Fig. 3: Advanced compensation schemes for attenuation difference proposed by researchers.
From: Physics and applications of Raman distributed optical fiber sensing
a1 Dual laser pumping scheme. a2 Raman OTDR traces based on dual laser pumping. b1 Optical attenuation calibration scheme and (b2) Raman OTDR traces based on the optical attenuation calibration scheme of the entire sensing fiber. c1 End reflection self-calibration scheme. c2 Raman OTDR traces based on the end reflection self-calibration. d1 Double-end loop demodulation scheme. d2 Raman OTDR traces based on double-end loop demodulation
