Scalability of Optical Networks: Crosstalk Limitations

Optical networks represent a promising solution for the future high capacity and flexible transport network. This paper presents a model for the performance evaluation of optical networks with respect to linear crosstalk and accumulated spontaneous emission noise. The proposed model is intended for the evaluation of the crosstalk requirements on the devices needed to support an optical network with a certain number of nodes and with a given level of bit-error rate.     

Covering arrays of strength three from extended permutation vectors

A covering array \(\text{ CA }(N;t,k,v)\) is an \(N\times k\) array such that in every \(N\times t\) subarray each possible t-tuple over a v-set appears as a row of the subarray at least once. The integers t and v are respectively the strength and the order of the covering array. Let v be a prime power and let \({\mathbb {F}}_v\) denote the finite field with v elements. In this work the original concept of permutation vectors generated by a \((t-1)\)-tuple over \({\mathbb {F}}_v\) is extended to vectors generated by a t-tuple over \({\mathbb {F}}_v\). We call these last vectors extended permutation vectors (EPVs). For every prime power v, a covering perfect hash family \(\text{ CPHF }(2;v^2-v+3,v^3,3)\) is constructed from EPVs given by subintervals of a linear feedback shift register sequence over \({\mathbb {F}}_v\). When \(v\in \{7,9,11,13,16,17,19,23,25\}\) the covering array \(\text{ CA }(2v^3-v;3,v^2-v+3,v)\) generated by \(\text{ CPHF }(2;v^2-v+3,v^3,3)\) has less rows than the best-known covering array with strength three, \(v^2-v+3\) columns, and order v. CPHFs formed by EPVs are also constructed using simulated annealing; in this case the results improve the size of eighteen covering arrays of strength three.     

电环形谐振腔表面几何参数对太赫兹超材料吸收体性能的影响

本文分析了电环形谐振腔的几何参数对超材料吸收体吸收率的影响。文中详细分析了电环形谐振腔参数、介电层（间隔物）厚度和电环形谐振腔厚度对超材料吸收体的影响,在此基础上,设置正交实验分析了几种参数的综合影响,最终获得超材料的理论吸收率。根据上述结果,制备了2个超材料吸收体的原理样机,经实验测得,原理样机的窄带吸收率高于98%。本文的研究成果为高性能吸收器的设计提供了指导。     

Regenerative all-optical wavelength multicast for next generation WDM network and system applications

We experimentally demonstrate regenerative all-optical wavelength multicast by simultaneous multi-wavelength conversion of 10 Gb/s non-return-to-zero signals to four ITU 100 GHz spaced channels with a receiver sensitivity improvement of 1.84 dB and less than 0.14 dB difference among all the multicast channels, using a single commercial monolithically integrated SOA-MZI. The multicast device also exhibited about 22 dB optical signal-to-noise ratio enhancement for all the converted channels compared to the original signal channel without wavelength conversion. Our experiment for the first time revealed the regeneration properties of a SOA-MZI device for WDM wavelength multicast purposes, and proved the excellent performance of a simple scheme for various future network and system applications, such as all-optical wavelength routing and grid networking.     

Distribution of photonically generated 5 Gbits/s impulse radio ultrawideband signals over fiber

We propose an approach to generate ultrawideband (UWB) pulses with tunable high-speed modulation based on pulse compression. Flexible generation of up to a record 5?Gbits/s on-off keying impulse radio UWB signals are successfully demonstrated as well. We also investigate 5?Gbits/s on-off keying bit-error-rate (BER) performance after 40?km single mode fiber transmission by employing a digital signal processing receiver, and the BER below forward error correction limit is achieved.     

