Search results for "Fiber optic"

Measurement of temperature profile induced by the optical signal in fiber Bragg gratings using whispering-gallery modes.

2014

The temperature sensitivity of whispering-gallery mode resonances of an optical fiber is exploited to measure thermal effects induced by an optical signal of moderate power along a fiber Bragg gating (FBG). The UV inscription technique used for the fabrication of FBG introduces a permanent change in the absorption coefficient of the fiber; thus, thermal effects are expected. The resonance wavelength shift of whispering-gallery modes provides information about the temperature change in the fiber, point to point. We present the experimental characterization of the thermal effects in FBG as a function of the wavelength and the power of the launched optical signal through the grating.

Fiber laser with cladding-mode feedback based on intracavity long period grating

2011

Cladding modes in fiber laser technology have considerable interest for dispersion compensation [1] and power scaling [2, 3]. A fiber laser with core-cladding conversion was made in convectional Erbium doped fiber by a combination of Bragg and external cavity mirrors and blocking the fundamental mode with a damaged core fiber [2]. Furthermore, the insertion of two long period gratings (LPG) in a fiber Bragg gratings (FBG) Fabry-Perot cavity has been proposed as a potential high-order-mode fiber laser [3]; however, no experimental demonstration has been reported yet because there are no ring-doped fibers available in the market. In this work, we present the first demonstration of an all-fibe…

Determination of the position of defects generated within a chirped fiber Bragg grating by analyzing its reflection spectrum and group delay

2016

We determinate the position of defects generated within a chirped fiber Bragg grating by analyzing its reflection spectrum and group delay. Simulations were performed by using the T-matrix method for different defect locations.

Fully automatic simultaneous fiber grating amplitude and group delay characterization

1997

Fabrication of chirped fiber Bragg gratings by simple combination of stretching movements

2008

Abstract A new stretching technique to fabricate chirped fiber Bragg gratings using a nonchirped phase mask is presented. It is based on continuous stretching and continuous UV beam scanning, which ensures phase matching between periods along the grating. Simple combinations of the fiber stretching movements of a pair of piezoelectric transducers are used to avoid unwanted period blurring and wavelength shifting. A third piezoelectric transducer can be easily added to the system to provide independent apodization through phase mask dithering. Successful fabrication of apodized and nonapodized chirped fiber gratings has been performed with this technique.

All-fiber noninterferometric narrow-transmission-bandpass filter

2012

In-fiber mode engineering based on the combination of Bragg and long-period gratings (LPGs) permits the implementation of noninterferometric transmission filters with narrow passbands using standard single-mode fiber. The design of the bandpass filter is based on the coupling between propagating and counterpropagating cladding modes in two fiber Bragg gratings. A LPG located between the Bragg gratings transfers power from the input fundamental mode to a specific cladding mode and recouples the filtered signal to the output fundamental mode. The filter produces a series of narrow passbands of about 30 pm linewidth with a maximum transmittance above 60%, 20 dB isolation, and passband separati…

Actively Q-switched all-fiber lasers

2007

Q-switching of fiber lasers using bulk elements has important drawbacks as reduced mechanical stability and high insertion losses. The development of efficient all-fiber modulation techniques is the key to obtain robust, compact and efficient Q-switched all-fiber lasers. Certainly, the development of fiber Bragg gratings (FBG) has been crucial to make progress on fiber lasers. FBGs permit a simple way to assemble all-fiber laser cavities and can be written in the active fiber itself. The Q-factor of this type of cavities is determined by the reflectivity of the FBGs and the losses of the fiber. Here, we focus on the use of magnetostrictive materials and the acousto-optic interaction to deve…

Radiation Vulnerability of Fiber Bragg Gratings in Harsh Environments

2015

International audience; The difficulties encountered in the implementation of a temperature or strain sensor based on fiber Bragg grating (FBG) in a harsh radiative environment are introduced. We present the choices made to select both a radiation-resistant fiber in terms of transmission and also the grating inscription conditions necessary to write radiation tolerant FBGs in such fibers with a femtosecond laser. The radiation response of these gratings was also studied under radiation at dose up to 1 MGy. The comparison between Ge-free and Ge-doped fibers was highlighted.

Electrically tunable photonic true-time-delay line

2010

We present a new application of the acousto-optic superlattice modulation of a fiber Bragg grating based on the dynamic phase and group delay properties of this fiber-optic component. We demonstrate a tunable photonic true-time-delay line based on the group delay change of the light reflected from the grating sidebands. The delay is electrically tuned by adjusting the voltage applied to a piezoelectric transducer that generates the acoustic wave propagating along the grating. In our experiments, a true-time delay of 400 ps is continuously adjusted (300 ps within the 3 dB amplitude range of the first sideband), using a 12 cm long uniform grating.

Efficient excitation of photoluminescence in a two-dimensional waveguide consisting of a quantum dot-polymer sandwich-type structure

2014

International audience; In this Letter, we study a new kind of organic polymer waveguide numerically and experimentally by combining an ultrathin (10–50 nm) layer of compactly packed CdSe/ZnS core/shell colloidal quantum dots (QDs) sandwiched between two cladding poly(methyl methacrylate) (PMMA) layers. When a pumping laser beam is coupled into the waveguide edge, light is mostly confined around the QD layer, improving the efficiency of excitation. Moreover, the absence of losses in the claddings allows the propagation of the pumping laser beam along the entire waveguide length; hence, a high-intensity photoluminescence (PL) is produced. Furthermore, a novel fabrication technology is develo…