OPTICAL TUNABLE FILTER OTF-920
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Principle of Operation
The OTF-920 uses Santec’s unique linear sliding tuning technology. This ensures that the optical
properties of the filter, including bandwidth, insertion loss and polarization dependent loss (PDL) are
all wavelength independent. The filter element is fabricated with a wavelength gradient along its
length. Wavelength tuning is achieved by linearly sliding the filter element in the optical beam. This
tuning method ensures that the optical beam always passes perpendicularly through the filter element
and eliminates the changes in optical properties that would otherwise occur.
The OTF-920 contains two independent optical sliders. The figure above shows a schematic diagram
of this design. A tunable filter element, with a tuning range of 40nm, or a variable attenuator element,
with 20dB attenuation, can be mounted on each slider. Using tunable filters on both sliders a tuning
range of 80nm can thus achieved. The sliders are automatically controlled to provide seemless
wavelength tuning or simultaneous wavelength tuning and power control.
A small portion of the output light is tapped and monitored by a photodetector. This enables accurate
power monitoring, and when the Automatic Power Control (APC) mode is activated the signal is
processed by the CPU to provide automatic power control of the output signal.
CPU
Display
Motor
Motor
IN
PD
OUT
GPIB
RS-232C
Lens
Lens
Communication
Interface
Slider 2
Slider 1
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