Methods of Controlling Laser Drivers: POTs and DACs

Abstract: A laser module designer can use a fixed resistor, mechanical pot, digital pot, or a digital-to-analog converter (DAC) to control the laser driver's modulation and bias currents. The advantages of a programmable method (POT or DAC) are that the manufacturing process can be automated and digital control can be applied (e.g., to compensate for temperature). Using POTs can be a more simple approach than a DAC. There can be a slight cost advantage to using a POT, but this is usually not significant relative to other pieces of the design. Using a DAC can offer advantages, including improved linearity (translating to ease of software implementation and ability to hit the required accuracy), increased board density, a wider range of resolutions, a better optimization range, ease of use with a negative voltage laser driver, and unit-to-unit consistency.
Maxim > App Notes > A/D and D/A CONVERSION/SAMPLING CIRCUITS DIGITAL POTENTIOMETERS
FIBER-OPTIC CIRCUITS

Keywords: laser driver, pots, digital pot, digipot, laser modulation, digital potentiometers, laser modulation, Mar 26, 2002
DS1845, DS1848

APPLICATION NOTE 1010
Methods of Controlling Laser Drivers: POTs and DACs

Abstract: A laser module designer can use a fixed resistor, mechanical pot, digital pot, or a digital-to-analog
converter (DAC) to control the laser driver's modulation and bias currents. The advantages of a programmable
method (POT or DAC) are that the manufacturing process can be automated and digital control can be applied
(e.g., to compensate for temperature). Using POTs can be a more simple approach than a DAC. There can be a
slight cost advantage to u