The Application Of Optic-Fiber Communication In Optic-Measure Equipments

The amount of video signals data is the most in photoelectric theodolite data communication system .The video signals are always transmitted by parallel cable so that the setting up and maintain of system are very complicated and electromagnetism disturb by other system is hard .This task is designed to use fiber as the substitute for cable , and transmit 10-route signals of CCD camera and one route text data by one fiber on base of TDM(Time-Division Multiplexing) principle.According to the demand of TDM system and the trait of transmitted Signals , the problem of code adjusting must be dealt with at first.The writing clock and reading clock of transceiver can be adjusted to synchronize by using FIFO which is designed by EAB modulate of programmable logic device FPGA and output signals of FIFO which can be detected as frame sign signals to control output frame signals.For receiving data correctly , another important problem of TDM system is how to realize bit synchronizing and frame synchronizing .This system select integrate chip SY87700L to realize bit synchronizing reliably .At the same time ,the circuit designed by FPGA can detect frame synchronizing signal . In particular ,a protecting circuit is added in this detect circuit for prevent fault synchronizing signal and missing synchronizing signal .In addition,8B10B encoder and 10B8B decoder are designed on base of FPGA for meet with the need for the type of transmission data in fiber communication system.This system designed the most of the circuit by using FPGA ,and realized synchronized multiplexing and demultiplexing for different signals .The most of cell circuit are realized by VHDL(very high speed hardware describe language) that can be extended for application only by programming .As the core device of transceiver system ,the application of DSP also make this system flexible and expands the range of application.