Fiber Coupled Laser Source
Chapter 7: Maximizing the Stability
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2288-D02
Chapter 7 Maximizing the Stability
The benchtop laser source provides the ability to control not only the output power of the fiber coupled laser
diode, it also allows for the precise control of the temperature at which the laser is operating. These two controls
can be used to tune the fiber coupled laser diode to an optimum operating point, providing as stable an output as
possible. The following graphs are from an OSA and a typical S3FC1550 laser.
75% Current, 1547.993 nm
80% Current, 1548.834 nm
85% Current, 1548.834 nm
90% Current, 1548.839 nm
95% Current, 1548.839 nm
Figure 5
Wavelength vs. Power Plots – Variation in Current
Figure 4
shows the effect of changing the operating current of the laser while maintaining a fixed operating
temperature (in this case 24.5 °C). The first plot corresponds to a drive current of 75%. Notice the broad line
width, the laser is not optimized but the output will appear to be stable. The next plot is at 80%. The laser is
approaching a stable point but the second mode indicates the laser is not yet stable.
The laser will randomly mode hop, shifting the power from one peak to another resulting in erratic performance
and power output. In the third plot, the current is at 85% and shows a typical optimized DFB output: a single, very
narrow line width and very stable power. The last two plots, taken at 90% and 95%, show the laser passing
through the optimum point and starting to ebb again.
