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: 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: The invention relates to Fabry-Perot interferometers (FFPI) that are thermally or electromechanically tunable. These interferometers are particularly useful as components of optical filters which can be tuned by coordinated tuning of the component filters. The tunble FFPI of this invention can be made by fiber bonding or fusion techniques and as a result, are relatively low cost devices.

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: 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: 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.

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.

Abstract: Compact, fixed-wavelength and tunable fiber optic lasers combine a sub-millimeter length of high-gain rare-earth-doped, sensitized glass fiber within a fiber Fabry-Perot (FFP) cavity. Tunable, single-frequency fiber lasers at 1535 nm employing high-gain erbium:ytterbium phosphate glass fiber are specifically provided. Single-frequency and/or single-polarization mode erbium:ytterbium glass fiber lasers, having cavity lengths less than about 200 .mu.m with continuous wavelength tuning range over several nanometers are provided. Amplified single-frequency lasers incorporating fiber rare-earth ion optical amplifiers are also provided. Single-frequency lasing employing sub-millimeter lengths of rare-earth doped sensitized fiber in a 3 mirror laser design is also demonstrated.

Abstract: Improved ferrule alignment fixtures for use in fiber Fabry-Perot (FFP) filters are provided. The inventive alignment fixtures have ferrule holders with shaped passageways for holding fiber-containing ferrules in three-point contact which allow fiber alignment using a rotary alignment technique.The FFPs have a fiber ferrule assembly which when aligned in the inventive ferrule holder forms an optical cavity between mirrors transverse to the fiber in the ferrule assembly. Wavelength tunable FFPs have a piezoelectric transducer interposed between the ferrule holders which can be used to change the length of the optical cavity and tune the filter.

Abstract: Temperature compensated Fiber Fabry Perot filters are provided. These filters display minimal wavelength drift over a wide range of temperatures. The temperature coefficients of the filters can be adjusted after construction. These FFPs are particularly useful in applications in which filter size is a constraint. The disclosed filter designs can be employed for minaturized filters which retain thermal and optical stability over a wide range of temperatures. In particular, low-loss thermally stable FFPs suitable for use in circuit board applications are provided.

Abstract: The present invention provides fiber Fabry-Perot filters having an adjustable temperature coefficient. Passive means and adjustable means for changing the temperature coefficients of FFPs are provided. These means allow adjustment of the temperature coefficient of the filter to minimize wavelength (or frequency) drift as a function of temperature. The means for temperature coefficient adjustment described herein are particularly useful in combination with electronic means for changing the cavity length, such as piezoelectric transducer elements. Controlling the thicknesses of epoxy used to attach PZTs in the filter fixture has been found to lead to improved reproducibility of passive temperature compensation. An adjustable means for changing the temperature coefficient of a FFP after its construction by varying the points of contact between the filter ferrules and the filter fixture is also provided.