Fiber optic hydrophone (FOH) is a new type of underwater acoustic sensor, which can be used in both military and civilian fields such as underwater target detection, oil and natural gas prospecting, and earthquake inspection. With the increase of ocean ambient noise and the development of noise suppression techniques for the underwater targets, people's demand for high-performance FOH is becoming more and more urgent. Therefore, this article introduces FOH technology from three aspects, including main development trends, key technologies and new-type FOH. In detail, large-scale FOH array, very low frequency detection, deep-sea and long-haul transmission, towed linear array, narrow-linewidth laser, signal processing, fiber optic vector hydrophone and distributed FOH are introduced. This research has certain guiding significance for the theoretical research and practical application of FOH system.