Laser Diode Bias-T PCB

Superimpose an RF Modulation Input onto
a Laser Diode Drive DC Current
Modulation Frequencies from 10 kHz - 1 GHz

T1G

Shown with
Included OSMT
Coaxial Cable

Application Idea

LD1100 Laser
Diode Driver

T1G Bias-T

Laser Diode
Terminals

To Function
Generator

Laser Diode
DC Current

RF Modulation Input

Modulated
Laser Diode
Output

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Overview
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Specifications
Frequency Range	10 kHz to 1 GHz
Input Impedance	50 Ω
Max DC Current	110 mA
Max RF Current (RMS)	50 mA

The T1G laser diode bias tee is designed to superimpose a modulation current onto the laser diode DC-supply current, thereby modulating the output power of the laser. This is useful in applications where information is being transmitted over a fiber.

A laser diode driver sets the DC current, and then an alternating voltage is applied to the RF input, which produces a modulated current, allowing the user to achieve the desired modulation amplitude. This bias-T is capable of providing modulation frequencies in the range of 10 kHz to 1 GHz, although the actual frequency range is limited by the impedance network surrounding the laser diode. Using the provided OSMT wire, a function generator can be connected to the OSMT coaxial connector, which has a characteristic impedance of 50 Ω. A DC blocking capacitor and a reverse bias protection diode are included to protect the laser diode.

In addition to the T1G bias tee, Thorlabs manufactures a range of products well suited for building laser controllers, including laser diode drivers, temperature controllers, and evaluation kits. Thorlabs also offers packaged controllers that are ready for integration into rack-mounted systems without additional modification.

Posted Comments:

julien.schiellein (posted 2018-07-25 08:45:57.557)

Hi, I bought several of these T1G boards. They are very convenient for testing. However, one major drawback is the fact that the ground of the RF signal is also directly connected to what is identify as DC negative... In the case of Anode Grounded Laser, the case of the laser is connected to the Anode of the laser, which is connected to the DC Positive of the Board... So if you attach your laser to some case which is also holding your RF connector, you will have a short circuit between DC positive and DC negative. This is not destructive, but it prevent the laser to work... Do you have any plan to fixe this issue? Best regards

YLohia (posted 2018-07-30 10:39:37.0)

Hello, thank you for contacting Thorlabs. When using laser diodes that are Anode Grounded, you need to either physically isolate the TO-can from the power supply ground (usually through Earth ground) or use a power supply that is isolated from earth ground (for e.g., a linear supply). Another option is wiring the laser backwards. Doing so will make the orientation of the protection diode incorrect, which will then need to be removed from the circuit (leaving the laser diode exposed to reverse currents).

lslatte2 (posted 2017-08-18 11:42:14.377)

Hi, I was wondering if I could have the board dimensions? I need it to fit in a small space. In addition, is there any chance it could be made with a higher dc current? Thanks in advance.

tfrisch (posted 2017-09-13 04:54:23.0)

Hello, thank you for contacting Thorlabs. The overall board dimensions are 0.870” x 0.600”, and we are working on a drawing to post as well.

hz13g13 (posted 2017-02-06 06:23:27.02)

Hi, I already have a thorlabs LDC205C benchtop driver, I wonder if I can connect the output from the laser driver to the T1G bias-T ? Could you please provide me with instructions? Can you source an OSMT-BNC adapter or sell me one, please? Thanks

tfrisch (posted 2017-02-17 01:39:27.0)

Hello, thank you for contacting Thorlabs. Both the DC and AC inputs of the bias T require a voltage as described in chapter 3 of the manual. I will reach out to you with more details regarding this and the adapter.

mitch (posted 2016-09-04 08:13:25.437)

Hi, I have bought several of these boards from you but the OSMT connector is the rarest connector on earth, it seems! I can't find an adapter anywhere. What coax cable are you using so that I can buy my own SMA plug and use it on one end, instead? Can you source an OSMT-SMA (or anything else, really) adapter or sell me one, please? Thanks

tfrisch (posted 2016-09-07 01:40:33.0)

Hello, thank you for contacting Thorlabs. I will reach out to you directly about the cable you need.

mitch (posted 2016-08-09 06:42:47.703)

Hi, would it be possible to tell me what the value of the capacitor is? I see the inductor looks like 0.22uH. I would like to sun some simulations to see how well this bias-t will work for me. Thanks

jlow (posted 2016-08-15 09:21:48.0)

Response from Jeremy at Thorlabs: We will contact you directly about this information.

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Laser Diode Bias-T PCB