WO2004107625A1 - Procede et systeme permettant d'identifier de canaux dans un reseau optique - Google Patents

Procede et systeme permettant d'identifier de canaux dans un reseau optique Download PDF

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Publication number
WO2004107625A1
WO2004107625A1 PCT/CA2003/001829 CA0301829W WO2004107625A1 WO 2004107625 A1 WO2004107625 A1 WO 2004107625A1 CA 0301829 W CA0301829 W CA 0301829W WO 2004107625 A1 WO2004107625 A1 WO 2004107625A1
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WIPO (PCT)
Prior art keywords
channel
tones
network
signature
tone
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Application number
PCT/CA2003/001829
Other languages
English (en)
Inventor
Paul David Obeda
Derrick Remedios
Ping Wai Wan
Colin Geoffrey Kelly
Original Assignee
Tropic Networks 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
Priority claimed from CA002430797A external-priority patent/CA2430797C/fr
Application filed by Tropic Networks Inc. filed Critical Tropic Networks Inc.
Priority to AU2003286051A priority Critical patent/AU2003286051A1/en
Publication of WO2004107625A1 publication Critical patent/WO2004107625A1/fr

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Classifications

    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0298—Wavelength-division multiplex systems with sub-carrier multiplexing [SCM]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2210/00—Indexing scheme relating to optical transmission systems
    • H04B2210/07—Monitoring an optical transmission system using a supervisory signal
    • H04B2210/075—Monitoring an optical transmission system using a supervisory signal using a pilot tone
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2210/00—Indexing scheme relating to optical transmission systems
    • H04B2210/07—Monitoring an optical transmission system using a supervisory signal
    • H04B2210/077—Monitoring an optical transmission system using a supervisory signal using a separate fibre

