Abstract: A hazard mitigation system to detect an object in a highway-railway grade crossing. A structure is provided that includes a fixed foundation and a surface layer that is cushionably placed above the foundation, such that the structure is located between tracks at the crossing. At least one sensor is mounted between the surface layer and the foundation. This sensor senses the weight of the object upon the surface layer and provides a sensor signal representative of that weight. A control unit receives the sensor signal, processes it to determine whether the object represents a potential hazard, and, if so generates a warning signal. The sensor can particularly include a pressure or strain gage, or a fiber optic sensor. When a fiber optic sensor is employed, it can particularly include a fiber Bragg grating.

Abstract: A hazard mitigation system to detect intrusion by an object into a track zone at a train station platform. A structure is provided that includes a fixed foundation and a surface layer that is cushionably placed above the foundation, such that the structure is located in the track zone. At least one sensor is mounted between the surface layer and the foundation. This sensor senses the weight of the object upon the surface layer and provides a sensor signal representative of that weight. A control unit receives the sensor signal, processes it to determine whether the object represents a potential hazard, and, if so generates a warning signal. The sensor can particularly include a strain or pressure gage, or a fiber optic sensor. When a fiber optic sensor is employed, it can particularly include a fiber Bragg grating.

Abstract: A system for monitoring traffic across a structure. A fiber Bragg grating (FBG) reflects a light wavelength. A mounting mechanism connects the FBG to the structure, such that physical change of the structure changes a stress to the FBG that changes the light wavelength. And optical fiber carries a first light beam to the FBG and carries a second light beam from the FGB. This permits first light beam including the light wavelength to be received from a light source, and permits the first light beam to be altered into the second light beam by passing the light wavelength through the FBG, and permits the second light beam to be provided to a detector to sense the light wavelength present in the second light beam. From this the stress in the structure and information about the traffic across a structure can be inferred.

Abstract: A system for tuning the wavelength of a beam from a tunable laser. A tunable etalon assembly includes a Fabry-Perot etalon with paired reflectors to filter the laser beam. The tunable etalon also includes a thermal unit to thermally adjust the separation of the paired responsive to an etalon tuning signal. A photodetector receives the laser beam after filtering the etalon and generates a detected signal based on intensity. A controller generates the etalon tuning signal, and receives the detected signal and generates a laser tuning signal based on it. Optionally, additional Fabry-Perot etalons, photodetectors, and one or more beamsplitters permit extending wavelength range and determining relative wavelength difference with a beam from a second laser.

Abstract: An a thermal fiber Bragg grating assembly. A platform provides two attachment locations and has a first coefficient of thermal expansion. A stick provides two ends and has a second coefficient of thermal expansion. A fiber Bragg grating provides two ends and has effective third coefficient of thermal expansion. One stick end is fixed to one grating end, the other stick end is fixed to one attachment location, and the other grating end is fixed to the other attachment location. The stick has a same cross-section area along its length that is equal to or less than the cross-section area of the grating. And the coefficients and lengths between respective locations and ends are such that the assembly exhibits an effective overall coefficient of thermal expansion approaching zero.

Abstract: An improved railroad switch monitoring unit of the type that determines whether a mobile rail is brought into a closed state or an open state with respect to a stationary rail. The improvement comprises a fiber Bragg grating (FBG) included in the monitoring unit that is used to determine, based on stress able change in the resonant wavelength of the FBG, whether the mobile rail and the stationary rail are closed or open.

Abstract: A fiber optic track circuit including a light source, a fiber Bragg grating (FBG) unit, and a receiver all connected by optical fiber. The light source provides a light via the optical fiber to the FBG unit. The FBG unit is mountable on a portion of a railway system directly effected by the weight of a passing train, and it receives the light beam and provides a reflected beam to the receiver. The receiver then provides a receiver signal based on the reflected beam. And a processor then determines, based on pre-set criteria and the receiver signal, whether to communicate and what to communicate as a track circuit signal to an external device.

