WO1997027694A1 - Transmission numerique sur des liaisons optiques paralleles - Google Patents

Transmission numerique sur des liaisons optiques paralleles Download PDF

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Publication number
WO1997027694A1
WO1997027694A1 PCT/SE1997/000101 SE9700101W WO9727694A1 WO 1997027694 A1 WO1997027694 A1 WO 1997027694A1 SE 9700101 W SE9700101 W SE 9700101W WO 9727694 A1 WO9727694 A1 WO 9727694A1
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WO
WIPO (PCT)
Prior art keywords
parallel
lines
pulse
random number
bit sequence
Prior art date
Application number
PCT/SE1997/000101
Other languages
English (en)
Inventor
Gunnar Forsberg
Original Assignee
Telefonaktiebolaget Lm Ericsson (Publ)
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 Telefonaktiebolaget Lm Ericsson (Publ) filed Critical Telefonaktiebolaget Lm Ericsson (Publ)
Priority to AU15630/97A priority Critical patent/AU1563097A/en
Publication of WO1997027694A1 publication Critical patent/WO1997027694A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03828—Arrangements for spectral shaping; Arrangements for providing signals with specified spectral properties
    • H04L25/03866—Arrangements for spectral shaping; Arrangements for providing signals with specified spectral properties using scrambling

