Using the OSICS DFB Module
86
OSICS User Manual
8.5.5
Setting Up Analog Modulation With the Internal Sinus
Modulation
Subject
Sinus Modulation is an internal modulation feature implemented on the DFB module and
designed to limit the effect of Brillouin scattering.
The DFB module can generate a sinusoidal signal with a user-defined frequency in the
range of 10 kHz–100 kHz and a user-defined modulation-rate in the range of 0%–15% (of
the diode current value) to modulate the current of the diode.
The following figure shows the resulting sinusoidal modulation of the laser diode bias-
current for a given modulation rate (< 15%) and frequency. The new diode current
fluctuates symmetrically around the original value of the bias-current (I
bias
).
I
bias
is the mean average of the new modulated current.
Figure 57: Diode current resulting from sinusoidal modulation
8.5.5.1
Specifying the Sinus Frequency
Subject
To use the Sinus frequency, you must first set the internal frequency (in the range 10 kHz–
100 kHz). The frequency unit cannot be modified; it is defined in kHz.
Procedure
1.
Access the DFB
Unit Setup
menu (see section
Accessing an OSICS Module Setup
).
2.
Expand the
Sinus Modulation
menu and enter the
Set Frequency
sub-menu.
The
Set Sinus Frequency
sub-menu appears and displays the current frequency of
the sinus modulation signal.
I
bias
Max. Rate = 15 %
Time
reference
Diode current
