Collision detector for VHSP / GPON coexistence with throughput flexibility
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- HUAWEI TECH CO LTD
- Filing Date
- 2024-11-14
- Publication Date
- 2026-05-21
Smart Images
Figure EP2024082316_21052026_PF_FP_ABST
Abstract
Description
[0001] COLLISION DETECTOR FOR VHSP / GPON COEXISTENCE WITH THROUGHPUT FLEXIBILITY
[0002] TECHNICAL FIELD
[0003] This disclosure relates to methods and devices for collision detection for VHSP / GPON.
[0004] BACKGROUND
[0005] After the advent of 50G Passive Optical Network, PON, 50G-PON, also named High Speed PON, HSP, including symmetric bitrate, research has been conducted into all possible ways to realize further increase on the bitrate, for example up to 200 Gb / s, in a subsequent standard, prospectively called Very High Speed PON, VHSP herein. Further considerations are dedicated to ensure the coexistence with legacy standards already deployed.
[0006] Among the potential technical solutions for higher bandwidths, for example beyond 50G-PON, there are two main groups: Intensity modulation with direct-detection, IMDD: following a multi-wavelength or other multi-variable (i.e. polarization) approach for achieving a total capacity of 200Gb / s and beyond.
[0007] Coherent technology: employing an intensity and phase modulated transmitter, Tx, with a full or simplified coherent receiver, Rx, for 200Gb / s and beyond.
[0008] Recommendations published until now are based on IMDD schemes since these seem the most cost-effective transceiver technologies. A natural option for the next step would be to consider IMDD. However, its feasibility seems constrained by various channel effects, in particular, chromatic dispersion, CD, and multi-path interference, MPI, an effect which is more pronounced in multi-level formats, would limit the possible fiber length, thus limiting the usability of IMDD schemes. The only format that seems to comply with legacy link budget classes (up to 35dB loss) and is less affected by MPI would be based on lOOGb / s non-retum to zero, NRZ, with one or two wavelengths (for achieving 200Gb / s). However, CD can limit the possible operating wavelength range to a region close to the zero-dispersion wavelength of standard single mode fiber, SSMF. Thus, a problem might appear when considering coexisting with previous technologies, since the wavelength band close to zero dispersion is occupied by the upstream, US, of GPON. Hence, the possible 200G-PON US and downstream, DS, bands overlap with legacy GPON US or option 2 of 50G-PON US.
[0009] Operators made large investments into the construction and implementation of optical distribution networks, ODN. Hence, one of their requirements for the different PON generations is that all of them can work in the same ODN. In other words, a key requirement for the generations after GPON and other legacy standards is their ability to coexist. This condition also helps for carrying out a step by step migration from one technology to the other.
[0010] For the three main recommendations published so far by the International Telecommunication Union Telecommunication Standardization Sector, ITU-T, (GPON, XG-PON and HSP), the way to ensure the coexistence between them is wavelength division multiplexing, WDM. Each generation works in a different band and by means of filters at the Optical Line Terminal, OLT, and at the Optical Network Unit, ONU, they are separated and processed independently (Fig. 1).
[0011] In contrast and for example, the Institute of Electrical and Electronics Engineers, IEEE, recommendations EPON and 10G-EPON require an additional system to coexist. While the DS is well separated and can be transmitted and detected independently, the 10G-EPON US overlaps with the working EPON US band. EPON US is defined from 1260nm to 1360nm, i.e. the whole O-Band. For 10G-EPON to benefit from using negative CD and positive chirp, some overlap is accepted. To avoid collisions, time-division multiple access, TDMA, between EPON and 10G-EPON is defined in the IEEE 802.3av standard in Annex 75A. The detection can be done either optically or electrically (Fig. 2). In the first case, a 3dB optical coupler separates the optical signal and then one photodiode, PD, detects 10G-EPON and another one GPON. Afterwards, the OLT receives the bits from the path that carries the data. In the second case, a single PD detects the optical signal which then passes through a burst-mode transimpedance amplifier, HA, that can work with either EPON or 10G-EPON, which are selected depending on the incoming signal bitrate.
[0012] Currently, there is no technical definition for successor standards such as VHSP However, especially when IMDD is used, finding a solution for coexistence with GPON will be necessary since GPON or other legacy standard operating wavelengths will overlap with the operating wavelengths of VHSP or other successor standards.
[0013] At present, TDMA is always employed in case the operating wavelengths overlay as in the case of EPON and 10G-EPON. The main disadvantage is that the channel always has to be shared between the two technologies. In the case of EPON and 10G-EPON US, this means that even if a system is 10 times faster than the other, it still has to compete for the channel with units that work at 1 / 10 of its capacity. If the same scheme is employed for 200G-PON and GPON, users working at 200G will have to share the channel with terminals working at -1 / 100 of their capacity. This situation can influence the quality and overall experience of 200G-PON users. Furthermore, in the case of EPON and 10G-EPON US, the overlap band is of 20 nm which corresponds to 1 / 5 of the total band of EPON. In other words, the probability that a 10G-EPON user collides with a GPON user is reduced. Even if they could be detected simultaneously, they are not detected and always follow a TDMA approach to avoid collisions.
[0014] SUMMARY
[0015] The present disclosure relates to methods and devices for collision detection for VHSP / GPON.
[0016] The present disclosure is defined by the scope of the independent claims. The dependent claims provide advantageous embodiments of the present disclosure.
[0017] The solution proposed in this disclosure solves the deficiencies mentioned above by providing a collision detection mechanism and devices, wherein TDMA is (only) applied as a last result. It thereby avoids a waste of channel capacity and allows for more efficient communication while at the same time ensuring backwards compatibility with existing standards and thus promoting cost-efficiency.