Definitions

  • the invention relates to digital transmission of information on parallel lines, in particular on parallel optical fibers in a parallel fiber optic, high speed transmission link.
  • Fiber ribbon or optical ribbon cable is presently used more and more widely for transmission of information.
  • Such a ribbon cable contains optical fibers extending in parallel to each other, the number of parallel fibers typically being 4, 6, 8 or 12.
  • Links made of ribbon cable are primarily intended for short distances but can of course also be used for longer transmission distances. For example they can be used internally for a rapid transmission between different circuit units in a telephone station instead of or as a complement to electrical signals transferred in the conventional way through back planes or by means of coaxial cables.
  • a parallel link that consists of a plurality of, such as 4, 6, 8 or 12
  • different separate parallel lines such as a number of parallel optical fibers
  • each received bit is a one or a zero, i.e. is above or below some predetermined signal level called the decision level or the decision threshold.
  • a fixed signal level is used such as in DC-coupled receivers.
  • the decision level will always be "floating" and automatically set somewhere in the middle between the smallest and largest values of the received signal.
  • this presupposes that the signal permanently contains samples of the two signal levels signifying "ones” and “zeroes” respectively in order that a decision circuit will be capable of determining the signal levels and thereby the very decision level, which decides the logical content of a received pulse.
  • the input signal can be coded or scrambled, before it is fed to a transmission link, e.g. in the shape of an optical fiber.
  • a transmission link e.g. in the shape of an optical fiber.
  • the signal is decoded or "descrambled" by means of a suitable circuit.
  • the European patent application EP-A2 0 232 043 relates to scrambling of data signals for transmission through a fiber optic transmission link by subjecting each data word to the logical operation EXCLUSIVE-OR with a respective word from a pseudo-random number generator 24, see Fig. 1.
  • Eight EXCLUSlNE-OR-gates are arranged.
  • a descrambler contains a pseudo-random number generator 34, which is similar to the generator 24, and eight EXCLUSIVE-OR-gates 36.
  • Fig. 2 shows a multiplexer of data words which arrive at 5 three ports A, B, C.
  • the scrambling is made according to the above for transmission through a fiber optic transmission link.
  • a demultiplexer according to Fig. 3 performs demultiplexing and descrambling.
  • U.S. patent US-A 5,355,415 discloses a parallel distributed scrambling system where the scrambling is made using different segments of a pseudo-random sequence.
  • U.S. patent US-A 4,304,962 scrambling methods, scrambling and descrambling are disclosed. i5 Randomisation and EXCLUSIVE-OR-gates are used.
  • the European patent application EP- A2 discloses a signal scrambling transmission system for single line transmission.
  • scrambling of digital signals transmitted on a parallel fiber optic link is used.
  • the signals are scrambled on the transmitting side and are descrambled on the receiving side.
  • On the transmitting side a single common circuit can make a random-like stream of ones and zeros.
  • Scrambling of the parallel channels is made by means of controllable inverters or 30 EXCLUSIVE-OR-gates.
  • the random bit sequence used in descrambling is identical to the random bit sequence used in the scrambling and then the output signals are identical to the input signals.
  • identical random number generators can be provided on the transmitting and receiving sides. They are built from digital circuits and generate identical
  • a random number generator on the transmitting side can be used and none on the receiving side and an extra channel for transmitting the random number sequence to the receiving side.
  • a random number generator of arbitrary type can be used such as a generator of genuine binary random numbers.
  • Such a generator can be constructed by connecting an analog noise generator through a band-pass filter to a comparator, the output of which is sampled with the clock frequency.
  • the output signal is a random number sequence which is thus transferred on an own channel also to the receiving side.
  • bit parallel transmission In the transmission according to the above on the parallel lines or fibers it is all the time 0 assumed that all channels are clocked with the same clock signal, i.e. so called bit parallel transmission is used.
  • - Fig. 1 is a block diagram of a system for transmitting information on four parallel lines
  • - Fig. 2 is a block diagram of another embodiment of a system for transmitting information on four parallel lines where one line is used for transmitting a code sequence
  • - Fig. 3 is a circuit diagram of a random number generator
  • FIG. 4 is a block diagram of a further embodiment of a system for transmitting information on four parallel lines.
  • Fig. 1 four parallel transmission lines are shown in the shape of optical fibers 1, which typically are joined to a fiber ribbon cable.
  • Information signals of common digital type in the shape of light pulse trains are fed to one end of each fiber 1 from transmitting elements 3 in a transmitting module 5.
  • the light signals in the fibers 1 are received by receiver elements 7 in a receiving module 9 and are there converted to electrical signals.
  • the signals transmitted in the fibers 1 arrive originally at four parallel electric data lines 11 and are then, before transmitting on the parallel lines, converted to suitable optical signals in the transmitting elements 3.
  • the time positions of the individual bits in each incoming electric signal are given by an electric clock signal that arrives on a line 13, so that thus all the electric data signals on the lines 11 are clocked with the same clock signal, i.e. a bit parallel transmission is performed on the incoming data lines 11.
  • receiving elements 7 made with AC-coupling i.e. having a discrimination level determined by the pulse signal itself, and in particular by the highest and lowest levels thereof, which signify the two binary digits zero and one, in the signals transmitted in the optical fibers 1 and thereby in the signals received in the electronic receiving portion of the receiving elements 7, all the time, i.e. during all long time periods, transitions must exist between the low and the high signal levels or generally between two different signal levels, and this applies to both the optical and electrical case but here the decisions is made on electrical signals. It is achieved by feeding the electrical data signals incoming on the lines 11 to the data input terminal of a scrambling circuit 15 each, one such circuit thus being arranged for each individual incoming line 11 and each optical fiber 1. To the clock input terminals of the scrambler-circuits 15 the clock signal is provided from the line 13. All scrambler circuits 15 can be identical to each other.
  • the signals modified in the scrambler circuits 15 which are suitable for AC-coupling in the discrimination circuits included in the receiving elements 7 on the receiving side are the modified again, after transmission on the parallel optical lines 11, to their original state, so that the original signals on the incoming data lines 11 are regenerated on the receiving side. It is achieved by providing the received signals after conversion to electrical signals to data input terminals of descrambler circuits 19, one of which being arranged for each optical fiber 1 and thus for each receiving element 7. To the clock input terminals of the descrambler circuits 19 a bit clock signal is provided which has been regenerated in a clock regenerating circuit 21 from one of the received signals that has been converted to electrical shape.
