Abstract: Methods and apparatus enable monitoring conditions in a well-bore using multiple cane-based sensors. The apparatus includes an array of cane-based Bragg grating sensors located in a single conduit for use in the well-bore. For some embodiments, each sensor is located at a different linear location along the conduit allowing for increased monitoring locations along the conduit.

Abstract: Methods and apparatus for the active control of a wavelength-swept light source used to interrogate optical elements having characteristic wavelengths distributed across a wavelength range are provided.

Abstract: An optical fiber feedthrough assembly includes a glass plug disposed in a recess of a feedthrough housing. The glass plug may define a large-diameter, cane-based, waveguide sealed within the recess in the housing and providing optical communication through the housing. Sealing occurs with respect to the housing at or around the glass plug of an optical waveguide element passing through the housing by braze sealing to the glass plug and/or embedding the glass plug in a polymer bonded with the plug to form a molded body that is sealed in the housing by, for example, compression mounting of the molded body or providing a sealing element around the molded body.

Abstract: An optical fiber feedthrough assembly includes a glass plug disposed in a recess of a feedthrough housing. The glass plug may define a large-diameter, cane-based, waveguide sealed within the recess in the housing and providing optical communication through the housing. Sealing occurs with respect to the housing at or around the glass plug of an optical waveguide element passing through the housing by braze sealing to the glass plug and/or embedding the glass plug in a polymer bonded with the plug to form a molded body that is sealed in the housing by, for example, compression mounting of the molded body or providing a sealing element around the molded body.

Abstract: An optical fiber feedthrough assembly includes a glass plug disposed in a recess of a feedthrough housing. The glass plug may define a large-diameter, cane-based, waveguide sealed within the recess in the housing and providing optical communication through the housing. Sealing occurs with respect to the housing at or around the glass plug of an optical waveguide element passing through the housing by braze sealing to the glass plug and/or embedding the glass plug in a polymer bonded with the plug to form a molded body that is sealed in the housing by, for example, compression mounting of the molded body or providing a sealing element around the molded body.

Abstract: Methods and apparatus for discrete point temperature sensing include a temperature sensor that can be part of an array of temperature sensors for location in a wellbore. A single unitary ribbon-like structure can form the temperature sensor that has separate optical cores possessing different characteristics such that one core is unique from another core. Each core has a reflective grating disposed therein such that the wavelength of light reflected by the gratings is in response to temperature and any strain applied to the sensor from a surrounding environment. For some embodiments, the responses to strain from each of the gratings are similar while the responses from each of the gratings to temperature are dissimilar due to the different characteristics of the cores. These responses provided separately by each grating therefore enable compensation for strain in order to provide an accurate temperature measurement at the sensor.

Abstract: An optical fiber feedthrough assembly includes a glass plug disposed in a recess of a feedthrough housing. The glass plug may define a large-diameter, cane-based, waveguide sealed within the recess in the housing and providing optical communication through the housing. Sealing occurs with respect to the housing at or around the glass plug of an optical waveguide element passing through the housing by braze sealing to the glass plug and/or embedding the glass plug in a polymer bonded with the plug to form a molded body that is sealed in the housing by, for example, compression mounting of the molded body or providing a sealing element around the molded body.

Abstract: An optical fiber feedthrough assembly includes a glass plug disposed in a recess of a feedthrough housing. The glass plug may define a large-diameter, cane-based, waveguide sealed within the recess in the housing and providing optical communication through the housing. Sealing occurs with respect to the housing at or around the glass plug of an optical waveguide element passing through the housing by braze sealing to the glass plug and/or embedding the glass plug in a polymer bonded with the plug to form a molded body that is sealed in the housing by, for example, compression mounting of the molded body or providing a sealing element around the molded body.

Abstract: Methods and apparatus for discrete point temperature sensing include a temperature sensor that can be part of an array of temperature sensors for location in a wellbore. A single unitary ribbon-like structure can form the temperature sensor that has separate optical cores possessing different characteristics such that one core is unique from another core. Each core has a reflective grating disposed therein such that the wavelength of light reflected by the gratings is in response to temperature and any strain applied to the sensor from a surrounding environment. For some embodiments, the responses to strain from each of the gratings are similar while the responses from each of the gratings to temperature are dissimilar due to the different characteristics of the cores. These responses provided separately by each grating therefore enable compensation for strain in order to provide an accurate temperature measurement at the sensor.

Abstract: Methods and apparatus allowing distributed temperature sensing (DTS) measurements to be compensated for differential and/or varying loss between Raman Stokes and anti-Stokes signals are provided. By irradiating an optical waveguide with signals at wavelengths at or near the Raman Stokes and anti-Stokes bands, a distributed loss profile for the waveguide may be generated. This distributed loss profile may be used to adjust the amplitudes or amplitude ratios of Raman Stokes and anti-Stokes signals used in DTS measurements, which may lead to more accurate DTS profiles.

