FR2709839A1 - Switch for switching optical signals - Google Patents

Switch for switching optical signals Download PDF

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Publication number
FR2709839A1
FR2709839A1 FR9310800A FR9310800A FR2709839A1 FR 2709839 A1 FR2709839 A1 FR 2709839A1 FR 9310800 A FR9310800 A FR 9310800A FR 9310800 A FR9310800 A FR 9310800A FR 2709839 A1 FR2709839 A1 FR 2709839A1
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Prior art keywords
means
characterized
switch according
address
optical
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Granted
Application number
FR9310800A
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French (fr)
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FR2709839B1 (en
Inventor
Loualiche Slimane
Simon Jean-Claude
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Loualiche Slimane
Simon Jean Claude
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Priority to FR9310800A priority Critical patent/FR2709839B1/en
Publication of FR2709839A1 publication Critical patent/FR2709839A1/en
Application granted granted Critical
Publication of FR2709839B1 publication Critical patent/FR2709839B1/en
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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q11/00Selecting arrangements for multiplex systems
    • H04Q11/0001Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005Switch and router aspects
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q11/00Selecting arrangements for multiplex systems
    • H04Q11/0001Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005Switch and router aspects
    • H04Q2011/0007Construction
    • H04Q2011/0011Construction using wavelength conversion
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q11/00Selecting arrangements for multiplex systems
    • H04Q11/0001Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005Switch and router aspects
    • H04Q2011/0007Construction
    • H04Q2011/0013Construction using gating amplifiers
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q11/00Selecting arrangements for multiplex systems
    • H04Q11/0001Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005Switch and router aspects
    • H04Q2011/0007Construction
    • H04Q2011/0015Construction using splitting combining
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q11/00Selecting arrangements for multiplex systems
    • H04Q11/0001Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005Switch and router aspects
    • H04Q2011/0007Construction
    • H04Q2011/002Construction using optical delay lines or optical buffers or optical recirculation
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q11/00Selecting arrangements for multiplex systems
    • H04Q11/0001Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005Switch and router aspects
    • H04Q2011/0007Construction
    • H04Q2011/0022Construction using fibre gratings
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04QSELECTING
    • H04Q11/00Selecting arrangements for multiplex systems
    • H04Q11/0001Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005Switch and router aspects
    • H04Q2011/0037Operation
    • H04Q2011/0039Electrical control

Abstract

The present invention relates to a switch for switching optical signals which are in the form of optical packets consisting of a routing address and of a useful message, characterised in that it includes: splitting means (10) capable of splitting the optical signals, received at the input, into two beams (one beam containing at least the routing address and one beam containing at least the useful message) wavelength conversion means (20) capable of modifying the wavelength of the beam containing the useful message, depending on the split-off routing address, and wavelength-sensitive passive routing means (30) which receive the beam containing the useful message emanating from the conversion means (20). <IMAGE>

Description

 The present invention relates to the field of optical signal transmissions, and more specifically that of optical signal switching devices.

It is known that fiber optic telecommunications networks require different processing means at the level of network nodes, such as multiplexers, routers, cross-connects, switches
In the context of the present invention, the term "switch" means means capable of directing an optical input signal towards an output channel selectively chosen from several available output channels.

 These optical signal processing means, and in particular optical signal switches, will most certainly be essential components of future optical telecommunications networks.

All international operators as well as equipment manufacturers (ATT, Alcatel, Bellcore, BNR,
British Telecom, Deutsche Telekom, Ericsson, NTT ...) are therefore very actively studying optical communication.

 Various proposals have already been made to operate fast signal switching.

 First of all, electronic processing can be carried out using rapid switches, for example in Gallium Arsenide technology. This approach involves a mastered technology, but it breaks the optical continuity. The increase in frequency as well as the high number of lines to be treated can lead to an increasingly complex and difficult situation to resolve.

 We have also proposed (see Ref 1) a switching technique called SEED (Self Electro-optic Devices).

This technique has been adopted by ATT. However, it requires a particular technology and architecture of systems which is very long to master and very expensive. In addition, signal routing is done in electronics. The latest work involves realizations based on direct addressing by optical signals, but detection (PIN + FET + SEED) and control are always done in electronics.

