Abstract: A strain-isolated bragg grating temperature sensor includes an optical sensing element 20,600 which includes an optical fiber 10 having at least one Bragg grating 12 disposed therein which is encased within and fused to at least a portion of a glass capillary tube 20 and/or a large diameter waveguide grating 600 having a core and a wide cladding and having the grating 12 disposed therein, which senses temperature changes but is substantially not sensitive to strains on the element caused by the fiber or other effects. Light 14 is incident on the grating 12 and light 16 is reflected at a reflection wavelength ?1. The shape of the sensing element 20,600 may be other geometries and/or more than one concentric tube may be used or more than one grating or pair of gratings may be used or more than one fiber or optical core may be used.

Abstract: A wavelength monitoring device is provided having an optical reflecting element for reflecting an incoming optical signal to a detector, wherein the device features a narrowband optical reflecting element for reflecting only a narrowband portion of the incoming optical signal to the optical reflecting element. The narrowband optical reflecting element has a reflection function having a bandwidth and shape that determines the narrowband portion of the incoming optical signal. The narrowband optical reflecting element may be a Bragg grating for spectrally processing the incoming optical signal, while the optical reflecting element may be a blazed Bragg grating for reflecting the spectrally processing incoming optical signal to the detector. The detector determines an amount of optical power reflected by the Bragg grating and discriminates between reflections of individual gratings, and is a spatial filter for providing a direct correlation between individual detector elements and a specific wavelength range.

Abstract: An optical filter for filtering a spectral profile of an optical signal for providing an output signal having a desire gain profile, such as a flatten gain profile. The filter comprises an optical waveguide that includes a core disposed within a cladding having an outer dimension greater than 0.3 mm. A Bragg grating is imparted or written in the core of the waveguide that attenuates the received optical input signal in accordance with a defined reflection or transmission filter profile. The Bragg grating may be a slanted grating. The filter profile is complementary to the spectral gain profile of the input signal to provide an output signal having a substantially flat spectral profile of a desired wavelength band. The cladding of the waveguide may have a mechanically advantageous outer geometry (e.g., a “dogbone” shape) for allowing an axial compressive force to tune the Bragg grating.

Abstract: An optical device is provided that includes an optical waveguide and a tuning device. The optical waveguide has an outer transverse dimension greater than about 0.3 millimeter (mm), and includes an outer cladding, and at least two cores disposed within the outer cladding, the at least two cores being spaced apart a predetermined distance to couple light from a first core to the other core. The tuning device provides a compressive force on the optical waveguide to couple one or more optical signals from one core to another core.

Abstract: A method and apparatus is provided for detecting peaks in an optical signal. The method comprises the three basic steps of: (1) sampling the optical signal to obtain sampled data containing information about the optical signal; (2) applying a cross-correlation filter on the sampled data to obtain cross-correlated data containing information about one or more peaks in the optical signal; and (3) detecting the one or more peaks in the optical signal based on the cross-correlation data. In one embodiment, the cross-correlation filter has an average value that is less than zero. The step of applying the cross-correlation filter includes reducing random noise present in the sampled data to remove quasi-dc components from the sampled data.

Abstract: A large diameter waveguide is provided having a diameter of at least about 0.3 millimeters, and an outer cladding with an inner core with a blazed grating included therein, which is written into the inner core at an oblique angle relative to a longitudinal axis of the inner core either for attenuating optical light traveling in the optical waveguide, or for reflecting optical light to or from the optical waveguide. The blazed grating has an optical parameter that changes in response to an application of a compressive force on the optical waveguide. The outer cladding may have the blazed grating written therein. The blazed grating has concatenated periodic or aperiodic gratings. The optical waveguide may be shaped like a dogbone structure having wider outer sections and a narrower central section inbetween. The blazed grating is written in the narrower central section of the dogbone structure.

Abstract: A method and corresponding apparatus for determining the centroid (Vc) of a waveform signal being sampled at a set of parameter values (Vi, i=1, . . . , n) yielding a corresponding set of sampled amplitudes (Ai, i=1, . . . , n), each parameter value and corresponding amplitude forming a sampled point (Vi, Ai), the method including the steps of: selecting an amplitude at which to create an interpolated point; interpolating a first parameter value corresponding to the amplitude selected in the step of selecting an amplitude; and performing a centroid calculation using only the sampled points with an amplitude greater than a predetermined threshold. The waveform is sometimes sampled in the presence of background noise, and the method sometimes also includes: estimating the background (Bi) for each value in the set of parameter values at which sampling is performed; and reducing the amplitude (Ai) of each sampled amplitude by the background (Bi) so estimated.

