CA1185022A - Multipoint fiber optics junction terminal - Google Patents
Multipoint fiber optics junction terminalInfo
- Publication number
- CA1185022A CA1185022A CA000379250A CA379250A CA1185022A CA 1185022 A CA1185022 A CA 1185022A CA 000379250 A CA000379250 A CA 000379250A CA 379250 A CA379250 A CA 379250A CA 1185022 A CA1185022 A CA 1185022A
- Authority
- CA
- Canada
- Prior art keywords
- junction terminal
- multiplexer
- demultiplexer
- improvement
- optical
- Prior art date
- Legal status (The legal status 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 status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R16/00—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for
- B60R16/02—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements
- B60R16/03—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for
- B60R16/0315—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for using multiplexing techniques
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R16/00—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for
- B60R16/02—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements
- B60R16/03—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for
- B60R16/0315—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for using multiplexing techniques
- B60R2016/0322—Temporary code for documents to be reclassified to G08C, H04L or H04Q
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Optical Communication System (AREA)
Abstract
Abstract Known aircraft intercom systems, in which audio signals are carried over wires, are prone to electrical noise interference problems. These problems are alleviated by the present invention in which the transceivers and receivers are interconnected with the control sets via fibre optic lines. Audio signals are applied to a multiplexer which drives an optical modulator. The output of the optical modulator feeds a fiber optic line. Conversely, optical signals are fed to an optical demodulator whose output feeds a demultiplexer. Audio outputs from the demultiplexers feed the receivers and transceivers and the control sets.
Description
S();22 This invention relates to aircraft intercommunication (intercom) systems.
Aircraft and avionics systems face a hostile electromagnetic environment which presents numerous sources of electrical noise. Such noise can be produced by external radiation, induction on transmission lines, coupling between antennas, coupling by difference in ground potential, cross talk, conduction among power supply lines and injection by transmitters and receivers.
~o Noise interference is especially serious at audio frequencies as modulation on the power supply line (400 Hz) will immediately be picked up by the audio lines and amplified by the intercom system, rendering monitoring of audio frequenc~es difficult. Interference with communications among operators (pilot~
navigator, flight engineers, etc.) is obviously a potential flight safety hazard.
This very important opera-tional problem compounds the normal problem of intercom system maintenance since it requires maintenance actions to respond to operators grievances. ~owever, in practice, it has been found that:
a) there is a large difference between the number of malfunctions recorded duxing flight operations and bench tests;
b) this difference is much more important for the intercom system than for any other avionics system; and c) the number of maintenance actions showing "no fault" found accounts for about 10% of the manhours expended.
,, .
8~
The above factors are indicative of the noise and intermit-tent electromagnetic interference problem a~fecting aircraft intercom sys-tems. It is clear that, bo~h from flight opera~ions and maintenance aspects, it would be of great benefit to resolve this problem.
In existing intercom systems, various corrective measures are resorted to to alleviate the problem of noise including shielding, grounding, conductors twisting, balancing and isolation transformers. All these techniques must, to achieve conclusive results, often be combined which makes for complexity, high cost and additional weight. As an indication of the magnitude of the problem, it might be noted that some aircraft installations have over a thousand feet of audio lines.
The number of wiring links required for the interconnection between the reeeivers and the transmitters to the control sets are repeated for eaeh system. Thus, if there are M receivers and transmitters and N control sets, there are MxN interconnecting links. One ean easily appreciate the disadvantages both in terms of weight and volume. Furthermore, the maintenance aspeet suffers from such ~aried and diverse eleetrical aircraft wiring.
A review of a typical aircra~t installation makes the potential drawbacks self evident. A VHF (Very High Frequency) communication system aircraft installation is typically as follows:
Following the VHF audio ~rom the navigator's intercom eontrol/monitor to the transciever, a shielded wire goes through a panel assembly diseonneet connector, a braeket assembly disconnect 5()22 connector -to a connector on a junction box (JB) to two terminal posts inside the JB, then to a connector on the JB which is wired to a connector on the JB through the JB out another connector to the control connector to a volume control, back out of the control through the same connector to the transceiver connector.
