Transmission distance of in-line amplifier systems withgroup-velocity-dispersion compensation

Group-velocity dispersion (GVD) compensation in in-line amplifier systems is evaluated from the viewpoint of improving the transmission distance. The nonlinear Schrodinger equation, which simulates signal propagation in optical fibers, is numerically evaluated to clarify the optimum configuration for GVD compensation. It is shown that the optimum amount of GVD compensation is about 100% of the GVD experienced by the transmitted signal. The optimum compensation interval is found to be a function of the bit rate, signal power, and dispersion parameter. For dispersion parameter values ranging from about -0.1 ps/nm/km to -10 ps/nm/km, and an amplifier noise figure of about 6 dB, the optimum compensation configuration can eliminate the GVD from in-line amplifier systems, thus improving transmission distances to those limited by self-phase modulation and higher-order GVD     

Low-noise and high-power Pr3+-doped fluoride fiberamplifier

We have successfully developed a low-noise and high-power Pr³⁺-doped fluoride amplifier (PDFA) module with a cascade configuration. The maximum signal gain and noise figure were 40.6 dB and 5 dB, respectively. An output power of 20.1 dBm was achieved at an input signal power of 0 dBm. We confirm that this PDFA module performs well from experimental results on its use in a 40 channel AM-VSB video signal transmission and a 10 Gbit/s digital transmission     

Low-noise Pr3+-doped fluoride fibre amplifier

The authors have constructed a Pr³⁺-doped fluoride amplifier (PDFA) module pumped by an Nd-YLF laser. The maximum signal gain and noise figure were 20 dB and 5 dB respectively. An output power of 19.2 dBm was achieved at an input signal power of 11.0 dBm. It was confirmed that this PDFA module has low-noise characteristics from experimental results on its use in a subcarrier multiplexed multichannel AM-VSB video signal transmission     

Linear microwave amplification with Gunn oscillators

Linear microwave amplifiers with continuous power outputs of 100 mW have been constructed utilizing the frequency-independent negative conductance observed externally in Gunn oscillators. This negative conductance is exhibited only in samples containing propagating dipole layers, in other words,n_{0} . Lmust be larger than 10¹²cm^-2for n-GaAs. The output power obtainable from this amplifier is substantially larger than that from a subcritically doped GaAs amplifier (n_{0} . L < 10^{12}cm^-2) becausen_{0} . Lcan be increased. Power output and efficiency are discussed in terms of n0andL. The upper-frequency limit for amplification is determined by the time the domain takes to readjust itself after a change of external voltage which leads to an upper limit for thef. Lproduct (about 10⁸cm/s). The essential feature of the amplifier circuit is to provide both a short circuit at the Gunn oscillation frequency and a broadband circuit at the signal frequency. An average gain of 3 dB was exhibited from 5.5 GHz to 6.5 GHz. Gain compression of 1 dB occurred at 60 mW output power with 9 dB gain, while the noise figure was about 19 dB.     

Comparison between regenerative-feedback and cofeedback gain-clamped EDFA

The erbium-doped fiber amplifier (EDFA) with regenerative feedback is compared with the cofeedback scheme. Without the bandpass filter, the injected signal experiences regenerative amplification and results in a higher signal gain. Such an above-threshold regenerative amplifier also exhibits a lower noise figure due to a higher inversion for the transition corresponding to the signal wavelength of 1550 nm. A near quantum-limited noise figure of 3.1 dB is achieved at the maximum pump power of 134.5 mW, showing nearly complete inversion at the EDF input end in the regenerative-feedback scheme. A low (<10/sup -10/) bit-error rate has been achieved with saturation input signal power above -12 dBm.     