Abstract: A method and apparatus sense attributes of reflected signals in an optical sensing system. In one embodiment, a method for sensing in an optical sensing system comprising an interrogator coupled to a Bragg grating sensor by an optical cable includes the steps of producing a first optical signal, coupling the first optical signal to an optical cable, receiving a first reflected signal from a Bragg grating sensor within the optical cable, resolving a wavelength of first reflected signal, producing a second optical signal, coupling the second optical signal to the optical cable, receiving a second reflected signal caused by Brillouin backscattering within the optical cable, and resolving a difference in frequencies between the second optical signal and second reflected signal. Embodiments of the method and apparatus are particularly useful for sensing temperature and strain in hazardous locations such as down hole gas and oil field applications and the like.

Abstract: Methods and apparatus enable compensation of source light wavelength fluctuations due to instability of a broadband source within an optical sensing system. Tapping off two or more portions of the light output from the source at specific wavelength bands enables power based measurements of these portions. The measurements provide compensation ability by either use as feedback to control the source or for determination of the central wavelength so that adjustments can be applied to sensor response signals received at a receiver.

Abstract: Methods and apparatus for discrete point temperature sensing include a temperature sensor that can be part of an array of temperature sensors for location in a wellbore. A single unitary ribbon-like structure can form the temperature sensor that has separate optical cores possessing different characteristics such that one core is unique from another core. Each core has a reflective grating disposed therein such that the wavelength of light reflected by the gratings is in response to temperature and any strain applied to the sensor from a surrounding environment. For some embodiments, the responses to strain from each of the gratings are similar while the responses from each of the gratings to temperature are dissimilar due to the different characteristics of the cores. These responses provided separately by each grating therefore enable compensation for strain in order to provide an accurate temperature measurement at the sensor.

Abstract: Methods and apparatus enable compensation of source light wavelength fluctuations due to instability of a broadband source within an optical sensing system. Tapping off two or more portions of the light output from the source at specific wavelength bands enables power based measurements of these portions. The measurements provide compensation ability by either use as feedback to control the source or for determination of the central wavelength so that adjustments can be applied to sensor response signals received at a receiver.

Abstract: A method and apparatus for mitigating the effects of polarization on wavelength determinations is disclosed. An optical source produces light across an optical spectrum, while a polarization element changes the polarization of the light at a first rate. The resulting light is applied to an optical element that produces a spectral response with a feature of interest from the polarization changed light. The optical element and the polarization element are such that the bandwidth of the feature of interest of the optical element is significantly greater than the first rate. A receiver network produces received signals from the received spectrum; and a data processing unit calculates a wavelength that is insensitive to ripple in the received signal and/or the received signals are low-pass filtered to reduce the ripple resulting from the polarization change.

Abstract: An optical fiber feedthrough assembly includes a glass plug disposed in a recess of a feedthrough housing. The glass plug may define a large-diameter, cane-based, waveguide sealed within the recess in the housing and providing optical communication through the housing. Sealing occurs with respect to the housing at or around the glass plug of an optical waveguide element passing through the housing by braze sealing to the glass plug and/or embedding the glass plug in a polymer bonded with the plug to form a molded body that is sealed in the housing by, for example, compression mounting of the molded body or providing a sealing element around the molded body.

Abstract: Methods and apparatus enable monitoring conditions in a well-bore using multiple cane-based sensors. The apparatus includes an array of cane-based Bragg grating sensors located in a single conduit for use in the well-bore. For some embodiments, each sensor is located at a different linear location along the conduit allowing for increased monitoring locations along the conduit.

Abstract: Methods and apparatus for discrete point temperature sensing include a temperature sensor that can be part of an array of temperature sensors for location in a wellbore. A single unitary ribbon-like structure can form the temperature sensor that has separate optical cores possessing different characteristics such that one core is unique from another core. Each core has a reflective grating disposed therein such that the wavelength of light reflected by the gratings is in response to temperature and any strain applied to the sensor from a surrounding environment. For some embodiments, the responses to strain from each of the gratings are similar while the responses from each of the gratings to temperature are dissimilar due to the different characteristics of the cores. These responses provided separately by each grating therefore enable compensation for strain in order to provide an accurate temperature measurement at the sensor.

Abstract: Methods and apparatus enable monitoring conditions in a well-bore using multiple cane-based sensors. The apparatus includes an array of cane-based Bragg grating sensors located in a single conduit for use in the well-bore. For some embodiments, each sensor is located at a different linear location along the conduit allowing for increased monitoring locations along the conduit.

Abstract: Methods and apparatus for the active control of a wavelength-swept light source used to interrogate optical elements having characteristic wavelengths distributed across a wavelength range are provided.