Hans Georg Limberger

Chattez avec Graph Search

Posez n’importe quelle question sur les cours, conférences, exercices, recherches, actualités, etc. de l’EPFL ou essayez les exemples de questions ci-dessous.

AVERTISSEMENT : Le chatbot Graph n'est pas programmé pour fournir des réponses explicites ou catégoriques à vos questions. Il transforme plutôt vos questions en demandes API qui sont distribuées aux différents services informatiques officiellement administrés par l'EPFL. Son but est uniquement de collecter et de recommander des références pertinentes à des contenus que vous pouvez explorer pour vous aider à répondre à vos questions.

Good thermal and mechanical reliability of fiber Bragg gratings are indispensable requirements for telecommunication and sensor applications. The basic model of thermal reliability is reviewed and the lifetime of Bragg gratings in different germanosilicate fibers is evaluated. Very good thermal stability over 50 years can be predicted for germanosilicate fibers if the gratings are annealed for 50 hours at T Å 120°C. The mechanical reliability of irradiated fiber is shown to depend strongly on the

Driven by the exponentially growing demand for capacity, it is already apparent that the next generation of telecommunication networks will be radically different from previous implementations; coherent detection along with powerful digital signal processing will be deployed to maximize the available capacity of each fiber strand within the network. However, applied in isolation these techniques will only delay the inevitable "capacity crunch" by a few years and without radical innovation in the basic inter

Fiber Bragg Gratings were fabricated using a 193-nm-ArF-excimer laser with ac index changes of 0.6×10E-4 and 2.2×10E-4 in pristine and H2-loaded Bi-Al-SiO2 fibers. Thermal annealing of the FBGs was investigated using continuous isochronal annealing. ...

The issue of mechanical resistance of optical fibers irradiated by UV laser sources has been recently reported. An important mechanical degradation as expressed by the decrease of median breaking strength and the widening of the Weibull distribution has been observed after homogenous irradiation by pulsed laser sources. In contrary, CW UV laser irradiation showed considerably better results exhibiting median breaking strengths and m-values very close to that of pristine fiber. The effect has an important im

Wavelength demultiplexing is a very promising application of photoinduced fiber gratings. In this paper efficient outcoupling of a very narrow wavelength band, in addition to the usual guided Bragg reflection, is presented. The selective outcoupling gratings were fabricated by focusing the irradiation beam to a dimension smaller than the core diameter of a standard fiber. The highly selective outcoupling of such devices might increase the multiplexing density

Rare-earth doped fibers can be used to realize simple, compact sources of ultrashort pulses. To date, considerable effort has been developed to obtain short pulse generation in Er3+-doped fiber lasers at 1.55 μm. Contrary to this, little work has been done on Pr3+-doped fiber lasers emitting an important 1.3 μm. This report describes an all-fiber laser incorporating a Pr3+-doped active fiber, fiber Bragg gratings (FBGs) as cavity mirrors, and a novel piezoelectric fiber-optic phase modulator (PFOM) for acti

A wavelength monitor based on a pair of tilted fiber Bragg gratings with low insertion loss (<1 dB) and sub-picometer wavelength resolution is reported. ...

Strong correlation between index change and stress change in irradiated optical fibers is reported. The stress increases with fluence. Stress changes and hence index changes seem to be due to a compaction of the fiber core

An all-fiber phase-modulated master oscillator power amplifier for free-space coherent communication is presented. A distributed-feedback fiber laser at 1.06 μm is used as master oscillator. A novel phase modulator based on a ZnO-coated single-mode fiber modulates the single frequency communication signal. The modulated signal is then amplified in a double-clad doped fiber power amplifier. Up to 1 W cw single-frequency output power, phase modulated at 196 MHz, has been obtained.

An all-fiber phase modulator based on lead titanate zirconate coating deposited by dc reactive magnetron sputtering was fabricated and optically characterized. The frequency response showed a flat broadband structure up to 600 kHz, with an efficiency of 0.73 rad/(V m). This is an order of magnitude higher than that for sputtered zinc oxide based phase modulators. Radial mode resonance peaks were observed between 10 and 700 MHz, with a maximum phase modulation amplitude of 0.3 rad at the fundamental radial r

We report on mode field diameter changes of -31% due to UV-induced core refractive index changes of

We present a simple technique to precisely and continuously adjust the resonance wavelengths of long-period cladding-mode-coupled gratings without strongly affecting the coupling strength. The main principle of this method is based on the strong dependence of the propagation constants and hence the peak positions of the cladding modes on the cladding diameter. Therefore, one can shift the grating resonance wavelength by changing the cladding dimension. In our case, this has been achieved by etching the fibe

Fiber Bragg gratings fabricated in pristine SMF-28e fibers using pulsed ArF-excimer and cw 244-nm Ar+ laser were annealed using tempering rates from 0.0038 to 0.25 K/s. Demarcation energy mapping allowed for the determination of the frequency factors and t ...

