Methods and devices for processing uplink data for cascaded passive optical networks

Abstract

The invention relates to a method for uplink data transmission, implemented in an apparatus (FGW) at the boundary between a first passive optical network (PON1) and a second passive optical network (PON2) and comprising a receive protocol stack and a transmit protocol stack, the data (Tm) being received at a physical layer (L1) of the receive stack in a first uplink optical burst originating from the second passive optical network (PON2), the method comprising in series: • at a sublayer (L2m) of the transport layer of the receive stack, referred to as the encapsulation level, transmitting the data (Tm') directly to a service layer (L3) of the transmit stack, without processing by sublayers above the encapsulation level in the receive stack; • successively processing in the transmission stack, by the service layer (L3), by a transport layer (L2) and by a physical layer (L1); and • transmitting the data (Tm') in a second uplink optical burst to the first passive optical network (PON1).

Description

Methods and devices for processing uplink data for cascaded passive optical networks 1. Field of the invention

[0001] The invention is in the field of optical telecommunications (optical fiber) and access networks of the “passive optical network” (PON) type.

[0002] A passive optical network, or PON, refers to a layer 1 fiber optic transport principle used in optical delivery networks (FTTx, "Fiber To The x"). It is characterized by a passive point-to-multipoint fiber architecture (several users share the same optical fiber and there is no active equipment between the central office and the subscribers).

[0003] There are various ITU (International Telecommunications Union) PON network standards, including GPON (ITU-T G.984 standard), XGS-PON (ITU-T G.9807 standard), NG-PON2 (ITU-T G.989 standard), HS-PON (ITU-T G.9804 standard), etc., as well as various IEEE ("Institute of Electrical and Electronics Engineers") standards, such as E-PON, 10GE-PON, 50GE-PON, etc. 2. State of the prior art

[0004] In this context, the optical line terminal, or OLT, ("Optical Line Terminal") at the operator's central office connects optical network units, or ONUs ("Optical Network Unit") deployed at customer premises. The low cost of PONs, their maturity and their point-to-multipoint topology make them interesting for applications beyond FTTH ("Fiber To The Home"): FTTR ("fiber to the room", deployment of an optical skeleton within the home to connect, for example, the home gateway with the Wi-Fi access points in each room), POL ("Passive optical LAN": optical LAN for businesses - LAN: "Local Ara Network"), FTTM ("Fiber to the machine: use of PON technology to connect the machines in a factory / warehouse / … to the network), etc.

[0005] To date, a natural solution for achieving FTTR / POL / FTTM would be to cascade PON technologies. In the case of FTTR, for example, a first PON stage would connect the operator's central office equipped with an OLT to the home equipped with an ONU in a home gateway, and a second PON stage would distribute the signal to the different rooms of the home with a second OLT in the home gateway and rooms equipped with ONUs. However, this requires the deployment of heavy equipment (in the functional sense) in the customer's home, such as an OLT functionality added in the home gateway, and equipment providing ONU functionality in the different rooms.

[0006] PON technologies are based on a specific protocol stack, required to manage the specific PON (point-to-multipoint) topology, allowing the transparent encapsulation and decapsulation of conventional Ethernet frames. ITU PON technologies use the TC ("Transmission Convergence") layer, which has several functions performed in series, including the encapsulation of data or management flows in GEM ("Gigabit-capable passive optical network Encapsulation Method") frames, then GTC ("Gigabit-capable passive optical network Transmission Convergence") frames, which are then encoded and scrambled. Headers in these frames are used to manage the "routing" of frames, and the priorities associated with services. The resulting binary sequence is transposed into the analog (electrical) domain and is used to modulate the optical carrier which thus carries the information.The optical signal is then received, and the received binary sequence is in turn "unscrambled", decoded, and decapsulated. The frame headers that carry the routing information then allow traffic to be directed to the correct destination with the associated priority.

[0007] The protocol stack is traversed in both directions of transmission (from the OLT to the ONU for downstream traffic, and vice versa for upstream traffic). Cascading multiple PON trees involves doing this at each stage of the cascade, which represents very heavy operations for equipment located outside the operator's central office. The fact that these operations are performed on electronic cards outside the domain controlled by the operator (the central office) also limits the miniaturization of equipment, the latter point being important in certain scenarios such as domestic use. This also implies an energy cost that is then charged to the user.

[0008] One of the aims of the invention is to remedy these drawbacks of the state of the art. 3. Statement of the invention

[0009] Downward direction

[0010] The invention improves the situation by means of a method for transmitting data in a downlink optical signal, implemented in a first optical line terminal of a first passive optical network, the data being received at a service layer, then processed successively by the service layer, a transport layer and a physical layer, then transmitted at the physical layer, the method comprising, at the service layer, processing of the data relating to at least one sub-layer of the transport layer, called encapsulation, before transmission of the processed data to the transport layer.

[0011] In this method, data is encapsulated in sub-layers of the transport layer by processing at the service layer. The data then undergoes the classic transport layer and physical layer processing.

[0012] Thus, if this data is intended for a second PON in cascade of the first PON, the processing that the OLT of this second PON must apply to the data is lightened. Indeed, when this data is received by an ONU of the first PON, after the successive processing of the physical layer, the transport layer and the service layer, it is in a format already including the processing carried out by the OLT of the first PON, and which are related to the transport layer. The OLT of the second PON only has to complete with the processing that was not carried out in the OLT of the first PON.

[0013] It is understood that the method according to the invention can be seen as consisting of moving a part of the protocol stack from the second PON to the first PON. More precisely, the service layer, as well as the part of the transport layer located above a cutout, are moved from the OLT of the second PON to the OLT of the first PON, to be processed there at the level of the service layer which is above the transport layer, without the transport layer of the first OLT being modified.

[0014] Thus, the data frames are transmitted with this encapsulation by the first OLT, are received in an optical signal by an ONU of the first PON. The data frames recovered by the ONU after unstacking are transmitted to the second OLT serving the second PON, directly at the sub-layer just below the cutout.

[0015] The second OLT does not need to perform any processing related to the sub-layer (or sub-layers) of the transport layer above the cutout. The second OLT only needs to apply to these frames processing related to the remaining sub-layer (or sub-layers) below the cutout of the transport layer, i.e. processing of the sub-layers that have not been encapsulated by the first OLT (which notably include all the sub-layers of the physical layer). This reduces the processing that the second OLT must perform before transmitting the data frames to a second ONU of the second PON.

