User`s guide

Performance Tests Performance Tests
74 Agilent 81618A/9A and Agilent 81623B/4B/6B/8B Optical Heads, Fourth Edition
The nonlinearity of the 81626B is not usually tested to the specified power
level of +27 dBm. Instead, limited testing up to +9 dBm is used to test the
electronic circuitry of the 81626B. Above +9 dBm the largest contribution
to nonlinearity is from the absorbing glass filter (which is tested on a
sample basis) that does not change its linearity with time. Thus it is
guaranteed by design that testing the 81626B up to +9 dBm ensures
specification compliance to +27 dBm
NOTE