THORLABS APD410 Series, Руководство по эксплуатации

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3 Operating Instruction
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Please note, that coupling losses may occur due to small detector size, which will result in a re-
duced output signal. If angled connectors are used the fiber adapter can be rotated from its ori-
ginal position to check for an improved alignment. For this process use an optical input power
below the saturation power while observing OUTPUT voltage on a digital voltmeter or other low-
frequency measurement device.
The maximum OUTPUT voltage swing is 4.1 V at High-Z termination. Saturation of the
OUTPUT will occur at optical input power greater than CW Saturation Power listed in
specifica-
tions . If necessary, use external neutral density filters or attenuators to reduce the input light
level. Please note that the Avalanche Photodetectors are extremely sensitive to unwanted stray
light. Carefully shielding of the Avalanche Photodetectors from any unwanted light sources is
essential. Common techniques to minimize the influence of stray light include baffling or other
opaque barriers like black cloths, beam tubes or using appropriate band pass filters in front of
the detector.
Attention
The optical damage threshold is 1 mW. Exceeding this value will permanently destroy the
Avalanche Photodetector!
3.1.2 Electrical Output
Thorlabs APD410x Avalanche Photodetectors deliver an OUTPUT voltage, which is a function
of incident light power
P
opt
, detector's responsivity
Â
M
(
l
) at a given wavelength and M factor
(see Typical Detector Responsivity Curves ), and transimpedance gain
G
:
·
Â
M
(
l
) for a given wavelength can be read from the spectral responsivity curves (see Tech-
nical Data ) to estimate the OUTPUT voltage.The M factor (gain) settings range is 10 to
100 (APD410A), 5 to 50 (APD410A2) and 4 to 20 for APD410C at 23°C ambient temperature.
·
The amplifier’s transimpedance gain
G
is 500 kV/A. Please note that OUTPUT voltage is re-
duced by a factor of 0.5 if connected to a 50
W
load.
The maximum output voltage swing of OUTPUT is 4.1 V for high impedance loads (2.0 V into
50
W
). Depending on the wavelength responsivity
Â
(
l
)
of the detector and the M factor, the
amplifier will reach saturation at optical input power greater than CW Saturation Power listed in
specifications. To avoid saturation, keep the output signal below the specified maximum output
voltage.
The output of the APD410x Avalanche Photodetectors is a BNC connector.
The amplifier offset voltage is factory set to zero at 23°C ambient temperature. Due to the very
high transimpedance gain, small temperature changes may affect offset voltage. Therefore it is
recommended to use the Avalanche Photodetectors in a constant temperature environment
after a short warm up period (~5 min) for exact DC light level measurements.
In the appendix, typical curves for Output Frequency Response and Spectral Noise Distribu-
tion can be found.
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