Feature: T&M


Figure 2: Block diagram of a typical SS-OCT system with integrated digitizer


supports high-frequency fringe signals without distortion and higher k-clock frequencies. The high dynamic range and low


noise are required to preserve weak reflections from deeper tissue layers. We are looking at 12-bit vertical resolution at sampling rates of 5GSPS. To avoid bottlenecks, scan rates


also need to handle data in real time, including peer-to-peer streaming and FPGA pre-processing. Here, real-time streaming to CPU or GPU at gigabytes per second are preferred rates. And for that immediate image


reconstruction or feedback, low-latency processing is crucial.


ADQ3 digitizer series for SS-OCT Teledyne has developed its ADQ3 series digitizers to meet these requirements. An essential part of the solution is the dedicated application- specific firmware, FWOCT, which maps the sampled k-clock to the OCT signal and performs all the other signal processing steps to produce images; see Figure 1. The k-clock and OCT signal are connected to a dual-channel digitizer. The k-clock signal is sampled by the digitizer and then processed to find


speed imaging systems. Also, phase stability is improved due to tightly controlled hardware-level processing.


Scan rates also need to handle data in real time, including peer- to-peer streaming and FPGA pre- processing


the desired OCT sampling points. For the selected points, the corresponding value of the OCT signal input is estimated with high precision, offering many advantages over direct clocking approaches. Integrated firmware moves key


processing steps such as re-sampling (k-linearisation), digital filtering and, potentially, FFT preparation onto the digitizer itself; see Figure 1. There are several advantages to this approach, including a reduced host CPU/GPU load, a simpler system architecture and lower data transfer bandwidth requirements, allowing data to be pre-processed before streaming. Performance is deterministic and in real time, which is essential for high-


40 July/August 2026 www.electronicsworld.co.uk


FWOCT highlights FWOCT is a dedicated application- specific firmware that provides several advantages, including a flexible k-clock support (4-2000MHz) for use with a wide range of lasers. The k-clock interpolation supports MZI interferometers. Programmable modes allow to select sampled k-clock points mapped to the OCT signal; for example, rising edge, rising and falling edge, or interpolated configuration with multiple points per k-clock period. There are timing adjustments between the k-clock and OCT signal paths, and signal noise reduction is via user-configurable FIR filters. In contrast, many other solutions


rely heavily on software-based processing after acquisition, which introduces latency, increases system complexity, and can limit achievable imaging speeds; see Table 2. Teledyne SP provides its ADQ32,


ADQ33 and ADQ35 instruments in either PCIe format or with a USB 3.2 interface, whereas the DQ36 is available in PXIe format.


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