Signal routing using optoelectronic devices (Niobate modulators, semiconductor optical amplifiers, electrooptical modulators with Stark effect, etc.) has been studied and continues to be studied by a number of laboratories (ATT, NTT, Ericsson, France
Telecom, ...). Technology is beginning to be mastered for 4x4 switching devices (4 inputs x 4 outputs), but increasing the number of lines seems difficult to achieve in integrated optoelectronic circuits. This argument goes through the use of hybrid technologies (Ref. 2).

 The present invention now aims to improve the known devices for switching optical signals.

 The object of the present invention is in particular to propose new means making it possible to auto-route optical signals organized in packets.

 These aims are achieved within the framework of the present invention thanks to a switch for optical signals, which are in the form of optical packets consisting of a routing address and a useful message, characterized in that it comprises - separating means capable of separating the optical signals received at the input, into two beams: a beam containing at least the switching address, and a beam containing at least the useful message, - length conversion means wavelengths capable of modifying the wavelength of the beam containing the useful message, as a function of the referral address, and - passive referral means sensitive to the wavelength, which receive the beam containing the useful message from conversion means.

 Other characteristics, objects and advantages of the present invention will appear on reading the detailed description which follows, and with reference to the appended drawings given by way of nonlimiting examples and in which - Figure 1 represents a schematic view of an optical switch according to the present invention, in a configuration with one input and four outputs, and - Figure 2 shows a schematic view of another optical switch according to the present invention in a configuration with four inputs and four outputs.

 As indicated previously and as illustrated in the appended figures, the optical switch according to the present invention essentially comprises separating means 10, conversion means 20 and passive switching means 30.

 The signals to be switched are in the form of optical packets consisting of a routing address and a useful message.

 The switch composed of means 10, 20 and 30 is adapted to direct an optical input signal to an output channel selectively chosen from several available output channels.

 More specifically, in the 1x4 configuration shown in FIG. 1, the switch is adapted to direct the optical signal coming from an input optical fiber 40 to an output channel selectively chosen from four available output channels placed opposite the means referral liabilities 30.

 On the other hand, in the context of the 4x4 configuration represented in FIG. 2, the switch is adapted to direct the optical input signals coming respectively from four optical input fibers 40, 41, 42, 43 towards an output channel selectively chosen among four available exit routes placed opposite the passive referral means 30.

 We will first of all endeavor to describe the embodiment in the 1x4 configuration represented in FIG. 1.

 The separating means 10 are designed to separate the optical signals received at the input, into two beams, a beam containing at least the switching address on the one hand, and a beam containing at least the useful message on the other hand. In practice, the two beams obtained at the output of the separating means 10 may be identical and each comprise the address of the switch and the useful message. The useful message can for example be used on the channel using the routing address, for phase synchronization in order to retrieve the routing address.

 If necessary, these separating means 10 can be designed to let the address signal pass with or without modification of the useful message.

 These separating means can be formed by any suitable means known to those skilled in the art. By way of nonlimiting example, the separating means 10 can be formed of a conventional fiber optic coupler.

 These separating means 10 further preferably comprise means 12 capable of electronically detecting the switching information and translating it into address form.

 These means 12 for detecting and processing the address may for example consist of a conventional optical detector (PIN) followed by an amplifier and a digital circuit for decoding the address and controlling the means for converting wavelength 20. This digital decoding and control circuit must be adapted in particular to the addressing code, to the number of bits of the address and to the telecommunications network.

 The output of the separating and processing means 10, 12 is applied to the wavelength conversion means 20.

 These wavelength conversion means can also be formed by any suitable means known to those skilled in the art.

 Preferably, in the context of the present invention, these conversion means 20 are formed by the combination of a semiconductor optical amplifier 22 and a set of lasers 24 controlled by the output of the processing means 12, and in number equal to the number of switch output channels.

 The useful message is applied to the input of the optical amplifier 22 via an optical fiber 45 placed between the output of the separating means 10 and said input of the amplifier 22. Furthermore, the outputs of the lasers 24 are connected via respective fibers 25 to an auxiliary input of the same optical amplifier 22 or coupled to the optical fiber 45, before the input of this optical amplifier 22.

