Search results for "Grating"

Simple guidelines to predict self-phase modulation patterns

2018

International audience; We present a simple approach to predict the main features of optical spectra affected by self-phase modulation (SPM), which is based on regarding the spectrum modification as an interference effect. A two-wave interference model is found sufficient to describe the SPM-broadened spectra of initially transform-limited or up-chirped pulses, whereas a third wave should be included in the model for initially down-chirped pulses. Simple analytical formulae are derived, which accurately predict the positions of the outermost peaks of the spectra.

Periodic time-domain modulation for the electrically tunable control of optical pulse train envelope and repetition rate multiplication

2012

An electrically tunable system for the control of optical pulse sequences is proposed and demonstrated. It is based on the use of an electrooptic modulator for periodic phase modulation followed by a dispersive device to obtain the temporal Talbot effect. The proposed configuration allows for repetition rate multiplication with different multiplication factors and with the simultaneous control of the pulse train envelope by simply changing the electrical signal driving the modulator. Simulated and experimental results for an input optical pulse train of 10 GHz are shown for different multiplication factors and envelope shapes. © 2006 IEEE.

Photonic fractional Fourier transformer with a single dispersive device

2013

In this work we used the temporal analog of spatial Fresnel diffraction to design a temporal fractional Fourier transformer with a single dispersive device, in this way avoiding the use of quadratic phase modulators. We demonstrate that a single dispersive passive device inherently provides the fractional Fourier transform of an incident optical pulse. The relationships linking the fractional Fourier transform order and scaling factor with the dispersion parameters are derived. We first provide some numerical results in order to prove the validity of our proposal, using a fiber Bragg grating as the dispersive device. Next, we experimentally demonstrate the feasibility of this proposal by us…

New solvability conditions for the Neumann problem for ordinary singular differential equations

2000

Stochastic Differential Equations

2020

Stochastic differential equations describe the time evolution of certain continuous n-dimensional Markov processes. In contrast with classical differential equations, in addition to the derivative of the function, there is a term that describes the random fluctuations that are coded as an Ito integral with respect to a Brownian motion. Depending on how seriously we take the concrete Brownian motion as the driving force of the noise, we speak of strong and weak solutions. In the first section, we develop the theory of strong solutions under Lipschitz conditions for the coefficients. In the second section, we develop the so-called (local) martingale problem as a method of establishing weak so…

On ordinary differential equations with interface conditions

1968

Intellectual evolution of strategic management and its relationship with ethics and social responsibility

2006

The main purpose here is to present an overview of the historical development of strategic management, through a critical review of the most relevant theoretical proposals, and to consider its links to ethics and corporate social responsibilities. From the very beginning of strategic management thought attempts have been made to fuse ethical aspects such as values of senior management or social values or social expectations to strategic management. More recently the stakeholder view of the firm has permitted the introduction of ethical theories into strategic management, and the resources-based view of the firm has lead to the consideration of competences, including moral virtues. Here it i…

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.

Radiation tolerant fiber Bragg gratings for high temperature monitoring at MGy dose levels

2014

International audience; We report a method for fabricating fiber Bragg gratings (FBG) resistant to very severe environments mixing high radiation doses (up to 3 MGy) and high temperatures (up to 230 degrees C). Such FBGs have been written in two types of radiation resistant optical fibers (pure-silica and fluorine-doped cores) by exposures to a 800 nm femtosecond IR laser at power exceeding 500 mW and then subjected to a thermal annealing treatment of 15 min at 750 degrees C. Under radiation, our study reveals that the radiation induced Bragg wavelength shift (BWS) at a 3 MGy dose is strongly reduced compared to responses of FBGs written with nonoptimized conditions. The BWS remains lower t…

Direct Bragg grating writing in a hybrid PDMS/silica photonic crystal fiber

2011

Infiltration of materials into the air holes of the PCFs can potentially manipulate their optical properties creating a new category of fibers termed as hybrid PCFs [1] and many devices based on hybrid PCFs have been developed [2–5]. Recently, a hybrid PCF with poly-dimethylsiloxane (PDMS) elastomer inclusions has been demonstrated [6]. PDMS is widely used in the area of photonics and optofluidics. It is highly transparent with a refractive index ∼1.41, conserving the total internal reflection guiding mechanism of the hybrid PCF. When PDMS is irradiated with UV light its refractive index increases [7]. In this paper we present the first example of a Bragg grating directly written using UV l…