Definitions

  • the invention relates to optical networks, and, in particular, to the method and system for identification of channels in an optical network.
  • One of the common methods for the identification of a channel in an optical network is to modulate the channel with a low frequency tone, where the tone uniquely identifies the channel wavelength in the network.
  • a network management server (NMS) associated with network nodes is responsible for mapping each channel with a unique tone, and for keeping track of tones available for channel identification.
  • this method may not be suitable for large networks having a large number of optical channels and/or when additional information about the network components needs to be carried with the channel, or, e.g., when tone allocation is -accompanied by certain restrictions.
  • a method for identifying an optical channel in an optical network comprising the steps of marking the channel with a unique combination of two or more identification tags, the combination of identification tags being referred to as a channel signature, to identify the channel in the network, and detecting the channel signature at various locations in the network.
  • the identification tags are encoded onto the channel, and the identification tags are low frequency dither tones .
  • the step of modulating with the tones beneficially comprises one of the following types of modulation: amplitude modulation, frequency modulation, phase modulation, and polarization modulation.
  • the tones are modulated onto the channel either simultaneously or consecutively, ⁇ or the tones are modulated onto the channel using combinations of simultaneous and consecutive modulation.
  • the step of modulating the tones onto the channel consecutively may comprise modulating the tones in a predetermined order so as to form a repeating consecutive sequence of tones, the repeating consecutive sequence of tones being the channel signature.
  • the step of ⁇ consecutively modulating the tones so as to form the repeating consecutive sequence of tones may comprise modulating the tones so as to form the repeating consecutive sequence of tones, in which each tone is being used only once.
  • the step of modulating the tones onto the channel consecutively may comprise modulating two tones "L" times in total so as to form a repeating digital bit sequence pattern of length "L", wherein one of the tones represents a logical "0" value, and the other tone respresents a logical "1" value, the repeating digital bit sequence pattern forming the channel signature or a part thereof.
  • the step of modulating the channel with four tones comprises selecting the four tones so that channel signatures for different channels in the network are chosen so that, for channels destined to the same decoder in the network, a list of individual tones used in the channel signatures of said channels includes each tone only once.
  • the step of modulating comprises modulating the two pairs of tones onto the channel alternatively so that at any time only one of the two tone pairs is present.
  • the step of modulating the tones onto the channel consecutively may comprise modulating two tones pairs "L” times in total so as to form a repeating digital bit sequence • pattern of tone pairs of length "L", wherein one of the tone pairs represents a logical "0" value, and the other tone pair respresents a logical "1" value, the repeating digital bit sequence pattern of tone pairs forming the channel signature or a part thereof .
  • the method further comprises the step of verifying one or more restrictions imposed on the allocation of tones for the channel signature in the network, the step of verifying being performed before the step of marking.
  • the verification step beneficially comprises verifying that the tones in the channel signature are selected so that the frequency difference between any two tones in the channel signature is not less than a predetermined frequency spacing. Due to restrictions imposed by the current technology used by decoders in used today, this predetermined frequency spacing is from, but not restricted to, a range of frequency- spacings from about 1 Hz to about 100 Hz, preferably from about 8 Hz to about 10 Hz, but any frequency spacing may be used such that the tones may be reliably decoded.
  • the step of verifying the restrictions comprises verifying ⁇ that channel signatures for different channels in the network are chosen so that, for any number of channels destined to the same decoder in the network where the tones are detected, a list of individual tones used in the channel ⁇ signatures of said channels includes each tone only once.
  • the method further comprises the steps of maintaining a list of all tones to be used or channel signatures in the network, releasing tones in unique combinations for use as channel signatures in the network, and keeping track of tones available for further allocation to channel signatures in the network.
  • a system for identifying an optical channel in an optical network comprising means for marking the channel with a unique combination of two or more identification tags, the combination of identification tags being referred to as a channel signature, to identify the channel in the network, and means for detecting the channel signature at various locations in the network.
  • the means for marking the channel usefully comprises an encoder for encoding two or more low frequency dither tones onto the optical channel, and the means for detecting comprises a decoder for decoding said low frequency dither tones from the optical channel.
  • the encoder includes means for modulating the tones onto the channel either simultaneously or consecutively, or modulating the tones onto the channel using
  • the system further comprises means for verifying one or more restrictions imposed on the allocation of tones for the channel signature in the network.
  • the means for verifying advantageously comprises one or more of the following: " means for verifying that the tones in the channel signature are selected so that the frequency difference between any two tones in the channel signature is not less than a predetermined frequency spacing, and means for verifying that channel signatures for different channels in the network are chosen so that, for any number of channels destined to the same decoder in the network where the tones are detected, a list of individual tones used in the channel signatures of said channels includes each tone only once.
  • the system further comprises means for maintaining a list of all tones to be used for channel signatures in the network, means for releasing tones in unique combinations for use as channel signatures in the network, and means for keeping track of tones available for further allocation to channel signatures in the network.
  • the step of marking comprises modulating the channel with the identification tags, which are low frequency dither tones.
  • the step of marking the channel comprises allocating one of the tones, or, alternatively, two or more of the tones, in the channel signature for identifying the channel,, and allocating one or more of the remaining tones in the channel signature for identifying one or more parameters in the network associated with the channel .
  • the step of allocating the remaining tones in the method gainfully comprises allocating the tones for identifying one or more of the following network parameters associated with the channel: an optical band including the channel , a source node in the network where the channel signature is marked, a destination node in the network where the channel signature is detected, an optical fiber carrying the channel, and an optical cable including the optical fiber carrying the channel.
