Method for allocating a point-to-point channel to a user module of an optical communication network, corresponding computer program product, storage medium and device

Abstract

A method for allocating a point-to-point channel to a user module of an optical communication network. The network includes user modules and optical terminations, and supports point-to-multipoint channels and a plurality of point-to-point channels, one same point-to-point channel being assigned to one single optical termination. The method is implemented for a user module called a requester user module, and includes: detecting a predetermined availability signal conveyed by a point-to-point channel of the plurality of point-to-point channels; and allocating the point-to-point channel over which the predetermined availability signal is conveyed, called available point-to-point channel, to the requester user module.

Claims

1. A method for allocating a point-to-point channel to a user module of an optical communication network, said network comprising user modules and optical terminations, and supporting point-to-multipoint channels and a plurality of point-to-point channels, one same point-to-point channel being assigned to one single optical termination, said method being implemented by at least one device for a user module called requester user module, and comprising: detecting a predetermined availability signal conveyed by a point-to-point channel of said plurality of point-to-point channels, and allocating the point-to-point channel over which said predetermined availability signal is conveyed, called available point-to-point channel, to said requester user module, wherein the detecting comprises verifying, on each point-to-point channel of said plurality of point-to-point channels, whether the predetermined availability signal is detected, and wherein the allocating comprises: in the case of a positive verification for one single point-to-point channel of said plurality, allocating said single point-to-point channel to said requester user module; in the case of a positive verification for a set of point-to-point channels of said plurality, allocating the point-to-point channel to said requester user module selected amongst said set of point-to-point channels, as function of a predetermined communication quality criterion.

2. The method according to claim 1, wherein the detecting is triggered on apparition of a condition belonging to the group consisting of: detecting a request for allocating a point-to-point channel; detecting a malfunction of an optical termination; deducting a preprogramed maintenance of an optical termination; introducing a new user module in the network; introducing a new optical termination in the network; detecting a point-to-point channel change request; detecting a communication quality level below a predetermined threshold between a user module and an optical termination of the network involved in a point-to-point channel of said plurality.

3. The method according to claim 1, further comprising, before allocating the available point-to-point channel, transmitting over the available point-to-point channel a query for using the available point-to-point channel, to the optical termination to which said available point-to-point channel is assigned.

4. The method according to claim 1, wherein an entity internal to the requester user module or external to the requester user module performs the allocating of the point-to-point channel.

5. A method for allocating a point-to-point channel to a user module of an optical communication network, said network comprising user modules and optical terminations, and supporting point-to-multipoint channels and a plurality of point-to-point channels, one same point-to-point channel being assigned to one single optical termination, said method being implemented by an optical termination of said plurality, called available optical termination, and comprises: emitting a predetermined availability signal over the point-to-point channel assigned to said available optical termination, called available point-to-point channel, towards the user modules, wherein the predetermined availability signal comprises information belonging to the group consisting of: information representative of a reference number associated to the available point-to-point channel; information representative of a wavelength associated to the available point-to-point channel: information representative of a frequency associated to the available point-to-point channel; information representative of a modulation rate associated to the available point-to-point channel; and queuing a query for using the available point-to-point channel, originating from a user module, called requester user module.

6. The method according to claim 5, further comprising, upon reception of the query for using the available point-to-point channel: stopping the emission of the predetermined availability signal over the available point-to point channel; verifying feasibility of establishment of a point-to-point communication over the available point-to-point channel between said requester user module and said available optical termination.

7. The method according to claim 6, further comprising: in the case of a positive verification, establishing a point-to-point communication over the available point-to-point channel between said requester user module and said available optical termination; in the case of a negative verification, re-emitting the predetermined availability signal over the available point-to-point channel.

8. The method according to claim 5, wherein the predetermined availability signal is emitted continuously.

9. The method according to claim 5, wherein the predetermined availability signal is emitted discontinuously.

10. A non-transitory computer-readable medium comprising program code instructions stored thereon which when executed by a processor configure the processor to implement a method for allocating a point-to-point channel to a user module of an optical communication network, said network comprising user modules and optical terminations, and supporting point-to-multipoint channels and a plurality of point-to-point channels, one same point-to-point channel being assigned to one single optical termination, said method being implemented for a user module called requester user module, and comprising: detecting a predetermined availability signal conveyed by a point-to-point channel of said plurality of point-to-point channels, and allocating the point-to-point channel over which said predetermined availability signal is conveyed, called available point-to-point channel, to said requester user module, wherein the detecting comprises verifying, on each point-to-point channel of said plurality of point-to-point channels, whether the predetermined availability signal is detected, and wherein the allocating comprises: in the case of a positive verification for one single point-to-point channel of said plurality, allocating said single point-to-point channel to said requester user module; in the case of a positive verification for a set of point-to-point channels of said plurality, allocating the point-to-point channel to said requester user module selected amongst said set of point-to-point channels, as function of a predetermined communication quality criterion.

