Abstract: A sensor system is disclosed, wherein the sensor system provides output data only when the error between a plurality of measured absorption wavelengths of a gas cell and a plurality of known absorption lines for the gas cell is less than or equal to a user-defined error margin.

Abstract: A sensor network having a series arrangement of fiber-coupled, reflective sensors is disclosed. In operation, a first light signal having multiple wavelength bands is launched in an upstream direction on a fiber bus. Each sensor includes a wavelength filter and an FP sensor that is sensitive to a parameter. Each wavelength filter (1) selectively passes a different one of the wavelength bands to its FP sensor and (2) reflects the remaining wavelength bands back into the fiber bus to continue upstream. The FP sensor imprints a signal based on the parameter onto its received light and reflects it as a second light signal. The collimator, wavelength filter, and FP sensor of each sensor are arranged such that each second light signal is returned to the fiber bus, which conveys them in a downstream direction to a processor that measures them and estimates the parameter at each sensor.

Abstract: The current invention relates to optical gages designed to measure strain on the surface of a test specimen. The gages of this invention is designed to be installed and used in a manner similar to conventional electronic foil strain gages, but to have the advantages of an all-optical gage. The gage of this invention is constructed to allow surface strain on the test specimen to be transferred to a length of optical fiber containing a fiber Bragg grating (FBG). As strain is applied to the fiber, the optical spectrum center wavelength reflected by the Bragg grating shifts in wavelength. This shift in wavelength can be converted directly to units of strain. The current invention provides a gage carrier design for use with fiber optic strain sensors comprising one or more FBGs which provide the benefits of a carrier for ease of handling and mounting without degrading gage performance.

Abstract: The invention relates to optical sensor measurement methods that use a swept wavelength optical source to determine wavelength shift as well as to optical sensor systems that embody and employ these methods. A variable scan rate swept optical source is used to determine the optical path length from the optical interrogator to the optical sensors being measured. This data can then be used as desired or needed in implementing the sensor or making sensor measurements. In particular the data can be used in the optical sensor system to compensate for potential measurement errors due to the finite speed of light in the optical medium interconnecting optical sensors under test.

Abstract: The invention relates generally to optical interference filters and interferometers. Methods, devices and device components for fiber Fabry-Perot (FFP) filters and ferrule holders are provided. The invention provides ferrule holders for FFP filters capable of good radial and longitudinal alignment. An exemplary ferrule holder of the present invention is capable of substantially constraining the motion of a pair of ferrules in all directions except a direction parallel to the longitudinal axis, thereby allowing the resonance cavity of a FFP filter to be adjusted while maintaining good radial alignment. The invention further provides temperature compensated ferrule holders and FFP filters that are stable with respect to wavelength drift over a useful range of device operating conditions. In addition, the present invention provides ferrule holders and FFP filters which are particularly useful for monitoring ambient conditions and measuring physical properties and mechanical phenomena.

Abstract: The invention relates to Fabry-Perot interferometers (FFPI) comprising two or more optically coupled tunable all-fiber Fabry-Perot component filters, wherein the Fabry-Perot cavity of the filter is formed within a bare section of optical fiber held within a fiber ferrule. The wavelength transmitted by the interferometer can be tuned thermally or electromechanically for a fiber containing the Fabry-Perot cavity bonded into a groove of a metal substrate. The interferometer can be tuned by changing the length of Fabry-Perot cavity, including by the use of a piezoelectric transducer.

Abstract: Improved fiber Fabry-Perot (FFP) filter configurations are provided in which at least one of the mirror-ended fiber ends forming the FFP has a concave fiber core end. The mirror at that fiber core end is thus concave. The invention provides waferless FFP configurations in which the FFP cavity is an air-gap cavity formed by two highly reflective dielectric mirrors deposited directly on optical fiber ends. The air gap cavity can be tuned using various methods to tune the filter. Use of a concave mirror at the fiber core enables filters with improved performance characteristics: including very wide FSR (>12000 GHz), very high finesse (>5,000), and high glitch-free dynamic range (GFDR) (>40 dB). The invention also provides improved wafer-based FFP fixed and tunable filters that incorporate a concave mirror at a fiber core forming the FFP cavity and a fiber (SMF) waveguide within the cavity.

