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Step 3: Calibrating and Adjusting the
1310 nm Circuit
Use the following procedure to make calibration
adjustments to the 1310 nm laser diode circuit and
to calibrate the 1310 nm modulation circuit:
3-1. Adjust the dc power supply to 9 V dc
±0.25 V dc. Connect the supply's positive
lead to BT1; connect the negative lead to
BT2.
3-2. Set up the DMM to measure dc current less
than 300 mA. Connect the DMM's positive
lead to J4-1; connect the negative lead to J4-
2.
3-3. Use a singlemode fiber patch cable to connect
the laser source to the OPM. Set the OPM to
measure 1310 nm.
WCaution
In the following steps, do not exceed
the laser diode's maximum operating
current of 60 mA. Doing so can damage
the laser diode. If the current reaches
60 mA before the optical power reading
reaches -9.2 dBm, clean the ST
connectors or repair the laser source.
3-4. Set the laser source to 1310 nm. Verify that
the laser diode current is less than 60 mA.
WCaution
In the next step, slow the adjustment
rate on R4 as the optical power reading
approaches -14 dBm. If you turn R4 too
quickly, you might overshoot the
-9.2 dBm target and exceed the laser
diode's maximum current of 60 mA.
3-5. Adjust R4 clockwise until the either the
power reading is -9.2 dBm ±0.1 dB or the
current reaches 60 mA. A typical current
value is 15 mA at -9.2 dBm. If the current
reaches 60 mA before the power reading
reaches -9.2 dBm, the laser source requires
repair.
3-6. Turn off the laser source. Disconnect the
current meter. Reinstall the jumper between
J4-1 and J4-2.
Calibration Adjustments for Serial Numbers < 79130000
3-7. With the laser source set to 1310 nm, verify
that the power reading is -9.2 dBm ±0.1 dB.
3-8. Adjust the 1310 nm external potentiometer
(R24) counterclockwise to verify that the
laser source output is adjustable to
-11.2 dBm ±0.1 dB.
3-9. Adjust R24 until the laser source output
reads -10.0 dBm ±0.1 dB.
3-10. While the laser source is on, disconnect the
power supply; then install a 9 V battery.
Verify that the output is still at -10.0 dBm
±0.1 dB.
3-11. Connect an oscilloscope across J4-1 and J4-4
(Gnd). Set the laser source's
switch to the
3-12. Verify that the power reading is -10 dBm
±0.5 dB. Verify that the signal frequency is
2 kHz ±100 Hz with a duty cycle of 50%
±5%.
3-13. Set the laser source's
CW
. Turn off the laser source. Remove the
9 V battery.
Step 4: Calibrating and Adjusting the
1550 nm Circuit
Use the following procedure to make calibration
adjustments to the 1550 nm laser diode circuit and
to calibrate the 1550 nm modulation circuit:
4-1. Adjust the dc power supply to 9 V dc
±0.25 V dc. Connect the supply's positive
lead to BT1; connect the negative lead to
BT2.
4-2. Set up the DMM to measure dc current less
than 300 mA. Connect the DMM's positive
lead to J2-1; connect the negative lead to
J2-2.
4-3. Use a singlemode fiber patch cable to connect
the laser source to the OPM. Set the OPM to
measure 1550 nm.
Service Information Sheet
CW/MOD
MOD
position.
switch to
CW/MOD
5
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