[0018] The present disclosure provides in a first aspect a method for multi-standard coexistence in a passive optical network, comprising:
[0019] a first passive optical network standard with a first optical bandwidth;
[0020] a second passive optical network standard with a second optical bandwidth, wherein the first and second optical bandwidth overlap at least in a portion of the first optical bandwidth and the second optical bandwidth;
[0021] providing a collision avoidance mechanism comprising a first stage, a second stage, a third stage and a fourth stage: determining, in the first stage if there is a potential or actual collision, wherein the potential or actual collision is an event in which two or more optical transceivers transmit a first signal according to the first passive optical network standard and a second signal according to the second passive optical network standard in an overlapping wavelength interval, if the potential or actual collision is determined in the first stage, determining, in the second stage, if the potential or actual collision is out of band, and if the potential or actual collision is out of band, applying at least one of the following: a band spacing, a line-code change, a reduction of throughput or a wavelength shift to at least one of the first signal or the second signal; determining, in the third stage, if the potential or actual collision has been avoided in the second stage or if the potential or actual collision is in band and if the potential or actual collision has not been avoided in the second stage or the potential or actual collision is in band, applying time division multiple access to the first signal and the second signal in the fourth stage. This method design allows for a flexible multi-stage approach that conserves bandwidth compared to a traditional approach using (only) TDMA. It is compatible with legacy systems and provides a cost-effective and efficient solution for implementing high speed PON standards with a bandwidth overlap with legacy PON standards.
[0022] According to an implementation of the method of the first aspect, the method may further comprise: the first passive optical network standard is Gigabit Passive Optical Network, GPON, or Ethernet Passive Optical Network, EPON, and wherein the second passive optical network standard is a very high speed passive optical network standard. Very high speed passive optical network standard or VHSP in this sense encompasses any network standard that shares a wavelength overlap with GPON or EPON and provides advanced network capabilities, especially higher data transmission speed.
[0023] According to an implementation of the method of the first aspect, the method may further comprise: at least one of an upstream or a downstream operating band of the very high speed passive optical network standard overlaps with a GPON upstream operating band and wherein the method is performed at an optical line terminal.
[0024] According to an implementation of the method of the first aspect, determining, in the first stage, if there is a potential or actual collision, in the method may further comprise:
[0025] correlating a result of the determining of the potential or actual collision with information of the transceivers in the passive optical network, wherein the information is information about a scheduling mechanism of a medium access control layer of the first passive optical network standard and the second passive optical network standard. Accordingly, a medium access control, MAC, layer information is included in the process of determining a potential or actual collision, improving the efficiency of the method.
[0026] According to an implementation of the method of the first aspect, the collision detection mechanism of the method may further comprise: dividing, by an optical splitter, the first signal and the second signal into a first splitter output signal and a second splitter output signal.
[0027] According to an implementation of the method of the first aspect, the collision detection mechanism of the method may further comprise: filtering, by a first optical filter and a second optical filter, the first splitter output signal and the second splitter output signal, wherein the first optical filter is applied to the first splitter output signal to provide a first filter output signal and the second optical filter is applied to the second splitter output signal to provide a second filter output signal and wherein the first optical filter is set to the first optical bandwidth and the second optical filter is set to the second optical bandwidth. Each signal received from the splitter is filtered so that the signal is preserved in a wavelength portion of interest. The wavelength portion of interest may be delineated into wavelength portions with and without overlap, i. e. wavelength portions with and without potential or actual collisions, improving detectability and separability of signal. They may also be delineated into wavelength portions encompassing the full spectrum of first passive optical network standard and the second passive optical network standard, respectively.
[0028] According to an implementation of the method of the first aspect, the method may further comprise: the optical splitter is a 3 dB splitter or an X: Y splitter, wherein X refers to the second splitter output signal and wherein X > Y. A 3 dB splitter is also known as a 50:50 splitter and divides an incoming light beam into two equal parts. The beam may be divided into either equal parts or unequal parts.
[0029] According to an implementation of the method of the first aspect, the collision detection mechanism of the method may further comprise: amplifying at least one of the first splitter output signal or the second splitter output signal or the first signal and the second signal by an optical amplifier before or after the optical splitter. According to an implementation of the method of the first aspect, the collision detection mechanism of the method may further comprise:
[0030] detecting, by a first photodiode, the first filter output signal and, by a second photodiode, the second filter output signal, respectively;
[0031] digitally processing the first filter output signal;
[0032] digitally processing the second filter output signal; and
[0033] comparing the second filter output signal to the first filter output signal to determine if a first signal also appears in the second filter output signal, and thereby determining if the potential or actual collision is detected.
[0034] An amplifier is used, and, for example, depending on whether a 3 dB splitter or an unequal splitter is used, the amplifier can be implemented in several positions, namely before the splitter, after the splitter or the unequal divider, preferably but not obligatorily on the side where the weaker signal is transmitted. One beam may include the whole spectral range of a first passive optical network standard, for example GPON, whereas the other beam may include only the portion of the spectrum of the first passive optical network standard wherein it overlaps with the second passive optical network. This design allows for superior flexibility and cost-efficient implementation.
[0035] According to an implementation of the method of the first aspect, the collision detection mechanism of the method may further comprise:
[0036] filtering the first signal and the second signal by a high order optical filter with passbands such that the first filter output signal comprises a portion of the first optical bandwidth in which the first optical bandwidth does not overlap with the second optical bandwidth and the second filter output signal comprises the second optical bandwidth;
[0037] detecting, by a first photodiode, the first filter output signal and, by a second photodiode, the second filter output signal, respectively;
[0038] digitally processing the first filter output signal;
[0039] digitally processing the second filter output signal ; and
[0040] wherein determining, in the first stage if there is a potential or actual collision, comprises:
[0041] determining whether the first photodiode detects the first filter output signal or the second photodiode detects the second filter output signal and if the first photodiode detects the first filter output signal, determine that there is the potential or actual collision.
