How the digital-interface standards for cables and connectors are changing

CoaXPress (CXP) is a popular, digital-interface standard developed for high-speed transmission of data, videos, and still images. This interface was introduced in 2008 and has been used in industrial automation for years, with advanced machine vision and robotics applications following suit. It has been driven by reliability and simplicity, which includes its cables and connectors.

CoaXPress combines conventional coaxial cables with high-speed, serial data technology. It provides a method for connecting high-resolution cameras to frame grabbers (which are high-speed capture cards) by using conventional coaxial cables.

For many years, COAX connectors and cables were used by this standard to support connectivity and older topologies. For example, Micro BNC’s circular connectors and Micro-Coax cables were typically used for older 6Gbps per-lane or link products. However, many of today’s I/O Faceplate connectors and cables must be robotic-friendly. (Micro-Coax is not ideal in these applications.)

More recently, CoaXPress has represented a booming market segment for advanced cables and connectors, including the quad small-form-factor pluggable (QSFP) and other pluggable connector types. QSFP is a compact, hot-pluggable transceiver used for data-communications applications.

The data-center industry is also proving an ideal and developing market where pluggable interconnect products, such as Twinax cables and QSFP connectors, are gaining popularity. Twinax is a type of cable similar to coaxial cable, but with two inner conductors instead of one.

There are several interconnect options available, including:

The current 12.5Gbps per-lane speed rate typically supports four-lane links, trunked four links, or link aggregation using QSFP+ pluggable interconnect types.

The latest CoaXPress 2.0 standard is expected to increase the performance of machine-vision systems at twice the speed and data rate. Twinax cables and optical connectivity are commonly used with these applications. CoaXPress-over-Fiber has also been designed as an add-on to the CoaXPress 2.0 specification, which provides a way to run the protocol over an Ethernet connection.

Japan Industrial Imaging Association (JIIA), which is dedicated to advancing technological innovation for industrial imaging, offers an informative document worth reading to learn more (check out JIIA’s “Optical Interface Guidelines for Coax Press”).

JIIA is currently developing 25 and 50G per-lane products, with expected 1, 2, 4, and 8X-link CoaXPress specifications using QSFP28 and QSFP56 connectors. However, they might switch to using some versions of the SFP56 and SFP112G links.

Camera Link is another high-end standard designed for camera interface applications, first launched more than two decades ago in 2000. It was designed for standardizing scientific and industrial video products, including cameras and frame grabbers, and already uses QSFP56 and QSFP112 connectors in AOCs, AOMs, and DACs. CameraLink has more recently used QSFP28 interconnect types, as well.

This group has remained relatively small and technologically focused on advancing. For instance, Camera Link High Speed (Camera Link HS) is an advanced interface standard for industrial cameras and systems that evolved from Camera Link.

Over time, several new types of higher-end cameras and sensor arrays have developed, driving the need for even greater network bandwidths and lengths. The goal with any digital-interface protocol, of course, is to continually transmit larger amounts of image data at faster speeds. To this end, there have been discussions amongst the industry about the potential benefits of merging CoaXPress and Camera Link HS standards.

Many of the proponents for this proposed merge are from the CoaXPress consortium leadership. It has promoted its CoaXPress-over-Fiber IP products. However, a merged QSFP connectivity family would likely need new or revised Forward Error Correction (FEC) and Common Management Interface Specification (CMIS) link requirements, as well as interoperability testing.

Currently, CoaXPress and Camera Link standards are different and have unique protocols and full-stack interfaces, both with better performances when compared to basic Ethernet or GigEVision. However, CoaXPress and Camera Link undoubtedly intend to capitalize on using the newly developing IEEE 802.3 standards within their own protocols, particularly as it relates to connectors, cables, and modules.

The question remains: is merging the way to increase and strengthen global market-share?

USB3 and USB4 are popular 10, 20, and 40G interfaces for use with frame-grabber I/O applications. There is already a large installed base of USB2 video frame-grabber, end-users who are ready to move up to USB4 devices. What sets USB4 apart from its predecessors is the ability to deliver up to 40 gigabits-per-second of transfer speed.

Overall, these interfaces offer various power and protocol options such as USB-like DisplayPort, HDMI, TB-4, MHL, and others. The USB4 will rely on the reversible USB Type C connector and circuit pinout options using AOC or Twinax cable options, depending on the system.

The USB-C cable, connector, and controller chip are much less costly than CoaXPress or CameraLink parts. The Type C connector also has waterproof options and is extremely lightweight. The Type C Twinax cabling is also small and lightweight compared to other pluggable or Micro-Coax connectors.

What’s more: a small Spectra7 active electrical chip is mounted onto an extremely small circuit board to improve the reach of Twinax cables. This type of cabling is similar to that used by AR VR video systems, which includes the rapidly growing Prosumer segment and gamer headsets.

The USB4s are already shipping, so it’s likely the USB5-based product is already under development.

Final thoughtsVisit CoaXpress for the latest news on the potential merging of CoaXPress and CameraLink IO standards. It’s worth noting that there is also a small market share for other video frame-grabber interfaces, such as Hotaru’s OPT-C: Link and Mikrotron Eosens Fiber products.

Although there is a decreasing demand for RJ45 and circular coax connectors, orders for QSFP and USB-Cs are ramping up as these devices become the primary connectors. Most active-copper DAC cables with QSFP plugs are also now embedded with a chip (such as the Spectra7), which enhances the performance of QSFP links.

Suppliers of QSFP, SFP, SFP-DD, DSFP, QSFP-DD, OSFP, OSFP-XD data-center server, storage, and switch copper and optical-ink products can also expect demands to surge to support the quickly growing machine-vision market segment.

Ultimately, cost and supply-chain control will affect how this market excels and changes over time.