Research On Small Radio Optic Module Applied To The Distributed Base Station

The distributed base station is a new base station with the rapid development of mobile communications technology.The optical module is an important photoelectric conversion device in the distributed base station,and it is the central module of Radio over Fiber in the application of mobile communications.The ROF technology is a new subject based on photonics and microwave technology.It not only succeed to the high-bandwidth low-loss,anti-electromagnetic interference and other characteristics of fiber-optic communication,but also succeed to the strong flexibility,wide coverage and other characteristics of wireless communication.So it has been widely used in the military and civilian fields.In this paper, application background of optical module in the distributed base station is explained. Optical module is played an important role in present structure of the distributed base station. Then, the optical module principle and application are introduced. The 700MHz frequency range is selected as the work frequency of the optical module in this paper after contrast four frequency range by ITU.This frequency can communicate well in some specal area include high-rise building,underground Parking,So it can cooperate with the present 4G communication. Then the main paremeters and principle are analyzed in the ROF system design. Optical transmission module is designed with the butterfly package laser as light source. On this basis, the small optic transmission module with the TOSA package laser is designed. Integration of the light receiving module is achieved including the photodetector driving circuit, low noise amplifier and attenuator.Finally,the communication performance of this two module are tested.The results show that,the gain flatness of this two optical module are all less than 1.5dB.Then different code rate include 2Mbps,4Mbps,6Mbps,8Mbps of 64 QAM are modulated on the Radio signal to test trasmission Characteristics of this two module,and they all can communicate stability in case of the EVM less than 2%.