  • the step of modulating with the tones beneficially comprises one of the following types of modulation: amplitude modulation, frequency modulation, phase modulation, and polarization modulation. Conveniently, the tones are modulated onto the channel either simultaneously or consecutively, or the tones are modulated onto the channel using combinations of simultaneous and consecutive modulation.
  • the method further comprises the step of verifying one or more restrictions imposed on the allocation of tones for the channel signature in the network, the step of verifying being performed before the step of marking.
  • the verification step beneficially comprises verifying that the tones in the channel signature are selected so that the frequency difference between any two tones in the channel signature is not less than a predetermined frequency spacing. Due to restrictions imposed by the current technology used by decoders in used today, this predetermined frequency spacing is from, but not restricted to, a range of frequency spacings from about 1 Hz to about 100 Hz, preferably from about 8 Hz to about 10 Hz, but any frequency spacing may be used such that the tones may be reliably decoded.
  • the step of verifying the restrictions comprises verifying that channel signatures -for different channels in the network are chosen so that, for any number of channels destined to the same decoder in the network where the tones are detected, a list of individual tones, used in the channel signatures of said channels includes each tone only once .
  • the method further comprises the steps of maintaining a list of all tones to be used for channel signatures in the network, releasing tones in unique combinations for use as channel signatures in the network, and keeping track of tones available for further allocation to channel signatures in the network.
  • the channel signature comprises a pair of two dither tones, and one of the tones in the pair is allocated to identify the channel wavelength, and the other tone in the pair is allocated to identify one of the following network parameters: an optical band including. the channel, a source node in the network where the channel signature is marked, a destination node in the network where the channel signature is detected, and an optical fiber carrying the channel.
  • the method further comprises the beneficial step of selecting a plurality of unique pairs of tones, each tone in each pair being selected from a tonespace comprising a limited number of tones, and each pair of tones uniquely identifying the channel and the associated parameter in the network.
  • the step of selecting comprises the steps of: partitioning the tonespace into M blocks, each block comprising N tones, and selecting the two tones in the pair from the same block, the tones in the block being used to uniquely identify one channel and the associated parameter in the network.
  • the step of selecting comprises the steps of: partitioning the tonespace into a first segment and a second segment, and partitioning each segment into M blocks, and selecting one tone in the pair from a block from the first segment, and the other tone in the pair from a block from the second segment .
  • a system for identifying an optical channel in an optical network, comprising means for marking the channel with a unique combination of two or more identification tags, the combination of identification tags being referred to as a channel signature, to uniquely identify the channel in the network and one or more network parameters associated with the channel, and means for detecting the channel signature at various locations in the network.
  • the means for marking the channel usefully comprises means for modulating the channel with the identification tags, which are low frequency dither tones.
  • the means marking the channel comprises means for allocating one of the tones in the channel signature for identifying the channel, and means for allocating one or more of the remaining tones in the channel signature for identifying one or more parameters in the network associated with the channel.
  • the means for allocating beneficially comprises means for allocating the tones for identifying one or more of the following network parameters associated with the channel: an optical band including the channel, a source node in the network where the channel- signature is marked, a destination node in the network where the channel signature is detected, an optical fiber carrying the channel, and an optical cable including the optical fiber carrying the channel .
  • the means for modulating with the tones comprises means for modulating with one of the following types of modulation: means for amplitude modulation, means for frequency modulation, means for phase modulation, and means for polarization modulation.
  • the encoder usefully includes means for modulating the tones onto the channel either simultaneously or consecutively, or modulating the tones onto the channel using combinations of simultaneous and consecutive modulation.
  • the system further comprises means for verifying one or more restrictions imposed on the allocation of tones for the channel signature in the network.
  • the means for verification beneficially comprises means for verifying that the tones in the channel signature are selected so that the frequency difference between any two tones in the channel signature is not less than a predetermined frequency spacing. Due to restrictions ' imposed by the current technology used by decoders in used today, this predetermined frequency spacing is from, but not restricted to, a range of frequency spacings from about 1 Hz to about 100 Hz, preferably from about 8 Hz to about 10 Hz, although it is understood that any frequency spacing may be used such that the tones may be reliably decoded.
  • the means for verifying the restrictions comprises means for verifying that channel signatures for different channels in the network are chosen so that, for any number of channels destined to the same decoder in the network where the tones are detected, a list of individual tones used in the channel signatures of said channels includes each tone only once .
  • system further comprises means for maintaining a list of all tones to be used for channel signatures in the network, means for releasing tones in unique combinations for use as channel signatures in the network, and means for keeping track of tones available for further allocation to channel signatures in the network.
  • the means for marking comprises means for marking the channel with the channel signature comprising a pair of two dither tones, and usefully includes means for allocating one of the tones in the pair to identify the channel wavelength, and means for allocating the other tone in the pair to identify one of the following network parameters: an optical band including the channel, a source node in the network where the channel signature is marked, a destination node in the network where the channel signature is detected, and an optical fiber carrying the channel.
  • the system further comprises means for selecting a plurality of unique pairs of tones, each tone in each pair being selected from a tonespace comprising a limited number of tones, and each pair of tones uniquely identifying the channel and the associated parameter in the network.
  • the means for selecting usefully comprises means for partitioning the tonespace into M blocks, each block comprising N tones, and means for selecting the two tones in the pair from the same block, the -tones in the block being used to uniquely identify one channel and the associated parameter in the network.