11. A device for allocating a point-to-point channel to a user module of an optical communication network, said network comprising user modules and optical terminations, and supporting point-to-multipoint channels and a plurality of point-to-point channels, one same point-to-point channel being assigned to one single optical termination, said device comprising, for a user module called requester user module: a processor; and a non-transitory computer-readable medium comprising instructions stored thereon which when executed by the processor configure the device to: detect a predetermined availability signal conveyed by a point-to-point channel of said plurality of point-to-point channels, and allocating the point-to-point channel over which said predetermined availability signal is conveyed, called available point-to-point channel, to said requester user module, wherein the detecting comprises verifying, on each point-to-point channel of said plurality of point-to-point channels, whether the predetermined availability signal is detected, and wherein the allocating comprises: in the case of a positive verification for one single point-to-point channel of said plurality, allocating said single point-to-point channel to said requester user module; in the case of a positive verification for a set of point-to-point channels of said plurality, allocating the point-to-point channel to said requester user module selected amongst said set of point-to-point channels, as function of a predetermined communication quality criterion.

12. An optical termination for implementation in an optical communication network, comprising user modules and optical terminations, and supporting point-to-multipoint channels and a plurality of point-to-point channels, one same point-to-point channel being assigned to one single optical termination, said optical termination comprising: a processor; and a non-transitory computer-readable medium comprising instructions stored thereon which when executed by the processor configure the optical termination to: emit a predetermined availability signal over the point-to-point channel assigned to said available optical termination, called available point-to-point channel, towards the user modules, wherein the predetermined availability signal comprises information belonging to the group consisting of: information representative of a reference number associated to the available point-to-point channel; information representative of a wavelength associated to the available point-to-point channel: information representative of a frequency associated to the available point-to-point channel; information representative of a modulation rate associated to the available point-to-point channel; and queue a query for using the available point-to-point channel originating from a user module, called requester user module.

Description

LIST OF THE FIGURES

(1) Other features and advantages of the invention will become apparent on reading the following description provided as an indicative and non-limiting example, and from the appended drawings, wherein:

(2) FIG. 1, already described in connection with the prior art, schematically represents a conventional PON TWDM communication network;

(3) FIG. 2, already described in connection with the prior art, schematically represents a PON communication network based on both a point-to-multipoint transmission mode (TWDM) and a point-to-point transmission mode (WDM);

(4) FIG. 3 presents a simplified diagram of an optical communication network in which the method according to a particular embodiment of the invention is implemented;

(5) FIG. 4 is a flowchart of a particular embodiment of the method according to the invention;

(6) FIG. 5 presents an events chart showing in a generic way the progress of the method between a user module and an optical termination of the network;

(7) FIG. 6 presents an example of a structure of a predetermined availability signal used in the context of the invention;

(8) FIG. 7 presents the structure of an application server according to a particular embodiment of the invention.

DETAILED DESCRIPTION

(9) In all figures of the present document, identical elements and steps are referred to by the same reference numeral.

(10) In the following description, an example of implementation of the invention in a PON-type optical access network is considered. Of course, the invention is not limited to this particular example, and may apply to any optical communication network implementing a plurality of point-to-point channels.

(11) FIG. 3 presents a schematic example of an optical communication network 300 in which the allocation method according to a particular embodiment of the invention is implemented. For example, it may consist of a PON network based on both a point-to-multipoint transmission mode (TWDM) and a point-to-point transmission mode (WDM). Only the portion of the network relating to the point-to-point communications is herein represented in the figure, to simplify the description thereof.

(12) Such an optical network 300 comprises three optical terminations P2P_CT1, P2P_CT3, P2P_CT4, a wavelength multiplexer 110, an optical fibre 200, an achromatic coupler 310, as well as three user modules P2P_ONU1, P2P_ONU2, P2P_ONU3. The optical terminations P2P_CT1, P2P_CT3, P2P_CT4 and the multiplexer 110 comprised within the terminal 350 are configured to optically serve the remote user modules by means of the optical fibre 200 and via the achromatic coupler 310. The optical network 300 is herein configured to support a set of four point-to-point optical channels, with the wavelengths λ1, λ2, λ3 and λ4, characteristic of the optical terminations P2P_CT1, P2P_CT2, P2P_CT3, P2P_CT4 respectively.

