A novel method based on a tunable fiber ring laser configuration with Er-doped fiber Raman hybrid amplification is proposed for performance enhancement of long-distance in-fiber Bragg grating (FBG) sensor systems to achieve quasi-distributed measurement. Such a method employs a tunable Er-doped fiber ring laser as light source. Dual-wavelength Raman fiber amplification is adopted for achieving low-noise bidirectional amplification of FBG signals, and two sections of EDFs, arranged in the fiber link remotely, are used for generation of amplified spantaneous emission with residual pump power to illuminate remotely-located FBG sensors and amplification of sensing signals, which makes the whole sensor system capable of achieving quite high signal-noise-ratio along ultra-long distance. Experimental results show that an excellent optical signal-noise-ratio of ～57dB has been achieved for a 100 km transmission distance with a low Er-doped fiber amplification pump power of ～40 mW at wavelength of 980 nm, a low Raman pump power of ～170 mW at wavelength of 1455 nm and a Raman pump power of ～2 W at wavelength of 1480 nm,leading to FBG-based sensing along ultra-long distance.