A technique for accurately calibrating the motion of a phase mask used to inscribe complex fibre Bragg grating...

A technique is described for calibrating the amplitude of motion of a phase mask typically used for inscribing fibre Bragg grating (FBG) structures. The motion of the phase mask is detected using a simple Michelson interferometer that can be readily mounted onto an FBG writing system. The output of the interferometer provides a direct indication of the phase mask motion as a function of the true periodicity of the phase mask structure and so is ideally suited to inscription of apodised or phase shifted FBG structures. The technique can be automated and can achieve accuracies of +/-1 nm in approximately 1 minute.