The path for the microphone audio "high" is equally complicated. It runs from the navigator intercom control box connector through shielded wire to the panel assembly disconnect to the bracket assembly disconnect to a connector on the JB to two terminal posts in the JB, then out of a connector on the JB
to a connector on the JB 7 out of the JB to a connector on the transceiver.
There are two main reasons for taking the receiver and microphone audio signals to the junction box. They are:
a) to distribute the signals to the other intercom ; control sets; and b) to terminate or "load'l these lines with a termination resistor.
All these wires, interconnectors and junction boxes are subject to noise sources.
The present invention provides a means of alleviating the above-described problem of electrical noise interference in an aircraft intercom system. Basically, in accordance with the present invention, the problem is avoided by replacing the existing aircraft audio lines wiring connections from the communication and navigation sets to the control sets of the intercom system by an interconnection system utilizing fiber optic lines~
Fiber-optic lines are virtually immune to radio-frequency 5(~
(R.F.) interference and are much lighter in weight than wires.
Thus, in accordance with a broad aspect of the invention, there is provided, in an aircraEt intercom system having a plurality of radio trans-ceivers, radio receivers and control sets, the improvement wherein audio sig-nals from the radio transceivers and radio receivers to the control sets, and audio signals from the control sets to the transceivers, are multiplexed for transmission, converted to optical signals for transmission via fiber optic lines, demodulated back to a~dio signals and then distributed via demultiplex-ing means.
The optical signals may, of course, be in the infrared portion of the spectrum and the term "light" used herein includes infrared as well as visible li~ht.
The invention will now be further described in conjunction with the accompanying drawings, in which:
Figure 1 is a simplified block diagram of the basic layout of a ; system according to tlle invention;
Figure 2 is a block diagram showing the functional arrangement of a junction terminal used in the system of Figure l;
Figure 3 is a partly block, partly schematic diagram of a multiplex/
demultiplex unit as used in the terminal shown in Figure 2;
Figure 4 is a schematic diagram of a synchronization unit as used in the terminal shown in Figure 2, and Figure 5 is a schematic diagram of a modulator/demodulator as used in the terminal shown in Figure 2~
Turning now to Figure 1, the basic system layout according to the invention is shown. The system is assumed to have L radio transmitters/recei~ers(transceivers) 10 and M-L radio receivers 12; i.e. the total number of radio receivers and radio transceivers is hl. ~11 the audio lines 13 from and to the 3SO~,~
radio transceivers 10 and from the radio receivers and all the audio lines 14 to and from the intercom control sets 15 (N in number) are multiplexed and demultiplexed through two audio junction terminals 18 and 19. If redundant audio junction terminals are desired for reliability purposes, they can be coupled via optical couplers 20 known in the art, e.g. "access" or "star" type couplers. Light may be distributed into different distribution links to a number of terminals. In Figure 1, light is shown conducted to four different junction terminals.
Audio signals from the M radio transceivsrs and radio receivers 10, 12 are fed into junction terminal 18 at connection means 21. The multi-plexer 23 sequentially samples the inputs at 21 and drives an optical modulator 25 which produces an optical output on fiber-optic line 27. The signals on riber-optic line 27 are received by the optical demodulator 30 in terminal 19 which produces an audio output which is distributed by demultiplexer 32 to its M x N output lines 33. These output lines 33 are connected as inputs to the N control sets 15. Any extra audio output lines can be connected to the monitor 26 as in any typical intercom.
~he monitor, which is conventional and not directly related to the invention, is an integral part of aircraft avionics intercom systems. It provides for the junction of audio signals when the number of inputs is too large to be 35(~2~
handled by the control sets. In Figure 1 the inputs to the monitor are any extra audio output lines from the junction terminal. Audio lines can be selected one-by-one from the monitor by the operator (pilot, navigator...). The selected audio is sent to the control set.
