23 Aug 2004
Plastic optical fibre (POF) finally seems to have found its killer application - wiring up cars. Paul Polishuk, president of the analyst firm Information Gatekeepers, spoke to Oliver Graydon about POF in cars today and outlined the roadmap for tomorrow.
From Opto & Laser Europe September 2004
OG: How widespread is the use of POF in vehicles? PP: Today, probably more than 15 million optical nodes are found in vehicles on the road. That's come from almost nothing in the space of just two to three years and it's growing at 40% a year. In Europe, around 16 models of car have a POF-based communication system called MOST [Media Orientated Systems Transport] that connects the car's entertainment system.
How did MOST come about? The number of electronic devices in cars, such as audio, DVD players and navigation units, has been growing exponentially so about five years ago Daimler-Benz [now DaimlerChrysler] decided that it needed an easier way to connect them all together. Doing it with copper wires was adding too much weight, cost and complexity. The company decided that the solution was a single databus that should be optical and plastic so that it was immune to electrical interference, and was also lightweight, robust and easy to install. They involved some other European car manufacturers and developed a standard called MOST.
What have been the consequences of the MOST standard? The idea of the standard was to allow all car makers to buy to a common specification and drive prices down so that a POF databus would become cost effective. Since then the price of the parts needed has plummeted. They designed a special type of transceiver package, called CAI [cavity as interface], which allows the fibre to slip into a plastic connector holding a red LED transmitter or PIN detector. Today a 25 Mbit/s CAI transmit-receive pair costs about $4.50 [€3.70], and the price will probably fall to $3.50 in the future. The next generation of transceiver will be 50 Mbit/s and the price probably won't be much higher, and after that want to go to 150 Mbit/s.
How else is POF being used in cars? If you look at a typical modern car, several electronic networks look after mission-critical applications such as steering and brakes, as well as non-critical functions like entertainment, air conditioning and windows.
BMW uses MOST for entertainment and decided to develop another network called Byteflight for mission-critical applications such as airbag control. A plastic-fibre sensor is tied to the POF network to fire the airbags. This is significant because it says that BMW is confident enough to use the technology to serve mission-critical needs.
Another standard called FlexRay is being developed to provide "drive-by-light" tasks such as automated braking, but that's at least a couple of years away. Finally, a group called IDB-1394 in the US is working on a higher-speed system that operates between 150 and 400 Mbits and is based on the IEEE 1394 protocol [FireWire]. This is not employed in cars yet but it is already popular in laptop computers, video cameras and gadgets like Apple's iPod. The idea is that you could have a convenience port in the car. then take devices from home and plug them into the car. There is a trend towards convergence between the automobile and the home.
What future developments and challenges are likely for POF in cars? One challenge is to raise the operating temperature. Daimler wants to go to 125 °C so that it can install POF in the roof of cars but today PMMA [polymethyl methacrylate] can only go to 85 °C. This means that you either have to change to a new material system or use a new type of fibre called plastic-clad silica (PCS) fibre [a fibre with the same dimensions that is made from a silica core surrounded by plastic cladding]. Daimler seems keen to do the latter but there are several issues with using PCS, such as are there enough suppliers and can the price fall, because it is more expensive than PMMA.
Another possible development is moving to a new operating wavelength. All the protocols based on PMMA fibre use red LEDs at 650 nm. However, moving to PCS or another fibre would mean that they could use transmitters at a different wavelength such as 850 nm, where the loss may be lower.
Aside from cars what other areas might benefit from POF? The home market is potentially huge but has yet to take off. The 1394 protocol could be used to interconnect all kinds of electronics in the home by wiring it with POF. Many audio-video devices, such as CD, DVD and mini-disc players, already have optical outputs that use POF, but more could be done. In Japan we've counted up to 20 buildings that are wired with perfluorinated fibres. For example, there are some hospitals that have 100 Mz going to the patients' rooms. The other area is the industrial control business, where a lot of POF is already used for the control buses. They now want to move to Ethernet over POF.
POF-based databuses for vehicleswww.mostnet.de.
Byteflight: A databus protocol developed by BMW for safety-critical applications such as airbag control. Like MOST, it relies on 650 nm LEDs and PMMA fibre but operates at a lower data rate of 10 Mbit/s. Instead of discrete transmitter-receiver pairs it uses integrated transceivers to provide bi-directional communication over a star-network that is linked to sensors and airbag actuators. To date some 7 million Byteflight transceivers are on the road in a range of BMW cars, including the 7 series. See www.byteflight.com.
FlexRay: The FlexRay consortium is developing a POF-based communication system to enable "drive-by-light" systems. The idea is to replace the mechanical actuators that implement a car's steering, braking and gear shifting with fully electronic systems connected by a POF infrastructure. The FlexRay consortium was formed in 2000 and consists of seven core members (DaimlerChrysler, BMW, Bosch, Motorola, Philips, General Motors and Volkswagen) and more than 50 associate members. See www.flexray-group.com.
IDB-1394: An initiative between the IDB (Intelligent Transportation System Data Bus) Forum and the 1394 Trade Association to create a protocol for vehicles based on the popular IEEE 1394b data format (FireWire). This format transfers data between computers and peripherals such as digital camcorders and MP3 players at speeds of up to 400 Mbit/s. The idea is to fit cars with a customer convenience port (CCP) that allows users to take devices from the home and plug them into their car. An IDB-1394 network within the car would enable the high-speed transfer of high-definition TV, uncompressed video from a blind-spot camera, or the transfer of Super Audio CD. Such a network is likely to appear in 2006-2007.
• Paul Polishuk is president of Information Gatekeepers Inc (IGI), a market analyst firm that specialises in POF. He is also co-chair of the POF trade organization POFTO. For more information about IGI and POFTO, visit: www.igigroup.com and www.pofto.com.