Abstract:
The present disclosure describes a system for notification, during flight and on ground, of the relative quality between two redundant optical data distribution networks on an aircraft, which are used for remote surveillance of refueling activities where there is no need to disconnect a fiber optic connection to make the quality assessment.

Description:
BACKGROUND 
     Many newer aircraft make extensive use of optical fibers for data transmission because of EMI benefits, to reduce weight, increase data throughput, and provide other benefits. Such optical data transmission systems are increasingly being used for safety critical, on-board video surveillance systems, such as used in conjunction with in-flight refueling systems. These systems are not immune to failures and performance issues. In the past, it has been known that optical connections can get dirty, especially in dry dusty desert environments, and it has been known to deploy a technician to test such systems by disconnecting the various LRUs and checking the optical path, component by component, and link by link. This is done when the aircraft is on the ground, such as during down time; e.g. when undergoing routine maintenance or urgent repairs. 
     While this system has been employed widely in the past, it has some drawbacks. Such testing requires a skilled technician and consumes, or possibly extends, the valuable time when the aircraft is on the ground and not in service. Often such testing, or alternatively prophylactic maintenance, must be done more frequently when operating in certain environments, especially when in-flight failures may be catastrophic. 
     Consequently, there exists a need for improved systems and methods for monitoring and maintaining the integrity of optical data transmission systems on an aircraft. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to increase integrity of on-board optical data distribution systems. 
     It is a feature of the present invention to include on-board the aircraft a plurality of digital diagnostics monitoring optoelectronic interfaces, each coupled to either an LRU, a central computer or a display device. Throughout this document, an LRU is being considered as any functional electronic device in or around the aircraft. 
     It is an advantage of the present invention to provide for the ability to monitor, in-flight and in real time, live diagnostic data with respect to said digital diagnostics monitoring optoelectronic interfaces. 
     It is another feature of the present invention to include an optical network status comparison ability for redundant optoelectronic systems on an aircraft. 
     It is still another feature of the present invention to include an ability to display, in real time, live quantized optical link performance information for optical paths on an aircraft, in-flight as well as on the ground. 
     It is an advantage of the present invention to provide for an ability to increase the efficiency of optoelectronic data transmission systems on airborne aircraft. 
     The present invention is a system and method for increasing effectiveness of optoelectronic data transmission on board an airborne aircraft, which is designed to achieve the above described object, include the aforementioned features and provide the previously stated advantages. 
     The present invention includes a system and method of transmitting optical data comprising the steps of: 
     A method of determining a superior performing optical data distribution network for in-flight video surveillance information among a plurality of redundant refueling surveillance system optical data distribution networks, the method comprising the steps of:
         providing a first redundant video surveillance system performance assessment comprising the steps of:   providing a first camera which outputs first electrical video signals;   providing a first camera fiber optic transceiver for converting said first video signals from a first electrical video signal to a first optical video signal;   monitoring said first camera fiber optic transceiver for first camera diagnostic data comprising at least three of:
           temperature of said first camera fiber optic transceiver,   supply voltage of said first camera fiber optic transceiver,   transmitter bias current of said first camera fiber optic transceiver,   optical transmit power of first camera fiber optic transceiver,   
           optical receive power of first camera fiber optic transceiver; and
           optical time domain reflection measurements;   
           providing a first computer which processes first electrical digital data;   providing a first computer fiber optic transceiver for converting said first electrical digital computer data to first optical digital computer data;   monitoring said first computer fiber optic transceiver for first computer diagnostic data comprising at least three of:
           temperature of said first computer fiber optic transceiver,   supply voltage of said first computer fiber optic transceiver,   transmitter bias current of said first computer fiber optic transceiver,   optical transmit power of first computer fiber optic transceiver,   optical receive power of first computer fiber optic transceiver; and   optical time domain reflection measurements;   
