A sensor system configured to sense perturbations over first and second dynamic ranges, the sensor system comprising: a source of input light pulses at a first wavelength; an array of sensors; a first optical delay path (2244, 2240, 2246, 1346) at the first wavelength; a first detection system responsive to light at the first wavelength; a second detection system; characterised in that the sensor system further comprises: a source of input light pulses at a second wavelength; a second optical delay path (2244, 2242, 2246, 1346) at the second wavelength, wherein the second detection system is responsive to light at the second wavelength; and an input/output system (1610, 1630, 1632, 1634, 1636, 1638, 1640, 1642, 1644, 1660, 1662, 1670, 1672, 1674, 1676, 1678, 1680, 1682) configured to receive the input light pulses at the first wavelength and the second wavelength, the input/output system directing a first portion of each light pulse at the first wavelength having a first polarization through the array of sensors in a first direction, then through the first optical delay path, and then to the first detection system, the input/output system directing a second portion of each light pulse at the first wavelength in a second polarization orthogonal to the first polarization through the first optical delay path, then through the array of sensors in a second direction, and then to the first detection system, the first detection system detecting variations in received light caused by perturbations varying over the first dynamic range, the input/output system directing a first portion of each light pulse at the second wavelength having a first polarization through the array of sensors in a first direction, then through the second optical delay path, and then to the second detection system, and the input/output system directing a second portion of each light pulse at the second wavelength in a second polarization orthogonal to the first polarization through the second optical delay path, then through the array of sensors in a second direction, and then to the second detection system, the second detection system detecting variations in received light caused by perturbations varying over the second dynamic range. a source of input light pulses at a first wavelength; an array of sensors; a first optical delay path (2244, 2240, 2246, 1346) at the first wavelength; a first detection system responsive to light at the first wavelength; a second detection system; a source of input light pulses at a second wavelength; a second optical delay path (2244, 2242, 2246, 1346) at the second wavelength, wherein the second detection system is responsive to light at the second wavelength; and an input/output system (1610, 1630, 1632, 1634, 1636, 1638, 1640, 1642, 1644, 1660, 1662, 1670, 1672, 1674, 1676, 1678, 1680, 1682) configured to receive the input light pulses at the first wavelength and the second wavelength, the input/output system directing a first portion of each light pulse at the first wavelength having a first polarization through the array of sensors in a first direction, then through the first optical delay path, and then to the first detection system, the input/output system directing a second portion of each light pulse at the first wavelength in a second polarization orthogonal to the first polarization through the first optical delay path, then through the array of sensors in a second direction, and then to the first detection system, the first detection system detecting variations in received light caused by perturbations varying over the first dynamic range, the input/output system directing a first portion of each light pulse at the second wavelength having a first polarization through the array of sensors in a first direction, then through the second optical delay path, and then to the second detection system, and the input/output system directing a second portion of each light pulse at the second wavelength in a second polarization orthogonal to the first polarization through the second optical delay path, then through the array of sensors in a second direction, and then to the second detection system, the second detection system detecting variations in received light caused by perturbations varying over the second dynamic range.