  • the scrambler and descrambler circuits 15 and 19 respectively can be the complementary type comprising self synchronization, so that a descrambler circuit 19 automatically, for example by sensing signal sequences that correspond to an incoming data signal having only zeros, changes automatically the phase or time position of the generated pseudo-random number sequences in order to make a correct decoding of the transferred signal.
  • Such scrambler and descrambler circuits are well-known within the art, see e.g. U.S. patents 4,304,962, 4, 109,856, 4,663,501, 4,669,118, 4,744,104, 4,760,598, 4,807,290, 4,864,617, 5,107,267, and the European patent application No. EP-A1 0 021 544.
  • Fig. 1 individual scrambler and descrambler circuits are used for each individual fiber in a parallel transmission link comprising several individual fiber parts. In the operation of such circuits a relatively large loss power is generated.
  • Fig. 2 a preferred alternative embodiment is shown comprising a common random number generator 23 for performing the "scrambling" of the individual signals.
  • the random number generator 23 provides a more or less random signal sequence in the rhythm of the bit clock on the line 13, which is thus connected to the random number generator 23 and controls the rate of the delivered random number sequence.
  • one 1' of the transmission lines 1 is used for transmitting the random number sequence, and then only three data signals incoming on the lines 11 can be transmitted on the optical link.
  • the signal from the random number generator 23 does not need to be modified since it is the signal type which is suitable for AC-coupling.
  • an EXCLUSIVE-OR-gate 25 and a D-type flip-flop 27 are arranged for each transmitting element 3 and fiber optic line 1 .
  • the electrical data signals arriving on the lines 11 are fed to one input terminal of one of the EXCLUSIVE-OR-gates 25, to the other input terminal of which the signal from the random number generator 23 is provided.
  • the pulses in the output signals of the EXCLUSIVE-OR gates can have a little different start and stop times and are therefore provided to the data input terminals of the D- type flip-flops 27, to the clock input terminals of which the bit clock on the line 33 is also provided. From the output terminals of the D-type flip-flops 27 then well synchronized pulses are obtained which are supplied to the transmitting elements 3.
  • this random number sequence signal is then obtained as an electrical pulse train.
  • This signal is provided as one of the input signals to EXCLUSIVE-OR-gates 29 on the receiving side, to the other input terminals of which the signals converted to electrical shape are provided which have been transmitted on the respective fiber lines 1, except to the EXCLUSIVE-OR- gate 29', that corresponds to that fiber 1' on which the random number sequence is transmitted.
  • a constant voltage is applied, e.g. 0 V, in the same way as on the transmitting side.
  • the random number sequence can in the embodiment illustrated in Fig. 2 be obtained from a pseudo-random number generator 23 of known type that comprises a shift register which is internally connected in a suitable manner, i.e. a row of flip-flops connected in a suitable way to each other.
  • a pseudo-random number generator 23 of known type that comprises a shift register which is internally connected in a suitable manner, i.e. a row of flip-flops connected in a suitable way to each other.
  • Such a random number generator provides a completely deterministic sequence which however has a long repetition time period the length of which depends on the number of connected flip-flops in the random number generator circuit.
  • the random number generator can advantageously be a genuine random number generator based on a noise generator.
  • a noise generator 35 provides a signal to a filter circuit 37 that filters away at least low frequencies but also advantageously can filter away too high frequencies.
  • This signal is given a suitable average level and is provided to one input terminal of a comparator 39, to the other input terminal of which a reference signal, e.g. the potential 0 V, is delivered.
  • the output signal of the comparator 39 is supplied to the data input terminal of a D-type flip-flop 41, to the clock input terminal of which a bit clock signal is provided.
  • On the output terminal for a suitable choice of frequencies of the filter circuit 37, provided that also the spectrum of the noise generator 35 is suitable, a sequence of binary units generated in a genuinely random way is obtained. Such a solution is electrically little energy consuming.
  • Fig. 4 another preferred embodiment is illustrated which uses only one scrambler circuit on the transmitting side and only one descrambler circuit on the receiving side and which is designed so that all the four parallel lines of the transmission link can transmit useful data.
  • the scrambler and descrambler circuits 15", 19" are of the self synchronizing type which for example is disclosed in U.S. patent US-A 4,304,962 mentioned above.
  • pseudo ⁇ random number generators 23' and 43' respectively are provided which have identical designs and therefore generate the same pseudo-random number sequence.
  • the pseudo-random number generator 23" in the scrambler circuit 15" on the transmitting side is as above clocked by a bit clock on a line 13.
  • the data stream on one of the incoming electrical lines for useful data, on the line 11" is thus provided to the scrambler circuit 15' and the EXCLUSIVE-OR-gate 25" arranged therein.
  • the random number sequence is provided from the pseudo-random number generator 23" on its other input terminal.
  • incoming data from the other electrical lines 11 are provided to individual EXCLUSIVE-OR-gates 25, to the other input terminals of which the random number sequence is delivered.
  • incoming data from the other electrical lines 11 are provided to individual EXCLUSIVE-OR-gates 25, to the other input terminals of which the random number sequence is delivered.
  • the output signals from the gates 25 are pulse shaped in the D-type flip-flops 27, which are clocked by the clock signal on the line 13, and they are then transmitted by transmitting elements 3 on the parallel transmission lines 1. It can be observed that the conversion made for the signal on all incoming electrical lines is identical, since it is only in a physical way that the random number generator 23" is connected to a particular EXCLUSIVE-OR-gate 25".
  • Transmitted data are as above received by receiving elements 9 in a receiving module 7 and are converted to electrical pulses.
  • the descrambler circuit 19 is connected, which comprises a clock regeneration circuit 31", in which a correct bit clock signal is produced.
  • the signal then controls a random number generator 43 constructed in the same way as the random number generator 23" on the transmitting side.
  • this random number generator will be self synchronizing and provides as its output signal a random number sequence which is identical to that generated by the random number generator 23" and which in addition has a correct position in relation to the incoming bit sequence.
  • This random number sequence generated independently is then provided, in the same way as in the embodiment according to Fig.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)
  • Dc Digital Transmission (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)

