Fig. 1. Principle diagram of the correlation between the Brillouin Stokes light and the reference light.

Fig. 2. Experimental setup of the partially coherent BOCDR using a noise-modulated LD.

Fig. 3. (Color online) Characteristics of a laser source with the noise-modulation intensity. (a) The time sequence, (b) the power spectra, (c) the optical spectra, and (d) the linewidth and the coherence length versus modulation power.

Fig. 4. (Color online) (a) The distribution of the Brillouin spectrum, and (b) the distribution of the BFS along the FUT with a 9 m long heated section.

Fig. 5. (Color online) Evaluation of the spatial resolution based on the noise-signal modulation using (risetime+falltime)/2 equivalent length, with (a) a −10dBm modulation power and (b) a −3dBm modulation power.

Fig. 6. (Color online) Backscattering light spectra of the pump light with a −10dBm noise modulation power.

Fig. 7. (Color online) Coherence length of the Brillouin Stokes light as a function of the noise modulation power with different Brillouin backscattering states.

Fig. 8. (Color online) Measured spatial resolution, the coherence lengths of the pump light and Brillouin backscattering Stokes light, and the measured errors under different modulation powers.