共查询到20条相似文献,搜索用时 31 毫秒
1.
A theoretical study of channel crosstalk due to gain saturation in a laser amplifier in multichannel transmission is discussed. When the amplifier is gain-saturated, the gain of any channel is influenced by the light intensity of the other channels, which causes channel crosstalk in intensity-modulated multiplexing transmission. On-off-keying modulation systems with more than two channels are discussed. Considering the probability distribution, the power penalty due to crosstalk is presented for practical system design. Calculated examples reveal that the power penalty is dependent on both the level of gain saturation and the number of multiplexed channels 相似文献
2.
A new method to equalize power imbalance caused by Raman-induced crosstalk among optical channels is proposed using a lumped germanosilicate fiber Raman amplifier. Evolution of optical channels through the Raman amplifier was simulated using Raman frequency modeling, which theoretically predicted simultaneous amplification and power equalization. Experimentally, a gain band with negative slope in the range of 1.571-1.591 μm was achieved in a lumped Raman amplifier pumped by a broad-band laser diode centered at 1.467 μm. We demonstrated compensation of the Raman-induced crosstalk of 5 dB accumulated along 330 km of conventional single-mode fiber 相似文献
3.
Nonlinear distortion in the adjacent channels of an X-band amplifier driven by an ultra-wideband digitally-modulated carrier is analyzed. Statistical properties of the input signal with a complex power series-based behavioral model of the amplifier are used to calculate the output power spectrum. Comparisons are made between measured and predicted adjacent channel power rejection for the X-band monolithic microwave integrated circuit. 相似文献
4.
Gholamreza Karimi Ali Lotfi 《AEUE-International Journal of Electronics and Communications》2013,67(8):723-728
In this paper, a novel pre-distorter is presented using the particle swarm optimization (PSO) for an RF power amplifier linearization has been presented. We used the PSO in order to design of an efficient pre-distorter for the linearization of the output of an RF power amplifier by using the output data of the proposed power amplifier. The PSO is implemented to estimate and optimize the coefficient parameters of the work function in the proposed pre-distorter block diagram. The proposed method using PSO is most efficient because this approach is independent of the output of the power amplifier. The proposed method has been simulated with two-tone input signal and output power spectrum has been compared, where the obtained adjacent channel leakage ration (ACLR) is better than 50 dBc for both channels. Therefore, a quite significant improvement in linearity is achieved. 相似文献
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The authors present and discuss fundamental limitations for erbium-doped fiber amplifier (EDFA)-based subcarrier-multiplexed AM-VSB CATV distribution systems. The impairments they consider are shot noise, amplifier spontaneous emission noise, and laser clipping-induced nonlinear distortion. Treating the amplifier input signal power and pump power as resources, they obtain limits on the number of receivers to which one can deliver, say, 60 (or 80) channels at a carrier-to-noise ratio (CNR) of 55 dB (or 48 dB). A simple approach that can be used to recalculate the results presented here for different system and amplifier fiber parameters is presented 相似文献
7.
A communications theory equivalent model suitable for analyzing carrier-density modulation effects within a traveling-wave semiconductor optical amplifier is derived by linearizing the amplifier rate equation. This model is used to analyze dual-channel amplification, and it is shown to give results which are in good agreement with those given by nonlinear polarization theory and experimental measurements. The effect of four-wave mixing on the amplification of many optical channels for worst-case operating conditions is studied, and it is shown that the individual channels experience different gains. It is also shown that if the individual channel gains are to be confined to lie within a ±1-dB band when operating the amplifier at high values of unsaturated power gain 相似文献
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9.
This paper presents a low-power imaging diversity front-end receiver employing the maximum-ratio-combining algorithm for free-space
optical communication. It consists of seven signal channels and an output stage, each channel has a front-end transimpedance
amplifier, a signal-to-noise ratio (SNR) estimator and a variable gain amplifier (VGA). The imaging receiver circuit was implemented
in a 90 nm CMOS process. The maximum-ratio weighting is achieved with the SNR estimator and variable gain amplifier (VGA),
which provides the signal with a gain proportional to the signal amplitude. The maximum ratio combining feature was demonstrated
with two channels driven by photodiode emulation circuits for electrical characterization. The power dissipation for the whole
chip is 43 mW from a single 1.2 V supply. 相似文献
10.
Motoshima K. Suzuki N. Shimizu K. Kasahara K. Kitayama T. Yasui T. 《Lightwave Technology, Journal of》2001,19(11):1759-1767
The design scheme for an erbium-doped fiber amplifier (EDFA) with automatic channel-by-channel gain and power regulation function is discussed with much emphasis on the pump power control scheme and the requirement for feedback circuitry. Based on both wavelength and time-resolved simulation technique, an amplifier repeater employing novel high-speed automatic gain control (AGC) and automatic level control (ALC) functions is designed and implemented. The AGC and ALC scheme can suppress the transient power fluctuation of a surviving channel caused by adding or dropping all other channels less than 0.45 dB and keep output power constant over 9-dB input power range 相似文献
11.
Bo-Hun Choi Chang-Bong Kim Jesoo Ko 《Photonics Technology Letters, IEEE》2007,19(18):1353-1355
We propose and demonstrate the scheme to combine a two-staged amplifier with a fixed gain flattening filter and two parallel optical feedback loops. This amplifier all-optically controls constant signal gain and gain level through all C-band with a dynamic input power range of up to -1 dBm while input signals are dynamically changed between one channel and 40 wavelength-division-multiplexing channels. The transient effects of each channel and their wavelength dependency are investigated. It is shown that the amplifier can be used in real field applications through transmission experiments, in which the amplifier performance is kept unchanged under wide dynamic traffic variance. 相似文献
12.