 The function of the optical amplifier 22 is to transpose the information coming from the optical fiber 45 onto the output wavelength of the activated laser 24.

 Thus, according to the content of the address identified at the output of the means 10, which address determines the routing of the message, the processing means 12 cause the supply of one of the lasers 24 of defined wavelength a to which the message will be transferred. useful and which will serve to direct the useful message towards the associated output.

 The wavelength of the signal from the conversion means 22 consequently corresponds to the wavelength of the activated laser 24 and consequently varies according to the content of the address detected by the means 12.

The optical amplifier 22 can be formed from any structure known to a person skilled in the art, as for example described in the document Electronics Letters, 27
August 1992, vol. 28, n012, page 1714.

 The output 23 of the optical amplifier 22 is directed towards the passive switching means 30. These preferably consist of a diffraction grating. This diffraction grating 30 working as a demultiplexer, consequently directs the optical signal to one or the other of the different possible output channels, according to the value of the wavelength of the signal which it receives as input.

 As can be seen in FIG. 1, the optical fiber 45 which directs the useful message from the output of the separating means 10 to the optical amplifier 20 may comprise a delay element, formed for example of different turns, to take account of time for electronic processing of the address signal in the means 12. In FIG. 1, these turns defining a delay in the useful message are referenced 46.

 In the variant with a 4x4 configuration shown in FIG. 2, we find separator means 10, conversion means 20 and passive switching means 30 in accordance with those previously described with reference to FIG. 1.

 More specifically, in the 4x4 configuration shown in FIG. 2, respective separator means 10 are provided for each of the four input channels referenced 1, 2, 3, 4 and corresponding respectively to fibers 40, 41, 42, 43 and respective wavelength conversion means 20 in accordance with those previously described. On the other hand, as can be seen in FIG. 2, the passive referral means 30 are formed by a single diffraction grating common to the four input channels.

 Consequently, the outputs of the four optical amplifiers 22 constituting the wavelength conversion means are directed via optically conductive bars 23 to the common diffraction grating 30.

 Such a diffraction grating 30 can be formed from any conventional structure known to those skilled in the art.

 The switch shown in FIG. 2, for a 4x4 configuration therefore comprises four separator circuits 10, capable of separating and processing the address signals, four optical amplifiers 22 associated with sixteen lasers 24 emitting at four different wavelengths and one referral network 30.

 In the current state of technology available on the market, such a switch can operate up to around SGb / s.

 The structure of the switch according to the present invention can be extended to configurations nxp with n and p greater than 4, for example a configuration 32x32. It should be noted that the number of lasers 24 is equal to p.n.

 Of course the present invention is not limited to the particular embodiments shown in the appended figures and previously described but extends to any variant in accordance with its spirit.

 For example, in the case of the switch in accordance with the present invention, it is possible, depending on the properties which it is desired to obtain, to process the routing address or not.

 For this purpose, the address can be transferred without modification from the input to the output. Or alternatively, the separating and processing means 10, 12 can be equipped with means capable of modifying the form of the address, for example to prepare the work of a next switch. Such change means can be formed of means capable of modulating for example one of the lasers 24 or the optical amplifier 22.

 The switch according to the present invention offers many advantages over known prior structures.

 The switch according to the present invention uses components existing on the market.

 The useful message transmitted benefits from optical continuity.

 Another advantage of the switch according to the present invention compared to the known prior solutions lies in its flexibility of use which results from the separate processing of the address signal and the useful message. Indeed, the address can be at a given bit rate different from that of the useful message, for example a lower bit rate to simplify the electronic processing of the address signal.

 In addition, the benefit of optical continuity makes it possible to vary the bit rate of the useful message between a minimum and the maximum imposed by the wavelength conversion.

 Another advantage of the switch according to the present invention is linked to the fact that the signal crosses only one active circuit (the wavelength conversion means 22), the rest of the circuits being passive.

 In addition, the number of active nodes is reduced to n for a switch nxn while it is n2 in a switch with optical doors (see even reference 2). For the latter, electronic control is much more complex (need to reconfigure n2 nodes at each change of address).

