KR101612909B1 - Passive optical network extending system having a function of recovering network and method thereof - Google Patents
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- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
- H04J14/0254—Optical medium access
- H04J14/0267—Optical signaling or routing
- H04J14/0268—Restoration of optical paths, e.g. p-cycles
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- H04B10/03—Arrangements for fault recovery
- H04B10/032—Arrangements for fault recovery using working and protection systems
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- H—ELECTRICITY
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- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/29—Repeaters
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- H—ELECTRICITY
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- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
- H04J14/0238—Wavelength allocation for communications one-to-many, e.g. multicasting wavelengths
- H04J14/0239—Wavelength allocation for communications one-to-many, e.g. multicasting wavelengths in WDM-PON sharing multiple downstream wavelengths for groups of optical network units [ONU], e.g. multicasting wavelengths
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- H04J14/0287—Protection in WDM systems
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- H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
- H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
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Abstract
The present invention relates to a passive optical network relay system and a line fault recovery method having a line failure recovery function that prevents a delay even when a fault is recovered through a preliminary line switching, the OLT can provide a continuous service even when the OLT does not perform the activation and registration process even if the physical line is changed while switching the line to the protecting line in case of working line failure, It is possible to prevent a communication error due to activation and registration process of several tens seconds to several minutes.
Description
The present invention relates to a passive optical network (PON) relay system and a line failure recovery method having a line failure recovery function, and more particularly, to a line failure recovery method and a line failure recovery method, And more particularly, to a passive optical network relay system and a line failure recovery method.
The passive optical network (PON) technology is configured to configure a high-speed subscriber network and can process simultaneous access of a plurality of subscribers through a time division scheme or a wavelength division scheme. Among these methods, a cost-effective time-sharing method is mainly used, and EPON (Ethernet PON) according to IEEE (Institute of Electrical and Electronics Engineers) 802.3av / ah, International Telecommunication Union-Telecommunication Standardization Sector (ITUT) G.984 / GPON (Gigabit PON) according to 7 is representative.
Such a PON is basically composed of one OLT (Optical Line Terminal) installed at the telephone company office, an ONT (Optical Network Terminal) of multiple subscribers, or a remote node (optical splitter) ) To point-to-multipoint network structure.
In the PON structure having such a structure, the transmission distance between the OLT of the telephone company and the subscriber's ONT is generally within about 20 km, and in the case of not a large city, And a method of extending the transmission distance by installing a telephone branch office in various places or installing a branch office branch is used.
FIG. 1 shows a configuration using a branch station to extend the transmission distance of the PON.
As shown in the figure, the
In this case, although the transmission distance is doubled, the economical efficiency is low because the cost of installing the
Another way to increase the transmission distance is to increase the signal output and decrease the reception sensitivity. In this case, the transmission distance can be extended, but there is a limit to increase the output and sensitivity of the optical transceiver, And the quality of the optical transceiver to be configured in the ONT of each subscriber must be increased, which leads to an increase in cost.
Another alternative is to use an optical repeater to amplify the transmitted optical signal, or to convert the received optical signal into an electrical signal and convert it back into an optical signal (OEO) A method using an optical repeater is used.
However, since the optical amplifier for amplifying the optical signal of the optical fiber which transmits a broadband optical signal as a whole is expensive, it is expensive, and the optical repeater is economical because it is relatively inexpensive and economical. However, Since the packet is damaged, it is difficult to apply it at gigabit class or higher.
Korean Patent Laid-Open No. 10-2011-0063034, "Relay device and relay method of gigabit passive optical network ", an optical signal transmitted through an optical repeater is converted into an electric signal, and the corresponding signal is modulated to analyze frame data In order to solve the delay problem occurring in the optical repeater by checking the control information for the uplink burst signal, restoring and modulating the uplink burst signal transmitted according to the control information, and then reconfiguring the uplink burst signal to the continuous signal. However, in such a case, in order to reconstruct the transmitted signal, it is necessary to construct an analysis of the entire frame signal to check the control information of the frame modulation and the upward burst signal. Therefore, a high performance FPGA or a dedicated ASIC , Resulting in an excessive computation load. Therefore, when the implementation is performed in such a manner, a high cost is incurred in the device configuration, and power consumption due to excessive computation for frame modulation and frame data analysis is significant, thereby increasing the operating cost.
