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.     

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.     

Noise figure monitoring of optical amplifiers via backwardamplified spontaneous emission

A new configuration of an optical amplifier is proposed that provide in-service noise figure (NF) monitoring. It is difficult to determine the NF of traditional optical amplifiers in operation because the amplified spontaneous emission (ASE) power cannot be measured separately from the output signal power. The proposed technique measures the NF from the backward ASE power. The discrepancy between the NF measured from forward ASE (using the traditional technique) and backward ASE (proposed technique) is found to be less than 1.0 dB at input powers below -6.2 dBm. A prototype optical amplifier is successfully used as a linear repeater, in a 10 Gbit/s 200 km transmission experiment     

波分复用系统的光信噪比与代价测试方法探讨

本文通过分析光放大器噪声的成分,指出了波分系统中在OSNR表象一致的情况下光放大噪声与ASE噪声的差异,以及这种差异在检测系统传输性能时所造成的影响,并设计了相关的代价测试实验系统。通过对实验数据的分析,指出了进行与系统OSNR代价相关的性能测试时如何获得真实系统参数的办法。     

Gain enhancement in gain-shifted erbium-doped fiber amplifiers forWDM applications

Utilization of amplified spontaneous emission (ASE) for gain enhancement in gain-shifted erbium-doped fiber amplifier (GS-EDFA) is analyzed. It is shown that in a multiwavelength regime, gain enhancement as high as 5 dB can be achieved when the counterpropagating ASE is used to invert an unpumped first stage of a two-stage GS-EDFA. We present design criteria for flat gain operation and noise penalty minimization of two-stage GS-EDFAs determined for multiwavelength operation in the 1580-nm wavelength band. The analysis is based on an application of a comprehensive large-signal numerical model which takes into consideration propagation of signal, pump and both the downstream and upstream ASE powers     

Optimum pumping configuration for L-band EDFA incorporating ASE pump source

L-band gain improvement through usage of secondary pumping sources in the form of amplified spontaneous emission (ASE) was conducted. A simulation of the three-level rate equation that precedes the experimental approach provides a limited overview of the behavior of various inputs into the active medium-the erbium-doped fiber. Gain improvement as high as 6 dB was attained while incurring minimal noise figure penalty; in this case as low as 1 dB. For an L-band amplifier system employing ASE to improve gain, pumping the system counterdirectionally with ASE while the 980- or 1480-nm pumps are being used in a copropagating configuration would yield the best overall performance in terms of gain.     

ASE spectral slice gain-clamping of EDFA

An erbium-doped (Er-doped) fiber amplifier operating in the C-band is gain clamped, at about 26 dB with noise figures below 6 dB by multiple fiber Bragg gratings. These gratings are placed at the amplifier output with center wavelengths in between communication channels so that unwanted amplified spontaneous emission is removed but put to good use. A 0.5-dB gain compression point at -15 dBm of input signal powers for two simultaneous signal channels is also demonstrated.     

3．1～10．6GHz超宽带低噪声放大器的设计

基于SIMC0．18μmRFCMOS工艺技术,设计了可用于3．1—10．6GHzMB—OFDM超宽带接收机射频前端的CMOS低噪声放大器（LNA）。该LNA采用三级结构：第一级是共栅放大器,主要用来进行输入端的匹配;第二级是共源共栅放大器,用来在低频段提供较高的增益;第三级依然为共源共栅结构,用来在高频段提供较高的增益,从而补偿整个频带的增益使得增益平坦度更好。仿真结果表明：在电源电压为1．8v的条件下,所设计的LNA在3．1～10．6GHz的频带范围内增益（521）为20dB左右,具有很好的增益平坦性f±0．4dB）,回波损耗S11、S22均小于-10dB,噪声系数为4．5dB左右,IIP3为-5dBm,PIdB为0dBm。     

Ultra-wideband CMOS low noise amplifier

A two-stage ultra-wideband CMOS low noise amplifier (LNA) is proposed. The first stage is optimised for wideband input matching and low noise figure, while the second stage is optimised to extend the -3 dB bandwidth of the overall amplifier. The combination of stages can provide lower noise figure and wider bandwidth simultaneously over that of previously reported feedback-based CMOS amplifiers. The implemented LNA shows a peak gain of 13.5 dB, more than 8.5 dB of input return loss, and a noise figure of 2.5-7.4 dB over a -3 dB bandwidth from 2 to 9 GHz with DC power consumption of 25.2 mW.     

