Coaxial Mach-Zehnder Digital Strain Sensor Made from a Tapered Depressed Cladding Fiber

An in-line digital optical sensor was proposed. It was built from a tapered depressed-cladding single-mode fiber and modeled as a coaxial Mach-Zehnder interferometer. The principle of operation of the optical digital sensor is based on the computation of the number of optical power transfer turning points (PTTP) from the transmission data of the component. Biconic tapers with high values of PTTP, high spectral resolution, high extinction ratio, and low insertion loss were modeled, fabricated, and characterized. As a proof of concept, an in-line digital strain sensor was fabricated and characterized. It presents a free spectral range of 1.3 nm, and produced 96 PTTP, at lambda(0) = 1.55 mu m, under stretch of Delta L = 707 mu m, therefore producing a digital resolution of 7.4 mu m/PTTP. The sensor also produced a quasi-symmetric response to stretch and compression.

Automated summary

An in-line digital optical sensor based on a tapered depressed-cladding single-mode fiber acting as a coaxial Mach-Zehnder interferometer is proposed. The sensor operates by computing the number of optical power transfer turning points (PTTP) from the transmission data of the component. Biconic tapers with high PTTP values, high spectral resolution, high extinction ratio, and low insertion loss were modeled, fabricated, and characterized. A proof of concept in-line digital strain sensor was fabricated and characterized, demonstrating a high digital resolution and quasi-symmetric response to stretch and compression.