It is a very effective studying method to cultivate the students’ interest, but the key is how to make the students interested in the content of the learning. This paper researches a teaching method of the reversal mode. The method is to let a student to play the role of the teacher, however, the teacher is to be a student. It can make the students get knowledge very well by themselves and give full play to their potential and the subjective initiative. Compared with the previous conventional teaching, the students master the knowledge points more clearly. This method is real and effective, we get good results through a semester of teaching.
The space coherent laser communication is a very potential and attractive mean as it allows higher
speed communication between satellites. The space coherent laser communication makes use of local
oscillator laser power to improve the power of received optical signal by mixing local oscillator laser and
optical signal together. However, the power of the local laser oscillator can not be increased infinitely, too
large but reduces the detection sensitivity. In this paper, starting from the principle of the signal-to-noise ratio
of the space coherent laser communication, we found the optimum local oscillator laser power was 28.174mw,
under the condition of the selected photodetector specific parameters. It is a great significant for high
detection sensitivity and low data error of the actual coherent detection system.
The space coherent laser communication is a very potential mean for high-speed laser
communication in the future, because the excellent receiver sensitivities can be achieved by coherent
detection techniques. The best coherent receiver sensitivity amounts to -59.4dBm at a data rate of 10Gbit/s
and a bit error rate of 10<sup>-9</sup>, which is obtained with phase-shift keying modulation in combination with
homodyne detection. In this paper, we investigated optical homodyne detection based on Costas phase-locked
loop in the space coherent laser communication system. We obtain optimum loop bandwidth of Costas
phase-locked loop and the maximum permissible laser line width based on Costas phase locked loop.