A dual-parameter active fibre sensor based on modal interference in few-mode fibres

We propose a dual-parameter active fibre sensor based on a fibre ring laser using a single-mode-two-mode-single-mode (STS) fibre interferemeter and a four-mode FBG as the intracavity dual-parameter sensing element. The interferometric spectra of the STS are investigated with different core-offset parameters and few-mode fibre length. The highest LP11 mode excitation ratio is achieved with a 6μm core-offset distance in the STS which achieves best sensing ability. High precision dual-parameter sensing of pressure and tension are achieved experimentally by measurements of fibre laser output wavelength and intensity.