[0042] A filter, for example a Demux filter is used, in order to divide incoming signals into a beam with potential or actual collisions and another beam with no potential or actual collisions, for example in a spectral range that only the first but not the second passive optical network standard occupies. This design allows for superior flexibility and cost-efficient implementation. The present disclosure provides in a second aspect a collision detector for multi-standard coexistence in passive optical networks, comprising:
[0043] an optical splitter configured to divide an incoming signal into a first splitter output signal and a second splitter output signal, wherein the incoming signal comprises a first signal according to a first passive optical network standard with a first optical bandwidth and a second signal according to a second passive optical network standard with a second optical bandwidth, wherein the first and second optical bandwidth overlap at least in a portion of the first optical bandwidth and the second optical bandwidth;
[0044] a first optical filter and a second optical filter, wherein the first optical filter is applied to the first splitter output signal to provide a first filter output signal and the second optical filter is applied to the second splitter output signal to provide a second filter output signal and wherein the first optical filter is set to only transmit the first optical bandwidth and the second optical filter is set to only transmit the second optical bandwidth;
[0045] a first detection device and a second detection device, wherein the first detection device is configured to detect the first filter output signal and wherein the second detection device is configured to detect the second filter output signal; and comparison means configured to compare the first filter output signal and the second filter output signal and determine if there is a potential or actual collision. Accordingly, filters after a splitter ensure that separate detection devices detect only signals in the first or second optical bandwidth according to the first or second passive optical network standard, respectively. This device design allows for a flexible collision detection approach that conserves bandwidth compared to a traditional approach using (only) TDMA. It is compatible with legacy systems and provides a cost-effective and efficient solutions for implementing high speed PON standards with a bandwidth overlap with legacy PON standards.
[0046] The present disclosure provides in a third aspect a collision detector for multi-standard coexistence in passive optical networks, comprising:
[0047] a high order optical filter with passbands configured to divide an incoming signal into a first filter output signal and a second filter output signal, wherein the incoming signal comprises a first signal according to a first passive optical network standard with a first optical bandwidth and a second signal according to a second passive optical network standard with a second optical bandwidth, wherein the first and second optical bandwidth overlap at least in a portion of the first optical bandwidth and the second optical bandwidth,
[0048] wherein the first filter output signal comprises a portion of the first optical bandwidth in which the first optical bandwidth does not overlap with the second optical bandwidth and the second filter output signal comprises the second optical bandwidth; a first detection device and a second detection device, wherein the first detection device is configured to detect the first filter output signal and wherein the second detection device is configured to detect the second filter output signal; and comparison means configured to determine if the first detection device detects the first filter output signal and if the first photodiode detects the first filter output signal, determine that there is a potential or actual collision.
[0049] Accordingly, a high order optical filter with passbands configured to divide an incoming signal, for example a Demux filter is used, in order to divide incoming signals into a beam with potential or actual collisions and another beam with no potential or actual collisions, for example in a spectral range that only the first but not the second passive optical network standard occupies. This device design allows for a flexible collision detection approach that conserves bandwidth compared to a traditional approach using (only) TDMA. It is compatible with legacy systems and provides a cost-effective and efficient solutions for implementing high speed PON standards with a bandwidth overlap with legacy PON standards.
[0050] The present disclosure provides in a fourth aspect an optical line terminal comprising the collision detector of the second or third aspect, wherein the optical line terminal is configured to identify the potential or actual collision if the collision detector determines the potential or actual collision, wherein the potential or actual collision is an event in which two or more optical transceivers simultaneously transmit the first signal and the second signal in the portion of the first optical bandwidth and the second optical bandwidth, in which the first and second optical bandwidth overlap.
[0051] The device of the second or third aspect can be implemented in an optical line terminal in order to improve the efficiency of a PON.
[0052] According to an implementation of the device of the fourth aspect, the optical line terminal is further configured to correlate a result of the determining of the potential or actual collision with the information of the transceivers in the passive optical network, wherein the information is information about a scheduling mechanism of a medium access control layer of the first passive optical network standard and the second passive optical network standard. Accordingly, a medium access control, MAC, layer information is comprised in the process of determining a potential or actual collision, improving the efficiency of the method.
[0053] According to an implementation of the device of the fourth aspect, the optical line terminal is further configured to avoid the potential or actual collision by determining if the potential or actual collision is out of band, and if the potential or actual collision is out of band, applying at least one of a band spacing, a line-code change, a reduction of throughput or a wavelength shift to the first signal or to the second signal, and, if the potential or actual collision cannot be avoided by applying at least one of a band spacing, a line-code change, a reduction of throughput or a wavelength shift to the first signal or to the second signal or if the collision is in band, applying time division multiple access. Accordingly, a further collision avoidance mechanism is provided that does not prematurely resort to TDMA, thus improving the efficiency of the device.
[0054] BRIEF DESCRIPTION OF DRAWINGS
[0055] In the following embodiments of the present disclosure are described in more detail with reference to the attached figures and drawings, in which:
[0056] Fig. 1 shows a triple coexistence scheme of GPON, XG-PON and HSPON with WDM.
[0057] Fig. 2 shows topologies for EPON and 10G-EPON operation with the split in the optical domain (left) and electrical domain (right) as described in IEEE 802.3av.
[0058] Fig. 3 shows a flowchart with regard to an exemplary collision detection method.
[0059] Fig. 4 shows an exemplary embodiment of a collision detector.
[0060] Fig. 5 shows a further implementation of an exemplary embodiment of a collision detector.
[0061] Fig. 6 shows a further exemplary embodiment of a collision detector.
