THORLABS DET02AFC Operating Manual

PO Box 366, 435 Route 206N, Newton, NJ 07860
Ph [phone], Fax [phone], http://www.thorlabs.com

DET02AFC Operating Manual — Fiber Input Si Photodetector

Description:

The DET02AFC is a ready-to-use, high-speed Si photodetector for use with FC/PC connectorized fiber optic cables
in visible wavelength optical systems. The unit comes with an FC/PC bulkhead connector, detector, and 12V bias
battery enclosed in a compact aluminum housing. The FC/PC connector provides easy coupling to fiber-based light
sources. The output uses an SMA jack to minimize size and maximize frequency response. The bandwidth is

1.2GHz and will operate over the spectral range of 400-1100nm. A NIR version, the DET01CFC, is also available
and operates in the 800-1700nm spectral range.

The DET02AFC includes one #8-32 tapped mounting hole with a 0.25″ mounting depth, while the DET02AFC/M has
one M4 tapped mounting hole with a 6.35mm mounting depth. A 12V A23 battery is included.

Specifications*:

Detector: Si PIN

Active Diameter: Ø0.25mm

Wavelength Range (λ):

Peak Wavelength (λp):

Peak Response [typ, ℜ(λp)]:

Input: FC/PC fiber connector

Rise Time (tR): 50ps (typ)

Fall Time (tf): 250ps (typ)

Ball Lens Size: Ø0.059″ (Ø1.5 mm)

Diode Capacitance (CJ): 0.94pF (typ)

Min Load Resistance:

Damage Threshold: 18mW

*All measurements performed with a 50Ω load unless stated otherwise.

1. Into high impedance. Max voltage is dependent on battery voltage. New batteries typically show 12-13V, while drained

batteries show 9V or less.

2. Calculated range based on peak responsivity and damage threshold.

3. Measured with specified bias voltage.

400-1100nm

730nm (typ)

0.46A/W (typ)

50Ω

Output Voltage1 (Hi-Z): 0-10V

Output Voltage2 (50Ω): 0-410mV

Output: SMA (DC coupled)

Dark Current3 (ID): 50pA (500pA max)

Shunt Resistance (Rsh): 20GΩ

Weight: 0.18lbs

Storage Temp:

Operating Temp:

Battery: A23, 12VDC, 40mAh

NEP (730nm):

Bias Voltage (VR): 12V

0-40°C
0-40°C

9.5x10

-15

W/√Hz (max)

Figure 1

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Operation

Thorlabs’ DET series is ideal for measuring pulsed and CW light sources. The DET02AFC includes a reversed­biased PIN photodiode, and a bias battery packaged in a rugged housing. The SMA output signal is the direct
photocurrent out of the photodiode anode and is a function of the incident light power (P) and wavelength (λ). The
spectral responsivity [ℜ(λ)] can be obtained from Figure 1 to estimate the amount of photocurrent to expect. Most
users will wish to convert this photocurrent to a voltage (V
accomplished by factoring in an external load resistance (R

= P * ℜ(λ) * R

V

OUT

It should be noted that the load resistor will react with the photodetector junction capacitance (CJ) to limit the
bandwidth. For best frequency response, a 50Ω terminator should be used. The bandwidth (f
response (t

) can be approximated using the diode capacitance (CJ) and the load resistance (R

R

below:

= 1 / (2 * π * R

f

BW

tR = 0.35 / f

For maximum bandwidth, we recommend using a 50Ω coax cable with a 50Ω terminating resistor at the opposite
end of the coax. This will also minimize ringing by matching the coax with its characteristic impedance. If bandwidth
is not important, you may increase the amount of voltage for a given input light by increasing R

Circuit Schematic

) for viewing on an oscilloscope or DVM. This is

OUT

). The output voltage is derived as:

LOAD

LOAD

) and the rise-time

BW

) as shown

LOAD

* CJ)

LOAD

BW

.

LOAD

Setup

• Unpack the optical head and install the battery as described in “Battery Replacement.”

• (Optional) Install a Thorlabs TR series ½″ diameter post into one of the #8-32 (M4) tapped holes, located on

the bottom and side of the sensor, and mount into a PH series post holder.

• Attach a 50Ω coax cable to the output of the DET. Select and install a terminating resistor to the remaining

end of the cable and connect to a voltage measurement device. See the “Operation” section to determine
resistor values. Thorlabs sells a 50Ω terminator (T4119) for best frequency performance, a variable
terminator (VT1) for output voltage flexibility, and SMA-to-SMA (CA29xx series) and SMA-to-BNC (CA28xx
series) coaxial cables. Note that the input impedance of your measurement device will act as a terminating
resistor. A load resistor is not necessary when using current measurement devices.