  • the means for selecting comprises means for partitioning the tonespace into a first and second segments, means for partitioning each segment into M blocks, and means for selecting one tone in the pair from a block from the first segment, and the other tone in the pair from a block from the second segment.
  • FIG. 1 shows, an optical communications network for illustrating methods for identification of optical channels in an optical network according to embodiments of the invention
  • Fig. 2 is an illustration of one form of an encoder for modulating tones onto an optical channel within a node of the network of Figure 1;
  • Fig. 3 illustrates one form of a decoder for decoding tones from an optical channel within a node of the network of Figure 1;
  • Fig. 4a illustrates a tonespace used in the embodiments of the invention and correspondence between tone frequencies and tone numbers within the tonespace;
  • Fig. 4b illustrates partitioning of tones in the tonespace used in a method for identification of channels according to a first embodiment of the invention;
  • Fig. 4c illustrates partitioning of tones in the tonespace used in a method for identification of channels according to a second embodiment of the invention
  • FIG. 5 illustrates partitioning of tones in the tonespace used in a method for identification of channels according to a third embodiment of the invention
  • Figures 6a, 6b and 6c illustrate partitioning of tones in the tonespace used in a method for identification of channels, according to a fourth embodiment of the invention.
  • Fig. 7 is a table showing allocation of tones in the tonespace in the method of Figure 6.
  • FIG. 1 A simple network configuration for illustrating methods for identification of an optical channel (optical wavelength) in an optical network according to the embodiments of the invention is shown in Fig. 1.
  • An optical channel is marked with a unique combination of two or more low frequency signals, hereinafter called tones or dither tones, which are selected from a set of tones available for channel identification.
  • the tones are of a low frequency, for example in a range from about 1 kHz to about 100 kHz.
  • the set of tones released in a network and available for channel identification is called the tonespace.
  • the unique combination of two or more tones chosen from the tonespace will be referred to as ' channel signature. Since the number of combinations of two or more tones in the tonespace is far greater than the number of single tones in the tonespace-, a relatively large number of unique channel signatures may be selected for the identification of channels in the network. '
  • a simple optical communications network 10 comprising a plurality of, in this example two, nodes 12, identified individually as Node 1 and Node 2, which are coupled together via an optical communications path 14, e.g., an optical fiber, carrying a plurality of optical channels.
  • Each of the nodes 12 comprises a form of decoder 24 having input 11 and output 13 for decoding low frequency tones from the optical channels, and an encoder 26 having input 15 and output 17 for encoding low frequency tones onto the optical channels.
  • the network 10 also includes a network management system (NMS) 16, to which all of the decoders 24 and encoders 26 on the nodes 12 are coupled via communications paths 20, 22 represented by dashed lines.
  • NMS network management system
  • the NMS 16 has a memory 18 for storing the allocation of tones in the network, and a processing unit 19 which is responsible for assigning unique combinations of tones and keeping track of tones available for further allocation to channel signatures in the network.
  • the communications paths 20, 22 can be optical or other types (e.g. electrical) of communications paths .
  • Identification of a channel is performed as follows.
  • the decoder 24 decodes one or more tones modulated onto the channel carried by the communications path 14, and communicates the tones to the NMS 16 via communications path 20.
  • the NMS 16 looks up the unique combination of tones, which represents the channel signature, in a table in the memory 18 and thus maps the combination of tones onto the channel .
  • the NMS 16 looks up the channel in a table in the memory 18, maps the channel into the unique combination of tones, and sends the tones to the encoder 26 via communications path 22, where the tones are encoded onto the optical channel carried by the optical communications path 14.
  • such a communications network may include an arbitrary number of nodes 12 and NMSs 16, which may be located together or separately from one another, with various arrangements of communications paths 14 between the nodes 12, and NMSs 16 having 'the desired configuration or topology. Furthermore, such a communications network may be coupled to other similar or different communications networks in various manners. Accordingly, Fig. 1 serves to illustrate a simple form of a network for the purposes of describing embodiments of the invention.
  • Fig. 2 illustrates one form of encoder 26 which can ⁇ be used within nodes 12.
  • an optical channel to be provided with a unique channel signature is supplied to the encoder 26 via an optical path 14 at the input 15 of the encoder 26, an electronic variable optical attenuator (EVOA) 28, and an optical tap 30 to an output optical path 14 at the output 17 of the encoder.
  • EVOA electronic variable optical attenuator
  • a small portion, e.g. 4%, of the optical channel which is tapped by the optical tap 30, is detected by an optical detector 32, whose electrical output is amplified and filtered by an Automatic Gain Control (AGC) amplifier and filter unit 34, an output of which is supplied to a digital signal processor (DSP) unit 36.
  • AGC Automatic Gain Control
  • DSP digital signal processor
  • the DSP unit 36 provides a controlled voltage bias to the EVOA 28 in accordance with a respective tone for the optical channel, with which the DSP unit 36 is supplied for example from the NMS 16 via the communications path 22.
  • the encoder of Fig. 2 can modulate the optical channel with a desired amplitude modulation depth, for example of about 1% to about 4%, at frequencies up to about 1 MHz, to provide the desired form of modulation on the optical signal.
  • Fig. 3 illustrates one form of the decoder 24 which can be used within nodes 12.
  • an optical channel on an optical path 14 is supplied at the input 11 of the decoder 24 and to an optical tap 38 to an output optical path 14 at the output 13 of the decoder 24.
  • a small portion, e.g. 4%, of the optical channel which is tapped by the optical tap 38 is detected by an optical detector 40, whose electrical output is amplified and filtered by an AGC amplifier and filter unit 42, an output of which is supplied to a DSP unit 44.
  • the DSP unit 44 derives the tones that are present in the optical channel and provides these as an output to the NMS 16 via a communications path 20.
  • the NMS 16 maps the unique combination of tones into a channel .
  • DSP units 36 and 44 The forms and functions of the DSP units 36 and 44 • depend on the particular form of tones used.
  • the DSP unit 36 may incorporate a digital synthesizer and the DSP ' unit 44 may incorporate a Fast Fourier Transform (FFT) or
  • FFT Fast Fourier Transform
  • DFT Discrete Fourier Transform
  • the tonespace will comprise 1600 tones available for use in channel signatures. However, it is understood that this value is chosen for illustrative purposes only, and any suitable number of tones in the tonespace may be used as required.
