The wire, cable and cable assembly community has embarked on a revolutionary plan to help OEM equipment designers change the way they deal with cables. With the advent of thinking cables, system designers can literally think outside the box when it comes to communication ports.

Background:

Like most communication technologies, there are many forerunners claiming rights and precedence for thinking cables. One inventive forerunner that rushed to aid a struggling progenitor in need was the designer of bar code scanning cable assemblies in the early 1990s. The early hand-held bar code scanners had to communicate with electronic cash registers from IBM, NCR, ICL and others, each with different communications requirements. One solution (see Photo 1) was to embed printed circuit boards with active circuits into the cable assembly itself. Power for the active circuit came from the cash register connector port.

At left, a bar code scanner cable is shown with the integrated active circuit cover removed.

While this solution appears to be simple and straightforward, implementation required designers to overcome significant engineering challenges.

Challenge #1: The design required the circuit pod to be strain relieved on both sides. The cable assembly strain relief must withstand severe flex and movement abuse, being in a consumer-oriented, high volume, point-of- sale (POS) application.

Challenge #2: The active circuit board inside the pod needed to be potted, with components secured to withstand severe abuse.

Challenge #3: Connections on the board needed enhanced soldering or welding techniques to ensure long-term reliability

By 1994, shipments of handheld barcode scanners incorporating these thinking cables reached millions of units per year. C&M Corporation, one of the manufacturers of these active cable assemblies, had hundreds of thinking assembly designs in production throughout the 1990s. Some thinking cable assembly designs had moved the active circuit board into the connector end, eliminating the mid-cable pod, as shown in this USB thinking cable assembly in photo #2.

In this application, the cable strain relief must be extended to encompass the active circuit board. The strain relief design is more complex than normal because it must be able to protect the board while still providing a flexible cable end in a dynamic, high use environment.

In the communication cable field, designers in the 1980s from Digital Equipment Corporation and IBM and probably others, had been incorporating active devices such as capacitors, inductors, resistors and other more advanced circuit devices affecting the signal waveform into their cable assemblies. Other designers used the electrical properties of the cable itself to modify the signal waveform. While these cables could be called active cables because they did modify the signals, most of these devices did not require external sources of power to perform their magic – just the signal traveling from the connector port. Today, it is commonplace to have compensating circuits embedded in Fibre Channel and Infiniband copper cable assemblies. I refer to these types of cables as active cables, just one form of thinking cables.

When datacom fiber optics became commonplace in the early 1990s, OEMs produced either copper or fiber-based equipment. To give customers the option of selecting from different media (copper vs. fiber) or optical distance options, first the media converter, then the pluggable port was created with names such as GBIC (Gigabit Interface Converter), SFP (Small Form Factor Pluggable) and others.

Photo 3:   While media converters as discrete devices could be used to convert from one type of connector, media or transceiver to another, these converters continued to shrink in size while adding significant functionality. This converter required two different signal cables plus a power cord.

Standards committees, notably the Power over Ethernet group, recognized that providing power at the connector port could (a) spur development of multifunction devices, such as security cameras that rotate or (b) trickle-charged laptops or sensors through a copper RJ45 Ethernet cable thus requiring only one cable for power and data purposes. Seeing the benefits of such an option, the Infiniband standards committee changed their specifications to allow power at the connector for active high-speed interconnect applications. Some designs now offer powered emphasis circuits that greatly increase operating distances. Wherever we look, in the industrial automation field, in high-speed communications, in general communications, the idea that power at the connector port can spur innovation has taken hold. All of these changes individually are interesting, but taken collectively, they are pointing to a change of monumental proportions for the cable assembly industry.

Benefits of the thinking cable:

Like most people, I prefer wireless devices. Many devices however cannot be wireless due to reasons of security, distance, EMI / RFI issues or power consumption. Our current technical ability to supply power to equipment without plugging a cable into an electrical outlet is very limited (though wireless transmission of significant power has been demonstrated and is certainly possible). It appears that cables will be around to power our electrical devices for the near future. Some OEM designers, recognizing this fact, have opted to change the rules completely for cables.

