- 标题
- 摘要
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- 实验方案
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DSP-free and Real-Time NRZ transmission of 50 Gb/s over 15 km SSMF and 64 Gb/s back-to-back with a 1.3 μm VCSEL
摘要： We demonstrate and analyze 50 Gb/s non-return-to-zero (NRZ) transmission over 15 km of standard single-mode fiber (SSMF), 60 Gb/s NRZ transmission over 5 km of SSMF and up to 64 Gb/s NRZ back-to-back using a directly modulated short-cavity long-wavelength single-mode VCSEL emitting at 1326 nm. Owing to an analog 6-tap transmit feedforward equalizer, the link can operate without digital signal processing. In all three cases, real-time bit error ratio measurements below the 7% overhead hard-decision forward error correction (FEC) threshold are demonstrated when transmitting a pseudo-random bit sequence (PRBS) with a period of 27-1 bits. In addition, we analyze the interplay between the residual fiber chromatic dispersion at the operating wavelength of the VCSEL and the chirp due to direct modulation. These results demonstrate how O-band, short-cavity long-wavelength single-mode VCSELs can be used in intra data center networks, as well as inter data center networks at reaches below 15 km.
关键词： Fiber Optics Communications,Optical Interconnections,Vertical Cavity Surface Emitting Lasers,BiCMOS integrated circuits,Chirp,Analog Equalization
更新于2025-09-09 09:28:46
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Sampling Rules for an Inhomogeneous Plane-wave Representation of Scattered Fields
摘要： Inhomogeneous plane waves (IPW) based on a linear contour deformation provide an accurate and concise field representation for scattering problems in which source and observation domains are visible within a limited angular sector. Given an error level, we derive closed-form expressions for the truncation limit, the sampling step and the contour slope that minimize the number of plane waves. A relation is drawn between the required number of plane waves and the degrees of freedom of the field, defined as the minimum number of orthonormal basis functions that represents scattered fields. The sampling rules are then applied to an efficient evaluation of the physical optics radiation integral.
关键词： Computational electromagnetics,spectral domain method,contour deformation,physical optics,error analysis,fast algorithm,degrees of freedom,field representation,Green’s function,scattering,inhomogeneous plane waves
更新于2025-09-09 09:28:46
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Optical concentrator from a hyperbolic liquid-crystal metamaterial
摘要： We examine the optical properties of two different configurations of a cylindrical device made from a hyperbolic metamaterial with optical axis defined by circular and radial director fields. The hyperbolic metamaterial is a uniaxial anisotropic medium for which the ratio between ordinary and extraordinary permittivities is negative, leading to a particular effective geometry with two timelike coordinates in the metric (Kleinian signature). By using differential geometry tools we are able to perform a comparison between a simple geometrical optics treatment and the wave formalism that shows the concentration of light along the cylinder axis for the case of the circular field configuration, whatever the injection conditions are.
关键词： optical concentrator,geometrical optics,wave formalism,light concentration,hyperbolic liquid-crystal metamaterial
更新于2025-09-09 09:28:46
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Study of Polymorphism of Borovanadate Glass of Sodium by Raman Spectroscopy Low Frequencies
摘要： Sodium tetraborate (100 – x)(Na2B4O7.10H2O) – xV2O5, (x = 0 to 20 mole %) has been elaborated by splat cooling technique. Raman Measurements on the doped and non polish samples reveal the presence of the of α-NaVO3 crystal on the superficial layer. After polishing, Raman spectra characteristic of glasses are obtained with two main bands located at 555 and 1097 cm-1 in the undoped glass and four bands at 241, 381, 776 and 938 cm-1 for the vanadium oxyde doped glasses. The volume devitrification of these glasses occurs at 750° C and the β-NaVO3 crystalline phase is identified by Raman scattering.
关键词： Non-linear optics,Oxide glasses,XRD,Raman scattering,DSC
更新于2025-09-09 09:28:46
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Contents: (Adv. Funct. Mater. 48/2018)
摘要： New organic three-component single crystals exhibiting large macroscopic optical nonlinearity, excellent optical quality, and efficient optical-to-THz conversion are developed using so-called 'pseudo-isomorphic cocrystallization' for nonlinear optical and THz photonic applications.
关键词： THz photonics,pseudo-isomorphic cocrystallization,organic single crystals,nonlinear optics
更新于2025-09-09 09:28:46
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Ultrashort pulse reconstruction using a deterministic phase retrieval method with Gaussian-envelope gates
摘要： A novel scheme of ultrashort pulse characterization is proposed that is capable of reconstructing the complex-valued envelope of a pulse in the time domain by use of a second harmonic generation system with two Gaussian gate pulses. In this scheme, we apply an analytic (noniterative) phase-retrieval method for coherent diffractive imaging in the space domain to the pulse characterization, and so the spectral phase of an unknown pulse can be retrieved from only two spectra of the unknown pulse modulated with a Gaussian gate and its time-shifted Gaussian one. Computer-simulated examples demonstrate that the pulse retrieval is robust. In particular, it is shown that the reconstruction of an unknown pulse using approximate Gaussian gates derived from replicas of the pulse itself is also effective, provided the spectrum of the unknown pulse has a gentle slope within the spectral bandwidth of the gate pulse.