  • One or more restrictions may be imposed on the choice of tones used to generate a channel signature for . identifying a channel in the network.
  • the NMS performs the necessary step of verifying the restrictions imposed on the choice of tones before the channel is marked with the channel signature.
  • the set of 1600 tones 46 in the tonespace of the embodiments of the invention is in the range between 48 kHz and 64 kHz, with a predetermined frequency spacing of 10 Hz between the tones.
  • the frequency of any tone in the tonespace will be (48000 + ( tonenumber*10) ) Hz, where "tonenumber" represents the ordinal number of the tone, for example, the first tone, second tone, and so on, in the tonespace, as illustrated in Fig 4a.
  • Fig. 4b illustrates partitioning of tones in the tonespace used in the method of identification of channels according to the first embodiment of the invention.
  • 49th tones are indicated by a dotted line and labelled 71, and the last (50th) tone in the second block is labelled 72.
  • Blocks 3 to block 31 are indicated by a dotted line and labelled 52.
  • the tones in the first block 48 are used to generate a channel signature for channel 1
  • the tones in the second block 50 are used to generate a channel signature for channel 2, and so on.
  • the frequencies of tones in each block are chosen as follows.
  • the first tone 56 is the first tone in the tonespace 46, or tone #1, and is equivalent to a frequency of 48000 Hz.
  • the second tone 58 in the first block is tone #33, which is 32 tones higher than the first tone 56
  • the third tone 60 is tone #65, which is 32*2 tones higher than the first tone, and so on
  • the last tone 64 in the first block is tone #1569, which is (32*49) tones higher than the first tone 56.
  • the first tone 66 is the second tone in the tonespace 46, or tone #2
  • the second tone 68 is 32 tones higher than the first tone 66 or tone #34, and so on
  • the first three tones used for identification of channel 1 are tones #1, #33, #65, and the first three tones used for identifying channel 32 are tones #32, #64 and #96.
  • a list of all tones to be used for channel signatures in the network is maintained by the NMS.
  • the NMS also performs the necessary steps of releasing tones in unique combinations for use as channel signatures, and keeping track of tones available for further allocation to channel signatures in the network.
  • a channel signature is chosen by the NMS by selecting a pair of tones from the block that corresponds to the channel .
  • the number of pairs available for. each channel is calculated by the combinatoric function (50 CHOOSE 2) or C 5 2 0 , which is equivalent to (50 ! / (50-2) !2 ! ) , or
  • Table 2 illustrates examples of tone pairs that uniquely identify channels 1 to 3 and channel 32 in the network, the tones in the tone pair being selected from the summary lists for corresponding channels from Table 1.
  • the tones pairs (1,33) and (1,65) may be used to uniquely identify two instances of channel 1 passing through, e.g., two different optical fiber links in the network.
  • channel signatures for identification of optical channels in the network
  • the combinations of tones in the pairs used for iridentifying the same channel are chosen so that each tone is not used in more than one pair.
  • Different channel signatures may be used for identification of the same channel in association with other parameters in the network, e.g., links or fiber sections carrying the channel. For example, consider the allocation of the channel signature (1,33) to a first optical link carrying channel 1, and (65,33) to a second optical link carrying channel 1. In this case, both channel signatures are unique, but both of them use the same tone, tone #33, in the channel signature.
  • tone #33 If a fault occurs in the network causing a decoder to detect only one tone, for example tone #33, then it is not possible to determine if the channel was carried by the first optical link or the second optical link. However, if channel signatures are allocated so that tones are not reused, then it is possible to determine the optical link, or other network component associated with the channel even though one of the tones cannot be decoded, thus increasing reliability of performance monitoring in the network.
  • Similar elements in Figs. 4b and 4c are labelled by the same reference numerals, with the addition of the letter "a" in Fig. 4c.
  • the tones in each block are chosen as follows.
  • the first tone 56a is the first tone in the tonespace, or ' tone #1, which is equivalent to a frequency of 48000 Hz.
  • the second tone 58a is the second tone in the tonespace, or tone #2
  • the third tone 60a is tone #3, and so on
  • the last tone 60a in the first block is tone #50.
  • the tones in the second block 50a are the next 50 tones in the tonespace, namely tones #51 to tone #100, and so on
  • the tones in the last (Mth) block 54a are the last 50 tones in the tonespace, which are tones #1551 to tone #1600.
  • Table 3 The lists of tones used in blocks 1 to 3 and block 32 used for identifying channels 1 to 3 and channel 32 respectively are illustrated in Table 3.
  • the first three tones in the list used for identifying a channel 1 are tones #1, #2 and #3, and the first three tones in the list used for identifying channel 32 are tones #1551, #1552, and #1553.
  • a channel signature is chosen by selecting a pair of tones from the block that corresponds to the channel.
  • Table 4 illustrates some exemplary choices of tone- pairs to identify channels 1 to 3 and channel 32, respectively.
  • two channel signatures for channel 1 may be the pairs of tones (1,2) and (1,3) .
  • Pairs of tones associated with a particular channel in the network are used to identify different instances of the channel in the network, e.g., each pair of tones associated with the channel may be used for a specified section of the network, e.g., an optical fiber ' , or alternatively it may be used to identify an encoder where the tones were modulated onto the channel or to identify another-, element or parameter in the network. In this way, a simple ⁇ method is provided for identification of a channel and an associated network parameter in an optical network.
  • Fig. 5 illustrates the partition of tones used in a method for identification of channels in an optical network according to a third embodiment of the invention.
  • the first block in the first segment 84 is labelled 88
  • the second block in the first segment 84 is labelled 90
  • blocks 3 to 32 in the first segment 84 are indicated by a dotted line and labelled 92.
  • the first block in ' the second segment 86 is labelled 94
  • the second block in the second segment 86 is labelled 96
  • blocks 3 to 32 in the second segment 86 are indicated by a dotted line and labelled 98.
  • the tones in the first block 88 in the first segment 84 are the first 25 tones in the tonespace 46 shown as in Fig. 1, comprising tone #1, labelled 100, tone #2, labelled 1-02, and tones #3 to #25, indicated by a dotted line and labelled 104.
  • the tones in the second block 90 in the first segment 84 are the next 25 tones comprising tone #26, labelled 106, tone #27, labelled 108, and tones #28 to #50, indicated by a dotted line and labelled 110.
  • the tones in the first block 94 in the second segment 86 comprise tone #801, labelled 112, tone #802, labelled 114, and tones #803 to tone #825, indicated by a dotted line and labelled 116.
  • the tones in the second block 96 in the second segment 86 are the next 25. tones, comprising tone #826, labelled 118, tone #827, labelled 120,. and tones #828 to #850, indicated by a dotted line and labelled 122.
