大气折射和色散对激光传输的影响

由于大气折射和色散效应,当用可见光或红外线瞄准目标而用另一波长的激光对目标进行探测或打击时,瞄准路径和激光传输路径是不一样的,瞄准点和激光束之间存在误差。本文建立了大气层折射模型,并给出了在不同仰角时,用可见光(0．55μm)和红外线(4μm)进行瞄准、用CO2激光器对10km远的目标进行探测或打击,瞄准点和CO2激光束之间的距离大小。     

Analytical model for the performance evaluation of DWDM transmission systems

We present a novel analytical model to assess the signal quality in nonlinear dense wavelength-division-multiplexed (DWDM) transmission. The nonlinear impairment dependence on various system parameters is reported. The good agreement with numerical simulations indicates that the proposed model can be of significant value in the search for optimized DWDM systems.     

Experimental evaluation of chromatic dispersion distortion inoptical CPFSK transmission systems

Receiver sensitivity degradations due to fiber chromatic dispersion without chromatic dispersion compensation in multigigabit optical continuous-phase frequency-shift-keying (CPFSK) transmission systems are evaluated experimentally and theoretically. Transmission distance limited by the chromatic dispersion of 15 ps/nm/km is estimated to be 130 km at 5 Gb/s and 33 km at 10 Gb/s     

Impact of fiber chromatic dispersion in high-speed TDM transmission systems

General guidelines for high-speed time-division multiplexing (TDM) data-rate transmission are essential for the increase of the overall transmission capacity. In this paper, general theoretical investigations concerning fiber chromatic dispersion in optical TDM systems are performed. Recent experiments that confirm the theoretical predictions are presented. Nonzero dispersion-shifted fiber and standard single-mode fiber are recommended for 40 and 160 Gb/s, respectively, independent of the chromatic dispersion compensation scheme.     

光纤色散和非线性对DWDM系统的影响及其消除

围绕光纤色散和非线性效应对DWDM系统传输限制的问题进行了深入的讨论。提出消除限制DWDM传输的有效方法。     

Improved chromatic dispersion tolerance for optical duobinary transmission using coherent detection

The impact of chromatic dispersion on the complex electric field of an optical phase-coded duobinary signal is investigated through numerical simulation. Dispersion causes distortion and rotation of the optical constellation with increasing transmission distance, leading to eye closure of the received signal. When direct detection is employed, rapid eye closure starts after approximately 213 km. Employing coherent detection increases this dispersion limit by 70 km.     

On the impact of filter dispersion slope on the performance of 40 Gbps DWDM systems and networks

A technique to separate the phase-induced penalty of a cascade of optical filters into dispersion, dispersion slope, and higher-order terms is introduced and its impact on the proper design and engineering of high-speed Dense Wavelength Division Multiplexed (WDM) optical systems and networks is demonstrated. As the currently deployed fiber optic systems and networks strive for higher speeds to respond to the growing global needs for more bandwidth, the impact of physical layer impairments (such as optical filter dispersion slope) which were not significant at lower speeds are now becoming increasingly important and worth looking at. In this article we demonstrate that at speeds of 40 Gbps and beyond, where the next generation systems will be operating, optical filter dispersion slope is at least as important as filter dispersion. As a result, separating the above contributions and accounting for each using the described modeling technique proves to be an effective way for designing and engineering such systems.     

Performance of non-fibre based dispersion compensation for long-haul 10.7 Gbit/s DWDM transmission

Non-fibre based in-line dispersion compensation is employed to achieve long-haul transmission of 80 channels at 10.7 Gbit/s bit rate over 1200 km of LEAF fibre. Average system margins of more than 4 dB and small transmission are demonstrated. The additional penalty incurred by the periodic nature of the dispersion compensator is assessed.     

Compensation for chromatic dispersion and nonlinear effect in highdispersive coherent optical repeater transmission system

A design for a chromatic dispersion equalizer that provides 4.4 times higher efficiency in the dispersion compensation characteristics, compared with a conventional equalizer, is proposed. In addition, the amplitude response slope in the frequency domain is less than half of the conventional characteristic. This extends the compensation limit for chromatic dispersion up to 82500 ps/nm for a 2.5-Gb/s heterodyne system, which corresponds to a 4900-km normal dispersion fiber transmission system. A compensation method for modulational instability is also proposed. The method was confirmed by a 2.5-Gb/s continuous-phase frequency-shift-keying (CPFSK) 764-km normal dispersion fiber transmission experiment, with the abovementioned chromatic dispersion equalizer. Employing computer simulations, an over-1000-km normal dispersion fiber optical repeater transmission system with 2.5-Gb/s CPFSK heterodyne detection was shown to be feasible     

40 Gbit/s CSRZ-DPSK transmission system with signed online chromatic dispersion detection

A chromatic dispersion measurement scheme based on arrival time detection, an active interferometer phase stabilisation, and a standard clock-and-data recovery circuit are used in this 40 Gbit/s carrier-suppressed return-to-zero differential phase shift keying system. Chromatic dispersion measurement noise is 100 fs/nm.     

