Secret Ethernet optical wireless communication drive circuit diagram

Posted on Dec 11, 2010

Ethernet is the most widely used networking technology with high reliability, media informative, easy to expand and update, etc., in businesses, schools and other fields are wi

Secret Ethernet optical wireless communication drive circuit diagram
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dely used. According to the standard IEEE802.3 Ethernet specification, each Ethernet coaxial cable length should not exceed 500m, through the repeater interconnection network shall not exceed the maximum distance 2.8km. In this case, the wireless communications using laser technology, beyond the geographical limits of Ethernet data communication needs, has a strong practical value. Modulation driving circuit design 6 is a circuit diagram of a modulation drive, mainly by MAXIMs MAX3263 chip and internal 155MHz with monitor diode laser LD constitution. MAX3263 main internal bias supply provides temperature compensated bias and reference voltage output Vref1 and Vref2, through a resistor R25, R26, R27 and R28 of the internal high-speed modulation driver circuit, laser diode and monitoring program. MAX3263 output current are inside the mirror current source control, the current mirror has 2Vbe junction temperature drift, the reference voltage is set at 2Vbe, junction temperature drift can be canceled. Select resistor R28 to adjust the laser bias current quiescent Ibo, Ibo make slightly less than the laser threshold current, so that the output of the laser has a good extinction ratio. LD internal monitor diode can light intensity change is converted to a current Ipin, the feedback current generated by the internal conversion Ibs, by the formula Ibo 40 (Ib + Ibs), light intensity change is converted into a portion of the laser bias current, feedback on laser, to ensure stable output optical power. Differential PECL signal RD input from the internal high-speed input buffer and output common-emitter differential-component modulator modulates the size of the modulation current is determined by the R26 current Im decision. Select R26 size, make appropriate laser modulation current, sufficient output optical power, and has a good extinction ratio. At the same time should be OUT +, OUT- terminal voltage at 2.2V or more to prevent the laser saturation. Because of Figures 6 and 7 are in the main chip 155MHz or more, so by the two circuit transceiver circuit, careful parameter selection and PCB design can be applied to high-speed optical communications applications. 5 system test on the basis of various parts of the design, the linking them, in the absence of optical antenna conditions, successfully conducted experiments indoor laser wireless Ethernet communication. Improve the system now, and ready to be used in optical networks.

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