Applicability of hybrid density functional theory methods to calculation of molecular hyperpolarizability

The donor/acceptor (D/A) substituted pi-conjugated organic molecules possess extremely fast nonlinear optical (NLO) response time that is purely electronic in origin. This makes them promising candidates for optoelectronic applications. In the present study, we utilized four hybrid density functionals (B3LYP, B97-2, PBE0, BMK), Hartree-Fock, and second order Moller-Plesset correlation energy correction, truncated at second-order (MP2) methods with different basis sets to estimate molecular first hyperpolarizability (beta) of D/A-substituted benzenes and stilbenes (D=OMe, OH, NMe(2), NH(2); A=NO(2), CN). The results of density functional theory (DFT) calculations are compared to those of MP2 method and to the experimental data. We addressed the following questions: (1) the accurate techniques to compare calculated results to each other and to experiment, (2) the choice of the basis set, (3) the effect of molecular planarity, and (4) the choice of the method. Comparison of the absolute values of hyperpolarizabilities obtained computationally and experimentally is complicated by the ambiguities in conventions and reference values used by different experimental groups. A much more tangible way is to compare the ratios of beta's for two (or more) given molecules of interest that were calculated at the same level of theory and measured at the same laboratory using the same conventions and reference values. Coincidentally, it is the relative hyperpolarizabilities rather than absolute ones that are of importance in the rational molecular design of effective NLO materials. This design includes prediction of the most promising candidates from particular homologous series, which are to be synthesized and used for further investigation. In order to accomplish this goal, semiquantitative level of accuracy is usually sufficient. Augmentation of the basis set with polarization and diffuse functions changes beta by 20%; however, further extension of the basis set does not have significant effect. Thus, we recommend 6-31+G(*) basis set. We also show that the use of planar geometry constraints for the molecules, which can somewhat deviate from planarity in the gas phase, leads to sufficient accuracy (with an error less than 10%) of predicted values. For all the molecules studied, MP2 values are in better agreement with experiment, while DFT hybrid methods overestimate beta values. BMK functional gives the best agreement with experiment, with systematic overestimation close to the factor of 1.4. We propose to use the scaled BMK results for prediction of molecular hyperpolarizability at semiquantitative level of accuracy.     

Experimental Investigation of Transmission Properties and All-Optical Label Swapping of Orthogonal IM/FSK Labeled Signals

Optically labeled IM/FSK signal saretran smitte dover 50km of SMF under different compensation schemes.All-opticallabel swapping based on MZ-SOA and EAM is presented. Transmission followed by label swapping shows a 2dB overall power penalty.     

Pulse shaping for high data rate ultra‐wideband wireless transmission under the Russian spectral emission mask

This paper addresses impulse‐radio ultra‐wideband (IR‐UWB) transmission under the Russian spectral emission mask for unlicensed UWB radio communications. Four pulse shapes are proposed and their bit error rate (BER) performance is both estimated analytically and evaluated experimentally. Well‐known shapes such as the Gaussian, root‐raised cosine, hyperbolic secant, and the frequency B‐spline wavelet are used to form linear combinations of component pulses, shaped to make efficient use of the spectral emission mask. Analytical BER values are derived using a Nakagami‐m model, and good agreement is found with the experimentally obtained BER. The proposed pulse shapes allow IR‐UWB transmission with BERs below the limit for a 7% overhead forward error correction, achieving distances of up to 6.5 m at 1 Gbit/s, 4.5 m at 1.25 Gbit/s, and 1 m at  Gbit/s. These results confirm the viability of IR‐UWB transmission under the strict regulations of the Russian spectral emission mask.     

Recognition of spectral amplitude codes by frequency swept coherent detection for flexible optical label switching

We propose a new method of recognizing spectral amplitude codes by using optical coherent detection with a frequency swept local light source oscillator. Our proposed method offer a substantial simplification in terms of required components to built optical label processing units with enhanced flexibility to accommodate for wavelength tuneability and a large number of labels. We present a performance analysis, comparison with conventional spectral codes recognition methods, based on computer simulation results. We consider a payload bit rate of 40 Gb/s.     

In-House Networks Using Multimode Polymer Optical Fiber for Broadband Wireless Services

A novel system concept is presented to transport microwave signals over an in-house multimode graded-index polymer optical fiber network, in order to feed the radio access points in high-capacity wireless LANs. By employing optical frequency multiplying, the network's intrinsically limited bandwidth is overcome. The feasibility of this concept to carry data at several hundreds of Mbit/s speed for various microwave signal formats at carrier frequencies in the tens of GHz range is shown. The concept enables cost-effective system implementation, and easy upgrading by offering data signal transparency. It can readily be integrated with other system technologies such as wired Gigabit Ethernet in a single multi-service in-house polymer optical fiber network.