• Install a fiber source to the DET02AFC photodetector FC/PC connector. Thorlabs recommends cleaning the

end of the fiber each time it is connected with the detector.

Figure 2

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Battery Replacement

Thorlabs delivers each DET with an A23 12V battery. This battery is readily available through Thorlabs, as well as
most retail stores. The battery supplied will deliver about 40 hours with a 1mA load, roughly equivalent to a
continuous 1.5mW light source at peak wavelength. The supply current when no light is applied is very small and
should not significantly degrade the battery.

• Locate the battery cap directly below the output SMA.

• Unthread the cap and remove the battery.

• Install the new battery into the battery slot, positive side in, and thread the cap back into the DET. The

battery spring should be located in the battery cap, not in the housing. The battery polarity is located on the
housing. Be careful not to cross-thread the cap into the housing. The design of the DET02AFC will not allow
damage to occur if the battery is installed backward. In this situation, the photodetector will operate;
however, it will be unbiased.

Troubleshooting

If there is no signal response…

• verify all connections are secure.

• verify the proper terminating resistor is installed if using a voltage measurement device.

• verify that the optical signal wavelength is within the specified wavelength range.

• verify that the fiber is correctly connected.

• verify the fiber is not broken.

If the output appears AC coupled with long rise times…

the battery level may be low and in need of changing. Rise time will degrade as the battery voltage levels drop. We
recommend changing the battery when voltage drops below 9V, because at this point the battery level will drop
quickly.

Maintaining the DET02AFC

It is always good practice to clean the fiber ends before installing them into the FC connector. Dirt buildup will
eventually affect lighting into the detector.

There are no serviceable parts in the DET02AFC optical sensor. The housing may be cleaned with a soft damp
cloth. If you suspect a problem with your DET02AFC, please call Thorlabs and an engineer will be happy to assist
you.

Contact

Americas

Thorlabs Inc.
435 Route 206 North
Newton NJ 07860
USA
Ph: [phone]
Fax: [phone]

www.thorlabs.com

Email:

[e-mail]

Europe
Thorlabs, GmbH
Hans-Boeckler-Str. 6
85221 Dachau-Munich
Germany
Ph: [phone]
Fax: [phone]

www.thorlabs.com

Email:

[e-mail]

UK and Ireland

Thorlabs, LTD.
1 Saint Thomas Place, Ely
Cambridgeshire CB7 4EX
United Kingdom
Ph: [phone]
Fax: [phone]

www.thorlabs.com

Email:

[e-mail]

Scandinavia

Thorlabs Sweden AB
Box 141 94
400 20 Göteborg
Sweden
Ph: [phone]
Fax: [phone]

www.thorlabs.com

Email:

[e-mail]

Japan

Thorlabs Japan, Inc.
5-17-1, Ohtsuka
Bunkyo-ku,Tokyo 112-0012
Japan
Ph: [phone]
Fax: [phone]

www.thorlabs.jp

Email:

[e-mail]

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WEEE

As required by the WEEE (Waste Electrical and Electronic Equipment Directive) of the European Commission and
the corresponding national laws, Thorlabs offers all end users in the EC the possibility to return “end-of-life” units
without incurring disposal charges.

This offer is valid for Thorlabs’ electrical and electronic equipment

• sold after Aug. 13, 2005.

• marked correspondingly with the crossed out “wheelie bin” logo (see figure, below).

• sold to a company or institute within the EC.

• currently owned by a company or institute within the EC.

• still complete, not disassembled, and not contaminated.

As the WEEE directive applies to self-contained, operational, electrical, and electronic products, this end-of-life take
back service does not refer to other Thorlabs products, such as:

• pure OEM products (assemblies to be built into a unit by the user, e.g. OEM laser driver cards),

• components,

• mechanics and optics,

• leftover parts of units disassembled by the user (PCBs, housings, etc.).

If you wish to return a Thorlabs unit for waste recovery, please contact Thorlabs or your nearest dealer for further
information.

Waste treatment on your own responsibility

If you do not return an end-of-life unit to Thorlabs, you must hand it to a company specialized in waste recovery. Do
not dispose of the unit in a litter bin or at a public waste disposal site.

Ecological background

It is well known that electronic products pollute the environment by releasing toxic products during decomposition.
The aim of the European RoHS directive is to reduce the content of toxic substances in electronic products in the
future. The intent of the WEEE directive is to enforce the recycling of such products. A controlled recycling of end-of­life products will thereby avoid negative impacts on the environment.

Crossed out “wheelie bin” symbol

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