ONET4201LD output auto power control minimum value

The minimum bias and modulation currents are specified when the disable pin is set to HIGH or if a fault occurs. This is a maximum of 25uA for bias current and 25uA for modulation current.

If the external resistors RAPCSET and RMODSET are being used to reduce the current, this may not sufficient to achieve low optical output power (< -20 to 30dBm).

It can be seen from figures 15, 16 and 17 in the datasheet, that with high value resistors, there will be some small amount of bias and modulation currents. The best way to reduce the optical power is to use the transmit disable function.

Dear Alex:

  Thanks for your reply.

I used IPAD=18uA to calculate output power that  is only -4.4dBm by equation 7 of datasheet.

Is it right?

If , yes, it means output power minimum is -4.4dBm, right?

Thomas,

This is not correct. The 18uA is the minimum recommended input to the PD pin for normal operation.

The minimum power will be less than -4.4dBm. The minimum power will occur when RAPSET and RMODSET are set to a large value like 100kohms. However, this may not be sufficient to achieve the off power required by the customer. In this case, the Tx disable should be set to high.

Regards,

Alex.