Abstract: A method, apparatus, and system for accident mitigation at a grade crossing of a railway and a highway. One or more gates are selectively horizontally movable to block the highway such that vehicles are blocked from entering the grade crossing, or alternately movable to unblock the highway yet concurrently then block vehicles from exiting the grade crossing onto the railway without impacting at least one gate. Alternately, one or more highway-gates are selectively vertically movable to block or unblock the highway and one or more railway-gates are vertically movable to guard or unguard the railway such that a vehicle cannot exit the grade crossing onto the railway without impacting a railway-gate.

Abstract: A structure analysis and defect detection system in which a laser light source provides light via optical fiber to fiber Bragg gratings that change resonant frequency as stresses change in the structure. Light at the resonant frequencies of the fiber Bragg gratings is reflected and light of other frequencies is passed. The respective reflected light is directed through a Fabry-Perot interference filter or a fiber interferometer and detected by a photodetector. If the Fabry-Perot interference filter is used, the intensity of the reflected light indicates current stress at a fiber Bragg grating. If the fiber interferometer is used, a beat frequency due to heterodyne interference in the light indicates current stress at the respective fiber Bragg grating. Comparison data for the respective characteristic in the detected light over time permits stress analysis, and comparison of such data with pre-determined limit values permits defect or failure detection.

Abstract: A metering module, or a system employing such, for monitoring fluid flow with a laser light source, a light detector and a processor, wherein the fluid may be a gas or liquid. A valve section and a grating section including a fiber Bragg grating (FBG) are provided. The valve section applies strain on the FBG that is representative of the flow of the fluid. An optical fiber couples a probing laser signal to the FBG and the FBG reflects a portion back as a return laser signal that the optical fiber couples to the light detector for detection and processing.

Abstract: A hazard mitigation system to detect an object in a highway-railway grade crossing. A structure is provided that includes a fixed foundation and a surface layer that is cushionably placed above the foundation, such that the structure is located between tracks at the crossing. At least one sensor is mounted between the surface layer and the foundation. This sensor senses the weight of the object upon the surface layer and provides a sensor signal representative of that weight. A control unit receives the sensor signal, processes it to determine whether the object represents a potential hazard, and, if so generates a warning signal. The sensor can particularly include a pressure or strain gage, or a fiber optic sensor. When a fiber optic sensor is employed, it can particularly include a fiber Bragg grating.

Abstract: An a thermal fiber Bragg grating assembly. A platform provides two attachment locations and has a first coefficient of thermal expansion. A stick provides two ends and has a second coefficient of thermal expansion. A fiber Bragg grating provides two ends and has effective third coefficient of thermal expansion. One stick end is fixed to one grating end, the other stick end is fixed to one attachment location, and the other grating end is fixed to the other attachment location. The stick has a same cross-section area along its length that is equal to or less than the cross-section area of the grating. And the coefficients and lengths between respective locations and ends are such that the assembly exhibits an effective overall coefficient of thermal expansion approaching zero.

Abstract: A hazard mitigation system to detect intrusion by an object into a track zone at a train station platform. A structure is provided that includes a fixed foundation and a surface layer that is cushionably placed above the foundation, such that the structure is located in the track zone. At least one sensor is mounted between the surface layer and the foundation. This sensor senses the weight of the object upon the surface layer and provides a sensor signal representative of that weight. A control unit receives the sensor signal, processes it to determine whether the object represents a potential hazard, and, if so generates a warning signal. The sensor can particularly include a strain or pressure gage, or a fiber optic sensor. When a fiber optic sensor is employed, it can particularly include a fiber Bragg grating.

Abstract: A metering module, or a system employing such, for monitoring fluid flow with a laser light source, a light detector and a processor, wherein the fluid may be a gas or liquid. A valve section and a grating section including a fiber Bragg grating (FBG) are provided. The valve section applies strain on the FBG that is representative of the flow of the fluid. An optical fiber couples a probing laser signal to the FBG and the FBG reflects a portion back as a return laser signal that the optical fiber couples to the light detector for detection and processing.

