[1] SOHAIL T, ZIKA J D, IRVING D B, et al. Observed poleward freshwater transport since 1970[J]. Nature, 602, 617-622(2022).

[2] KATSUMATA K, PURKEY S G, COWLEY R, et al. GO-SHIP easy ocean: gridded ship-based hydrographic section of temperature, salinity, and dissolved oxygen[J]. Scientific Data, 9, 103(2022).

[3] LI Y, WU G F, SONG G, et al. Soft, pressure-tolerant, flexible electronic sensors for sensing under harsh environments[J]. ACS Sensors, 7, 2400-2409(2022).

[4] DINNAT E P, LE VINE D M, BOUTIN J, et al. Remote sensing of sea surface salinity: comparison of satellite and in situ observations and impact of retrieval parameters[J]. Remote Sensing, 11, 750(2019).

[5] DEMIR O, JOHNSON J T, JEZEK K C, et al. Studies of sea-ice thickness and salinity retrieval using 0.5-2 GHz microwave radiometry[J]. IEEE Transactions on Geoscience and Remote Sensing, 60, 4304412(2022).

[6] QIAN Y, ZHAO Y, WU Q L, et al. Review of salinity measurement technology based on optical fiber sensor[J]. Sensors and Actuators B:Chemical, 260, 86-105(2018).

[7] QUAN X H, FRY E S. Empirical equation for the index of refraction of seawater[J]. Applied Optics, 34, 3477-3480(1995).

[8] ZHENG H K, ZHAO Y, LV R Q, et al. Study on the temperature and salinity sensing characteristics of multifunctional reflective optical fiber probe[J]. IEEE Transactions on Instrumentation and Measurement, 70, 9514308(2021).

[9] ZHAO Y, ZHAO J, WANG X X, et al. Femtosecond laser-inscribed fiber-optic sensor for seawater salinity and temperature measurements[J]. Sensors and Actuators B:Chemical, 353, 131134(2022).

[10] ZHANG S Q, PENG Y, WEI X, et al. High-sensitivity biconical optical fiber SPR salinity sensor with a compact size by fiber grinding technique[J]. Measurement, 204, 112156(2022).

[11] WANG Y, TONG R J, ZHAO K J, et al. Optical fiber sensor based on SPR and MZI for seawater salinity and temperature measurement[J]. Optics & Laser Technology, 162, 109315(2023).

[12] SUN M Y, JIANG H T, SHI B, et al. Development of FBG salinity sensor coated with lamellar polyimide and experimental study on salinity measurement of gravel aquifer[J]. Measurement, 140, 526-537(2019).

[13] AN G W, LIU L, HU P, et al. Probe type TFBG-excited SPR fiber sensor for simultaneous measurement of multiple ocean parameters assisted by CFBG[J]. Optics Express, 31, 4229-4237(2023).

[14] YANG F, HLUSHKO R, WU D, et al. Ocean salinity sensing using long-period fiber gratings functionalized with layer-by-layer hydrogels[J]. ACS Omega, 4, 2134-2141(2019).

[15] ZHAO SH, DU CH, WANG Q Y, et al. A long period fiber grating seawater salinity sensor based on bend insensitive single mode fiber[J]. Optical Fiber Technology, 77, 103269(2023).

[16] LI Q SH, YANG Y, DU Y D, et al. Highly sensitive detection of low-concentration sodium chloride solutions based on polymeric nanofilms coated long period fiber grating[J]. Talanta, 254, 124126(2023).

[17] DEL VILLAR I. Ultrahigh-sensitivity sensors based on thin-film coated long period gratings with reduced diameter, in transition mode and near the dispersion turning point[J]. Optics Express, 23, 8389-8398(2015).

[18] CHEN J Y, BAI ZH Y, ZHU G X, et al. Femtosecond laser inscribed helical long period fiber grating for exciting orbital angular momentum[J]. Optics Express, 30, 4402-4411(2022).

[19] ZHANG Y N, LIU S C, ZHAO Y, . Fabrication mechanism of long-period fiber grating based on 800 nm high intensity femto-second laser pulses[J]. Acta Photonica Sinica, 47, 0106003(2018).

[20] ZHANG Y N, XI Y R, JIANG P, . Fabrication of long period fibre gratings by femtosecond laser writing directly and its spectral characteristics[J]. Acta Photonica Sinica, 47, 1106001(2018).

[21] ZHANG Y N, JIANG P, QIAO D, et al. Sensing characteristics of long period grating by writing directly in SMF-28 based on 800 nm femtosecond laser pulses[J]. Optics & Laser Technology, 121, 105839(2020).

[22] ŚMIETANA M, DOMINIK M, MIKULIC P, et al. Temperature and refractive index sensing with Al₂O₃-nanocoated long-period gratings working at dispersion turning point[J]. Optics & Laser Technology, 107, 268-273(2018).

[23] DU CH, WANG Q, ZHAO Y, et al. Ultrasensitive long-period gratings sensor works near dispersion turning point and mode transition region by optimally designing a photonic crystal fiber[J]. Optics & Laser Technology, 112, 261-268(2019).

[24] ZHU Y Y, XI Y R, ZHANG Y N, . Numerical simulation of transmission spectra characterization of long-period fiber grating[J]. Chinese Optics, 13, 451-458(2020).

[25] ZHONG X Y, WANG Y P, LIAO CH R, et al. Long period fiber gratings inscribed with an improved two-dimensional scanning technique[J]. IEEE Photonics Journal, 6, 2201508(2014).

[26] DEL VILLAR I, FUENTES O, CHIAVAIOLI F, et al. Optimized strain long-period fiber grating (LPFG) sensors operating at the dispersion turning point[J]. Journal of Lightwave Technology, 36, 2240-2247(2018).

[27] PEREIRA D A, FRAZAO O, SANTOS J L. Fiber Bragg grating sensing system for simultaneous measurement of salinity and temperature[J]. Optical Engineering, 43, 299-304(2004).

[28] DEL VILLAR I, CRUZ J L, SOCORRO A B, et al. Sensitivity optimization with cladding-etched long period fiber gratings at the dispersion turning point[J]. Optics Express, 24, 17680-17685(2016).

[29] VIVEIROS D, DE ALMEIDA J M M M, COELHO L, et al. Turn around point long period fiber gratings with coupling to asymmetric cladding modes fabricated by a femtosecond laser and coated with titanium dioxide[J]. Journal of Lightwave Technology, 39, 4784-4793(2021).