In this paper, the behaviour of fibre Bragg grating sensors subjected to transversal as well as axial strains is characterized, both in the case of low-birefringent and polarization-maintaining single-mode optical fibres. Two configurations are considered. Firstly, diametrical compression is studied and the results compared to those previously obtained in the literature. Secondly, the sensors are embedded in an epoxy specimen and their response monitored when the latter is subjected to biaxial loading. In b

LP01-LP02 mode converters based on UV-written intracore gratings have been fabricated for chromatic-dispersion compensation. The mode converters operate in transmission at wavelengths near 1550 nm with spectral bandwidths of 14-25 nm and coupling efficiencies of as much as 90%. A large negative dispersion of -335 ps/(nm km) is obtained for a compensator consisting of the mode converter and a 1490-m-long few-mode fiber. The compensator shows negative dispersion over a wavelength region of 5 nm. Its figure of

Bi:SiO2 fiber drawn under oxidizing conditions shows ultra-low photosensitivity and no NIR luminescence under 1064 nm pumping. Hydrogen loading followed by ArF irradiation induced both. The increase of photosensitivity and the creation of luminescence cent ...

Mean index changes up to 2.2 × 10-3 were demonstrated in hydrogen loaded germanium free Bi-Al-doped silica fibers. Tensile stress changes indicate a contribution of compaction to the total index change. ...

An optical fiber sensor to simultaneously measure strain and temperature was designed and embedded into an adaptive composite laminate which exhibits a shape change upon thermal activation. The sensor is formed by two fiber Bragg gratings, which are written in optical fibers with different core dopants. The two gratings were spliced close to each other and a sensing element resulted with Bragg gratings of similar strain sensitivity but different response to temperature. This is due to the dependence of the

Unusually high ionization energies have been observed for Cs-O clusters having certain sizes and compositions, namely for Cs/sub 2n+z/O/sub n/ with z=8, 18, 34, 58 and 92. The anomalies are well defined for clusters containing from one to seven oxygen atoms. The indicated values of z are identical to the numbers of electrons in closed shells of angular momentum.

We report the first demonstration of an extremely simple and efficient 1.24 μm phosphosilicate fiber-based Raman laser with Bragg gratings written directly in the fiber used. The laser pumped by Nd fiber laser exhibits a slope efficiency of 80%

Hans Georg Limberger

Chattez avec Graph Search

Reliability aspects of fiber Bragg gratings - invited

Workshop: Next-Generation Fibers for High Capacity Transmission—Radical Solutions

Thermal decay of UV Ar+ and ArF excimer laser fabricated Bragg gratings in SMF-28e and Bi-Al-doped optical fiber

High mechanical resistant fiber Bragg gratings fabricated by CW UV laser irradiation

Bragg gratings with directional, efficient, and wavelength-selective fiber outcoupling

Stable picosecond pulse generation at 1.3 mm in a Pr3+-doped all-fiber laser actively mode-locked using a fiber-optic phase modulator.

Low loss wavelength monitor with sub-picometer resolution based on tilted fiber gratings

Correlation of index changes with stress changes in fibers containing UV-written Bragg gratings

All-fiber phase-modulated master oscillator power amplifier for coherent communication

All-fiber phase modulator based on lead zirconate titanate thin-film coating

Fabrication of mode field converter in H2-loaded SMF-28e using CW-Ar+ laser

Post-irradiation resonance wavelength adjustment of long period grating based loss filters

Annealing of UV Ar+ and ArF excimer laser fabricated Bragg gratings: SMF-28e fiber

Characterization of the response of fibre Bragg grating sensors subjected to a two-dimensional strain field

Efficient broadband intracore grating LP01-LP02 mode converters for chromatic-dispersion compensation

Photosensitivity and Luminescence Induced by ArF-Irradiation of Hydrogen Loaded Bi-SiO2 Fiber

UV-Photosensitivity of Germanium-free Bi-Al Silica Fibers

In-situ simultaneous strain and temperature measurement of adaptive composite materials using a fiber Bragg grating based sensor

Evidence of electronic shell structure in Cs-O clusters

CW highly efficient 1.24 μm Raman laser based on low-loss phosphosilicate fiber