can anyone plz teach me how to interface a LASER diode with microcontroller . The LASER diode will be used to transmit the output data(in binary format)of microcontroller using an optical fiber .... plz reply asap .... thanx for reading this and for your help .....
Note that it isn't just a question of being able to supply 200 mA, so it isn't enough to have a more powerful buffer chip or transistor.
A laser wants a regulated current, compared to much other equipment that wants a regulatd voltage. A switching transistor just supply or remove supply of a voltage, but leaves it to the consumer to draw as much as it wants/needs at that voltage. A laser needs a current-limiting circuit where you adjust the drive current to how powerful the laser is. That's one of the reasons why so many lasers comes with a little driver board.
Constant current can't be managed by just carefully adjusting the voltage. A minute change to the voltage will result in a huge change in current. And a tiny temperature change will result in a minute change to the voltage of a voltage regulator, resulting in a huge change of current.
So let's repeat the question I asked before. Is this a naked laser diode, where 200 mA is the maximum current allowed or a diode + drive electronics where 200 mA is the maximum current needed?
If it's a naked laser LED, then it does require that the processor turns on/off the power from a constant-current generator, i.e. a circuit with a feedback loop where the voltage gets dynamically adjusted to keep the current stable. Or alternatively - that the laser is driven like a normal LED with a constant voltage and a series resistor, where the resistor is selected so the laser will never manage to draw more than 200 mA. If using a series resistor, then the design must allow enough voltage to burn over the resistor to make it reasonably stable - if too little percent of the total voltage gets burned over the resistor, then a small change in supply voltage will result in a significant change in laser current.