Abstract: An optical amplifier is disclosed comprising a signal semiconductor optical amplifier having a waveguide, forming at least part of a signal path between an input and an output, extending along a signal active region for amplification of a signal. The amplifier also includes a control active region of semiconductor material having a gain which is controllable independently from the gain of the signal active region. The amplifier also includes a laser cavity containing both the signal active region and the control active region and being capable of clamping the gain of the signal active region, and the control active region is arranged not to amplify a signal in the signal path within a predetermined signal band.

Abstract: An automatic power control system for automatic power control of a semiconductor optical amplifier arranged to amplify a signal has an automatic power control loop which provides automatic power control of the power of the amplified signal for maintaining the power of the amplified signal in the output from the semiconductor optical amplifier at a desired level. The automatic power control loop compensates for, an estimated level of amplified spontaneous emission in the detected output power using stored characteristics of the semiconductor optical amplifier. In one type of embodiment, a photodiode detects the output power of the semiconductor optical amplifier and a current detector detects the drive current of the semiconductor optical amplifier and the automatic power control loop uses both the detected output power of the semiconductor optical amplifier and the detected drive current.

Abstract: A detection system for use in detecting the presence of a non-aqueous organic measurand is provided. The system comprises a fiber-optic probe assembly incorporating an optical fiber which is susceptible to micro bending anywhere along its length, and a body of material contained within a rigid containment structure, wherein said body comprises a material selected from the group consisting of a rubber, plastic and semi-crystalline/rubbery polymeric material which is subject to a volumetric change capable of inducing a microbend in said optical fiber in the presence of said non-aqueous organic measurand and wherein the body of material is a substantially continuous coating which has a thickness prior to contact with the non-aqueous measurand of less than 7.

Abstract: A detection system for use in detecting the presence of a non-aqueous organic measurand is provided. The system comprises a fibre-optic probe assembly incorporating an optical fibre which is susceptible to micro bending anywhere along its length, and a body of material contained within a rigid containment structure, wherein said body comprises a material selected from the group consisting of a rubber, plastic and semi-crystalline/rubbery polymeric material which is subject to a volumetric change capable of inducing a microbend in said optical fibre in the presence of said non-aqueous organic measurand and wherein the body of material is a substantially continuous coating which has a thickness prior to contact with the non-aqueous measurand of less than 7.

Abstract: A measurand is detected by a sensor element forming part of a transducer unit which is filled to an optical fiber or fiber capable such that the fiber is bent or curved to an abnormal level which introduces a measurable loss in the transmission characteristics of the fiber. The transducer unit has three spaced clamp members arranged to be clamped along the length of the fiber. The sensor element is fitted between clamp members and the fiber is guided over a bar located between clamp members.

Abstract: A system for detecting the presence of a target measurand, such as water or specified chemicals which are carried in an aqueous solution, and which includes a fibre-optic probe assembly which incorporates an optical fibre, a thin film of a water swellable hydrogel, and a rigid containment structure. The hydrogel is in contact with the optical fibre such that a volumetric change in the hydrogel causes a microbend of the optical fiber. The microbend is detected by a sensor assembly which is coupled to the probe assembly.