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WO1991020138A1 - Transmission par fibre optique de signaux electroniques a trois niveaux - Google Patents

Transmission par fibre optique de signaux electroniques a trois niveaux

Info

Publication number
WO1991020138A1
WO1991020138A1 PCT/US1991/004183 US9104183W WO9120138A1 WO 1991020138 A1 WO1991020138 A1 WO 1991020138A1 US 9104183 W US9104183 W US 9104183W WO 9120138 A1 WO9120138 A1 WO 9120138A1
Authority
WO
WIPO (PCT)
Prior art keywords
message
pulse
line
fiber optic
signals
Prior art date
Application number
PCT/US1991/004183
Other languages
English (en)
Inventor
Michael L. Canestri
Ross D. Capen
Kevin F. Keefe
Original Assignee
Light Wave Communications, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Light Wave Communications, Inc. filed Critical Light Wave Communications, Inc.
Publication of WO1991020138A1 publication Critical patent/WO1991020138A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L12/403—Bus networks with centralised control, e.g. polling
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M5/00—Conversion of the form of the representation of individual digits
    • H03M5/02—Conversion to or from representation by pulses
    • H03M5/16—Conversion to or from representation by pulses the pulses having three levels
    • 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
    • H04B10/27—Arrangements for networking
    • H04B10/278—Bus-type networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
    • H04L25/40—Transmitting circuits; Receiving circuits