  • Blocks 3 to 32 in the second segment 86 are indicated by a dotted line and labelled 98.
  • Channel signatures for the channels are chosen by selecting pairs in the following manner.
  • the first tone in the pair is chosen from one of the blocks in the first segment, the block in the first segment being used for identifying the channel in question only.
  • the second tone in the pair is chosen from the block in the second segment with the same ordinal number as the block used to choose the first tone in the pair, the block in the second segment being used for identifying the channel in question only. For example, if the first tone in the pair is selected from block 88, then the second tone in the pair is chosen from block 94, or alternatively, if the first tone in the pair is chosen from the block 90, then the second tone in the pair is chosen from the block 96.
  • the number of tone pairs available to identify each channel is 625.
  • Table 5 illustrates examples of channel signatures used to identify channels one to three and channel 32, according to the described allocation scheme of the third embodiment . •
  • two channel signatures for channel one may be the pairs of tone ' s (1,801) and (1,802), and a channel signature for channel 32 may be (775,1575) .
  • Fig. 6a illustrating the partition of the tonespace 46 into M blocks, each block indicated by dotted lines and labelled 126.
  • the block 126 comprises two parts, 128 and 130.
  • the values of M, G, B and C have been chosen as 20, 4, 36 and 11, respectively, although any suitable choice of values for M, G, B and C may be used.
  • a channel signature comprising a pair of tones is chosen in the following manner.
  • the first tone in the pair is chosen from one of the tones 134 in the channel group 132 in the set of channel groups 128 in the block 126. associated with the channel and the band carrying the channel.
  • the first tone in the pair is used to identify the channel only.
  • the second tone in the pair is chosen from the pool of band tones 130 in the same block 126 used to select the first tone.
  • the second tone is used to identify the band carrying the channel only.
  • Table 6 illustrates the list of channel tones for a channel group in a band, and the list of band tones for .the band. For example, referring to table 6, to identify channel 1 in band 1, the first tone may be chosen as tone #1 from channel group 1, and the second tone may be chosen as tone #45 from the pool of band tones for band 1.
  • each channel signature identifies a channel and the band carrying the channel.
  • Table 7 illustrates some examples of channel signatures for channels one to four in band one, channels one to two in band two, and channel one in band four .
  • pairs of tones for each channel the same tone is- not used in more than one pair of tones for a channel on the same fiber (and destined to the same decoder) .
  • pairs (1,45) and (12,45) are not chosen to identify two channels on the same fiber to avoid collision of channel signature, and ensure that tones in the pairs are distinctly detected by the decoder.
  • a channel signature uniquely identifies a channel and also a network parameter associated with the channel .
  • the decoder 24 compares a combination of tones with the list of expected tone combinations. If the decoded tone combination is not found in the list of expected tone combinations, then the tones comprising a pair are mismatched. In this case, the NMS may generate an alarm for the band to indicate a possible failure for the band.
  • any partition of C channel tones per channel group, G channel groups per block, and B band tones per block may be used. Different partitions of M, N, C, G and B may be used, for example, where there are more or less channels in a band, or more or less bands.
  • a physical restriction of the methods of embodiments of the invention is associated with the resolution of the detector and is that, when choosing combinations of tones to modulate a channel, any two tones in a channel signature must have a predetermined frequency difference, for example around 1kHz, in order that each tone can be reliably detected.
  • tone pairs in the method according to the fourth embodiment of the invention is further restricted by generation of a unique summary list across the network for a channel in a band, where a summary list is a non-repeating list of all tones used for the first and second tone of all tone pairs used for a channel.
  • the tones comprising a channel signature are selected from the tonespace 46 of 1600 tones without partitioning the tonespace 46.
  • a channel signature comprising a pair of tones identifies a channel only, and is chosen in the following manner.
  • the first tone in the pair is chosen from one of the tones in the tonespace 46.
  • the second tone in the pair is chosen from one of the remaining tones in the tonespace 46.
  • the combination of the first and second tone is used to identify the channel only.
  • the NMS 16 keeps track of the channel signatures assigned to the channel, for all channels.
  • Table 8 illustrates two example channel signatures for channels one to four.
  • a channel signature may comprise three or more tones. If the channel signature uses a set of three tones, the tones are selected in the same way as in the selection of tones for the first embodiment, except that three tones are selected from the corresponding block for a channel signature. This increases the number of sets available for each channel up to (50 CHOOSE
  • a channel signature comprises five or more tones. Similar modifications may be applied to the second, third and fourth embodiments of the invention.
  • the associated network parameter may be one of the following: a source node in the network where the channel signature is marked, a destination node in the network where the channel signature is detected, an optical fiber carrying the channel, and an optical cable including the optical fiber carrying the channel. Similar modifications may be applied to the second, third and fourth embodiments of the invention.
  • the tones comprising the channel signature may be encoded onto the channel using one, or a combination of, the following modulation techniques: amplitude modulation, frequency modulation, phase modulation and polarization modulation. Similar modifications may be applied to the second, third and fourth embodiments of the invention.
  • the tones comprising the channel signature may be encoded onto the channel simultaneously, consecutively, or by using a combination of simultaneous and consecutive modulation.
  • the order of the consecutive modulation of the tones comprising the channel signature may be significantly determined to allow the same set of tones to be reused for different channel signatures, or for encoding additional information in the channel signature.
  • the set of tones comprising the three frequencies f l7 f 2/ and f 3 may be repeatedly encoded in the order f 1# f 2 , f 3 , i.e.
  • a second repeating sequence of the same tones may be based on the order fi, f 3 , f 2 , thus f l t f 3 , f 2 , fi, f 3 , f 2 , »••
  • These two sequences can be readily distinguished by the decoder regardless of the starting time. With a set of three frequencies, only two different sequences- of repeating consecutive sequences can be thus distinguished. For example the order f 2 , f 3 , fi,'... would not be distinct from the order f l t f 2 , f 3 , ....
  • the encoder may be designed so as to generate a mark, identifying the beginning of the repeating tone sequence, e.g. by slightly increasing the modulation depth of the first tone (or any other tone in the sequence) in the sequence or by modulating the first tone (or any other tone in the sequence) onto an optical channel for a slightly longer period of time.