           providing a first display device for displaying an image representative of said first electrical video signals;   providing a first fiber optic link between said first camera, said first display device and said first computer which carries said first optical video signals and signals representative of said first camera diagnostic data;   without disconnecting a fiber optic connection, making a quantitative assessment of performance based upon an optical link budget based upon performance of said first camera fiber optic transceiver, and said first computer fiber optic transceiver and said first fiber optic link;   providing a second redundant video surveillance system performance assessment comprising the steps of:
           providing a second camera which outputs second electrical video signals;   providing a second camera fiber optic transceiver for converting said second video signals from a second electrical video signal to a second optical video signal;   monitoring said second camera fiber optic transceiver for second camera diagnostic data comprising at least three of:
               temperature of said second camera fiber optic transceiver,   supply voltage of said second camera fiber optic transceiver,   transmitter bias current of said second camera fiber optic transceiver,   optical transmit power of second camera fiber optic transceiver, and   optical receive power of second camera fiber optic transceiver;   
               
           providing a second computer which processes second electrical digital data;   providing a second computer fiber optic transceiver for converting said second electrical digital computer data to second optical digital computer data;   monitoring said second computer fiber optic transceiver for second computer diagnostic data comprising at least three of:
           temperature of said second computer fiber optic transceiver,   supply voltage of said second computer fiber optic transceiver,   transmitter bias current of said second computer fiber optic transceiver,   optical transmit power of second computer fiber optic transceiver, and   optical receive power of second computer fiber optic transceiver;   
           providing a second display device for displaying an image representative of said second electrical video signals;   providing a second fiber optic link between said second camera, said second display device and said second computer, which carries said second optical video signals and signals representative of said second camera diagnostic data;   without disconnecting a fiber optic connection, making a second quantitative assessment of performance based upon an optical link budget based upon performance of said second camera fiber optic transceiver, and said second computer fiber optic transceiver and said second fiber optic link;   comparing said first quantitative assessment of performance and said second quantitative assessment of performance while said first fiber optic link is on a refueling tanker which is airborne; and   providing to a person onboard said refueling tanker with a live indicator of superior performance between said first redundant video surveillance system and said second redundant video surveillance system.       

    
    
     
       BRIEF SUMMARY OF THE DRAWINGS 
         FIG. 1  shows an aircraft, with an inset of a cockpit and a simplified optical network. 
         FIG. 2  shows a digital diagnostics monitoring opto-electronic interface of the present invention. 
         FIG. 3  shows a more detailed view of a portion of the optical network of  FIG. 1 , including digital diagnostics monitoring opto-electronic interfaces of  FIG. 2 . 
         FIG. 4  shows a simplified version of redundant video surveillance systems on a refueling tanker. 
         FIG. 5  is a block diagram view of the internal portions of the data interpreter of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Now referring to  FIG. 1 , there is shown a cartoon drawing of an avionics system with an optical data network. The system could be any type of avionics system such as, but not limited to, a video surveillance system for use in refueling aircraft. Such a system, and other systems, may comprise of a central computer  10 , which can be any type of computer, router, hub or any other electronic device which is coupled to more than one other device via fiber optic cable. In this example, it is a central control computer for an aircraft. Coupled to central computer  10  is a digital diagnostics monitoring optoelectronic interface  20 , which can be a somewhat standardized device, which converts electronic signal to optical signal, and vice versa, then communicating with other LRUs through a fiber optic link, such a links A, B and C, which are well known in the art but may preferably be multi-mode optical fibers and may be uni-directional or bi-directional optical fibers. Also shown is a LRU  12 , which could be located remotely in the aircraft, such as, but not limited to, a video camera, a GPS receiver, an accelerometer or any other device located in or around the aircraft  1 , which has a digital diagnostics monitoring optoelectronic interface  20  attached thereto for converting from optical to electronic, and vice versa, digital optical signals received from or sent over the optical network. Also shown on aircraft  1  is an inset view of a cockpit  2  of the aircraft  1 , which shows, among other things, a first platform display device  14  and a second platform display device  16 , each of which is shown with a digital diagnostics monitoring optoelectronic interface  20  coupled thereto.  FIG. 1  could have been drawn without the inset and with very short lines A and C running to boxes  14  and  16 , each with a box  20 , all located in the cockpit area of the aircraft. 