Abstract: Multi-dimensional optical gratings (600, 700) of a background material (602, 702, 802) having a first refractive index and cells (604, 704, 804) of at least one different refractive index. The cells (604, 704, 804) may occupy two-dimensional or three-dimensional grids, defining the optical gratings as planar gratings (600) or cubical gratings (700), and thus providing two or three sets of surface-to-surface separations, or thicknesses, and cell-to-cell separations. The respective sets of surface-to-surface separations and cell-to-cell separations used may particularly be selected according to Bragg's law to selectively scatter respective light wavelengths.

Abstract: A light wavelength meter (10) able to accept light into a light diverter (16) and impart to it a transverse displacement characteristic which can be detected in a light detection unit (20) connected to a processor (22). Optionally, a light diverger (18) may be provided to enhance angular resolution. The light diverter (16) and the light diverger (18) may either transmit or reflect the light. The light diverter (16) may particularly include a diffraction grating (116, 156), Fabry-Perot interferometer (216), multiple slit plate (316), or an acousto-optical unit (416).

Abstract: A light wavelength meter (10) able to accept light into a light diverter (16) and impart to it a transverse displacement characteristic which can be detected in a light detection unit (20) connected to a processor (22). Optionally, a light diverger (18) may be provided to enhance angular resolution. The light diverter (16) and the light diverger (18) may either transmit or reflect the light. The light diverter (16) may include a diffraction grating (116, 156), Fabry-Perot interferometer (216), multiple slit plate (316), or an acousto-optical unit (416). The processor (22) may employ wavelength data look-up tables, including addressed based on light intensity and the first defivative of light intensity.

Abstract: A wavelength reference (10) including at least one gas-tunable etalons (12). Each etalon (12) has first and second reflective surfaces (20,22), making a reflecting surface pair (23). Each reflecting surface pair (23) surrounds a cavity (16) which is filled with a gas-tunable medium (19) having a variable optical index of refraction. The etalons (12) produce equally-spaced spectral lines (4) which are variable in response to changes in the gas-tunable medium (19) such as varying gas pressure or composition. The spectral lines (4) are tuned to align to an external wavelength standard, preferably an ITU reference grid (2). The properties of the gas-tunable medium (19) are then fixed, preferably by sealing an enclosure (14) which surrounds the etalons (12), so that they act as a wavelength reference (10). The etalon (12) can be a reflective etalon (29) or in an alternate embodiment (60), can be a transmissive etalon (29).

Abstract: A multiplexing and de-multiplexing system that may both use the same wavelength division multiplexing (WDM) device. For multiplexing, light sources provide a plurality of light beams having different wavelengths and the WDM forms a single light beam. For de-multiplexing, a light source provides a light beam having a plurality of different light wavelengths and the WDM forms a plurality of output light beams each having respective of the wavelengths. The WDM devices may particularly be formed from optically multi-dimensional planar gratings and cubical gratings which may diffract single wavelengths, sets of wavelengths, and ranges of wavelengths each with respect to one optical dimension present. The gratings may be discrete or integrated in the multiplexing or the de-multiplexing devices. Complex embodiments of the multiplexing system, such as an interleaver, and complex embodiments of the de-multiplexing system, such as a de-interleaver, can be formed using blocks of the gratings.

Abstract: An interference filter (10) and a process (100) by which it may be fabricated. A substrate (12, 52, 82) is provided and a working region (56, 84) is defined therein or thereupon. Relative to the horizontal substrate (12, 52, 82), a plurality of vertical layers having differing refractive index are then constructed by applying material into the working region (56, 84) or altering material already in the working region (56, 84). Photo masking and etching processes may be used to selectively remove material in the working region (56, 84) for applying additional material having a differing refractive index. Photo masking and impurity doping processes may be used to selectively change material to have a differing refractive index.