[0016] The split between encapsulated and unencapsulated sub-layers can be determined based on the processing capabilities of the second OLT, or other criteria such as available computing resources or available power supply.

[0017] For convenience in this document, the term "encapsulation" generally refers to any processing performed in the transport layer to prepare a data frame for processing by the physical layer, i.e., in the downward direction of the protocol stack, from the so-called upper layers to the so-called lower layers. Transport layer processing in the downward direction includes, for example, depending on the sub-layer concerned, fragmentation, encryption, embedding of OAM (Operation Administration & Maintenance) information, scrambling, etc.

[0018] This transmission process is completely transparent for the ONUs of the first PON and for the ONUs of the second PON, and allows for a reduction in processing within the second OLT, which results in savings in terms of required computing power and necessary energy. This is advantageous because this second OLT, which is at the root of the second PON, is not located in an operator's central office but rather at a customer's premises where the ONU is located, in hardware equipment that can be either physically connected to the customer's ONU or integrated with the customer's ONU.

[0019] According to one aspect of the transmission method, the encapsulation relates to all sub-layers of the transport layer.

[0020] In other words, according to this aspect, the method comprises, for data frames intended for the second ONU, and prior to processing at the transport layer and at the physical layer, encapsulation of the data frames throughout the transport layer.

[0021] Thus, when the cut is between the physical layer and the transport layer, i.e. with encapsulation, by the first OLT, of the entire transport layer, the second OLT no longer has to perform any processing at the transport layer for the data frames, and can transmit them directly to its physical layer. This minimizes the processing that the second OLT must perform for the data frames intended for ONUs of the second PON.

[0022] According to one aspect, the transmission method comprises, at the service layer and prior to encapsulation, another encapsulation relating to at least one sub-layer of the transport layer.

[0023] Thus, if more than 2 PONs are arranged in cascade, that is to say if the second ONU of the second PON is connected to a third OLT at the root of a third PON, this third OLT can also save processing at the service and transport layers. In the OLT of the first PON, the frames intended for an ONU of this third PON are encapsulated a first time according to a transport layer division specific to the third PON, then encapsulated a second time according to a transport layer division specific to the second PON. Indeed, the divisions of the protocol stack for encapsulation can be different from one PON cascade stage to another.

[0024] The invention is not limited to two or three cascaded passive optical networks. Thus, if N PONs are cascaded, the frames intended for an ONU of this N-th PON can be encapsulated N-1 times according to the successive cuts of the transport layer of each of the PONs, starting with the cut of the N-th PON and ending with that of the second PON.

[0025] The invention also relates to a method for downlink data transmission, implemented in equipment at the border between a first passive optical network and a second passive optical network and comprising a reception protocol stack and a transmission protocol stack, the data being received in a first downlink optical signal from the first passive optical network, at a physical layer of the reception stack, then processed successively in the reception stack by the physical layer (L1), a transport layer (L2) and a service layer (L3), the method comprising:at the service layer, a detection of an encapsulation of the data relative to at least one sub-layer (L2d') of the transport layer (L2),a transmission of the encapsulated data, from the reception stack to the transmission stack, directly at a level (L2d) immediately below the at least one transport sub-layer, called the encapsulation level,without processing relating to the at least one transport sub-layer, successive processing in the transmission stack up to a physical layer (L1), from the encapsulation level, transmission of the data in a second downlink optical signal, towards the second passive optical network (PON2).,

[0026] Thanks to the encapsulation of the frames which is carried out in the first OLT of the first PON, the second OLT of the second PON saves the processing relating to the encapsulated sub-layers, since they have already been carried out at the level of the first OLT. This lightens the equipment hosting the second OLT, which is particularly advantageous in the case where this equipment is located at a customer of the operator of the first PON. In addition, since an ONU of the first PON is already located in the same place, this lightening facilitates the integration of the second OLT with the ONU of the first PON in a single FGW hardware device (for Fiber Gateway), which can be an optical network gateway, such as for example a modified home or professional Internet access gateway.

[0027] The choice of the sub-layers that are encapsulated in the downstream direction is made according to a division of the protocol stack which determines the part of this stack which is functionally deported from the second PON to the OLT of the first PON. As a result, the division determines a complementary link between the first and second OLTs.

[0028] In this downlink transmission method, the ONU functionality of the integrated equipment detects at the service layer the presence or absence of encapsulation. If encapsulation is present, this means that the frame is intended to continue its path to the second PON, which is cascaded to the first PON. If encapsulation is absent, this means that the frame has the ONU function as its destination, or more precisely, has as its final destination a device connected to a local network served by the ONU, for example a home Wi-Fi network.

[0029] The invention also relates to a device for transmitting data in a downlink optical signal, included in a first optical line terminal of a first passive optical network, the data being received at a service layer, then processed successively by the service layer, a transport layer and a physical layer, then transmitted at the physical layer, the device comprising receivers, transmitters, a processor and a memory coupled to the processor with instructions intended to be executed by the processor for, at the service layer, processing of the data relating to at least one sub-layer of the transport layer, called encapsulation, before transmission of the processed data to the transport layer.

[0030] This device, capable of implementing in all its embodiments the transmission method which has just been described, is intended to be implemented in an optical line terminal serving optical network units through a first passive optical network, at least one of which is connected to another optical network terminal serving other optical network units through a second passive optical network.

[0031] According to one aspect, the transmission device further comprises a first unit for managing configurations, faults, performances, and security of the first passive optical network, and a second unit for managing configurations, faults, performances, and security of the second passive optical network.

[0032] When two passive optical networks are cascaded, according to the invention and unlike the prior art, it is the optical line terminal of the first passive optical network that manages the configurations, faults, performances, and security of the passive optical networks of each stage of the cascade. The relocation of this function to the first optical line terminal thus relieves the optical line terminals of the second stage of the cascade, while allowing synchronized and harmonized management of the OMCI (ONU Management and Control Interface) messages circulating in all the passive optical networks of the cascade.

[0033] The invention also relates to a device for downlink data transmission, included in equipment at the border between a first passive optical network and a second passive optical network and comprising a reception protocol stack and a transmission protocol stack, the data being received in a first downlink optical signal from the first passive optical network, at a physical layer of the reception stack, then processed successively in the reception stack by the physical layer, a transport layer and a service layer, the device comprising receivers, transmitters, a processor and a memory coupled to the processor with instructions intended to be executed by the processor for:at the service layer, a detection of an encapsulation of the data relative to at least one sub-layer of the transport layer,a transmission of the encapsulated data,from the reception stack to the transmission stack, directly at a level immediately below the at least one transport sub-layer, called the encapsulation level, without processing relating to the at least one transport sub-layer, successive processing in the transmission stack up to a physical layer, from the encapsulation level, transmission of the data in a second downlink optical signal, to the second passive optical network.,

[0034] This device, capable of implementing in all its embodiments the downlink transmission method which has just been described, is intended to be implemented in an optical network gateway, such as for example a "fiber" gateway for access to the Internet, domestic or professional.

