Abstract: According to a first aspect of the present invention there is provided an apparatus for performing power equalization and phase correction of two signals (400). The apparatus comprises a first hybrid coupler (401) configured to operate as a power combiner, and a second hybrid coupler (402) configured to operate as a power divider, wherein the apparatus is configured to provide an output (406) of the first hybrid coupler as an input (407) to the second hybrid coupler.

Abstract: There is disclosed an electronic apparatus comprising a chip within a casing. A thermoelectric cooler has thermal connections to the chip and the casing and is configured to transport heat from the chip to the casing. A temperature measuring device is provided for determining the temperature of the chip. A control system is configured to maintain the chip at a target temperature by controlling current supplied to the thermoelectric cooler in response to the measured temperature. A temperature selection system is configured to select the chip target temperature dynamically on the basis of the casing temperature.

Abstract: An optical amplifier system is provided which comprises first and second optical amplifiers (1, 2) for amplifying optical signals in a fibre optic communications link and a common pump (3) for optically pumping both the first amplifier (1) and the second amplifier (2) to effect such amplification. There is also provided an optical switch (6) for providing an optical path between the pump and the first amplifier in a first switching state and an optical path between the pump and the second amplifier in a second switching state to enable pumping of the first and second amplifiers by the pump sequentially. Advantageously this arrangement provides high accuracy to the outputs (4, 5) of the pump (3) and reduces low power pump noise.

Abstract: According to a first aspect of the present invention there is provided an apparatus for performing power equalisation and phase correction of two signals (400). The apparatus comprises a first hybrid coupler (401) configured to operate as a power combiner, and a second hybrid coupler (402) configured to operate as a power divider, wherein the apparatus is configured to provide an output (406) of the first hybrid coupler as an input (407) to the second hybrid coupler.

Abstract: There is disclosed an electronic apparatus comprising a chip within a casing. A thermoelectric cooler has thermal connections to the chip and the casing and is configured to transport heat from the chip to the casing. A temperature measuring device is provided for determining the temperature of the chip. A control system is configured to maintain the chip at a target temperature by controlling current supplied to the thermoelectric cooler in response to the measured temperature. A temperature selection system is configured to select the chip target temperature dynamically on the basis of the casing temperature.

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.