System design and optimization of optically amplified WDM-TDMhybrid polarization-insensitive fiber-optic Michelson interferometricsensor

We investigate the optically amplified time-division-multiplexed (TDM) polarization-insensitive fiber-optic Michelson interferometric sensor (PIFOMIS) system using erbium-doped fiber amplifier (EDFA). The EDFA was named preamplifier, in-line amplifier or postamplifier; by the position it was located. We find that the preamplifier EDFA has limited usefulness because of its unstable amplification of the optical pulse trains. Both post- and in-line cases can work successfully in the TDM-PIFOMIS system. The amplitudes of the optical pulse trains are stable after amplified by the in-line EDFA, this is a significantly advantage of the optically amplified TDM-PIFOMIS system. The MPDS of the unamplified TDM-PIPOMIS system with an extinction ratio (ER) of 33 dB of the output pulse of the optical guide wave (OGW) modulator was 2.4×10^-5 rad/(Hz)^1/2 at 1 kHz. For maintaining MPDS better than 3.4×10^-5 rad/(Hz)^1/2 at 1 kHz, the allowable worst ER for the post- and in-line amplified system are 20 and 17.8 dB, respectively, and the corresponding input signal peak power should be larger than -20 and -25 dBm. While employing such two post- and two in-line EDFAs in the TDM-PIFOMIS system, the allowable loss of the sensor array is 47 dB. We analyze the phase-induced intensity noise (PIIN) of the optically amplified TDM-PIFOMIS system in detail and propose methods to reduce the PIIN. The output optical pulse of an intensity modulator with high ER is a key issue to minimize the PIIN and sensor crosstalk in the system. In order to reduce the system PIIN, complexity and cost, we suggest an optimum optically amplified WDM (wavelength-division multiplexing)-TDM hybrid PIFOMIS system with four wavelengths and four eight-sensor subarrays     

X波段捷变频率源设计

文章介绍了一种捷变频率源的设计方案。该方案设计的捷变频率源由10个不同频率的介质振荡器、十选一高速开关以及功率放大器三部分组成。在设计方案中,10个振荡器同时加电工作,输出频率信号到十选一开关,由TTL信号控制开关选通一路信号输出到功率放大器,功率放大器放大该信号并输出。该设计的主要特点是:高低温下频率误差小于0.3 MHz,输出功率大于10 dBm,相位噪声小于-75 dBc/Hz/10 kHz,杂波抑制大于65 dBc。文中给出了设计过程、样品研制以及测试结果。     

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     

1.5 µm GaInAsP traveling-wave semiconductor laser amplifier

This paper presents a theoretical and experimental study in terms of small-signal gain, signal gain saturation, and noise characteristics of a 1.5 μm GaInAsP traveling-wave amplifier (TWA), realized through the application of SiOxfilm antireflection coatings. This TWA, having a residual facet reflectivity of 0.04 percent, exhibits a wide, flat signal gain spectrum and a saturation output power of +7 dBm at a 20 dB signal gain. The TWA also has a noise figure of 5.2 dB, which is the smallest value reported for semiconductor laser amplifiers. The experimental results are confirmed to be in good agreement with the theoretical predictions based on the multimode traveling-wave rate equations in conjunction with the photon statistic master equation analysis, which takes into account the amplifier material and device structural parameters. Signal gain undulation, saturation output power, and noise figure are also theoretically evaluated as functions of the facet reflectivity. The superior performance of the TWA demonstrates that the device is favorable for use in linear optical repeaters in fiber transmission systems.     

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     

On the Temperature-Dependent Gain and Noise Figure Analysis of C-Band High-Concentration EDFAs With the Effect of Cooperative Upconversion

We present an efficient temperature-dependent analysis to study the effect of cooperative upconversion on the temperature-dependent gain (TDG) performance of the C-band erbium-doped fiber amplifier (EDFA) at high-concentration. The influence of cooperative upconversion on the TDG is examined by using a set of temperature-dependent rate and light propagation equations. In the analysis given, the amplified spontaneous emission (ASE), as well as the excited state absorption (ESA) are also considered. In the forward pumping configuration at a signal wavelength of 1547 nm and in the temperature range of - 40degC to + 80degC, the variations of the TDG and the noise figure (NF) are about 1.7 and 0.9 dB, respectively. Numerical analysis results show that, with 260-mW/1480-nm pump power, an erbium-doped fiber amplifier having a doping concentration of 4.4 times 10²⁶ ion/m³ and optimum length of 9.2 cm may reach a signal gain of 44.6 dB and a noise figure of 3.9 dB at room temperature.     

