Although burning laser pointer has been based on the construction of various infrastructure found useless, but it still exists some problems. One problem is that the scope of monitoring is limited. Recent analysis shows that the power probe span up to several kilometers to may cause the pump pulse signal distortion, seriously affect the accurate detection.
Another problem is the limited burning laser pointer. because the interaction depends on the nonlinear optical and material to produce sound waves, so the spatial resolution of a small but very obvious. There are delays in the time domain technique in frequency and other technical related domain can make up for the shortcomings of SBS, but it needs longer time, measured along the one million point fiber distribution takes about an hour or longer.
Most of the time domain based on burning laser pointer scheme, the frequency shift is by symmetrically scanning two sideband beam pumping pulse frequency offset relative to the fixed transport determined. However, in fact, the scanning method is main source of high power probe pulse distortion. This is because the two sideband probe and the pump energy between pulses is difficult to quantify the asymmetric transfer effect increased with the increase of probe power.
By changing the burning laser pointer, the band edge detection beam fixed frequency difference, and associated with frequency of the input pump beam scanning, which can significantly reduce the signal distortion. This method means that the beam power limit becomes higher, and the optical fiber sensing system the span becomes longer.