Transfer Rate Limits for Each Time Tagger Model

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Time Tagger 20 utilizes a USB 2 interface, which limits the maximum transfer rate to about 9 MTags/s. Time Tagger Ultra and Time Tagger X instead utilize a USB 3 interface, allowing a maximum transfer rate of approximately 90 MTags/s; Time Tagger X additionally provides SFP+ and QSFP+ interfaces for even higher data rates, as described in later sections. Reaching high data rates depends on many variables, e.g. CPU performance, workload from other running processes, and power and performance settings; the figures above can only be achieved using a high-performance CPU with minimal workload from other applications running on the same computer.

Measuring Your Own Transfer Rate

The maximum transfer rate achievable with your system can be measured using the transfer_rate.py and/or maximum_transfer_rate.m scripts in Python and MATLAB, respectively. These scripts can be found in the example section of the installation folder.

In a series of tests conducted using the top-performance CPU AMD Ryzen 9 5950X 16-Core 3.40 GHz with only essential processes running in the background, we were able to measure a maximum transfer rate of approximately 93 MTags/s for Time Tagger Ultra and Time Tagger X, and 9.2 MTags/s for Time Tagger 20. If your laptop has an “Ultra-Low Power” CPU (denoted by a U at the end of the CPU model, such as the AMD Ryzen 7 PRO 4750U or Intel i7-1365U), it is crucial to connect your laptop to a power source when acquiring data. Otherwise, you may experience a reduction of up to 30% in the transfer rate.

These results suggest that CPU performance is more significant in limiting the maximum rate than USB 3, provided everything is set up correctly. See our Recommended USB Accessories article for how to set up your Time Tagger connection to the PC without degrading the transfer rate, and our Optimal PC Requirements for Time Tagger article to learn more about choosing a PC to maximize it.

Streaming Directly to a PC over 10 GbE

Time Tagger X also provides a 10 Gbit/s Ethernet (10 GbE) link over its SFP+ port, which can stream time tags directly to an acquisition PC as an alternative to USB. This supplements rather than replaces the USB connection: USB remains required for device configuration and control, and only one of the two interfaces carries the time-tag stream at any given time. It is intended for applications with sustained tag rates or latency requirements beyond what USB 3 can reliably provide. 10 GbE data transfer is available to all users at up to 100 MTags/s; with the High Rate hardware license, the full transfer rate of up to 300 MTags/s is enabled. See our 10 Gbit/s Ethernet Link in-depth guide for the full setup instructions.

Streaming Data to an External FPGA over SFP+/QSFP+

For applications that connect an FPGA of your own design directly to the Time Tagger X, rather than streaming to a PC, the SFP+ and QSFP+ ports can also be used as an Ethernet-based FPGA link, enabling data transfer of up to 300 MTags/s (SFP+) or 1200 MTags/s (QSFP+) in the form of raw data blocks encapsulated into Ethernet frames. This is a separate feature from the 10 GbE link described above and is mainly intended for custom hardware integration. See our FPGA Link in-depth guide for the full setup instructions.

Streaming via TimeTaggerNetwork over Ethernet

The maximum transfer rate achievable with TimeTaggerNetwork is limited to the transmission speed of your local network. A widely adopted transmission technology in modern network infrastructures is Gigabit Ethernet (GbE), which provides a data rate of 1 Gbps. This limits the transfer rate from Time Tagger Ultra or Time Tagger X to a PC over the network to up to 29 MTags/s.

Channel Count Does Not Affect These Rates

The number of registered channels does not affect any of the maximum rates above, whether over USB, the 10 GbE link, or TimeTaggerNetwork: they hold the same whether one or many channels are aligned and streaming simultaneously.