 On the other hand, in the context of the invention, the laser corresponding to the decoded address must simply be supplied.

 It should also be noted that in the context of the invention, the switching point (converter 22) is static biased and does not require any electronic control.

 It is true that the switch according to the invention modifies the wavelength of the signal between the input and the output. However, this problem can be solved without difficulty, for example by the presence of a second switch.

 To avoid the creation of parasitic lines resulting from the mixing of waves, conventional bandpass optical filters can be provided at the output of each channel, each optical filter being calibrated on the respective wavelength of the channel considered.

REFERENCES 1.- F.B. McCormick, F.A.P. Tooley et Al, Applied Optics nO 31, p.5431, 1992.

2.- M. Gustavsson, B. Lagerstrom and Al, electronics letters nO 28, p.2223, 1992.

Claims (16)

 1. Switch for optical signals, which are in the form of optical packets consisting of a routing address and a useful message, characterized in that it comprises - separating means (10) capable of separating the optical signals received at the input, in two beams: a beam containing at least the switching address and a beam containing at least the useful message, - wavelength conversion means (20) capable of modifying the wavelength of the beam containing the useful message, as a function of the referral address, and - passive referral means (30) sensitive to the wavelength, which receive the beam containing the useful message from conversion means (20).
 2. Switch according to claim 1, characterized in that the passive switching means (30) are formed of a diffraction grating.
 3. Switch according to one of claims 1 or 2, characterized in that the means (20) for wavelength conversion are formed by the combination of an optical amplifier (22) and a set of lasers (24) equal in number to the number of output channels, which lasers (24) are controlled by the output of address decoder means (12) associated with the separator means (10).
 4. Switch according to claim 3, characterized in that the optical amplifier (22) is a semiconductor optical amplifier.
 5. Switch according to one of claims 1 to 4, characterized in that the separating means (10) are designed to transmit the address signal with the useful message.
 6. Switch according to one of claims 1 to 5, characterized in that the separating means (10) are formed of an optical fiber coupler.
 7. Switch according to one of claims 1 to 6, characterized in that the connecting means (45) between the output of the separating means (10) and the input of the wavelength conversion means (22) comprise a delay element formed for example of turns of an optical fiber.
 8. Switch according to one of claims 1 to 7, characterized in that it is configured in a 1x4 version.
 9. Switch according to one of claims 1 to 7, characterized in that it is configured in nxp version with n and p greater than or equal to 4.
 10. Switch according to one of claims 1 to 9, characterized in that each input channel comprises separating means (10) and wavelength conversion means (20), while the passive means d 'switch (30) are common to the various entry routes.
 11. Switch according to one of claims 1 to 10, characterized in that in an nxp configuration, it comprises n input channels each comprising separator means (10) and frequency conversion means (20) and it comprises passive switching means (30) common to the n entry channels, preferably formed by a diffraction grating (30) placed opposite p exit channels.
 12. Switch according to claim 11, characterized in that each of the conversion means (20) comprises p lasers (24).
 13. Switch according to one of claims 1 to 12, characterized in that it comprises means capable of changing the address when crossing the switch.
 14. Switch according to claim 13, characterized in that the address change means comprise modulation means, for example lasers.
 15. Switch according to one of claims 1 to 14 characterized in that it further comprises an optical bandpass filter set on a respective wavelength at the output of each channel.
 16. Switch according to one of claims 3 or 4 characterized in that the optical amplifier (22) is adapted to transpose on the output wavelength of an activated laser (24), the information of the beam containing the useful message.
FR9310800A 1993-09-10 1993-09-10 Optical signal switch. Expired - Fee Related FR2709839B1 (en)

Priority Applications (1)

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FR9310800A FR2709839B1 (en) 1993-09-10 1993-09-10 Optical signal switch.

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Application Number Priority Date Filing Date Title
FR9310800A FR2709839B1 (en) 1993-09-10 1993-09-10 Optical signal switch.

