Letter to the Editor

Dear Sir, I read with interest the article "Cameras and camera interfaces span the bandwidth spectrum" by Andrew Wilson, Contributing Editor in the February 2017 issue ofVision Systems Design. In regards to Figure 1 which charts bandwidth against maximum theoretical cable length, I would like to point out that comparing bit rates could have been described more exactly.

Since 8b/10b encoding used by CoaXPress (CXP) consumes 25% of the bandwidth, optical 40GigE is about the effective bandwidth of CXP-6 (octal) that provides 4.8GBytes/s of throughput.

CLHS X quad protocol as demonstrated recently by camera manufacturer PCO (Kelheim, Germany;www.pco.de) and frame grabber vendor Kaya Instruments (Haifa, Israel; www.kayainstruments.com) achieves this bandwidth over fiber and should have been shown beside the 40GigE solution. The CLHS standard also supports an octal configuration (9.6 GBytes/s) although not used by a commercial product to my knowledge.

With the introduction of thumbscrew active optical cables (AOCs) for the CX4 connector, Teledyne DALSA (Waterloo, ON, Canada;www.teledynedalsa.com) achieves rates of 35Gbps in our company's current color camera and frame grabber (3.3 GBytes/s). The roadmap for the CX4 connector is to move to 10.3 Gbps, 12.5 Gbps, and 14 Gbps per lane x7 lanes to achieve 8.4, 10.2, and 11.4 GBytes/s of throughput in a single camera to computer cable solution.

Yours sincerely,

Michael Miethig
Camera Link HS Chair
R&D Camera Development Manager
Teledyne DALSA
Waterloo, ON, Canada
www.teledyne.com