I want to drive a DFB laser in a type-2, 14-pin butterfly package. The manufacturer has provided limited information on how to bias the laser diode and could not get any information on the reference or test circuit.

The laser diode's anode is connected to the case ground. I need to DC bias the cathode with a voltage of 2V at a maximum of 200mA current using a constant current source to drive the laser without damaging it. And, I do not want to monitor its output with the internal photo diode. I just want to bias the laser diode.

I have been researching for some circuits, they are either using LM317 or very complex circuits using integrated ICs with additional controls and functionalities.

I am looking for a very simple circuit to bias my laser. Please help!

Datasheet: http://ao-inc.com/images/uploads/products/01-05-1347_DFB-XXX-BF-XX-CW-FX-HX-N347_REV_001.pdf

  • \$\begingroup\$ The information you have are not sufficient for the task: you can bias the laser diode by any current source, but if you do not know what is a safe value for the anode current, you'll probably destroy it in few seconds. \$\endgroup\$ – Daniele Tampieri Mar 7 '19 at 11:36
  • \$\begingroup\$ @DanieleTampieri what information should I additionally post in the question? \$\endgroup\$ – Ganesh Mar 7 '19 at 11:44
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    \$\begingroup\$ I think you need features and monitoring. The manufacturer put a photodiode in there to monitor optical power. They put a thermistor in there to monitor temperature. They put a thermoelectric cooling device in it to cool it. I don't think they put all of that in there because it isn't needed. \$\endgroup\$ – JRE Mar 7 '19 at 12:49
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    \$\begingroup\$ Not using the internal photodiode is asking for trouble. Did they ship you a photodiode calibration value with the device? \$\endgroup\$ – Andy aka Mar 7 '19 at 12:56
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    \$\begingroup\$ @pericynthion, If you use an external photodiode for laser current control, you'd better be careful nobody ever disconnects the output fiber. Ideally you'd have the components needed for feedback fusion spliced on to the output fiber rather than connectorized. \$\endgroup\$ – The Photon Mar 7 '19 at 18:37

I have found an application note on Current Sources for Fiber Optic Lasers, Application Note 90 by Jim Williams of LTC.

The Grounded Anode Current Source circuit is suitable to drive my laser. The circuit also has current limiting, over-voltage protection, and self enable (for slow start). And I have designed a circuit using MAX1979 to control the internal TEC temperature. These two should ensure proper current and temperature control required for the safe operation of my laser.


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