共查询到20条相似文献,搜索用时 0 毫秒
1.
The required frequency spacings between channels in an optical frequency division multiplexing (FDM) network are considered. The minimum permissible spacings consistent with meeting bit error rate (BER) objectives are derived. The assumed transmission uses on-off keying (OOK), at a data rate 1/T (in bits per second), via external modulation of a laser source having linewidth β (in hertz). The assumed receiver consists of an optical channel selection filter followed by a p-i-n photodiode and a postdetection integrate-and-dump circuit. The analysis estimates the adjacent channel interference (ACI)-induced floor on BER for the middle of three FDM channels, as a function of frequency spacing and linewidth-to-bit rate ratio (βT ). For BER=10-9 and βT ranging from 0.32 to 5.12, the required channel spacing ranges from 5.2 to 27.5 bit rates. The multiplying factors associated with using (wide-deviation) frequency shift keying (FSK), coherent (heterodyne) detection, and infinitely many FDM channels, respectively, are estimated to be 2.0, at most 3.0, and at most 1.37 相似文献
2.
Coherent detection of optical quadrature phase-shift keying signals with carrier phase estimation 总被引:2,自引:0,他引:2
This paper describes a coherent optical receiver for demodulating optical quadrature phase-shift keying (QPSK) signals. At the receiver, a phase-diversity homodyne detection scheme is employed without locking the phase of the local oscillator (LO). To handle the carrier phase drift, the carrier phase is estimated with digital signal processing (DSP) on the homodyne-detected signal. Such a scheme presents the following major advantages over the conventional optical differential detection. First, its bit error rate (BER) performance is better than that of differential detection. This higher sensitivity can extend the reach of unrepeated transmission systems and reduce crosstalk between multiwavelength channels. Second, the optoelectronic conversion process is linear, so that the whole optical signal information can be postprocessed in the electrical domain. Third, this scheme is applicable to multilevel modulation formats such as M-array PSK and quadrature amplitude modulation (QAM). The performance of the receiver is evaluated through various simulations and experiments. As a result, an unrepeated transmission over 210 km with a 20-Gb/s optical QPSK signal is achieved. Moreover, in wavelength-division multiplexing (WDM) environment, coherent detection allows the filtering of a desired wavelength channel to reside entirely in the electrical domain, taking advantage of the sharp cutoff characteristics of electrical filters. The experiments show the feasibility to transmit polarization-multiplexed 40-Gb/s QPSK signals over 200 km with channel spacing of 16 GHz, leading to a spectral efficiency as high as 2.5 b/s/Hz. 相似文献
3.
Fady I. El-Nahal 《光电子快报》2018,14(5):372-375
Coherent optical fiber communications for data rates of 100 Gbit/s and beyond have recently been studied extensively because high sensitivity of coherent receivers could extend the transmission distance. Spectrally efficient modulation techniques such as M-ary phase shift keying (PSK) can be employed for coherent optical links. The integration of multi-level modulation formats based on coherent technologies with wavelength-division multiplexed (WDM) systems is vital to meet the aggregate bandwidth demand. This paper reviews coherent quadrature PSK (QPSK) systems to scale the network capacity and maximum reach of coherent optical communication systems to accommodate traffic growth. 相似文献
4.
The error performance of coherent detection of binary phase shift keying (BPSK) signals with noisy phase reference is analysed for a flat Nakagami-m fading channel and in the presence of additive white Gaussian noise (AWGN). By assuming Gaussian and Tikhonov probability density functions (PDFs) for the phase error, closed-form expressions for the average bit error rate (BER) are derived 相似文献
5.
为有效利用信道资源,基于扩展二元相移键控(Extended Binary Phase Shift Keying,EBPSK)调制和解调的独特性,分析了多载波EBPSK调制的传输体制,推导出各路调制信号间参数约束关系,找出传输信号频谱变化规律,提出两种传输方案并设计相应的解调器,实现了多路EBPSK信号的并行传输;针对线谱分布规律修改调制波形,抑制了调制信号功率谱中的线谱杂散;取不同组调制参数进行仿真验证,结果表明两种方案的解调性能趋于一致且与载频间隔有关,载频趋近,系统实现复杂度提高,在相同误码率下解调所需信噪比额外支出约1~2 dB,但传输速率成倍提高,节省了频率资源,表明了这两种方法的可行性、有效性和利用信道资源的合理性. 相似文献
6.
