has been extensively investigated from a small single channel input signal to high-power wavelength division multiplexing (WDM) signals. The small-signal gain coefficient of 1545-nm pumping among the 1540-nm band is 2.25 times higher compared to the conventional 1480-nm pumping. This improvement in gain coefficient is not limited by the pumping direction. The cause for this high coefficient is explained by analyzing forward- and backward-amplified spontaneous emission spectra. The gain spectra as a function of a pump wavelength suggest that a broadband pump source as well as a single wavelength pump can be used as a 1540-nm-band pump. In the experiment for high-power WDM signals, the power conversion efficiency for 256 WDM channel input is 48.5% with 1545-nm pumping. This result shows more than 20% improvement compared with the previous highest value for the L-band EDFA. Finally, the 1545-nm bidirectionally pumped EDFA is applied as a second stage amplifier in an in-line amplifier of an optical communication link with a 1480-nm pumped first stage EDFA, in which the input power of the second-stage EDFA is +2.2 dBm. The power conversion efficiency yields a 38% improvement without noise figure degradation compared with the case of 1480-nm pumping.     

Wideband HEMT MMIC low-noise amplifier with temperaturecompensation

A wideband low-noise pseudomorphic HEMT MMIC variable-gain amplifier has been designed and fabricated. The amplifier has a nominal gain of 13 dB across the band 2-20 GHz, with gain flatness better than ±0.4 dB. The noise figure is less than 3 dB across the band 6-16 GHz. An on-chip temperature-sensing diode is used to provide a linear temperature correction which has been used to reduce the gain variation of the amplifier by a factor of 2 across the temperature range -50°C to +95°C     

Noise Figure Limit of L-band EDFAs

Erbium-doped fiber amplifiers (EDFAs) with high gain generally degrade the signal-to-noise ratio by at least 3 dB. In the conventional wavelength band, noise figures close to the so-called quantum limit can be obtained by strong pumping. Due to their lower average population in the metastable level, this limit is not reached by amplifiers designed for the long-wavelength band (L-band). In this paper, the lower noise figure limit is determined for such amplifiers. It has been found that the noise figure for typical gain values of about 30 dB can be very close to the quantum limit, whereas significantly larger noise figure values result for small amplifier gains. The lower limit decreases with increasing gain if the gain values are beyond 5 dB. In addition, the results reveal that low temperatures yield better noise figure.     

Gain enhancement in L-band loop EDFA through C-band signal injection

Gain enhancement provided in L-band erbium-doped fiber amplifier (EDFA) with loop configuration and through C-band signal injection is experimentally demonstrated and compared with conventional single-stage L-band EDFA design. Significant backward amplified spontaneous emission suppression in C-band and pump conversion efficiency increase in L-band were observed for varying C-band seed signal wavelength and power levels. Gain and noise figure (NF) performance of loop design L-EDFA is compared with the conventional bidirectionally pumped single-stage L-EDFA design. Gain and NF measurements in the loop configuration have resulted in an up to 9.5-dB increase in gain and up to 2.6-dB degradation in NF at a moderate signal wavelength of 1585 nm.     

Gain clamping in two-stage L-band EDFA using a broadband FBG

A gain-clamped long wavelength band erbium-doped fiber amplifier (L-band EDFA) with an improved gain characteristic is demonstrated by simply adding a broadband conventional band (C-band) fiber Bragg grating (FBG) in a two-stage amplifier system. The FBG reflects backward C-band amplified spontaneous emission (ASE) from the second stage back into the system to clamp the gain. The gain is clamped at about 22.4 dB with a gain variation below 0.4 dB for input signal powers of -40 to -15 dBm. Compared with an unclamped amplifier of similar noise figure values, the small signal gain has improved by 2.4 dB due to the FBG which blocks the backward propagating ASE. At wavelengths from 1570 to 1600 nm, gain of the clamped amplifier varies from 19.4 to 26.7 dB. The corresponding noise figure varies by /spl plusmn/0.35 dB around 5 dB, which is not much different compared to that of the unclamped amplifier.     

