Abstract: An apparatus for sensing a value of a property in a borehole having hydrogen gas penetrating a subsurface formation includes an optical fiber configured to be disposed in the borehole having the hydrogen gas and comprising a core having a fiber Bragg grating that is responsive to the value of the property and a cladding disposed about the core, wherein (i) the core is doped with a first dopant that is photo-sensitive for writing the fiber Bragg grating and that has a concentration in the core of 2 Mole % or less and (ii) the cladding is doped with a second dopant that lowers an index of refraction of the cladding.

Abstract: A sensing apparatus includes a sheath, a central member disposed in the sheath, at least one optical fiber disposed with the central member, and a film adhesive disposed between the central member and the sheath, the film adhesive provided in one or more sheets or strips and disposed in one or more layers between the central member and the sheath, and the film adhesive attached to the sheath.

Abstract: An embodiment of a method of manufacturing a fiber optic cable includes selecting a cable support structure configured to support an optical fiber sensor, adhering the optical fiber sensor to the cable support structure by applying a temporary adhesive, and installing a protective layer around the cable support structure and the temporarily adhered optical fiber sensor. The method further includes removing a bond between the optical fiber sensor and the temporary adhesive, wherein removing the bond includes injecting a debonding material into a space formed between the cable support structure and the protective layer, and injecting a permanent adhesive into the space, the permanent adhesive configured to immobilize the optical fiber sensor relative to the protective layer and allow strain to be transferred from the protective layer to the optical fiber sensor.

Abstract: An embodiment of a method of manufacturing a fiber optic cable includes selecting a cable support structure configured to support an optical fiber sensor, adhering the optical fiber sensor to the cable support structure by applying a temporary adhesive, and installing a protective layer around the cable support structure and the temporarily adhered optical fiber sensor. The method further includes removing a bond between the optical fiber sensor and the temporary adhesive, wherein removing the bond includes injecting a debonding material into a space formed between the cable support structure and the protective layer, and injecting a permanent adhesive into the space, the permanent adhesive configured to immobilize the optical fiber sensor relative to the protective layer and allow strain to be transferred from the protective layer to the optical fiber sensor.

Abstract: A sensing apparatus includes a sheath, a central member disposed in the sheath, at least one optical fiber disposed with the central member, and a film adhesive disposed between the central member and the sheath, the film adhesive provided in one or more sheets or strips and disposed in one or more layers between the central member and the sheath, and the film adhesive attached to the sheath.

Abstract: A temperature sensing arrangement includes a member having a first coefficient of thermal expansion, and an optical fiber having a second coefficient of thermal expansion. The optical fiber is strain transmissively mounted to the member. And the first coefficient of thermal expansion is greater than the second coefficient of thermal expansion such that strain measurable in the optical fiber is correlatable to temperature changes in the member.

Abstract: A method of measuring acoustic energy impinging upon a cable includes, interrogating at least one optical fiber of the cable with electromagnetic energy, the at least one optical fiber is nonconcentrically surrounded by and strain locked to a sheath of the cable, monitoring electromagnetic energy returned in the at least one optical fiber, and determining acoustic energy impinging on the cable.

Abstract: An apparatus for estimating a parameter includes: an optical fiber sensor including at least one optical fiber configured to be disposed in a downhole location and including at least one sensing location configured to generate measurement signals; at least one light source configured to transmit a measurement signal having a wavelength to interrogate a sensing location and cause the sensing location to return a reflected measurement signal indicative of a measured parameter, and configured to transmit a reference signal and cause a reflected reference signal to be returned from a location associated with the sensing location, the reflected reference signal having a known relationship to hydrogen concentration; and a processor configured to receive the reflected measurement signal and the reflected reference signal, estimate the hydrogen concentration based on the reflected reference signal, and calibrate the first reflected signal based on the estimated hydrogen concentration.

Abstract: A method of measuring acoustic energy impinging upon a cable includes, interrogating at least one optical fiber of the cable with electromagnetic energy, the at least one optical fiber is nonconcentrically surrounded by and strain locked to a sheath of the cable, monitoring electromagnetic energy returned in the at least one optical fiber, and determining acoustic energy impinging on the cable.

Abstract: A fiber optic cable arrangement includes a core, a sheath surrounding the core and being strain locked to the core, and at least one optical fiber positioned within the sheath being strain locked to the core.

