The application of POF in automobile industry
  • The reasons to employ POF in the car
      In automotives, electronic control, higher speeds for GPS, video anti-skid brakes, and audio system  and sensing systems like collision detection are growing in sophistication. As automobiles become more and more complicated, the weight and volume of copper- based networks creates a problem for new automobile designs. New technologies have to push the limits of the traditional automotive wiring harness, which carries both electrical power and control signals.
    The get around those limitations, cost-conscious automotive engineers are finally turning to POF. .A single POF can replace many individual copper wires(existing copper wiring harnesses), resulting in major weight and space savings. The exchange of the communication medium delivers lower weight. For example, in the Mercedes S-Class the weight was reduced by about 50Kg due to POF replacing cooper.
     Table 1     Comprarison of POF and copper wiring for automotives
                                                 POF                                                Copper
                                                -Small                                                    -Heavy
                                                -Lightweight                                         -Bulky
                                               -Immune from EMI                              -Susceptible to EMI
                                               -Higher bandwidth                             -Low bandwidth
                                               -Cab be formed into a network      -Simple point to point links
                                               -Easy to maintain                               -Difficult to maintain
                                               -Cheap                                                  -Number of  copper wires increases dramatically as new amenities are added to automobiles
   According to BMW, the current copper cable inevitably generate electromagnetic noise problem whenever the data transmission speed exceeds 500kbps. Obviously, the future data transmission speed tendency is becoming faster and faster, the problem will become more serious. Under this circumstance, POF will be a final solution. Start from now on is better than start late anyway. In this way, the connector design do not need to care about electromagnetic noise, thus the costs become much lower.
     Luxury cars were traditional starting place for POF technology. As the system cost is reducing, POF starts to go into medium class and even ordinary cars eventually.
After years of development, POF systems have been around for more than 20 years in automotive and have a strong impact on the wiring harness business. The first applications are in high-end broadband entertainment and information systems, linking compact-disc (CD) changers, audio systems, and speakers throughout the car, delivering navigation information to the driver, and providing video entertainment to passengers. The automotive sector has been the most successful POF application to date, with millions of cars already equipped with POF-based networks using the MOST (Media Oriented Systems Transport) standard. Whether it’s a BMW or Audi car, POF is becoming a must-have option for in-vehicle networks.
    Automotive manufactures are keen to exploit POF technology for connecting car infotainments systems and even some safety-critical applications such as airbags. Today’s high-end cars are processor intensive, supporting devices such as radio, CD, DVD, navigation systems, Bluetooth, telephones, TV tuners, gaming and even internet, etc.
    Next generation car specifications will easily observing trends in home networking, same service as in the office and home. POF will connect up the ever-increasing number of in-car electrical devices such as  TV, computer, fax machine also into a car.
Besides, the benefits for the automotive manufactures are clear: POF offers a high operation bandwidth, increased transmission security and reliability, immunity to EMI and anti-shock, ease of handling, connection and installation, flexibility and long shelf life. Crucially, it’s also a low-cost option.
  • D2B ( a POF premium audio-distribution system)
   D2B is the result of an extensive development program that aims to realize an automotive communications and information network. The D2B optical network is based on distributed devices such as head units, CD players, speech-control units, telephones, and Internet-access units. The D2B enables complex and distributed functions, minimizes electromagnetic-interference problems, decreases weight and cost, and achieves a high data rate of up to several megabits per second. Daimler-Chrysler recognized the potential of this medium and introduced a POF premium (15 meters) audio-distribution system (D2B) into its Series Mercedes-Benz S series back in Nov 1998.
      D2B optical network is a synchronous bus with a ring structure in which two devices each build an optical point-to-point link to the ring. The head unit serves as a network master and each D2B device is equipped with a network transceiver chip that serves the physical layer. The optical cabling to interconnect all network devices inside the car consists of POF.
The introduction of the D2B optical network represents the first step toward enhancing the capability of automotive multimedia applications. The integration of World Wide Web services with automotive network devices such as intelligent traffic guidance is the start of an evolution that promises both technological challenges and new solutions.  It soon became apparent that a more sophisticated protocol was needed.
  • MOST (Media-oriented systems transport)
     MOST, a bus protocol, promoted and organized by the MOST Cooperation (Karlsruhe, Germany) and  led by Daimler Chrysler, BMW and Audi, was devised in the late 1990s to meet the rapidly increasing in-car data bandwidth for vehicle enterinment systems, where plastic optical fiber can replace literally miles of copper cabling required for automotive systems.  MOST25 initially offered 25Mbps and more recently, MOST50 offers up to 50Mbps data bandwidth using POF as the physical media. The bandwidth will soon jump to 125 Mbps.
