Abstract: An amplifier/filter combination including a fibre amplifier (4) and a fibre reflection/transmission filter (5) coupled to said amplifer. The fibre amplifier amplifies an input signal (1) in response to pump light (2) received from a laser. Preferably the fibre filter (5) is a chirped Bragg fibre filter which is arranged to filter out the unabsorbed portion of the pump light from the output amplified signal and which reflects the unabsorbed portion (7) of the pump light back to the amplifier (4) for re-absorption therein. The amplified signal (6) is transmitted by the filter (5) to a receiver.

Abstract: A laser source for pumping an optical device which requires for its operation a significant amount of light power, the source comprising a semiconductor array (11) for providing a plurality of spaced apart light beams at different wavelengths, an optical assembly (14, 15, 16) for focussing the light beams into an optical waveguide (19), the optical waveguide (19) being coupled to the optical device.

Abstract: An optical fibre coupling device comprises a mount 11 supporting an optical fibre waveguide having at a fibre end a surface of the fibre core 2 material which is surrounded by a body 3 of cladding material. At the core end a circular symmetric phase plate 7 is centered about the core 2 such that the light from a laser 1 entering or leaving the waveguide experiences a predetermined phase change. The phase change can act to reduce an optical coupling loss which occurs when the device is in use.

Abstract: A laser is characterized by a glass gain medium which contains trivalent samarium Sm.sup.3+ ions and which, when optically pumped on one or a number of absorption bands to achieve excitation at or above the metastable .sup.4 G.sub.5/2 level, radiates light at a wavelength substantially corresponding to transitions from the .sup.4 G.sub.5/2 level of samarium.