Cost-Effective Brillouin Optical Time-Domain Analysis Sensor Using a Single Optical Source and Passive Optical Filtering

Figure 4

Optical spectrum of the optical signal at  GHz in different positions of the setup (black solid) (a) at the output of the DFB-EAM module, transfer function of the FBG1 (blue dash-dot), and transfer function of the FBG2 (red dashed), (b) at the input of the EDFA in the upper branch of the setup, and (c) at the beginning of the fiber in the lower branch of the setup.

(a)

(b)

(c)