| Along with the quick development of the communication and network technologies, the data communication services and their applications come up one after another, such as the information index and the electronic commerce, all of which developed the vast foreground for data communication. As the amount of data transmission services increases greatly, people also have higher requests to the mutual connection of networks and communication each other and the transmitting speed and quality. But the interface and data rate of some of the special or local area nets, which were set in the past, already can not satisfy the demands today, therefore the problems existing must be resolved urgently. For example, in the bank system, insurance company, the electric power system, etc., the nets build in the past are the 64kb/s DDN(Digital Data Network) special net. Now they all hope to upgrade the data rate to 2 Mbs/s, and use the El net to transmit data in order more easily to implement the mutual connection and communication and to exchange information among the nets of the different departments in the same place and different regions. It is based on such application background and in order to meet a local commercial bank's request of raising the baud rate and reconstructing its net, our company puts forward a project to develop the optical modem which is a kind of new interface device, and hands over it to me to complete.This paper is a technique summary to this project. In it, the present situation of the nets is analyzed. The background of the subject is explained. The principle and the circuit design and the simulation of the optical modem are discussed. The PCB plotting, the device assembly and adjustment, and the test results are presented. Currently the device has already carried through trial evaluation, the result showed that the operation is completely normal. Consequently the task of this project has being completed basically. |
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