Advanced radiation tolerant Erbium doped fibers have been developed surviving an accumulated dose of 1 kGy∗. Femtosecond fiber lasers and amplifiers manufactured from such fibers have been packaged and irradiated under active operation to test for accelerated ageing with dose rates up to 10 mGy/s using a Cobalt 60 source. The laser output power degraded by about 11% after exposure of a dose of 1 kGy. Compared to conventional Erbium fiber lasers this represents a significant improvement in radiation tolerance.
Based on the experience acquired early from pioneering work at Stanford University and Thomson-CSF starting in the mid 70s, fiber optic gyro (FOG) R&D began at Photonetics in the late 80s to yield OCTANS, a FOG-based inertial strapdown system providing attitude and gyro compassing, at the end of the 90s. This FOG activity was spun out from Photonetics in October 2000 to create iXsea with only 16 people. The product line was rapidly expanded with PHINS, an inertial-grade INS (Inertial Navigation System) and later with MARINS, a strategic-grade INS, as well as with ASTRIX systems developed for satellites in cooperation with EADS-Astrium (today Airbus Defence & Space). In 2010, iXsea merged with several subsidiaries of its parent company, iXcore, to create iXblue. Among these subsidiaries were iXfiber, a maker of specialty fibers, and Photline, producing lithium-niobate integrated optics, hence allowing iXblue to fully master the key FOG components supply chain. Ten years later, the ‘adventure' is continuing and the former start-up is now quite a significant player in the inertial world, especially for high-grade applications. The cumulated number of high-performance 3-axis systems in service has grown to over 8,000, i.e. more than 25,000 FOG axes, with a bias stability ranging from 30 mdeg/h down to 15 μdeg/h, and an angular random walk (ARW) performance ranging from 8 mdeg/√h down to 40 μdeg/√h depending on the size of their sensing coils (3 m2 to 1000 m2) and on the application!
Erbium-ytterbium co-doped phospho-silicate double-clad fibers are used in many applications were powerful 1.5 μm sources are needed, such as telecommunication systems, LIDAR, medical lasers and much more. These fibers are typically pumped with diodes emitting at 915, 940 or 976nm to excite Ytterbium ions, which in turn transfer their energy to erbium ions through a phonon-assisted mechanism, thus leading to 1.5 μm emission. This energy transfer requires a large phosphorous content in the core of the fiber and therefore these fibers exhibit typically high numerical apertures. Properly optimized, the ytterbium to erbium ratio will minimize parasitic emission at 1 μm which provokes system failures through non-controlled spurious laser effects. We have recently observed, on such optimized fibers exhibiting 12 μm core diameter and 0.20 numerical aperture, that long term operation in CW mode in both amplifier and laser configuration, leads to a slow and irreversible decrease of the output power. This phenomenon starts at moderate signal power of just 7W and increases rapidly with the output power. This phenomenon is also observed in polarization maintaining version of the very same fibers. We have studied this phenomenon which resembles the well-known photodarkening effect in Ytterbium doped fibers. Our experiments show that all the commercially available fibers tested exhibit the same behavior. We will present a tentative explanation of the phenomenon and some solutions we implemented to drastically stabilize the output powers up to 20W enabling the use of such fibers in many industrials applications.
HOBAN (Development of Hard Optical Fiber BrAgg GratiNgs Sensors) is an European H2020 project granted by Kic InnoEnergy and aiming the development of fiber-based temperature and strain monitoring systems that can withstand harsh nuclear environment (350°C temperature and MGy dose levels). The objective will be achieved by employing ‘ad hoc’ fiber Bragg grating (FBG) sensors and their associated instrumentation system which will bring to the market new tools for optimizing the running and the services in current and future nuclear power plants. We’ll present the challenges associated with this project and recent advances at the OFS conference.
We study guided acoustic wave Brillouin scattering (GAWBS) in several photonic crystal fibers (PCF) with different
kind of air-hole microstructure and we show this effect is enhanced only for a few acoustic phonons. The results of our
numerical simulations based on a finite element method reveal that these acosuti waves emitted in the GHz range are
indeed trapped within the air-hole microstructure, in good agreement with experimental observations. The periodic
wavelength-scale air-hole microstructure of solid-core PCFs can indeed drastically alter the transverse elastic waves
distribution and therefore forward Brillouin scattering compared to what is commonly observed in conventional all-silica
fibers. We show additionnally that the elasto-optic diffraction coefficient and the transverse acousto-optic field overlap
are maximum for these acoustic waves. For the most intense GAWBS modes, we investigate the scattering efficiency
and temperature dependence of the fundamental phonon frequency for sensing applications.
