Abstract: A fiber sensing system according to the present disclosure includes a submarine cable, and a plurality of relaying apparatuses being connected in series to one another via the submarine cable. The relaying apparatus includes a DAS interrogator being connected to a relaying apparatus at a subsequent stage via a sensing optical fiber in the submarine cable, and a terminator being connected to a relaying apparatus at a preceding stage via the sensing optical fiber. The DAS interrogator outputs probe light to the sensing optical fiber. The terminator terminates probe light being output from the DAS interrogator in the relaying apparatus at the preceding stage to the sensing optical fiber. The DAS interrogator receives backscattered light of probe light from the sensing optical fiber, and acquires the DAS data from the received backscattered light.