Command/Response Structure - THORLABS DFB13TK User Manual

Low-Noise DFB Laser System
and supports modulation frequencies from 2 kHz to 20 MHz. The DC current modulation port is DC-coupled and
supports frequencies from 0 Hz to 5 MHz. For both current modulation ports, the input voltage range is from -5 V
to +5 V. The AC modulation port modulates the current at a rate of 20 mA/V around the current set-point. The DC
modulation port modulates the current at a rate of 2 mA/V around the current set-point. A third modulation port
is included for modulating the temperature of the laser around its set-point. The chip temperature can be
controlled through the analog voltage input applied to this port (-5 V to +5 V). This port has a bandwidth of 1 Hz
and is designed for slow modulation of the laser temperature for applications that require locking the laser
frequency. The temperature modulation port is disabled by default and can be enabled to control the chip
temperature through a command sent via the USB or RS-485 connection on the back panel of the laser. The rate
of temperature change versus voltage can also be set through a command. Please see Section 4.4 for details on
the commands for setting up the temperature modulation input. All modulation ports have an input impedance
of approximately 1 kOhm.
Software Communications
Each device is equipped with an USB mini-B style connector for USB communication with a host device. The device
will enumerate as a Virtual COM port on the host device. For Windows PCs running Windows 10 or later, no special
driver is required. For Windows PCs prior to Windows 10, the driver included as part of the firmware update utility
is required.
All communication queries must be terminated by a single carriage return character (\r) or a combined carriage
return and newline (\r\n). Communications originating from the device will be terminated by one or more
combined carriage return, newline pairs (\r\n). A connected host should not attempt to send additional queries
until a response has been received from the device. Most queries will result in a response within 10ms. Queries
requesting the saving of configuration parameters will result in longer response times.
The commands sent from the USB interface enable the following functions:
• Turning the laser on or off
Reading status of the laser, and values of the laser temperature set-points
•
• Adjusting the temperature set-points for the chip
• Adjusting the drive current of the laser
Setting the external temperature modulation port function. The default for this port is to be disabled, but
•
it can be changed to adjust the chip temperature based on the analog voltage applied to this port.
In addition to the USB port, a RS-485 port has also been included on the back panel of the system. This port, a 9-
pin D-Sub, can be used with the same command set outlined in this chapter through the RS-485 communication
protocol. Please refer to the last sub-section in this chapter to see the pin-out of the D-Sub connector.
4.3.1

Command/Response Structure

All commands are text based with the basic format as follows:
command [param1 [param2..[paramN]]]
Proper syntax will be specified for each command in the following subsections. Each command will be followed
by a corresponding response with the following format:
Response_code:Response_Text[command_response]
Note that all commands and parameters are lower-case letters.
Page 12
Chapter 4: Operation
TTN339662-D02