Abstract
We proposed and demonstrated an optical fiber Fabry-Perot (F-P) sensor with long sensing length for strain measurement. The structure of the sensor was fabricated with a simple process by splicing a long single mode fiber (SMF) with a short section of hollow-core fiber (HCF). The end of the SMF was cleaved with smooth reflective surface which hence allows the sensing length of the proposed sensor can achieve several centimeters with good visibility. Sensors with different sensing lengths were fabricated and experimentally analyzed in this paper. The relationship between the optical path difference (OPD) of the sensor and strain is found to be linear. With the sensing length of ∼10 mm and ∼49 mm, the sensor can achieve the OPD strain sensitivity of 20.42 nm/ μϵ and 115.57 nm/ μϵ at 1550 nm over the range of 1000 μϵ respectively. Besides, with the sensing length of ∼10 mm, the OPD temperature sensitivity of the sensor was 187.64 nm/°C. With the advantages of easy making, low cost and long sensing length, it is anticipated that the proposed sensor has great potential in measuring the strain with a large distribution.
Highlights
Nowadays, the measuring and monitoring of strain is of great significance in civil engineering, aerospace, marine and other industrial fields [1], [2]
The peak of the frequency component is dependent on the optical path difference (OPD), by properly filtering according to the position of the peak of the frequency, we can obtain the interference spectrum corresponding to the distinctive frequency component of FP1 and FP2 respectively, which has been reported in [20]
The linear fitting results indicates that the variation of the OPD is dependent on the strain as theoretically analyzed above, the relationship between the variation of OPD and the strain maintains a good linearity, and the OPD strain sensitivity of the sensor is enhanced from 20.42 nm/με to115.57 nm/με while the cavity length is increased from ∼10 mm to ∼49 mm, which is basically consistent with the theoretical value of 23.19 nm/με and 116.45 nm/με, respectively
Summary
The measuring and monitoring of strain is of great significance in civil engineering, aerospace, marine and other industrial fields [1], [2]. Optical fiber Fabry–Perot (F-P) sensors [12], [13] have attached much attention and provide possibilities for a variety of strain sensing in practical due to their advantages of simple configuration and high sensitivity. The strain sensor with the structure of the long active length F-P micro-cavity was presented in [15] to overcome the shortcomings mentioned above, and the sensing length reported in [15] was 360 με. Strain sensors based on photonic crystal fiber (PCF) have been reported by Rao et al [18] and Tian et al [19], as the loss of the transmission of the PCF is much smaller than that of the HCF, the cavity length of the sensor can enlarged up to several millimeters with a good fringe visibility. The fabricating methods mentioned above generally require high-cost micromachining or instrument, and still cannot meet the requirement when the distribution of strain is large due to the limitation of the sensing length
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