HP 8163A Series, User Manual

Page: 97 / 207

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Tunable Laser Sources
What is a Tunable Laser ?
5.1 What is a Tunable Laser ?
A tunable laser is a laser source for which the wavelength can be
varied through a specified range. The Hewlett-Packard Tunable
Laser modules also allow you to set the output power, and to choose
between continuous wave or modulated power.
5.2 How to Set the Power
The laser output can be either:
• a continuous wave (CW) signal, fixed amplitude signal, see
“How to Set the Output Power of a CW Signal” on page 98,
• a modulated signal, see “How to Modulate a Signal” on
page 116, or
• a signal with increased linewidth (coherence control), see
“How to Increase Linewidth” on page 122.
If [M
OD
S
RC
] is <O
FF
>, a continuous wave signal is the chosen
optical output. A continuous wave signal is the default.
If any other [M
OD
S
RC
] source is chosen, the chosen source
modulates the signal. For possible modulation sources, see “How to
Modulate a Signal” on page 116.
A t t e n u a t o r If your tunable laser has an in-built optical attenuator, there are two power
modes for the fixed-amplitude, the modulated, and the increased-linewidth
signals. You can either:
• specify the output power (<A
UTOMATIC
> Attenuation Mode), the
instrument automatically sets the current through the laser diode and the
attenuation to output the power you specify, or
• specify the output power and the attenuation (<M
ANUAL
A
TT
.> Mode)
The two modes are separate, the values set in in one mode do not affect
values set in the other.