关键词： Ultrafast measurements,Pulse characterization,Phase retrieval,Ultrafast optics
更新于2025-09-09 09:28:46
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Effect of Faraday mirror imperfections in a fiber optic current sensor dedicated to ITER
摘要： Plasma current measurements in ITER are safety-related and must therefore satisfy a very demanding specification. In this paper, the use of the Fiber Optics Current Sensor (FOCS) operating in the reflection mode with a Faraday mirror to perform plasma current measurements is analyzed. Based on the Jones matrix formalism, we performed numerical simulations to investigate the impact of the Faraday mirror detuning on the measurement accuracy. We show that the use of standard commercial components does not allow to satisfy the ITER requirements for the whole plasma current range. A simple solution to the problem is proposed, which consists in taking into account a mirror calibration in the current estimator. We show that the achievable mirror calibration accuracy is sufficient to fulfill the ITER requirements.
关键词： Polarimetric sensors,Plasma diagnosis,Fiber optics current sensors
更新于2025-09-09 09:28:46
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An optimization model for robust FSO network dimensioning
摘要： FSO (Free Space Optics) is a well established wireless optical transmission technology considered as an alternative to radio communications, for example in metropolitan wireless mesh networks. An FSO link is established by means of a laser beam connecting the transmitter and the receiver placed in the line of sight. A major disadvantage of FSO links (with respect to fiber links) is their sensitivity to weather conditions such as fog, rain and snow, causing substantial loss of the transmission power over the optical channel due mostly to absorption and scattering. Thus, although the FSO technology allows for fast and low-cost deployment of broadband networks, its operation will be affected by this sensitivity, manifested by substantial losses in links’ transmission capacity with respect to the nominal capacity. Therefore, a proper approach to FSO network dimensioning should take such losses into account so that the level of carried traffic is satisfactory under all observed weather conditions. In the paper we describe such an approach. We introduce a relevant dimensioning problem and present a robust optimization algorithm for such enhanced dimensioning. A substantial part of the paper is devoted to present a numerical study of two FSO network instances that illustrates the promising effectiveness of the proposed approach.
关键词： Free space optics,Multicommodity flows,Linear and mixed-integer programming,Robust optimization,Resilient and survivable networks,Variable link capacity
更新于2025-09-09 09:28:46
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Super-resolution enhancement by quantum image scanning microscopy
摘要： The principles of quantum optics have yielded a plethora of ideas to surpass the classical limitations of sensitivity and resolution in optical microscopy. While some ideas have been applied in proof-of-principle experiments, imaging a biological sample has remained challenging, mainly due to the inherently weak signal measured and the fragility of quantum states of light. In principle, however, these quantum protocols can add new information without sacrificing the classical information and can therefore enhance the capabilities of existing super-resolution techniques. Image scanning microscopy, a recent addition to the family of super-resolution methods, generates a robust resolution enhancement without reducing the signal level. Here, we introduce quantum image scanning microscopy: combining image scanning microscopy with the measurement of quantum photon correlation allows increasing the resolution of image scanning microscopy up to twofold, four times beyond the diffraction limit. We introduce the Q-ISM principle and obtain super-resolved optical images of a biological sample stained with fluorescent quantum dots using photon antibunching, a quantum effect, as a resolution-enhancing contrast mechanism.
关键词： image scanning microscopy,quantum dots,quantum optics,super-resolution microscopy,photon antibunching
更新于2025-09-09 09:28:46
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The photonic candle
摘要： Using light to manipulate small particles has proven an indispensable tool for ‘tweezing’, sorting and force measurements. To achieve effective optical traps with high ‘stiffness’, researchers often go to great lengths to tailor light fields, for example by using holographic elements. Now, Aliaksandra Ivinskaya and colleagues from Russia, the USA, the UK and Israel predict that small particles can be manipulated using a plane wave of light and a simple flat surface of an anisotropic media supporting hyperbolic modes. Their hyperbolic metamaterial is composed of metal and dielectric layers and is potentially less affected by losses and offers more broadband capability than purely plasmonic approaches. In their theoretical study a small dielectric sphere near a hyperbolic metamaterial is considered. The particle is sufficiently small to provide the required momentum to excite both surface plasmon and bulk hyperbolic waves from incident plane waves. Strong optical pulling forces were predicted over the 400–800 nm wavelength range thanks to the broadband high density of states of hyperbolic modes.
关键词： hyperbolic modes,nano-optics,optical manipulation,metasurface,plasmon
更新于2025-09-09 09:28:46