Abstract: A method of controlling an external-cavity tuneable laser which has a wavelength-elective tuneable mirror, in which wavelength selectivity is achieved by an electrical signal provided by an alternating voltage. The tuneable mirror has a liquid crystal material, a diffraction grating and a planar waveguide optically interacting with the grating. The diffraction grating and the waveguide form a resonant structure that reflects only a selected resonance wavelength from among all the other wavelengths impinging thereon. Depending on the amplitude of the voltage applied to the tunable mirror, the tuneable mirror reflects radiation only at a given wavelength. The lasing output wavelength of the laser is selected to correspond to the resonance wavelength of the tuneable mirror. Accurate selection of the emission wavelength (frequency) of the tuneable laser by the tuneable mirror can be derived from the analysis of the signal modulation induced by the AC voltage applied to the tuneable mirror.

Abstract: A single-mode external-cavity tuneable laser includes a gain medium, a tuneable element and a channel allocation grid element. The channel allocation grid element is preferably an FP etalon which is structured and configured to define a plurality of equally spaced transmission peaks corresponding to the ITU channel grid, e.g., 200, 100, 50 or 25 GHz. The tuneable element, preferably a tuneable mirror, serves as the coarse tuning element that discriminates between the peaks of the grid etalon. The tuneable laser of the invention has a relatively short cavity length of not more than 15 mm, preferably not larger than 12 mm. It has been found that the FP etalon introduces a phase non-linearity in the external cavity, which induces a compression of the cavity modes, i.e., a reduction in the cavity mode spacing, in correspondence to the etalon transmission peaks. Mode compression increases with the decrease of the FWHM bandwidth of the grid FP etalon, hereafter referred to as (FWHM)FP.

Abstract: A method of controlling an external-cavity tuneable laser which has a wavelength-elective tuneable mirror, in which wavelength selectivity is achieved by an electrical signal provided by an alternating voltage. The tuneable mirror has a liquid crystal material, a diffraction grating and a planar waveguide optically interacting with the grating. The diffraction grating and the waveguide form a resonant structure that reflects only a selected resonance wavelength from among all the other wavelengths impinging thereon. Depending on the amplitude of the voltage applied to the tunable mirror, the tuneable mirror reflects radiation only at a given wavelength. The lasing output wavelength of the laser is selected to correspond to the resonance wavelength of the tuneable mirror. Accurate selection of the emission wavelength (frequency) of the tuneable laser by the tuneable mirror can be derived from the analysis of the signal modulation induced by the AC voltage applied to the tuneable mirror.

Abstract: A single-mode external-cavity tuneable laser includes a gain medium, a tuneable element and a channel allocation grid element. The channel allocation grid element is preferably an FP etalon which is structured and configured to define a plurality of equally spaced transmission peaks corresponding to the ITU channel grid, e.g., 200, 100, 50 or 25 GHz. The tuneable element, preferably a tuneable mirror, serves as the coarse tuning element that discriminates between the peaks of the grid etalon. The tuneable laser of the invention has a relatively short cavity length of not more than 15 mm, preferably not larger than 12 mm. It has been found that the FP etalon introduces a phase non-linearity in the external cavity, which induces a compression of the cavity modes, i.e., a reduction in the cavity mode spacing, in correspondence to the etalon transmission peaks. Mode compression increases with the decrease of the FWHM bandwidth of the grid FP etalon, hereafter referred to as (FWHM)FP.

Abstract: Optical pumping unit comprising a first pump source adapted to emit a first pump radiation at wavelength ?p1; a second pump source adapted to emit a second pump radiation at wavelength ?p2, with wavelength ?p2 different from wavelength ?p1; and a common coupling section comprising a first and a second port connected to the first and second pump source for respectively receiving the first and the second pump radiation; a third port for a signal radiation at wavelength ?s; a fourth port, wherein the coupling section is adapted to combine, in the fourth port, the signal radiation and the first and second pump radiation through a reversal of the direction of propagation of the first pump radiation from the first port to the fourth port.

Abstract: Optical pumping unit comprising a first pump source adapted to emit a first pump radiation at wavelength ?p1; a second pump source adapted to emit a second pump radiation at wavelength ?p2, with wavelength ?p2 different from wavelength ?p1; and a common coupling section comprising a first and a second port connected to the first and second pump source for respectively receiving the first and the second pump radiation; a third port for a signal radiation at wavelength ?s; a fourth port, wherein the coupling section is adapted to combine, in the fourth port, the signal radiation and the first and second pump radiation through a reversal of the direction of propagation of the first pump radiation from the first port to the fourth port.

Abstract: A method of making an all-fiber Mach-Zehnder interferometer comprising at least two optical fibers comprises the steps of bringing the fibers in a reciprocal contact relationship for a contact section thereof; fusing together and tapering the fibers in at least a first portion of said contact section; forming at least two optical couplers between the fibers in a second and a third portions of said contact section, located at opposite sides of said first portion.

