Agilent Technologies 8614 B Series, Руководство пользователя, Страница: 44 / 272

2-4
Using the Instrument
Setting Up Measurements
Operating the Internal White Light Source
For Option 002 only
Option 002 provides a built-in white light source which is a stable, broadband light source for
swept-wavelength stimulus response testing from 900 nm to 1700 nm. The light source is ideal
to perform stimulus-response measurements, and measure photodetector responsivity.
Refer to
“Light Source” on page 3-29 .
N o t e Although the light source’s lamp lasts an exceptionally long time, turn off the light when not in use
to extend the lamp’s lifetime. On the front panel, press System, Optimum, Light Source, Select off.
1 From the front panel, press System > Options > Light Source > Select Off.
Performing Stimulus-Response Measurements
Stimulus-response measurements characterize optical components for loss (or gain) versus
wavelength. You can characterize devices such as couplers, switches, filters, fibers, and amplifi-
ers.
To perform stimulus-response measurements, you must have an amplitude-stable broadband
light source. Although a white-light source provides the widest wavelength input for stimulus-
response measurements, you can also use an LED or the spontaneous emission from an optical
amplifier.
The displayed response is a convolution of the analyzer’s resolution bandwidth and the amplitude
response of the device under test. Because of this convolution, the analyzer’s resolution band-
width affects both dynamic range and the ability to resolve large amplitude changes versus
wavelength. Wide resolution bandwidths increase the ability to resolve large amplitude changes.
You can display two responses at the same time. The output response versus wavelength is dis-
played. The displayed trace shows the ratio of the output power to the input power expressed as
a logarithm (dB).
response (dB) = 10 log(output power/input power)
Making ratioed measurements is sometimes referred to as normalization. Normalized measure-
ments are used to negate wavelength dependencies in the source. The ratio is achieved through
simple trace subtraction using logarithmic amplitude scales. This is possible because of the fol-
lowing logarithmic equality:
log(A/B) = (logA - logB)
1 Connect the Light Source Output to the Monochromator Input using the short 62.5/125 µm fiber.
The standard connector interface is FC/PC.