Abstract: A Bragg Grating optical waveguide laser source comprising at least one Bragg grating in a rare earth doped waveguide and an optical pump source coupled to said doped waveguide, said Bragg gratings having at least two different peak reflection wavelengths and at least one of said Bragg gratings comprising a phase-shift and a phase-shift actuator being coupled to the phase-shift for controlled application of changes in the phase-shift thus activating or deactivating the corresponding Bragg grating waveguide laser.

Abstract: Fibre optic apparatus for accurate and repeatable measurements of light comprising one or more wavelength ranges, and system employing the apparatus. The apparatus according to the invention comprises: a directional coupler adapted to lead the light into an optical fibre, said optical fibre containing at least one analysis filter for each wavelength range, said analysis filters consisting of at least one fibre-optical Bragg-grating (FBG) which reflects incident light with a chosen wavelength back through said directional coupler and onto a detector having an associated signal processing unit, a modulator device for pulsing the incident light with a chosen pulse width, and an optical fibre delay line in front of each analysis filter, with a length adapted to provide for a sufficient time delay larger than the pulse width, so that the pulses reflected from each analysis filter at different wavelengths can be separated in time and thereby be demodulated in the signal processing unit.

Abstract: A fiber optic sensor system comprises at least one measuring sensor 1 providing an optical output dependent upon one or more parameters to be measured, e.g. temperature, and at least one reference sensor 2 providing a reference output for comparison with the measuring sensor output. The reference sensor is provided in a birefringent fiber.

Abstract: A Bragg Grating optical waveguide laser source comprising at least one Bragg grating in a rare earth doped waveguide and an optical pump source coupled to said doped waveguide, said Bragg gratings having at least two different peak reflection wavelengths and at least one of said Bragg gratings comprising a phase-shift and a phase-shift actuator being coupled to the phase-shift for controlled application of changes in the phase-shift thus activating or deactivating the corresponding Bragg grating waveguide laser.

Abstract: A body compatible fiber optic sensor probe is provided. The probe includes at least one optical fiber and the fiber or fibers include at least one sensing region adapted and arranged such that the probe has simultaneously measurable respective optical properties that are responsive to respective different parameters within the body, such properties being dependent upon mechanical strain established in the fiber or fibers in response to said parameters. Such a probe is suitable for invasive medical use.

Abstract: A body compatible fiber optic sensor probe for invasive medical use is provided. The probe includes at least one sensing location at which the fiber is configured to provide at least one detectable changeable optical property responsive to strain within the fiber, and at least one sensing element which undergoes a volumetric change in response to an in body parameter to be sensed. The sensing element is coupled to the fiber in such a way that the volumetric change induces strain within the fiber so as to vary the detectable optical property or properties.

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 device for accurate and repeatable measurements of optical wavelengths, including an interrogation broadband light source (1) and a tuneable optical filter (2). A first part of the light is, in either order, transmitted through the filter (2) and reflected from, or transmitted through, at least one fibre Bragg grating (5) with known Bragg wavelength, providing an absolute wavelength reference, and directed to a first detector (7). A second part of the light is, in either order, transmitted through the filter and transmitted through, or reflected from a Fabry-Perot filter (8) with fixed and known free spectral range, creating a comb spectrum sampling the interrogation source spectrum to provide an accurate frequency/wavelength scale.

Abstract: An optical end-pumped fiber laser doped with one or more rare-earths and with distributed feedback (DFB) via a fiber Bragg-grating, which is oscillating on two orthogonally polarized wavelengths. The distance between the wavelengths may be tuned by changing the birefringence of the fiber. The laser may be applied as a polarimetric sensor in which an asymmetrical force changes the wavelength separation, or as a tunable two-wavelength source. A particular preferred field of application is for measuring the pressure in pipes, to determine the flow.

Abstract: An optical fibre distributed feedback laser comprises an amplifying optical fibre (50) operable to provide optical gain at a lasing wavelength, in which a diffraction grating (30) is disposed on at least a portion of the amplifying optical fibre to provide distributed optical feedback for sustaining lasing action at the lasing wavelength.

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.