[0035] The invention also relates to a system of cascaded passive optical networks for transmitting downlink data, comprising a transmitting device, such as that which has just been described, connected to a plurality of downlink transmission devices such as that which has just been described, through the first passive optical network, at least one such downlink transmission device being connected to a plurality of optical network units through a second passive optical.

[0036] The invention also relates to a computer program comprising instructions which, when these instructions are executed by a processor, cause the latter to implement the steps of the transmission method, which has just been described.

[0037] The invention also relates to an information medium readable by an optical network terminal, and comprising instructions of a computer program as mentioned above.

[0038] The invention also relates to a computer program comprising instructions which, when these instructions are executed by a processor, cause the latter to implement the steps of the downward transmission method, which has just been described.

[0039] The invention also relates to an information medium readable for example by a fiber gateway for Internet access, and comprising instructions of a computer program as mentioned above.

[0040] Upward direction

[0041] The invention improves the situation using a method for uplink data transmission, implemented in equipment at the border between a first passive optical network and a second passive optical network and comprising a reception protocol stack and a transmission protocol stack, the data being received at a physical layer of the reception stack in a first uplink optical burst from the second passive optical network, the method successively comprising: at a sub-layer of the transport layer of the reception stack, called the encapsulation level, a transmission of the data directly to a service layer of the transmission stack, without processing by sub-layers higher than the encapsulation level in the reception stack, successive processing in the transmission stack, by the service layer, by a transport layer and by a physical layer,a transmission of data in a second uplink optical burst to the first passive optical network.,

[0042] In the upstream direction, in the OLT of the second PON, unlike the prior art, the processing relating to sub-layers of the transport layer is omitted. This processing will be carried out further upstream at the level of the OLT of the first PON. This lightens the equipment hosting the second OLT, which is particularly advantageous in the case where this equipment is located at a customer of the operator of the first PON. In addition, since an ONU of the first PON is already located in the same place, this lightening facilitates the integration of the second OLT with the ONU of the first PON in a single FGW hardware device (for Fiber Gateway), which can be an optical network gateway, such as for example a modified home or professional Internet access gateway.

[0043] The choice of sub-layers that are not decapsulated in the upstream direction is made based on a division of the protocol stack that determines the part of this stack that is functionally deported from the second PON to the OLT of the first PON. As a result, the division determines a complementary link between the first and second OLTs. The division in the upstream direction may differ from the division in the downstream direction. There may also be a division in only one of the two transmission directions.

[0044] For convenience in this document, the term "decapsulation" generally refers to any processing performed in the transport layer on data after processing by the physical layer, i.e. in the direction of ascending the protocol stack, from the so-called lower layers to the so-called upper layers. Transport layer processing in the upstream direction includes, for example, depending on the sub-layer concerned, descrambling, recovery of OAM information ("PLOAM parsing"), decryption, reassembly, etc. It should be noted that in the context of PONs, the term "optical burst" is used for the upstream direction, rather than the term "optical signal", which is reserved for the downstream direction.

[0045] According to one aspect, the uplink transmission method comprises, at the encapsulation level, before transmission of the data to the service layer of the transmission stack, formatting the data into an Ethernet frame and inserting information indicative of the encapsulation into the Ethernet frame.

[0046] Thus, the fact that processing related to sub-layers of the transport layer is omitted is transmitted as information in a field of the Ethernet frames. It will be easy for the OLT of the first PON to distinguish these Ethernet frames from Ethernet frames coming from an ONU of the first PON, which do not have this characteristic.

[0047] Optionally, information indicative of the encapsulation level can also be inserted into Ethernet frames.

[0048] The invention also relates to a method for receiving data in an uplink optical burst, implemented in a first optical line terminal of a first passive optical network, the data being received at a physical layer, then processed successively and completely by the physical layer and by a transport layer, the method comprising, at a service layer, a detection of missing processing of the data, relating to at least one sub-layer of the transport layer, above a level called the encapsulation level, at the service layer, a processing of the data relating to sub-layers of the transport layer above the encapsulation level, to obtain a data frame.

[0049] The missing processing according to the sub-layer(s) of the transport layer is not performed in the OLT of the second PON but is deported to the OLT of the first PON. After complete processing of the frame by the transport layer, i.e. after its complete decapsulation, it is transmitted to the service layer, which checks the presence or absence of an additional encapsulation, in other words a second recursive encapsulation in the first encapsulation.

[0050] If there is additional encapsulation, this means that the frame is coming from the second PON and the OLT needs to finish decapsulating the frame. If there is no additional encapsulation, this means that the frame is coming from the first PON and its transport layer processing is completely finished.

[0051] In one aspect of the receiving process, missing processing detection involves verifying that the data is not in an Ethernet or OMCI format.

[0052] A first way to detect that processing is missing is to check the format in which the data is delivered by the transport layer. In fact, according to the prior art, the data expected by the service layer must be in Ethernet or OMCI (ONU Management and Control Interface) format. If they are not in Ethernet or OMCI format, this means that their processing is not complete.

[0053] According to one aspect of the receiving method, the detection of missing processing consists of verifying that Ethernet frames containing the data include information indicative of an encapsulation.

[0054] A second way to detect that a processing is missing is based on a prior formatting of the data into Ethernet frames, carried out upstream in the OLT of the second PON, at the encapsulation level. In addition to Ethernet formatting, the OLT of the second PON inserts in a specific field of each Ethernet frame information indicating the presence of encapsulation, and optionally information indicating the encapsulation level. Thus, when the OLT of the first PON receives the data at the output of its transport layer, they are all in the form of Ethernet frames (or OMCI messages), whether they originate from the first or the second PON. Data frames coming from an ONU of the first PON and not coming from the second PON do not include the information indicating encapsulation, i.e. indicative of a missing processing.It is therefore possible to distinguish these data frames from data frames coming from an ONU of the second PON, which include in a field the information indicative of missing processing.

[0055] According to one aspect of the receiving method, the detected missing processing relates to all sub-layers of the transport layer.

