User`s guide

Specifications Definition of Terms
24 Agilent 81618A/9A and Agilent 81623B/4B/6B/8B Optical Heads, Fourth Edition
Definition of Terms
This section defines terms that are used both in this chapter and
“Performance Tests” on page 37.
Generally, all specifications apply for the given environmental conditions
and after warmup time.
Measurement principles are indicated. Alternative measurement
principles of equal value are also acceptable.
Linearity
The linearity error is defined as the relative difference between the
displayed power ratio, D
x
/D
0
, and the actual (true) power ratio P
x
/P
0
caused by changing the displayed power level from the reference level, D
0
,
to an arbitrary displayed level, D
x
. Symbol N.
if expressed in %
if expressed in dB
Conditions: reference level 10 µW, displayed power levels within the
specified range, zero less than specified time prior to measurement.
Note 1: ideally N = 0 %, respectively 0 dB.
Note 2: the power-dependent nonlinearity, N(P
x
), can alternatively be
expressed by the following formula:
where r(P) is the power-dependent responsivity (for a power meter, the
responsivity is defined as the ratio of displayed power to actual input
power).
N
D
x
D
0
⁄
P
x
P
0
⁄
---- ---- ----- ----- 1Ð


100()=
N
dB
10
D
x
D
0
⁄
P
x
P
0
⁄
----- ---- ---- -----


log=
NP
x
()
rP
x
()rP
0
()Ð
rP
0
()
---- ---- ---- ------- ---- ---- ------- --=