LDRVDUAL is a dual-channel current drive and temperature control module for semiconductor laser diodes, SOAs and PPLNs. Its main functions include: controlling the internal temperature of the laser, generating a constant current signal to drive the laser, and converting the external input voltage signal into a current drive. The module has 4*2 maximum current drive ranges, suitable for lasers of different power sizes (selected by circuit board patch cords). Considering the wiring problem, 3 fiber optic interfaces are designed, and a power cord port is reserved for user operation.

The built-in reference source has an extremely low noise level and can achieve 16-bit control accuracy. Both current and temperature parameters can be stored on the module, and the laser can be operated with these parameters via a simple external trigger signal. This makes the module a plug-and-play, high-stability laser light source.

Install

Please be sure to refer to the laser manual, the wiring sequence of the corresponding connector, and the wiring on the circuit board to confirm that the laser is compatible with the current wiring sequence. Powering on with an incorrect wiring sequence may cause damage to the laser!

The negative input of the power supply of the module, the bottom plate and the negative pole of the NTC are all grounded. And the positive and negative poles of the drive output are not grounded. When any functional pin of the laser to be installed is grounded (connected to its shell), special attention should be paid.

When there is a grounding situation of the laser function pin (such as the positive pole of the laser is grounded), a piece of sticky thermal conductive silicone needs to be placed between the laser and the bottom shell, and do not use metal screws to fix the laser to insulate the laser shell from the bottom shell. If you are not sure, please consult the engineer of the seller. Improper grounding will cause abnormal function of the module or even burn the laser!

！The two patch cords in the same channel must be completely consistent, otherwise the instrument will not work properly! All operations should be performed with the power off.

！If the laser has a built-in voltage divider resistor, try not to use it, as it will cause the external drive voltage to be insufficient and the laser will be in an undervoltage state.

Panel

From left to right:

Power interface: 3.81mm connector 1, VSOA DC 5~12V, 3A. Use low ripple regulated power supply to reduce overall system noise.

3.81mm connector 2, VIN DC 5, 5A. Use low ripple regulated power supply to reduce overall system noise.

Communication interface: serial communication, baud rate 115200bps, 8 data bits, 1 stop bit, no parity bit; 3.3V TTL level. You can use a patch cord to short the GND and RX pins to make the system start driving the laser according to the set internal current. Please be sure to use this function after all parameters are fully set.

P+, P- are auxiliary connectors, and the internal connector can be used to directly connect the laser pins.

COM light: communication indicator light, red light is displayed when GND and RX are shorted.

SYS light: system status light. When the laser is not installed or the laser temperature is not stable to the set value, the yellow light is displayed. When the laser temperature is stable, the green light is displayed. When the internal drive current is turned on, the red light is displayed.

DIRECT INPUT: SMB connector, input voltage 0~2.5V, input frequency 0~20MHz

AC INPUT: SMB connector, input voltage -5~5V, input frequency 20Khz~20MHz

Pay special attention!

！When the laser has a functional pin connected to the shell (such as NEL laser, the positive pole is often connected to the shell), the laser shell must be insulated from the base: a layer of thermal conductive silicone pad is placed under the laser, and do not use metal screws to fix it.

！The laser current setting needs to be realized through short-circuit caps (patch cord caps) at P3 and P10. Mismatch between the two will cause the system's self-identification and actual current to mismatch, which may cause the laser to burn out!

！It is recommended to connect an LED lamp bead or a cheap red laser first to test whether the current setup is working properly.

！Laser temperature oscillation indicates that the temperature control PID parameter settings are incorrect. The temperature control parameter adjustment command is tecp kp kI kd. It will take effect immediately after sending. Observe the temperature response accuracy and speed until a satisfactory effect is achieved. After the adjustment is completed, use the save command to save.

！The module has no switch. After connecting the power supply, the temperature control function starts working immediately, but the laser current source does not start. The green light indicates that the temperature has stabilized. Use a patch cord cap to short RX and GND to start the current source. Please use this function after the parameters are fully set!

External signal input (Direct)

The signal input terminal INPUT on the rear panel of the instrument is used to receive external input. When the internal bias signal is not turned on, the equivalent circuit is shown in the figure below:

The driving current of the laser is:

I_Laser = (V1/1.25V) x I_max

I_max=149mA, 378mA etc

When the internal signal is turned on, the equivalent circuit is as follows:

Tunable curve

If only the internal signal is used, all connections on the INPUT interface should be disconnected. If you want to use both internal and external signals at the same time, please calculate the final effect yourself according to the above equivalent circuit.

External signal input (AC)

The instrument also has an AC input channel with a -20db gain, which is AC coupled with the internal reference source. It is convenient for users to input modulated signals with larger amplitudes to improve the signal-to-noise ratio. The instrument reduces it by 10 times and then superimposes it on the original low-noise internal reference source to achieve low-noise modulated output, as shown in the following formula:

I_laser = (-V_ac/25V) x I_max+I_internal

PC Control Interface

Replace the instrument cover, connect the controller to the power supply, and connect it to the computer with a USB cable. WIN7 and above systems will prompt to automatically connect to the Internet to install the USB driver. When using other systems or unable to connect to the Internet, please download the corresponding driver at  http://www.ftdichip.com/Drivers/VCP.htm .  After the driver is installed, a virtual serial device will appear in the "Device Manager".

Open the computer-side dedicated software, as shown below:

Find the corresponding virtual serial port in Communication Port. If not found, click the Refresh button. Click the Connect button. After normal connection, the console will light up and read the current setting value of the controller. Enter the required operating temperature in LD Temp Setpoint and click Set Temperature to set it. The Bias slider sets the constant operating current value, and the Limit slider sets the maximum limiting current. Driver and Driver2 control the current of the two channels respectively. After setting the parameters, click Set Parameters below to send the parameters to the instrument. Click Save All Settings to save all parameters in the instrument.

Click Run:DC to start the laser with the set current value. The Limit slider is used to protect the laser. It can also limit the current under external input conditions. Please set it to the maximum operating current in the laser parameter table.

！Before starting the laser, please carefully check whether each parameter is within the allowable operating range of the laser!

Communication instructions

The dedicated conversion cable connects the circuit board to the computer USB or serial port. The USB converter uses the FT232R chip to simulate the serial port. WIN7 and above systems will automatically connect to the network and install the driver. For other systems or when not connected to the network, please download the corresponding driver at  http://www.ftdichip.com/Drivers/VCP.htm  . After the driver is installed, a new serial device will appear in the "Device Manager", and the communication rate defaults to 115200bps. Change the parameters by receiving ASCII format serial commands, and the command ends with a carriage return.

The following uses PuTTY as an example to illustrate the communication method. After opening PuTTY, select Serial for connection, enter the same port number as in the device manager, enter 115200 in Speed, and click open to open the black interactive port. Enter the relevant instructions through the keyboard (the Backspace key is invalid). After entering the command correctly, the system will prompt the setting result, and an error will return an error message.

The computer is the main control end (host computer), and sends a string command. A line of command starts with a colon ":" as the start character of the first channel, and ends with a carriage return (\r\n). The lower computer returns information after execution. All the following functions can be accessed through the supporting software. It is recommended to complete the settings with the supporting LDPD software and get the correct waveform, then click Save to save the parameters to the lower computer, and then transfer it to other clients for control.

The operation modes are as follows:

Parameter Setting: