LS-1310/1550
Laser Source
6
W
Caution
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.
4-4.
Set the laser source to 1550 nm. Verify that
the laser diode current is less than 60 mA.
W
Caution
In the next step, slow the adjustment
rate on R14 as the optical power reading
approaches -14 dBm. If you turn R14 too
quickly, you might overshoot the
-9.2 dBm target and exceed the laser
diode’s maximum current of 60 mA.
4-5.
Adjust R14 clockwise until either the power
reading is -9.2 dBm ±0.1 dB or the current
reaches 60 mA. A typical current value is
25 mA at -9.2 dBm. If the current reaches
60 mA before the power reading reaches
-9.2 dBm, the laser source requires repair.
4-6.
Turn off the laser source. Disconnect the
DMM. Reinstall the jumper between J2-1
and J2-2.
4-7.
With the laser source set to 1550 nm, verify
that the power reading is -9.2 dBm ±0.1 dB.
4-8.
Adjust the 1550 nm external potentiometer
(R35) counterclockwise to verify that the
laser source output is adjustable to
-11.2 dBm ±0.1 dB.
4-9.
Adjust R35 until the laser source output
reads -10.0 dBm ±0.1 dB.
4-10.
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.
4-11.
Connect an oscilloscope across J2-1 and J2-4
(Gnd). Set the laser source
CW/MOD
switch
to the
MOD
position.
4-12.
Verify that the power reading is -10 dBm
±0.5 dBm. Verify that the signal frequency
is 2 kHz ±100 Hz with a duty cycle of 50%
±5%.
4-13.
Set the laser source
CW/MOD
switch to
CW
.
Turn off the laser source.
Step 5: Reassembly and Final Test
5-1.
Remove the singlemode cable from the laser
source. Put the dust cap onto the laser source
optical ST connector.
5-2.
Apply insulating varnish, such as red GLPT,
to all potentiometers adjusted.
5-3.
Put the board back in the case. Put the case
halves together and install the four Phillips
screws. Reinstall the lock washers and nuts to
the CW/MOD and 1550/1310 switches.
Install a 9 V battery and the battery door.
5-4.
Run the performance tests as described in the
earlier section "Performance Tests".
Calibration Adjustments for Serial
Numbers
≥
79130000
(For earlier serial numbers, see page 3)
To ensure that the laser source performs to
specifications, calibrate it annually using the
procedure that follows.
Always perform the complete calibration
adjustment procedure.
Step 1: Preparing for Calibration
Before you start the calibration procedures
described in this sheet, do the following (refer to
Figure 2 for locations of components on the circuit
board):
1-1.
Turn off the laser source.
1-2.
Remove the battery door and the 9 V battery.
1-3.
Remove the four Phillips screws from the
back of the laser source. Remove the top case.
1-4.
Unscrew the external retaining nuts from the
laser source's power switch and
CW/MOD
switch.
1-5.
Carefully remove the laser source circuit
board from the bottom case. Take care to not
strain the fiber that connects the circuit board
to the ST connector mounted in the bottom
case.