Search results for "Wavelength"
showing 10 items of 741 documents
Radiation resistance and optical properties of lead fluoride Cherenkov crystals
1998
Abstract Optical properties of large size lead fluoride (PbF 2 ) crystals of three different manufacturers and their degradation caused by 60 Co γ-radiation have been investigated. Transmission losses have been systematically studied at absorbed energy doses between 0.1 and 7 kGy. Several radiation induced absorption bands have been observed. Optical bleaching with light of wavelengths ≳365 nm has been found very effective to restore the original characteristics even after repeated irradiations. This observation together with the high density and the ultraviolet extended transmission make PbF 2 an excellent choice for high rate and high resolution e.m. calorimetry.
A decade of SN 1993J : discovery of radio wavelength effects in the expansion rate
2009
We studied the growth of the shell-like radio structure of supernova SN 1993J in M 81 from September 1993 to October 2003 with very-long-baseline interferometry (VLBI) observations at the wavelengths of 3.6, 6, and 18 cm. We developed a method to accurately determine the outer radius (R) of any circularly symmetric compact radio structure such as SN 1993J. The source structure of SN 1993J remains circularly symmetric (with deviations from circularity under 2%) over almost 4000 days. We characterize the decelerated expansion of SN 1993J until approximately day 1500 after explosion with an expansion parameter m = 0.845 ± 0.005 (R ∝ tm). However, from that day onwards the expansion differs whe…
Observation of modulational instability induced by velocity-matched cross-phase modulation in a normally dispersive bimodal fiber
2008
We demonstrate experimentally the existence of cross-phase-modulation-induced modulational instability in the absence of group-velocity mismatch between the interacting nonlinear dispersive waves. The experiment is performed by means of a normally dispersive isotropic bimodal fiber. The group-velocity mismatch between the fundamental and the first-order modes that constitute the two interacting waves is controlled by wavelength tuning. A strong power dependence of the modulational instability spectra is observed near the condition of group-velocity matching.
1 Tb/s·km WDM transmission over multimode fibre link
2008
We demonstrate 1 Tb/smiddotkm WDM error-free transmission (highest reported value to our knowledge) over a MMF link by a combination of low-linewidth lasers and central launch.
Limits of ultra-high bit rate RZ data transmissions in terrestrial optical fiber systems
2006
We numerically study the limits of the terrestrial optical fiber systems as a function of the bit rate. In particular, we compare for 160-, 320- and 640-Gbit/s the limits of single channel and WDM configurations.
Polychromatic Cherenkov radiation and supercontinuum in tapered optical fibers
2012
We numerically demonstrate that bright solitons in tapered optical fibers can emit polychromatic Cherenkov radiation providing they remain spectrally close to the zero dispersion wavelength during propagation along the fiber. The prime role in this phenomenon is played by the soliton self-frequency shift driving efficiency of the radiation and tuning of its frequency. Depending on tapering and input pulse power, the radiation is emitted either as a train of pulses at different frequencies or as a single temporally broad and strongly chirped pulse.
Multi-peak-spectra generation with Cherenkov radiation in a non-uniform single mode fiber
2014
We propose, by means of numerical simulations, a simple method to design a non-uniform standard single mode fiber to generate spectral broadening in the form of "ad-hoc" chosen peaks from dispersive waves. The controlled multi-peak generation is possible by an on/off switch of Cherenkov radiation, achieved by tailoring the fiber dispersion when decreasing the cladding diameter by segments. The interplay between the fiber dispersion and the soliton self-frequency shift results in discrete peaks of efficiently emitted Cherenkov radiation from low order solitons, despite the small amount of energy contained in a pulse. These spectra are useful for applications that demand low power bell-shaped…
Optimization of wavelength division multiplexing in N×160Gbit/s terrestrial transmission systems
2005
Abstract We analyze, from an engineering viewpoint, the prospects of an exploitable upgrade of terrestrial fiber systems based on standard monomode fiber and dispersion compensating units, for future N × 160 Gbit/s transmission systems. We show that dispersion swing, average dispersion and input pulse power are the key parameters that govern the system performances. We show that whenever the dispersion swing is arranged in a symmetrical setup and the compensation ratio is optimized accordingly, one may obtain a significant improvement of the transmission performances.
All-optical simultaneous polarization attraction and intensity regeneration of a 40-Gbit/s RZ signal
2011
We experimentally report the dual all-optical instantaneous regeneration of both the state of polarization and the intensity profile of a 40 Gbit/s Return-to-Zero telecommunication signal by means of a unique segment fiber.
The Be/X-ray Transient V0332+53: Evidence for a tilt between the orbit and the equatorial plane?
1999
We present optical and infrared observations of BQ Cam, the optical counterpart to the Be/X-ray transient system V0332+53. BQ Cam is shown to be an O8-9Ve star, which places V0332+53 at a distance of ~7 kpc. H-alpha spectroscopy and infrared photometry are used to discuss the evolution of the circumstellar envelope. Due to the low inclination of the system, parameters are strongly constrained. We find strong evidence for a tilt of the orbital plane with respect to the circumstellar disc (pressumably on the equatorial plane). Even though the periastron distance is only ~ 10 R_*, during the present quiescent state the circumstellar disc does not extend to the distance of periastron passage. U…