(13) In general, a distinct point-to-point channel is assigned to each optical termination of the network and each user module is associated to the set (or to a subset) of the point-to-point channels. Thus, by “assigned”, it should be understood that the considered channel is definitively associated, that is to say allocated to the optical termination for the establishment of a determined point-to-point communication, and by “associated”, it should be understood that the considered channel is provisionally associated to the optical module to carry out the phase of detecting an available point-to-point channel before the allocation phase itself. Indeed, in order to avoid using the same term “allocation” to both the optical terminations and the user modules, the term “assignment” is herein used specifically for the optical terminations, and the term “allocation” is herein used specifically for the point-to-point user modules.

(14) It will be considered in the particular example herein illustrated that the optical terminations P2P_CT1 and P2P_CT4 are in service with the user modules P2P_ONU1 and P2P_ONU2 respectively. An optical termination is called in service when it is already involved in a point-to-point communication with a point-to-point user module via the point-to-point channel that has been assigned thereto beforehand, and that, consequently, it is in an unavailability state for the allocating its point-to-point channel to another point-to-point user module.

(15) In turn, the optical termination P2P_CT2 is not connected to the multiplexer 110; it is therefore also considered as unavailable. In contrast, the optical termination P2P_CT3 is available. Thus, the point-to-point channel with the wavelength λ3 that is assigned thereto is a point-to-point channel considered as available and able to be allocated to a user module in order to establish a point-to-point communication via this channel.

(16) It should be understood that the number of user modules and optical terminations (and therefore the number of point-to-point channels) discussed herein is intentionally limited, for purely pedagogical description purposes, so as not to overload the figure and the associated description. Indeed, a larger number of pieces of equipment may be considered without departing from the invention.

(17) FIG. 4 represents a flowchart of a particular embodiment of the allocation method according to the invention. This flowchart comprises the main steps for implementing the method, which are applied each time a request for allocating a point-to-point channel to a user module of the network is initiated. Some of these steps are performed by an optical termination called available termination of the network and others are performed by a user module, called requester of the network. In order to facilitate understanding of the present invention, these steps are also represented in FIG. 5 in the form of an events chart illustrating the progress of the method.

(18) As discussed in more details hereinafter, the method is based on a new approach consisting in finding an available point-to-point channel amongst the set of point-to-point channels of the network upon detecting a predetermined availability signal conveyed by this channel.

(19) The method is initialised upon request for allocating to a user module a point-to-point channel, amongst the set of point-to-point channels supported by the network 300. The introduction of a new user module P2P_ONU3 in the network 300 is herein considered. This new user module P2P_ONU3 is optically connected to the achromatic coupler 310 so that it is associated to the set of point-to-point channels of the network, with the wavelengths λ1, λ2, λ3 and λ4 (but still not allocated to any of these point-to-point channels).

(20) At step 410 (denoted “EMI_SD”), for the allocating a point-to-point channel to the user module P2P_ONU3, the available optical termination P2P_CT3 of the terminal 350 proceeds with the emission of a predetermined availability signal over the point-to-point channel assigned thereto, that is to say the channel with the wavelength λ3. According to a particular implementation, the predetermined availability signal is continuously emitted and has a particular optical signature recognisable by all of the user modules of the network. The predetermined availability signal is materialised by the arrows A in FIG. 5 and its structure is detailed further hereinafter with reference to FIG. 6.

(21) It should be noted that if several optical terminations of the network are available, each of these optical terminations emits the predetermined availability signal via the point-to-point channel assigned thereto.

(22) According to a variant of implementation, the predetermined availability signal is discontinuously emitted by the optical termination, according to a predefined sequencing. This enables the optical termination concerned by the emission to reduce its energy consumption.

(23) Regardless of the emission mode implemented by the optical termination (continuous or discontinuous), the availability signal is emitted as long as no use query is received from a user module (as described later on in connection with step 440). Hence, the optical termination P2P_CT3 is put on hold waiting for a query for using a point-to-point channel originating from a user module having received the predetermined availability signal.

