Abstract: The present invention provides an optical fiber providing high photosensitivity in the absence of hydrogen loading as well as a low numerical aperture. One aspect of the present invention relates to an optical fiber including a core, the core comprising silica doped with at least about 6 mol % germania and at least about 0.9 wt % fluorine; and a cladding surrounding the core. The optical fiber of the present invention is suitable for the production of fiber Bragg gratings.

Abstract: The present invention provides an optical fiber providing high photosensitivity in the absence of hydrogen loading as well as a low numerical aperture. One aspect of the present invention relates to an optical fiber including a core, the core comprising silica doped with at least about 6 mol % germania and at least about 0.9 wt % fluorine; and a cladding surrounding the core. The optical fiber of the present invention is suitable for the production of fiber Bragg gratings.

Abstract: A method of fabricating a chirped optical fibre grating so that the grating has a predetermined desired wavelength-dependent response across an operational bandwidth comprises apodising the grating so that a degree of apodisation at a longitudinal position along the grating corresponds to the desired response at the optical wavelength reflected at that longitudinal position along the grating.

Abstract: A superluminescent source emits a wide-band light beam, that is frequency modulated by a filter with a pass band centred on a frequency that is made to vary according to a predetermined law so as to frequency modulate the light beam. Means for splitting and recombining beams determine a mutual phase shift between two components of the beam that depends on the physical magnitude to be measured and is detected by a detector as an indication of the value of the magnitude itself.

Abstract: In a laser apparatus for measuring the velocity of a fluid, a measurement laser light beam (M) fed into the fluid and scattered by a particle within the fluid is made to interfere with a reference laser light beam (R) to generate an interference signal based on the velocity of the particle; the apparatus comprises a low-coherence laser source (10) and interferometric means (11, 12) which split the light beam of the laser source (10) into the stated reference light beam (R) and measurement light beam (M), and cause the reference light beam (R) derived from the laser source (10) to interfere with the backscattered component resulting from the scattering of the measurement light beam (M).

Abstract: In a polarimetric fibre-optic sensor using a polarization-maintaining optical fibre with two light propagation modes, a reference light signal is fed to propagate along the optical fibre in accordance with one propagation mode, a series of measurement light signals being induced by a series of optical fibre deformation elements, to propagate along the optical fibre in accordance with the other propagation mode, each being unbalanced in time with respect to the reference light signal by an amount which is different from that of the other measurement light signals; by using particular interferometric techniques, compensating the unbalances and analyzing the signals resulting from the interference between the measurement light signals and the reference light signal it is possible to determine and locate a physical phenomenon which disturbs the optical fibre.