Institut National D'optique

Other

UniversitÈ Laval

Jocelyn Lauzon

Yves Painchaud

Yves Taillon

Pierre Galarneau

Alain Chandonnet

Chiara Meneghini

André Croteau

Pierre Langlois

Martin Guy

Michel B&eacute;gin

Yvan Mimeault

Robert Larose

Carl Paquet

Martin Pelletier

Yves Rouleau

Francedillaois Ouellette

Fran&ccedil;ois Tr&eacute;panier

Jean-Fran&ccedil;ois Couillard

Sylvain Derome

Pierre-Yves Cort&egrave;s

Min Wang

Francois Trepanier

Jean-Francois Couillard

The invention provides a multi-clad fiber, with three claddings or more, where at least one intermediate cladding is inserted between an inner core and an outer core of the multi-clad fiber, for enlarging the cross-section of the fiber core or for increasing the dopant density in the core. The invention also provides an intermediate cladding having a multi-layer structure to better confine the pump power in a suitable pumping region of the fiber.

Multi-clad doped optical fiber

An optical fiber comprises a singlemode core, and an inner cladding disposed around said core, an intermediate cladding disposed around said inner cladding and an outer cladding disposed around said intermediate cladding thereby forming a triple-clad geometry. The core is doped with rare-earth elements and represents the waveguide section of higher refractive index through which the signal is transmitted and amplified. A fiber coating is provided around said outer cladding. The core has a higher refractive index than said inner cladding, said inner cladding having a higher refractive index than said intermediate cladding, and said intermediate cladding having a higher refractive index than said outer cladding. The inner cladding has a fairly high refractive index to limit the numerical aperture (NA) of said core. The inner cladding is within said intermediate, larger, cladding which is made of glass, that is used to guide multimode, high-power pump, said inner cladding acting as an intermediate level between said core and said multi-mode pump guiding intermediate cladding, with said outer cladding being present in said optical fiber for allowing said intermediate cladding to guide the pump power properly. The outer cladding is made of glass or of a low-index polymer material. The inner cladding is adapted to trap some of the pump signal into a smaller section in order to accelerate the absorption of the pump power.

Triple-clad rare-earth doped optical fiber and applications

A tunable phase mask assembly for use in photoinducing an optical wavelength filter in an optical waveguide. The phase mask assembly includes a phase mask having a length extending between two opposite longitudinal ends. The phase mask has grating corrugations projecting from its surface and distributed with a periodicity along its length. The periodicity of the phase mask is tuned by reversibly changing its length between the two longitudinal ends, such as by compressing or stretching the mask. In this manner, the interference pattern of a light beam passing through the phase mask is also tuned, which allows to control the characteristics of a wavelength filter photoinduced using this phase mask assembly.

Tunable phase mask assembly

The present invention concerns a method for fabricating a patterned, poled dielectric structure, comprising the steps of providing a material, patterning a periodic pattern into a first surface, applying an electrode to the first surface, and applying a voltage to the electrode to create a domain inversion in the material. Preferably, the material is a ferroelectric material, and the electrode is a single, planar, solid electrode. The method proposed herein is simple, reproducible and economical, as compared to prior methods. Patterned, poled dielectric structures are used to generate optical frequency conversion, by creating quasi-phase matching between two optical signals.

Method for the fabrication of patterned poled dielectric structures and devices

A wavelength tunable optolelectronic device. Two channel waveguides are provided in an optoelectronic structure made of a ferroelectric material. The waveguides are adjacent along at least a coupling region. A periodically poled structure is provided in the coupling region, and at least one of the waveguides is untouched by this structure. An electric field is applied in the coupling region, through both waveguides, to enable coupling a light of a given wavelength between the two waveguides. The amplitude of the electric field may be selected to tune the coupling wavelength. A third waveguide or more having a coupling region in common with the second waveguide may also be added to allow the bandwidth of the resulting beam to also be tuned.

Tunable optoelectronic frequency filter

An optical fiber pumping apparatus for use with a double-cladding fiber in an optical amplifier or laser configuration comprises a plurality of laser diodes used as pump sources disposed in a spatial configuration for radiating pump energy along an optical axis through a surrounding generally annular area, leaving an available middle area. The apparatus further comprises an optical coupling device having an optical input portion generally aligned with the optical axis to collect the pump energy and having an optical output portion aligned with the pumping input portion for transferring the pump energy to the inner cladding surrounding the doped core of the fiber. The apparatus exhibits high pump power rating and allows efficient input signal coupling in optical fiber amplifier applications. According to the different preferred embodiments, the apparatus can act either simultaneously or independently as a pump combiner, multiple pump injector, signal coupler or pump/signal multiplexer/demultiplexer.

Optical fiber pumping apparatus and method for use in pumped optical fiber amplifier and laser systems

A low-cost superfluorescent fiber souce. A gain medium in a length of optical fiber is pumped in counter-propagation by a pump source, producing superfluorescent radiation. The pump source is coupled to the fiber by a first coupler, disposed forward of the gain medium, that selectively transmits the pump signal in the backward direction, and the superfluorescence in the forward direction. A second coupler is disposed backward of the gain medium, selectively transmitting the backward propagating superfluorescent radiation along a first path and the pump signal along a second path, the pump signal is absorbed in the second path by a high-attenuation fiber, to avoid feedback to the pump laser, and the superfuorescent is reflected in the first path back toward the source output. Advantageously, this source can be realized with readily available optical components that are easy to assemble and do not require any alignment.

