TB 9-6625-2309-24
(20) If OFTS calibration software indicates out-of-tolerance condition for TI, perform
b below.
b. Adjustments. Perform adjustments in SECTION IV and repeat paragraph 8.
9. Attenuation Scale Non-linearity
a. Performance Check
(1) Connect equipment as shown in figure 3, Connection A. Connect ST end of
optical fiber jumper cable to LIGHTWAVE MULTIMETER optical input and connect FC
end to FOCUS-SWCM OPTICAL IO (fig. 3).
(2) Adjust FOCUS-SWCM controls as indicated in (a) through (c) below:
(a) Set LD BIAS CURRENT switch to LD PULSED.
(b) Set SWITCHED ATTN switch to OUT.
(c) Adjust VAR ATTN 1 control for approximately -27 dBm optical power
amplitude indication at 850 nm on lightwave multimeter and record indication.
NOTE
When calibrating TD-285C optical module, adjust VAR ATTN
1 control for approximately -38 dBm at 1310 nm and 1550 nm.
(3) Set FOCUS-SWCM SWITCHED ATTN switch to IN.
(4) Adjust FOCUS-SWCM VAR ATTN 2 control for an optical power amplitude
indication on lightwave multimeter 6.0 dBm ( -0.5 dB) lower than recorded in a (2) (c) above.
NOTE
This will produce a nominal 3 dB power level difference when
displayed on TI. Take care not to disturb optical fiber jumper
cable when making measurements or disconnecting fiber
connectors. Excess optical fiber jumper cable length should be
coiled in 6 inch (approximate) diameter loops and taped
temporarily to bench top to avoid unnecessary movement of the cable.
(5) Lock FOCUS-SWCM VAR ATTN 2 control using locking tab on control.
NOTE
Steps which follow test repeatability of switched attenuator.
Referenced attenuation data sheet values will be averaged by
OFTS calibration software.
(6) Set FOCUS-SWCM SWITCHED ATTN switch to OUT and record lightwave
multimeter indication in Power High Ref column on TD-260C (850 nm) Reference
Attenuation Data Sheet (appendix A).
