The change of field of view (FOV) which is caused by the image defocus of laser communication terminal introduced in the process of assembly will have a great interference to the link energy budget. In view of the problem, the method of measuring the FOV is proposed to calculate the defocus amount of receiving system. On the premise of the sensitivity of the detector is satisfied by the received energy, the relationship among the defocus receiving energy, defocus amount and FOV are derived by the theoretical analysis and calculation. With the link distance is 1km, the defocus amount of 0.27mm is calculated under the FOV of 0.965mrad which is measured by experimental test. The maximum FOV from 2km to 4km can be reversed further. At the same time, the test experiment platform was designed and the FOV of the laser communication terminal was measured. Compared with the theoretical calculation results, the maximum error is less than 55μrad, which is conformed to the error allowable range. Conclusion: By the method of measuring the FOV of the system, the defocus error which is caused by assembling can be calculated, so the maximum FOV of the system in different link distance can be simulated. The method not only solves the problem that the defocus amount is difficult to measure, but also provides theoretical guidance to increase the FOV of laser communication by introducing the image defocus.
With the problem of small field of view, high precision and difficulty in alignment for portable laser communication, the method and device based on measuring field of view in portable laser communication are designed and proposed. By calculating the link energy under the specified communication distance, the energy range of extensible field of view can be obtained. A high precision measuring device is designed. The actual test was carried out. The result shows that the receiving field of view for portable laser communication is 0.63mard under the condition of 1km communication distance and the sensitivity of detector -30dBm. The field of view for portable laser communication can be accurately measured by the test method and device. The test device can extend the measuring range of small field of view in different fields.
The influence of the alignment error in laser communication is analyzed. The link energy model with the position deviation at the image surface is established, and on the basis of this model, the spot deviation and the receiving optical axis deviation caused by the angular deviation of the optical axis are discussed and analyzed. Under the conditions of initial transceiver parameters, the link energy and the allowable maximum angle deviation with the distance of 0~2km are further calculated. The model formula of alignment error can be applied to analysis and discussion under the father distance. It has a theoretical guiding significance for the field laser communication test.
Demanding for the closed communication among urban buildings, a solution for close range laser communication is proposed. The functional composition of the system is demonstrated and analyzed and the parameters of the system are reasonably allocated. The system design is used with independent optical aperture. The energy model under the inherent error of transceiver is analyzed and calculated. On the basis, the actual communication test was carried out, the specific test operation process is given and the measured data are obtained. The deviation between the average data and the theory is not more than 0.58dB. The correctness of the theoretical energy model is verified. The energy model can be used to guide the design of remote distance communication terminal. At the same time, the successfully development and communication test can be effectively accelerated the application of civil communication for urban buildings.
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