Search results for "Fiber optic sensor"

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.

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.

An optical pulse modulator based on an all-fiber mirror

1996

Self-referenced phase reconstruction proposal of Ghz bandwidth non-periodical optical pulses by in-fiber semi-differintegration

2011

Abstract We propose two new techniques able to retrieve the phase profile of a given temporal optical pulse based on the use of in-fiber semi-differintegral operators, where by semi-differintegration we mean either a 0.5th-order differentiation or integration. In both cases, the signal's temporal phase can be obtained by simple dividing two temporal intensity profiles, namely the intensities of the input and output pulses of a spectrally shifted semi-differintegral operator. In both cases, we obtained simple analytical expressions for the phase profile. The techniques are self-referenced and well-suited for real-time applications. We numerically prove the viability of these proposals.

PON Monitoring Technique Based on 2D Encoders and Wavelength-to-Time Mapping

2020

A PON monitoring technique is demonstrated based on an OTDR-like device and FBG-encoders having a unique combination of central wavelength and reflection bandwidth. This results in more compact and cost-efficient encoders than previous proposals.

Effects of radiation and hydrogen-loading on the performances of raman-distributed temperature fiber sensors

2015

International audience; The integration of Raman-distributed temperature fiber-based sensors (RDTS) into the envisioned French deep geological repository for nuclear wastes, called Cigéo requires evaluating how the performances of RDTS evolve in harsh environments, more precisely in presence of H2 or γ-rays. Both H2 and radiations are shown to affect the temperature measurements made with the single-ended RDTS technology. The amplitudes of the observed effects depend on the different classes of multimode fibers varying in terms of composition and coatings. By selecting the most tolerant fiber structure for the sensing, we could maintain the RDTS performances for such application. A hardeni…

Improved time-resolved acousto-optic technique for optical fiber analysis of axial non-uniformities by using edge interrogation

2015

The time-resolved acousto-optic technique demonstrated recently to be a very useful method for the analysis of fiber axial non-uniformities, able to detect variations of fiber diameter in the nanometric scale with a spatial resolution of few cm. An edge interrogation approach is proposed to improve further the performance of this technique. The detection of subnanometer fiber diameter changes or sub-ppm changes of the core refractive index is demonstrated.

Extreme statistics in Raman fiber amplifiers : influence of pump depletion and dispersion

2010

OSA 2010 NonLinear Photonics Best Student Poster Award; International audience; We experimentally and theoretically investigate the influence of pump depletion effects on extreme statistics observed in fiber Raman amplifiers. We also report on the impact of the dispersion of the fiber.

Theoretical study of microfiber resonator devices exploiting a phase shift

2008

Phase shifts within microfiber resonators can be exploited to demonstrate compact and fast-responding devices. Two examples, a sensor and a bistable device, where the origins of the phase shift are fundamentally different, are investigated. In the sensor the phase change originates from the change of refractive index of the medium surrounding the microfiber ring. This is a linear mechanism which translates into a change of resonance wavelength. Calculations of a silica microfiber ring immersed in an aqueous solution and operating at a wavelength of 1550 nm show that with a fiber 550 nm in diameter the sensitivity approaches a maximal value of about 1137 nm/RIU. In contrast to the sensitivit…