[0056] In other words, according to this aspect, the first OLT decapsulates the entire transport layer of the frame twice: a first time, following the passage of the frame in an optical burst through the first PON, then a second time, to compensate for the absence of decapsulation after its passage in a previous optical burst, through the second PON.

[0057] So, when the upstream cut is exactly between the physical layer and the transport layer, the OLT of the first PON performs all the transport layer processing, which the OLT of the second PON no longer has to perform.

[0058] This minimizes the processing that the second optical line terminal must perform for data frames coming from the ONU of the second PON.

[0059] According to one aspect, the reception method comprises, following the processing relating to the sub-layers above the encapsulation level: at the service layer level, another detection of processing missing from the data, relating to at least one sub-layer of the transport layer, above another level called other encapsulation level, at the service layer level, another processing of the data relating to sub-layers of the transport layer above the other encapsulation level, to obtain a data frame.

[0060] Thus, if more than 2 PONs are arranged in cascade, i.e. if the second ONU of the second PON is connected to a third OLT at the root of a third PON, this third OLT can also save processing at the service and transport layers, according to a division of the sub-layers of the transport layer, which can be different from one PON stage to another.

[0061] The invention also relates to a device for uplink data transmission, at the border between a first passive optical network and a second passive optical network, comprising a reception protocol stack and a transmission protocol stack, the data being received at a physical layer of the reception stack in a first uplink optical burst from the second passive optical network, the device comprising receivers, transmitters, a processor and a memory coupled to the processor with instructions intended to be executed by the processor for:at a sub-layer of the transport layer of the reception stack, called the encapsulation level, a transmission of the data to a service layer of the transmission stack, without processing by sub-layers higher than the encapsulation level in the reception stack,successive processing in the transmission stack, by the service layer,by a transport layer and by a physical layer, a transmission of data in a second uplink optical burst to the first passive optical network.,

[0062] This device, capable of implementing in all its embodiments the uplink transmission method which has just been described, is intended to be implemented in an optical network gateway, such as for example a "fiber" gateway for access to the Internet, domestic or professional.

[0063] The invention also relates to a device for receiving data in an uplink optical burst, included in a first optical line terminal of a first passive optical network, the data being received at a physical layer, then processed successively and completely by the physical layer and by a transport layer, the device comprising receivers, transmitters, a processor and a memory coupled to the processor with instructions intended to be executed by the processor for:at a service layer, a detection of missing processing of the data, relating to at least one sub-layer of the transport layer, above a level called the encapsulation level,at the service layer, a processing of the data relating to sub-layers of the transport layer above the encapsulation level, to obtain a data frame.

[0064] This device, capable of implementing in all its embodiments the reception method which has just been described, is intended to be implemented in an optical line terminal serving optical network units through a first passive optical network, at least one of which is connected to another optical network terminal serving other optical network units through a second passive optical network.

[0065] According to one aspect, the receiving device further comprises a first unit for managing configurations, faults, performances, and security of the first passive optical network, and a second unit for managing configurations, faults, performances, and security of the second passive optical network.

[0066] When two passive optical networks are cascaded, according to the invention and unlike the prior art, it is the optical line terminal of the first passive optical network that manages the configurations, faults, performances, and security of the passive optical networks of each stage of the cascade. The relocation of this function to the first optical line terminal thus relieves the optical line terminals of the second stage of the cascade, while allowing synchronized and harmonized management of the OMCI (ONU Management and Control Interface) messages circulating in all the passive optical networks of the cascade.

[0067] According to one aspect, the receiving device further comprises a first unit for managing the upstream bandwidth allocation of the first passive optical network, and a second unit for managing the upstream bandwidth allocation of the second passive optical network.

[0068] When two passive optical networks are cascaded, according to the invention and unlike the prior art, it is the optical line terminal of the first passive optical network which manages the allocation of upstream bandwidth of the passive optical networks of each stage of the cascade. The transfer of this function to the first optical line terminal thus relieves the optical line terminals of the second stage of the cascade, while allowing synchronized and harmonized management of all the passive optical networks of the cascade.

[0069] The invention also relates to a system of cascaded passive optical networks for receiving uplink data, comprising a receiving device such as that which has just been described, connected to a plurality of uplink transmission devices such as that which has just been described, through the first passive optical network, at least one such uplink transmission device being connected to a plurality of optical network units through a second passive optical.

[0070] The invention also relates to a computer program comprising instructions which, when these instructions are executed by a processor, cause the latter to implement the steps of the uplink transmission method, which has just been described.

[0071] The invention also relates to an information medium readable for example by a fiber gateway for Internet access, and comprising instructions of a computer program as mentioned above.

[0072] The invention also relates to a computer program comprising instructions which, when these instructions are executed by a processor, cause the latter to implement the steps of the reception method, which has just been described.

[0073] The invention also relates to an information medium readable by an optical network terminal, and comprising instructions of a computer program as mentioned above.

[0074] The above-mentioned programs may use any programming language, and may be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other desirable form.

[0075] The above-mentioned information carriers may be any entity or device capable of storing the program. For example, a carrier may include a storage medium, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording medium.

[0076] Such a storage medium may, for example, be a hard disk, a flash memory, etc. On the other hand, an information carrier may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. A program according to the invention may in particular be downloaded from a network such as the Internet.

[0077] Alternatively, an information carrier may be an integrated circuit in which a program is incorporated, the circuit being adapted to perform or to be used in performing the methods in question. 4. Presentation of figures

[0078] Other advantages and characteristics of the invention will appear more clearly on reading the following description of some particular embodiments of the invention, given as simple illustrative and non-limiting examples, and the appended drawings, among which:

[0079] Schematically presents two passive optical networks connected in cascade, according to the prior art,

[0080] Schematically presents two passive optical networks connected in cascade, according to a first aspect of the invention,

[0081] Schematically presents two passive optical networks connected in cascade, according to a second aspect of the invention,

[0082] Presents an example structure of an optical network terminal, implementing the method of transmitting data in a downlink optical signal, and the method of receiving data in an uplink optical burst, according to aspects of the invention,

[0083] The present invention presents an example structure of an optical network gateway, implementing the method of transmitting data in a downlink optical signal, and the method of transmitting data in an uplink optical burst, according to aspects of the invention.

