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Measuring Coherence Length
Measuring Coherence Length
Coherence length is a measure of the distance over which a laser’s light retains
the phase relationships of its spectrum. The Agilent 86120B measures coher-
ence length of Fabry-Perot semiconductor diode lasers. The Agilent 86120B
cannot measure coherence length of light emitting diodes (LEDs) or distrib-
uted feedback (DFB) lasers.
When you select coherence length measurements, the Agilent 86120B dis-
plays the following four values:
• Coherence length (Lc)
• Round trip optical length of diode laser cavity (2nLd)
•Alpha factor
• Beta factor
Coherence length in the region of 1 mm to 200 mm can be measured. The fol-
lowing figure shows a coherence length measurement.
To measure coherence length
1
Press the front-panel
Preset
key.
2
Press
Appl’s
and then
COH LEN
.