Reducing ASE Effect in Coherent Detection by Employing Double-Pass Fiber Preamplifier and Time-Domain Filter

We report on a novel fiber based coherent detection system employing a double-pass fiber preamplifier, a spectral bandpass filter, and a time-domain filter. The time-domain filter, a synchronous time gate, reduces the in-band amplified spontaneous emission (ASE) beat noise, which cannot be achieved by the spectral bandpass filter alone. The double-pass fiber amplifier further reduces the out-band ASE by about 20 dB with a fiber Bragg grating (FBG) at the end of the fiber amplifier. In preliminary experiments with a 100 GHz bandpass filter, no degradation is observed from the optically preamplified coherent detection compared to pure coherent detection. With a 10 ns pulse width, 500 kHz repetition rate, and 10 pW average input power, about 2 dB and 1 dB signal-to-noise ratio (SNR) improvements are achieved when 5% and 50% time gating duty cycles are used, respectively.     

Amplified spontaneous emission in pulse-pumped Raman amplifiers

We discuss amplified spontaneous emission (ASE) generated in Raman amplifiers that are counter-pumped with trains of pulses. Our experimental and theoretical results show that if the peak power of the pump pulses is too high, the ASE output from the amplifier can be significantly higher than that from a continuous-wave pumped amplifier providing the same gain. This effect places a lower limit on the duty cycle of pump pulses one can use for a given level of Raman gain. Furthermore, we report an additional ASE enhancement if there is insufficient walkoff between the pump pulses and copropagating ASE to average the effects of higher frequency pump intensity noise. As a result, less pump intensity noise can be tolerated when pulse-pumping a fiber having a zero-dispersion wavelength located midway between the pump and signal wavelengths.     

Diode-laser pumped erbium-doped fluorozirconate fibre amplifier for the 1530 nm communications window

An erbium-doped fluorozirconate fibre amplifier has been pumped at 1480 nm using a semiconductor diode laser. The small signal gain was 15 dB for 25 mW launched pump power. The ASE bandwidth was 45 nm and the predicted noise figure was 5 dB.<>     

一种采用噪声抵消及多重功耗优化技术的UWB-LNA

采用噪声抵消及多重功耗优化技术,提出了一种超宽带低噪声低功耗放大器。它主要包括采用RL网络的共栅输入级、电流复用型噪声抵消级、放大输出级以及偏置电路四个部分。验证结果表明,该放大器,在2-6GHz频带内,增益(S21)可以在14dB以上;输入回波损耗(S11)小于-10dB;输出回波损耗(S22)小于-25dB;噪声系数(NF)小于3.2dB;在3.8V的工作电压下,功耗仅为14mW。     

基于改进的垂直型同轴微带转换的Ku频段平衡低噪声放大器

提出了一种垂直型同轴微带转换的宽带补偿方法,并应用于一款Ku频段平衡低噪声放大器(LNA)的研制。放大器包含波导同轴转换、同轴微带转换、由2级pHEMT 管芯及分支线耦合桥组成的前级放大器以及由MMIC 放大器实现的后级放大器。在13.5 ~14.5 GHz 频率范围内,2 批次累计55 套低噪声放大器的噪声系数小于1.5 dB、增益分布在44.5 ~46.5 dB之间,增益平坦度小于0.6 dB,批次间性能一致性良好。     

60 GHz compact low noise amplifier in 65 nm CMOS

A single-ended low noise amplifier in 65 nm CMOS for applications at 60 GHz is presented. Its measured gain and noise figure at the centre frequency of 57 GHz are 19.1 dB and 5.5 dB, respectively, and it provides wideband matching. Transistors in the design have an asymmetrically fingered layout which reduces parasitic capacitances while simultaneously allowing for higher channel current densities.     

