CoaXPress-over-Fiber

CoaXPress-over-Fiber is a light but significant extension of the existing CoaXPress specification to support transport over fiber optics.
CoaXPress (CXP) is the de-facto standard for high-bandwidth computer vision applications. CoaXPress’ top speed is CXP-12, a 12.5 Gbps (Gigabit per second) link over a coaxial copper cable. As link aggregation is common with CoaXPress, a bandwidth of 50 Gbps (12.5 x 4) is easily achievable with four CXP-12 links.
CoaXPress-over-Fiber has been initially designed as an add-on to the CoaXPress specification. It provides a way to run the CoaXPress protocol, as it is, unmodified, over a standard Ethernet connection, including fiber optics. As such, CoaXPress-over-Fiber uses standard electronics, connectors and cables designed for Ethernet, but the protocol is CoaXPress, not Ethernet, not GigE Vision.
Euresys and Sensor to Image have started the development and demonstration of CoaXPress-over-Fiber in 2018. The CoaXPress-over-Fiber specification has been approved in 2021 as an add-on to the CoaXPress  standard, which is hosted by the JIIA (Japan Industrial Imaging Association).

What are the cable options for CoaXPress-over-Fiber and what is the maximum cable length?

One of the most important benefits of CoaXPress-over-Fiber is the wide variety of connectivity options already available from multiple suppliers. The initial connectivity options for CoaXPress-over-Fiber at 10/25 Gbps are SFP+/SFP28 and QSFP+/QSFP28 (Quad, or four times SFP) modules.
The advantage of using modules compared to fixed interfaces is that ports can be equipped with any suitable type of transceiver as required by the application. A variety of transmitter and receiver types is available, allowing users to select the appropriate transceiver to provide the required optical cable reach over multi-mode or single-mode fiber. 

Thanks to constant Optical Transceivers evolutions, other options regularly arise, offering longer cable reach with the same types of fibers. 

Breakout optical cables are also available. They feature a 40G QSFP+ transceiver (for the frame grabber) on one side and four 10G SFP+ transceivers (for four cameras) on the other side

These solutions are future proof as higher speed options are available. The SFP28 iteration is designed for speeds of 25 Gbps. The QSFP28 (Quad SFP28) variant allows speeds up to 100 Gbps. Already in 2019, QSFP56 was standardized, doubling the top speeds to 200 Gbps with products selling from major vendors.

What are the jitter and latency of CoaXPress-over-Fiber?

How do they compare to “traditional” CoaXPress?

CoaXPress-over-Fiber is based on the CoaXPress protocol and it exhibits a similar high performance to CoaXPress in terms of jitter and latency. In addition, as CoaXPress-over-Fiber supports higher transmission speeds compared to CoaXPress.

CoaXPress-over-Fiber vs other vision interfaces

How do CoaXPress and CoaXPress-over-Fiber compare with other vision interfaces in general?

CoaXPress is successful because of its unique combination of 

• High bandwidth 
• Low jitter and low latency (including camera triggering)
  
• High stability / reliability

CoaXPress-over-Fiber is CoaXPress, it features the same advantages.

CoaXPress-over-Fiber vs GigE Vision

How do CoaXPress and CoaXPress-over-Fiber compare with GigE Vision?

In terms of image transfer bandwidth 

CoaXPress and CoaXPress-over-Fiber easily support link aggregation and most CoaXPress cameras currently use two or four links. Similarly, CoaXPress frame grabbers offer from one to eight connections per card. The initial configuration of CoaXPress-over-Fiber is 4 x 10 Gbps (QSFP+) for a total of 40 Gbps (the same net bandwidth as four CXP-12 links), or 4x25 Gbps (QSFP28) for a total of 100 Gbps, and there is a clear upgrade path towards 4 x 50 Gbps = 200 Gbps (QSFP56).
On the contrary, link aggregation with GigE Vision is difficult and most GigE Vision cameras use only one link.

In terms of image acquisition stability 

The data packet management of the CoaXPress protocol is simpler. It is done by the frame grabber or interface card, using dedicated hardware, ensuring low latency and stable image acquisition without loading the host CPU.
On the contrary, conventional GigE Vision applications use standard Network Interface Cards (NIC) where data packet management is done by the driver, while significantly loading the host CPU.
Overall, CoaXPress provides more stable, reliable image transfer without loading the host CPU. This will be even more true at higher speeds.

What operating systems are supported?

CoaXPress-over-Fiber is independent from any operating system. As of today, CoaXPress frame grabbers support Windows, Linux, macOS and/or specialized embedded Operating Systems; the same applies to CoaXPress-over-Fiber.

CoaXPress-over-Fiber cameras and GenICam

Do CoaXPress-over-Fiber cameras work with GenICam compatible software?

Yes. CoaXPress-over-Fiber is an add-on to CoaXPress, they both include mandatory support for GenICam.

What are the advantages of using Ethernet connectivity?

By using Ethernet connectivity, CoaXPress-over-Fiber benefits from the low-cost standard components (such as connectors and cables) designed for Ethernet. Ethernet is defined by IEEE 802.3 standard; by leveraging this standard, CoaXPress-over-Fiber will also benefit from the constant evolution of these Ethernet components towards higher bandwidths.

What are the pros and cons of using fiber optics?

Pros 

• First and foremost, cable length is not an issue anymore as fiber connectivity is basically not limited in length. 
• Fiber optics provide more bandwidth, as connectivity at 10, 25 and 50 Gbps per fiber is standard today and widely used in data centers. 
• Fiber optics are immune to electrical noise, which is a significant advantage on the production floor and some medical applications. 
• Fiber optics are lighter and smaller in size than the equivalent copper cabling, making them appropriate for applications where this characteristic is essential, like in mobile robots, aircrafts or vehicles. 

Cons 

• There is no “power over fiber”. As signals in fiber optics are transmitted using light, there is no way to transfer power over fiber optics and devices such as cameras must be powered separately.