Therefore, there is a growing demand for an optical repeater capable of extending the transmission distance while reducing the configuration cost and computation load.
On the other hand, since the PON has a network structure of 1: N, the number of subscribers, that is, ONTs, which one OLT occupies is basically several hundreds, and when ONU is used instead of ONT, one ONU is connected with dozens of subscribers, The OLT in charge of communication with many thousands of subscriber terminals. Therefore, if an abnormality occurs in the main optical line before the branching, communication to all subscribers is interrupted, so that it is required to quickly recover from such line abnormality. Particularly, if a repeater is constructed to extend the transmission distance, the risk of occurrence of a light beam failure increases because of a long optical path.
However, when using a general optical line redundancy structure, since the restart time is considerably long due to the characteristics of the PON, there is a limitation that it is difficult to recover quickly.
Therefore, we propose a new PON relay system that can extend the transmission distance of the PON with a transmission speed of Gigabit class or higher by using an inexpensive OEO optical repeater and to quickly recover the fault in the main line between the OLT and the optical repeater There is a growing demand for
In case of a PON having 1: N network structure, since one OLT communicates with a plurality of ONTs or ONUs, many subscribers may inconvenience when a failure occurs in the optical line directly connected to the OLT. Also, in a PON with a gigabit transmission speed or more, a delay for converting an optical signal into an electric signal, an electric signal into an optical signal, or a delay for detecting a clock from a burst signal can not be ignored. Therefore, the OEO optical repeater The signal delay factor due to additional optical / electrical conversion and electrical / optical conversion can be doubled.
SUMMARY OF THE INVENTION It is therefore an object of the present invention to solve the above problems and to provide an optical repeater which can reduce or prevent frame data loss due to signal conversion between the OLT and the ONT and clock recovery delay, A passive optical network relaying system having a line failure recovery function for real-time failure recovery by preventing a delay due to a switching while transferring the signal to a protecting line in case of a working line failure, And to provide a recovery method.
It is another object of the present invention to provide an OLT that includes a pair of optical transceivers and an optical transceiver of an optical repeater connected to an OLT, and each of the optical transceivers has a pair of reception units, and the transmission unit separates transmission signals through a splitter, In this case, it is possible to compare the signals transmitted through physically separated lines, calculate the delay information for the same signal, and use them to make the lines having physically different lengths electrically equal length. A passive optical network relay system and a line failure recovery method having a line failure recovery function for preventing a delay due to a line change by allowing the distance information used without activation and registration procedures to be used as they are, .
It is another object of the present invention to provide an OLT in which an upstream signal transmitted to an OLT through an optical repeater is provided as a clock of an OLT and simultaneously receive and compare upstream burst frame data received by an OLT through a duplexed line, It is possible to check the bit-by-bit delay information on the uplink frame data received through different lines and to store a part of the received signal through the buffer so that the uplink frame data received in line switching can be managed to be continuous at the bit level And to provide a passive optical network relay system and a line failure recovery method having a line failure recovery function capable of performing lossless line switching in units of bits.
It is another object of the present invention to provide an optical repeater which is configured such that a line between an OLT and an optical repeater is duplexed so as to be able to recover from a failure. In case of transmitting an upstream burst frame data to an OLT, And transmits the received actual burst frame data to the OLT so that the actual burst frame data is not damaged. When the uplink burst frame data is transmitted to the OLT, an interpolation signal is generated between the burst frame data, To the OLT, thereby preventing unnecessary delay and preventing the occurrence of frame data corruption. Thus, it is possible to apply the optical repeater for the OLT connection line failure recovery of the PON having the transmission speed of the gigabit or higher, complex A passive optical network relay system having an old function and a method of restoring a line fault.
A passive optical network relay system having a line failure recovery function according to an embodiment of the present invention uses a physically longer optical line as a working line among a pair of optical lines connected thereto, An OLT (Optical Line Terminal) having distance information on an ONT (Optical Network Terminal); OLT is connected to a pair of optical lines, and the delay for the same downlink signal simultaneously provided through them is calculated to calculate the delay information between the optical lines. Then, the delay calculated based on the transmission / And a photoelectric conversion optical repeater that allows the distance information provided in the OLT to be used as it is.