Abstract: An optical filter, including a Bragg grating, is compression tuned such that when under one compressional load (or no load) the grating has a first profile and under a second compressional load the grating has a second profile. One application is to allow the grating filter function to be parked optically between channels of a WDM or DWDM optical system.

Abstract: A fiber grating pressure sensor for use in an industrial process includes an optical sensing element 20,600 which includes an optical fiber 10 having a Bragg grating 12 impressed therein which is encased within and fused to at least a portion of a glass capillary tube 20 and/or a large diameter waveguide grating 600 having a core and a wide cladding and which has an outer transverse dimension of at least 0.3 mm. Light 14 is incident on the grating 12 and light 16 is reflected from the grating 12 at a reflection wavelength &lgr;1. The sensing element 20,600 may be used by itself as a sensor or located within a housing 48,60,90,270,300. When external pressure P increases, the grating 12 is compressed and the reflection wavelength &lgr;1 changes. The shape of the sensing element 20,600 may have other geometries, e.g., a “dogbone” shape, so as to enhance the sensitivity of shift in &lgr;1 due to applied external pressure and may be fused to an outer shell 50.

Abstract: A tunable dispersion compensating device includes a grating element in the form of a bulk or large diameter waveguide, having an outer cladding disposed about an inner core. The grating element may be etched, grounded or machined to form a generally “dog bone” shape, wherein the end portions of the grating element has a larger diameter than the center portion disposed therebetween. A chirped grating is written or impressed within the portion of the core disposed in the center portion of the grating element. The center portion is tapered to allow different stresses to be applied along the grating length when the grating element is compressed longitudinally by force F, and thereby vary chirp of the grating to tunably compensate for dispersion.

Abstract: A method of applying a metal coating to optical element, such as an optical waveguide, comprising the steps of partially depleting stabilizers in an electroless metallic solution and immersing an optical waveguide in the electroless metallic solution to deposit the metal coating to the optical waveguide. The step of partially depleting may include creating an electroless metallic solution having a sodium hypophoshite concentration of about 25 grams per liter. The electroless metallic solution may comprise a Fidelity solution 4865A, a Fidelity solution 4865B and de-ionized water in a ratio of 1:1:18; and sodium hypophosphite crystals. Alternatively, the step of partially depleting may include placing a dummy load into the electroless metallic solution. The dummy load may be a rectangular block of metal, formed of a low carbon steel, and may have a threaded cylindrical passage therein.

Abstract: A method is provided for precise and repeatable location of one or more Bragg gratings in a large diameter optical waveguide having a cross-section of at least about 0.3 millimeters, featuring the steps of: defining a reference location on a fixed placement datum arranged on a waveguide fixture device; defining one or more desired locations on a large diameter optical waveguide arranged on the waveguide fixture location in relation to the reference location; and writing one or more Bragg gratings in the large diameter optical waveguide at the one or more desired locations based on the reference location on the fixed placement datum. The step of defining the reference location may include marking the fixed placement datum with a scribe mark thereon; and securing the fixed placement datum in a groove in a waveguide fixture device.

Abstract: In industrial sensing applications at least one parameter of at least one fluid in a pipe 12 is measured using a spatial array of acoustic pressure sensors 14,16,18 placed at predetermined axial locations x1, x2, x3 along the pipe 12. The pressure sensors 14,16,18 provide acoustic pressure signals P1(t), P2(t), P3(t) on lines 20,22,24 which are provided to signal processing logic 60 which determines the speed of sound amix of the fluid (or mixture) in the pipe 12 using acoustic spatial array signal processing techniques with the direction of propagation of the acoustic signals along the longitudinal axis of the pipe 12. Numerous spatial array-processing techniques may be employed to determine the speed of sound amix. The speed of sound amix is provided to logic 48, which calculates the percent composition of the mixture, e.g., water fraction, or any other parameter of the mixture, or fluid, which is related to the sound speed amix. The logic 60 may also determine the Mach number Mx of the fluid.