In this paper, we propose a fiber amplifier gain equalizer using a coherent optical transversal filter. The gain equalizer is tunable and has a bandwidth in the order of 30 nm. We also study the effects of different parameters such as input signal power pattern and the input pump power on the gain profile of the amplifier. The results show that, when the input signal power pattern changes, the amplifier does not maintain its gain profile. The gain profile has to be maintained in order to make the gain equalization effective. We show that, the pump input power can be adjusted so that the changes in the gain profile are compensated for. The gain profile varies quite slowly, hence compensation is feasible. As an example, we discuss the design of a gain equalizer for a system consisting of seven wavelength channels 相似文献
13.
基于速率方程的离散算法,实现了对双包层Er^3+/Yb^3+光纤放大器动态特性的分析。研究了不同信号和泵浦功率下单信道的瞬态功率、脉冲序列输出功率与增益随时间的变化以及多信道异步转移模式下输出功率和增益随时间的变化。结果表明:对于单个脉冲,在相同的泵浦功率下,输出脉冲的峰值功率取决于输入脉冲的峰值功率;在不同的泵浦功率下,输出脉冲的峰值功率取决于泵浦功率。对于脉冲序列,在达到稳定的输出前,将经历一个输出功率和增益由高到低的变化过程。对于异步转移模式的多信道脉冲,脉冲重叠时的功率和增益变化要快于非重叠时功率和增益的变化。 相似文献
14.
Effects of Power Amplifier Distortion and Carrier Frequency Offset on the Performance of WLAN System
Zi-Wei Zheng 《Wireless Personal Communications》2011,57(4):575-589
Due to the efficiency of mitigation multipath delay spread, orthogonal frequency division multiplexing (OFDM) is extensively
used in the wireless local area network (WLAN) domain, such as the IEEE 802.11a standard defined by the IEEE 802.11 standardization
group and the HIPERLAN/2 defined by the European Telecommunication Standards Institute Project on Broadband Radio Access Networks.
OFDM based WLAN system is very sensitive to the power amplifier distortion and the carrier frequency offset. The performance
of the OFDM based WLAN system in the presence of the power amplifier distortion and the carrier frequency offset under practical
fading channel is researched and analyzed in this paper. A closed form of bit error rate (BER) is derived for the OFDM based
WLAN system in the presence of the power amplifier distortion and the carrier frequency offset under practical fading channel.
The effects of the power amplifier distortion and the carrier frequency offset on the OFDM based WLAN system performance are
comparatively studied by the theoretical method and by the simulation method under practical multipath fading channels. Studies
show that the theoretical and simulated results match well. 相似文献
15.
Glance B.S. Eisentein G. Fitzgerald P.J. Pollock K.J. Raybon G. 《Lightwave Technology, Journal of》1989,7(5):759-765
The crosstalk degradation caused by an optical amplifier in a four-channel FSK (frequency-shift-keyed) heterodyne communication system is measured. A bit error rate (BER) floor of 3×10-4 is observed when the channels are spaced by 200 MHz, FSK modulation at 45 Mb/s, and when the optical input signal is large enough such that the gain is compressed by 2 dB relative to its small-signal value. The receiver is substantially improved by reducing the optical power amplifier input. However, the sensitivity increases only to a maximum value beyond which it degrades as the optical power of the demodulated channel becomes small relative to the noise of the optical amplifier. The combined effect of the crosstalk and the amplifier noise yields an optimum sensitivity of 250 photons/b for BER=10-9. This result is 5 dB poorer than the sensitivity obtained in the absence of an optical amplifier 相似文献
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Signal gain saturation and crosstalk characteristics in two-channel common amplification were investigated using a 1.5?m travelling-wave laser amplifier. Simultaneous amplification in the two channels causes gain saturation of the other, which results in an approximate 3 dB reduction in saturation output power. The total output power is confirmed to dominate the gain saturation in laser amplifiers. 相似文献
18.
《Lightwave Technology, Journal of》2009,27(2):88-93
19.
设计一种数字控制的高增益宽带宽放大器,提出了采用多个放大器直接耦合级联方式,通过理论分析合理选择各级增益的分配,明显改善了放大器的低频特性,极大地提高了增益范围。系统由前置放大电路、程控增益放大电路、通频带选择电路、功率放大电路、单片机控制电路以及电源模块6个部分组成。其中通频带选择电路由两路巴特沃斯低通滤波器组成,可实现通频带的切换;功率放大电路由多个高速缓冲芯片BUF634并联组成,扩大了电流输出范围,实现了功率放大;单片机控制电路以MSP430G2553为主控芯片,使用液晶12864实现显示功能,人机界面友好。经测试,本系统能够完成0~10MHz频率范围内的0~80dB增益步进可调功能。在增益为60dB时,输出电压噪声峰峰值小于0.3V,很好的完成了系统的设计指标。 相似文献
20.
Mahdi M.A. Poopalan P. Selvakennedy S. Ismail N. Ahmad H. 《Photonics Technology Letters, IEEE》1999,11(12):1581-1583
All optical gain-locking in an erbium-doped fiber amplifier (EDFA) is demonstrated. A double-pass superfluorescence is created by using a broad-band fiber reflector centered at 1530 nm at the output of the EDFA, to lock the gain at 21 dB. Experiments on an eight-channel wavelength-division-multiplexing system shows promise with gain variation between channels of less than 0.6 dB over the input signal power range. While, gain variation with input signal power is about 0.2 dB for all channels 相似文献