HP 37718A Installation And Verification Manual page 48

Performance Tests
Self Test
1550 nm Dual Wavelength Tests:
If a Dual Wavelength Optical Interface is fitted, repeat the
CONFIDENCE test with 1550 nm selected.
1 Select 1550 nm OPTICS wavelength
2 Connect 1550 nm OUT to IN via 15dB Optical Attenuator. Ensure the
attenuator is inserted in the OUT port.
3 Run the test.
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