[0062] DETAILED DESCRIPTION OF THE DRAWINGS
[0063] In the description of embodiments of this application, "and / or" describes an association relationship between associated objects and indicates that three relationships may exist. For example, A and / or B may indicate the following three cases: Only A exists, both A and B exist, and only B exists. In this application, "at least one" means one or more, and "a plurality of' means two or more. In addition, it should be understood that in description of this application, terms such as "first", "second", and "third" are merely used for distinguishing and description, but should not be understood as indicating or implying relative importance, or should not be understood as indicating or implying a sequence. Passive Optical Networks, PON: PON is a telecommunications technology that delivers broadband network access via optical fiber without electrical power in the distribution network. It uses a single optical fiber to serve multiple endpoints, allowing for high-speed data transmission.
[0064] Optical Distribution Network, ODN: ODN is the physical network structure of a passive optical network, comprising the fiber optic cables, splitters, and other components that link the central office to the subscribers.
[0065] Optical Line Terminal, OLT: OLT is the device located at the service provider's central office that communicates with optical network units, managing the data flow in a passive optical network and coordinating upstream and downstream signals. Optical Network Unit, ONU: ONU is a device at the end user's premises that connects to the optical line terminal and provides data, voice, and video services by converting optical signals into electrical signals.
[0066] Point-to-Point, PtP: PtP is a network topology where a direct link connects two nodes, typically providing dedicated bandwidth and low latency between the two points. Point-to-multi-Point, PtmP: PtmP is a network architecture where one central point is connected to multiple endpoints, commonly used in passive optical networks to serve multiple users through a single optical fiber.
[0067] Central Office, CO: CO refers to the facility where telecommunications providers house equipment like the optical line terminal, connecting to the optical distribution network and coordinating services for various endpoints.
[0068] Downstream, DS: DS denotes data transmission from the central office or network core toward the end user's location, generally delivering content such as video and internet.
[0069] Upstream, US: US is the data transmission direction from the end user back toward the network core, commonly carrying data such as user-generated content or requests.
[0070] Power Splitter, PS: A Power Splitter in a passive optical network, PON, is a crucial passive device that divides an incoming optical signal from a single input into multiple outputs, distributing the signal to various endpoints. This allows a single optical line terminal, OLT, to serve multiple users through one fiber, making PONs highly cost-effective. Power splitters vary in splitting ratios (e.g., 1x2, 1x4, 1x8, etc.), indicating the number of output channels generated. For instance, a 1x8 splitter divides the optical power equally among eight outputs, though the power decreases as the number of splits increases. Examples of power splitters that may optionally be used in the present disclosure but to which the disclosure is not limited to include Planar Lightwave Circuit, PLC, Splitters, which are highly compact and offer low insertion loss across all wavelengths, and Fused Biconic Taper, FBT, Splitters, which are cost-effective but better suited for specific wavelengths.
[0071] Media Access Control, MAC: The Media Access Control layer is a sublayer of the data link layer in network protocols responsible for regulating how devices access and share the network channel. In a shared network environment, like a PON, MAC plays a key role in preventing data collisions and managing the order in which multiple devices access the network. MAC layer protocols establish rules for device identification, transmission scheduling, and error detection. For instance, in Ethernetbased networks, the MAC protocol ensures that only one device transmits at a time, either by collision detection or collision avoidance.
[0072] Photo Diode, PD: PD is a semiconductor device that converts light into electrical current, essential for detecting and receiving optical signals in fiber-optic communications. For the purpose of this specification, any photo diode may optionally be an avalanche photo diode.
[0073] Avalanche Photo Diode, APD: APD is a highly sensitive photodiode that uses avalanche multiplication to amplify light signals, making it suitable for detecting low-intensity optical signals.
[0074] Single Mode Fiber, SMF: SMF is an optical fiber type that supports a single light mode, allowing long-distance, high-bandwidth communication with minimal dispersion and loss.
[0075] Time Division Multiple Access, TDMA: TDMA is a channel access method used to allow multiple users to share the same frequency channel by dividing the channel into time slots. In a PON, TDMA enables several Optical Network Units, ONUs, to share a single fiber by allocating specific time slots to each ONU. During its assigned slot, an ONU transmits its data, then pauses to allow the next ONU to transmit, creating a seamless, orderly flow of data between the OLT and multiple ONUs. TDMA is used in various telecommunications networks, including GSM cellular systems and digital broadcast systems. Insertion Loss, IL: IL is the amount of optical power lost when a signal passes through a component, such as a splitter or connector, and is typically measured in decibels (dB).
[0076] Optical Amplifier, OA: An Optical Amplifier is a device used in fiber-optic networks to boost the strength of an optical signal without converting it to an electrical signal. Amplifiers are essential in long-distance communications, as they maintain signal integrity and extend the transmission range. OA types which may be used in the disclosure herein but to which said disclosure is not limited include Erbium-Doped Fiber Amplifiers, EDFAs, or Semiconductor Optical Amplifiers, SOAs, which are compact and versatile, or Raman Amplifiers, which provide distributed amplification along the fiber length. Transmitter, Tx: Tx is the component that generates and sends optical signals in a fiber-optic network, typically converting electrical data into optical form for transmission.
[0077] Receiver, Rx: Rx is the component that detects and receives optical signals, converting them back into electrical signals for processing in a fiber-optic network.
[0078] Wavelength Division Multiplexing, WDM: WDM is an optical communication technology that allows multiple data streams to travel simultaneously on a single optical fiber by assigning each stream a different wavelength of light. By using multiple wavelengths, WDM significantly increases the fiber's capacity without laying additional cables. There are two main types: Coarse WDM, CWDM, which uses fewer, widely spaced wavelengths, ideal for short-distance and lower-cost implementations, and Dense WDM, DWDM, which utilizes closely spaced wavelengths to support high data rates and long-haul communications, typically used in large telecom networks. Any of these two WDM types may be used in the disclosure; however, the disclosure is not limited to either of them. WDM has become a backbone technology in high-capacity networks due to its scalability and efficiency.
