Research And Design Of Digital Signal Processing In Optical Fiber Distribution System

The optical fiber distribution system is a comprehensive indoor and outdoor solution, combining 2G, 3G, and 4G network. It's supposed to realize the seamless combination of indoor and outdoor wireless coverage, which can enhance the quality of coverage. Multi-stantard signals introduced to the system are digital signal processed, transported via fiber optics, and finally sent out.Fiber distribution system directly couples base station signals, and transports them via digital fibers.The system consists of digital access control unit and digital RF remote unit. Downlink signals are coupled to the master unit from mobile communicatio base station, and converted to IF signals by down-coversion module, and coverted to digital signals by AD converters. After that they are converted to frame format suitable for standard access protocol by baseband signal processing unit,and transported to the Remote Unit with the help of digital fiber transceiver and digital fiber.And then the Remote Unit transports baseband digital signal to the baseband signal processing unit by digital fiber transceiver. The baseband data is recovered and then converted to IF signal by DA converter, and converted to RF signal by upconversion module. Finally it's amplified by power amplifier, and sent out to covering area via user antenna. The uplink signals from end users are received by the Remote Unit, and then transported back to base station by applying the inverse process.This article mainly studies the digital signal processing part in the optical fiber distribution system, especially the digital processing hardware design.In In optical fiber distribustion system, FPGA device is used for realizing digital signal processing function, including data acquisition, data mixing,data conversion, data filtering and signal contro. The signal data after conversion is transported to DAC device. The main modules of the DSP software are clock processing module, ADC module, DDC and DUC module, CPU interface module, ALC control module, TD-LTE synchronization module, power detection module, and optical interface module. And this article put emphases on the DDC and DUC module and TD-LTE synchronization module. After simulation debugging, software coding, and system testing andverification, based on DSP technique,the optical fiber distribution system has the benefit of large dynamic, and low noise,which meets the application requirement of multi-standard signal remote coverage, resolving indoor and outdoor multi-standard signal coverage problems.