Real-Time Digitized Fiber-Optic Transmission Scheme Based On FPGA

In order to meet the real-time control in systems with high isolation demanding applications, a new and efficient scheme of digitized fiber-optic transmission is proposed. In this scheme, an FPGA unit is used to process and encode sampled signals in ADC, and optical fiber is used to send signals to signal processing unit. At the end of the fiber, another FPGA receiver unit recovered the original signals. The system has merits of stable and good real-time performance. The method is reliable for real-time multi-point sampling data transmission with long-distance under disturbing environments.The system is divided into two parts by the fiber, transmitting part and receiving part. The transmitting part mainly includes an analog-digital converter and an FPGA unit. The A/D converter digitizes input analog signals, then FPGA, processes the digital signals. The processing consists of two aspects: first, making a custom transmission protocol, with which the receiving part can exactly extract and recover original signals, second, encoding the transmission protocol so that the signals can be transmitted by optical fiber. Moreover, FPGA is also in charge of controlling the A/D converter. The encoded protocol, which contains the effective signals, is transmitted by the fiber to receiving part, where another FPGA unit decodes the protocol and restores the effective signals which could be used in subsequent circuits. Because the signals are transmitted by a single fiber, it is a must to extract the synchronous clock from the signals before decoding so that the receiving part can follow the synchronous clock when processing signals. In addition, using a D/A converter to convert the effective digital signals into analog signals, in order to compare this output analog signals with the original input analog signals to observe whether the effective digital signals are correct.The article firstly introduces the main composition of the digitized fiber-optic transmission system and the function of each module circuit, then discusses in detail the hardware design and software design of both the transmitting part and the receiving part. The hardware design is introduced from the following three aspects, the structure of hardware circuits, selection of devices and the design of each module circuit. The introduction of software design includes programming methods, the programming flowchart and the simulation results figures. Finally taking one channel signal as an example, the paper gives the experiment waveforms of main signals and analysis of experimental results. The time delay of signal acquisition and transmission is less than 1.5μs, which indicates a good real-time performance of this system. Besides, the system also has good stability, low Bit Error Rate and strong anti-jamming ability. Results of experiments verify the effectiveness and feasibility of this scheme.