We report recent advances in the domain of Highly Non-Linear Photonic Crystal Fibers (HNL-PCFs) especially designed as gain medium for Raman fiber lasers. Indeed, a fiber Raman coefficient as high as 42 W-1.km-1 at 1.12μm has been obtained, while keeping optical losses moderate, below 6 dB/km at this wavelength. We have calculated that only 2 meters of such a germanium doped HNL-PCF is required to obtain an output power in the order of 10W at 1.12 μm with an efficiency of 90%. Experimental output optical spectra of multi-cascades cavities are finally given.
In this paper, we present recent results concerning germanium doped highly non-linear photonic crystal fibres (HNLPCF).
The finite element method is used to predict main fibre properties. The polarization behaviour of HNL-PCF is
discussed in the case of disturbed numerical profiles and real fibres. Characteristics of an optimized germanium doped
HNL-PCF are presented and future prospects for in-device integration are discussed as conclusion.
One of the objectives of NextGenPCF European Union R&D project is to develop compact and low-cost white-light supercontinuum sources, based on the use of microchip lasers and air/silica microstructured optical fibres. In this paper, we present some experimental results obtained with doped or undoped highly nonlinear fibres. We also introduce and discuss some ways of getting blue/UV frequency generation, which is particularly useful for certain specific biomedical applications. Finally, the different methods proposed for supercontinuum generation are compared, in terms of spectral power density and spectrum range.
We demonstrate that second harmonic generation obtained in Ge-doped holey fibres can act as a seed for visible supercontinuum generation. This spectral enlargement is obtained by means of a double-pumping system. By using a microchip laser source delivering sub-nanosecond pulses at 1064 nm and a highly Ge-doped fibre, we obtain a second harmonic generation efficiency of 4.8 % after an optical poling process. A white light continuum extending on more than 250 nm is obtained in visible domain.
We demonstrate a Raman laser made from a grating-free highly-nonlinear photonic crystal fiber. The laser
threshold power is lower than 600 mW and laser power characteristics recorded in experiments are accurately
described from the usual simplest model dealing only with stationary evolutions of total optical powers. Experimental
investigations of the spectral properties of our grating-free Raman fiber laser evidence that the shape
of the Stokes power spectrum remains remarkably Gaussian whatever the incident pump power. Increasing the
incident pump power induces a drift of the Stokes wavelength together with a broadening of the Stokes optical
spectrum. Investigations on the role of light polarization on laser characteristics show that our grating-free
Raman fiber laser behaves as a Raman laser made with a standard polarization maintaining fiber. At high pump
power, the birth of the second-order Stokes wave induces a destabilization of the laser output with the emergence
of self-oscillations of the optical powers which are explained from the interplay between counterpropagating pump
and Stokes waves through stimulated Raman scattering.
Microstructured optical fibers (MOFs) are optical fibers having a periodic air-silica cross-section. The air holes extend along the axis of the fiber for its entire length. The core of the fiber is formed by a missing hole in the periodic structure. Remarkable properties of MOFs have recently been reported. This paper presents new work in the modeling of the propagation characteristics of MOFs using the Finite Element Method (FEM) and the Galerkin Method (GM). This efficient electromagnetic simulation package provides a vectorial description of the electromagnetic fields and of the associated effective index. This information includes accurate determination of the spectral extent of the modes, cutoff properties and mode-field distributions. We show that FEM is well adapted for describing the fields at abrupt transitions of the refractive index while GM has the advantage to accurately analyze MOFs of significant complexity using only modest computational resources. This presentation will focus on the specific techniques required to determine single mode operation, dispersion properties and effective area through careful choice of the geometrical parameters of the fibers. We demonstrate that with suitable geometrical parameters, the zero dispersion wavelength can be shifted. This tool can also provide design criteria for fabricating MOFs and a corresponding map of effective area. This approach is validated by comparison with experimental results and measurements on actual MOFs fabricated at IRCOM and at Alcatel Research and Innovation Center.
The Photonic Crystal Fibres (PCF) are microstructured waveguides
currently developed in the frame of fibre telecommunications. This
study is mainly focused on the improvement of dispersion property
and wide spectral single-mode operating domain. Moreover, these
fibres are highly birefringent and thus are able to maintain
polarization. Consequently, in the astronomical context, this kind
of fibre is a good candidate to design a fibre linked version of
stellar interferometer. In this paper, we experimentally study the
potential of these fibres taking advantage of the wide spectral
single-mode operation. We propose an experimental setup acting as
a two-beam interferometer using PCF. In a first time, the aim of
this experiment is to measure fringes contrast at four different
wavelengths (670 nm, 980nm, 1310 nm and 1543 nm) corresponding to
four spectral band (R, I, J and H-band) with the same couple of
PCF samples.
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