Modulated continuous wave

Abstract: Apparatus for analyzing thin surface layers. An acoustic wave generating laser beam is amplitude modulated with continuous wave modulation of a frequency in the megahertz to gigahertz range and an optical system directs the modulated radiation to a surface of a thin surface layer. This in turn causes an acoustic wave that is sensed and analyzed to provide an indication of properties of thin surface layer.

Abstract: An intensity modulation hard-target differential laser absorption lidar system for CO2 sensing is demonstrated. On and off wavelength lasers are modulated with 10 kHz and 12 kHz sinusoidal waves. The echo is extracted using coherent detection technique. The system is fiber based, which makes it compact and removable. We obtain three day variation of horizontal column averaged CO2 concentration of Shanghai district. We also propose an accuracy evaluation method based on electronic noise analysis combined with laser frequency modulation. The result shows that the measurement precision for the column corresponds to 3.39×10-6 (rms) with 1s integral time and 450 m path.

Abstract: The invention discloses an integrated two-dimensional multi-beam laser radar launching system based on a butler matrix. The system comprises an adjustable laser array, a frequency modulation continuous wave modulation array, an N*N butler optical matrix network, an N*M optical beam expanding network, an M-path phase shifter array and an M-path two-dimensional laser radar transmitting end; narrow line wide continuous light output by the adjustable laser array generates N paths of frequency modulation continuous optical signals through the frequency modulation continuous wave modulation array, after processing by the N*N butler optical matrix network and the N*M optical beam expanding network, the energy of each path of frequency modulation continuous optical signal is divided into M outputports, and the M-path phase shifter array generates an equal-difference phase which is continuously adjustable in phase difference between the M paths of optical signals; and M paths of optical signals with continuously adjustable phase difference are transmitted through the transmitting end of the M-path two-dimensional laser radar, and no more than N different two-dimensional adjustable transmitting beams are achieved. The system is simple, the resolution, the anti-interference capability and the survival capability of the radar can be improved, and the energy of the transmitting wave beam is fully utilized.

Abstract: A vibrating FBG acceleration measuring system with continuous wave modulation frequency and wavelength division multiplex technology is presented in this paper.Double FBG acceleration detector with pressure strain and drag strain applying simultaneity is designed.Selects difference of its central reflection wave length as sensing signal.Both eliminated the temperature noise to the sensing signal disturbance,and enhanced the measuring sensitivity and the resolution.Using wavelet signal processing methods not only completed the optical wavelength absolute code,improved the imbalanced and nonlinear optical signal efficiently,but also reestablished micro accelerating signal.This system has some advantages such as simple structure,high scan frequency,high resolution and good linearity.