  • all three different sequences of repeating • consecutive sequences can be thus distinguished. For example the order f 2 , f 3/ fi, ' ... will then be distinct from the order f l7 f 2 , f 3 ,
  • the tone space may be partitioned into three segments.
  • the first two segments comprise 576 tones each, and the third segment comprises 488 tones.
  • Each of the first two segments is further partitioned into 32 blocks of 18 tones in each block.
  • the third segment is partitioned into 32 blocks of 15 tones in each block.
  • a pair of tones for channel identification is chosen in the following manner.
  • the first tone in the pair is chosen by selecting a tone from block "I", the "Ith" block, in the first segment, where "I" is the channel number.
  • the second tone is chosen from "Ith" block in the second segment.
  • the number of tone pairs available to identify each channel using a tone from the first segment and a tone from the second segment is 18*18, or 324 tone pairs.
  • the number of tone pairs can be increased to (18*18) + (18*15) , or 594 tone pairs, by selecting a first tone from "Ith" block in the first segment, and a second tone from “Ith” block in the second segment, or from "Ith” block in the third segment if the available tone pairs are exhausted by using only the first and second segments.
  • the number of tone pairs can be further increased to (18*18) + (18*15) + (18*15) , or 864 tone pairs, by selecting a first tone from "Ith" block in the first or second segment, and a second tone from "Ith” block in the second or third segment, if the available tone pairs are exhausted by using only the first and the second or third segments. In this way, a method for identification of a larger number of channels in an optical network is provided.
  • the band tones are chosen so that they are maximally distributed across the tonespace, where the band tones for each band are contiguous.
  • the channel tones in the band are distributed across the tonespace, where there is a frequency spacing of at least 1 kHz between the channel tone and the band tone, and the difference in frequency between a channel tone and another channel tone for the band . is maximized.
  • the tonespace allocation is a numerical sequence, where the allocation of tones in the tonespace is read from left to right, from top to bottom.
  • the first column in Fig. 7 has the caption "Block 1",. labelled 136, and each cell in the first column illustrates the tones for the four channel groups in block 1.
  • the presence of a number in a cell indicates the first tone of four consecutive tones, where each of the four tones is allocated to each of the four channel groups.
  • the fifth cell in column- 1, labelled 138 shows the caption "289", indicating that the first four channel tones for channel groups 1,2,3, and 4 in block 1 are tones 289, 290, 291 and 292, respectively.
  • the presence of the caption "x" in a cell indicates that no tones are allocated to channel tones in a block in that position in ⁇ the numerical sequence of tones across the tonespace.
  • the sixteenth cell in column 1, labelled 140 indicates that no channel tones are allocated to block 1 at that point in the numerical sequence.
  • the twentieth cell in column 1, labelled 142 has the caption "1433", indicating that the last four channel tones for channel groups 1,2,3, and 4 in block 1 are tones 1433, 1434, 1435 and 1436, respectively.
  • the first cell, labelled 144, in the fourth column has the caption "1", indicating that the first four channel tones for channel groups 1,2,3, and 4 in block 4 are tones 1, 2, 3 and 4, respectively.
  • the first cell, labelled 146, in the twentieth column has the caption "-65”, indicating that the first four channel tones for channel groups 1,2,3, and 4 in block 20 are tones 65, 66, 67 and 68, respectively.
  • the last -column shows the band tones for each block, it has the caption "Corresp Pool” and is labelled 148.
  • the first cell in the last column, labelled 150 has the caption "Pool 1 69-104", indicating that the 36 band tones for block 1 are tones 69, 70, 71, and so on, to tone 104.
  • the remaining steps to select channel signatures in this modification to the method of the fourth embodiment are identical to that of the fourth embodiment.
  • the first, second", third, fourth, and fifth embodiments all provide methods for selecting a pair of tones to comprise a channel signature.
  • the two tones comprising a channel signature may be encoded sequentially in a simple alternating pattern, or in a repeating digital bit sequence pattern where one of the tones represents a logical 0 value, the other tone representing a logical 1 value.
  • the repeating digital bit sequence pattern in combination with the selection of the frequencies of the tones, comprises the channel signature. The use of the repeating bit sequence pattern provides increased reliability of detection, especially in large networks.
  • bit sequence patterns may be used for encoding additional information in the channel signature.
  • Table 9 illustrates the four distinct repeating bit sequence patterns of length 4 using two tones .
  • Table 10 illustrates as another example the twelve distinct repeating bit sequence patterns of length 6 using two tones .
  • two pairs of tones may comprise a channel signature.
  • any four tones from the entire pool of available frequencies could be chosen to generate the two pairs of tones for each channel signature.
  • the frequencies may be selected to have at least a predetermined frequency difference, for example around 1kHz , in order that each tone can be reliably detected.
  • Tone pairs may also be chosen from the blocks of tone pairs allocated to each channel, as described above.
  • the first pair of the two pairs of tones comprising the 2-pair channel signature for a particular channel may be selected from the pool of tones ' as described under the original embodiments .
  • the second pair of tones of the two pairs of tones comprising the 2-pair channel signature may be similarly selected from the pool of tones as described under the original embodiments .
  • Higher detection reliability may be achieved with the additional constraint that none of the frequencies comprised by the second pair of tones may be coincident with any of the frequencies comprised by the first pair of tones.
  • the tone pair (1,801) may be selected for the first pair of a particular 2-tone channel signature for channel 1, and the tone pair (25,824) may be selected as the second pair. In this example, all frequencies of the two tone pairs are distinct.
  • (1,801) is selected as the first pair
  • (1,802) should not be chosen as the second pair for the same channel signature because it contains a frequency already used in the first pair.
  • the channel signature thus comprised of two tone pairs may be modulated as if it were simply a four-tone signature (assuming all four frequencies have been selected to be distinct) as described earlier.
  • the two pairs are modulated in an alternating sequence so that at any time only one of the two tone pairs is present.
  • a repeating bit sequence may be encoded. whereby one tone pair represents a logical 0 value and the other tone pair represents a logical 1 value. Furthermore a selection of more than two tone pairs, or tone sets made up of more than two tones, may be used to increase the. number of possible channel signatures, or to encode additional information with each channel signature, or a combination of the two.

