Driven by an ever-increasing number of new services and applications, transport networks have been undergoing significant changes. In this paper, we describe several exciting technology directions associated with future optical transport networks. We review the status of 100G, which is now commercially available and entering volume deployments, and its applications in China. Beyond 100G is considered as the primary technology for the expansion of both channel and fiber capacity in the near term, and several enabling techniques are introduced. Then, key technologies, products, and future evolutionary options of Optical Transport Networks (OTNs) are extensively discussed. Compared to fixed bandwidth and coarse granularity of current WDM network, a flexible grid architecture is a desirable evolution trend, and key technologies and challenges are described. Finally, we illustrate the multi-dimension convergences in terms of IP and optical, Packet OTN (P-OTN), as well as Electronic Integrated Circuits (EICs) and Photonic Integrated Circuits (PICs). Transport networks are therefore in the process of becoming more broadband, robust, flexible, cost-effective and lower-power-consumptive.
We propose a joint nonlinear electrical equalization approach in coherent optical discrete-Fourier-transform spread orthogonal-frequency-division-multiplexing(DFT-spread-OFDM) systems with polarization division multiplexing(PDM).This method is based on an adaptive Volterra series expansion for nonlinear distortions of two orthogonal polarizations.The nonlinear electrical equalization is validated through numerical simulation of 100-Gb/s quadrature phase shift keying and 200-Gb/s 16 quadrature amplitude modulation PDM DFT-spread-OFDM systems.
Fiber nonlinearity is one of the most important limiters of capacity in coherent optical communications. In this paper, we review two nonlinear compensation methods: digital backward propagation (BP) and nonlinear electrical equalizer (NLEE) based on the time-domain Volterra series. These compensation algorithms are implemented in a single-channel 50 Gb/s coherent optical single-carrier frequency-division multiplexed (CO-SCFDM) system transmitting over 10 × 80 km of standard single-mode fiber (SSMF).
Fan Zhang (State Key Laboratory of Advanced Optical Communication Systems & Networks, Peking University, Beijing 100871, P.R.China)
In recent years,much attention has been given to the increase in the Earth-Sun distance,with the modern rate reported as 5-15 m/cy on the basis of astronomical measurements.However,traditional methods cannot measure the ancient leaving rates,so a myriad of research attempting to provide explanations were met with unmatched magnitudes.In this paper we consider that the growth patterns on fossils could reflect the ancient Earth-Sun relationships.Through mechanical analysis of both the Earth-Sun and Earth-Moon systems,these patterns confirmed an increase in the Earth-Sun distance.With a large number of well-preserved specimens and new technology available,both the modern and ancient leaving rates could be measured with high precision,and it was found that the Earth has been leaving the Sun over the past 0.53 billion years.The Earth's semi-major axis was 146 million kilometers at the beginning of the Phanerozoic Eon,equating to 97.6% of its current value.Measured modern leaving rates are 5-14 m/cy,whereas the ancient rates were much higher.Experimental results indicate a special expansion with an average expansion coefficient of 0.57H0 and deceleration in the form of Hubble drag.On the basis of experimental results,the Earth's semi-major axis could be represented by a simple formula that matches fossil measurements.
ZHANG WeiJia1,3,4,LI ZhengBin2,3 & LEI Yang1 1 Department of Physics,Peking University,Beijing 100871,China
We experimentally investigate multigranularity optical subband switching functionality between two superchannels with slight error vector magnitude penalty. One is 4×39 Gb/s polarization-division-multiplexed(PDM) quadrature phase shift keying discrete Fourier transform spread orthogonal frequency division multiplexing(DFT-spread-OFDM) superchannel with 12.5 GHz band spacing. The other is 8×29 Gb/s PDM-16-quadrature amplitude modulation Nyquist pulse shaping superchannel with 6.25 GHz band spacing. To the best of our knowledge, this is the first time that optical switching functionality for individual band between different superchannels with multigranularity is realized.
Enhancing resonance frequency of strong optical injection-locked semiconductor lasers is experimentally studied.Resonance frequency is increased from 4.1 to 53.9 GHz by the optical injection locking(OIL)technique.We experimentally demonstrate that resonance frequency is strictly equal to the frequency spacing between the cavity modes of the master and slave lasers under strong OIL condition.This result provides valuable information to improve OIL theory.
