{'fraction_non_alphanumeric': 0.03412616339193381, 'fraction_numerical': 0.020682523267838676, 'mean_word_length': 5.165605095541402, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
High-sensitivity fiber salinity sensor based on an exposed-core microstructured fiber interferometer

A high-sensitivity salinity sensor based on a free space propagation-core mode Mach–Zehnder interferometer was proposed with a well-designed exposed-core microstructured optical fiber. The real-time salinity sensing was achieved by using an exposed-core microstructured optical fiber shortened to 228 µm. The proposed sensor has a salinity measurement range from 0 ‰ to 40 ‰ and a salinity sensitivity of around  −2.29 nm/‰, corresponding to a refractive index sensitivity of  −13 103.16 nm/RIU. The measurement error caused by the temperature is only 0.02 ‰ °C−1, which can be neglected in practical applications. This kind of sensor also presents a Fabry-Perot interference phenomenon besides the Mach–Zehnder interferometer, which shows a flexible sensing structure. The proposed sensor offers an alternative method for accurate measurement of seawater salinity.