THORLABS SIR5-FC User manual

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HIGH-SPEED PHOTODETECTOR
Thorlabs item # SIR5-FC
Serial #____________

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SIR5-FC PHOTODETECTOR
TECHNICAL DATA
Wavelength Range 900 – 1650 nm
Detector Material InGaAs
Detector Diameter 80
μ
m
Bandwidth (-3 dB point) >5 GHz
Rise and Fall Time <70 ps
Afterpulse Ringing <20% of Maximum
Dark Current <1.5nA @20V
Junction Capacitance ~0.3pF @20V
NEP 2x10E-15 W/sqrt(Hz)
Dynamic Range Calculate from NEP and 1V maximum output into 50 Ω
Fiber Input Receptacle FC
Output Impedence 50 Ω
Typical Peak Optical Input Power for a 2 V output
(Okay to increase to achieve a full 2 V output)
20 mW
Maximum Safe Output Voltage 1 V
Battery Power Supply 20 V
Battery Shelf Life 190 mAh of stored charge, lifetime depends on signal rep-rate,
t
Dimensions 25 x 25 x 38 mm

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OPERATIONAL INSTRUCTIONS FOR THE PHOTODETECTORS
SIR5-FC, SV2-FC, AND SUV7-FC
•Inject the radiation to be analyzed into a 50 μm fiber. Keep the energy and power of the
radiation below the damage threshold of the fiber tip/volume.
•Attenuate the peak power of the optical pulse exiting the fiber to less than 20 mW. NOTE: If
the photodetector input is greater than 20 mW, the detector may be damaged, and the
warranty will not apply.
•Connect the photodetector to an oscilloscope using a high-bandwidth SMA adapter. Using
cables or low-bandwidth adapters will significantly degrade the quality of the measurement.
•Slowly insert the FC fiber connector into the photodetector fiber receptacle while watching the
electrical signal on the oscilloscope. The maximum value of the signal must be lower than 1V
into 50 Ω. Attenuate at the fiber input until the fiber connector can be completely inserted into
the receptacle without exceeding 1V.
•Upon completion of measurements, disconnect the fiber from the photodetector, or block the
fiber input to prevent unnecessary drain on the batteries.
•Always use protective plastic caps for the fiber connectors and photodetector receptacles.
Note about Battery Lifetime
When using battery operated photodetector packages it is important to realize the limitations on the battery life.
Photo detectors are current output devices, meaning that the output current is directly proportional to the light
hitting incident on the detector. Most users will convert this to a voltage by applying a load terminating resistor.
The resistance value is essentially the circuit gain. For very high speed detectors, such as the SIR5, SV2, and
SUV7, it is very important to use a 50Ωterminating resistor to match the impedance of standard coax cables to
reduce cable reflections and improve overall signal performance and integrity. Most high bandwidth scopes
include this termination.
Since the detector is a current device, this directly correlates to the battery usage lifetime. Most battery
manufacturers provide a battery capacity in terms of mA hr. The battery used with these detectors is rated for
190mA hrs. this means that it will reliably operate for 190hr at a current draw of 1mA. Below is a quick example
of how to determine batter lifetime:
Let’s assume a 1550nm light source with an average 1mW power is applied to an SIR5. The responsivity of a
biased photodetector at this wavelength is 1.0 A/W as shown in the response curve above. From this the photo
current can be calculated as 1.0 A/W * 1 mW, or 1.0 mA. If the battery used to power the biased photodetector
has a specified capacity of 190 mAhrs, as the SV2 does, then the battery will last 190 mA hrs / 1.0 mA, which
equals 190 hrs (8 days) of continuous use. By reducing the average incident power of the light to 10 uW the

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same battery would last for about 2 years when used continuously. For these high speed detectors a 50Ω
terminating load is recommended for best performance. Continuing the example above, the 1.0mA photo
current will be converted to a voltage as 1.0mA * 50Ω, or 50mV. The 10μW power level will produce on output
voltage of 10μA * 50Ω, or 0.5mA. For some measurement devices this signal level may be too low and a
compromise between battery lifetime and measurement accuracy will need to be made.
As a result, when using a biased photodetector with a battery powered source it is beneficial to use as low of
light intensity as is reasonable for the application. It is important to remember that a battery will not immediately
cease producing a current after it has supplied its specified number of mAhr; instead, the terminal voltage of
the battery will drop below the rating of the battery. A drop in the terminal voltage of the battery will lower the
electric potential being applied to the photodiode. This in turn will increase the response time of the detector
(lower the bandwidth of the detector). As a result, it is important to make sure that the battery is operating
within its specified parameters in order to ensure the proper functioning of the biased photodetector. The
battery can be tested by following the procedure described in the specifications sheet for the detector.
Another suggestion to increase the battery lifetime is to remove, or power down the light source illuminating the
sensor. Without the light source the photodetector will continue to draw current equal to the photodetector dark
current, however this will significantly increase the lifetime. The SIR5 has a dark current less than 1.5nA, will
not significantly impact the battery life.
For applications where a DET series photodetector is being continuously illuminated with a relatively
highpower light source or if having to change the battery is not acceptable consider using the DET1A adapter
for that allows the photodetector to be powered using the LDS2 power supply. The drawback to the DET1A is
that noise in the line voltage will contribute to noise in the output signal of the DET series detector.
Warranty Information and Technical Support
All high-speed photodetectors are under warranty for 12 months. During this time, Thorlabs
will accept return and repairs free of charge for all problems, provided the customer operates the unit
within our specifications. Replacement batteries are available directly from Thorlabs, part # SBP20.
The average time for repair and returns is 2 weeks.
You may use any of the following methods to contact Thorlabs in case of difficulty or if you
have questions regarding your photodetector.
[email protected] You can send a detailed email message and one of our application
engineers will respond promptly (within 1 business day).
Fax: [phone]
Phone: [phone]

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3 STEPS TO CHANGE THE BATTERY PACK

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Model Number: __SIR5-FC___________________________________ Serial Number: ________________________
Thorlabs does hereby certify that the above equipment meets or exceeds our published specifications for performance
and accuracy. All test results specific to the above unit are shown below.
Tested and Approved by: ______________________________________________ Date: ______________________