Résumé
A fiber Bragg grating (FBG) is a type of distributed Bragg reflector constructed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all others. This is achieved by creating a periodic variation in the refractive index of the fiber core, which generates a wavelength-specific dielectric mirror. Hence a fiber Bragg grating can be used as an inline optical fiber to block certain wavelengths, can be used for sensing applications, or it can be used as wavelength-specific reflector. The first in-fiber Bragg grating was demonstrated by Ken Hill in 1978. Initially, the gratings were fabricated using a visible laser propagating along the fiber core. In 1989, Gerald Meltz and colleagues demonstrated the much more flexible transverse holographic inscription technique where the laser illumination came from the side of the fiber. This technique uses the interference pattern of ultraviolet laser light to create the periodic structure of the fiber Bragg grating. The fundamental principle behind the operation of an FBG is Fresnel reflection, where light traveling between media of different refractive indices may both reflect and refract at the interface. The refractive index will typically alternate over a defined length. The reflected wavelength (), called the Bragg wavelength, is defined by the relationship, where is the effective refractive index of the fiber core and is the grating period. The effective refractive index quantifies the velocity of propagating light as compared to its velocity in vacuum. depends not only on the wavelength but also (for multimode waveguides) on the mode in which the light propagates. For this reason, it is also called modal index. The wavelength spacing between the first minima (nulls, see Fig. 2), or the bandwidth (), is (in the strong grating limit) given by, where is the variation in the refractive index (), and is the fraction of power in the core. Note that this approximation does not apply to weak gratings where the grating length, , is not large compared to \ .
À propos de ce résultat
Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.
Cours associés (6)
EE-440: Photonic systems and technology
The physics of optical communication components and their applications to communication systems will be covered. The course is intended to present the operation principles of contemporary optical comm
MICRO-426: Laser fundamentals and applications for engineers
The course will cover the fundamentals of lasers and focus on selected practical applications using lasers in engineering. The course is divided approximately as 1/3 theory and 2/3 covering selected
PHYS-317: Optics I
L'optique est un vieux domaine qui touche à beaucoup de sujets modernes, des techniques expérimentales aux applications courantes. Ce premier cours traite plusieurs aspects de base de l'optique: propa
Afficher plus
Publications associées (436)
Concepts associés (1)
Fibre optique
Une fibre optique est un fil dont l’âme, très fine et faite de verre ou de plastique, a la propriété de conduire la lumière et sert pour la fibroscopie, l'éclairage ou la transmission de données numériques. Elle offre un débit d'information nettement supérieur à celui des câbles coaxiaux et peut servir de support à un réseau « large bande » par lequel transitent aussi bien la télévision, le téléphone, la visioconférence ou les données informatiques.