Full-Field Electronic Dispersion Compensation of a 10 Gbit/s OOK Signal Over 4$,times,$ 124 km Field-Installed Single-Mode Fibre

We experimentally demonstrate the use of full-field electronic dispersion compensation (EDC) to achieve a bit error rate of 5times10^{- 5} at 22.3 dB optical signal-to-noise ratio for single-channel 10 Gbit/s on-off keyed signal after transmission over 496 km field-installed single-mode fibre with an amplifier spacing of 124 km. This performance is achieved by designing the EDC so as to avoid electronic amplification of the noise content of the signal during full-field reconstruction. We also investigate the tolerance of the system to key signal processing parameters, and numerically demonstrate that single-channel 2160 km single mode fibre transmission without in-line optical dispersion compensation can be achieved using this technique with 80 km amplifier spacing and optimized system parameters.     

CMOS超宽带低噪声放大器的设计

由于超宽带技术能够在短距离内传输几百兆的数据,帮助人们摆脱对导线的依赖,因此使得大带宽数据的无线传输从几乎不可能变为现实。尽管目前超宽带技术的标准还没有统一,但是低噪声放大器终归是其接收机中一个不可或缺的重要模块。文章介绍了一种基于0.18μmCMOS工艺、适用于超宽带无线通信系统接收前端的低噪声放大器。结合计算机辅助设计,该超宽带低噪声放大器输入、输出均实现良好的阻抗匹配,在3GHz～10GHz的频带范围内实现了增益G=29±1dB,噪声系数小于4dB。在1.8V工作电压下放大器的直流功耗约为35mW。     

High-output-power polarization-insensitive semiconductor optical amplifier

A high-output-power 1550 nm polarization-insensitive semiconductor optical amplifier (SOA) was developed for use as a compact in-line optical amplifier. A very thin tensile-strained bulk structure was used for the active layer and active width-tapered spot-size converters (SSCs) were integrated on both input and output sides. The SOA module exhibited a high saturation output power of +17 dBm together with a low noise figure of 7 dB, large gain of 19 dB, and low polarization sensitivity of 0.2 dB for optical signals of 1550 nm wavelength. For the amplification of optical signals modulated at 10 Gb/s in the nonreturn-to-zero (NRZ) format, a good eye pattern without waveform distortion due to the pattern effect was obtained at an average output power of up to +12 dBm. Additionally, good amplification characteristics were demonstrated for the signal wavelength range corresponding to the C-band.     

Comparison between NRZ and RZ signal formats for in-line amplifiertransmission in the zero-dispersion regime

Nonreturn-to-zero (NRZ) and return-to-zero (RZ) signal formats are experimentally and numerically compared for single-channel long-distance transmission in an in-line amplifier system with dispersion management providing average zero dispersion and local nonzero dispersion at an interval equal to the in-line amplifier spacing. Among a 20-ps RZ signal, a 40-ps RZ signal, and an NRZ signal transmitted in 10 Gb/s straight-line experiments, the last signal achieves the longest transmission distance of 6000 km while the others are limited to 4400 km. Numerical simulations explain these results well and show that, along with linear amplified spontaneous emission (ASE) accumulation, signal waveform distortion due to the combined effect of higher order group-velocity dispersion (GVD) and self-phase modulation (SPM) dominates the performance. Nonlinear optical noise enhancement is not obvious because of the fiber dispersion arrangement. Signals with large pulse widths are less affected by the combined effect, while small-width signals yield superior initial signal-to-noise ratio (SNR) as determined by optical noise. A detailed simulation indicates that a pulse width of about 60 ps is optimum for long distance transmission under the fiber dispersion arranged in this paper     

宽带高增益输出平衡CMOS低噪声放大器的设计

设计了一种带片内变压器、适用于0.05～2.5 GHz频段的宽带低噪声放大器(LNA).电路设计采用了并行的共栅共源放大结构,将从天线接收到的单端输入信号转换为一对差分信号输出给后级链路.针对变压器结构的LNA噪声系数不够低和输出不平衡的问题,采用了缩放技术、噪声消除技术以及两级的全差分放大器作为输出缓冲级,来有效降低电路的噪声系数,提高增益和输出平衡度.电路采用TSMC 0.18μm 1P6M RF CMOS工艺设计仿真和流片,测试结果表明:在0.05 ～ 2.5 GHz频带范围内,该LNA的最高功率增益达24.5 dB,全频段内噪声系数为2.6～4 dB,输入反射系数小于-10 dB,输出差分信号幅度和相位差分别低于0.6dB和1.8°.     