[0084] 5. Detailed description of at least one embodiment of the invention

[0085] PON technologies are based on a specific protocol stack, required to manage the specific PON (point-to-multipoint) topology, allowing for transparent encapsulation and decapsulation of conventional Ethernet frames. ITU PON technologies, for example, use the TC (Transmission Convergence) layer, which has several functions performed in series, including the encapsulation of data or management streams in GEM (Gigabit-capable passive optical network Encapsulation Method) frames, then GTC (Gigabit-capable passive optical network Transmission Convergence), which are then encoded and scrambled. Since GEM and GTC are related to G-PON technology, other PON technologies (XGS-PON, HS-PON, etc.) have similar functions with other names. Headers in these frames are used to manage the "routing" of frames and the priorities associated with services.The resulting binary sequence is transposed into the analog (electrical) domain and is used to modulate the optical signal that carries the information. The optical signal is then received, and the received binary sequence is in turn "unscrambled", decoded, and deencapsulated. The frame headers that carry the routing information then allow traffic to be directed to the correct destination with the associated priority.

[0086] The protocol stack is traversed in both directions of transmission (from the OLT to the ONU for downstream traffic, and vice versa for upstream traffic).

[0087] The different layers and sub-layers of the ITU standardized protocol stack are summarized in the following table (top layers first):SDU layerL3TC layerService AdaptationFrame Fragmentation / AssemblyL2TC layerService AdaptationEthernet - GEML2TC layerService AdaptationOMCI - GEML2TC layerService AdaptationGEM Encryption / DecryptionL2TC layerService AdaptationGEM - GTCL2TC layerFramingOAM Embedding / ParsingL2TC layerFramingPLOAM Embedding / ParsingL2TC layerPHY AdaptationFEC Encaps / DecapsL2TC layerPHY AdaptationScrambling / DescramblingL2TC layerPHY AdaptationSynchro, DelineationL2PMD layerL1

[0088] This table is not exhaustive, and presents as an example some of the sub-layers of the TC layer for the case of a G-PON according to the ITU standard.

[0089] The different layers and sublayers of the IEEE standardized protocol stack are another example and are summarized in the following table (top layers first):Network layerLAN & CSMA / CD layersL3Data link layerMAC ClientL2Data link layerOAM (optional)L2Data link layerMULTIPOINT MAC CONTROL (MPCP)L2Data link layerMAC - MEDIA ACCESS CONTROLL2Physical layerRECONCILIATION sublayerL1Physical layerPHYSICAL CODING SUBLAYER (including optional Forward Error Correction)L1Physical layerPHYSICAL MEDIUM ATTACHMENT (PMA)L1Physical layerPMD layerL1

[0090] This table is not exhaustive, and presents as an example some of the layers and sub-layers for the case of a 10GE-PON according to the IEEE standard.

[0091] For simplicity in the rest of the document, whatever the protocol stack, as indicated in the tables above, the different layers and sub-layers are grouped into 3 groups of layers corresponding respectively to a physical layer noted L1, a transport layer noted L2 and a service layer noted L3. The layers of the ITU and IEEE standards have equivalent functions and the rest of the document is based on those of the ITU standard, for simplicity.

[0092] Illustrates two passive optical networks arranged in cascade, according to the prior art.

[0093] In the downstream direction, the data transmitted by an upstream transmitter arrives at the OLT denoted OLT1, for example in the form of Ethernet frames. The data of such an Ethernet frame Td are processed successively by the L3, L2 and L1 layers of the OLT1, then are transmitted in the form of a downstream optical signal, in the first-level PON denoted PON1, which serves a plurality of ONUs for example through an optical coupler, including the ONU denoted ONU1a, which receives the optical signal at the L1 layer. The optical signal received by the ONU1a is then processed successively by the L1, L2 and L3 layers. At the output of the L3 layer of the ONU1a, the Td frame is recovered and ready to be delivered to the second-level PON denoted PON2, if its final destination is served by the PON2.

[0094] If this is the case, the same processing as in OLT1 is then applied to the data of the Td frame by OLT2, which transmits the data in a second optical signal in PON2. Then this second optical signal transports the data of the Td frame in PON2 to a plurality of ONUs including the ONU denoted ONU2a, which applies the same processing to them as ONU1a. At the output of the L3 layer of ONU2a, the Td frame is recovered and can continue its progression towards its final destination.

[0095] In the upstream direction, the operations described above are performed in reverse for a Tm frame.

[0096] Schematically presents two passive optical networks connected in cascade, according to a first aspect of the invention.

[0097] This first aspect corresponds to a particular embodiment where the entire L3 layer and the entire L2 layer, i.e. the entire service layer and the entire transport layer, are transferred from the OLT2 to the OLT1, in both transmission directions.

[0098] In the downstream direction, when a Td frame arrives at the OLT1 at the L3 layer, the OLT1 checks the final destination of the Td frame. Two cases arise: either the final destination of the Td frame is served by the PON2 which is cascaded from the PON1, or it is not. In the latter case, the data of the Td frame undergoes the classic processing of the L3, L2 and L1 layers according to the prior art.

[0099] When data is transmitted by an OLT to ONUs (downstream direction), it is processed successively by the L3, L2 and L1 layers. The L3 layer processing corresponds, for example, to the routing of Ethernet frames or OMCI information to the L2 layer of the OLT. The L2 layer processing corresponds, for example, to the fragmentation of an Ethernet frame or OMCI information into GEM frames, their encryption, fragmentation into GTC frames, the loading of administration and management information to the OLT or ONUs, the scrambling of the frames and their synchronization before sending the electrical signal thus generated to the optical transmitter.The L1 layer processing corresponds, for example, to the emission of an optical signal from an electrical signal via an optical transmitter, to the propagation in the optical fiber, and to the detection of the optical signal by a photoreceiver which transforms the optical signal into an electrical signal.

[0100] OMCI information, or OMCI messages, are signaling frames exchanged between an OLT and the ONUs of the same PON, for managing configurations, faults, performance, and security of the PON system.

[0101] In the first case, on the other hand, that is, for example, if the final destination of the Td frame is the ONU2a served by the PON2, the L3 layer of the OLT1 is modified and, in addition to the L3 layer processing, the L3 layer of the OLT1 encapsulates the Td frame in the L2 layer, before delivering it to the L2 layer. The L2 layer of the OLT1 is not modified and encapsulates the Td frame again, then delivers it to the L1 layer, which is also not modified.

