This paper presents a theoretical investigation on a type of Fiber Optic Sensing system used for seismic monitoring which incorporates an array of Fiber Bragg Gratings (FBGs) in the sensing medium. An interferometry array contains a group of interferometry sub-arrays, every sub-array including a plurality of interferometry. Each interferometer in a sub-array is realized with a particular pair of fiber Bragg gratings and a sensing length of optical fiber located between the respective pair of fiber Bragg gratings. The fiber Bragg gratings in every respective couple of fiber Bragg gratings have a similar characteristic wavelength that is altered from the characteristic wavelength of every other couple of fiber Bragg gratings in the sub-array. The sub-arrays are interconnected to minimize the common-wavelength crosstalk among the sensors in the overall interferometry array. Our work focuses on investigating the selection of the optimum wavelength for use in the system. The study was performed using state-of-the-art simulation techniques for strain and temperature changes in the FBG sensor array. The cumulative results obtained can be used to help designers produce an optimized performance for similar fiber optic hydrophones in the future. It has been shown that the wavelength 1300nm region gives the best performance in this type of fiber optic hydrophone system.