(24) At step 420 (denoted “DET_SD”), the user module P2P_ONU3 requesting an allocation proceeds with a sequential scanning (or probing) of the different point-to-point channels associated thereto, in order to detect the predetermined availability signal that might be conveyed by one (or several) point-to-point channel(s) of the network 300. For this step, the user module P2P_ONU3 uses a “listen”, or “receive”, mode configuration. For this purpose, the user module P2P_ONU3 connects to (or is positioned on) a first point-to-point channel and verifies whether an availability signal is detected via this first point-to-point channel. For this purpose, the user module P2P_ONU3 has a local table, stored in its memory, comprising for example the list of all point-to-point channels of the network 300 to which it is associated (namely the channels with the wavelengths λ1, λ2, λ3 and λ4). The user module P2P_ONU3 then connects (in the receive-only mode) to (or is positioned on) the first point-to-point channel of the list, namely the channel with the wavelength λ1 and verifies whether an availability signal is conveyed by this channel. Yet, in the present example, the availability signal emitted by the termination P2P_CT3 is not conveyed by the channel with the wavelength λ1. Although point-to-point communications are exchanged over this first channel (recall that P2P_CT1 and P2P_ONU1 are in service), no availability signal is detected by the user module P2P_ONU3 over this first channel. Consequently, the user module P2P_ONU3 stops its connection with the channel with the wavelength λ1 and connects (in the receive-only mode) to (or is positioned on) the second point-to-point channel of the list, namely the channel with the wavelength λ2, and verifies whether the availability signal is conveyed by this second channel. Yet, no optical signal (including the availability signal) is detected over this second channel (the termination P2P_CT2 is not connected). The user module P2P_ONU3 then stops its connection with the channel with the wavelength λ2 and connects (in the receive-only mode) to (or is positioned on) the third point-to-point channel of the list, namely the channel with the wavelength λ3. This time, the user module P2P_ONU3 detects that an availability signal is actually conveyed by this third point-to-point channel, and then stops scanning of the point-to-point channels.

(25) Thus, in this particular implementation, each point-to-point channel is probed by the user module until the latter detects the availability signal. After detecting the availability signal, probing is stopped and the point-to-point channel conveying the availability signal is considered as the available point-to-point channel to be allocated to the user module. This particular implementation aims to probe a reduced number of point-to-point channels, in order to reduce the energy consumption of the user module. This is a particular implementation of channels probing, and other implementations may of course be considered without departing from the context of the invention. For example, in another particular implementation, it may be considered that the user module proceeds with an exhaustive probing of all of the point-to-point channels and verifies whether a predetermined availability signal is detected for each probed point-to-point channel. Then, two situations may arise. In the case of a positive verification for one single point-to-point channel, this single point-to-point channel is allocated to the user module. In the case of a positive verification for a set of point-to-point channels, a point-to-point channel selected amongst said set of point-to-point channels, according to a predetermined communication quality criterion (for example the point-to-point channel having the highest point-to-point communication quality level of said set) is allocated to the user module.

(26) It should also be noted that steps 410 and 420 may be activated either sequentially, that is to say the step of emission 410 by the optical termination and then the step of detection by the user module, or else they may be activated simultaneously.

(27) At step 430 (denoted “ALL_CP2P”), the user module P2P_ONU3 then proceeds with the allocating the point-to-point channel with the wavelength λ3 (available channel over which the availability signal is conveyed). In this example, the allocation is carried out by configuration of the transmitter internal to the user module P2P_ONU3 on the wavelength λ3 in order to enable a communication over the point-to-point channel with the wavelength λ3.

(28) At step 440 (denoted “REQ_UTI”), the user module P2P_ONU3 then transmits over the allocated point-to-point channel with the wavelength λ3 a query for using this point-to-point channel λ3 towards the optical termination P2P_CT3. This step aims to inform the optical termination concerned by the available point-to-point channel (P2P_CT3) on the intent of the requester user module (P2P_ONU3) to establish a point-to-point communication with it via this channel.

(29) The use query is materialised by the arrow B in FIG. 5.

(30) It should be noted that when the user module P2P_ONU3 detects the availability signal on the point-to-point channel λ3, the wavelength on which the user module P2P_ONU3 must be tuned to transmit the use query over this point-to-point channel λ3 is determined either implicitly by recognizing the point-to-point channel λ3 over which the availability signal is conveyed (a wavelength predefined in the standard), or explicitly by means of the information contained in the availability signal (whose principle is detailed later on with reference to FIG. 6).

(31) At step 450 (denoted “REQ_UTI”), upon reception of the query for using the point-to-point channel λ3, the optical termination P2P_CT3 stops the emission of the predetermined availability signal initiated at step 410 and begins a procedure of verifying the feasibility of the establishment of a point-to-point communication with the user module P2P_ONU3. Stopping the emission of the predetermined availability signal means that the optical termination P2P_CT3 is no longer available.

(32) The procedure of verifying the feasibility of the establishment of a point-to-point communication consists in an exchange of one or several query(ies) between the optical termination P2P_CT3 and the user module P2P_ONU3 using the point-to-point channel λ3 (materialised as example by the arrows C and D in FIG. 5). This procedure is based on a predefined point-to-point communication start protocol and is intended to stabilise the point-to-point connectivity between the two pieces of equipment.

