Effects of Intensity Modulation of Light Source on Brillouin Optical Correlation Domain Analysis

Fiber optic nerve systems for smart materials and smart structures

“…The shape of the spectrum shown in Fig. 3(a) is almost ideal, which is proved in simulations [27]. Figure 3(b) shows a sample fiber used in the experiment to verify the function of the intensity modulation.…”

“…Even the ratio of total length of the fiber to the spatial resolution become large, the Lorentzian-shaped signal spectrum can be clearly detected by the intensity modulation scheme, as shown in Fig. 4(a) and (b) [27]. In Fig.…”

“…In Fig. 4(c), strain applied portion along the 1,000m fiber is clearly recognized with 30cm spatial resolution [27].…”

“…Then, the total spectrum obtained in the BOCDA system has a shape of a Lorentzian peak with a mountain-shaped component [26,27]. When strain applied at the measurement position, the Lorentzian-shaped signal caused at the position slips down along the slope of the mountain-shaped component.…”

“…When the height of the signal peak becomes lower than that of the mountain-shaped spectrum component, the strain can not be measured. We have found that the problem can be solved by using an intensity modulation onto the input lightwave [26,27]. Figure 3(a) shows the averaged lightwave spectrum synthesized both with the frequency and the intensity modulation.…”