Patent ID: 8259387

Claim:
An optical amplifier for determining the attenuation of an optical fibre that forms a span of a network to which the amplifier is adapted to be connected comprising means ( 5 ) to receive an input signal from the optical fibre ( 7 ), means ( 6 ) to output an amplified signal to the optical fibre ( 7 ), a gain medium ( 2 ) and a pump means ( 3 ) arranged to generate the amplified signal from the input signal, the amplifier ( 1 ) further comprising means ( 13 ) to measure the optical power of the signal leaving the gain medium and means ( 14 ) to measure the optical power of the signal backscattered from the optical fibre ( 7 ), wherein the pump means ( 3 ) is controlled by a control means ( 4 ), the control means ( 4 ) being adapted to modulate the pump means ( 3 ) with a determination signal, the control means ( 4 ) being adapted to change the frequency of the determination signal over a plurality of determination frequencies while keeping the amplitude of the determination signal constant, the control means ( 4 ) further being adapted to calculate the attenuation of the length of the optical fibre ( 7 ) from the length of the optical fibre ( 7 ), the effective refractive index of the fibre ( 7 ), and the power of the signal from the gain medium and the power of the backscattered signal measured at each of the plurality of determination frequencies.