OPTICAL TUNABLE FILTER OTF-920
3-1
3
Features
The Peak Search function provides automatic searching and selection of the wavelength with the
greatest optical power. The function operates by sweeping the filter through a specified wavelength
range whilst continuously monitoring the optical power. On completion of the search the filter
automatically moves to the wavelength with greatest optical power. The Peak Search Function has two
modes. In the standard mode the OTF-920 sweeps through the specified wavelength range in 0.001nm
steps. A peak is thus selected with high accuracy, and by selecting a suitable scan range the function
can even be used to select a single wavelength from a comb of signals. In addition, a Rapid Mode can
also be programmed. In Rapid Mode an initial course wavelength sweep is performed at 1nm intervals
and this is followed by a fine wavelength sweep in 0.001nm steps over a range of
±
1nm from the
detected peak. The Rapid Mode thus enables a rapid scan over a broad wavelength range to be
achieved whilst maintaining the high resolution and accuracy.
3.2. Peak Search Function
3.1. Wavelength Range
The OTF-920 contains two sliders in which the optical filter elements, or variable attenuator elements,
are mounted. The OTF-920 can thus be supplied in a variety of configurations. Please note that it is not
usually possible to change the configuration after manufacture. Each slider has a tuning range of 40nm
for a tunable filter and 20dB for the variable attenuator. The sliders are automatically controlled to
provide seemless wavelength tuning, or simultaneous wavelength tuning and power control. The
following combinations are possible:
•
Identical filter profiles on each slider providing 80nm tuning range, e.g. 1530 - 1610nm.
•
Different filter profiles on each slider, each with 40nm tuning range.
•
One tunable filter and one attenuator providing both wavelength selection and power control.
Optical power monitoring is realized by tapping the optical signal using a coupler behind the filter
element and monitoring this using a photodetector. Compensation for the wavelength sensitivity of the
photodetector is carried out automatically.
3.3. Optical Power Monitor
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