Definitions

  • This invention relates to the use of optical fibers for transmission of electronic signals which are bipolar.
  • the problem leading to the present invention arose from the desire to provide a fiber optic bus extender suitable for use with the military standard data bus MIL-STD-1553.
  • Fiber optic lines are ideal carriers of optical signals derived from electronic signals on a data bus.
  • Such electronic signals may, for example, be those in aircraft internal time division command/response multiplex data buses utilized in systems integration of aircraft subsystems.
  • a fiber optic bus extender permits bus information to be optically transmitted to, and received from, a remote location, e.g., a location 500 meters or 1,000 meters from the bus.
  • the fiber optic extender is able to protect the transmitted signals from noise, in addition to its other advantages over electrical cable connections.
  • the fiber optic extender preferably has two lines, one carrying signals from a bus-connected transmitter, and the other carrying signals to a bus-connected receiver. At the other end of the extender, there may be a monitor, a remote terminal, a bus controller, or another bus.
  • Figures 1-4 illustrate possible configurations of systems utilizing a fiber optic bus extender.
  • MIL-STD-1553 In addition to the military standard data bus mentioned above (MIL-STD-1553) , there is a military standard (MIL-STD-1773) for the electrical optical interface of extenders used with 1553 buses.
  • a handbook for 1773 users describes the "electrical/optical interface (EOI) as a circuit which accepts 1553 bus signals, performs the required conversions and transmits the message to a fiber optic cable, and also receives MIL-STD-1773 messages, performs the required conversions, and couples the message in electrical form to the MIL-STD-1553 bus cable.
  • a pulse of light is transmitted by the 1773 transmitter when the received 1553 signal is positive and no light is transmitted when the 1553 signal is zero or negative.”
  • the present invention deals with the problem of combining a three signal level bus terminal with an optical system which carries only two signal levels.
  • Use of an added fiber or an added signal frequency would make the system more cumbersome and significantly more expensive.
  • the present invention provides (a) an electronic means at the transmitter for detecting the end of a given message and sending on the fiber optic extender an end-of-message signal and (b) an electronic means at the receiver for detecting the end-of-message signal and enabling the receiver to accept another message.
  • an electronic means at the transmitter for detecting the end of a given message and sending on the fiber optic extender an end-of-message signal
  • an electronic means at the receiver for detecting the end-of-message signal and enabling the receiver to accept another message.
  • Figures 1-5 are prior art material considered useful in understanding the background of the invention.
  • Figure 1 is a diagram of a complete bus and bus extender system, including two bus-to-extender terminals;
  • Figure 7 is a block diagram showing the transmitter of the end-of-message pulse
  • Figure 8 is a block diagram showing the receiver of the end-of-message pulse
  • Figure 9 provides a more detailed showing of the electronic elements which create the end-of-message pulse at the transmitter end;
  • Figure 10 is a time diagram showing the pulsing sequences at various positions in the circuitry of Figure 9;
  • Figure 11 provides a more detailed showing of the electronic elements which detect the end-of-message pulse at the receiver end; and Figures 12 and 13 are time diagrams showing the pulsing sequences in the old design and new design bus extender systems, respectively.
  • the third coupler 22 is shown connected to a unit 28 which connects the bus to duplex fiber optic cables 30 and 32.
  • Unit 28 is an electrical/optical interface (EOI) unit. It has wire connections 34 and 36 with the first coupler 22. The conversion of electrical signals to optical signals, and vice versa, in unit 28 is accomplished by electrical circuitry which includes a transformer 38.
  • the EOI unit 28 has a transmitter terminal 40 and a receiver terminal 42.
  • a pulse of light in a fiber optic cable is transmitted when the output of unit 28 or 44 is positive, and no light is transmitted when the output is zero or negative.
  • the signal transmission system comprises the bus portion having those signal levels, an electronic logic portion in which two levels (1 and 0) are used, and an optical portion in which two levels (on and off) are used.
  • the electronic logic portion is the link between the bus and the fiber optic bus extender.
  • the second EOI unit 44 is shown connected to a bus monitor 52.
  • a box 54 represents the entire bus extender system, comprising the first EOI unit 28, the second EOI unit 44, and the two fiber optic cables (which may extend 500 to 1,000 meters).
  • Line 5c shows the end of a bi-polar electrical message, at which point the voltage level goes to zero, as shown by the right portion 86 of the line. This zero voltage is reached at time T 2 .
  • the EOI must accurately determine the time 'T2' in the reconstructed 1553 signal when the 1773 message ends at 'Tl 1 .
  • a further requirement is that •Tl' be distinguished from *T3' .
  • 'T3* is not the end of a message because a data sync follows the command word. Since the circuit must look ahead in time to determine whether a data word follows the end of the previous word, the transmitted 1553 message must be delayed by at least 1.5 microseconds.”
  • a timing problem exists because the encoding scheme of the bus assumes that no response is forthcoming after a predetermined time; and waiting for the time required to confirm that a message has ended can conflict with the encoding scheme.
  • Transceiver 90 has four input lines - 102, 104, 106 and 108 - which are output lines from a receiving unit 110.
  • Unit 110 has an input line 112 from fiber optic receiver 114.
  • the unit 96 which is replicated in the transmitter of the remote EOI, is an end-of-message pulse generator.
  • the unit 110 which is also replicated in the receiver of the remote EOI, is an end-of-message pulse detector.
  • the intercommunication, via the fiber optic lines, of units 96 and 110 is the means for conveying an end-of-message optical pulse, which substantially eliminates waiting time in the bus extender system, and thus eliminates the previously discussed performance problems of prior bus extender systems.
  • the end-of-message pulse is narrower than any pulse included in the bus protocol; so no confusion is possible.
  • the pulse entering pulse generator 122 causes the latter to generate a short end of message signal, e.g., a signal having a pulse width of 100 nanoseconds (ns) .
  • OR gate 166 will output a 1 value on line 168 as long as a given message is in progress on the bus extender. After passing through a delay device 170, the output signal of OR gate 166 reaches the input line 164 of one-shot 162.
  • OR gate 166 has one input 172 which is connected to the output 174 of an OR gate 176.
  • One input 178 of OR gate 176 is connected to logic line 150.
  • the other input 180 of OR gate 176 is connected to not-logic line 182, which carries the complement of the logic value. In other words, whenever the value at input 178 is high (1) , the value at input 180 is low (0) , and vice versa. This means that a 1 value will output from OR gate 176 on line 174 as long as message pulses are occurring.
  • a delay device 184 is connected between not-logic line 182 and input 186 of an OR gate 188.
  • another delay device 190 is connected between logic line 150 and input 192 of OR gate 188. This arrangement insures that the output signal from OR gate 188 on input line 194 of OR gate 166 will be slightly offset from the signal on its input line 172. Therefore, a 1 value will be maintained throughout the message transmission.
  • the usefulness of the overlap feature is due to the differences in rise and fall times of the message pulses, depending on the amplitude of the incoming signals.
