Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
  • H04B10/40—Transceivers

Definitions

• the field of the invention relates generally to fiber optic networks, and more specifically, to methods and systems for providing full avionics data services over a single fiber using two wavelengths.
• Full data services at least it relates to an avionic computer, generally means transmission and/or reception of mission data (control and/or sensing), health maintenance status, and configuration data loading.
• the electrical data links utilized in most aircraft incorporate a first twisted pair of conductors to transmit signals, and a second twisted pair of conductors to receive sensing and/or control data.
• interfaces for file transfer functions such as configuration data loading and health maintenance data are also required and utilized. While about 10% of aircraft data links are high speed backbones that often require full duplex operation such as a switched network, the other 90% are lower speed access networks that typically use half duplex operation on a multicast or bus network.
• aircraft sensing and/or control data is periodically transmitted (or received) and these messages are generally a fixed size.
• File transfer data messages are not periodic. Instead, file transfer data messages are transmitted on demand and are generally of irregular file size. Data loading messages are necessary to change the configuration of airborne computing equipment to adapt to different computing applications and flight missions.
• Health maintenance messages are one type of file transfer data messages that are incorporated and utilized to report health status of aircraft equipment for fast maintenance action and avoidance of long turn around time at an airport. Due to increasing functionality and capability of avionic equipment, health maintenance and configuration data have increased exponentially for each new aircraft configuration. Navigation databases and intelligent engine messaging are relevant examples of applications with large amounts of configuration and health maintenance data.
• Such data can take several hours to transfer, however, turn around times at airport terminals are generally limited to about fifteen minutes. It is relatively easy to contemplate that it is costly for an aircraft to be grounded for maintenance. Typically, health maintenance data is time shared with control data on the same data link. Therefore, bandwidth would be reduced and the latency and jitter of the critical control data would be increased to accommodate the additional health maintenance data traffic.
• multiple pairs of copper wiring are used to send and receive sensing data, control data, configuration data, and health maintenance data.
• a file to be transferred such as a health maintenance data file
• a health maintenance data file is disassembled into dozens or hundreds of smaller pieces, so the transmission of this data can be time multiplexed with control data in the same stream. These pieces must be reassembled into the health maintenance data file at the receiving end.
• configuration and health maintenance data is time shared with control data on the same data link. Transmission of health maintenance data, for example, reduces the bandwidth available for the control data in order to accommodate additional health maintenance data traffic.
• One possible result is additional latency and jitter of the critical control data, since the computer has to perform tasks to separate the different data types and disassemble (or reassemble) data files as mentioned above.
• File transfer data messages such as health maintenance messages must either be time shared with control data on a single data link or enabled utilizing a separate data link.
• the loading of new configuration data for an article of aircraft equipment can be delayed and performed at a convenient time, such as when the subject computer is not in mission operation mode, the health maintenance data needs to be transmitted concurrently to provide for the desired goal of fast maintenance actions. It is desirable to perform configuration data loading processes in real time, for example, to reconfigure one or more avionics computers "on the fly" to adapt to different phases of a single flight.
• the method includes transmitting a first data package across the single optical fiber at a first wavelength, and transmitting a second data package across the same optical fiber at a second wavelength, in either the same direction or in a direction opposite as the first data package, wherein the second data package transmission may be concurrent with the first data package transmission.
• the method also includes separating the data package transmissions into two optical paths, filtering the second wavelength from a first of the two optical paths, detecting the first data package at the first wavelength, filtering the first wavelength from a second of the two optical paths; and detecting the second data package data at the second wavelength.
• an optical transceiver in another aspect, includes a first optical transmitter and receiver pair configured for operation at a first wavelength, a second optical transmitter and receiver pair configured for operation at a second wavelength, and an optical coupler configured to couple optical signals from the first optical transmitter and receiver pair and the second optical transmitter and receiver pair, and route the coupled optical signals from the optical coupler to a single optical fiber.
• an avionics unit includes a processing device, a computer memory associated with the processing device, an optical transceiver, and at least one communication controller configured to provide a communications interface between the processing device and the optical transceiver.