Power Amplification of Microwave FM Communication Signals Using a Phase-Locked Voltage-Tuned Oscillator

An analog phase-locked oscillator is used as a power amplifier for FM communications signals. Intended service is for FDM telephone message service or television relay. The output power is generated in a varactor-tuned oscillator, which is synchronized with a weak input signal using a phase-lock loop. This involves a phase detector and a wide-band direct-coupled video amplifier whose output is applied to the tuning varactor. The paper is largely theoretical, relating the parameters of the feedback loop to the performance of the overall device. Explicit expressions are derived for the noise figure, the frequency response of the modulation characteristic, AM-PM conversion, and nonlinearity effects in terms of differential gain and intermodulation. In addition, two experimental models are described, together with certain measured data. The phase-lock method differs in many ways from multistage reflection amplifiers and appears to offer advantages for many applications. The device has adequate bandwidth and linearity for a single FDM-FM signal with 1800 or more channels, but must be tuned to the intended frequeucy. Tuning procedures are simple. High gain of 25-35 dB is obtainable in a single microwave "stage." Most of this gain may be associated with the functions of phase detection, video amplification, and VCO tuning. Of major importance, with respect to noise, is that the device is functionally equivalent to a high-gain low-noise microwave preamplifier followed by a low-gain power amplifier stage in which the preamplifier has the noise figure of the phase detector combined with the video amplifier, and the power stage has a noise figure appropriate to the class of power diode used. FM noise generation is substantially lower than in a high-gain reflection amplifier using the same class of microwave power diode throughout.     

A 0.6-V Low Power UWB CMOS LNA

This paper presents the design of a low-power ultra-wideband low noise amplifier in 0.18-mum CMOS technology. The inductive degeneration is applied to the conventional distributed amplifier design to reduce the broadband noise figure under low power operation condition. A common-source amplifier is cascaded to the distributed amplifier to improve the gain at high frequency and extend the bandwidth. Operated at 0.6V, the integrated UWB CMOS LNA consumes 7mW. The measured gain of the LNA is 10dB with the bandwidth from 2.7 to 9.1GHz. The input and output return loss is more than 10dB. The noise figure of the LNA varies from 3.8 to 6.9dB, with the average noise figure of 4.65dB. The low power consumption of this work leads to the excellent figure of gain-bandwidth product (GBP) per milliwatt     

Design considerations and operating characteristics of high-poweractive grating-surface-emitting amplifiers

An analysis of the characteristics and optimization of the design parameters of active-grating surface emitting amplifiers is presented. It is concluded that coherent power outputs of more than 1 W with ⩽30 dB of amplified spontaneous emission noise power contained in the far-field beam divergence of the coherent output are expected for amplifier lengths greater than 0.5 cm. The effects of end reflections on the active-grating amplifier power output are also considered, and it is found that end reflections of 10^-3 or less should have a negligible effect on the power output     

Structural modification of semiconductor optical amplifiers for wavelength division multiplexing systems

In this paper, the semiconductor optical amplifier is analyzed for in-line and pre-amplifier for wavelength division multiplexing (WDM) transmission having minimum crosstalk and power penalty with sufficient gain. It is evaluated that the cross gain saturation of the SOA can be reduced by settling crosstalk at lower level and also minimizing the power penalty by slight increase in the confinement factor. At an optimal confinement factor of 0.41069, high amplification is obtained up to saturation power of 20.804 mW. For this confinement factor, low crosstalk of −9.63 dB and amplified spontaneous emission noise power of 119.4 μW are obtained for −15 dBm input signal. It has been demonstrated for the first time that twenty channels at 10 Gb/s WDM can transmit up to 5600 km by use of this optimization. In this, cascading of in-line SOA is done at the span of 70 km for return zero differential phase shift keying modulation format with the channel spacing of 100 GHz. The optical power spectrum and clear eye are observed at the transmission distance of 4340 and 5600 km in RZ-DPSK system. The bit error rate for all channels increases more than 10⁻¹⁰ with the increase in launched input power.