Micro-force measurement with pre-curvature long-period fiber grating-based sensor

¹ Technological Institute of Aeronautics [Instituto Tecnológico de Aeronáutica - ITA], Praça Mal. Eduardo Gomes, 50, São José dos Campos-SP, 12228-900, Brazil.
² Institute for Advanced Studies [Instituto de Estudos Avançados - IEAv], Trevo Cel. Av. José A. A. do Amarante, 01, São José dos Campos- SP, 12228-001, Brazil.
³ INESC TEC - Institute for Systems and Computer Engineering, Technology and Science, 4200-465 Porto, Portugal.
⁴ Escola Superior de Tecnologia e Gestão, Instituto Politécnico de Viana do Castelo Rua Escola Industrial e Comercial de Nun’Álvares, n.º34 4900-347 Viana do Castelo
⁵ Departamento de Física e Astronomia da Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal

^* Corresponding author:pcaldas@estg.ipvc.pt

Published online: 20 August 2020

Abstract

In this work, a long-period fiber grating (LPG) based sensor was evaluated as a sensing device for micro-force measurement, in the order of micro Newtons. It was used an LPG fabricated by arc-inducted technique in a SMF-28 standard optical fiber. The optical fiber was fixed between two clamps with a separation of 150 mm with the middle of the LPG located at the center. Characterizations were performed in terms of temperature, curvature and strain. The grating was then used as a micro-force sensor by means of both curvature and strain, induced by a hung mass in a stretched fiber. Furthermore, the evaluation of a precurvature LPG was performed to assess if an increase of sensitivity is achieved. Micro-force sensitivity achieved with the stretched LPG was 1.41 nm/mN and it was demonstrated that its sensitivity can be enhanced to 5.14 nm/mN with a pre-curvature of 2.2 m^–1 applied to the LPG, achieving a spectral resolution of at least 15.6 μN.