Design Of Extended Reach And Multi-rate CWDM SFP

Optical fiber communication has become a major means of transmission in the modern information network, with the communication capacity continuous improvement and development of communication networks, the demand of optical transceiver modules have increased by magnitude, advancement, reliability and economy of optical modules will also directly affect the entire network system equipment and the vitality and market competitiveness, especially for those modules which apply in CWDM system and can transmit long distance with multi-rate. At the same time in order to meet the demand of the communication link management, the optical transceiver module with digital diagnostic function has become increasingly common, and its technology has gradually been matured, through monitor parameters of modules, can help find fault locations faster, reduce fault repair time. Management efficiency of the communications network can be improved and system maintenance also can be easier.This paper is under the background of "Design of 2.5Gbit/s CWDM SFP ", which is the project of Shanghai Oplink Communication Technology Co., Ltd. Wuhan Branch. It first introduces the background and the development direction of optical transceiver, and then briefly introduces the electrical interface of MSA agreement and storage unit, monitoring parameters and calibration methods of SFF-8472 agreement, then introduces work principle of the parts, CWDM technology, laser driving way and coupling mode, analyses main chips selection in detail, introduces the main circuit design of the module's transmit and receive parts, especially Digital Diagnostic Monitoring technology which includes transmit and receive optical power calibration, Best APD bias Voltage's search and its temperature compensation technology, extinction ratio compensation technology. Finally, the article introduces the test of the SFP transceiver, including the optical power, extinction ratio, the dispersion, receive sensitivity, LOSS alarm and jitter performance and so on. The SFP optical transceiver module designed in the paper can meet the design target, it also meets the MSA agreements and SFF-8472 agreement, can transmit in various rates from 155Mbps to 2.5Gbps, it supports 32dBm optical link power budget, and can transmit signal through 100km optical fiber with the receiver sensitivity meets the design target and dispersion can be controlled in the range. To verify the performance of the module, after repeated testing of high temperature and low temperature, the indicators include the light eye, extinction ratio, optical power, receiver sensitivity, and digital diagnostic monitoring parameters can all meet the design requirements.