Search results for "fiber"
showing 10 items of 2343 documents
Presymplectic manifolds and conservation laws
2008
In this paper we make use of a new structure called seeded fibre bundle. This allows us to combine the symplectic formalism and general relativity. A theorem of existence is obtained and some examples and properties are studied.
An all-fiber RF modulation technique: frequency response calibration of optical detectors
1995
Two all-fiber Mach-Zender interferometers have been designed to generate RF modulated light at 633 nm and 830 nm. The interferometers are scanned with a piezoelectric tube driven at its fundamental frequency of resonance. The actual experimental arrangement covers the frequency range 1 kHz to 1 GHz. The technique combines several interesting features such as the simplicity, the stability and reliability of all-fiber systems and the use of low-frequency electronics to control and generate the RF modulated light. >
Bright and dark optical solitons in fiber media with higher-order effects
2002
We consider N-coupled higher-order nonlinear Schrodinger (N-CHNLS) equations which govern the simultaneous propagation of N optical fields in fiber media with higher-order effects. Bright and dark soliton solutions are derived using Hirota bilinear method for the general cross-coupling ratio between the parameters of self-phase modulation and cross-phase modulation effects. By means of coupled amplitude-phase formulation also, similar kind of dark soliton solutions are obtained. It is found that the parametric conditions for the simultaneous propagation of N dark solitons from both the methods are the same.
AdS$_3$ solutions with exceptional supersymmetry
2018
Among the possible superalgebras that contain the AdS$_3$ isometries, two interesting possibilities are the exceptional $F(4)$ and $G(3)$. Their R-symmetry is respectively SO(7) and $G_2$, and the amount of supersymmetry ${\cal N}=8$ and ${\cal N}=7$. We find that there exist two (locally) unique solutions in type IIA supergravity that realize these superalgebras, and we provide their analytic expressions. In both cases, the internal space is obtained by a round six-sphere fibred over an interval, with an O8-plane at one end. The R-symmetry is the symmetry group of the sphere; in the $G(3)$ case, it is broken to $G_2$ by fluxes. We also find several numerical ${\cal N}=1$ solutions with $G_…
Dissipative soliton resonance as a guideline for high-energy pulse laser oscillators
2010
Dissipative soliton resonance (DSR) occurs in the close vicinity of a hypersurface in the space of parameters of the equation governing propagation in a dissipative nonlinear medium. Pulsed solutions can acquire virtually unlimited energies as soon as the equation parameters converge toward that specific hypersurface. Here we extend previous studies that have recently unveiled DSRs from the complex cubic-quintic Ginzburg-Landau equation. We clearly confirm the existence of DSR for a wide range of parameters in both regimes of chromatic dispersion, and we establish general features of the ultra-high-energy pulses that can be found close to a DSR. Application to high-energy mode-locked fiber …
Spatiotemporal Complexity in Step-Index Multimode Fibers
2016
We study supercontinuum generation in step-index fibers with a varying number of modes. We observe new spatiotemporal effects, including evidence of multimode spectral incoherent solitons, and a universal transition to spatiotemporal complexity.
Resolution-enhanced optical coherence tomography based on classical intensity interferometry.
2009
We propose a fourth-order interference scheme for optical coherence tomography operating with broadband incoherent (or quasi-incoherent) light. It is shown that using this proposal, an axial resolution improvement by a factor of 2 and a better sensitivity for weakly reflecting samples are obtained than with the standard second-order correlation scheme. From a practical perspective, we suggest the use of broadband Q-switched pulses and performing ultrafast intensity correlation with a nonlinear crystal. The global performance of our proposal is illustrated by means of numerical simulations
Observational Effects of Anomalous Boundary Layers in Relativistic Jets
2008
Recent theoretical work has pointed out that the transition layer between a jet an the medium surrounding it may be more complex than previously thought. Under physically realizable conditions, the transverse profile of the Lorentz factor in the boundary layer can be non-monotonic, displaying the absolute maximum where the flow is faster than at the jet spine, followed by an steep fall off. Likewise, the rest-mass density, reaches an absolute minimum (coincident with the maximum in Lorentz factor) and then grows until it reaches the external medium value. Such a behavior is in contrast to the standard monotonic decline of the Lorentz factor (from a maximum value at the jet central spine) an…
Angular Energy Distribution of Collapsar-Jets
2008
Collapsars are fast-spinning, massive stars, whose core collapse liberates an energy, that can be channeled in the form of ultrarelativistic jets. These jets transport the energy from the collapsed core to large distances, where it is dissipated in the form of long-duration gamma-ray bursts. In this paper we study the dynamics of ultrarelativistic jets produced in collapsars. Also we extrapolate our results to infer the angular energy distribution of the produced outflows in the afterglow phase. Our main focus is to look for global energetical properties which can be imprinted by the different structure of different progenitor stars. Thus, we employ a number of pre-supernova, stellar models…
Incoherent modulation instability in instantaneous nonlinear Kerr media
2005
We demonstrate theoretically and experimentally in an optical fiber system that partially temporally incoherent light exhibits modulational instability during its propagation in an instantaneous response nonlinear medium. We show that the modulation frequency and gain are substantially increased with respect to the corresponding values of coherent modulational instability.