Along with communication’s swift development, the fiber optic communications technology has become the correspondence the important means. The optical fiber transmission system has the capacity to be big, transmitting range far two big superiority. The optical fiber theory capacity may reach 20000GHz, the non-relay transmission distance may amount to 50-80 kilometers.
The light end machine is one kind of equipment which in the fiber optic communications uses, materially is an electrical signal to the light signal, the light signal to electrical signal’s switch. From transmission mode polishing end fuselage for digital light end machine and simulation light end machine two kinds. The digital light end machine is the image which, the pronunciation as well as the data signal must transmit carries on digitized processing, carries on again these digital signal multiplying processing, causes the multi-channel low speed the digital signals to transform a group high speed signal, and this signal conversion light signal. In the receiving end the light signal reduction electrical signal, the return to original state high speed signal decomposes the original multi-channel low speed signal, finally again these data signal reduction image, pronunciation as well as data signal. The simulation light end machine will be the signal which is going to transmit carries on the scope or the frequency modulation will then modulate the good electrical signal to transform the light signal. In the receiving end the light signal reduction electrical signal, carries on again the signal the demodulation, returns to original state the image, the pronunciation or the data signal.
The digital light end machine transmission signal quality is high, has not simulated the frequency modulation, the phase modulation, the amplitude modulation light end machine multi-channel signal with biography time beat interferences serious, easily the environmental effect, the transmission quality inferior, the long lasting work stability bad shortcoming, therefore, the digital light end machine will substitute for the simulation light end machine gradually. At present in the highway, the transportation, electronic police, the monitoring, domains and so on An Fang, industrial automation, electric power, customs, water conservation, bank, light ends machine and so on video image, audio frequency, data, ethernet started the universal massive applications. Figure 1 is a light end machine model application.
TI simulates one of component whole world biggest suppliers, (shown in Figure 2) in view of the digital light end’s machine system requirements, TI provides the complete set high performance the simulation part solution.
Video channel
TI OPAX692/3 and the THS73X3 series video amplifier provides high performance video signal filter shape processing, the difference gain and the differential phase may reach 0.001% separately and 0.01%, may act according to the concrete system requirements to choose a section of appropriate video amplifier. After the TLC55X0 series high performance ADC(8bits,20-40MSPS) transforms the video amplifier processing simulated signal the digital signal, SNR may achieve 46dB. If achieves the higher signal processing and the transmission quality, suggested that uses TI THS1041ADC(10bits,40MSPS), THS1041 to design in view of the video frequency application, its most major characteristic was the interior integrated the clamp function and a gain adjustable amplifier, may see from Figure 2(a), uses THS1041 will be a high integration rate plan, THS1041 SNR may reach 57dB. Regarding DAC, we suggested that uses TI DAC908(8bits,165MSPS) or DACX900(10bits,165MSPS), these two section of DAC also aims at the video frequency application design.
Audio frequency channel
TI provide the comprehensive audio frequency solution, including audio frequency power amplifier, audio frequency A/D/A, digital audio frequency and so on. According to the light end’s machine system requirements (amplifier A/D/A), we recommend use OPAX134/X604 to take the audioamplifier, DRV13X/INA13X take the audio frequency actuation. Audio frequency ADC recommends PCM180X, the audio frequency DAC recommendation uses PCM175X. If uses audio frequency Codec(ADC DAC), we suggest the TLV320AIC3X/2X series.
High speed and string data conversion connection
TI provides the field most competitive high speed and string switch (Serdes). TLK1501/2501/3101(16:1) series provides from 0.5Gbps to the 3.125Gbps speed scope, the power loss is lower than 350mV, the parallel interface is the LVTTL level, the serial interface has CML and the VML level, may dock directly with the majority light/electricity module. If the data quantity is not big, may use SN65LV1023A/1224B(10:1), it provides from 100Mbps to the 660Mbps serial speed, the level is the LVDS level.
System clock
If ring-like cascade’s topology, in each first-level must provide the clock from on first-level high speed data to do for this level master clock, so that overall system’s synchronization, because withdraws from the line the clock vibration is big, generally the need clock vibration eliminates, TI CDC7005 or CDCM7005 are aim at this kind of application specially a section of high performance clock phase-locked loop and have the clock to filter shake the function, regarding this TI had issued a section of special appraisal system (TSW2000), the detailed information may obtain from the TI.com website.
Power source management part
TI provides the comprehensive power source solution, speaking of the light end machine, TI has aims at the power source solution which specially Xilinx and Altera FPGA design.
Chart 2a: Digital light end machine transmitting end (TX).
Chart 2b: Digital light end machine receiving end (RX).