The control sets are connected via lines 38 to junction terminal lg where the lines are sequentially examined by a multiplexer 40 which feeds an optical modulator 42 whose output on fiber optic line 43 is received by optical demodulator 45 in terminal 18. The demodulator 45 feeds a demultiplexer 46 which provides LxN outputs for the transceivers 10. That is, each of the N control set has to be connected to each of the L transmitters (in the transceivers) so L.xN outputs are required from demultiplexer 4~.
Turning now to Figure 2, the layout of a junction terminal, e.g. terminal 18, is shown in more detail. Electrical inputs 13 to the multiplexer 23 are taken from electrical connector Jl(21). Similarly, the outputs 50 o-E the demultiplexer 46 are taken to the same electrical connector Jl(21), or a similar one (standard electrical connection). The output 51 of the multiplexer 23 is connected via electrical bus 52 to the input 54 of a preamp 55. The preamp 55 feeds an amplifier 57 via, if required, an AGC circuit 56. The amplifier 57 drives an optical modulator comprising, a light emitting diode (LED) 58 whose light output is coupled to an optical fiber (not shown) at optical connectox J3.
Optical signals are received at optical junction J2 and detected by an optical demodulator compri~ing a photodiode ., , ~ ~5~2~
60. After preamplification at 61, AGC at 62, if re~uired, and ampllfication at 63, the electrical signal passes via bus 52 and line 64 to the input of demultiplexer 46.
Demultiplexer 46 directs the signals from line 64 to the appropriate output line S0.
The multiplexer 23 and demultiplexer 46 are controlled by a clock 65, binary counters 66, 67 and sync. unit 68 (comprising phase locked loop 70, delay compensation circuit 71 and level detector 72) as will be discussed in more detail later.
Figure 3 is a more detailed diagram of the multiplex/
demultiplex unit. Power supply, ground and all audio inputs and outputs go through the connector Jl. Analog audio signals, typically from 2 to 7 volts and of 100 to 150 mW, are the inputs to channels Sl to S15 of the multiplexer 23. The switching ; from one channel to the next is controlled by a binary counter 66, which divides a reference pulse given by the crystal oscillator clock 65. The output 51 of the multiplexer 23 is sent to the optical modulator which will be later described in connection with Figure 5.
The input 6~ to the demultiplexer 46 is the demodulated optical signal received from the optical demodulator to also be discussed in connection with Figure 5. See also Figure 2.
Switching of the demul~iplexer 46 from one channel to the next is controlled by the binary counter 67, which divides a reference pulse received from the synchronisation unit, to be discussed in detail in connection with Figure 4. The required D.C. voltage for all units is obtained from voltage regulators VRl and VR2.
-S(~2~
The crystal clock is conventional and here comprises a 1 M~lz crystal CRl, resistors Rl-R4, capacitor Cl and amplifier Ul.
rne binary dividers 66 and 67 are of similar construction including four stages connected as shown.
Pin 9 of Illultiplexer 23 is used as the synchronization input from the master clock oscillator 65. This input is sent through the line and will be detected by the synchronizatlon unit of the next j~mction terminal.
The multiplexer and demultiplexer may be integrated circuits. Pins 10-11, D13J C14 and lNH15 are the same for multiplexer 23 and demultiplexer 4-6 and are used by the logic structure of the integrated circuits. Pin 12 is connected to ground.
Suitable multiplexers/demultiplexers may comprise COS/MOS type CD
4067 integrated circuits.
Line 80 from pin 11 of counter 67 provides pulses at 1/16 th the clock rate for use by the synchronization unit, Figure 4.
