Abstract: An electrochemical sensor apparatus and electrochemical sensing method are described, using one or more working electrodes (110) of boron doped diamond (BDD). A cathodic reduction process provides a cathodic measurement and, substantially simultaneously, an anodic oxidation process provides an anodic measurement. A sum of a content of two equilibrium species within an aqueous system is obtained using both the cathodic measurement and the anodic measurement. One example measures total free chlorine by simultaneously measuring hypochlorous acid (HOCl) and hypochlorite ion (OCl-). The BDD working electrode (110) comprises at least one ablated region (115) which introduces non-diamond carbon sp2 material. The ablated region (115) may comprise one or more grooves (114) which are cut into the working surface (112), e.g. by a laser.

Abstract: An optical amplifier is described that comprises at least two sections of amplifying optical fibre and pumping means for optically pumping the amplifying optical fibre. Optical fibre support means, for example a channel or channels in a substrate, are also provided to hold the two or more sections of amplifying optical fibre substantially straight during use. The optical fibre support means also includes a means for coupling light between the at least two sections of amplifying optical fibre. The at least one amplifying optical fibre may comprise an Erbium doped core to provide an erbium doped fibre amplifier (EDFA).

Abstract: Optical circuits for optical amplifier input and output stages are described. The input stage circuit (42) comprises a first optical waveguide (46) for carrying a signal beam to be amplified, a second optical waveguide (62) for carrying a pump beam, a beam combining means (58) optically coupled to the first and second optical waveguides (46, 62) for producing a combined signal/pump beam, and means for optically coupling the combined signal/pump beam into an amplifying optical fibre (63). The output stage circuit (44) comprises a first output optical waveguide (64), an optical fibre attachment means arranged to receive an amplifying optical fibre (63) and an optical fibre attachment means arranged to receive an output optical fibre (76) wherein light from the amplifying optical fibre (63) is optically coupled to the output optical fibre (76) via the first output optical waveguide (64).