I. Introduction
The ship pipelines are the significant components of the ship in the use of liquids transportation [1], ensuring the stability of the voyage and meeting the needs of the crew and passengers [2]. However, pipeline leakage can pose a threat to ship operation, human safety, and marine environment [3]. It can be typically caused by vibration, high temperature, corrosion, or sabotage [4], [5]. Manual inspection is the most common method for detecting pipeline leakage. It has high accuracy for larger leakage locations but is limited by the responsibility and experience of the inspector. Several leakage detection technologies have been developed based on different types of sensors [6], such as acoustic [7], infrared [8], fiber optic [9], and ultrasonic flow sensors [10]. These sensors rely on pressure, temperature, density, flow rate, or sonic velocity to detect and locate pipeline leakage. However, they have low sensitivity to minor or invisible leakage that can affect the performance and safety of pipelines [11], [12]. For example, traditional ultrasonic pipeline inspection has limitations [13] in application due to wave propagation attenuation, especially in complex fluids and high-pressure pipelines [14]. Furthermore, fiber optic sensors face challenges related to complex installation, costly and intricate replacement, and vulnerability to noise [15] and variations in light transmission, posing difficulties in detecting subtle or concealed leaks [16]. Therefore, designing an effective sensor for detecting minor or invisible leakage in ship pipelines is still a challenge.