Awesome now I am lost... forward voltage drop has to be taken into consideration, right ? so I should choose resistor value based on:
(supply voltage - forward voltage drop of the LD) / LD planned current
...precisely what I wrote earlier in the thread.
What's more, while temperature has effect on value of resistors I found that the temperature coefficient of most resistors is 0.0050% per 1 deg C. So in other words if the temperature increases by 100 deg C the change in resistance will be 0.5% so way below tolerance of most resistors.
so... who is right ??