Superfluorescent fiber source

A gain-locked dual stage or multi stage optical amplifier. The input signal is injected into an optical waveguide, such as an optical fiber, provided with at least a first and a second amplifying stage. Each amplifying stage is pumped by a corresponding pump source producing a pump signal having an initial pump power value. Means are provided to monitor the initial pump power of the first pump source, the initial pump power of the second pump source and the pump power of the portion of this signal unabsorbed by the first amplifying stage. The initial pump power of the first and second pump signals are controlled together, being set to a same controlled value which is calculated based on the pump power of the unabsorbed signal from the first amplifying stage.

Gain-locked dual stage optical amplifier

A method and an apparatus to photoinduce a grating or other type of modulated refractive index change in a photosensitive optical medium such as optical fiber. The resulting grating has a variable and controllable intensity profile and average value of the index change. The modulated refractive index change is photoimprinted in the medium in a series of writing steps, each comprising exposing a segment of the medium to a writing beam for a predetermined exposure time. To change the modulation intensity from step to step, the angle of incidence of the writing beam is dithered for an appropriate fraction of the exposure time at each step. This allows to control the amount of incident light on the medium for each step. If the exposure time is the same for each writing step, the average value of the index change may be kept constant avoiding undesired structure in the grating frequency response.

Method and apparatus for spectrally designing all-fiber filters

The amplifier is a two-stage amplifier in which dispersion compensation and WDM channel equalization are carried out using a plurality of in-waveguide Bragg gratings placed between the two stages. The first stage has a gain able to raise the intensity of WDM optical communications signals to a high enough level that after dispersion compensation and equalization, the signals fed into the second stage nearly or substantially saturate the second stage amplifier. The noise figure signal-to-noise ratio is thereby of good quality since there are no significant losses at the signal input of the signal into the optical amplifier. Erbium-doped optically pumped fiber amplifiers are used for the two stages. An add/drop filter can be appended to the end of the conditioning Bragg gratings. Residual optical signal from the fiber Bragg grating may be used to optically pump another amplifier for amplifying longer wavelength optical signals.

In-fiber two-stage amplifier providing WDM signal conditioning

A method for spatially controlling the period and amplitude of Bragg filters in an optical medium having a longitudinal axis that is sensitive to at least some wavelength of electromagnetic radiation. A phase mask of period .LAMBDA. is laid close to the optical medium at an angle .alpha. with respect to the longitudinal axis of the optical medium. A single beam of electromagnetic radiation is directed at an incidence angle .phi. with respect to normal incidence on the phase mask so that the radiation is diffracted, resulting in an interference pattern having a period P impinged into the optical medium so that the period P of the interference pattern may be altered by changing the incidence angle .phi. or the angle .alpha.. This method is simpler, more flexible and more suitable for mass production than existing methods.

Method for spatially controlling the period and amplitude of BRAGG

A fused fiber filter coupler is disclosed characterized in that a long period grating is written in at least a portion of the waist of the coupler. The two fibers which make up the coupler have respective propagation constants .beta..sub.fiber1 and .beta..sub.fiber2 which are different and both fibers are singlemode at the wavelength of operation. In order for an efficient grating to be written in the waist of the coupler, the couple must be photosensitive in at least a region of the waist. Since the propagation constant is a function of the wavelength and the period of the grating is given by the expression .LAMBDA.=2 .pi./(.beta..sub.fiber1 -.beta..sub.fiber 2), the filter may be tuned to a particular wavelength by adjusting the period of the grating. The filter so constructed acts in transmission and can discriminate wavelengths of the order of 1 nm. The filter is particularly useful in wavelength-rich optical communications networks to extract a particular wavelength from a signal or to add a particular wavelength to a signal (i.e. multiplexing and demultiplexing).

Grating assisted fused fiber filter

A method for spatially controlling the period and amplitude of Bragg filters in an optical medium having a longitudinal axis that is sensitive to at least some wavelength of electromagnetic radiation. A phase mask of period .LAMBDA. is laid close to the optical medium at an angle .alpha. with respect to the longitudinal axis of the optical medium. A single beam of electromagnetic radiation is directed at an incidence angle .phi. with respect to normal incidence on the phase mask so that the radiation is diffracted, resulting in an interference pattern having a period P impinged into the optical medium so that the period P of the interference pattern may be altered by changing the incidence angle .phi. or the angle .alpha. . This method is simpler, more flexible and more suitable for mass production than existing methods.

Method for spatially controlling the period and amplitude of Bragg

A linear chirp is imposed on a fibre Bragg grating by means of a temperature gradient impressed on the grating. An optical fibre containing a fibre Bragg grating is set in a groove in an elongated plate. A temperature gradient is imposed on the plate by the applying heat to each end of the plate containing the optical fibre. The heat is applied by means of Peltier effect plates which sandwich each end of the elongated plate. Thermistors are applied to the elongated plate between the Peltier effect plates to provide feedback as to the temperature of the elongated plate and to enable an estimate to be made of the gradient across the fibre Bragg grating.

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Saint-Augustin-de-Desmaures, Canada

Jocelyn Lauzon