Abstract: The present invention provides a method for making a multicore large diameter optical waveguide having a cross-section of at least about 0.3 millimeters, two or more inner cores, a cladding surrounding the two or more inner cores, and one or more side holes for reducing the bulk modulus of compressibility and maintaining the anti-buckling strength of the large diameter optical waveguide. The method features the steps of: assembling a preform for drawing a multicore large diameter optical waveguide having a cross-section of at least about 0.3 millimeters, by providing an outer tube having a cross-section of at least about 0.3 millimeters and arranging two or more preform elements in relation to the outer tube; heating the preform; and drawing the large diameter optical waveguide from the heated preform. In one embodiment, the method also includes the step of arranging at least one inner tube inside the outer tube.

Abstract: A tunable optical filter has a large diameter cane waveguide with “side-holes” in the cane cross-section that reduce the force required to compress the large diameter optical waveguide without overly compromising the buckling strength thereof. The large diameter optical waveguide has a cross-section of at least about 0.3 millimeters, including at least one inner core, a Bragg grating arranged therein, a cladding surrounding the inner core, and a structural configuration for providing a reduced bulk modulus of compressibility and maintaining the anti-buckling strength of the large diameter optical waveguide. The structural configuration reduces the cross-sectional area of the large diameter optical waveguide. These side holes reduce the amount of glass that needs to be compressed, but retains the large diameter.

Abstract: The invention provides a pressure transducer having a cane waveguide geometry with “side-holes” in the cane cross-section that reduce the force required to compress the large diameter optical waveguide. The large diameter optical waveguide has a cross-section of at least about 0.3 millimeters, at least one inner core, a Bragg grating arranged therein, a cladding surrounding the inner core, and a structural configuration for providing a reduced bulk modulus of compressibility and maintaining the anti-buckling strength of the large diameter optical waveguide. The structural configuration reduces the cross-sectional area of the large diameter optical waveguide. These side holes reduce the amount of glass that needs to be compressed, but retains the large diameter.

Abstract: The present invention provides a new and unique method for increasing the photosensitivity of a large diameter optical waveguide having a cross-section of at least about 0.3 millimeters. The method features loading the large diameter optical waveguide with a photosensitizing gas at a pressure at least about 4000 pounds per square inch (PSI) at a temperature of at least about 250E Celsius. The photosensitizing gas may be hydrogen, Deuterium or other suitable gas. The method also includes the step of using a particular large diameter optical waveguide having a diameter of greater than 0.9 millimeters. The method may be used as part of a process for writing a Bragg grating in an inner core or a cladding of the large diameter optical waveguide.

Abstract: A method for erasing some or all of at least some of the grating elements of a grating inscribed in an optical waveguide such as an optical fiber or a cane structure (a more rigid optical waveguide), or, more generally, for selectively altering the index of refraction of a span of an optical waveguide, and products provided by the method. A temperature profile suitable for achieving a predetermined desired apodization (shaping of the grating strength) is determined, and then a focused laser beam, from for example a CO2 laser, is directed to a target site on the optical waveguide selected as a suitable point from which to direct the laser beam and so introduce heat into the optical waveguide. The laser beam is held on the target site only so long as is necessary to create at least a portion of the temperature profile.

Abstract: A reconfigurable multifunctional optical device has an optical arrangement for receiving an optical signal, each having optical bands or channels, and a spatial light modulator for reflecting the at least one optical signal provided thereon. The optical arrangement features a free optics configuration with a light dispersion element for spreading each optical signal into one or more respective optical bands or channels for performing separate optical functions on each optical signal. The spatial light modulator includes a micro-mirror device with an array of micro-mirrors, and the respective optical bands or channels reflect off respective micro-mirrors. The free optics configuration includes a common set of optical components for performing each separate optical function on each optical signal. The separate optical functions reflect off separate non-overlapping areas on the spatial light modulator. The separate optical functions include optical switching, conditioning or monitoring functions.

Abstract: A large diameter waveguide is provided having a diameter of at least about 0.3 millimeters, and an outer cladding with an inner core with a long period grating included therein. The long period grating either couples forward propagating cores modes to forward propagating cladding modes of one optical signal travelling in one direction in the large diameter waveguide, or couples forward propagating cladding modes to forward propagating cores modes of another optical signal travelling in another direction in the large diameter waveguide. The long period grating has an optical parameter that changes in response to an application of a compressive force on the optical waveguide. The outer cladding may also have the long period grating written therein. The long period grating has concatenated periodic or aperiodic gratings. The optical waveguide may be shaped like a dogbone structure having wider outer sections and a narrower central section inbetween.