[0102] Then, the data of the Td frame are received in a first optical signal by the ONU1a, at the L1 layer. The optical signal is processed successively by the L1, L2 and L3 layers. At the output of the L3 layer of the ONU1a, the Td' frame which is recovered differs from the Td frame in that it has already undergone in anticipation the processing of the L2 layer of the OLT2. It is already "encapsulated" in the L2 layer, and it is ready to be delivered directly to the L1 layer of the modified OLT2 of the PON2, without processing at the L3 and L2 layers. The OLT2 is therefore lightened, because it can be devoid of the components necessary for processing the L2 and L3 layers.

[0103] The data of the Td' frame are then transmitted in a second optical signal in the PON2. This second optical signal carries the data of the Td' frame in the PON2 to a plurality of ONUs, including the ONU2a, which applies the same processing to them as the ONU1a. At the output of the L3 layer of the ONU2a, the frame that is recovered is the Td frame, and not the Td' frame. It should be noted, however, that the data of the two frames are the same, only their formats differ.

[0104] In the upstream direction, when a Tm frame arrives at the L3 layer of the ONU2a, it successively undergoes processing at the L3, L2, and L1 layers as in the prior art. The data in the Tm frame are then transmitted in a first optical burst going up the PON2 to the L1 layer of the OLT2, which is modified. Indeed, the Tm' frame delivered by the OLT2 in the upstream direction (as in the downstream direction, moreover) has not undergone any processing at the L2 and L3 layers. The ONU1a receiving the Tm' frame processes it successively at the L3, L2, and L1 layers as in the prior art, and transmits the data included in the frame in an optical burst towards the OLT1.

[0105] When a burst of data is received by an OLT from the ONUs (upstream direction), they are processed successively by the L1, L2 and L3 layers. The processing of the L1 layer corresponds, for example, to the conversion of the received optical signal into an electrical signal via an optical receiver, then electrically amplified.

[0106] The L2 layer processing corresponds, for example, to the "unscrambling" of the received binary sequence, to the extraction of administration and management information from the ONU, to the reconstruction of GEM frames from GTC frames, to the decryption of GEM frames, or to the assembly of GEM frames to reform SDU frames (composed of Ethernet frames or OMCI messages).

[0107] Layer 3 processing corresponds, for example, to the routing of Ethernet or OMCI frames to their destination, indicated by the "destination MAC" address in the case of an Ethernet frame, or to the OMCI management entity, in the second case.

[0108] The data of the Tm' frame are then transmitted in a second optical burst going up the PON1 to the L1 layer of the OLT1, which is also modified at its L3 layer. Indeed, in the OLT1, after having undergone the processing of the L1 and L2 layers as in the prior art, when the data of the Tm' frame are delivered to the L3 layer, the latter must determine whether they originate from the PON1 or the PON2 which is a cascade of the PON1.

[0109] This determination may be made, in a first mode of operation, by estimating that the shape of the frames does not correspond to the Ethernet frames or OMCI messages normally received at the L3 layer in the prior art, or when transmitted by the PON 1 only. The OLT1 then determines that the shape of the frames is abnormal, and estimates that this means that the frames originated from the PON2 and have not completed their processing.

[0110] In another embodiment, the Tm' frame which is delivered by the OLT2 in the upstream direction undergoes encapsulation in Ethernet frames at the OLT2 before reaching the ONU1a. The headers of these Ethernet frames make it possible to direct the Tm' frame to a module of the OLT1 in the L3 layer (illustrated in the by a rectangle denoted L2 in the rectangle denoted L3) carrying out the L2 layer processing not carried out by the OLT2, after having undergone the processing of the L1 and L2 layers of the OLT1.

[0111] In these two operating modes, the OLT1 therefore subjects the Tm' frames to the L2 layer processing in the upstream direction, which was not done by the OLT2, and outputs the Tm frame, not the Tm' frame. It should be noted, however, that the data in the Tm and Tm' frames are the same, only their formats differ.

[0112] Schematically presents two passive optical networks connected in cascade, according to a second aspect of the invention

[0113] This second aspect corresponds to a more general embodiment, where the L3 layer is entirely offset but not the L2 layer which is partially offset, from the OLT2 to the OLT1, and where the part of the L2 layer which is offset is different depending on the transmission direction.

[0114] In the downward direction, the set of sub-layers of the L2 layer that are offset is noted L2d', and the set of sub-layers of the L2 layer that are not offset is noted L2d.

[0115] For example, the L2d' layer includes the upper sub-layer of the ITU protocol stack called "Service Adaptation", and the L2d layer includes the lower layers of the ITU protocol stack called "Framing" and "PHY Adaptation". The split of the offset is therefore between the "Service Adaptation" and "Framing" sub-layers. In this example, for data in the downstream direction, the OLT2 of PON2, which is cascaded to PON1, does not perform the processing related to the "Service Adaptation" sub-layer. It is the OLT2 of PON1 that does this.

[0116] Compared to the treatments undergone by the downstream data of a Td frame described with reference to the, the differences are as follows:

[0117] In the OLT1 of the PON1, the L3 layer encapsulates the Td frame in the L2d' layer, before delivering it to the L2 layer.

[0118] In the OLT2 of the PON2 which is cascaded to the PON1, the Td' frame which is recovered from the ONU1a, is delivered directly to the L2d layer of the OLT2.

[0119] In the upward direction, the set of sub-layers of the L2 layer that are offset is noted L2m', and the set of sub-layers of the L2 layer that are not offset is noted L2m.

[0120] For example, the L2m layer includes the upper sub-layers of the ITU protocol stack called "Service Adaptation" and "Framing", and the L2m layer includes the lower layer of the ITU protocol stack called "PHY Adaptation". The split of the offset is therefore between the "Framing" and "PHY Adaptation" sub-layers. In this example, for data in the uplink direction, the OLT2 of PON2, which is cascaded to PON1, does not perform the processing related to the "Service Adaptation" and "Framing" sub-layers. It is the OLT2 of PON1 that does this.

[0121] Compared to the processing of the uplink data of a Tm frame described with reference to the, the differences are as follows:

[0122] In the OLT2 of the PON2 which is cascaded from the PON1, it is at the output of the L2m layer of the OLT2 that the Tm' frame is delivered directly to the L3 layer of the ONU1a.

[0123] In the OLT1 of the PON1, after processing the data of the Tm' frame by the L2 layer, the L3 layer performs the processing of the L2d' layer on this data a second time, and delivers the Tm frame at the output of the L3 layer.

[0124] It is understood that the advantages of this second embodiment are similar to those of the first embodiment: the OLT2 is lightened because it no longer has to carry out certain processing relating to the service layer and part of the transport layer.

