Laser diode pumped Er3+-doped fiber amplifier in a 565Mbit/s DPSK coherent transmission experiment

A laser-diode-pumped erbium-doped fiber amplifier, exhibiting 9-dB gain, has been operated as an in-line optical repeater in a 565-Mb/s coherent optical communications system. A sensitivity penalty of 0.4 dB was observed when the amplifier was positioned 35 dB away from the receiver, thus indicating a system improvement of 8.6 dB. By progressively reducing the coupling loss between amplifier and receiver, the noise figure of the contradirectionally pumped amplifier was calculated to be 5.4 dB, a value which is consistent with simple noise theory     

High-gain mode-adapted semiconductor optical amplifier with12.4-dBm saturation output power at 1550 nm

A mode-adapted semiconductor optical amplifier (SOA) has been fabricated and packaged. At the gain peak, 1500 nm, the fiber to fiber gain was measured to be 32.5 dB. Statistics for eight packaged devices indicate that a fiber-to-fiber gain of 26.3 dB ± 1.3 dB and a saturation output power of 12.4 dBm ± 0.4 dBm are typical at a bias of 500 mA for λ = 1550 nm. Polarization sensitivity at 1550 nm was measured to be 1.1 dB ± 0.4 dB and the transverse electric (TE) polarization state noise figure (NF) was determined to be 7.0 dB ± 0.5 dB. The coupling loss was 1.3 dB ± 0.1 dB per facet. This SOA, with a 1.3-nm filter, was used as an optical preamplifier in a 10-Gb/s return-to-zero (RZ) system testbed with a pseudorandom binary sequence (PRBS) of 2³¹ -1. A 14.5-dB improvement in receiver sensitivity was observed at a bit error rate (BER) of 10^-11     

2-Gbit/s signal amplification at λ=1.53 μm in anerbium-doped single-mode fiber amplifier

The gain, saturation power, and noise of an erbium-doped single-mode traveling-wave fiber amplifier operating at a wavelength λ=1.53 μm are characterized. In continuous-wave (CW) measurements amplification at 2 Gbit/s was demonstrated with up to 17-dB gain for 1×10^-9 bit error rate at 1.531 μm and a 3-dB full bandwidth of 14 nm. From the determination of the fiber-amplifier's output signal-to-noise ratio versus input signal power during data transmission, it was concluded that, with signal levels used here, signal-spontaneous beat noise limited the receiver sensitivity improvement. With the fiber amplifier acting as an optical preamplifier of the receiver, the best sensitivity was -30 dBm, obtained after installing a polarizer at the fiber amplifier output to reject half of the applied spontaneous emission power. This sensitivity was 6 dB better than without the fiber amplifier, proving that the fiber amplifier can be used as a preamplifier     

Optical amplifier noise figure in a coherent optical transmissionsystem

Two important aspects of optical amplifier noise figure as measured with a heterodyne detection receiver are investigated. First, differential mode gain will result in polarization-dependent degradation of the perceived amplifier noise figure, even when the noise figures for the TE and TM modes of the amplifier are the same. For a differential mode gain of 7.5 dB the noise figure degradation can be as large as 3 dB, and experimental data is reported in good agreement with theoretical predictions. Secondly, the first experimental demonstration of the use of image-rejection techniques to improve the sensitivity of a heterodyne receiver limited by beat noise between the local oscillator and amplified spontaneous emission is discussed     

REAP: recycled erbium amplifier pump

We report a novel erbium doped fiber preamplifier design with a combination of high gain (>40 dB) and low noise figure (3 dB) at 1556 nm for 80 mW of 980 nm pump power. The co-directional single pumped amplifier employs a composite two stage arrangement in which the second stage is pumped with recycled pump not used in the first stage. In addition, we contrast the amplifier performance trade-offs with the insertions of an isolator or a band pass filter or both in between the two amplifier sections. Finally, we demonstrate a receiver sensitivity of -37 dBm (156 photons/bit) with a 10 Gb/s optical preamplifier regenerator     

Design of an L1 band low noise single-chip GPS receiver in 0.18 μm CMOS technology

This article presents an L1 band low noise integrated global positioning system(GPS)receiver chip using 0.18 μm CMOS technology.Dual-conversion with a low-IF architecture was used for this GPS receiver.The receiver is composed of low noise amplifier(LNA),down-conversion mixers,band pass filter,received signal strength indicator,variable gain amplifier,programmable gain amplifier,ADC,PLL frequency synthesizer and other key blocks.The receiver achieves a maximum gain of 105 dB and noise figure less than 6 dB.The variable gain amplifier(VGA)and programmable gain amplifier(PGA)provide gain control dynamic range over 50 dB.The receiver consumes less than 160 mW from a 1.8 V supply while occupying a 2.9 mm2chip area including the ESD I/O pads.     

