Abstract
In this paper, we report a novel and compact sensor based on an optic microfiber coupler interferometer (OMCI) for seawater salinity application. The OMCI device is fabricated by connecting Faraday rotating mirrors to the two out-ports of the microfiber coupler, respectively. The sensor signal processing is based on a wavelength demodulation technique. We theoretically analyze the sensing characteristics with different device structure parameters. Besides, the results show that the date reading error decreases with the thinner waist region and longer arm difference. Through the experiment, the reflection spectra red-shifted as the sea water salinity increased; the highest response sensitivity of the OMCI salinity sensor reached 303.7 pm/‰ for a range of 16.6–23.8‰, and the resolution was less than 0.03‰. This study provides a new technical solution for the development of practical optical fiber seawater salinity sensors.
Highlights
Salinity is one of the basic parameters of the ocean state equation
When the arm of the optic microfiber coupler interferometer (OMCI) is not equal, the difference is that the interference peaks related to the interferometer arm differences appear in temperature T is 25 °C, the OMC uniform waist length L is 2 mm, and the radius of the optical microfiber (OM) is 1.55 μm, the salinity response characteristics of the OMCI transmission spectra under different arm differences are simulated and analyzed
For example, the salinity sensors based on optical reflection have high sensitivity, but their prism systems are complicated and difficult to apply to harsh marine environments
Summary
Salinity is one of the basic parameters of the ocean state equation. At the same time, it plays an important role in global water cycle change, and provides a means of studying the linkages of the oceans with the terrestrial water cycle, which affects marine phenomena such as precipitation and circulation [1,2,3,4]. Due to the characteristics of large evanescent surface to plasmon resonanceenvironmental [2,18], and interferometer the above types of optical field transmission (a salinity light field transmitted outside thesuch boundary surface ofand thesusceptibility waveguide) fiber seawater sensors have various problems as low sensitivity to [21] Gradually be very sensitive to surrounding environmental changes due to the characteristics of large evanescent used in ocean salinity sensing research, including the microfiber knot resonator [6], optical microfiber field transmission (a light field transmitted outside the boundary surface of the waveguide) [21] It coupler (OMC) [22,23,24], and OMC-Sagnac [25]. Compact optical path, and provides new technical solutions for the development of practical optical fiber seawater salinity sensors
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