     If the aircraft  1  is a refueling tanker, then LRU  12  may be a video surveillance system, or a portion thereof, such as a video camera assembly. In a typical refueling tanker, there are redundant video surveillance systems and stations, so in such an application there could be another LRU, which is substantially the same as LRU  12 . The optical network of  FIG. 1  is simplified and is shown as a representative simple airborne avionics optical data transmission network. More elaborate networks are envisioned and are believed to be enabled by this simplified example. 
     Now referring to  FIG. 2 , there is shown a more detailed view of the novel digital diagnostics monitoring optoelectronic interface  20  of  FIG. 1 , which includes a fiber optic transceiver  22 , which can be a single device for both transmitting and receiving data, and converting the data from electrical data to optical data, or vice versa. It may also be a dedicated receiver or dedicated transmitter, or any combination of multiple transmitters mixed with multiple receivers, which will herein be referenced as only fiber optic transceivers. One example of a fiber optic transceiver that is commercially available is the RJ-3G-SXHP-D-DPLX-LC-R-A device available from the COTSWORKS company located in Highland Heights, Ohio. A dedicated fiber optic receiver  22  would receive optical data via an optical link, such a links A, B and C, and convert the data to electrical data, provide that electrical data to a data interpreter  24  module via an electronic data line  26 , which may be an electronic high speed serial data bus. High speed electronic data line  26  is shown with a Clock Data Recovery block disposed therein for providing necessary signal conditioning. The A818 signal may be a 3.1875 Gbps ARINC 818 signal, but may be any electrical data bus. The data interpreter  24  could be performed by various types of hardware, including, but not limited to, a field programmable gate array (FPGA) such as the EP2AGX45DF25I5 Arria II device from Altera. The fiber optic transmitters  22  receive high speed electronic data from the data interpreter  24  via the high speed electronic data line  26  and convert it to optical data to be transmitted on the fiber optic links. 
     Disposed between data interpreter  24  and fiber optic transceivers  22  is also a digital diagnostic data line  28 , which may be a Two Wire Serial Interface (TWSI), which is a 100 Khz bus with a clock line and a data line. The TWSI is the interface used by the data interpreter  24  to gather the diagnostics data from the one or more fiber optic transceivers  22  that may be connected to data interpreter  24 . This diagnostic data may include temperature, supply voltage, transmit bias current, optical transmit power, optical receive power, as well as other faults, flags and monitoring information. 
     The data interpreter  24 :
         receives high speed electrical data from the fiber optic transceivers  22 ;   transmits high speed electrical data to the fiber optic transceivers  22 ;   continuously gathers diagnostics data from the fiber optic transceivers  22 ;   continuously gathers data from the external electrical interface, which may be a 5 Gbps Gen 2 PCIe bus;   responds to commands from the external electrical interface to read specific information;   sends out requested data on the external electrical interface;   responds to commands from the external optical interface to read specific information;   sends out requested data to the high speed electrical interface with the fiber optic transmitter, where it is converted from electrical to optical and sent onto the external optical interface.       

     The data interpreter  24  can gather data from the optically received data, digital diagnostics data, and external electrical interface. It puts that data into internal memory for current or future manipulation, and can send that data out either via the external optical interface or the external electrical interface. The data interpreter  24  may provide data to, and receive data requests from, central computer  10  or other sources. These data requests may be intermittent or may, in some applications, be periodic, e.g. per cycle or every second etc. A more thorough understanding of the data interpreter  24  can be achieved by referring to  FIG. 5 , which shows some of the internal structures and organization. 
