Measuring brillouin backscatter from an optical fibre using channelisation

Apparatus for measuring Brillouin backscattering from an optical fibre comprising:

• a first optical source operable to generate probe pulses of coherent light at a frequency f0 and launch probe pulses into an optical fibre;
• a receiver operable to receive backscattered light from the optical fibre that includes at least one Brillouin spectral line at a frequency fB(t) shifted from f0 by a Brillouin shift, the Brillouin spectral line varying with time/distance along the fibre, and to deliver a signal representative of the received backscattered light;
• a divider operable to divide the signal into a plurality of signal components each having a different frequency band and deliver each component to a detection channel, each detection channel comprising:
• a detector operable to detect the signal component and generate an electrical signal;
• and
• an analog-to-digital converter operable to digitize the electrical signal by sampling to generate a sequence of digital samples representing the electrical signal;
• and
• a processor operable to process the digital samples from the detection channels to determine one or more properties of the Brillouin spectral line of the received backscattered light as a function of time/distance along the fibre.