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ET-3500AF/ET-4000AF User’s Guide
OPERATION:
1. Caution: Eye safety precautions must be followed when utilizing any equipment used in the vicinity of laser beams. Laser beams may reflect from the surface of the detector or the optical mount and caution must be exercised.
2. Mount the detector to an optical stand by the mounting holes on the bottom of the detector housing.
3. Clean the end of the fiber ferrule and connect to the laser.
4. Connect the detector to the oscilloscope using a coaxial cable designed for 10 GHz operation. The DC Monitor cable can be a general purpose cable.
5. Use the 50Ω termination input of the oscilloscope. If the oscilloscope does not have a 50Ω input, connect the coaxial cable to a 50Ω terminator and connect this to the oscilloscope’s 1MΩ input.
6. Connect the DC Monitor to a high impedance device, such as a multimeter. Set the device to millivolts or volts. The output of the DC Monitor
converts the average photodiode current to a voltage output of 1 mV/uA. The DC Monitor output has an offset voltage of less than 2 mV.
7. After being certain that the damage threshold of the detector is not exceeded, turn on the laser.
TROUBLE SHOOTING:
A. No signal is seen the first time the detector is used.
1. Is the power switch on? Is the external power supply connected?
2. Is your signal a cw signal? If so, there will not be a signal output present because the detector is AC coupled. There would be an output from the DC Monitor.
3. Be certain that the signal is not high off scale on the oscilloscope.
4. Is the wavelength of the laser within the spectral range of the detector?
5. Has a 50Ω termination input been used?
6. Make sure fiber radius is greater than 1 inch. Inspect fiber for damage.
7. Check the end of the fiber ferrule for cleanliness or damage.
8. Is there enough light (see sensitivity spec on the data sheet) incident on the detector to generate a signal?
B. A signal has been previously obtained, but not currently:
1. Try steps listed under A.
2. Recheck if voltage is present at the external power supply plug.
C. Increasing the power incident on the detector does not result in a higher voltage signal on the oscilloscope:
1. The detector is probably saturated. You should lower the power incident on the detector to a level below the saturation point.
A NOTE ABOUT THE EXTERNAL POWER SUPPLY:
The external power supply is a 5 VDC, regulated supply with a positive center pin. Using an unregulated power supply or any supply other than 5 VDC could damage the detector.
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