The OLT includes an optical transceiver having one transmitter for separating and outputting optical signals to a pair of optical lines and a pair of receivers for receiving optical signals received through a pair of optical lines, The repeater has an OLT-side optical transceiver having a transmitter for separating and outputting optical signals to a pair of optical lines connected to the OLT, and a pair of receivers for receiving optical signals received through the pair of optical lines .
The OLT includes an optical transceiver having one transmitter for outputting optical signals to a pair of optical lines and one receiver for receiving optical signals received through one of the pair of optical lines, Side optical transceiver having a pair of receiving portions for receiving optical signals received through a pair of optical lines and a pair of transmitting portions for selectively outputting only optical signals to be used to an optical line to be used, The OLT optical transceiver may further include a splitter unit which divides the optical signal into a pair of optical paths and provides the optical signal received through one of the pair of optical paths to the receiving unit of the OLT optical transceiver.
It is preferable that the photoelectric conversion optical repeater selects a line to be received later by checking the delay based on the same identifiable information among the downstream signals simultaneously transmitted from the OLT and received through each line.
The photoelectric conversion optical repeater transmits an upstream signal to the OLT using the OLT clock recovered from the downstream signal received from the OLT.
The OLT checks the inter-line delay information based on the identifiable bit data of the upstream frame data simultaneously transmitted from the photoelectric conversion optical repeater and received through each line, buffers the upstream frame data received through the spare line, A data transfer unit for providing data following the bits of the normally received uplink frame data through the pre-transfer operation line using the uplink frame data of the buffered spare line at the time of transfer, And a processing unit.
The photoelectric conversion optical repeater generates an uplink burst frame preamble prior to the clock and data restoration of the signal when the uplink burst signal is detected or predicted by the signal pattern, and outputs the generated uplink burst signal to the restored OLT clock in the downlink signal. When the uplink burst frame data is received through the clock and data restoration, all or a part of the received uplink burst frame data may be output to the determined clock following the uplink burst frame preamble generated and generated in advance.
As another example, the photoelectric conversion optical repeater receives and restores the upstream burst signal provided from the ONT, stores the reconstructed frame data in the asynchronous buffer using the reconstructed clock as an input clock, and outputs the OLT clock And outputs the frame data of the asynchronous buffer to the OLT. The interpolation signal including the identification information informing the start and end of the frame data in the interval between the frame data is included according to the OLT clock, And the OLT receives the uplink continuous signal generated by the continuous signal conversion repeater and received through the at least one optical repeater to recover the uplink data based on the local OLT clock, Identification information indicating the start and end of the frame data identified from the upstream data It may separate the frame data.
Another embodiment of the present invention is a method for restoring a line fault in a passive optical network relay system having a line failure recovery function in which an OLT and a photoelectric conversion optical repeater connected through a pair of optical lines are switched to a standby line in case of a line failure, Collecting the distance information of the ONT using a physically longer optical line as a working line among a pair of optical lines connected to the optical line; Confirming a delay between adjacent optical lines by confirming a delay for the same downstream signal simultaneously provided through a pair of optical lines connected to the OLT; When the line is switched, the photoelectric conversion optical repeater delays the upstream relay signal according to the confirmed delay information to provide the OLT with a physically shorter spare line of the pair of optical lines, and confirms the downlink relay signal received from the OLT And relaying the delayed signal to the ONT according to the delay information.
Checking the inter-line delay information based on the identifiable bit data among the upstream frame data simultaneously received from the photoelectric conversion optical repeater and received through the respective lines, and buffering the upstream frame data received through the preliminary line; And receiving the upstream frame data from the upstream frame data of the preliminary line buffered at the time of the line transfer successively from the bits following the bits of the upstream frame data normally received through the pre- .
A passive optical network relay system and a line fault recovery method having a line failure recovery function according to an embodiment of the present invention are configured to duplex a transmission line between an OLT and an optical repeater to switch to a protecting line in case of a working line failure Even if the physical line is changed, the OLT can provide a continuous service even when the activation and registration are not performed again. Thus, It is possible to prevent a communication failure.
In addition, the passive optical network relay system and the line failure recovery method having the line failure recovery function according to the embodiment of the present invention simultaneously receive the uplink burst frame data received in the OLT through the duplicated line, And the received signal is partially stored through the buffer. Thus, even when the line is switched, the received uplink frame data can be managed to be continuous at the bit level, so that the lossless line switching can be performed in units of bits. It has excellent effect.
