Phase-sensitive　optical　time　domain　reflectometry　(φ-OTDR)　utilizes　the　back　Rayleigh　scattered　light　to　realize　long-distance　and　high　spatial　resolution　vibration　and　acoustic　waves　detection　in　the　whole　sensing　fiber.　The　φ-OTDR　has　been　widely　used　in　structure　health　monitoring,　gas　pipelines　preventing　digging,　etc.　For　practical　applications,　because　of　weak　backscattering　Rayleigh　light　and　exponentially　decreased　injecting　optical　signal　along　the　optical　fiber,　long　distance　φ-OTDR　detection　is　very　difficult　to　realize,　so　how　to　extend　detecting　range　meanwhile　possessing　a　relatively　high　spatial　resolution　turns　into　a　challenge　in　φ-OTDR.　We　proposed　a　scheme　of　adjusting　EDFA　output　optical　power　to　use　segmented　measurement　to　improve　the　performance　of　φ-OTDR,　which　can　extend　detecting　range　to　several　tens　of　kilometers.　A　segmental　measurement　scheme　was　proposed　and　the　experimental　results　were　presented.　©　Published　under　licence　by　IOP　Publishing　Ltd.