Model for optical forward scattering by nonspherical raindrops

We describe a numerical model for the interaction of light with large raindrops using realistic nonspherical drop shapes. We apply geometrical optics and a Monte Carlo technique to perform ray traces through the drops. We solve the problem of diffraction independently by approximating the drops with areaequivalent ellipsoids. Scattering patterns are obtained for different polarizations of the incident light. They exhibit varying degrees of asymmetry and depolarization that can be linked to the distortion and thus the size of the drops. The model is extended to give a simplified long-path integration.Comment: 12 pages, 16 figure

Nonlinear Schr\"odinger Equation with a White-Noise Potential: Phase-space Approach to Spread and Singularity

We propose a phase-space formulation for the nonlinear Schr\"odinger equation with a white-noise potential in order to shed light on two issues: the rate of spread and the singularity formation in the average sense. Our main tools are the energy law and the variance identity. The method is completely elementary. For the problem of wave spread, we show that the ensemble-averaged dispersion in the critical or defocusing case follows the cubic-in-time law while in the supercritical and subcritical focusing cases the cubic law becomes an upper and lower bounds respectively. We have also found that in the critical and supercritical focusing cases the presence of a white-noise random potential results in different conditions for singularity-with-positive-probability from the homogeneous case but does not prevent singularity formation. We show that in the supercritical focusing case the ensemble-averaged self-interaction energy and the momentum variance can exceed any fixed level in a finite time with positive probability

Transmission of optical communication signals by distributed parametric amplification

We have demonstrated, for the first time to our knowledge, distributed parametric amplification, i.e. amplification of 10-Gb/s communication signals along a 75-km transmission fiber by using a co-propagating pump with only 66.5 mW of power.published_or_final_versio

Recent advances in the design and implementation of practical fiber optical parametric amplifiers

Conference on Optoelectronic and Microelectronic Materials and Devices, Brisbane, Australia, 8-10 December 2004Fiber optical parametric amplifiers (OPAs) are based on the third-order nonlinear susceptibility of glass fibers. If two strong pumps and a weak signal are fed into a fiber, an idler is generated. Signal and idler can grow together if pump power is high enough, and phase matching occurs. In recent years, impressive performance has been demonstrated in several respects: 1) Gain in excess of 60 dB has been obtained; 2) fiber OPAs can exhibit a large variety of gain spectra: a gain bandwidth of 400 nm has been demonstrated; tunable narrowband gain regions can also be generated; 3) Noise figure of 3.7 dB, limited by other third-order nonlinear process; 4) Polarization-insensitive operation in both one-pump and two-pump configurations; 5) The presence of the idler can be used for wavelength conversion. Also, the spectrum of the idler is inverted with respect to that of the signal; thus by placing an OPA in the middle of a fiber span one can realize mid-span spectral inversion (MSSI) which counteracts the effect of fiber dispersion and some nonlinear effects. Besides using fiber OPA in continuous-wave regime as in typical systems, pulsed-pump has also been demonstrated to achieve larger bandwidth and higher peak gain by combining with optical filtering technique. Furthermore, by modulating the pump it is possible to modulate signal and/or idler at the output. This can be used to implement a variety of signal processing functions, including: fast signal switching; demultiplexing of time-division-multiplexed signals; retiming and reshaping of waveforms; optical sampling. A number of challenges must be overcome in order for fiber OPAs to be useful in communication applications. In multi-wavelength systems, these are: four-wave mixing, cross-phase modulation; and cross-gain modulation between signals. Furthermore, the pump-to-signal relative intensity noise (RIN) transfer and frequency/phase modulation (FM/PM) to signal intensity conversion are also potential challenges for practical fiber OPAs. © 2005 IEEE.published_or_final_versio

Possible approach to improve sensitivity of a Michelson interferometer

We propose a possible approach to achieve an 1/N sensitivity of Michelson interferometer by using a properly designed random phase modulation. Different from other approaches, the sensitivity improvement does not depend on increasing optical powers or utilizing the quantum properties of light. Moreover the requirements for optical losses and the quantum efficiencies of photodetection systems might be lower than the quantum approaches and the sensitivity improvement is frequency independent in all detection band.Comment: 8 pages, 3 figures, new versio

Pump-to-signal transfer of low-frequency intensity modulation in fiber optical parametric amplifiers

This paper describes the theoretical and experimental investigation of the transfer of low-frequency intensity modulation (IM) from pump to signal in fiber optical parametric amplifiers (OPAs). It is first established that low-frequency IM of the pump remains unchanged over the length of the amplifier in spite of the presence of parametric gain. The pump-power dependence of the OPA gain is then used to calculate the instantaneous effect of pump IM on the signal and idler output powers. These calculations are performed for both one- and two-pump OPAs. The main predictions are that 1) the ratio ρ of the signal intensity modulation depth to that of the pump varies across the OPA gain spectrum and 2) for a 20-dB gain, ρ can exceed 10 at some wavelengths, which indicates that this effect can be detrimental. Experiments have been performed to verify these predictions. Using sinusoidal IM of the pump, the resulting amplified signal IM was measured, and the experimental results were found to be in good agreement with the theoretical predictions. © 2005 IEEE.published_or_final_versio

