Abstract: An Ar.sup.+ ion laser pumped optical fibre amplifier is provided with an optical fibre having a core which has been solution doped using a solution of an aluminum and an erbium salt.

Abstract: An active device (FIG. 1) comprising a length of doped fiber (1) and an end-coupled pump source (11). The fiber (1) is of single-mode geometry and incorporates rare-earth or transition metal dopant ions. These latter are incorporated at a low-level uniform concentration (.ltorsim.900 ppm). The fiber host (1) selected exhibits an inherently ultra low attentuation loss (.ltorsim.40 dB/km) at the emission wavelength. The fibers (1) are generally of long length (e.g. 5 m to 300 m) and may be coiled for compact packaging. The fiber (1) may be formed as part of a Fabry-Perot cavity (1, 7, 9); or, as a ring cavity (FIG. 8) using a doped fiber coupler (29) spliced to form a ring (27). Q-switch and mode-locking devices (19) and gratings (25) may be included as part of the Fabry-Perot cavity to allow pulse-mode operation and/or wavelength tuning, respectively. The fiber (1) may also be utilised as an amplifier.

Abstract: A fibre laser (1) of the type comprising a doped single-mode optical fibre (3) arranged between reflectors (5,7), and which is coupled (11) to an optical pumping source (9). For the given reflection efficiency of the reflectors (5,7), the length of the optical fibre (3) is chosen such that it exceeds that affording saturation and provides at its end a region for absorption (FIG. 1). The resultant hysteretic behavior of this bistable device may be utilized for logic memory (bistable), and regenerative amplification applications. To this end a second source (9') can be coupled (11',19) to the laser fibre (3).

Abstract: A method of making a preform for drawing optical fibers includes the steps of depositing a dopant material 3 in a dopant carrier chamber 1, heating the dopant material to cause it to vaporise at a predetermined rate, depositing from a mixture of a source material (GeCl.sub.4, SiO.sub.4, O.sub.2) and said vaporised dopant a mixture of solid components 8 and fusing said solid components to form a doped glass.