Abstract: A fiber optic towed array is provided. The array includes a flexible core upon which is disposed a semi-rigid mandrel. The semi-rigid mandrel has a helical groove formed therein, in which is disposed an optical fiber, the optical fiber including a plurality of fiber gratings. The mandrel is in turn covered with a nylon or fiber screen and encased in a layer of open cell foam, which is encased in a protective covering that includes at least one strength member disposed along a longitudinal axis of the array.

Abstract: An encapsulated fiber Bragg grating sensor is provided wherein the EFL of sensor as well as the coefficient of friction between the sensor and the encapsulating tubing is controlled to minimize measurement errors caused by tensile and compressive strains. A method of manufacturing such a sensor is also provided.

Abstract: A system and method for controlling the output of a semiconductor laser is presented. The system and method includes using non-linear equations to calculate a state space model of the laser around an operating point. Adaptive algorithms are calculated and control signals determined using a controller to determine appropriate control laws and cost functions, which are then optimized and used to feed back a control signal to the semiconductor laser to improve the performance and stabilize the output of the laser.

Abstract: A fiber optic towed array is provided. The array includes a flexible core upon which is disposed a semi-rigid mandrel. The semi-rigid mandrel has a helical groove formed therein, in which is disposed an optical fiber, the optical fiber including a plurality of fiber gratings. The mandrel is in turn covered with a nylon or fiber screen and encased in a layer of open cell foam, which is encased in a protective covering that includes at least one strength member disposed along a longitudinal axis of the array.

Abstract: A method for affixing an adjustable optical element in place to allow for tuning an optical device during assembly of the device, but which provides for fixation of the element in place after adjustment.

Abstract: A system and method for deploying an optical fiber within the bore or a well using a linear traction to push the optical fiber, typically encased in a protective sheath, down an instrumentation tube to place an optical fiber sensor at a desired location with the bore of the well.

Abstract: A method for optimizing the architecture of a linear sensor array using WDM-TDM technology and stabilizing the reflectivity spectral profile of the fiber Bragg gratings of the sensors against the influence of environmental factors such as pressure and temperature is provided. The method includes stripping a portion of the foamed coating on the exterior of an optical fiber in the region of the fiber Bragg grating to thin the coating in the region of the grating. After the coating is stripped and the optical fiber cleaned, the area of stripped fiber is recoated with an unvoided plastic.

Abstract: A pressure sensor (100) and system for measuring pressure changes, especially in harsh environments, is described. The pressure sensor has a Fabry-Perot optical cavity formed within a tube (115) with a partial reflective mirror (130) provided by an end of an optical fiber (105) and a reflective mirror (135) provided by an end of a plug (120), with a gap (125) formed between. The pressure sensor may be disposed within a sensing chamber of a housing having an opening into the environment to be monitored. Alternatively, an isolator means may be used to isolate the sensor from the environment while communicating pressure changes to the sensing chamber. In another embodiment, the sensing chamber is filled with a compressible non-flowing material.

Abstract: An array of fiber optic hydrophones or geophones is formed by winding of optical fiber around a continuous, yet flexible cylindrical core. The cylindrical core contains an elastomer filled with a specified percentage of voided plastic microspheres. The elastomer provides the necessary radial support of the optical fiber, and with the included voided microspheres, provides sufficient radial compliance under acoustic pressure for proper operation of the hydrophone. The cylindrical core can be made in very long sections allowing a plurality of fiber optic hydrophones to be wound onto it using a single optical fiber, with individual hydrophone elements separated by integral reflectors such as Fiber Bragg Gratings (FBSs). The center of the core may include a strength member and a central hollow tube for the passing of additional optical fibers. The aforementioned hydrophone array is then packaged within a protective outer coating or coatings as required for the specified application.

Abstract: A mode coupling device is provided for coupling co-propagating modes in an optical waveguide to provide a gain flattening filter for use with an optical amplifier such as an erbium-doped fiber amplifier. The mode coupling device includes a plurality of long period grating sections having equal spatial periods, with adjacent grating sections separated by an interval of less than 10 periods in length. Also provided is a method for manufacturing the mode coupling device, including a method for determining the parameters of the device and a method for fine tuning the device to provide a loss spectrum closely matching the output spectrum of the optical amplifier. The mode coupling device is useful for flattening the gain of the optical amplifier.