[0125] In both cases, cascaded passive optical networks can use different data rates and use protocol stacks of different standards (ITU for one and IEEE for the other, for example).

[0126] The present invention presents an example structure of an optical network terminal, implementing the method of transmitting data in a downlink optical signal, and the method of receiving data in an uplink optical burst, according to aspects of the invention.

[0127] The device 100 may be included in, or be, an optical line terminal such as, for example, OLT1.

[0128] For example, the device 100 comprises a receiver 101 of downlink data frames Td, a transmitter 102 of uplink data frames Tm, a transmitter 103 of downlink optical data signal S(Td'), a receiver 104 of uplink optical data burst S(Tm'), a processing unit 130, equipped for example with a microprocessor µP, and controlled by a computer program 110, stored in a memory 120 and implementing the transmission and reception methods according to the invention. At initialization, the code instructions of the computer program 110 are for example loaded into a RAM memory, before being executed by the processor of the processing unit 130.

[0129] Such a memory 120, such a processor of the processing unit 130, are capable of, and configured for, in the downstream direction: at the level of the service layer (L3) in the downstream direction of the data, a processing of the data relating to at least one sub-layer (L2d') of the transport layer, called downward encapsulation, before transmission of the processed data to the transport layer (L2), optionally, at the level of the service layer in the downstream direction of the data, and prior to the downward encapsulation, another downward encapsulation relating to at least one sub-layer of the transport layer,

[0130] and for, in the upstream direction:at the service layer in the upstream direction of the data, a detection of a missing processing of the data, relating to at least one sub-layer (L2m') of the transport layer, above a level called the upstream encapsulation level,at the service layer in the upstream direction of the data, a processing of the data relating to the sub-layers (L2m') above the upstream encapsulation level, called upstream decapsulation, to obtain a data frame,optionally, at the service layer in the upstream direction of the data, as part of the detection of a missing processing of the data, either a verification that the data is not in an Ethernet or OMCI format, or a verification that Ethernet frames containing the data include information indicative of an encapsulation,optionally, at the service layer in the upstream direction of the data,and following the processing relating to the sub-layers above the uplink encapsulation level, detecting another processing missing from the data, relating to at least one sub-layer of the transport layer, above another level called another uplink encapsulation level, then carrying out another processing of the data relating to sub-layers of the transport layer above the other uplink encapsulation level, to obtain a data frame.,

[0131] The device 100 also comprises, at the service layer (L3): a unit 180 for transmitting the uplink frames Tm to the transmitter 102, and directing the downlink data frames Td from the receiver 101 to the transport layer or to the downlink encapsulation (L2d') depending on their destination, an OMCI1 unit for managing the configurations, faults, performances, and security of the PON1, an OMCI2 unit for managing the configurations, faults, performances, and security of the PON2 which is connected in cascade to the PON1, a unit 190 for directing the uplink data from the transport layer to the unit 180, the OMCI1 unit or the uplink decapsulation (L2m'), depending on the detection of a missing processing of the data, a DBA2 unit (for Dynamic Bandwidth Allocation) for manage the upstream bandwidth allocation of the PON2.

[0132] The device 100 also comprises, at the transport layer (L2): a DBA1 unit for managing the upstream bandwidth allocation of the PON1, with which the DBA2 unit coordinates.

[0133] The device 100 may be composed of two separate devices 100d and 100m (not shown), the device 100d comprising the components necessary for the downlink direction, and the device 100m comprising the components necessary for the uplink direction.

[0134] The present invention presents an example structure of an optical network gateway, implementing the method of transmitting data in a downlink optical signal, and the method of transmitting data in an uplink optical burst, according to aspects of the invention.

[0135] The device 200 may be included in, or be, an optical network gateway, i.e., a home or business Internet access gateway, combining ONU functionality and OLT functionality, such as, for example, the FGW gateway.

[0136] For example, the device 200 comprises a receiver 201 of an optical downlink data signal S(Td'), a transmitter 202 of an optical uplink data burst S(Tm'), a transmitter 203 of an optical downlink data signal S(Td), a receiver 204 of an optical uplink data burst S(Tm), a unit (ONU1a) implementing an ONU functionality, a unit (OLT2) implementing an OLT functionality. The device 200 also comprises a processing unit 230, equipped for example with a microprocessor µP, and controlled by a computer program 210, stored in a memory 220 and implementing the transmission methods according to the invention. At initialization, the code instructions of the computer program 210 are for example loaded into a RAM memory, before being executed by the processor of the processing unit 230.

[0137] Such a memory 220, such a processor of the processing unit 230, are capable of, and configured for, in the downstream direction: at the level of the service layer (L3) of the ONU1a unit and in the downstream direction of the data, a detection of an encapsulation of the data relative to at least one sub-layer (L2d') of the transport layer (L2), a transmission of the descending encapsulated data, from the ONU1a unit to the OLT2 unit, directly at a level (L2d) immediately lower than the at least one transport sub-layer, called the encapsulation level, without processing relative to the at least one transport sub-layer, at the level of the transport layer (L2) of the OLT2 unit, successive processing up to a physical layer (L1), from the encapsulation level, at the level of the physical layer (L1) of the OLT2 unit, a transmission of the processed data in a downlink optical data signal S(Td), to a passive optical network (PON2),

[0138] and for, in the upstream direction: at a sub-layer (L2m) of the transport layer (L2) of the OLT2 unit, called the encapsulation level, a transmission of the data (Tm') directly to a service layer (L3) of the ONU1a unit, without processing in the OLT2 unit by sub-layers higher than the encapsulation level, successive processing in the ONU1a unit, by the service layer (L3), by a transport layer (L2) and by a physical layer (L1), a transmission of the processed data in an upstream optical burst S(Tm') to a passive optical network (PON1), optionally, at the encapsulation level, before the transmission of the data (Tm') to the service layer (L3) of the ONU1a unit, a formatting of the data into an Ethernet frame and an insertion into the Ethernet frame of information indicative of the encapsulation.

[0139] The device 200 also comprises, at the service layer (L3) of the ONU1a unit: a unit 180 for transmitting the uplink data frames Tm' to the transmitter 202, and receiving the downlink data frames Td' from the receiver 201, an OMCI1 unit for managing the configurations, faults, performances, and security of the PON1 system.

[0140] In another embodiment not shown, the device 200 is separated into two distinct hardware entities. The first entity is a device 200a which comprises the ONU functionality, i.e. the elements 201, 202 and ONU1a of the device 200, in addition to a processing unit, equipped for example with a microprocessor µP, and driven by a computer program, stored in a memory.