Performance degradation of erbium doped fibre amplifier induced by terminal reflection

Degradation of the gain and noise characteristics of an erbium doped fibre amplifier induced by terminal reflection is analysed. It is shown that the reflection at the input end seriously affects the noise characteristics; reflections at the input end smaller than -50 dB at signal wavelength of 1535 nm, and smaller than -36 dB at 1553 nm, are required to suppress the noise figure deterioration below 0.5 dB.<>     

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     

Inherent enhancement of gain flatness and achievement of broad gainbandwidth in erbium-doped silica fiber amplifiers

We report new methods to inherently increase the flatness and bandwidth of erbium-doped silica fiber amplifiers from three perspectives: fiber design, pump-signal WDM coupler optimization, and amplifier structure. First, to achieve inherent control of the gain spectrum, a new type of composite fiber structure with an Er-doped core and a Sm-doped cladding ring is proposed and experimentally demonstrated. Interaction of the optical field with the Sm-doped cladding to produce evanescent wave filtering is modeled, which provides an in-line control of gain fluctuation in the erbium-doped flier amplifier (EDFA) C band, 1530-1560 nm. Second, the effect of the spectral characteristics of WDM couplers over the L band of an EDFA is explored. A fused taper fiber coupler for a 1480-nm pump is optimized for signals in the wavelength range of 1570-1610 nm by measuring the small-signal gain, gain tilt, and noise figure in an L-band EDFA. Finally, a new all-fiber structure for a wide-band EDFA, where the L and C bands were coupled serially, is demonstrated with optimized pump-signal couplers. Further optimization of the new composite fiber structure and the transient effects in the serially coupled EDFAs are also discussed     

C+L波段宽带增益平坦铋基掺铒光纤放大器的设计

基于光纤放大器增益谱的宽带平坦化发展需要,设计了一个两段铋基掺铒光纤(Bi-EDF)级联并携带一个C波段(1 530~1 565 nm)宽带光纤布拉格光栅(FBG)的双通结构型铋基掺铒光纤放大器(Bi-EDFA),从理论上研究了其对输入信号的放大特性。研究表明:FBG的引入可以使C和L波段(1 570~1 620 nm)信号分别经历不同长度Bi-EDF的双向传输,各自获得高增益放大,实现增益谱的宽带平坦化。在200 mW的1 480 nm双向对称泵浦下,第一级和第二级Bi-EDF长度分别为50 cm和170 cm时,对于波长间隔为2 nm、每路功率为-30 dBm的56路C+L波段信号的输入,Bi-EDFA高于30 dB的增益带宽达到了90 nm(1 530~1 620 nm),平均增益为35.7 dB,增益起伏仅为2.3 dB。同时,噪声系数得到明显改善。研究结果对于研制具有宽带、增益平坦的C+L波段Bi-EDFA具有实际指导意义。     

The Effects of Complex Energy Transfer Dynamics and Gaussian Profiles on the Performance of High-Concentration EDFAs

In this paper, we investigate the effects of complex energy transfer dynamics and Gaussian profiles on the gain and noise figure performance of erbium-doped fiber amplifiers (EDFAs) with high doping concentration. We use a two-level system to study the complex energy transfer dynamics that comes from the homogeneous up-conversion (HUC) and the pair-induced quenching (PIQ). In our model, the system is stimulated by a pump source at the wavelength of 1480 nm and operated with a signal source at the wavelength of 1560 nm. Assuming a uniform distribution of erbium ions in the fiber core, we approximate the fundamental mode distributions by Gaussian profiles which are commonly used to calculate the mode radius or spot size. Using the numerical calculations and analysis of the rate and power propagation equations for a two-level model under consideration, the most advantageous Gaussian profile is determined as the Whitley mode radius to obtain a high-gain and a low-noise figure per unit length of silica-based fiber amplifiers. The effects of the number of ions per cluster and the percentage of ions in clusters on the calculated gain and noise figure are compared for several pump powers. Results are discussed to achieve a desired gain and noise figure performance, and compared with the available experimental data to verify the feasibility of the model.     