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997024899A1 (en) * 1995-12-29 1997-07-10 Telefonaktiebolaget Lm Ericsson (Publ) High-speed optical data switching system
EP0855587A2 (en) * 1997-01-27 1998-07-29 Sumitomo Electric Industries, Ltd. Wavelenght-variable light source and OTDR apparatus
EP1079571A2 (en) * 1999-08-25 2001-02-28 Nippon Telegraph and Telephone Corporation Optical packet routing network system based on optical label switching technique
EP1187508A3 (en) * 2000-09-06 2006-05-03 National Institute of Information and Communications Technology, Incorporated Administrative Agency Method, network and packet router for optical routing using multiple wavelength labels

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0223258A2 (en) * 1985-11-22 1987-05-27 Nec Corporation Wavelength division optical switching system having wavelength switching light modulators
EP0550046A2 (en) * 1991-12-31 1993-07-07 Gte Laboratories Incorporated Routing and switching of optical packets with multiplexed data and header

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0223258A2 (en) * 1985-11-22 1987-05-27 Nec Corporation Wavelength division optical switching system having wavelength switching light modulators
EP0550046A2 (en) * 1991-12-31 1993-07-07 Gte Laboratories Incorporated Routing and switching of optical packets with multiplexed data and header

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
IEEE COMMUNICATIONS MAGAZINE, vol.25, no.5, Mai 1987, PISCATAWAY, NJ US pages 27 - 32, XP3674 M. SAKAGUCHI ET AL 'Optical Switching Device Technologies' *
JOURNAL OF LIGHTWAVE TECHNOLOGY, vol.8, no.3, Mars 1990, NEW YORK US pages 416 - 422 M. FUJIWARA 'A Coherent Photonic Wavelength-Division Switching System for Broad-Band Networks' *
PHOTONICS II, PROCEEDINGS OF THE INTERNATIONAL TOPICAL MEETING, 12-14 AVRIL 1990, PAGES 296-299, KOBE JP, XP333175 S. KUROYANAGI ET AL 'Photonic ATM Switching Network' *
TECHNICAL DIGEST, OPTICAL FIBER COMMUNICATION CONFERENCE, 2-7 FEV. 1992, VOL. 5 PAGE 58, SAN JOSE US, XP341592 A. CISNEROS 'Large Scale ATM Switching and Optical Technology' *

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997024899A1 (en) * 1995-12-29 1997-07-10 Telefonaktiebolaget Lm Ericsson (Publ) High-speed optical data switching system
US5729548A (en) * 1995-12-29 1998-03-17 Telefonaktiebolaget Lm Ericsson (Publ.) High-speed optical data switching system
EP0855587A2 (en) * 1997-01-27 1998-07-29 Sumitomo Electric Industries, Ltd. Wavelenght-variable light source and OTDR apparatus
EP0855587A3 (en) * 1997-01-27 1999-07-21 Sumitomo Electric Industries, Ltd. Wavelenght-variable light source and OTDR apparatus
EP1079571A2 (en) * 1999-08-25 2001-02-28 Nippon Telegraph and Telephone Corporation Optical packet routing network system based on optical label switching technique
EP1079571A3 (en) * 1999-08-25 2004-03-24 Nippon Telegraph and Telephone Corporation Optical packet routing network system based on optical label switching technique
US6782210B1 (en) 1999-08-25 2004-08-24 Nippon Telegraph And Telephone Corporation Optical packet routing network system based on optical label switching technique
EP1499077A1 (en) * 1999-08-25 2005-01-19 Nippon Telegraph and Telephone Corporation Optical packet routing network system based on optical label switching technique
US7113701B2 (en) 1999-08-25 2006-09-26 Nippon Telegraph And Telephone Corporation Optical packet routing network system based on optical label switching technique
US7120358B2 (en) 1999-08-25 2006-10-10 Nippon Telegraph And Telephone Corporation Optical packet routing network system based on optical label switching technique
EP1187508A3 (en) * 2000-09-06 2006-05-03 National Institute of Information and Communications Technology, Incorporated Administrative Agency Method, network and packet router for optical routing using multiple wavelength labels
US7177543B2 (en) 2000-09-06 2007-02-13 National Institute Of Information And Communications Technology Method for routing optical packets using multiple wavelength labels, optical packet router using multiple wavelength labels, and optical packet network that uses multiple wavelength labels

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