  • Figure 10 is a time diagram illustrating the pulse timing at key points in the Figure 9 circuitry.
  • Line 10A shows pulses at the hardwire transceiver, prior to their conversion to two value (high/low) logic. Three values exist - plus voltage, zero voltage, and minus voltage. The first and last ends of the line are at zero voltage. The other portions change between positive and negative voltage.
  • Line 10D shows the pulse form at the output of OR gate 176. The value remains at 1, because one of the inputs is always at 1.
  • Line 10E shows the slightly delayed pulse form exiting delay device 184 on line 186.
  • Line 10F shows the slightly delayed pulse form exiting delay device 190 on line 192.
  • the pulse forms on lines 10E and 10F are mirror images of one another, because one receives the logic input, and the other receives the not-logic input.
  • Line 10G shows the pulse form at the output of OR gate 188. Like the output of OR gate 176, the value remains at 1, because of the logic and not-logic inputs.
  • the pulse form on line 10G is delayed slightly from the pulse form on line 10D.
  • Line 10H shows the logic output from OR gate 166. The line stays high throughout the message being transmitted. It goes low when both logic and not-logic go low, indicating that the message has ended.
  • Line 101 shows the output on line 164. Its profile essentially matches that of line 10H, except that 101 has been delayed slightly by the delay device 170.
  • FIG 11 shows the primary electronic components included in the end-of-message detector associated with the fiber optic receiver.
  • Receiving unit 110 ( Figures 6 and 8) receives an electronic logic signal on line 200. That signal has been converted from the optical signal received by fiber optic receiver 114 ( Figure 6) .
  • a message pulse from the fiber optic extender After passing through an inverter 202a, a message pulse from the fiber optic extender has a positive-going edge on line 204 and on line 206.
  • the normal message pulses pass through a series of inverters 202b, 202c, 202d, and 202e, and a delay device 208. Then they are output on line 210 to one input 212 of an AND gate 214.
  • the output line 216 of AND gate 214 leads to the hardwire transceiver unit.
  • AND gate 214 is enabled to transmit the normal message information as long as its second input 218 has a 1 value provided by an enable line 220.
  • the value on enable line 220 drops to 0 for a predetermined period in response to an end-of-message pulse on incoming line 200.
  • the circuitry in Figure 11 has three primary functions. First, it delays the normal message pulses sufficiently to permit detection of the end-of-message pulse.
  • the end-of-message pulse is preferably 100 nanoseconds (ns) wide.
  • the minimum pulse width during a normal message transmission is 500 nanoseconds (ns) .
  • Delay device 208 and inverters 202b, 202c, 202d, and 202e, provide sufficient delay to permit detection of a 100 ns pulse before the normal message pulse is transmitted through AND gate 214.
  • the second and third functions of the Figure 11 circuitry are detection of an end-of-message pulse, and removal of that pulse from the pulse train on line 216. Detection of the end-of-message pulse is primarily the function of a one-shot 222, which creates a "window" 300-400 nanoseconds wide. If no incoming pulse is completed within that period, the normal message passes through from line 200 to line 216, because the value on enable line 220 remains at 1.
  • a shorter incoming pulse end-of-message
  • the result is a change at a flip-flop 224, which in turn causes a change at a flip-flop 226.
  • the change at flip-flop 226 causes a change at a flip-flop 228, which changes the value on enable line 220 to 0, thereby blocking the message pulses on line 210 at AND gate 214.
  • the subsequent return to 1 of the value on enable line 220 is accomplished by a signal carried on line 230 from line 210 to clock input 232 of flip-flop 228.
  • Enable line 220 When a positive-going edge appears on line 230, it reaches input 232 of flip-flop 228, causing it to fire. This causes the Q value at 242 to go to 1. Enable line 220, therefore, has a 1 value, and thus permits message pulses on line 210 to pass through AND gate 214 to output line 216.
  • Delay device 208 is a 350 ns delay, and the series of inverters 202 causes a slight additional delay (e.g., 20 ns) . This permits a 100 ns end-of-message pulse to be detected.
  • the positive edge on line 206 causes the one-shot 222 to fire, i.e., a 1 value from Q output 246 is sent on line 248 to the clear input 250 of flip-flop 224.
  • the period during which this 1 output at Q is maintained is the 300-400 nanoseconds for which the one-shot 222 is designed. During this period, the clear constraint on flip-flop 224 is removed. It will fire if a positive edge is received at its clock input 260. Such an edge will occur if an end-of-message pulse enters on line 200. If a 100 nanosecond pulse arrives, its negative-going edge will be changed to a positive-going edge by inverter 202b.
  • a one-shot 264 is provided, which has its input 226 connected to enable line 220.
  • One-shot 264 fires when the enable goes from an on condition to an off condition. It allows for propagation delays, in order to prevent problems due to differences in transition speeds from high to low or vise versa.
  • Figures 12 and 13 are time diagrams of the old and new designs, respectively.
  • the old design is that used by the assignee of the present invention prior to discovering the need for a separate end-of-message signal.
  • line 12A shows pulses on the bus, before or after their conversion to high/low logic.
  • the total of 4 microseconds ( ⁇ s) indicates how quickly a remote terminal can respond to a bus controller command. If a 4 ⁇ s wait were incorporated, a new message would have begun with pulse 276, causing signal confusion and loss of synchronization.
  • Line 12B shows the optical pulses; and line 12C shows the voltage logic pulses from the optical receiver.
  • Lines 12D and 12E show, respectively, the logic outputs from two flip-flops in the system.
  • line 12F shows that the combination of high values on lines 12D and 12E causes a continuous high value, which blocks out the dead (zero voltage) portion 270 in line 12A.
  • the result is a failure to distinguish the end of one message and the start of a new message.
  • a timer was started and restarted on every edge of the incoming data. The duration of the timer was too long for those cases where a remote terminal would respond faster than the width of the timer. The EOI would not give up the bus connection soon enough.
  • Line 12G shows the receiving unit bus output, having high, low, and zero values.
  • the zero value (end-of-message) time shown by dashed line 278, has not been recognized by the communication system.
  • Figure 13 is a time diagram showing how the brief end-of-message pulse (Figures 6-11) solves the problem illustrated in Figure 12.
  • Line 13A represents the on/off optical transmitter output. The end of the present message occurs at 280; and the 100 ns pulse is generated at 282.
  • Line 13B shows the logic pattern at the input of the optical receiver. It has the same pulse pattern as line 13A.
  • Line 13C shows the enable pattern provided by the end-of-message detection electronics. The pulse flow is disabled during the low period 284.
  • Line 13D shows the stripped signal at the receiver, after the end-of-message pulse 282 has been removed.
  • Line 13E shows the three level signal values at the receiving transceiver.
  • the receiver is off the bus at dashed line 286, and has a zero voltage value for a period 288 before a new data message starts at 290.
  • the time required to determine that a data message has ended is too short to cause loss of synchronization.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Theoretical Computer Science (AREA)
  • Computing Systems (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Dc Digital Transmission (AREA)