基于小信号放大的掺铒光纤放大器的仿真与实验北大核心CSCD

本文研究并设计了一种掺铒光纤放大器,该EDFA能够有效对微弱光信号功率进行放大。首先在OptiSystem环境下进行理论数值仿真优化,根据仿真优化结果对现有光路进行改进。为对比两种掺杂浓度光纤的增益特性,本文进行低掺光纤和高掺光纤仿真与实验,发现高掺光纤优势较大,选用高掺光纤增益系数可达34.2 dB。相较传统EDFA,选择的高掺光纤长度仅为传统光纤长度的十分之一,并且可以保证增益系数在34 dB以上;其次在缩短光纤长度的条件下对-40 dBm的信号产生较大增益,利用改进的插值法计算测量得到的噪声系数更加精确,较传统放大器低0.3 dB左右,实现较低噪声系数和较高增益。基于以上优点,该放大器已应用于信号光的前置放大系统,对小信号光具有良好的放大效果。     

30 GHz Band Low Noise Receiver for 30/20 GHz Single-Conversion Transponder

This paper describes the design and performance of a low noise multicarrier receiver for a 30/20 GHz single-conversion satellite transponder. To develop a low noise receiver the following areas were examined: 1) analysis of spurious signals, 2) selection of devices most suitable for use on board the satellite, and 3) level diagram tradeoff studies. The receiver consists of a 30 GHz low noise GaAs FET amplifier, a 30/20 GHz GaAs Schottky barrier diode mixer, a dielectric resonated local oscillator, a 20 GHz high gain GaAs FET amplifier, and a 20 GHz high power (0.5 W) GaAs FET amplifier. The receiver has an 8 dB noise figure and a 48 dB gain in the frequency range from 28.395 GHz to 29.015 GHz (620 MHz frequency bandwidth).     

A low-noise and gain-flattened amplifier composed of a silica-based and a fluoride-based Er/sup 3+/-doped fiber amplifier in a cascade configuration

We propose a novel low noise and gain-flattened Er/sup 3+/-doped fiber amplifier (EDFA) with a cascade configuration for wavelength division multiplexing (WDM) signals. In this configuration, a 1480-nm pumped fluoride-based EDFA is joined to a 980-nm pumped silica-based EDFA through an optical isolator. By adjusting the silica-based Er/sup 3+/-doped fiber length in the silica-based EDFA, we realized an excellent flat gain EDFA with a gain excursion of less than 0.9 dB and noise figure of 5.7/spl plusmn/0.2 dB, and a low noise EDFA with a noise figure of 5/spl plusmn/0.2 dB and a gain excursion of less than 1.4 dB, for 8 channel WDM signal in the 1532-1560-nm wavelength region.     

Influence of reflected light on erbium-doped fiber amplifiers foroptical AM video signal transmission systems

Investigates experimentally the influence of reflected light on an erbium-doped fiber amplifier for use in optical AM frequency-division multiplexing (FDM) video distribution systems when reflection points exist before and after the amplifier. It is found that amplifier distortion is not affected by reflected light but that the signal gain and the noise figure of the fiber amplifier degrade with increased reflectivity. Gain was decreased by 3 dB when reflectivity after the amplifier was -12 dB. It was theoretically and experimentally clarified that the noise figure degradation was related to the internal reflection of the erbium-doped fiber, in addition to the reflection before and after the fiber amplifier. This internal reflection is caused by input signal light scattered within the erbium-doped fiber     

一种新型低噪声并联C+L波段掺铒光纤放大器

提出并论证了一种新的低噪声系数C+L波段掺铒光纤放大器的结构.在该结构中,利用一个前置放大器以减少噪声系数,并利用一个带有光纤布拉格光栅的双通结构以增加L波段增益,同时减少噪声系数.实验结果表明,新宽带放大器的噪声系数减小了约2 dB,并且在1 525～1 605 nm波长范围内,增益提高到了25 dB以上.     