[0079] Intensity Modulation with Direct-Detection, IMDD: IMDD is a fiber-optic communication method where information is transmitted by modulating the light signal's intensity. The receiver, typically using a photodetector, directly detects the intensity variations of the incoming light to interpret the data. This method is straightforward and cost-effective, as it doesn’t require complex coherent detection systems, making it suitable for short- to medium-distance fiber links. However, IMDD systems are more susceptible to noise and dispersion compared to coherent detection, which limits their effectiveness over longer distances and higher data rates.
[0080] Very High-Speed PON, VHSP: VHSP is a high-speed version of passive optical networks, designed to deliver significantly faster data transmission rates to meet the growing demand for bandwidth-intensive services. For the purposes of this specification, VHSP is a network standard that operates with a wavelength range overlapping with GPON or EPON and that provides advanced network capabilities, especially higher data transmission speed.
[0081] Gigabit Passive Optical Network, GPON: GPON is a PON technology that provides high-speed internet, voice, and video services, delivering data rates of up to 2.5 Gbps downstream and 1.25 Gbps upstream.
[0082] Ethernet Passive Optical Network, EPON: Ethernet Passive Optical Network, EPON), is a type of passive optical network that uses Ethernet-based protocols for data transmission, combining the simplicity and cost-efficiency of Ethernet with the highspeed, long-distance capabilities of fiber optics. EPON offers symmetric data rates (typically 1 Gbps) in upstream and downstream directions.
[0083] Potential or Actual Collision: In this specification, a potential or actual collision is defined as an event in which two or more optical transceivers transmit a first signal according to the first passive optical network standard and a second signal according to the second passive optical network standard in an overlapping wavelength interval. The number of transceivers is not specifically limited herein. Neither is the possibility of the transceivers to transmit signal according to the first passive optical network standard, the second passive optical network standard or another standard. Specifically and exemplary, the transceivers can both transmit at a bandwidth according to the second passive optical network standard and the second passive optical network standard.
[0084] Out of Band: Out of band refers to communication or signaling that occurs outside the primary data transmission channels or wavelengths used for delivering network traffic. Out-of-band signaling in PONs typically involves using a separate wavelength, frequency, or dedicated channel.
[0085] In Band: In the context of passive optical networks, PONs, in band refers to any communication or signaling that occurs within the same channel or wavelength range used for primary data transmission. Unlike out-of-band signaling, which uses separate wavelengths or channels, in-band communication transmits two or more signals over the same path. Band Spacing: Band spacing refers to the separation between optical wavelengths used in a PON for transmitting data across different channels. Adequate band spacing is critical in Wavelength Division Multiplexing, WDM, to prevent interference between channels and to maintain signal clarity. In a PON, this spacing ensures that downstream and upstream signals do not overlap or interfere, particularly as networks add more users or expand services. By carefully defining band spacing, PONs can support more data streams within the same fiber infrastructure, enhancing network capacity without sacrificing signal integrity. Line-Code Change: A line-code change in a PON context involves switching the encoding method used to convert data into a format suitable for optical transmission. Line coding is necessary to ensure data is accurately transmitted and received without error. Common line codes in PONs include Non-Retum-to-Zero, NRZ, and Retum-to-Zero, RZ, coding, each with specific attributes suited to different network requirements. Changing line code can improve data integrity, signal clarity, or compatibility with upgraded equipment or protocols, though it may impact network compatibility and throughput.
[0086] Reduction of Throughput: In a PON, reduction of throughput may be intentionally implemented as a response to a potential or actual collision between data signals or users. By deliberately lowering the data transmission rate, network congestion can be eased, giving each Optical Network Unit, ONU, more time to transmit and reducing the likelihood of overlapping transmissions in a shared medium. This controlled slowdown helps manage traffic flow, ensuring that critical data packets reach their destination with reduced risk of data loss or error due to collision. While users may experience temporarily reduced speeds, the method stabilizes network performance during high-collision risk situations.
[0087] Wavelength Shift: Wavelength shift can be intentionally applied in a PON to resolve or prevent collisions, for example via temperature changes, fiber strain, or equipment variation. When two signals risk overlapping in wavelength, shifting one signal’ s wavelength slightly out of its original range can create enough separation to prevent interference. This adjustment helps to reassign channels without extensive reconfiguration of the PON, effectively managing potential collisions and maintaining data integrity.
[0088] With regard to Figs. 1 and 2, existing issues with regard to the triple coexistence scheme of GPON, XG-PON and HSPON with WDM and topologies for EPON and 10G-EPON operation with the split in the optical domain (left) and electrical domain (right) as described in IEEE 802.3av are shown, as discussed in the background section.
[0089] With regard to Fig. 3 a first embodiment of the disclosure, a method for multi-standard coexistence in a passive optical network is provided. The method is employed in the context of a first passive optical network standard with a first optical bandwidth and a second passive optical network standard with a second optical bandwidth. The first and second optical bandwidth according to the first and second optical network standard, respectively, overlap at least in a portion of the first optical bandwidth and the second optical bandwidth.
[0090] In order to ensure the coexistence of the first and the second optical network standard in the passive optical network, a multi stage collision avoidance mechanism is provided.
[0091] The collision avoidance mechanism comprises a first stage, a second stage, a third stage and a fourth stage.
[0092] In the first stage S10, it is determined if there is a potential or actual collision. The potential or actual collision is an event in which two or more optical transceivers transmit a first signal according to the first passive optical network standard and a second signal according to the second passive optical network standard in an overlapping wavelength interval.
[0093] If the potential or actual collision is determined in the first stage, a second stage S20 follows in which it is determined if the potential or actual collision is out of band, and if this is the case, applying at least one of the following: a band spacing, a linecode change, a reduction of throughput or a wavelength shift to at least one of the first signal or the second signal.