Abstract: A polarization insensitive tunable optical filter system combines an interference filter or the like with a quarter wave plate and a retro-reflector. The retro-reflector is situated and aligned to intercept light reflected from the filter, and the quarter wave plate is disposed between the filter and the retro-reflector. Hence, the pass signal reflected off the filter a first time passes through the quarter wave plate a first time, reflects off of the retro-reflector, passes through the quarter wave plate a second time, and reflects off of the filter a second time.

Abstract: The invention relates to devices and methods for tuning a fiber grating. A fiber containing a fiber grating is uniformly, precisely and reproducibly bent by first embedding the fiber in a substrate or mounting the fiber on a substrate parallel to the longitudinal (long) axis of the substrate and applying appropriate force to bend the substrate perpendicular to the length of the fiber, i.e., perpendicular to the longitudinal axis of the substrate. Embedding of the fiber carrying the fiber grating parallel to, but offset from the plane containing the central axis which is normal to the bend of the substrate allows bending of the substrate along that central axis of the substrate to achieve enhanced fiber compression or stretching. The fiber grating is tuned preferably by application of force to the substrate to bend the substrate such that the radius of the bend uniformly increases or decreases at least along the length of the fiber grating in the substrate.

Abstract: A method for calibrating tunable optical filters, calibrated tunable filters and devices employing such filters. The method is of particular use with fiber Fabry-Perot tunable filters and more particularly for filters which employ piezoelectric transducers as tuning elements. Sets of calibration coefficients are generated which span the wavelength region and operating temperature range of the filter. Calibrated tunable filters are combined with a means for storing the sets of calibration coefficients and means for correcting wavelength measurements using the sets of coefficients in devices which measure wavelengths of light. The sets of calibration coefficients can also be used to tune the filter to pass a selected wavelength of interest.

Abstract: Swept-wavelength lasers with accurately calibrated wavelength output which can be very rapidly scanned or swept over a selected wavelength band. The invention provides lasers that generate wavelengths in the 1550 nm range that can be swept over about 50 nm. These swept-wavelength lasers are generally useful as accurately calibrated high power light sources. Calibration is achieved by use of a calibrated reference system. Swept-wavelength lasers are particularly useful as components of sensor interrogator systems which determine wavelengths reflected (or transmitted) by Fiber Bragg Gratings (FBG) in sensor arrays. Swept wavelength lasers of this invention are also generally useful for testing of WDM systems, particularly for their applications to current communication systems. the invention provides lasers, interrogator systems and systems for testing WDM components employing the lasers as a calibrated light source.

Abstract: A multi-wavelength reference for use in identifying and measuring wavelengths of radiation from an optical device. The invention provides an interferometer to generate a comb of accurately spaced peaks spanning a selected wavelength range combined with a fiber Bragg grating (FBG) of known Bragg wavelength to generate a peak or notch of known wavelength for use in identifying or marking a peak of the comb. The combination provides an accurate multi-wavelength reference useful in particular with high resolution wavelength scanners, such as tunable FFPI. The invention further provides systems for controlling, and/or compensating for, relative shifts in the wavelengths of the interferometer and the FBG as a function of changing temperature.

Abstract: This invention provides compact, fixed-wavelength and tunable fiber-optic lasers comprising a gain medium, for example a semiconductor, half-cavity VCSEL, or an organic light emitting polymer, within a Fabry-Perot cavity wherein one of the mirrors forming the cavity is a mirror integral with a fiber, for example a mirror (metallic or dielectric, for example) deposited at a fiber end, a reflective tap within an optical fiber, a fiber Bragg Grating (FBG), or a fiber loop mirror. Semiconductor gain material can be bulk semiconductor material or comprise a semiconductor multiple quantum well region. The gain medium itself is not confined to a fiber.

Abstract: The invention provides cascaded Fabry-Perot filters having a plurality of optical fibers within a single F-P cavity. Of particular interest are cascaded FFPs having two, three or four optical fiber paths in the filter. An all-fiber FFP filter has a ferrule assembly having two or more aligned fiber ferrules, each having a plurality of optical fibers bonded into axial bores. Mirrors within the ferrule assembly transverse to the fibers from the F-P cavity. The FP filters can be fixed wavelength or tunable by changing an air gap within the cavity. The invention also provides ferrule holders useful for maintaining alignment of and for tuning the air gap of ferrule assemblies. The holders are particularly useful for construction of cascaded F-P filters.