Referring to Figure 4, the synchronization unit receives pulses from the optical demodulator on line 64 for comparison with a reference voltage, on line 81, applied via resistor R5 to the non-inverting input of level detector 82, line 64 being connected to the inverting input. The delay equali~ation circuit ~C2, R9, R10, Ll, U2, Rll) makes compensation for phase propagation delays both over the transmission line and the întegrated circuits. It is followed by a comparator, U3 controlled by Rl2, which reestablishes, if required, the original shape of the clock pulse. Finally a phase locked ~ ~85~3~;~
loop circuit 83, comprising a phase detector 84, a filter 85 and a voltage controlled oscillator 86, whose characteristics are controlled by R13, R14, R15, R16, R17, C3 and C4, ensures final synchronisation of the signal.
Figure 5 illustrates a simple light emitting diode modulator and a photodiode detector demodulator used to optically process the multiplexed signals in between the junction terminals. The modulator and demodulator could also be of integrated circuit types. The multiplexed signal on l:ine 51 is fed via transformer Tl, capacitor C5 and variable resistor R18 to the base of transistor Ql. Transistor Ql drives the light emitting diode Vl, whose light output is coupled to the fiber optic link by optical coupler J3.
The photcdiode V12 of the demodulator receives light from optical coupler J2. The electrical output of V12, passing through capacitor C6, is amplified by amplifiers UlA and UlB (and associated resistors and capacitors) and then sent, through transformQr T2, to the demultiplexer unit.
As mentioned above, the multiplexers/demultiplexers may comprise COS/MOS type CD 4067 integrated circuits but of course other suitable circuits may be used if desired. A number of other components may also comprise integrated circuits and, without limiting the invention thereto in any way, th~ following examples have been found suitable:
Figure 3 Ul - LM149/LM349 67 - SN5493~
~' ~.~85~1~22 23, 2~ - CD4067 Figure 82 - L~741LN
U~ - MC140463AL
! Figure 5 Ul - MLM149 or LM349 The intercom system according to the invention has a number of advantages, including the following:
a) reduction of noise usually picked up by the audio transmission lines, relays and splices;
b) reduction of crosstalk;
c) reduction of the number of maintenance actions and noise problems;
d) reduction of wiring weight and volume; and e) system fle~ibility and adaptability.
The reduction of noise makes the intercom system according to the invention more "airworthy".
The system is relatively simple and very adaptable to various types of aircraft intercom systems. System modifications are not required as the multi-point fiber-optic junction terminals will interface with any analog audio signal.
The fiber-optics junction terminal is relatively simple and eliminates the need to have a large number of aircraft electrical terminals and junction boxes. The simple module/unit design allows adaptation to specific systems or aircraft requirements.
~ ~s~
Obviously, some modifications and variations in the system are possible in light of particular requ.irements. It is therefore to be understood that within the scope of the attached claims the invention may be practiced with some variations to the system specifically described.
Aircraft and avionics systems face a hostile electromagnetic environment which presents numerous sources of electrical noise. Such noise can be produced by external radiation, induction on transmission lines, coupling between antennas, coupling by difference in ground potential, cross talk, conduction among power supply lines and injection by transmitters and receivers.
~o Noise interference is especially serious at audio frequencies as modulation on the power supply line (400 Hz) will immediately be picked up by the audio lines and amplified by the intercom system, rendering monitoring of audio frequenc~es difficult. Interference with communications among operators (pilot~
navigator, flight engineers, etc.) is obviously a potential flight safety hazard.
This very important opera-tional problem compounds the normal problem of intercom system maintenance since it requires maintenance actions to respond to operators grievances. ~owever, in practice, it has been found that:
a) there is a large difference between the number of malfunctions recorded duxing flight operations and bench tests;
b) this difference is much more important for the intercom system than for any other avionics system; and c) the number of maintenance actions showing "no fault" found accounts for about 10% of the manhours expended.
,, .
8~
The above factors are indicative of the noise and intermit-tent electromagnetic interference problem a~fecting aircraft intercom sys-tems. It is clear that, bo~h from flight opera~ions and maintenance aspects, it would be of great benefit to resolve this problem.
