Modified J(1) ... J(4) method for linear readout of dynamic phase changes in a fiber-optic homodyne interferometer.

Fiber-optic interferometers have been studied extensively for sensing applications. Recently a technique described as the J(1) ... J(4) technique was reported for the linear measurement of dynamic phase changes in a fiber interferometer that requires no phase bias and for which the measurement is independent of random phase fluctuations. However, the implementation of the J(1) ... J(4) technique is limited because only the magnitude of the J(1) ... J(4) Bessel components can be measured on a spectrum analyzer without information available on the sign of the Bessel function. Here a modified signal-processing technique that overcomes the limitations mentioned above is described.