用于IEEE802．11b／g WLAN直接下变频接收机的射频前端设计

介绍了一种应用于IEEE802．11b／g无线局域网接收机射频前端的设计。基于直接下变频的系统架构。接收机集成了低噪声放大器、I／Q下变频器、去直流偏移滤波器、基带放大器和信道选择滤波器。电路采用TSMC0．18μm CMOS工艺设计,工作在2．4GHz ISM（工业、科学和医疗）频段,实现的低噪声放大器噪声系数为0．84dB,增益为16dB,S11低于-15dB,功耗为13mW;I／Q下变频器电压增益为2dB,输入1dB压缩点为-1 dBm,噪声系数为13dB,功耗低于10mw。整个接收机射频前端仿真得到的噪声系数为3．5dB,IIP3为-8dBm,IP2大于30dBm,电压增益为31dB,功耗为32mW。     

Use of LD-pumped erbium-doped fiber preamplifiers with optimalnoise filtering in a FDMA-FSK 1 Gb/s star network

An erbium-doped fiber amplifier was implemented in a closely spaced FDMA-FSK (frequency-division-multiple-access-frequency-shift-keyed) optical star network with a signaling rate of 1 Gb/s per channel. The fiber preamplifier, which is laser-diode pumped, increases the sensitivity of the direct-detection avalanche photodiode (APD) receiver by 14 dB, allowing for an increased number of network users. This enhanced sensitivity nearly corresponds to all of the available gain of the amplifier. Furthermore, the amplifier noise is optimally filtered by means of a wide band interference filter cascaded with a narrow band fiber Fabry-Perot filter     

DCF光纤拉曼放大器的实验研究

DCF(dispersion compensating fibre)光纤具有较高的拉曼增益系数,利用这一点可以用较短长度的DCF光纤制成分立式的光纤拉曼放大器,作为传输线路上的损耗补偿.本文在测量并计算了DCF光纤的拉曼增益系数的基础上,对分立式的DCF放大器的开关增益和噪声指数进行了测量和分析,并将分立式FRA和分布式FRA在开关增益和噪声指数方面做了比较。介绍了用不同的测量方法所造成的实验结果的差异.实验结果表明,放大介质为5 km的DCF光纤所构成的放大器,在抽运功率为800 mW的条件下,最大增益可达14.77dB,3 dB带宽为35 nm,满足作为损耗补偿的要求.     

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.     

110-120-GHz monolithic low-noise amplifiers

The authors discuss the development of 110-120-GHz monolithic low-noise amplifiers (LNAs) using 0.1-mm pseudomorphic AlGaAs/InGaAs/GaAs low-noise HEMT technology. Two 2-stage LNAs have been designed, fabricated, and tested. The first amplifier demonstrates a gain of 12 dB at 112 to 115 GHz with a noise figure of 6.3 dB when biased for high gain, and a noise figure of 5.5 dB is achieved with an associated gain of 10 dB at 113 GHz when biased for low-noise figure. The other amplifier has a measured small-signal gain of 19.6 dB at 110 GHz with a noise figure of 3.9 dB. A noise figure of 3.4 dB with 15.6-dB associated gain was obtained at 113 GHz. The authors state that the small-signal gain and noise figure performance for the second LNA are the best results ever achieved for a two-stage HEMT amplifier at this frequency band     

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     

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.     

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。     

E‐Band Wideband MMIC Receiver Using 0.1 µm GaAs pHEMT Process

In this paper, the implementations of a 0.1 µm gallium arsenide (GaAs) pseudomorphic high electron mobility transistor process for a low noise amplifier (LNA), a subharmonically pumped (SHP) mixer, and a single‐chip receiver for 70/80 GHz point‐to‐point communications are presented. To obtain high‐gain performance and good flatness for a 15 GHz (71 GHz to 86 GHz) wideband LNA, a five‐stage input/output port transmission line matching method is used. To decrease the package loss and cost, 2nd and 4th SHP mixers were designed. From the measured results, the five‐stage LNA shows a gain of 23 dB and a noise figure of 4.5 dB. The 2nd and 4th SHP mixers show conversion losses of 12 dB and 17 dB and input P1dB of –1.5 dBm to 1.5 dBm. Finally, a single‐chip receiver based on the 4th SHP mixer shows a gain of 6 dB, a noise figure of 6 dB, and an input P1dB of –21 dBm.