Fiber Optics in Automotive Applications

Fiber optic cabling has been used extensively in telecommunication and networking applications. In the automotive world, however, it’s still in its infancy, as is networking within the vehicle. To help explore the potential of these automotive applications, we enlisted the expertise of Delphi Automotive’s fiber optic experts, Reinhard Felgenhauer, innovations and advanced engineering projects supervisor, Delphi Electrical/Electronic Architecture (Delphi-E/EA), and John Yurtin, staff component specialist for data connectivity, as well as Delphi-E/EA Lead Architect, Larry Matola.

What are the main applications for fiber optic connectors and cable assemblies in automotive?

The main automotive application for fiber optic cabling is in the infotainment systems. “The MOST consortium has defined a set of fiber optic connectors and headers for multimedia applications,” says Felgenhauer. The MOST system (Media Oriented Systems Transport) utilizes POF (plastic/polymer optical cable) for the backbone to network the entertainment system—audio and video—navigation, and communication systems. Matola points out that the 1394 Trade Association also provides for fiber optic cabling in automotive applications.

The main standards organizations include the MOST Consortium, ISO Radio Connector, and the 1394 Trade Association.

Right now, fiber optics are not being used in other automotive applications. Although the technology certainly exists for control of electronic steering, for example, much like the fly-by-wire systems in airplanes, it is not likely to make that leap in the near future.

What are the driving factors for fiber optics and why?

According to Felgenhauer, “Fiber optics’ high data transmission capability and immunity to electromagnetic interference (no emission or receiving) is a driving factor. Currently, MOST is transmitting 25 Mb/s. With the identical POF, 150Mb/s is also possible. Emitters and receivers are available for this higher data rate. The MOST consortia have implemented Ethernet data into the MOST data transmission frame. The weight of a fiber optic cable is less than copper, mainly because of the non-metallic wire. For high voltage applications, the complete insulation of these wires creates new application opportunities.”

What are some of the challenges of using fiber optic cabling?

“Delphi has developed a set of internal guidelines for handling and processing fiber optic cable. Since the POF cable in use today for MOST applications differs from the copper wire we normally use, these guidelines address things such as in-process handling, assembly, bend radii, etc. All are internal to the wiring. This ensures the highest quality product delivered to our customers,” said Matola.

High temperature is also an issue. POF is good to about 85°C, and there are harsher temperature environments in automotive applications. “Some development work has been done with several OEMs on 250 micron PCS (polymer clad silica) cable. It is capable of higher temperatures. However, since it is glass-based, it is subject to shock damage, and because of the smaller size, it is more difficult to terminate. With smaller glass cables, the precision found in the interconnect must be greater,” said Matola. In other words, the alignment of the fiber to the emitter/transmitter must be more precise, while at the same time allowing for cost-effective assembly of the cables.

What is the future of fiber optics in automotive applications?

“Fiber optics provides a high-data bit rate transmission. Wires for automotive applications are available. An optical emitter and receiver are necessary, and that is the main challenge because of their cost. The fiber optic data transmission is different than electrical data transmission, but based on the EMI immunity, much less difficult. No electromagnetic interference happens because there is complete insulation of connected components. The lack of familiarity and the low number of applications are the main roadblocks of this technology, but the advantages will provide some new applications,” said Felgenhauer.

“I expect we will see a slow increase in applications over the next 10 years. The total cost of fiber optics limits widespread implementation, and repair is a major issue in the field. The interface is extremely critical to performance and is a major issue in design, application, assembly, and field service,” added Yurtin.

Matola said, “Large scale high speed data connectivity is still in its infancy. The data network historically has been a closed network. With the introduction of USB and more consumer connectivity, the automobile is moving toward the desktop-like networks we are all familiar with. Since there is widespread use of this type of hardware, it is attractive to the OEM because the high volumes result in favorable prices. The automobile still has unique uses that require certain systems to be isolated from consumer access.”

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