[0141] The second entity is a device 200b which comprises the OLT functionality, i.e. the elements 203, 204 and OLT2 of the device 200, in addition to a processing unit, equipped for example with a microprocessor µP, and controlled by a computer program, stored in a memory.

[0142] In addition, each of the devices 200a and 200b has an interface at the service layer (L3) in order to exchange data frames between them, for example an Ethernet interface.

[0143] The device 200 (respectively each of the devices 200a and 200b), may be composed of two separate devices for the descending and ascending directions, 200d and 200m (respectively 200ad, 200bd, 200am, 200bm, not illustrated), the device 200d (respectively 200ad, 200bd) comprising the components necessary for the descending direction, and the device 200m (respectively 200am, 200bm) comprising the components necessary for the ascending direction.

[0144] The entities described and included in the devices described in relation to figures 4 and 5 may be hardware or software. These figures illustrate only one particular way, among several possible ones, of carrying out the method detailed above, in relation to the preceding figures. Indeed, the technique of the invention is carried out indifferently on a reprogrammable computing machine (a PC computer, a DSP processor or a microcontroller) executing a program comprising a sequence of instructions, or on a dedicated computing machine (for example a set of logic gates such as an FPGA or an ASIC, or any other hardware module).

[0145] In the case where the invention is implemented on a reprogrammable computing machine, the corresponding program (i.e. the sequence of instructions) may be stored in a removable storage medium (such as for example a USB key, 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.

Claims

Upstream data transmission method, implemented in equipment (FGW) at the boundary between a first passive optical network (PON1) and a second passive optical network (PON2) and comprising a receive protocol stack and a transmit protocol stack, the data (Tm) being received at the level of a physical layer (L1) of the receive stack in a first upstream optical burst from the second passive optical network (PON2), the method comprising successively: at the level of a sublayer (L2m) of the transport layer of the receive stack, called the encapsulation level, a transmission of the data (Tm') directly to a service layer (L3) of the transmit stack, without processing by sublayers higher than the encapsulation level in the receive stack, successive processing in the transmit stack, by the service layer (L3), by a transport layer (L2) and by a physical layer (L1),a data transmission (Tm') in a second up-progress optical burst towards the first passive optical array (PON1). Upstream transmission method according to claim 1, comprising at the encapsulation level, before the transmission of the data (Tm') to the service layer (L3) of the transmission stack, an Ethernet frame formatting of the data and an insertion into the Ethernet frame of an encapsulation indicator information. Method for receiving data in an upstream optical burst, implemented in a first optical line terminal (OLT1) of a first passive optical network (PON1), the data (Tm') being received at the level of a physical layer (L1), then processed successively and completely by the physical layer (L1) and by a transport layer (L2), the method comprising, at the level of a service layer (L3), a detection of missing processing of the data, relating to at least one sublayer (L2m) of the transport layer (L2), above a level called the encapsulation level, at the level of the service layer (L3), a processing of the data relating to sublayers (L2m') of the transport layer (L2) above the encapsulation level, to obtain a data frame (Tm). A receiving method according to claim 3, wherein the missing processing detection consists of verifying that the data is not in an Ethernet or OMCI format. A receiving method according to claim 3, wherein the missing processing detection consists of verifying that Ethernet frames containing data include information indicative of encapsulation. Reception method according to any one of claims 3 to 4, wherein the missing treatment detected relates to all sub-layers of the transport layer. A receiving method according to any one of claims 3 to 5, comprising, following the processing relating to the sublayers (L2m') above the encapsulation level: at the level of the service layer (L3), another detection of missing data processing, relating to at least one sublayer of the transport layer (L2), above another level called another encapsulation level, at the level of the service layer (L3), another data processing relating to sublayers of the transport layer (L2) above the other encapsulation level, to obtain a data frame. Upstream data transmission device (200), at the boundary between a first passive optical network (PON1) and a second passive optical network (PON2), comprising a receive protocol stack and a transmit protocol stack, the data (Tm) being received at a physical layer (L1) of the receive stack in a first upstream optical burst from the second passive optical network (PON2), the device comprising receivers (201, 204), transmitters (202, 203), a processor (230) and a memory (220) coupled to the processor with instructions intended to be executed by the processor for: at a sublayer (L2m) of the transport layer of the receive stack, called the encapsulation level, transmission of the data (Tm') to a service layer (L3) of the transmit stack, without processing by sublayers higher than the encapsulation level in the receive stack, successive processing in the stack broadcast,via the service layer (L3), a transport layer (L2) and a physical layer (L1), a data transmission (Tm') in a second uplink optical burst destined for the first passive optical network (PON1). Device (100) for receiving data in an upstream optical burst, included in a first optical line terminal (OLT1) of a first passive optical network (PON1), the data (Tm') being received at the level of a physical layer (L1), then processed successively and completely by the physical layer (L1) and by a transport layer (L2), the device comprising receivers (101, 104), transmitters (102, 103), a processor (130) and a memory (120) coupled to the processor with instructions intended to be executed by the processor for: at the level of a service layer (L3), a detection of missing processing of the data, relating to at least one sublayer (L2m) of the transport layer (L2), above a level called the encapsulation level, at the level of the service layer (L3), a processing of the data relating to sublayers (L2m') of the transport layer (L2) above the encapsulation level, to obtain a data frame (Tm). Receiving device(100) according to claim 9, further comprising a first unit (OMCI1) for managing configurations, faults, performance, and security of the first passive optical network (PON1), and a second unit (OMCI2) for managing configurations, faults, performance, and security of the second passive optical network (PON2). Receiving device(100) according to any one of claims 9 to 10, further comprising a first unit (DBA1) for managing the upstream bandwidth allocation of the first passive optical network (PON1), and a second unit (DBA2) for managing the upstream bandwidth allocation of the second passive optical network (PON2). Cascaded passive optical network system for uplink reception, comprising a receiving device (100) according to claim 9 connected to a plurality of uplink transmission devices (200) according to claim 8 through the first passive optical network (PON1), at least one uplink transmission device (200) being connected to a plurality of optical network units (ONU2a) through a second passive optical network (PON2). Computer program(210), comprising instructions which, when executed by a processor, cause the processor to carry out the steps of the upstream transmission method, according to claim 1. Computer program(110), comprising instructions which, when executed by a processor, cause the processor to carry out the steps of the receiving process, according to claim 3.

Images