In addition, a passive optical network relay system and a line failure recovery method having a line failure recovery function according to an embodiment of the present invention can prevent a signal damage that may occur in relaying gigabit-class PONs only at a signal level By using the photoelectric conversion optical relaying method, it is possible to extend the transmission distance even in the Gigabit class PON, and to effectively recover the optical path trouble built in the extended transmission section.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exemplary view showing an example of a transmission distance extension method of a conventional passive optical network.
2 is a conceptual diagram for explaining a downlink and uplink signal transmission method of a passive optical network;
3 is a block diagram illustrating a transmission delay component of a gigabit passive optical network.
4 is a signal diagram illustrating the transmission delay of a gigabit passive optical network.
5 is a view for explaining a transmission delay when an optical repeater is applied to a gigabit passive optical network.
6 is a system configuration diagram showing a configuration of a relay apparatus according to an embodiment of the present invention and a passive optical network configuration using the same.
FIG. 7 is a conceptual diagram for explaining a difference in delay time between the case of using the relay apparatus of FIG. 6 and the case of using the existing optical repeater.
8 is a view illustrating a relay system for extending a transmission distance of a passive optical network including a continuous signal conversion relay apparatus according to an embodiment of the present invention.
FIG. 9 is a conceptual diagram for explaining a configuration of an upward continuous signal according to an embodiment of the present invention; FIG.
10 is a block diagram illustrating a configuration of a continuous signal conversion repeater and an OLT capable of receiving upstream continuous signals according to an embodiment of the present invention.
11 is a conceptual diagram illustrating a transceiver output of an OLT capable of receiving an upstream continuous signal according to an embodiment of the present invention.
12 is a configuration example of a relay system for extending a transmission distance of a passive optical network according to an embodiment of the present invention.
13 is a configuration example of a passive optical network relaying system having a line failure recovery function according to an embodiment of the present invention.
14 is an example of a line redundant connection configuration according to an embodiment of the present invention.
15 is a configuration example of an OLT having a line failure recovery function according to an embodiment of the present invention.
16 is a conceptual diagram illustrating a recovery method in case of a line failure according to an embodiment of the present invention.
17 is a configuration example of a passive optical network relaying system having a line failure recovery function according to an embodiment of the present invention.
18 is an example of a line redundant connection configuration according to an embodiment of the present invention;
FIG. 19 is a flowchart for explaining a line failure recovery method according to an embodiment of the present invention; FIG.
It is noted that the technical terms used in the present invention are used only to describe specific embodiments and are not intended to limit the present invention. In addition, the technical terms used in the present invention should be construed in a sense generally understood by a person having ordinary skill in the art to which the present invention belongs, unless otherwise defined in the present invention, and an overly comprehensive It should not be construed as meaning or overly reduced. In addition, when a technical term used in the present invention is an erroneous technical term that does not accurately express the concept of the present invention, it should be understood that technical terms that can be understood by a person skilled in the art can be properly understood. In addition, the general terms used in the present invention should be interpreted according to a predefined or context, and should not be construed as being excessively reduced.
Furthermore, the singular expressions used in the present invention include plural expressions unless the context clearly dictates otherwise. The term "comprising" or "comprising" or the like in the present invention should not be construed as necessarily including the various elements or steps described in the invention, Or may include additional components or steps.
In addition, terms including ordinals such as first, second, etc. used in the present invention can be used to describe elements, but the elements should not be limited by terms. Terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals refer to like or similar elements throughout the several views, and redundant description thereof will be omitted.
In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. It is to be noted that the accompanying drawings are only for the purpose of facilitating understanding of the present invention, and should not be construed as limiting the scope of the present invention with reference to the accompanying drawings.
In particular, in describing the present invention, a subscriber's optical communication terminal is referred to as an ONT (Optical Network Terminal), but this is used to represent a subscriber's optical communication terminal including an ONU (Optical Network Unit) And other types of optical communication modems or optical communication terminal devices.
In addition, all the optical repeaters in the detailed description refer to photoelectric conversion optical repeaters. Since one or more optical repeaters may be constituted, the repeaters such as 'OLT side' and 'ONT side' Direction may be a direction corresponding to a connection configuration when connecting a plurality of optical repeaters.
