Agilent Technologies 86038A User Manual page 46

Measurement Concepts
Table 3 Maximum RF Modulation Frequency (MHz) for <90° phase steps
∆τ RGD
(ns/nm)
0.1
0.5
1
5
10
50
100
500
1000
5000
10000
50000
46
Maximum RF Modulation Frequency (MHZ)
The following table lists recommended modulation frequencies. Any
modulation smaller than that listed will give correct results (that is, no
phase wrapping). Smaller modulation frequencies will have more noise
and better resolution. Table cells that have an arrow symbol (
that you must decrease the wavelength increment to achieve the desired
∆τ RGD.
0.001 0.005 0.01
any any any
any any any
any any any
any any any
any any 2500
any 1000 500
2500 500 250
500 100 50
250 50 25
50 10 5
←
25 5
← ←
5
Relationship of setup parameters to aliasing
Since all measurements are sampled at discrete wavelengths, there is an
implication of the performance between the sampled points. The
wavelength increment and the RF modulation sideband separation must be
small compared to the wavelength range over which the device under test
has variations of interest.
When a device has periodic variations across wavelength, such as a Fabry-
Perot filter, an interleaver, amplitude ripple, or group delay ripple, the
wavelength increment must be small enough to collect two or more
samples per period. If the wavelength increment is so large that less than
two samples per period are measured, the result will be aliased to an
⁄ ( × ∆τ
f = 1 4
90
∆λ Wavelength Increment (nm)
0.05 0.1
any any
any any
any 2500
1000 500
500 250
100 50
50 25
10 5
←
5
← ←
← ←
← ←
Agilent 86038A Optical Dispersion Analyzer, Third Edition
Description of the 86038A
←
) indicate
× ∆λ )
0.5 1 5
any 2500 500
1000 500 100
500 250 50
100 50 10
50 25 5
←
10 5
← ←
5
← ← ←
← ← ←
← ← ←
← ← ←
← ← ←