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ONET4291VA: VCSEL Bias / Modulation Formula

Mitchell
Expert 4915 points
Part Number: ONET4291VA

Hi Team,

I have one quick question on the ONET4291VA. I'm assuming typical VCSEL bias/modulation formulation for this driver IC is logic LOW=  Ibias-Ithreshold, logic HIGH = Ibias+I_modulation - Ithreshold. Is this correct?

Other definitions of modulation has logic LOW =  Ibias-I_modulation/2 - Ithreshold, logic HIGH = Ibias+I_modulation/2 - Ithreshold. 

The datasheet does not really say which.

Thanks,
Mitchell

  • 0
    TI__Guru* 93670 points
    Hi Mitchell,
    Please note figure 1 of the ONET4291VA data sheet. If you look at it single ended, then DOUT+ or DOUT- is the same as what you have mentioned( logic LOW = Ibias-I_modulation/2 - Ithreshold, logic HIGH = Ibias+I_modulation/2 - Ithreshold). On the other hand, if you look at it differentially then your first equation is correct.
    Regards,,nasser