FAQs | APD modules

What is the output voltage amplitude of APD modules?

When shipped from the factory, the output voltage amplitude is set as follows。

Type no. Output voltage amplitude
C12703 Approx. +10 V
C12703-01 Approx. -10 V
C12702 series Approx. -0.4 to -0.3 V
C10508-01 Approx. +3 V
C5658 Approx. +0.7 to +0.8 V

What is the maximum incident light level to APD modules?

The maximum incident light level is calculated for each type by the output voltage amplitude [V] ÷ photoelectric conversion sensitivity [V/W]. Incidentally, the incident light level leading to device destruction is approximately several milliwatts, so take precautions before actually inputting light to the device.

The APD module is not functioning properly. Why is that?

Check the following points:

*Is the power supply wiring correct?
*The termination resistor should have the values shown here.

Type no. Termination resistor
C12703 series 10 kΩ or more
C10508-01 10 kΩ or more
C12702 series 50 Ω
C5658 50 Ω

*Is the incident light level exceeding the maximum allowable level?
*Is the gain set too high? (C12702/C12703 series)

If the gain is too high, then the APD dark current will increase, causing the APD's excess noise to increase and lowering the S/N.

Noise signal is superimposed on the output. How can it be avoided?

When ambient fluctuating light enters an APD, it may cause noise to appear in the output. Noise from commercial power sources may become superimposed on the output signal, especially when under fluorescent lamp lighting. We recommend using the APD module in a dark location as much as possible. Also use a series power supply with low ripple noise rather than a switching power supply. If this problem is not solved, then contact our sales office for advise on the ambient condition.

Can optical fibers be connected to an APD module?

For optical fiber connection to the C12702/C12703 series and C10508-01, the FC and SMA type optical fiber adapters (sold separately) are provided. Recommended optical fibers are GI type multimode optical fibers with a quartz core of 50 μm diameter and a clad of 125 μm diameter. No optical fiber can be connected to the C5658. Custom modifications are required for connecting an optical fiber to the C5658.

Are there recommended power supplies?

We will let you know the commercially available, stabilized power supplies that are suited for the APD module to be used.
Contact our sales office for details.

Are there recommended light sources?

Use light sources such as an LD or LED that match the spectral response of the APD module. To check the light level that will be input to the APD, we recommend measuring the optical power in advance with a power monitor.

Can an A/D converter be directly connected to the APD module?

Connecting an A/D converter directly to the APD module is not recommended. The A/D converter's input impedance may adversely affect the APD module, making it impossible to obtain satisfactory characteristics.

Can the APD module's electrical characteristics be changed?

We can make a custom modification to the APD mounted in the module and the electrical characteristics such as bandwidth and sensitivity (a service fee is required).

Can the APD module's gain be changed?

On the C12702 series and C12703 series, the APD gain can be changed by using the APD gain adjustment trimmer. Note, however, that this trimmer does not have any scale and stopper mechanism, and can be turned many times. So, before turning the trimmer, it is recommended to allow the reference light to enter the APD and check the output so that the trimmer can be returned to the initial state when needed. The adjustable gain range of this trimmer is from one to over several hundred times where a breakdown occurs.

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