     Now referring to  FIG. 3 , there is shown an alternate embodiment of the simplified network of the present invention, which includes an LRU#1, which includes integrated therein (inside the LRU), a digital diagnostics monitoring optoelectronic interface  20  and some other functionality, such as is shown in  FIG. 1  as LRU  12 . The main difference between LRU  12  and digital diagnostics monitoring optoelectronic interface  20  in  FIG. 1  is that digital diagnostics monitoring optoelectronic interface  20  is shown in  FIG. 1  as an add-on device; but in  FIG. 3 , LRU  12  and digital diagnostics monitoring optoelectronic interface  20  are combined into a single LRU#1. Similarly, the central computer  10  and digital diagnostics monitoring optoelectronic interface  20  of  FIG. 1  are integrated in  FIG. 3  into a single central computer, which itself may be a LRU. The remainder of the system of  FIG. 1  is also shown, including platform display device  14  and platform display device  16 , and optical links A, B and C. Also there is shown an electrical interface which couples the central computer  10  with the platform display device  14  and platform display device  16 , that may be used as an alternative way to get the fiber link information to the platform. 
     In operation and now referring to  FIG. 4 , there is shown a system of the present invention which could be adapted and employed on a KC-46 Tanker as follows: 
     There are two parallel and redundant systems for refueling aircraft on board the tanker. Each of the redundant systems has a central computer  10 , which is configured to communicate with a camera LRU  12  through its optical interface. The digital diagnostics data, as well as the video from LRU#1, is transmitted to the central computer  10  through its fiber optic interface. The data interpreter  24  of the central computer then gathers the digital diagnostics data from the LRU #1, as well as its own digital diagnostics information. All of this information is then presented to the central computer&#39;s processor. When the system monitors the optical power transmitted at one point in the optical data path, and then measures the power that same data is received at a remote location, the processor then has the capability to logically break the optical network into a series of point-to-point transmissions and examine and quantitatively assess all of the fiber optic links between any two optically coupled LRUs on the aircraft, including the two shown LRUs (central computer LRU and camera LRU#1) and present that information to the platform display devices  14  and  16 , where it is accessible by the user. This information can be delivered to the platform interface either optically or electrically. However, it may be preferred that the platform interface also have digital diagnostics monitoring optoelectronic interface  20 , then the central computer could generate a budget of all of the losses in the links between the camera, the central computer and platform interface as well. 
     Since there are two redundant systems for video surveillance of the remote fueling tanker, these link budgets can be easily compared between the two redundant systems to determine which has the highest performance and therefore is the more reliable of the two. A visual indicator, or light  40 , could be located at each of the redundant refueling stations, and be illuminated with a color of light, such as green, for acceptable and the best of the two redundant systems, yellow for acceptable and the lesser of the two redundant systems, or red meaning the link budget is below the acceptable threshold. Other visual indicators (such as icons in a GUI or any other visual representation) could be used for easy display of the relative quality of the optical network during in-flight operation, and immediately in advance of selecting one of the redundant systems for refueling an aircraft. 
     The system of the present invention is easily scalable from the simplified systems shown by adding as many LRUs as required for the platform. LRUs  1 ,  2 ,  3 ,  4 , etc. could all be connected to one or more central computers. The central computer could then figure all of the optical link budgets in the airplane and present that information to the platform interface. The central computer can be any device capable of gathering the information from the data interpreter and then presenting that information to the platform interface. 
     One especially valuable aspect of the present invention is the ability to do end of life (EOL) monitoring and prediction for fiber optic transceivers  22  and components thereof. Depending upon the transceivers chosen for any particular application, EOL performance data can be input from a manufacture, or stored onboard during the life of the fiber optic transceivers  22 . Typically, before failure of a fiber optic transceivers  22 , there are changes in the performance ratios, e.g. optical power output as a function of drive current or voltage. When such ratios exceed predetermined limits, EOL warnings can be issued, or otherwise utilized in internal maintenance prescriptions, to be issued by the controlling computer. Reducing the number of times that fiber optic transceivers  22  fail during flight can be a very valuable aspect of the present invention.