• the memory is configured to store at least application data, health maintenance data, and configuration data associated with the avionics unit.
• the optical transceiver includes a first optical transmitter and receiver pair configured for operation at a first wavelength and a second optical transmitter and receiver pair configured for operation at a second wavelength.
• the application data is transmitted from and received by the processing device via the first optical transmitter and receiver pair.
• the configuration data is received by the processing device via the second optical transmitter and receiver pair.
• the health maintenance data is transmitted from the processing device via the second optical transmitter and receiver pair.
• a network for providing full avionics data services over a single optical fiber includes a first avionics unit comprising an optical interface, a second avionics unit comprising an optical interface, and a single optical fiber configured to provide at least a portion of a communications path between the first avionics unit and the second avionics unit.
• Each optical interface includes an optical transceiver comprising a first optical transmitter and receiver pair configured for operation at a first wavelength and a second optical transmitter and receiver pair configured for operation at a second wavelength.
• a communications system in another aspect, includes a plurality of hubs and a plurality of modules.
• Each hub includes a plurality of optical interfaces, and each module includes at least one optical interface.
• Each module is optically coupled to at least two of the hubs.
• Each of the optical interfaces includes an optical transceiver having a first optical transmitter and receiver pair configured for operation at a first wavelength and a second optical transmitter and receiver pair configured for operation at a second wavelength.
• Figure 1 is a diagram illustrating an optical interface for a dual channel, optical fiber transceiver.
• Figure 2 is a functional diagram of an avionic computer that incorporates two of dual channel, optical fiber transceivers shown in Figure 1.
• Figure 3 is a diagram illustrating a system architecture that incorporates the avionics computer of Figure 2.
• the described embodiments address the problems described above through utilization of a single optical fiber network that operates with only two wavelengths of light.
• the embodiments allow a full avionics data service on a single optic fiber network through the implementation of substantially simultaneous transmission of sensing and control data (bidirectional across the fiber) and file transfer data (including configuration data loading in one direction across the fiber and health maintenance data in the other direction across the fiber).
• FIG. 1 is a diagram illustrating an optical interface for a dual channel, optical fiber transceiver 10.
• Transceiver 10 includes a passive optical Y-coupler 12 for separating and combining optical signals.
• transceiver 10 is a chip-on-chip transceiver that incorporates a LED (Light Emitting Diode or Laser Diode) and a PD (Photo Detector).
• Transceiver 10 is compact and low cost.
• transceiver A 14 transmits and receives optical signals at a first wavelength while transceiver B 16 transmits and receives optical signals at a second wavelength.
• the passive optical Y-coupler 12 acts as a combiner for transceivers A
• low cost dielectric filter films 18 and 20 have central cut outs, 22 and 24 respectively, therein to allow for the LED to transmit unimpeded through the respective cut out while filtering out the second wavelength, and preventing it from reaching the respective photo detector (and allowing the first wavelength to reach the photo detector.)
• the transceiver 14 includes a transmitter (LED) 30 and a receiver (photo detector) 32 operating at a first wavelength.
• the filter 18 allows the transmission from transmitter 30, at the first wavelength, through the cut out 22, and also allows the reception of signals at the first wavelength at receiver 32, through the filtering portion 40 of filter 18.
• the filtering portion 40 of filter 18 prevents optical signals at the second wavelength from reaching the receiver 32.
• the transceiver 16 includes a transmitter (LED) 50 and a receiver (photo detector (PD)) 52 operating at a second wavelength.
• the filter 20 allows the transmission from transmitter 50, at the second wavelength, through the cut out 24, and also allows the reception of signals at the second wavelength at receiver 52, through the filtering portion 60 of filter 20.
• the filtering portion 60 of filter 20 prevents optical signals at the first wavelength from reaching the receiver 52.
• transmission and reception may be simultaneous, as long as the wavelengths are different.
• an optical signal at a first wavelength may be received at receiver 30 while a signal at a second wavelength it emanating from transmitter 52.
• the shape of the Y-coupler 12, filters 18 and 20, and the transceivers 14 and 16 is somewhat arbitrary.
