Phase demodulation in optical fibre Fabry–Perot sensors with inexact phase steps

The authors describe an algorithm that extends the usefulness of phase stepping as a method for phase recovery from Fabry–Perot cavities. The use of arbitrary step sizes eliminates the need to operate with predetermined phase steps, thus minimising the effect of phase step errors. Furthermore, an iterative technique that accounts for multiple-reflection cavities is discussed. The algorithm is demonstrated on data obtained from an intrinsic fibre Fabry–Perot heat-flux sensor.