Impact of chromatic dispersion on the system limitation due topolarization mode dispersion

The impact of chromatic dispersion on the system limitation due to polarization mode dispersion (PMD) is investigated through Monte Carlo simulations. The waveplate model is used to realistically simulate the variation of PMD with frequency. It is shown that the effects of higher order PMD are compounded in the presence of chromatic dispersion. This can lead to a reduction in the PMD limit for large values of chromatic dispersion. However, it does not lead to a reduction in the PMD limit for the moderate levels of chromatic dispersion that would be encountered in most systems     

A minimum distortion transmission scheme under combined effects of chromatic dispersion and SPM based on optical time-domain fractional Fourier transformation

In this paper, an optical time-domain fractional Fourier transformation (FRFT) system is proposed to achieve the minimum distortion transmission under combined effects of chromatic dispersion and self-phase modulation (SPM). In the new method, the pulses operated as FRFT will propagate in a new domain, in which the waveform in time domain will keep nearly unchanged through the transmission. The novel method achieves a 400 km optical transmission for an optical pulse with the full width at the 1/e point of peak power of 80 ps without any dispersion compensation and the pulse offers a nice performance with negligible nonlinear distortion. Compared with the soliton communication, this scheme shows more advantages on linear and nonlinear distortions without strict restriction to input pulses.     

Chirped picosecond injection laser pulse transmission in single-mode fibres in the minimum chromatic dispersion region

We report the propagation of chirped picosecond InGaAsP injection laser pulses in single-mode fibres in the minimum chromatic dispersion wavelength region. The observed initial compression and subsequent broadening are in good agreement with theory and illustrate the implications of chirped pulse transmission for high-bandwidth communication in the 1.2?1.6 ?m wavelength region.     

利用啁啾光纤光栅的色度色散补偿方案的研究

本文针对高速率光传输系统中的色度色散问题,利用啁啾光纤光栅,设计了后置补偿、前置补偿和混合补偿三种方案并实现了320k。的G．652光纤单信道40Gbit/s的无中继传输,仿真实验结果表明：较之后置补偿和前置补偿,混合补偿具有最好的色散补偿性能。     

Automatic chromatic dispersion compensation using alternating chirp signal for installation of high-speed transmission systems

Proposes a simple automatic chromatic dispersion compensation system that can detect the zero-dispersion point of an installed fiber span. This technique realizes high sensitivity without requiring the system to be extensively modified. The alternating chirp signal, which is used as the zero-dispersion-detection signal, has alternating optical frequency shift. It can be generated simply by changing the input signals of multiplexer circuits and shifting the bias voltage of the LiNbO/sub 3/ modulator. This technique is shown to detect the zero-dispersion point in the range of -600 to +600 ps/nm by using the signal modulated at 10 GHz; automatic dispersion compensation is successfully demonstrated in a 20-Gb/s, 400-km transmission experiment in our laboratory. Compensation is also demonstrated in 281-km-installed dispersion-shifted fiber using a 20-GHz alternating chirp signal.     

A single-mode fiber with chromatic dispersion varying along thelength

A method for fabrication of a novel type of optical fiber with dispersion varying along the fiber length is described. The method takes into account the calculated dependence of fiber dispersion on fiber core diameter for the measured profile of the preform and the desirable dispersion dependence on the fiber length. The main optical parameters of the drawn fiber are theoretically studied and experimentally measured. The fibers are of great interest for nonlinear fiber optics. Such applications of the fibers, such as high-quality soliton pulse compression, soliton pulsewidth stabilization through compensation of losses, and generation of a high-repetition-rate train of practically uninteracting solitons, are considered     

Reconstructing transmission networks using ATM and DWDM

TDM transmission and ATM switching have been established as two wide area core network technologies, operating separately but in conjunction with each other at different layers of the protocol stack. History shows that transmission networks have been reconstructed on a regular basis, and the reconstruction, based on fiber, SONET, and DWDM (dense wave division multiplexing), allows TDM transmission capabilities to be integrated with ATM switches, resulting in increased transmission efficiencies, effective bandwidth management, and greatly reduced capital, operational, and maintenance costs     

Effects of chromatic dispersion on optical coherent-detection systems

Chromatic dispersion induces to a phase-modulated optical signal a constand phase rotation that was never included in most previous studies. When the constant phase shift is removed by a phase-locked loop, the dispersion tolerance of a coherent-detection system is increased. The dispersion tolerance of phase-shift keying (PSK) signal is compared with differential PSK (DPSK) signals by numerical simulation and experimental measurement. Contrary to conventional belief, PSK signal has larger dispersion tolerance than DPSK signal.     

Electronic compensation of PMD and chromatic dispersion with an ICin 10 Gbit/s transmission system

A system experiment is reported in which polarisation mode dispersion (PMD) and chromatic dispersion (CD) compensation was achieved using an SiGe IC linear equaliser, with a transmission rate of 100 bit/s over 95 km of standard single-mode fibre (DL=1600 ps/nm). Full equalisation was obtained, with a differential group delay (DGD) of <65 ps and a penalty reduction to 3.4 dB for DGD=100 ps     

Exact compensation for both chromatic dispersion and Kerr effect ina transmission fiber using optical phase conjugation

We propose a new method to compensate exactly for both chromatic dispersion and self-phase modulation in a transmission fiber, where the light intensity changes due to fiber loss and amplifier gain. This method utilizes optical phase conjugation (OPC). The pulse shape is precompensated before OPC by transmission through a fiber with large dispersion. A computer simulation demonstrates effective compensation for waveform distortion in a 40 Gb/s NRZ intensity-modulated light transmission