Abstract: Multiple-cavity fiber optic lasers are fabricated with high-gain fibers in low-loss, high-finesse fiber ferrule resonance cavity configurations supported in low-loss ferrule alignment fixtures developed for use in FFP filters. These lasers incorporate rare-earth doped, sensitized glass fiber as the active medium within FFP cavities. FFP lasers of this invention include those exhibiting single-frequency and/or single-polarization mode operation with wide mode separation. Lasers provided include those with short cavity lengths, where the longest of the cavities of can be less than or equal to about 10 mm in length. These FFP laser sources are fixed-frequency or discretely-tunable. Multiple-cavity configurations in which at least one of the cavities formed contains active fiber are readily formed in fiber ferrule assemblies. FFP lasers can be end-pumped using single- or double-pass pumping configuration or pump resonance cavity configurations.

Abstract: A multi-wavelength reference for use in identifying and measuring wavelengths of radiation from an optical device. The invention provides an interferometer to generate a comb of accurately spaced peaks spanning a selected wavelength range combined with a fiber Bragg grating (FBG) of known Bragg wavelength to generate a peak or notch of known wavelength for use in identifying or marking a peak of the comb. The combination provides an accurate multi-wavelength reference useful in particular with high resolution wavelength scanners, such as tunable FFPI. The invention further provides systems for controlling, and/or compensating for, relative shifts in the wavelengths of the interferometer and the FBG as a function of changing temperature.

Abstract: The invention is a temperature compensating structure for a fiber Bragg grating (FBG) contained in optical fiber. The structure comprises two plates made of materials having different temperature coefficients of expansion and bonded together. The optical fiber is bonded to the exposed surface of the plate having the lower temperature coefficient. The structure bends with changes in temperature and produces an elongation of the fiber with decreasing temperature.

Abstract: A multi-wavelength reference for use in identifying and measuring wave-lengths of radiation from an optical device. The invention provides an interferometer to generate a comb of accurately spaced peaks spanning a selected wavelength range combined with a fiber Bragg grating (FBG) of known Bragg wavelength to generate a peak or notch of known wavelength for use in identifying or marking a peak of the comb. The combination provides an accurate multi-wavelength reference useful in particular with high resolution wavelength scanners, such as tunable FFPI. The invention further provides systems for controlling, and/or compensating for, relative shifts in the wavelengths of the interferometer and the FBG as a function of changing temperature.

Abstract: A reference system for an optical wavelength scanner, used for measuring wavelengths of radiation from an optical device. The system utilizes a wavelength reference comprising a fixed fiber Fabry-Perot (FFP) filter in combination with a reference fiber Bragg grating (FBG) of accurately known wavelength to minimize the effects of drift and nonlinearities in the scanner. The system utilizes dual optical branches, one containing a device or devices which generate, emit or reflect light of a particular wavelength which is to be measured or identified and the other containing the reference. The two branches are periodically illuminated, while the wavelength band is scanned for peaks or notches in light intensity in the illuminated branch. The wavelengths, at which peaks or notches in the light intensity of each branch occur, are logged. The wavelengths of the reference comb of the fixed FFP are determined by reference to that of the reference FBG.

Abstract: This invention relates to temperature compensated FFPs with improved means for alignment of optical fibers. The invention provides ferrule holders with shaped ferrule passageways, as components of FFP alignment fixtures, in which optical fiber ends can be readily aligned using the ferrule rotary alignment method. The ferrule holders have a composite structure facilitating temperature compensation required for applications to PZT-tuned FFPs. The ferrule holder has a core and peripheral region made of materials having different thermal expansion coefficients. The holder core in contact with the ferrule is made of a material having a thermal expansion coefficient substantially matched to that of the ferrule material. In addition, ferrule holders are provided with a means for changing the points of contact between a secured ferrule and its holder which allows wavelength drift as a function of temperature in FFPs to be adjusted.