[0094] In a third stage S30, it is determined if the potential or actual collision has been avoided in the second stage or if the potential or actual collision is in band. If the potential or actual collision has not been avoided in the second stage or the potential or actual collision is in band, time division multiple access, TDMA, is applied to the first signal and the second signal in a fourth stage S40.
[0095] The first passive optical network standard may optionally be a Gigabit Passive Optical Network, GPON, or Ethernet Passive Optical Network, EPON, standard. The second passive optical network standard may optionally be a very high speed passive optical network standard, VHSP, wherein VHSP operates with a wavelength range overlapping with GPON or EPON and that provides advanced network capabilities, especially higher data transmission speed.
[0096] Optionally, at least one of an upstream or a downstream operating band of the very high speed passive optical network standard overlaps with a GPON upstream operating band and the method is performed by a collision detector. The collision detector may be comprised by an optical line terminal, such that the method is performed at an optical line terminal.
[0097] Optionally, determining, in the first stage, if there is a potential or actual collision, may comprise correlating a result of the determining of the potential or actual collision with information of the transceivers in the passive optical network, wherein the information is information about a scheduling mechanism of a medium access control layer of the first passive optical network standard and the second passive optical network standard Sil.
[0098] Optionally, the first signal and the second signal into a first splitter output signal and a second splitter output signal may be divided by an optical splitter in the collision detection mechanism. The splitter may be configured to divide the incoming optical signals with precise power distribution ratios, depending on the network requirements. Optionally, the optical splitter is a 3 dB (50:50) splitter or an X:Y splitter, wherein X refers to the second splitter output signal and wherein X > Y. The optical splitter may be a Planar Lightwave Circuit, PLC, splitter or a Fused Biconic Taper, FBT, splitter, each offering distinct advantages in terms of wavelength compatibility and signal loss characteristics. In this setup, the first signal and second signal are divided into separate splitter output signals, with the first splitter output signal directed to one (set of) Optical Network Unit(s), ONU(s), and the second to another, ensuring efficient allocation of bandwidth and reducing signal interference. Additionally, the splitter may be an asymmetric splitter to optimize the distribution of optical power to each output channel, balancing signal strength and coverage for downstream transmission. Advanced configurations of the optical splitter may include integrated wavelength-selective filtering to support Wavelength Division Multiplexing, WDM, allowing the system to handle multiple data streams on distinct wavelengths simultaneously, enhancing network capacity without additional fiber.
[0099] In case a splitter is used, a first optical filter and a second optical filter may optionally filter the first splitter output signal and the second splitter output signal, wherein the first optical filter is applied to the first splitter output signal to provide a first filter output signal and the second optical filter is applied to the second splitter output signal to provide a second filter output signal and wherein the first optical filter is set to the first optical bandwidth and the second optical filter is set to the second optical bandwidth.
[0100] The collision detection mechanism may further comprise amplifying at least one of the first splitter output signal or the second splitter output signal or the first signal and the second signal by an optical amplifier before or after the optical splitter.
[0101] Additionally, the collision detection mechanism may optionally comprise detecting, by a first photodiode, the first filter output signal and, by a second photodiode, the second filter output signal, respectively. Further, the first filter output signal; and the second filter output signal may both be digitally processed and thereafter compared to each other to determine if a first signal also appears in the second filter output signal, and thereby determining if the potential or actual collision is detected.
[0102] In a different implementation of the first embodiment, the collision detection mechanism may optionally comprise filtering the first signal and the second signal by a high order optical filter with passbands such that the first filter output signal comprises a portion of the first optical bandwidth in which the first optical bandwidth does not overlap with the second optical bandwidth and the second filter output signal comprises the second optical bandwidth. As described with regard to the foregoing implementation, a first photodiode may detect the first filter output signal and a second photodiode may detect the second filter output signal, respectively and the first filter output signal and the second filter output signal may both be digitally processed. In this implementation, however determining, in the first stage, if there is a potential or actual collision, comprises determining whether the first photodiode detects the first filter output signal or the second photodiode detects the second filter output signal and if the first photodiode detects the first filter output signal, determine that there is the potential or actual collision, meaning that in this case detection by the first photodiode indicates a potential or actual collision.
[0103] Optionally, the collision avoidance mechanism can be applied at registration or at any point during the operation of the passive optical network or both, at registration and at any point during the operation of the passive optical network.
[0104] In a second embodiment, a collision detector for multi-standard coexistence in passive optical network is provided. Exemplary implementations are provided in Figs. 4 and 5.
[0105] The collision detector comprises an optical splitter configured to divide an incoming signal into a first splitter output signal and a second splitter output signal, wherein the incoming signal comprises a first signal according to a first passive optical network standard with a first optical bandwidth and a second signal according to a second passive optical network standard with a second optical bandwidth, wherein the first and second optical bandwidth overlap at least in a portion of the first optical bandwidth and the second optical bandwidth. The splitter may optionally be any splitter as described with regard to the first embodiment.
[0106] Further, the collision detector comprises a first optical filter and a second optical filter, wherein the first optical filter is applied to the first splitter output signal to provide a first filter output signal and the second optical filter is applied to the second splitter output signal to provide a second filter output signal and wherein the first optical filter is set to only transmit the first optical bandwidth and the second optical filter is set to only transmit the second optical bandwidth, wherein the first optical bandwidth is Y nm : Y nm + X nm, and the second optical bandwidth is Y nm : Z nm, wherein Y may optionally be 1290, X may optionally be any integer between 9 and 20, preferably 15, and Z may optionally be 1330 nm. Nanometer values shown in Fig. 4 and subsequent figures and / or mentioned here or later in the text are optional only and should not be construed as limiting. Further, the collision detector comprises a first detection device and a second detection device, which may optionally be photo diodes, wherein the first detection device is configured to detect the first filter output signal and wherein the second detection device is configured to detect the second filter output signal, wherein both signals or either signal may optionally be digitally processed by a digital signal processor, DSP. Even though Figs. 4 and 5 only show one DSP, two may be employed, one for each detection device.
