Abstract: An optical amplifier for telecommunication lines over which communication signals at a predetermined wavelength are transmitted. The amplifier has portions of two optically coupled fibers, at least one of the fibers being an active fiber, interconnected by a length of active fiber connected to the one fiber of successive portions. Preferably, the active fibers are doped with erbium, and the coupling wavelength of the two fibers is different from the communication signal wavelength so that energy of the spontaneous emission of erbium is transferred from the one fiber to the other fiber and absorbed in the latter permitting amplification of communication signals in a range of wavelengths corresponding to the tolerance range of commercial laser signal emitters.

Abstract: The invention relates to an optical amplifier, in particular for optical fiber telecommunication lines (1), operating with a transmission signal in a predetermined wavelength range, which amplifier comprises a fluorescent active optical fiber (6) doped with erbium, having two cores (11 and 12, 101 and 102), one (11, 101) of which is connected to a fiber (4) in which a transmission signal to be amplified and a luminous pumping energy are multiplexed, and to an outgoing fiber adapted to transmit the amplified signal, whereas the second core (12, 102) is optically coupled to the first core and is capable of absorbing the spontaneous erbium emission which would constitute a noise source, allowing a signal to be amplified in a wavelength range substantially corresponding to the tolerance range of the commercially available signal laser emitters.

Abstract: An optical fibre structure usable in amplifying optical signals, comprising a length of optical fibre (1) which includes two uniformally spaced monomode optical cores (2,4) located within a common cladding (6) so as to provide two optical guidance paths, the optical characteristics of at least the cores being different such as to give the two guidance paths different propagation constants the values of which coincide for a predetermined coupling wavelength, one of the cores including a fluorescent material capable of producing stimulated emission. There is also disclosed a method of amplifying an optical signal using such an optical fibre structure, comprising arranging for the wavelength (.lambda..sub.s) of the optical signal, the fluorescent wavelength of said material in said one core, and said predetermined coupling wavelength all to be substantially the same, launching optical pump energy having a different wavelength (.lambda..sub.

Abstract: An electrically tunable optical fibre structure comprising a length of optical fibre which includes two uniformly spaced monomode optical cores (1,2) located within a common cladding (4) so as to provide two optical guidance paths, the optical characteristics of at least the cores being different such as to give the two guidance paths different propagation constants the values of which coincide for a predetermined wavelength, so that optical energy at said wavelength will repeatedly transfer from one core to the other, characterized in that two electrodes (6,8,20) are provided within the cladding and are located with at least one core between them for applying an electrical field to that core whereby to alter its propagation constant by the electro-optic effect and hence to alter said wavelength, the structure thereby being tunable. Methods of making such a structure are also disclosed.

Abstract: An optical fibre sensor 11 has two monomode cores 13,14 arranged in a common cladding 15 to allow cross-talk of optical signals between the cores as a function of strain, temperature and optical wavelength. Optical signals are generated by a generator 16 at two wavelengths, at one of which cross-talk between the cores 13,14 is temperature independent. The generated optical signals are injected into the element 11 via an optical fibre lead 18 having a single monomode core 19 which is connected to one of the cores 13 of the element 11 at one end thereof and after cross-talk between the cores, optical signals are extracted from the element, for example via the same lead 18, and processed to determine temperature and strain at the element.