In existing intercom systems, various corrective measures are resorted to to alleviate the problem of noise including shielding, grounding, conductors twisting, balancing and isolation transformers. All these techniques must, to achieve conclusive results, often be combined which makes for complexity, high cost and additional weight. As an indication of the magnitude of the problem, it might be noted that some aircraft installations have over a thousand feet of audio lines.
The number of wiring links required for the interconnection between the reeeivers and the transmitters to the control sets are repeated for eaeh system. Thus, if there are M receivers and transmitters and N control sets, there are MxN interconnecting links. One ean easily appreciate the disadvantages both in terms of weight and volume. Furthermore, the maintenance aspeet suffers from such ~aried and diverse eleetrical aircraft wiring.
A review of a typical aircra~t installation makes the potential drawbacks self evident. A VHF (Very High Frequency) communication system aircraft installation is typically as follows:
Following the VHF audio ~rom the navigator's intercom eontrol/monitor to the transciever, a shielded wire goes through a panel assembly diseonneet connector, a braeket assembly disconnect 5()22 connector -to a connector on a junction box (JB) to two terminal posts inside the JB, then to a connector on the JB which is wired to a connector on the JB through the JB out another connector to the control connector to a volume control, back out of the control through the same connector to the transceiver connector.
The path for the microphone audio "high" is equally complicated. It runs from the navigator intercom control box connector through shielded wire to the panel assembly disconnect to the bracket assembly disconnect to a connector on the JB to two terminal posts in the JB, then out of a connector on the JB
to a connector on the JB 7 out of the JB to a connector on the transceiver.
There are two main reasons for taking the receiver and microphone audio signals to the junction box. They are:
a) to distribute the signals to the other intercom ; control sets; and b) to terminate or "load'l these lines with a termination resistor.
All these wires, interconnectors and junction boxes are subject to noise sources.
The present invention provides a means of alleviating the above-described problem of electrical noise interference in an aircraft intercom system. Basically, in accordance with the present invention, the problem is avoided by replacing the existing aircraft audio lines wiring connections from the communication and navigation sets to the control sets of the intercom system by an interconnection system utilizing fiber optic lines~
Fiber-optic lines are virtually immune to radio-frequency 5(~
(R.F.) interference and are much lighter in weight than wires.
Thus, in accordance with a broad aspect of the invention, there is provided, in an aircraEt intercom system having a plurality of radio trans-ceivers, radio receivers and control sets, the improvement wherein audio sig-nals from the radio transceivers and radio receivers to the control sets, and audio signals from the control sets to the transceivers, are multiplexed for transmission, converted to optical signals for transmission via fiber optic lines, demodulated back to a~dio signals and then distributed via demultiplex-ing means.
The optical signals may, of course, be in the infrared portion of the spectrum and the term "light" used herein includes infrared as well as visible li~ht.
The invention will now be further described in conjunction with the accompanying drawings, in which:
Figure 1 is a simplified block diagram of the basic layout of a ; system according to tlle invention;
Figure 2 is a block diagram showing the functional arrangement of a junction terminal used in the system of Figure l;
Figure 3 is a partly block, partly schematic diagram of a multiplex/
demultiplex unit as used in the terminal shown in Figure 2;
Figure 4 is a schematic diagram of a synchronization unit as used in the terminal shown in Figure 2, and Figure 5 is a schematic diagram of a modulator/demodulator as used in the terminal shown in Figure 2~
Turning now to Figure 1, the basic system layout according to the invention is shown. The system is assumed to have L radio transmitters/recei~ers(transceivers) 10 and M-L radio receivers 12; i.e. the total number of radio receivers and radio transceivers is hl. ~11 the audio lines 13 from and to the 3SO~,~
radio transceivers 10 and from the radio receivers and all the audio lines 14 to and from the intercom control sets 15 (N in number) are multiplexed and demultiplexed through two audio junction terminals 18 and 19. If redundant audio junction terminals are desired for reliability purposes, they can be coupled via optical couplers 20 known in the art, e.g. "access" or "star" type couplers. Light may be distributed into different distribution links to a number of terminals. In Figure 1, light is shown conducted to four different junction terminals.