Abstract: A fused optical coupler comprising a polarization maintaining fiber and a standard fiber is provided. The cross-section of the said standard fiber is smaller than the cross-section of the polarization maintaining fiber in the area of fusion of the coupler. The internal forces in the coupling area are sufficiently low to provide an extinction ratio of more than 20 dB at the output of the polarization maintaining fiber.

Abstract: Optical pumping unit comprising a first pump source adapted to emit a first pump radiation at wavelength &lgr;p1; a second pump source adapted to emit a second pump radiation at wavelength &lgr;p2, with wavelength &lgr;p2 different from wavelength &lgr;p1; and a common coupling section comprising a first and a second port connected to the first and second pump source for respectively receiving the first and the second pump radiation; a third port for a signal radiation at wavelength &lgr;s; a fourth port, wherein the coupling section is adapted to combine, in the fourth port, the signal radiation and the first and second pump radiation through a reversal of the direction of propagation of the first pump radiation from the first port to the fourth port.

Abstract: Device for locking the wavelength of an optical signal emitted by a source, comprising: a coupler (2) capable of extracting a fraction of the said optical signal, a splitter (4) capable of dividing the said fraction of the said optical signal into a first sub-fraction and a second sub-fraction, a first filter (FP1) capable of filtering the said first sub-fraction and of generating an optical signal when its wavelength is displaced to values below the wavelength of the optical signal to be locked, a second filter (FP2) capable of filtering the said second sub-fraction and of generating an optical signal when its wavelength is displaced to values above the wavelength of the optical signal to be locked, an opto-electronic device (6) capable of converting the said first filtered sub-fraction of the optical signal and the said second filtered sub-fraction of the optical signal, and of generating a signal corresponding to the said size of the displacement and a signal identifying the direction of the said displacem

Abstract: Optical pumping unit comprising a first pump source adapted to emit a first pump radiation at wavelength &lgr;p1; a second pump source adapted to emit a second pump radiation at wavelength &lgr;p2, with wavelength &lgr;p2 different from wavelength &lgr;p1; and a common coupling section comprising a first and a second port connected to the first and second pump source for respectively receiving the first and the second pump radiation; a third port for a signal radiation at wavelength &lgr;s; a fourth port, wherein the coupling section is adapted to combine, in the fourth port, the signal radiation and the first and second pump radiation through a reversal of the direction of propagation of the first pump radiation from the first port to the fourth port.

Abstract: A method of making an all-fiber Mach-Zehnder interferometer comprising at least two optical fibers comprises the steps of bringing the fibers in a reciprocal contact relationship for a contact section thereof; fusing together and tapering the fibers in at least a first portion of said contact section; forming at least two optical couplers between the fibers in a second and a third portions of said contact section, located at opposite sides of said first portion.

Abstract: Splice between a first optical fiber, having a first propagation constant, and a second optical fiber, having a second propagation constant which is different from the first. The said splice comprises a coupling region between an end portion of the said first optical fiber and an end portion of the said second fiber, such that a coupling of at least 90% of the optical power in a waveband of at least 100 nm is obtained between the said first fiber and the said second fiber.

Abstract: Optical switch comprising an input optical collimator having a first axis of collimation of an optical beam, two output optical collimators, one having a second axis and one having a third axis of collimation of an optical beam, and a device for the distribution of the optical beam directed along the said first collimation axis towards one of the said second and third axes of collimation of the optical beam. The said device comprises at least one reflector movable between a first and a second predetermined position, which provides an optical connecting path between the said input collimator and one of the said output collimators, in which each of the said first and second positions corresponds to the selection of one of the said output collimators.

Abstract: Method of determining the axis of polarization of polarization-maintaining fibers, comprising: a) sending a polarized optical signal along a polarization fiber; b) emitting the polarized optical signal from one end of the fiber; c) inserting a polarizer between the fiber and an optical power; d) rotating the polarizer, and e) rotating the optical fiber.

Abstract: A twin coupler system includes first and second optical couplers that couple a multimode pump fiber into a double-clad active primary fiber. The pump fiber carries multimode pump power from a multimode source. The primary fiber, on the other hand, carries optical information signals on the single mode core that are amplified through the pump power. A system and method for manufacturing the twin coupler system constructs the first coupler by preparing first portions of the primary and pump fibers for coupling and performing fusion and tapering operations on the primary and pump fibers at the first portions, and constructs the second coupler by preparing second portions of the primary and pump fibers for coupling and performing fusion and tapering operations on the primary and pump fibers at the second portions.

Abstract: A method for fusion-forming an optical signal attenuator using a piece of optical fibre, comprising essentially the following steps:a) fusing the piece of optical fibre;b) manipulating the piece of optical fibre during fusion;c) inserting the piece of optical fibre into a mechanical adaptor for connection to two standard connectors butt-coupled respectively to the ends of two optical fibres, wherein the manipulation of the piece of optical fibre during fusion is effected by subjecting the piece of optical fibre to both axial misalignment and angular misalignment.