Beam walk-off
42
When remapping is required
This mapping depends on the specific hardware configuration (driver, crystal and
cables). If you decide to swap-out any part of your system’s factory configuration
remapping may be required. NKT Photonics suggests you contact our support
team before going forward with this procedure.
Remapping procedure
If the AOTF system configuration is changed and a remapping of the optimum RF
power level is needed, follow the steps in Procedure 5. Perform the procedure for
all wavelengths that you wish to implement.
Caution: Refer to the notice above in “When remapping is required” before you
perform this procedure. This procedure is unnecessary for factory stock systems
using the original supplied hardware.
Procedure 5 Remapping the optimum RF power level
1. Select wavelength.
2. Measure optical power as a function of RF power. This should result in a
curve similar to the one shown in Figure 25.
3. Determine the optimum RF power as the first peak on the curve (see
Figure 25).
4. Select the next wavelength and repeat from step 2.
Beam walk-off
Beam walk-off is a phenomena that displaces the beam alignment of the system
upon a wavelength change. Beam walk-off in the AOTF of the SELECT is a
function of wavelength due to the grating’s first order diffraction.
Reduction in output
power
When using an NKT Fiber Delivery System or similar, the beam output from the
SELECT AOTF is aligned with the FDS optics to achieve optimum light coupling
efficiency. When changing the SELECT output wavelength, beam walk-off may
be pronounced enough to cause the coupling efficiency of the FDS to degrade
considerably.
Realignment When power reduction is due to beam walk-off, realignment is necessary to
restore the optimum coupling efficiency and thus output power. The FDS must
be realigned using the procedures in the NKT Photonics document:
SuperK Fiber Deliver System Product Guide
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