The paper considers an algorithm for coherent reception of signals with multiparameter polarization-phase keying. An asymptotic
expression is derived for the average probability of symbol error depending on signal-to-noise ratio. Comparative assessment
of this probability is performed for different ensembles of signals with multiparameter polarization-phase keying.
Original Russian Text ? Yu. V. Zapletin, V.V. Liventsev, 2007, published in Izvestiya VUZ. Radioelektronika, 2007, Vol. 50,
No. 4, pp. 51–58. 相似文献
7.
The key synchronization aspects in the system design of a QQPSK (quadrature-quadrature phase-shift-keying) modem are addressed. The sensitivity of the data demodulator to synchronization errors is discussed, and contextually the performances of some IF and baseband carrier phase and symbol timing recovery schemes are evaluated both theoretically and by computer simulations. In particular, a fourth-power IF carrier/clock regenerator and two baseband clock recovery schemes, with and without the aid of data decisions, respectively, are taken into account. The analysis shows on the one hand the substantial robustness of QQPSK to carrier phase errors and the adequacy of the examined carrier extraction scheme. On the other hand, the remarkable sensitivity of QQPSK to symbol timing inaccuracy is stressed and the need to resort to the newly proposed decision-aided baseband clock recovery scheme is pointed out 相似文献
8.
The paper describes a new superfast digital converter with phase-shift keying designed for transforming optical amplitude-modulated
signals to microwave oscillations with phase keying.
Original Russian Text ? M. Ye. Il’chenko, O.V. Asmolova, 2007, published in Izvestiya VUZ. Radioelektronika, 2007, Vol. 50,
No. 4, pp. 77–80. 相似文献
9.
The sensitivity of an optical homodyne receiver with practical degradations is analytically evaluated using a semiclassical photodetection model which is valid for arbitrarily low levels of local oscillator (LO) power. This model provides several important advantages over the usual treatment in which large LO is assumed. In addition to giving an intuitive picture of the evolution of the detection sensitivity from the direct detection case (LO=0) to the shot noise limited coherent detection case (large LO), it allows for a quantitative comparison between degradations caused by some important receiver nonidealities for the two limiting cases. Sensitivity loss due to dark current, thermal noise, and electronic distortion is evaluated and the LO power required to reach shot noise limited operation in the presence of these degradations is determined 相似文献
10.
This article investigates the asymptotic error-rate behavior for the noncoherent on-off keying (OOK) signaling scheme in different fading environments and at both extremes of the signal-to-noise ratio (SNR). A transcendental equation to compute the optimum threshold level of noncoherent OOK operating over a Rician fading channel is derived. The optimum threshold level and its corresponding ratio of the mark and space error probabilities in additive white Gaussian noise (AWGN). Rayleigh, and Rician channels are tabulated as a function of the SNR. Geist (see ibid., vol.42, p.225, 1994) has shown that mark and space errors contribute equally to the average error probability in an AWGN channel when the SNR is large with optimum threshold setting. We show that mark errors predominate when the SNR is small and/or in fading channels 相似文献
11.
The authors analyze the performance of receivers that use envelope detection at an IF to detect optical signals with orthogonal modulation formats. Exact closed-form expressions for the error probability conditioned on the normalized envelope were obtained. The only information necessary for obtaining the unconditional error probability is a small set of tilted moments of the envelope. The authors then provide an approximation to this envelope which is not only accurate to the first order in phase noise strength, but also has the same range as the actual random envelope. This approximation was used to obtain the bit error performance of the three receiver models considered. A tight lower bound in closed form is given. The analysis is extended to the case of N -ary frequency-shift-keying (FSK) to provide very tight upper and lower bounds to the bit error probability 相似文献
12.
13.