Architekturnaja metafora u Mandel´štama

RéSUMéLe rapprochement métaphorique de la poésie et de l’architecture chez Osip Mandel´Òtam. Dans ses écrits poétiques et théoriques, Mandel´Òtam établit une analogie entre la poésie et l’architecture, plaçant ainsi son œuvre dans un contexte philosophique et esthétique différent de celui qu’exploraient les symbolistes russes. Il y développa l’idée que la beauté naît de la téléologie et qu’on en trouve le meilleur exemple dans l’architecture, en particulier celle des cathédrales gothiques. L’idée que la beauté est l’effet de la téléologie implique généralement un rapport entre le beau et le bien, et le glissement de Mandel´Òtam vers cette esthétique fut guidé par la philosophie du Bien de Solov´ev. La conception de ce dernier se trouve paraphrasée dans « Notre Dame », le poème le plus connu de Mandel´Òtam, qui est aussi une sorte de manifeste artistique. Ce sont les traités de rhétorique de l’Antiquité qui utilisèrent les premiers les métaphores architecturales dans le but d’introduire le rapport entre la beauté et le téléologique dans la théorie littéraire. Il est plus vraisemblable que Mandel´Òtam puisait son inspiration dans la rhétorique de l’Antiquité et non dans les édifices eux-mêmes quand il décrivait les voûtes gothiques et les dômes byzantins ou de la Renaissance. On retrouve dans l’un de ses poèmes des termes utilisés par Demetrius dans une comparaison entre une figure de rhétorique et une voûte ou un dôme. Le poète accordait sans doute une importance hors du commun au dôme de Saint-Pierre parce que Diderot en avait fait un exemple de l’identification de la beauté au téléologique dans son étude brillante, Essai sur la peinture. Mandel´Òtam, qui avait une prédilection pour le Siècle des lumières, fait allusion à l’ Essai de Diderot dans le poème intitulé « L’Amirauté ».ABSTRACTOsip Mandel´shtam’s architectural metaphor of poetry. Mandel´shtam’s use of an analogy between poetry and architecture in his poems and theoretical writings placed his poetry in a specific philosophical and aesthetical context different from that explored by Russian Symbolists. Throughout his oeuvre, he developed the idea that beauty originates in purposiveness, the best example of which, to him, could be found in architectural structures, first and foremost Gothic cathedrals. The concept that beauty is the effect of purposiveness usually includes a connection between the beautiful and the good, and Mandel´shtam’s shift to this kind of aesthetics was guided, in its turn, by V. Solov´ev’s philosophy of the Good. Solov´ev’s conception of art is paraphrased in “Notre Dame,” Mandel´shtam’s most famous poem and a poetic manifesto of sorts. It was the classical treatises on rhetorics that first used architectural metaphors in order to introduce the purposive idea of beauty into literary theory. It is likely that it was not the architectural structures themselves, but the classical theories of speech that influenced Mandel´shtam’s view of poetry and inspired him to describe the structure of Gothic vaults and Byzantine or Renaissance domes in his writings. One of his poems uses Demetrius’ terms in a comparison of a rhetorical period with a vault or dome. The poet may have given the dome of St. Peter exceptional significance because its structure had already been brilliantly interpreted by Diderot in his Notes on Painting as exemplifying the identification of beauty with purposiveness. Mandel´shtam, who had a predilection for the Enlightenment, implicitly refers to Diderot’s discussion of beauty in the poem “The Admiralty.

Quasi-passive optical infrastructure for future 5G wireless networks: pros and cons

In this paper, we study the applicability of the quasi-passive reconfigurable (QPAR) device, a special type of quasi-passive wavelength-selective switch with flexible power allocation properties and no power consumption in the steady state, to implement the concept of reconfigurable backhaul for 5G wireless networks. We first discuss the functionality of the QPAR node and its discrete component implementation, scalability, and performance. We present a novel multi-input QPAR structure and the pseudo-passive reconfigurable (PPAR) node, a device with the functionality of QPAR but that is pseudo-passive during steady-state operations. We then propose mesh and hierarchical back-haul network architectures for 5G based on the QPAR and PPAR nodes and discuss potential use cases. We compare the performance of a QPAR-based single-node architecture with state-of-the-art devices. We find that a QPAR node in a hierarchical network can reduce the average latency while extending the reach and quality of service of the network. However, due to the high insertion losses of the current QPAR design, some of these benefits are lost in practice. On the other hand, the PPAR node can realize the benefits practically and is the more energy-efficient solution for high reconfiguration frequencies, but the remote optical node will no longer be passive. In this paper, we discuss the potential benefits and issues with utilizing a QPAR in the optical infrastructure for 5G networks.This work has been funded by the Spanish project TIGRE5 CM (grant number S2013/ICE 2919), the EU H2020 5G Crosshaul project (grant number 671598), and the Australian Research Council’s Discovery Early Career Researcher Award (DECRA) funding scheme (project number DE150100924). The authors would also like to acknowledge the support of the Center for Integrated Systems, Stanford University, and Corning Incorporated. for the development of this work

Quasi-passive and reconfigurable optical node: implementations with discrete latching switches

Quasi-Passive and Reconfigurable (QPAR) optical nodes are implemented using two different discrete optical latching switches based on Micro-Opto-Mechanical and Magneto-Optic principles. A clear trade-off between speed and power consumption is noticed for those QPAR realizations