AK2572 Datasheet, PDF (46/50 Pages) Asahi Kasei Microsystems – APC for Burst Mode Applicable Direct Modulation Laser Diode

ASAHI KASEI
[AK2572]
11. Example of Adjusting Sequence
Adjusting sequence example is shown in Table 11-1.
Table 11-1 Example of Adjusting Sequence (for Continuous mode)
Item
Contents
1 Transition to
Adjustment Mode
After releasing the Write Protection, issue a command to make a transition
into Adjustment Mode via Digital I/F.
2 Set APC_FB in
open-loop operation
Set R_APC_FB_SET=”0” 、 R_APC_FF_SET=”3”, and Bias current and
Modulation current are set to open-loop operation. Output current range of
I-DAC1 (or V-DAC3) for Modulation current and I-DAC2 for Bias current is
set by R_DAC1_GAIN (or R_DAC3_GAIN) and R_DAC2_GAIN respectively.
3 LD power adjustment Set R_MOD_FF (Modulation current) and R_BIAS_FF (Bias current) so that
designated LD power is available.
4-A PDGAIN adjustment
(When to monitor
PDMON-pin voltage)
Adjust PDMON-pin voltage when the designated LD power is output.
Adjust PDMON-pin output voltage to be 1 [V] by R_PDGAIN.
Set R_APC_TRGT (APC target)＝”1 0000” (its center value), and after
making APC setting (R_APC_FB_SET, R_APC_FF_SET, R_MOD_FBRT
and R_BIAS_FBRT when both Bias and Modulation currents are used for
APC_FB setting), jump to “Step 5” in this table.
4-B PDGAIN adjustment Set R_APC_TRGT (APC target)＝”1 0000” (its center value) and R_PDGAIN
(When to monitor
＝ ”00 0000” (23.5dB, Maximum gain), then make APC setting
PDMON-pin voltage is _{(R_APC_FB_SET, R_APC_FF_SET, R_MOD_FBRT and R_BIAS_FBRT}
impossible)
when both Bias and Modulation currents are used for APC_FB setting),
Then APC_FB function is activated and LD power is lowered. Adjust
R_PDGAIN so that LD power reaches a closest amount to the designated
power level, and jump to “Step 5” in this table.
5 APC_FB
Adjust DAC_APC setting value (R_APC_TRGT) so that LD optical power
target adjustment
reaches its designated power level.
6 Read-out of sensed
temperature data
Read out the LSI chip-surface temperature equivalent value (R_TEMP).
7 Calculation of
temperature
characteristic
In order to adjust the temperature characteristic of LD, vary temperature
and repeat “Steps 2 ~ 6” above when adjustment is made at 2 different
temperature points or more and make the look-up table of I-DAC1 (or
V-DAC3) and I-DAC2 with referring the measured data
If the adjustment is executed at single temperature point, make the look-up
table with the measured data and On-chip temperature sensor gain (1.5 ℃
/LSB [Typ.]).
8 Write the adjustment (1) Prepare the data to be written into EEPROM based on LD adjusting data.
data into EEPROM (2) Issue a command to make a transition into EEPROM Access Mode via
Digital I/F.
(3) Write adjusting data into EEPROM.
(4) Verify that correct data is written, by reading out the written data.
9 Transition to
After writing data into EEPROM, issue a command to make a transition to
Self-Operation Mode Self-Operation Mode via Digital I/F. Then the AK2572 automatically initiates
its operation in accordance with the setting data retained in EEPROM.
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< MS0290-E-01>
2004/8