High dynamic range temperature point sensor using greenfluorescence intensity ratio in erbium-doped silica fiber

We propose a sensor based on the temperature dependant behavior of the two lines of green emission of the erbium ion. The ratio of the intensities of these two lines presents a very low dependance on pump wavelength and pump power fluctuations. The sensitivity of the ratio is 0.013/°C between room temperature and 600°C. In addition, the measurement is self-calibrated     

Noise figure of erbium doped fiber amplifiers in the saturatedregime

We have made an experimental and theoretical study of the noise figure of an erbium doped fiber amplifier in the saturated regime. The saturated amplified spontaneous emission at the signal wavelength was measured using a very accurate pulsed source technique. We have quantified the noise figure dependence on compression, in excellent agreement with theory, to be less than 1.5 dB for a gain compression as high as 15 dB when the small signal gain was 26 dB, and the 1.48 μm pump power was 27 mW     

反射式L波段掺铒光纤放大器增益与噪声指数改善

提出了一种改善反射式L波段掺铒光纤放大器增益和噪声指数的方法,即在放大器的输入端插入一泵浦源,通过提高信号输入端的粒子数反转率实现提高增益和降低噪声指数的目的.通过仔细调整两个泵浦源的输出功率,与单泵浦结构相比,在相同条件下,在1565～1615 nm波长范围内,小信号增益提高了1.5～9.9 dB,噪声指数下降了1.3～9.4 dB.     

Low-noise intelligent cladding-pumped L-band EDFA

We present results on a low-cost cladding-pumped L-band amplifier based on side pumping (GTWave) fiber technology and pumped by a single 980-nm multimode diode. We show that simultaneous noise reduction and transient suppression can be achieved by using gain clamping by a seed signal (/spl lambda/=1564 nm). In the gain-clamping regime, the amplifier exhibits 30-dB gain over 1570-1605-nm spectral band with noise figure below 7 dB. The noise figure can be further reduced to below 5 dB by utilizing a low power single-mode pump at 980 nm. The erbium-doped fiber amplifier is relatively insensitive to input signal variations with power excursions below 0.15 dB for a 10-dB channel add-drop.     

Gain enhancement in L-band EDFA through a double-pass technique

An improvement of gain in the long-wavelength band (L-band) is observed by double passing the forward amplified spontaneous emission and signal in the erbium-doped fiber (EDF) using a circulator, unlike conventional single pass amplification. A gain enhancement as high as 11 dB is obtained for a 1570-nm signal with an input power of -20 dBm at 98 mW of pump power. However, a noise figure penalty of about 2 dB is observed     

L波段砷化镓单片低噪声放大器

设计、研制了一种工作在Ｌ波段的ＧａＡｓ单片低噪声放大器。该放大器在ＨＰ－８５１０Ｂ网络分析仪和ＨＰ－８９７０Ｂ自动噪声仪上的测试结果为：１．１～１．５ＧＨＺ频段，ＮＦ≤２．０ｄＢ，Ｇ≥１８ｄＢ，ＶＳＷＲ（ｉｎ，ｏｕｔ）≤２：１，增益起伏≤０．５ｄＢ；在１．５～２．０ＧＨＺ频段ＮＦ≤２．５ｄＢ，Ｇ≥１８ｄＢ，ＶＳＷＲ（ｉｎ，ｏｕｔ）≤２：１，增益起伏≤±０．５ｄＢ。     

1.4-μm-band gain characteristics of a Tm-Ho-doped ZBLYAN fiberamplifier pumped in the 0.8-μm band

The gain characteristics of a 1.4-μm-band thulium-holmium-doped ZBLYAN fiber amplifier are described. Signal gain is obtained over the whole 1.4-μm band for a pump power level of 73.5 mW. A maximum signal gain of 18 dB is achieved at a signal wavelength of 6.46 μm for a pump power of 150 mW at 0.79 μm. The noise figure is 5.6 dB in the signal wavelength region from 1.45-1.50 μm. From a comparison of the gain characteristics of thulium-holmium-doped ZBLYAN fibers and thulium-doped ZBLYAN fibers, it is proved that holmium ions play an effective role in increasing the gain and widening the gain spectrum