[0107] Through comparison means of the collision detector, the first filter output signal and the second filter output signal may be compared and said comparison means may determine if there is a potential or actual collision.
[0108] Optionally, the collision detector includes one or more optical amplifiers as described with regard to the first embodiment which may be placed both, before and / or after the splitter.
[0109] As indicated in Figs. 4 and 5, the first passive optical network standard may optionally be a Gigabit Passive Optical Network, GPON, or Ethernet Passive Optical Network, EPON, standard. The second passive optical network standard may optionally be a very high speed passive optical network standard, VHSP, wherein VHSP operates with a wavelength range overlapping with GPON or EPON and that provides advanced network capabilities, especially higher data transmission speed. Network standards mentioned in Fig. 4 and subsequent figures and / or mentioned here or later in the text are optional only and should not be construed as limiting.
[0110] In a third embodiment, a further collision detector for multi-standard coexistence in passive optical network is provided. An exemplary implementation is provided in Fig. 6.
[0111] The collision detector comprises a high order optical filter with passbands configured to divide an incoming signal into a first filter output signal and a second filter output signal, wherein the incoming signal comprises a first signal according to a first passive optical network standard with a first optical bandwidth and a second signal according to a second passive optical network standard with a second optical bandwidth, wherein the first and second optical bandwidth overlap at least in a portion of the first optical bandwidth and the second optical bandwidth.
[0112] Therein, the first filter output signal comprises a portion of the first optical bandwidth in which the first optical bandwidth does not overlap with the second optical bandwidth and the second filter output signal comprises the second optical bandwidth, namely second filter output signal comprises a portion of the wavelength spectrum Y nm : Y nm + X nm, and the first filter output signal comprises a portion of the wavelength spectrum Y nm + X nm : Z nm, wherein Y may optionally be 1290, X may optionally be any integer between 10 and 20, preferably 15, and Z may optionally be 1330 nm.
[0113] Further, the collision detector comprises a first detection device and a second detection device, which may optionally be photo diodes, wherein the first detection device is configured to detect the first filter output signal and wherein the second detection device is configured to detect the second filter output signal, wherein both signals or either signal may optionally be digitally processed by a digital signal processor, DSP. Even though Fig. 6 only shows one DSP, two may be employed, one for each detection device.
[0114] Through comparison means of the collision detector, the collision detector may determine if the first detection device detects the first filter output signal and if the first photodiode detects the first filter output signal, it may determine that there is a potential or actual collision.
[0115] Optionally, the collision detector includes one or more optical amplifiers as described with regard to the first and second embodiment which may be placed both, before and / or after the splitter.
[0116] As indicated in Fig. 6, the first passive optical network standard may optionally be a Gigabit Passive Optical Network, GPON, or Ethernet Passive Optical Network, EPON, standard. The second passive optical network standard may optionally be a very high speed passive optical network standard, VHSP, wherein VHSP operates with a wavelength range overlapping with GPON or EPON and that provides advanced network capabilities, especially higher data transmission speed.
[0117] In a fourth embodiment, an optical line terminal comprising the collision detector of embodiments two or three is provided. The optical line terminal is configured to identify the potential or actual collision if the collision detector determines the potential or actual collision. As with regard to the first embodiment, a potential or actual collision is an event in which two or more optical transceivers simultaneously transmit the first signal and the second signal in the portion of the first optical bandwidth and the second optical bandwidth, in which the first and second optical bandwidth overlap.
[0118] Optionally, the optical line terminal may be further configured to correlate a result of the determining of the potential or actual collision with the information of the transceivers in the passive optical network, wherein the information is information about a scheduling mechanism of a medium access control layer of the first passive optical network standard and the second passive optical network standard, as described with regard to the first embodiment.
[0119] Further optionally, the optical line terminal may be further configured to avoid the potential or actual collision by determining if the potential or actual collision is out of band, and if the potential or actual collision is out of band, applying at least one of a band spacing, a line-code change, a reduction of throughput or a wavelength shift to the first signal or to the second signal, and, if the potential or actual collision cannot be avoided by applying at least one of a band spacing, a line-code change, a reduction of throughput or a wavelength shift to the first signal or to the second signal or if the collision is in band, applying time division multiple access, as described with regard to the first embodiment.
Claims
CLAIMS1. A method for multi-standard coexistence in a passive optical network, comprising:a first passive optical network standard with a first optical bandwidth;a second passive optical network standard with a second optical bandwidth, wherein the first and second optical bandwidth overlap at least in a portion of the first optical bandwidth and the second optical bandwidth;providing a collision avoidance mechanism comprising a first stage, a second stage, a third stage and a fourth stage: determining, in the first stage if there is a potential or actual collision (S10), wherein the potential or actual collision is an event in which two or more optical transceivers transmit a first signal according to the first passive optical network standard and a second signal according to the second passive optical network standard in an overlapping wavelength interval, if the potential or actual collision is determined in the first stage, determining, in the second stage, if the potential or actual collision is out of band (S20), and if the potential or actual collision is out of band, applying at least one of the following: a band spacing, a line-code change, a reduction of throughput or a wavelength shift to at least one of the first signal or the second signal;determining, in the third stage, if the potential or actual collision has been avoided in the second stage or if the potential or actual collision is in band and if the potential or actual collision has not been avoided in the second stage or the potential or actual collision is in band (S30), applying time division multiple access to the first signal and the second signal in the fourth stage (S40).
2. The method of claim 1, wherein the first passive optical network standard is Gigabit Passive Optical Network, GPON, or Ethernet Passive Optical Network, EPON, and wherein the second passive optical network standard is a very high speed passive optical network standard.