(33) In the case of a positive verification (of the feasibility of the establishment of a point-to-point communication with the user module P2P_ONU3), the allocating the point-to-point channel λ3 to the user module P2P_ONU3 is considered to be successful and a point-to-point communication over the point-to-point channel λ3 is established (step 460 (denoted “ETA_CP2P”). The point-to-point channel λ3 is then considered as unavailable.

(34) In the case of a negative verification (of the feasibility of the establishment of a point-to-point communication with the user module P2P_ONU3), the algorithm returns to step 410 of the method and the optical termination P2P_CT3 proceeds again with the emission of the predetermined availability signal over the point-to-point channel λ3. Prior to that, the optical termination P2P_CT3 may send to the user module P2P_ONU3 a query of failure of the allocating the point-to-point channel λ3, in order to inform it that the allocating the point-to-point channel λ3 has not finally succeeded and that this channel becomes available again.

(35) The above-described determination method is initialised upon request for allocating an available point-to-point channel of a user module newly-introduced in the network. In this instance, this is a particular example of application and the method may be implemented on apparition or occurrence of one of the following events (non-exhaustive list): detecting a malfunction of an optical termination; preprogramed maintenance of an optical termination; introducing a new user module in the network; introducing a new optical termination in the network; detecting a point-to-point channel change request; detecting a communication quality level below a predetermined threshold between a user module and an optical termination of the network involved in a point-to-point communication.

(36) The request for allocating an available point-to-point channel may be initiated by an optical termination or by a user module of the terminal or else by another piece of equipment for example by a managing module of the network 300 (independently of the user modules or of the optical terminations).

(37) FIG. 6 illustrates a schematic example of an availability signal 600 in accordance with the present invention. The availability signal 600 comprises a header field 610, a useful data field 620 (encoded on 32 bits for example) and a protection field 630. The header field 610 is encoded for example on 32 bits in a NRZ (standing for “non-return-to-zero”) type modulation, and contains an identifier of the optical termination emitter of the availability signal and information representative of the type of the signal conveyed herein, namely an availability signal. The useful data field 620 comprises information relating to the available point-to-point channel over which the availability signal is conveyed, namely the wavelength associated to the concerned point-to-point channel or the frequency associated to the concerned point-to-point channel or the reference number of the concerned point-to-point channel or else the modulation rate associated to the concerned point-to-point channel. The protection field 630 contains the data that are necessary to the application of protective encoding against errors of the header 610 and useful data 620 fields using an error-correcting code.

(38) For example, the availability signal according to the invention may be transmitted in the form of a low-frequency clock signal (typically in the range of 1 MHz) whose signature allows differentiating it from the other known signals transmitted over the network 300.

(39) FIG. 7 presents the simplified structure of a device 700 implementing the allocation method according to the invention (for example the particular embodiment described hereinabove with reference to FIGS. 4 to 6). This device 700 comprises a random-access memory 730 (for example a RAM memory), a processing unit 710 equipped for example with a processor, and driven by a computer program stored in a read-only memory 720 (for example a ROM memory or a hard disk). Upon initialisation, the code instructions of the computer program are for example loaded in the random-access memory 730 before being executed by the processor of the processing unit 710. Such a computer program enables the execution of part of the steps of the algorithm of FIG. 4 described hereinabove (steps 420, 430, 440, 460) if executed by a smart entity internal to the user module, or of the other part of the steps of the algorithm of FIG. 4 described hereinabove (410, 450), if executed by an optical termination.

(40) In one variant, it is possible to consider that it is actually a smart entity external to the user module and to the optical termination that undertakes the completion of the step of allocating a point-to-point channel to the concerned user module. More particularly, it may be considered that it is this external entity (located for example in the central office CO) that initiates the algorithm of FIG. 6 and sends commands for executing the steps dedicated to the optical termination and to the user module respectively, according to the above-described principle.

(41) This FIG. 7 illustrates only a particular way, amongst many others, for carrying out the different algorithms detailed hereinabove, with reference to FIG. 4. Indeed, the technique of the invention is carried out indifferently: on a reprogrammable calculation machine (a PC computer, a DSP processor or a microcontroller) executing a program comprising an instructions sequence, or on a dedicated calculation machine (for example a set of logic gates such as a FPGA or an ASIC or any other hardware module).

(42) In the case where the invention is set up on a reprogrammable calculation machine, the corresponding program (that is to say the instructions sequence) may be stored in a storage medium, whether removable (such as a floppy disk, a CD-ROM or a DVD-ROM) or not, this storage medium being partially or totally readable by a computer or a processor.