In the case of applying a photoelectric conversion optical repeater for extending the transmission distance of a passive optical network (PON) having a gigabit transmission speed or more, the present invention provides a line fault recovery function for effectively coping with the occurrence of a fault in a line extended by application of such an optical repeater To a passive optical network relay system and a line fault recovery method.
In the PON, the upstream frame data between the OLT and the ONT is provided as a burst, so that a delay occurs for photoelectric conversion and clock recovery when the burst data is transmitted. This delay can not be ignored if the transmission speed is higher than the gigabit transmission rate, and when the photoelectric conversion optical repeater is applied, the delay is doubled and the actual transmitted signal is damaged. Therefore, it is an object of the present invention to provide an optical repeater capable of reducing or preventing signal damage caused by bursted uplink frame data transmission, and to provide a transmission line failure between the OLT and the optical repeater, The present invention provides a passive optical network relay system having a line failure recovery function capable of recovering a faultlessly.
For the sake of understanding of the present invention, when a photoelectric conversion optical repeater is applied to a passive optical network (PON) having a transmission speed of Gigabit or higher, the reason why signal impairment occurs in uplink frame data will first be described with reference to FIG. 2 to FIG.
Two types of embodiments relating to a photoelectric conversion optical repeater for preventing such signal damage will be described with reference to FIGS. 6 to 12, and a description will be given of a method for duplicating the optical repeater and the OLT, An embodiment will be described with reference to Figs. 13 to 19. Fig.
2 is a conceptual diagram for explaining a downlink and uplink signal transmission method of a passive optical network. 2A illustrates a downstream signal transmission method of a passive optical network. As shown in the figure, when the
However, in the case of an upstream signal in which the
2B is a conceptual diagram for explaining an uplink signal transmission method of a passive optical network. As shown in FIG. 2B, the ONTs 2_1 and 2_2 generate uplink signals of predetermined amounts of data at different time points and transmit them to the
As shown in the figure, the upstream signal is a burst signal in which the signal is continuously divided. Since each signal uses its own clock of the ONTs 2_1 and 2_2, the clocks of the upstream burst signals are synchronized with each other or with the OLT clock And there is a deviation from the clock of the
That is, in the illustrated case, since the individual start timings t1, t2 and t3 of the upstream burst signal are different from the clock of the
As a result, the
In the case of the Gigabit PON, a large part of the preamble of the frame data to be transmitted is lost due to the processing delay.
FIG. 3 is a block diagram illustrating a transmission delay element of a gigabit passive optical network. As shown in FIG. 3, the
The
The optical signal thus converted through the
In addition, this delay up burst signal converted is OLT (1) is using a clock (clk_ OLT) (1d) and any other ONT (2) is because using a clock using any ONT clock applied to the signal And is provided to the burst mode clock and data recovery (BCDR)
FIG. 4 is a signal diagram for explaining a transmission delay of a gigabit passive optical network. As shown in the figure, the upstream burst frame data transmitted by the ONT is composed of a preamble (repetition of 1 and 0) and an actual packet. ), The delay time of the laser diode of the optical transceiver, that is, the preparation time of optical signal generation (T TXON ) occurs, and the timing of the optical signal transmitted to the actual optical line is Tc Time must pass. Since the laser diode of the optical transceiver actually needs to be turned off (T TXOFF ), the section where there is no signal on the actual optical path corresponds to Ta.
On the other hand, so an up burst frame, the data transmitted is received in the optical transceiver of the OLT is converted into electrical signals by the optical signal, where the time required for effective electrical signals generated in the photo diode, that is an electric signal generated preparation time (T RXON ), And a delay of the burst mode clock data recovery time (T BCDR ) occurs subsequently. Accordingly, the time point at which the OLT can substantially confirm the uplink frame data is t RS .
As a result, when the upstream frame data is transmitted, the optical signal generation preparation time, the electric signal generation preparation time, and the BCDR time are delayed. This means that if these delays are completed within the preamble period of the upstream frame data, It is possible to do.