3. The method of claim 2, wherein at least one of an upstream or a downstream operating band of the very high speed passive optical network standard overlaps with a GPON upstream operating band and wherein the method is performed at an optical line terminal.
4. The method of any of claims 1 to 3, wherein determining, in the first stage, if there is a potential or actual collision, comprises: correlating a result of the determining of the potential or actual collision with information of the transceivers in the passive optical network, wherein the information is information about a scheduling mechanism of a medium access control layer of the first passive optical network standard and the second passive optical network standard (Si l).
5. The method of any of claims 1 to 4, wherein the collision detection mechanism comprises:dividing, by an optical splitter, the first signal and the second signal into a first splitter output signal and a second splitter output signal.
6. The method of claim 5, wherein the collision detection mechanism further comprises:filtering, by a first optical filter and a second optical filter, the first splitter output signal and the second splitter output signal, wherein the first optical filter is applied to the first splitter output signal to provide a first filter output signal and the second optical filter is applied to the second splitter output signal to provide a second filter output signal and wherein the first optical filter is set to the first optical bandwidth and the second optical filter is set to the second optical bandwidth.
7. The method of any of claims 5 or 6, wherein the optical splitter is a 3 dB splitter or an X: Y splitter, wherein X refers to the second splitter output signal and wherein X > Y.
8. The method of any of claims 5 to 7, wherein the collision detection mechanism comprises:amplifying at least one of the first splitter output signal or the second splitter output signal or the first signal and the second signal by an optical amplifier before or after the optical splitter.
9. The method of any of claims 5 to 8, wherein the collision detection mechanism comprises:detecting, by a first photodiode, the first filter output signal and, by a second photodiode, the second filter output signal, respectively;digitally processing the first filter output signal;digitally processing the second filter output signal ; andcomparing the second filter output signal to the first filter output signal to determine if a first signal also appears in the second filter output signal, and thereby determining if the potential or actual collision is detected.
10. The method according to any of claims 1 to 4, wherein the collision detection mechanism comprises:filtering the first signal and the second signal by a high order optical filter with passbands such that the first filter output signal comprises a portion of the first optical bandwidth in which the first optical bandwidth does not overlap with the second optical bandwidth and the second filter output signal comprises the second optical bandwidth;detecting, by a first photodiode, the first filter output signal and, by a second photodiode, the second filter output signal, respectively;digitally processing the first filter output signal;digitally processing the second filter output signal ; andwherein determining, in the first stage if there is a potential or actual collision, comprises:determining whether the first photodiode detects the first filter output signal or the second photodiode detects the second filter output signal and if the first photodiode detects the first filter output signal, determine that there is the potential or actual collision.
11. A collision detector for multi-standard coexistence in passive optical networks, comprising:an optical splitter configured to divide an incoming signal into a first splitter output signal and a second splitter output signal, wherein the incoming signal comprises a first signal according to a first passive optical network standard with a first opticalbandwidth and a second signal according to a second passive optical network standard with a second optical bandwidth, wherein the first and second optical bandwidth overlap at least in a portion of the first optical bandwidth and the second optical bandwidth;a first optical filter and a second optical filter, wherein the first optical filter is applied to the first splitter output signal to provide a first filter output signal and the second optical filter is applied to the second splitter output signal to provide a second filter output signal and wherein the first optical filter is set to only transmit the first optical bandwidth and the second optical filter is set to only transmit the second optical bandwidth;a first detection device and a second detection device, wherein the first detection device is configured to detect the first filter output signal and wherein the second detection device is configured to detect the second filter output signal; and comparison means configured to:compare the first filter output signal and the second filter output signal and determine if there is a potential or actual collision.
12. A collision detector for multi-standard coexistence in passive optical networks, comprising:a high order optical filter with passbands configured to divide an incoming signal into a first filter output signal and a second filter output signal, wherein the incoming signal comprises a first signal according to a first passive optical network standard with a first optical bandwidth and a second signal according to a second passive optical network standard with a second optical bandwidth, wherein the first and second optical bandwidth overlap at least in a portion of the first optical bandwidth and the second optical bandwidth,wherein the first filter output signal comprises a portion of the first optical bandwidth in which the first optical bandwidth does not overlap with the second optical bandwidth and the second filter output signal comprises the second optical bandwidth; a first detection device and a second detection device, wherein the first detection device is configured to detect the first filter output signal and wherein the second detection device is configured to detect the second filter output signal; and comparison means configured to:determine if the first detection device detects the first filter output signal and if the first photodiode detects the first filter output signal, determine that there is a potential or actual collision.
13. An optical line terminal comprising the collision detector of claim 11 or 12, wherein the optical line terminal is configured to identify the potential or actual collision if the collision detector determines the potential or actual collision, wherein the potential or actual collision is an event in which two or more optical transceivers simultaneously transmit the first signal and the second signal in the portion of the first optical bandwidth and the second optical bandwidth, in which the first and second optical bandwidth overlap.
14. The optical line terminal according to claim 13, wherein the optical line terminal is further configured to correlate a result of the determining of the potential or actual collision with the information of the transceivers in the passive optical network, wherein the information is information about a scheduling mechanism of a medium access control layer of the first passive optical network standard and the second passive optical network standard.1515. The optical line terminal according to claim 13 or 14, wherein the optical line terminal is further configured to avoid the potential or actual collision by determining if the potential or actual collision is out of band, and if the potential or actual collision is out of band, applying at least one of a band spacing, a line-code change, a reduction of throughput or a wavelength shift to the first signal or to the second signal, and, if the potential or actual collision cannot be avoided by applying at least one of a band spacing, a line-code change, a reduction of throughput or a wavelength shift to the first signal or to the second signal or if the collision is in band, applying time division multiple access.