• the square shape associated with filters 18 and 20, and transceivers 14 and 16, is but one example.
• Other embodiments, such as round, rectangular, triangular, and other shapes may be implemented.
• the same constraints apply to the Y-coupler 12, which may have a cross-section that is other than round.
• the chip-on-chip transceiver incorporating both dual transmitters (LEDs) and dual receivers (PDs) enables compact size and low cost for a dual transceiver. For example, if first and second wavelengths are used, the first transceiver transmits and receives at the first wavelength, while the second transceiver transmits and receives at the second wavelength.
• the passive optical Y-coupler 12 acts as a combiner for the two transceivers in the transmit direction and acts as a splitter in the receive direction.
• the low cost dielectric filter film has a cut out in the middle to allow for the LED associated with the first wavelength to transmit unimpeded therethrough while the outer perimeter of the filter film filters out the second wavelength from reaching the photo detector, and also allowing the first wavelength to pass through to reach the photo detector.
• Other configurations for the filter may be implemented, based on the configuration of the transmitting LED with respect to the receiving photo-detector.
• Y-coupler may be fabricated used plastic or glass, based on the wavelengths of the light used. As is well known, plastic is often used in the visible light range while glass is often used in the infrared light range.
• the Y-coupler maybe implemented using a variety of methods including tapered optical fiber, silicon waveguide or polymer waveguide.
• FIG 2 is a functional diagram of an avionic computer 100 that incorporates two of the dual channel, optical fiber transceivers described above.
• Transceivers 102 and 104 each provide an optical fiber communication interface.
• Avionic computers of the type similar to avionic computer 100 are sometimes referred to as line replaceable units (LRUs) and transceivers 102 and 104 are functionally equivalent to transceiver 10 (shown in Figure 1).
• LRUs line replaceable units
• avionics computer 100 includes one or more host processors
• application data 130 is routed bi- directionally to and from the processors 110 and 112 through the communications controllers 120 and 122.
• the communications controllers 120 and 122 are communicatively coupled to both transceivers 102 and 104, which are respectively coupled to individual single fiber busses 140 and 142.
• the application data 130 is transmitted and received on the busses 140 and 142 at a first wavelength.
• Configuration data 132 is received on the busses 140 and 142 at a second wavelength, filtered by the filters and routed to the memory through the transceivers 102 and 104, communications controllers 120 and 122, and processors 110 and 112.
• Health maintenance data 134 is retrieved from the memory by processors 110 and 112, forwarded through the communications controllers 120 and 122 to the transceivers 102 and 104 and transmitted on the busses 140 and 142 at the second wavelength.
• the transceivers 102 and 104 are configured as described above with respect to transceiver 10 in that they include a first transmitter and receiver pair (150 and 160 respectively) operating at a first wavelength (based on the filters 170 and 172) and a second transmitter and receiver pair (152 and 162 respectively) operating at a second wavelength (based on the filters 174 and 176).
• the filters associated with each transmitter/receiver pair are utilized as described above.
• Filters 170 and 172 allow the transmissions therethrough from transceivers 150 and 160, at the first wavelength (application data to be transmitted on busses 140 and 142), through a cut out (not shown in Figure 2), and also allows the reception of signals at the first wavelength (application data received via busses 140 and 142) at transceivers 150 and 160, through the filtering portion of the respective filter 170 and 172.
• the filtering portion of filters 170 and 172 prevent optical signals at the second wavelength (configuration data and health maintenance data) from reaching the transceiver 152 and 162.
• filters 174 and 176 allow the transmission from transceivers
• Each avionic computer or LRU in a system architecture typically incorporates dual redundant data links for fault tolerance and resource availability. Whether the LRU deploys a single microprocessor or dual microprocessor architecture depends on the requirement for that avionic system.
• each processor 110 and 112 is communicatively coupled to two communication controllers 120 and 122.
• the controllers can be of the same type, or they may be different, incorporating one or more communication protocols for flexibility.
