A novel tunable fiber ring laser configuration with a combination of bidirectional Raman amplification and dual erbium-doped fiber (EDF) amplification is proposed for realizing high optical signal-to-noise ratio (SNR), long-distance, quasi-distributed fiber Bragg grating (FBG) sensing systems with large capacities and low cost. The hybrid Raman–EDF amplification configuration arranged in the ring laser can enhance the optical SNR of FBG sensor signals significantly owing to the good combination of the high gain of the erbium-doped fiber amplifier (EDFA) and the low noise of the Raman amplification. Such a sensing system can support a large number of FBG sensors because of the use of a tunable fiber Fabry–Perot filter located within the ring laser and spatial division multiplexing for expansion of sensor channels. Experimental results show that an excellent optical SNR of $\sim 60\mathrm{dB}$ has been achieved for a $50\mathrm{km}$ transmission distance with a low Raman pump power of $\sim 170\mathrm{mW}$ at a wavelength of $1455\mathrm{nm}$ and a low EDFA pump power of $\sim 40\mathrm{mW}$ at a wavelength of $980\mathrm{nm}$ , which is the highest optical SNR achieved so far for a $50\mathrm{km}$ long FBG sensor system, to our knowledge.