Abstract: An optical amplifier comprises an optical fibre, a pump laser for optically pumping the optical fibre to amplify an optical signal, a TEC 1 for cooling the pump laser on receipt of a cooling current, a temperature sensor 2 for monitoring the temperature of the amplifier housing; and a control circuit 3 for controlling the cooling current in dependence on a sensing output from the temperature sensor 2, so as to maintain the temperature of the pump laser at a temperature set point. The control circuit 3 is configured (i) to maintain the temperature of the pump laser at a first temperature set point within a predetermined temperature range of the amplifier, and (ii) to maintain the temperature of the pump laser at a second temperature set point, higher than the first temperature set point, when the sensing output from the temperature sensor 2 exceeds a threshold value.

Abstract: Multistep recycling processes for preparing recycled plastic materials. The processes feature a sequence of operations selected from the group consisting of preprocessing operations, size reduction operations, gravity concentration operations, color sorting, sorting by thickness, friction, or differential terminal velocity or drag in air, surface to mass control operations, separation processes enhanced by narrow surface to mass distributions, blending operations, and extrusion and compounding operations. Plastic-rich mixtures are subjected to the process, and one or more recycled plastic materials are collected as outputs of the sequence of processes.