How to measure DFB-LD (LW = 5MHz) frequency deviation per unit drive current change (in mA)?

Hello,

Another way you could do this if you don't have access to either a wavemeter or stable reference laser is to scan the laser across an interferometer with a known free spectral range with several peaks in the tuning range. Finding the frequency deviation is then just a matter of counting the number of fringes that go by as you tune the laser, then multiplying by the free spectral range to get frequency change. This solution won't give you the center frequency of the laser, just the relative change. One nice aspect of this approach is that it can be done both slowly or at high rate with a current chirp. At high rate, you can use this approach measure the dynamic response of the laser (ie, see it tune faster/slower during a linear current ramp) and calibrate accordingly.
If you lack an interferometer with a short enough FSR, you can build a Fabry-Perot with two optical half-mirrored flats or wedges and a detector. That way you can make the FSR as short as you like, though you'll need ~1.5 m for a 100 MHz FSR, and alignment will be a fun exercise.
Thanks

Another way you could do this if you don't have access to either a wavemeter or stable reference laser is to scan the laser across an interferometer with a known free spectral range with several peaks in the tuning range. Finding the frequency deviation is then just a matter of counting the number of fringes that go by as you tune the laser, then multiplying by the free spectral range to get frequency change. This solution won't give you the center frequency of the laser, just the relative change. One nice aspect of this approach is that it can be done both slowly or at high rate with a current chirp. At high rate, you can use this approach measure the dynamic response of the laser (ie, see it tune faster/slower during a linear current ramp) and calibrate accordingly.
If you lack an interferometer with a short enough FSR, you can build a Fabry-Perot with two optical half-mirrored flats or wedges and a detector. That way you can make the FSR as short as you like, though you'll need ~1.5 m for a 100 MHz FSR, and alignment will be a fun exercise.