The roughness of sea surface affects the optical property of the exiting upward laser, which constrains the application of
the LIDAR and Laser Communication in ocean. The paper designs one pool test to study the influence of sea-air
interfaces and develops a corresponding geometric optical model. It analyzes the optical property of the upward laser
through the sea-air interface systematic. Results show that the roughness of wavy sea surface will affect beam spreading,
pointing and scintillation when transmitting through the boundary. Further, experiment results in one water tank with
man-made wave show that the incident angle and divergence angle are very important to the upward laser on the
real-time and statistics change. Selecting one appropriate incident angle and divergence angle will get one stabilized
performance, which is useful to the laser practical application on the marine areas.
The optical Pulse Position Modulation (PPM) is applied widely in Free Space Optical communication (FSO) with the
low average power and the high peak power. The transmitted PPM information depends on the location of the coming
optical pulse signals in fixed period. Both receiver and transmitter should been kept in time slot synchronization and
frame synchronization in demodulation. Because the channel is very complex, the received optical pulse width will be
stretched randomly. We design and realize one digital PPM modulation receiver with high sensitivity using the
technology of PMT, A/D converter, and DSP. It is suitable to the total digital optical receiver with random time slots and
random pulse width. The paper will mainly discuss the realization of the soft demodulation behind A/D converter. The
key of PPM digital soft modulation is the establishment of the synchronization that involves the segment
synchronization, the fame synchronization and the bit synchronization. The synchronization can be obtained by seeking
for the frame head in data frames. Based on the estimation of received waveform characteristics, we adopt a matched
filter without the best factors firstly. Thereafter, their errors will be self-adapted while finding the synchronization head.
Considering the real-time need, we choose the reduced mode of maximum likelihood function judgment finally. In the
experiments, results with high sensitivity and low bit error rate have been achieved.
Laser remote sensing underwater acoustical signal is one effective way to recognize underwater targets and realize
on-board active scanning, acquisition, pointing and tracking over a wide range. By the research of the theoretical
and the simulation of PC, one fundamental experiment system is constructed, which validates the feasibility of
laser detection of underwater acoustic signal. The size and location of the diaphragm of the detection system are
particularly discussed and one optimum diaphragm aperture was developed. The affection of the incidence beam
width is also analyzed. By selecting the very incident angle and beam width, we can get the best performance.
These conclusions has the important guiding significance to the technology of laser remote sensing underwater
acoustic signal. As a whole laser remote sensing underwater acoustic signal has its own advantages and opens up
broad possibilities for the practical application. Of course it still has something to do to improve its performance,
which worth doing further studies.
A technique is developed to detect underwater acoustic signals by utilizing the resultant surface perturbations. It
uses light wave in air and uses acoustic wave under water. Because two best channels are combined together, it is
an ideal method for remotely detecting underwater acoustic signals. The underwater acoustic signal can cause the
perturbations at water-air interface. These perturbations result in an amplitude modulation effect on a laser beam
reflected by the water surface. The modulated underwater laser signal can be detected by using a direct light
intensity detecting method. Based on the theory of modulation of the intensity of laser, a detection system was
developed in the laboratory. By analyzing the massive experimental data, the technique of laser detection of
underwater acoustic signals is validated.