A method of processing strain measurements during fibre-optic sensing using a first sensor which is a first optical fibre : characterized by : providing a second sensor which is a second optical fibre positioned for acoustic waves to be incident on both the first and second optical fibres, wherein the first optical fibre has a first magnitude sensitivity associated therewith; the second optical fibre has a same direction of acoustic sensitivity as the first optical fibre and the second optical fibre has a second magnitude sensitivity that is different to the first magnitude sensitivity; measuring a first backscattered optical signal in respect of the first optical fibre and a second backscattered optical signal in respect of the second optical fibre, wherein the first measured signal has a first phase signal associated therewith; the second measured signal has a second phase signal associated therewith that constitutes a consolidation of the first phase signal and an additional phase signal, wherein the first phase signal and the additional phase signal are indistinguishable from one another in the phase domain; processing the first phase signal, processing the second phase signal to obtain the additional phase signal; and constructing a strain measurement signal using the processed first phase signal and the additional phase signal. characterized by : providing a second sensor which is a second optical fibre positioned for acoustic waves to be incident on both the first and second optical fibres, wherein the first optical fibre has a first magnitude sensitivity associated therewith; the second optical fibre has a same direction of acoustic sensitivity as the first optical fibre and the second optical fibre has a second magnitude sensitivity that is different to the first magnitude sensitivity; providing a second sensor which is a second optical fibre positioned for acoustic waves to be incident on both the first and second optical fibres, wherein the first optical fibre has a first magnitude sensitivity associated therewith; the second optical fibre has a same direction of acoustic sensitivity as the first optical fibre and the second optical fibre has a second magnitude sensitivity that is different to the first magnitude sensitivity; measuring a first backscattered optical signal in respect of the first optical fibre and a second backscattered optical signal in respect of the second optical fibre, wherein the first measured signal has a first phase signal associated therewith; the second measured signal has a second phase signal associated therewith that constitutes a consolidation of the first phase signal and an additional phase signal, wherein the first phase signal and the additional phase signal are indistinguishable from one another in the phase domain; processing the first phase signal, processing the second phase signal to obtain the additional phase signal; and constructing a strain measurement signal using the processed first phase signal and the additional phase signal. the first measured signal has a first phase signal associated therewith; the second measured signal has a second phase signal associated therewith that constitutes a consolidation of the first phase signal and an additional phase signal, wherein the first phase signal and the additional phase signal are indistinguishable from one another in the phase domain; processing the first phase signal, processing the second phase signal to obtain the additional phase signal; and constructing a strain measurement signal using the processed first phase signal and the additional phase signal. <EOS>