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Abstract

L'invention concerne un procédé et un système permettant d'identifier un canal dans un réseau optique. Ledit canal est identifié par utilisation de combinaisons uniques de deux fréquences ou plus ou de tons modulés sur le canal et, éventuellement, d'un paramètre de réseau associé audit canal.
PCT/CA2003/001829 2003-06-02 2003-11-14 Procede et systeme permettant d'identifier de canaux dans un reseau optique WO2004107625A1 (fr)

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CA002430797A CA2430797C (fr) 2002-09-30 2003-06-02 Methode et systeme d'identification de canaux dans un reseau optique
CA2,430,797 2003-06-02
US10/452,511 2003-06-03
US10/452,511 US7142783B2 (en) 2002-09-30 2003-06-03 Method and system for identification of channels in an optical network

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014015888A1 (fr) 2012-07-26 2014-01-30 Xieon Networks S.À.R.L. Procédé et agencement de configuration de canal dans un réseau wdm optique

Citations (5)

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Publication number Priority date Publication date Assignee Title
EP0782279A2 (fr) * 1995-12-27 1997-07-02 AT&T Corp. Entretien de résaux optiques
WO1999033200A1 (fr) * 1997-12-19 1999-07-01 Tellabs Denmark A/S Procede et systeme pour le codage de signaux multiplexes par repartition en longueur d'onde
US20030067646A1 (en) * 2001-10-05 2003-04-10 Ar Card Channel identification in communications networks
US20030067651A1 (en) * 2001-10-05 2003-04-10 Wan Ping Wai Channel identification in communications networks
US20030067647A1 (en) * 2001-10-05 2003-04-10 Wan Ping Wai Channel identification in communications networks

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0782279A2 (fr) * 1995-12-27 1997-07-02 AT&T Corp. Entretien de résaux optiques
WO1999033200A1 (fr) * 1997-12-19 1999-07-01 Tellabs Denmark A/S Procede et systeme pour le codage de signaux multiplexes par repartition en longueur d'onde
US20030067646A1 (en) * 2001-10-05 2003-04-10 Ar Card Channel identification in communications networks
US20030067651A1 (en) * 2001-10-05 2003-04-10 Wan Ping Wai Channel identification in communications networks
US20030067647A1 (en) * 2001-10-05 2003-04-10 Wan Ping Wai Channel identification in communications networks

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014015888A1 (fr) 2012-07-26 2014-01-30 Xieon Networks S.À.R.L. Procédé et agencement de configuration de canal dans un réseau wdm optique
US9621261B2 (en) 2012-07-26 2017-04-11 Xieon Networks S.A.R.L. Method and arrangement for channel set up in an optical WDM-network

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