Abstract

Système d'extension de fibre optique (Fig. 6) dans lequel des messages sont transférés par des lignes de fibre optique entre des unités électroniques éloignées. Les unités électroniques (par exemple, isolées du transformateur) ont trois niveaux de signaux: tension positive, tension négative, et tension zéro (Fig. 13). Puisque le système de fibre optique ne peut traiter convenablement que deux niveaux de signaux, les graves problèmes de communication potentiellement intermittents sont évités par la production et la transmission d'une impulsion de fin de message (282) lorsque l'unité électronique de transmission est au niveau de tension zéro. Cette impulsion de fin de message (282) est détectée au niveau de l'unité électronique éloignée, et la ligne est libérée pour le message suivant.
PCT/US1991/004183 1990-06-14 1991-06-12 Transmission par fibre optique de signaux electroniques a trois niveaux WO1991020138A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US53822490A 1990-06-14 1990-06-14
US538,224 1990-06-14

Publications (1)

Publication Number Publication Date
WO1991020138A1 true WO1991020138A1 (fr) 1991-12-26

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Family Applications (1)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998044635A1 (fr) * 1997-03-27 1998-10-08 Northern Telecom Limited Technique de codage duobinaire et de modulation pour systemes optiques de communication

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3693155A (en) * 1971-03-23 1972-09-19 Nat Telecommunications System Communication system
US3914537A (en) * 1972-05-16 1975-10-21 Xerox Corp Facsimile communication system
US4000371A (en) * 1974-03-16 1976-12-28 Ricoh Co., Ltd. Facsimile transmission method and system
US4850047A (en) * 1986-08-29 1989-07-18 Fujitsu Limited Optical bus communication system utilizing frame format signals
US4850046A (en) * 1986-10-30 1989-07-18 Neiman Infrared transmitter of coded message having fixed code and large number of combinations
US4882770A (en) * 1987-12-14 1989-11-21 H. M. Electronics, Inc. Wireless optical communication system

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3693155A (en) * 1971-03-23 1972-09-19 Nat Telecommunications System Communication system
US3914537A (en) * 1972-05-16 1975-10-21 Xerox Corp Facsimile communication system
US4000371A (en) * 1974-03-16 1976-12-28 Ricoh Co., Ltd. Facsimile transmission method and system
US4850047A (en) * 1986-08-29 1989-07-18 Fujitsu Limited Optical bus communication system utilizing frame format signals
US4850046A (en) * 1986-10-30 1989-07-18 Neiman Infrared transmitter of coded message having fixed code and large number of combinations
US4882770A (en) * 1987-12-14 1989-11-21 H. M. Electronics, Inc. Wireless optical communication system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998044635A1 (fr) * 1997-03-27 1998-10-08 Northern Telecom Limited Technique de codage duobinaire et de modulation pour systemes optiques de communication
US5892858A (en) * 1997-03-27 1999-04-06 Northern Telecom Limited Duobinary coding and modulation technique for optical communication systems
AU709464B2 (en) * 1997-03-27 1999-08-26 Ciena Luxembourg S.A.R.L. Duobinary coding and modulation technique for optical communication systems

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