《Optical Fiber Technology》2013,19(5):514-517
This paper proposes an opto-electrical feed-forward circuit that reduces phase noise in binary PSK signals by averaging the noise. Random and independent phase noise is averaged over several bit slots by externally modulating a phase-fluctuating PSK signal with feed-forward signal obtained from signal processing of the outputs of delay interferometers. The simulation results demonstrate a reduction in the phase noise. 相似文献
14.
Time domain phase noise correction for OFDM signals 总被引:2,自引:0,他引:2
《Broadcasting, IEEE Transactions on》2002,48(3):230-236
We introduce an algorithm for compensating for carrier phase noise in an OFDM communication system. Through the creation of a linearized parametric model for phase noise, we generate a least squares (LS) estimate of the transmitted symbol. Using digitized DVB-T RF signals created in a laboratory and a DVB-T compliant receiver model, simulation results are presented to evaluate the effectiveness of the algorithm in practical environments. 相似文献
15.
There are several applications of highly coherent semiconductor lasers, especially in coherent optical-fibre communications systems and optical-fibre sensors. Optical phase noise is extremely important in these applications. Here we report preliminary results from a simple technique whereby phase noise in semiconductor lasers may be reduced. Initial results demonstrate a phase-noise reduction of typically 20 dB. Developments of the technique should permit reduction towards the shot noise limit. 相似文献
16.
The amplifier is based on the optical Kerr effect in waveguides with large third-order nonlinear susceptibility. The short response time of the Kerr effect gives the device an extremely large bandwidth, exceeding that of any laser amplifier. Also, for binary signals, the amplifier is shown to have a phase regenerative effect. Examples of signal and pump powers are given for polydiacetylene waveguides 相似文献
17.
针对α稳定分布噪声环境下数字通信信号的二阶与高阶循环统计特征显著退化问题,结合分数低阶矩和共变理论对二进制频移键控(Frequency Shift Keying,FSK)信号的分数低阶循环谱公式进行了理论推导,并对2FSK信号在不同混合信噪比、分数阶因子和特征指数条件下的分数低阶循环谱进行了详细的仿真分析.理论和仿真结果表明:2FSK信号分数低阶与二阶的循环谱结构相同,其谱峰对应的循环频率相同,谱峰的幅度值不同,取决于循环谱的阶因子.相对于在低混合信噪比下失效的二阶循环谱,分数低阶循环谱对α稳定分布噪声具有更强的抗干扰性和适用性. 相似文献
18.
《Lightwave Technology, Journal of》2005,23(5):1866-1873
Taking into account the influence of group-velocity dispersion (GVD) and the nonlinear Kerr effect, the nonlinear amplification of the amplified spontaneous emission (ASE) noise in fiber transmission systems using optical phase conjugation (OPC) is studied. Under a path-averaged power approximation for long-haul transmission systems, an equivalent system is developed to evaluate ASE noise amplification and accumulation in OPC systems. Combining the theoretical analysis and numerical simulations, the noise suppression effect in OPC systems is demonstrated and discussed. By using the numerical calculation method, the power variation along the system is involved in the evaluation of noise amplification. It is shown that the power variation through the system results in an imperfect compensation of the modulation instability (MI) effect, which furthermore causes the degradation of the noise suppression performance in OPC systems with anomalous dispersion. 相似文献
19.
A possible way to design photonic switch matrices is by interconnecting multiple 2×2 switches based on semiconductor optical amplifier gates. The size of these matrices is limited by many phenomena including phase noise from the gates. The authors examine the limitations imposed by this noise in a system using DPSK direct detection 相似文献
20.
Wenke Yu Dan Lu Dong Wang Caiyun Lou Li Huo Shilong Pan 《Optical Fiber Technology》2012,18(2):117-120
We propose a simple and novel format conversion scheme based on a polarization modulator (PolM) and a zero-chirp intensity modulator (IM) to perform NRZ to RZ conversion for quaternary amplitude-shift keying (4-ASK) signals. Simulation shows that the scheme is capable of realizing format conversion from 20-Gbit/s NRZ-4-ASK signal to RZ-4-ASK signal with tunable pulse-width for 4-level intensity modulation format. The converted signals can transmit over a dispersion-managed fiber link from 200 km to 300 km confirming the high quality conversion. 相似文献