Audio signals from the M radio transceivsrs and radio receivers 10, 12 are fed into junction terminal 18 at connection means 21. The multi-plexer 23 sequentially samples the inputs at 21 and drives an optical modulator 25 which produces an optical output on fiber-optic line 27. The signals on riber-optic line 27 are received by the optical demodulator 30 in terminal 19 which produces an audio output which is distributed by demultiplexer 32 to its M x N output lines 33. These output lines 33 are connected as inputs to the N control sets 15. Any extra audio output lines can be connected to the monitor 26 as in any typical intercom.
~he monitor, which is conventional and not directly related to the invention, is an integral part of aircraft avionics intercom systems. It provides for the junction of audio signals when the number of inputs is too large to be 35(~2~
handled by the control sets. In Figure 1 the inputs to the monitor are any extra audio output lines from the junction terminal. Audio lines can be selected one-by-one from the monitor by the operator (pilot, navigator...). The selected audio is sent to the control set.
The control sets are connected via lines 38 to junction terminal lg where the lines are sequentially examined by a multiplexer 40 which feeds an optical modulator 42 whose output on fiber optic line 43 is received by optical demodulator 45 in terminal 18. The demodulator 45 feeds a demultiplexer 46 which provides LxN outputs for the transceivers 10. That is, each of the N control set has to be connected to each of the L transmitters (in the transceivers) so L.xN outputs are required from demultiplexer 4~.
Turning now to Figure 2, the layout of a junction terminal, e.g. terminal 18, is shown in more detail. Electrical inputs 13 to the multiplexer 23 are taken from electrical connector Jl(21). Similarly, the outputs 50 o-E the demultiplexer 46 are taken to the same electrical connector Jl(21), or a similar one (standard electrical connection). The output 51 of the multiplexer 23 is connected via electrical bus 52 to the input 54 of a preamp 55. The preamp 55 feeds an amplifier 57 via, if required, an AGC circuit 56. The amplifier 57 drives an optical modulator comprising, a light emitting diode (LED) 58 whose light output is coupled to an optical fiber (not shown) at optical connectox J3.
Optical signals are received at optical junction J2 and detected by an optical demodulator compri~ing a photodiode ., , ~ ~5~2~
60. After preamplification at 61, AGC at 62, if re~uired, and ampllfication at 63, the electrical signal passes via bus 52 and line 64 to the input of demultiplexer 46.
Demultiplexer 46 directs the signals from line 64 to the appropriate output line S0.
The multiplexer 23 and demultiplexer 46 are controlled by a clock 65, binary counters 66, 67 and sync. unit 68 (comprising phase locked loop 70, delay compensation circuit 71 and level detector 72) as will be discussed in more detail later.
Figure 3 is a more detailed diagram of the multiplex/
demultiplex unit. Power supply, ground and all audio inputs and outputs go through the connector Jl. Analog audio signals, typically from 2 to 7 volts and of 100 to 150 mW, are the inputs to channels Sl to S15 of the multiplexer 23. The switching ; from one channel to the next is controlled by a binary counter 66, which divides a reference pulse given by the crystal oscillator clock 65. The output 51 of the multiplexer 23 is sent to the optical modulator which will be later described in connection with Figure 5.
The input 6~ to the demultiplexer 46 is the demodulated optical signal received from the optical demodulator to also be discussed in connection with Figure 5. See also Figure 2.
Switching of the demul~iplexer 46 from one channel to the next is controlled by the binary counter 67, which divides a reference pulse received from the synchronisation unit, to be discussed in detail in connection with Figure 4. The required D.C. voltage for all units is obtained from voltage regulators VRl and VR2.