• Each controller 120 and 122 is communicatively coupled to two optical transceivers 102 and 104 in a crossed strap configuration to allow the optical fibers to carry dual, but distinguishable optical communication protocols. Through the utilization of bidirectional, half duplex transceivers, only two wavelengths are needed to handle all sensing/control data (application data) and all configuration and health maintenance data.
• FIG. 3 is a diagram illustrating a system architecture 200 that incorporates avionics computer 100 and multiple other avionics LRUs 202, 204, and 206, each of which provides one or more specific avionic functions.
• Avionics computer 100 and avionics LRUs 202, 204, and 206 are collectively referred to as avionics units.
• System architecture 200 further includes a central health maintenance database 210 and a configuration database 212.
• Avionics computer 100, avionic LRUs 202, 204, 206, central health maintenance database 210 and configuration database 212 are communicatively interconnected utilizing a multi-port network hub controller 220.
• Communication channels are redundant in that each of the components of system architecture 200 are connected to busses 140 and 142 (also shown in Figure 2) and at least the avionics computers (LRUs) (100, 202, 204, and 206) incorporate the transceiver/filter configurations described herein. As all of the components of system architecture 200 incorporate the above described embodiments, full avionic data service over a single optical fiber results.
• busses 140 and 142 also shown in Figure 2
• LRUs avionics computers
• Each avionics LRU incorporates and utilizes dual redundant optical fibers for fault tolerance, and each optical fiber carries dual first and second wavelengths to provide the full avionic data transmission services that have been described herein.
• Dual redundant network hubs such as multi-port network hub controller 220, are implemented within system architecture 200 for fault tolerance with each avionic computer/LRU connected to each of the multiple controllers.
• Each network hub controller 220 is utilized to connect the optical interfaces of multiple avionic computer/LRUs together, as well as to provide an interface to the central health maintenance database 210 and configuration database 212.
• These network hub controllers 220 can be cascaded to connect as many avionic computer/LRUs as allowed by the implemented communication protocols.
• Either active hubs (with active optoelectronics) or passive hubs (no electronics) can be utilized, depending on the quantity of LRU nodes on the data bus. Obviously a passive hub can only divide optical power to a limited number of nodes. Also, both active and passive hubs can be utilized in a mixed topology.
• the channel having a wavelength associated with the configuration data/health maintenance data can be utilized to supplement the sensing/control (application) data channel.
• both channels can be used to increase the data bandwidth.
• the units receiving and supplying such data would have to be operable at both wavelengths so that the filtering mechanisms described herein would not impede communications.
• both channels would have to utilize the same communication protocol.
• a file transfer channel can utilize a different communication protocol from the control data channel.
• full duplex operation of sensing/control (application) data can be achieved by replacing the half duplex transceiver with a full duplex transceiver.
• Such a transceiver has a separate LED and photodetector within the same package (not chip on chip), and utilizes different wavelengths for transmission and reception of application data.
• a full duplex transceiver typically utilizes a wave division multiplexer (WDM) mirror within the transceiver to separate the two wavelengths.
• WDM wave division multiplexer
• the embodiments provide significant savings in part weight, volume, cost, fabrication, assembly, handling, inventory, installation, inspection, and maintenance.
• the embodiments invention improve bandwidth and data flow efficiency while reducing data latency and jitter.
• utilization of optical fiber instead of conventional wiring reduces airplane systems susceptibility to EMF and lightning strike.
• the embodiments described herein result in a system capable of supporting a method for adding concurrent file transfer capabilities (such as configuration data loading to a host computer and health management traffic from a host computer) to an existing sensing and control data architecture without interfering with the transmission and reception of sensing/control data, and without adding any wiring to an aircraft.
• the above described architecture utilizes only two optical wavelengths, while still supporting a full avionic data service, and utilizing a single optical fiber (a second optical is provided for redundancy.
• the described embodiments support bidirectional, half duplex transmission and reception of control/sensing (application) data and bidirectional, half duplex configuration data loading and health management data transmissions.
• the embodiments support simultaneous operation of same or different communication protocols, one for sensing/control (application) data and one for configuration and health maintenance data.

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