User`s guide

Definition of Terms Specifications
Agilent 81689A, 81689B and 81649A Tunable Laser Modules User’s Guide, Third Edition 35
Definition of Terms
This section defines terms that are used both in this chapter and
“Performance Tests” on page 45.
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.
Absolute Wavelength Accuracy
The maximum difference between the actual wavelength and the
displayed wavelength of the TLS. Wavelength is defined as wavelength
in vacuum.
Conditions: constant power level, temperature within operating
temperature range, coherence control off, measured at high power
output.
Measurement with wavelength meter. Averaging time given by
wavelength meter, ≥1 s.
Linewidth
The 3-dB width of the optical spectrum, expressed in Hertz.
Conditions: temperature within operating temperature range,
coherence control off, power set to maximum flat power (maximum
attainable power within given wavelength range).
Measurement with self-heterodyning technique: the output of the
laser under test is sent through a Mach-Zehnder interferometer in
which the length difference of the two arms is longer than the
coherence length of the laser. The electrical noise spectrum of the
photodetector current is measured with an Agilent Lightwave Signal
Analyzer, and the linewidth is calculated from the heterodyne
spectrum (Lightwave signal analyzer settings: resolution bandwidth 1
MHz; video bandwidth 10 kHz; sweep time 20 ms; single scan).
Minimum Output Power
The minimum output power for which the specifications apply.