-S(~2~
The crystal clock is conventional and here comprises a 1 M~lz crystal CRl, resistors Rl-R4, capacitor Cl and amplifier Ul.
rne binary dividers 66 and 67 are of similar construction including four stages connected as shown.
Pin 9 of Illultiplexer 23 is used as the synchronization input from the master clock oscillator 65. This input is sent through the line and will be detected by the synchronizatlon unit of the next j~mction terminal.
The multiplexer and demultiplexer may be integrated circuits. Pins 10-11, D13J C14 and lNH15 are the same for multiplexer 23 and demultiplexer 4-6 and are used by the logic structure of the integrated circuits. Pin 12 is connected to ground.
Suitable multiplexers/demultiplexers may comprise COS/MOS type CD
4067 integrated circuits.
Line 80 from pin 11 of counter 67 provides pulses at 1/16 th the clock rate for use by the synchronization unit, Figure 4.
Referring to Figure 4, the synchronization unit receives pulses from the optical demodulator on line 64 for comparison with a reference voltage, on line 81, applied via resistor R5 to the non-inverting input of level detector 82, line 64 being connected to the inverting input. The delay equali~ation circuit ~C2, R9, R10, Ll, U2, Rll) makes compensation for phase propagation delays both over the transmission line and the întegrated circuits. It is followed by a comparator, U3 controlled by Rl2, which reestablishes, if required, the original shape of the clock pulse. Finally a phase locked ~ ~85~3~;~
loop circuit 83, comprising a phase detector 84, a filter 85 and a voltage controlled oscillator 86, whose characteristics are controlled by R13, R14, R15, R16, R17, C3 and C4, ensures final synchronisation of the signal.
Figure 5 illustrates a simple light emitting diode modulator and a photodiode detector demodulator used to optically process the multiplexed signals in between the junction terminals. The modulator and demodulator could also be of integrated circuit types. The multiplexed signal on l:ine 51 is fed via transformer Tl, capacitor C5 and variable resistor R18 to the base of transistor Ql. Transistor Ql drives the light emitting diode Vl, whose light output is coupled to the fiber optic link by optical coupler J3.
The photcdiode V12 of the demodulator receives light from optical coupler J2. The electrical output of V12, passing through capacitor C6, is amplified by amplifiers UlA and UlB (and associated resistors and capacitors) and then sent, through transformQr T2, to the demultiplexer unit.
As mentioned above, the multiplexers/demultiplexers may comprise COS/MOS type CD 4067 integrated circuits but of course other suitable circuits may be used if desired. A number of other components may also comprise integrated circuits and, without limiting the invention thereto in any way, th~ following examples have been found suitable:
Figure 3 Ul - LM149/LM349 67 - SN5493~
~' ~.~85~1~22 23, 2~ - CD4067 Figure 82 - L~741LN
U~ - MC140463AL
! Figure 5 Ul - MLM149 or LM349 The intercom system according to the invention has a number of advantages, including the following:
a) reduction of noise usually picked up by the audio transmission lines, relays and splices;
b) reduction of crosstalk;
c) reduction of the number of maintenance actions and noise problems;
d) reduction of wiring weight and volume; and e) system fle~ibility and adaptability.
The reduction of noise makes the intercom system according to the invention more "airworthy".
The system is relatively simple and very adaptable to various types of aircraft intercom systems. System modifications are not required as the multi-point fiber-optic junction terminals will interface with any analog audio signal.
The fiber-optics junction terminal is relatively simple and eliminates the need to have a large number of aircraft electrical terminals and junction boxes. The simple module/unit design allows adaptation to specific systems or aircraft requirements.
~ ~s~
Obviously, some modifications and variations in the system are possible in light of particular requ.irements. It is therefore to be understood that within the scope of the attached claims the invention may be practiced with some variations to the system specifically described.