Abstract

Des données arrivent sur des lignes électriques parallèles (11) en même temps qu'un signal d'horloge associé aux bits de données transmis sur une autre ligne parallèle (13). Les données transmises sur les diverses lignes sont brouillées, ces données étant envoyées à une entrée de portes OU exclusif (25), une séquence de nombres aléatoires produite par un générateur (23) de nombres aléatoires étant envoyée à l'autre entrée. Les signaux générés et codés de la sorte sont mis en forme dans des bascules (27) d'où ils sont envoyés à des éléments d'émission (3) pour être émis sur des lignes parallèles (1), des fibres optiques individuelles, par exemple. Les informations transmises sur les lignes de transmission parallèles (1) arrivent aux éléments récepteurs (7) et sont décodés par des portes OU exclusif (29) à l'autre entrée où est envoyée la séquence de nombres aléatoires transmise sur une des liaisons de transmission (1). Les signaux par impulsions décodés sont uniformément mis en forme dans des bascules (33) pour l'autre entrée où un signal d'horloge régénéré est envoyé, lequel a été fourni par un circuit (25) d'extraction d'horloge. L'utilisation d'un tel procédé de brouillage-débrouillage dans la transmission permet d'utiliser des circuits à couplage CA dans les éléments récepteurs (7), ceci conférant un niveau de sécurité élevé à la transmission.
PCT/SE1997/000101 1996-01-24 1997-01-22 Transmission numerique sur des liaisons optiques paralleles WO1997027694A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU15630/97A AU1563097A (en) 1996-01-24 1997-01-22 Digital transmission on parallel optical links

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9600256A SE9600256L (sv) 1996-01-24 1996-01-24 Digital överföring på parallell optik länk
SE9600256-3 1996-01-24

Publications (1)

Publication Number Publication Date
WO1997027694A1 true WO1997027694A1 (fr) 1997-07-31

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PCT/SE1997/000101 WO1997027694A1 (fr) 1996-01-24 1997-01-22 Transmission numerique sur des liaisons optiques paralleles

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AU (1) AU1563097A (fr)
SE (1) SE9600256L (fr)
TW (1) TW393835B (fr)
WO (1) WO1997027694A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1701497A1 (fr) * 2005-03-10 2006-09-13 AGILENT TECHNOLOGIES, INC. (A Delaware Corporation) Procédé et système d'embrouillage et de désembrouillage de données

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4304962A (en) * 1965-08-25 1981-12-08 Bell Telephone Laboratories, Incorporated Data scrambler
US4531022A (en) * 1983-01-13 1985-07-23 International Standard Electric Corporation Device for generating binary digit pseudo-random sequences
EP0232043A2 (fr) * 1986-02-07 1987-08-12 Nortel Networks Corporation Embrouillage de signaux de données
EP0298609A2 (fr) * 1987-07-06 1989-01-11 Wegener Communications, Inc. Système de transmission à embrouillage du signal
US5355415A (en) * 1993-03-15 1994-10-11 Byeong Gi Lee Parallel distributed sample scrambling system
US5448640A (en) * 1993-03-18 1995-09-05 Electronics And Telecommunications Research Institute Parallel distributed sample descrambling circuit for cell-based asynchronous transfer mode physical layer

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4304962A (en) * 1965-08-25 1981-12-08 Bell Telephone Laboratories, Incorporated Data scrambler
US4531022A (en) * 1983-01-13 1985-07-23 International Standard Electric Corporation Device for generating binary digit pseudo-random sequences
EP0232043A2 (fr) * 1986-02-07 1987-08-12 Nortel Networks Corporation Embrouillage de signaux de données
EP0298609A2 (fr) * 1987-07-06 1989-01-11 Wegener Communications, Inc. Système de transmission à embrouillage du signal
US5355415A (en) * 1993-03-15 1994-10-11 Byeong Gi Lee Parallel distributed sample scrambling system
US5448640A (en) * 1993-03-18 1995-09-05 Electronics And Telecommunications Research Institute Parallel distributed sample descrambling circuit for cell-based asynchronous transfer mode physical layer

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1701497A1 (fr) * 2005-03-10 2006-09-13 AGILENT TECHNOLOGIES, INC. (A Delaware Corporation) Procédé et système d'embrouillage et de désembrouillage de données

Also Published As

Publication number Publication date
TW393835B (en) 2000-06-11
AU1563097A (en) 1997-08-20
SE9600256D0 (sv) 1996-01-24
SE9600256L (sv) 1997-07-25

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