基于GaN HEMT的13～17 GHz收发多功能芯片

基于GaN高电子迁移率晶体管(HEMT)工艺设计制作了一款收发(T/R)多功能芯片(MFC),主要用于射频前端收发系统.该芯片集成了单刀双掷(SPDT)开关用于选择接收通道或发射通道工作,芯片具有低噪声性能、高饱和输出功率和高功率附加效率等特点.芯片接收通道的LNA采用四级放大、单电源供电、电流复用结构,发射通道的功率放大器采用三级放大、末级四胞功率合成结构,选通SPDT开关采用两个并联器件完成.采用微波在片测试系统完成该芯片测试,测试结果表明,在13～ 17 GHz频段内,发射通道功率增益大于17.5 dB,输出功率大于12W,功率附加效率大于27％.接收通道小信号增益大于24 dB,噪声系数小于2.7 dB,1 dB压缩点输出功率大于9 dBm,输入/输出电压驻波比小于1.8∶1,芯片尺寸为3.70 mm×3.55 mm.     

Double-pass L-band EDFA with enhanced noise figure characteristics

A new double-pass long wavelength band erbium-doped fiber amplifier with enhanced noise figure characteristics is demonstrated by adding a short length of forward pumped erbium-doped fiber (EDF) in front of a double-pass amplifier. Compared with the conventional double-pass amplifier, the new amplifier provides noise figure improvement of about 0.8 to 6.0 dB over the flat-gain region from 1568 to 1600 nm. Since the optical circulator prevents the amplified signal and backward amplified spontaneous emission from propagating into the EDF, the population inversion of the input part of the amplifier is hardly affected by the intense lights, therefore, the noise figure could be kept low. The new double-pass system has achieved a flat-gain output at about 33.5 dB, which is 13.5 dB higher than that of the single-pass system with gain variation less than 1.3 dB at the flat-gain region. The noise figure varies from 5.9 to 6.6 dB in this region.     

An 8-channel digitally tunable transmitter with electroabsorptionmodulated output by selective-area epitaxy

We demonstrate an 8-frequency digitally tunable laser based on a waveguide grating router with an electroabsorption modulated output. The laser wavelengths range from 1.567 to 1.580 μm with channel spacings of 200 GHz (1.6 nm). The modulator extinction is -10 dB/VN with a -5-V bias. A unique output coupler design delivers an ASE noise suppression of -55 dB/Å     

Gain clamping in L-band erbium-doped fiber amplifier using a fiberBragg grating

A gain-clamping technique for the long wavelength band (L-band) erbium-doped fiber amplifier (EDFA) is presented. It uses a single fiber Bragg grating (FBG) on the input side of erbium-doped fiber (EDF) to inject a portion of backward conventional band (C-band) amplified spontaneous emission (ASE) back into the system. The use of a narrow-band (NB) FBG has shown a better performance in clamped-gain level and noise figure compared to a broad-band FBG. The amplifier gain for the NB FBG set up is clamped at 15.4 dB with a variation of less than 0.3 dB for an input power as high as 0 dBm     

S波段雷达接收机前端低噪声放大器

采用0.35μm SiGe BiCMOS工艺设计了用于S波段雷达接收机前端电路的低噪声放大器。对于现代无线接收机来说,其动态范围和灵敏度很大程度上都取决于低噪声放大器的噪声性能和线性度。相对于CMOS工艺来说,SiGe BiCMOS工艺具有更高的截止频率、更好的噪声性能和更高的电流增益,非常适合微波集成电路的设计。该低噪声放大器采用三级放大器级联的结构以满足高达30dB的增益要求。在5V的电源电压下,满足绝对稳定条件,在3GHz-3.5GHz频段内,功率增益为34.5dB,噪声系数为1.5dB,输出1dB功率压缩点为11dBm。