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In an aircraft intercom system having a plurality of radio trans-ceivers, radio receivers and control sets, the improvement wherein audio sig-nals from the radio transceivers and radio receivers to the control sets, and audio signals from the control sets to the transceivers, are multiplexed for transmission, converted to optical signals for transmission via fiber optic lines, demodulated back to audio signals and then distributed via demulti-plexing means.
2. The improvement as claimed in claim 1 wherein there are L radio transceivers, and M-L radio receivers for a total of M radio transceivers and radio receivers and N control sets and wherein the M radio transceivers and receivers feed a first multiplexer in a first junction terminal, said first multiplexer feeding a first optical modulator whose output feeds a first fiber optic line, said first fiber optic line feeding a first optical demodulator in a second junction terminal, said demodulator feeding a first demultiplexer in said second junction terminal, said second junction terminals having MxN
audio outputs connected to said control sets.
audio outputs connected to said control sets.
3. The improvement as claimed in claim 2 wherein the control sets feed N inputs in said second junction terminals to a second multiplexer, said second multiplexer having an output feeding a second optical modulator whose output feeds a second fiber optic line, said second fiber optic line feeding a second optical demolulator in said first junction terminal, said second demodulator feeding a second demultiplexer in said first junction terminal, said first junction terminal having LxN audio outputs connected to said radio transceivers.
4. The improvement as claimed in claim 3 wherein said first multiplexer is controlled by a first binary counter which is controlled by a first crystal clock in said first junction terminal, and said second multiplexer is controlled by a second binary counter which is controlled by a second crystal clock in said second junction terminal.
5. The improvement as claimed in claim 4 wherein said first demulti-plexer in said second junction terminal is controlled by a third binary counter which is controlled by a first synchronization unit in said second junction terminal, and said second demultiplexer in said first junction terminal is controlled by a fourth binary counter which is controlled by a second synchro-nization unit in said first junction terminal.
6. The improvement as claimed in claim 5 wherein said first demultiplexer in said second junction terminal is synchronized with said first multiplexer in said first junction terminal when a clock synchronization pulse, from said first crystal clock in said first junction terminal, along with a multiplexed signal, reaches said first synchronization unit and said first demultiplexer in said second junction terminal.
7. The improvement as claimed in claim 6 wherein said second demultiplexer in said first junction terminal is synchronized with said second multiplexer in said second junction terminal when a clock synchronization pulse, from said crystal clock in said second junction terminal, along with a multiplexed signal, reaches said second synchronization unit and said second demultiplexer in said first junction terminal.
8. The improvement as claimed in claim 2, wherein said optical modulators comprise light emitting diodes.
9. The improvement as claimed in claim 8, wherein said optical demodulators comprise photodiodes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000379250A CA1185022A (en) | 1981-06-08 | 1981-06-08 | Multipoint fiber optics junction terminal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000379250A CA1185022A (en) | 1981-06-08 | 1981-06-08 | Multipoint fiber optics junction terminal |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1185022A true CA1185022A (en) | 1985-04-02 |
Family
ID=4120173
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000379250A Expired CA1185022A (en) | 1981-06-08 | 1981-06-08 | Multipoint fiber optics junction terminal |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1185022A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20130287400A1 (en) * | 2012-04-26 | 2013-10-31 | Miranda Technologies Partnership | Intercom transceiver with fiber optic link |
-
1981
- 1981-06-08 CA CA000379250A patent/CA1185022A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20130287400A1 (en) * | 2012-04-26 | 2013-10-31 | Miranda Technologies Partnership | Intercom transceiver with fiber optic link |
| WO2013163096A1 (en) * | 2012-04-26 | 2013-10-31 | Miranda Technologies Partnership | Intercom transceiver with fiber optic link |
| US9143233B2 (en) | 2012-04-26 | 2015-09-22 | Miranda Technologies Partnership | Intercom transceiver with fiber optic link |
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