Until recently, most OEMs looked at cables as a component to be sourced to the lowest bidder, built in places that only the National Geographic Society had ever visited. Today, designers are seeing that the cable can do more for them than just passive signal carrying. In fact, it can spur cost reductions that far exceed the cost of the cable itself. The biggest opportunity is cost reduction across their entire product platform if thinking cables are used properly. Here are just a few of the opportunities:

A) One interface for both copper & fiber: OEMs no longer have to carry both a copper and fiber solution for their LAN, SAN, WAN equipment. In the past, the OEM required copper cable assemblies for the copper port and fiber optic assemblies for the fiber ports. Each fiber port had either a permanently mounted transceiver or a plug-in style transceiver requiring a cage / carrier system to allow the plug-in capability. By changing to a single powered interface, the OEM benefits from having just one electronics unit to inventory. The customer can choose from a range of conventional and thinking hybrid cables that will support the speed and distance needed for the application.

B) Merging the best of a copper and fiber interface: In the hybrid copper/fiber applications, the actual ceramic or polymer fiber ferrules can be completely eliminated, saving significant cost and preventing the bane of fiber communications – dust, oils and scratches. Copper connectors, with its two best features, robustness and self-cleaning gold contacts married to the speed and distance benefits of optics, will see new life in hybrid assemblies. With power available at both ends, copper connectors with embedded electrical to optical converters can be used with fiber optic cable for extended reach applications while conventional copper cables are used for short reach versions.

C) Cable Margins, not Transceiver Margins: With proper vendor management, the OEM can have quick-turn assembly vendors build-to-order either conventional copper or copper-fiber hybrid assemblies. There is no need for the OEM to inventory stand-alone transceivers or fiber optic cable patch cables. By pushing assembly of embedded optical transceivers to the cable suppliers in the ferociously competitive cable assembly business, this will drive down costs due to vertically integrating the low-end assembly business, with a savings on transceiver packaging and fiber connectors.

D) Self-Awareness: By embedding chips capable of self-identification and test into the cable assemblies, solutions providers can have real-time wiring analysis between active devices without expensive 3rd party intelligent patch panel systems. Other awareness activities and services can be built into the assemblies, off-loading the main electronics the assemblies are plugged into. Infrastructure tracking costs can be greatly reduced by self-aware cables with broadcast abilities. Even if there is a problem and the thinking cable is no longer capable of broadcasting, the lack of a message from the cable child can be itself a yell for help if this silence is recognized by an attentive electronics parent.

E) Environmental: With RoHS and other green initiatives driving designers to take a second look at their methods, thinking cable assemblies would have enough value to justify Return, Repair or Recycling (The 3Rs). Manufacturers of these assemblies can design the devices to be upgradeable or recyclable and offer these services for OEMs.

F) Data Centers & Cooling: One forgotten fact about many data centers is that as the blade servers and ever shrinking switches and routers implement data speeds of 10 Gbps or faster, the heat density grows significantly in those concentrated racks of equipment. Cooling specialists Emerson / Liebert and APC have advised customers to study those hot spots in the data centers. Removing relatively low power VCSEL transceivers from the electronics and moving into the cables gives the equipment designers more room to work with on the valuable PCB real estate. It also pushes the minimal heat load from the hybrid assemblies to the cable assemblies. These cable assemblies sit the ambient cool air environment of the data center, not the sweltering internal life inside the electronics cabinet next to some overheated processor chip. If the cables can’t be eliminated due to speed constraints, designers might as well use the cables for other purposes, such as heat sinks outside the active box, to cut costs or to improve mating reliability.

Summary:

It won’t be long now before thinking cables become mainstream in our day-to-day lives. What will be interesting is the impact on the OEMs that adopt the technology early and take advantage of the long term cost benefits. OEMs seeking too late to develop the assembly suppliers capable of working with the hybrid copper-fiber designs and embedded active circuits might find themselves engaged in a cost war they might not survive.

Author: Joseph Iamartino,
BS Electrical Engineering, University of Rhode Island
MS Technology, Worcester Polytechnic Institute
Professor of Business at Baypath College
Vice President Marketing & New Business Development
C&M Corporation