Abstract: An embodiment of a method of manufacturing a fiber optic cable includes selecting a cable support structure configured to support an optical fiber sensor, adhering the optical fiber sensor to the cable support structure by applying a temporary adhesive, and installing a protective layer around the cable support structure and the temporarily adhered optical fiber sensor. The method further includes removing a bond between the optical fiber sensor and the temporary adhesive, wherein removing the bond includes injecting a debonding material into a space formed between the cable support structure and the protective layer, and injecting a permanent adhesive into the space, the permanent adhesive configured to immobilize the optical fiber sensor relative to the protective layer and allow strain to be transferred from the protective layer to the optical fiber sensor.

Abstract: A twisted, multicore fiber communicates light input to each core to an output. The twisting mitigates relative time delays of the input light traveling through each of the cores in the multicore fiber to the output caused by bending of that multicore fiber. An example application is in an optical network that includes an optical input terminal and an optical sensor connected by a twisted multicore connecting fiber. One example of twisted multicore optical fiber is helically-wrapped, multicore fiber.

Abstract: An optical cable includes an outer tubing. At least one optical fiber disposed within the outer tubing. A stiffening member configured to bend with bending of the outer tubing; wherein the stiffening member shifts a neutral plane of the cable away from the at least one optical fiber. Also included is a method of increasing a bending sensitivity in an optical cable.

Abstract: A distributed sensing apparatus and system including one or more optical fibers disposed in a channel on the surface of a central member. A layer of film adhesive is disposed between the central member and a sheath. The film adhesive is circumferentially wrapped around the central member prior to arranging the sheath around the central member. The film adhesive is then cured and expanded to firmly attach the optical fiber to the sheath.

Abstract: An optical cable includes an outer tubing. At least one optical fiber disposed within the outer tubing. A stiffening member configured to bend with bending of the outer tubing; wherein the stiffening member shifts a neutral plane of the cable away from the at least one optical fiber. Also included is a method of increasing a bending sensitivity in an optical cable.

Abstract: An apparatus for estimating a parameter includes: an optical fiber sensor including at least one optical fiber configured to be disposed in a downhole location and including at least one sensing location configured to generate measurement signals; at least one light source configured to transmit a measurement signal having a wavelength to interrogate a sensing location and cause the sensing location to return a reflected measurement signal indicative of a measured parameter, and configured to transmit a reference signal and cause a reflected reference signal to be returned from a location associated with the sensing location, the reflected reference signal having a known relationship to hydrogen concentration; and a processor configured to receive the reflected measurement signal and the reflected reference signal, estimate the hydrogen concentration based on the reflected reference signal, and calibrate the first reflected signal based on the estimated hydrogen concentration.

Abstract: A method and structure for terminating an optical fiber are disclosed that provide an optical fiber termination structure with a small volume and very low return loss, even when the termination is in close proximity to reflective surfaces. In one example embodiment, the optical fiber termination reduces reflections into the one or more cores to a return loss of ?70 dB or less regardless of the presence of surfaces proximate the optical fiber termination. At the same time, a length of the optical fiber termination is less than 5 mm and a largest transverse dimension of the optical fiber termination is less than 325 um. The optical fiber termination is useful in fiber sensing applications in general and is particularly effective for terminating a multi-core fiber used in a distributed shape sensing application.

Abstract: A temperature sensing arrangement includes a member having a first coefficient of thermal expansion, and an optical fiber having a second coefficient of thermal expansion. The optical fiber is strain transmissively mounted to the member. And the second coefficient of thermal expansion is greater than the first coefficient of thermal expansion such that strain measurable in the optical fiber is correlatable to temperature changes in the member.

Abstract: An apparatus for estimating at least one parameter in a downhole environment includes: an optical fiber configured to be disposed in a borehole, the optical fiber including a core having a first index of refraction and a cladding surrounding the core and having a second index of refraction that is lower than the first index of refraction, at least a portion of the core being made from a hydrogen resistant material; at least one fiber Bragg grating (FBG) formed within the hydrogen resistant material; a light source configured to send an optical signal into the optical fiber; and a detector configured to receive a return signal generated by the at least one FBG and generate data representative of the at least one parameter.

Abstract: Systems and methods for monitoring signals in an optical fiber amplifier system are provided. The optical amplifier system includes a tapered fiber bundle which couples optical energy into the cladding of an optical amplifier. A signal passing through the optical amplifier is amplified. To monitor the amplified signal, a single fiber of a tapered fiber bundle may be used as a monitor fiber. Alternatively, a monitor or coupler may be integrated into the tapered fiber bundle during manufacturing. The systems and methods disclosed allow for monitoring the amplified signal without increasing the length of the amplified signal's path, thus minimizing the introduction of additional non-linearities.