Sensor assembly

A wheel assembly, comprising:

• an axle,
• a bearing mounted to the axle,
• a wheel mounted to the bearing, and
• a sensor for sensing a property of the bearing, wherein the sensor comprises an optical fibre that extends along the axle.

An aircraft system comprising:

• a wheel supported on an axle by a first bearing and a second bearing;
• a first fibre optic sensor provided at the first bearing for sensing a strain or temperature of the first bearing;
• a second fibre optic sensor provided at the second bearing for sensing a strain or temperature of the second bearing;
• and
• an interrogator configured to receive optical signals from the sensors, and analyse the optical signals to determine differences in the strains or temperatures of the first bearing and the second bearing.

A sensor arrangement for an aircraft comprising a wheel supported by a first bearing and a second bearing, comprising:

• a first fibre Bragg grating sensor for sensing a strain or temperature of the first bearing;
• a second fibre Bragg grating sensor for sensing a strain or temperature of the second bearing;
• and
• an interrogator for receiving optical signals from the sensors, and for analysing the optical signals to determine differences in the strains or temperatures of the first bearing and the second bearing.