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.     

Compensation of fibre chromatic dispersion in optical heterodynedetection

Compensation of fibre chromatic dispersion in coherent optical fibre transmission is demonstrated. The chromatic dispersion of a 70 km single-mode fibre with 1.3 μm zero dispersion wavelength is compensated for using a microstrip line equaliser in the intermediate frequency band. Amplitude distortion due to fibre chromatic dispersion at 1.55 μm wave-length is reduced to below 2.5 % with the equaliser     

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     

Effect of fibre dispersion on four-wave mixing in multichannel coherent optical transmission system

Severe bit error rate degradations and strong error rate floors caused by fibre four-wave mixing (FWM) in a high launch power, seven channel, coherent optical transmission system are reported. The critical influence of fibre chronic dispersion is highlighted, with a negligible penalty after transmission over conventional step index fibre, even for a launch power of +17 dBm. Several orders of FWM products are visible in the optical spectra for dispersion shifted fibre.<>     

Compensation of 202 km single-mode fibre chromatic dispersion in 4Gbit/s optical CPFSK transmission experiment

Compensation for fibre chromatic dispersion in a coherent transmission system is demonstrated. A 4 Gbit/s optical CPFSK signal at 1.55 μm is transmitted through a 202 km conventional single-mode fibre. There is 1.8 dB degradation in transmission caused by fibre chromatic dispersion. This degradation has been completely compensated for using a delay equaliser with optical heterodyne detection     

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。     

Limitations in long haul IM/DD optical fibre systems caused by chromatic dispersion and nonlinear Kerr effect

The power penalty induced by dispersion, Kerr nonlinearity and attenuation is numerically investigated for long haul IM/DD systems with cascaded optical amplifiers. The authors demonstrate that the eye opening is critically dependant on the input mean power.<>     

Measurement of nonlinear and chromatic dispersion parameters of optical fibers using modulation instability

We present a simple method for the measurement of Kerr, second- and third-order dispersion coefficients in optical fibers using power and dispersion dependences of modulation instability near the zero-dispersion wavelength. We also complete the analysis by the accurate determination of the zero-dispersion wavelength of the fiber using the phase-matched four wave mixing process which occurs near this specific wavelength.     

Comparison of optical millimetre-wave system concepts with regardto chromatic dispersion

The author reports the impact of chromatic dispersion in optical millimetre-wave systems operating in the 1.55 μm wavelength window. Experimental and theoretical results confirm the dramatical millimetre-power degradation in conventional amplitude modulated systems using for example, external optical modulators. In comparison, by use of a similar setup a self-heterodyne-based system concept has been investigated showing negligible dependence on the chromatic dispersion     

Subband equaliser for chromatic dispersion of optical fibre

An oversampled subband equaliser is designed for chromatic dispersion of singlemode optical fibre. The signal of each subband is equalised individually and delayed to align with other subbands. From simulation, the overall number of equaliser taps is approximately reduced by the upsampling ratio.     

相干光纤电视传输实验系统

一种新型的相干光纤通信实验系统最近在桂林激光通信研究所完成。该系统用于传输彩色电视信号,其接收灵敏度述-56dBm,比目前的直接探测光纤彩电传输系统的接收灵敏度提高了近14dB。     

Techniques for multigigabit coherent optical transmission

It has been anticipated that the main roles for coherent optical techniques will be to provide increased capacity both for long-haul transmission and wide-band signal distribution. This could be achieved by the combination of high-data-rate transmission and fine-grain WDM. To this end, heterodyne detection experiments have recently been extended into the gigabit regime but difficulties not present at lower data rates have been encountered. This paper discusses a range of technical solutions to these problems, including broad-band receivers, homodyne detection, and phase diversity reception, and reviews their current status.     

5 Gbit/s optical transmission system experiment employing laser amplifier repeater

The performance of a packaged semiconductor laser amplifier has been investigated for use in an optical transmission system at 5 Gbit/s. With optical filtering at the receiver input only small system penalties were found, as expected from the analysis of the dominant noise contributions.<>     

Experimental demonstration of the maximum likelihood-based chromatic dispersion estimator for coherent receivers

We perform an experimental investigation of a maximum likelihood-based (ML-based) algorithm for bulk chromatic dispersion estimation for digital coherent receivers operating in uncompensated optical networks. We demonstrate the robustness of the method at low optical signal-to-noise ratio (OSNR) and against differential group delay (DGD) in an experiment involving 112 Gbit/s polarization-division multiplexed (PDM) 16-ary quadrature amplitude modulation (16 QAM) and quaternary phase-shift keying (QPSK).     

Ten-channel coherent optical fibre transmission

A laboratory ten-channel coherent fibre-optic broadband transmission system is reported. The frequency-division-multiplexed optical carriers are separated by 6 GHz and are demultiplexed by a tunable heterodyne receiver having a sensitivity of -46 dBm at a bit error rate of 10-9. In this system a maximum number of 64 channels can be installed.     

Improved all optical chromatic dispersion monitoring method for WDM systems

In this paper we propose an improved all optical chromatic dispersion (CD) monitoring method applicable to wavelength division multiplexing (WDM) systems with intensity or phase modulation format. This method can operate over a much larger bandwidth and CD monitoring range and is insensitive to optical signal-to-noise ratio (OSNR) and polarization mode dispersion (PMD). These improvements are achieved by utilizing a wavelength tunable laser as the probe to maintain the appropriate phase-matching condition and a loop-back controlled tunable CD compensator to discriminate CD distortions from PMD and OSNR influences. Numerical simulations show that by this method the operational bandwidth and CD monitoring range can be expanded to cover C + L bands and ±1600 ps/nm, respectively, for different modulation formats and the sensitivity is higher than the other methods proposed before.     

高速光纤传输系统的色散管理分析

对NRZ、RZ和CS-RZ码等三种码型在高速准线性传输系统中的性能进行了分析。通过对设计出相应色散管理方案的仿真,对其色散容限、抗非线性效应、抗噪声和抗偏振模色散性能进行对比分析。根据系统设计CS-RZ码的预色散补偿、后色散补偿和对称色散补偿等三种色散管理方案,并对三种方案的最大Q值进行残余色散优化,为现实系统的设计提供参考价值。     

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.     

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.