     Currently 19 car makers are members and there are over 6 million MOST nodes on the road, with over 10 million nodes/year predicted from 2005 onwards. Over 22 models of car are equipped with MOST systems so far, with the Mercedes E-Class and S-Class, BMW7 Series, Porsche Cayenne, Saab9-3, Audi A8 , and Volve XC-90 among the first to deploy the technology commercially and new BMW 7 Series has more than 100 meters of POF in it.
      Now Jaguar, Land Rover, Fiat, Peugeot, Citroen also are producing MOST cars.
 Figure 1. In a MOST network, fiber links form a ring connecting components such as mobile phone receivers, radios, speakers, DVD and CD players, computers
     Both BMW and Mercedes have announced plans to equip all their lines of cars with MOST-equipped cars including BMW5 and BMW3 Series.
With MOST, the automotive industry developed a unified standard that everybody abides to, with the intention of driving cost down.
  • IDB-1394
     Like MOST standard, IDB-1394 standard relys on the combination of POF and 650nm red light sources.The 1394 Trade Association, best known for its FireWire standard for video and computer data transfer, has an Automotive Working Group developing a version of the standard for car use. Like MOST, the 1394 standard has seven layers, with point-to-point links running between plug-and-play devices. However, the topology is a tree or star, with devices branching out from each other rather than arranged in a ring like MOST (see Fig. 2). The point-to-point links between devices contain two fibers, one for sending data, the other for receiving it. The IDB-1394 POF network enables a reduction in the shielded wiring, and offers a cost-effective solution when compared with existing analog system technology.

Figure 2. In the tree geometry of the 1394 network, point-to-point links branch off other devices. Typically two fibers run between devices, one for sending and one for receiving
   Unlike MOST, the 1394 standard accommodates several types of cable: 1000-µm plastic fiber, hard-clad glass fibers, shielded twisted-pair copper cable, and category 5 copper cable. Each link can run up to 100 m between devices, and the network can contain a total of 63 devices. The design can handle both streaming video signals and asynchronous signals such as computer data.
The original copper-cable version of the 1394 standard operated at up to 400 Mbps, but was limited to runs of 4.5 m by the use of copper cable. The enhanced 1394b version can carry data rates to 800 Mbps over distances to 100 m over plastic fiber or category-5 cable. Future plans call for increasing data rates to 3.2 Gbps. The final standards are in the approval process.
Renault has  played a major role in 2004 to advance the IDB-1394 standard .The transport of three simultaneous video streams, DVD player, digital TV and a camera can be used for real riew parking assistance. Navigation and hot plug-and-play access to an Apple iPOD is included, along with three displays. One display is for front seat and two for back seat passengers. The concept of the demo is simple: to show how to entertain rear and front passengers according to each individual choice.
    General Motors and Toyota and other Japanese car makers are planning to install IDB-1394 in their new car designs.
  • ByteFlight
    And it’s not just navigation and entertainment functions that can exploit POF. BMW, in conjunction with several electronics firms,  has developed a 10Mbps protocol called ByteFlight, which it uses it support the rapidly growing number of sensors, actuators (airbag) and electronic control units within cars, intended for safety-critical applications.Unlike MOST, which employs real-time data transfer, Byteflight is a deterministic system in which the focus is on making sure that no data is lost. This deterministic behavior is vital for safety. Developers picked optical fiber because of its immunity to electromagnetic interference.
BMW began using Byteflight in its 7 Series cars in 2001, in which 13 electronic control units are connected, including accelerometers and pressure sensors to detect when seats are occupied.

Figure 3. Sensors using plastic optical fiber embedded within the framework of an automobile can be used to provide pedestrian protection. The transmission signal changes when a surface-treated zone on the fiber is bent. Analysis of the signal from several parallel fiber strands allows the system to determine the nature of the object impacting the vehicle. The sensor can distinguish between a human and an inanimate object, triggering the hood to lift and softening the impact if a human is struck. Transmission shifting is also done through the fiber network.
  In 2006, BMW’s Series 7 models added ByteFlight to control the airbag system on its new Z4 roadster. The vehilcel contains 12 sensors velocity, acceleration and pressure sensors, distributed in a star system and linked via POF (43 meters long). The system operates as a computer cluster with distributed functionality in order to evaluate the sensor data and fire the required air bags in case of accident. And in 2007 BMW extended fiberoptic airbag control to its new 5 Series cars.
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