For example, if the optical signal generation preparation time, the electrical signal generation preparation time, and the BCDR time are all 12.8 ns in the Gigabit PON communication, a total delay of 38.4 ns occurs. Generally, the preamble (repetition of 1 and 0) constituting the uplink frame data is set to about twice the actual delay in consideration of a change in the network environment such as delay or loss, so that a preamble period of 76.8 ns can be set. In EPON with a transmission rate of 1.25Gbps, for example, one bit is 0.8 ns. Therefore, when 96 bits are used as the preamble interval, 76.8 ns is used. Stable communication is guaranteed only when the expected delay is half the preamble interval.
FIG. 5 is a diagram for describing a transmission delay when an optical repeater is applied to a gigabit passive optical network. The
When the
That is, the
Assuming that all the delay times are 12.8 ns, when the
As a result, this configuration consumes all of the preamble sections set to twice the expected delay for normal PON communication, and in such a case, normal communication becomes difficult in such a case. Particularly, because the
That is, when the
Embodiments of the present invention for preventing such signal damage will be described with reference to FIGS. 6 to 12. FIG.
6 to 7, an OLT or an ONT, which is a component of the existing PON communication, is used as it is, and upstream transmission data can be used without modification and the transmission distance can be extended. Particularly, for this optical relay, the control information of the downlink frame data is analyzed or the transmission method is not modified differently from the standard, so that the load increase can be suppressed and the compatibility can be maintained.
FIG. 6 is a system configuration diagram illustrating a configuration of a relay apparatus and a passive optical network according to an embodiment of the present invention. As shown in FIG. 6, the
An optical repeater 100 constructed between the conventional OLT 1 and the ONT 2 and extending a transmission distance according to an embodiment of the present invention includes a pair of optical fibers 1 and 2 connected to the ONT 2 and the OLT 1, A signal detector 130 for detecting the presence or absence of an upstream burst signal through an optical transceiver 110 connected to the ONTs and a transceiver 110 and a signal detector 130 for receiving optical signals from the optical transceiver 110, A BCDR unit 120 for recovering a clock and data from an electrical burst signal converted into an electrical signal through an optical transceiver function and an optical transceiver 170 connected to the OLT, A CDR unit 160 for recovering an OLT clock and data from a downward continuous signal converted into a signal, and an uplink control unit 160 for storing an uplink burst signal using the clock recovered by the BCDR unit 120 as an input clock, The recovered clock is used as the output clock, And an asynchronous buffer unit 150 for generating an upstream burst frame preamble according to the OLT clock recovered through the CDR unit 160 upon detection of an upstream burst signal through the signal detection unit 130, 150, the asynchronous buffer unit 150 selects the uplink burst frame data following the uplink burst frame preamble generated in advance, and provides the uplink burst frame data to the optical transceiver connected to the OLT according to the OLT clock And a control unit 140. [ The
The
In response to the detection of the uplink burst signal, the
In order to predict the end point of a certain uplink burst frame, the
For example, when the
That is, the proactive uplink burst frame data preamble can be generated in advance by predicting the signal detected by the
When the upstream burst frame preamble generated in this manner is transmitted to the OLT using the OLT clock, the delay caused by the
Meanwhile, during the transmission of the preamble of the upstream burst frame, the actual upstream burst signal is converted into an electrical signal through the ONT-side
The
For example, if the ON time
Since the
In particular, the clock of the upstream burst signal to the
FIG. 7 is a conceptual diagram for explaining the difference in delay time between the case of using the relay apparatus according to the embodiment of the present invention and the case of using the existing optical repeater. As shown in FIG. 7, 10A) includes at least six delays (ONT optical signal generation preparation time (T TXON ), optical repeater electrical signal preparation time (T RXON ), optical repeater burst mode clock data recovery time (T BCDR ) (T TXON ) of the OLT, the electric signal generation preparation time (T RXON ) of the OLT, and the burst mode clock data recovery time (T BCDR ) of the OLT) and the network environment change (additional delay added to each delay time) (T RS1 data restoration time (t RS1 ) of the OLT exceeds the preamble duration ) by generating more delay than the preamble duration by the preamble duration, ONT uplink burst frame data (Fig. 10b) in the case of using the repeater is substantially PON single third delay caused by the communication component (generated optical signals of the ONT preparation time (T TXON), generating an electric signal of the OLT up time (T RXON) , short delay (T SD), only more so of the actual OLT data in the OLT burst mode clock data recovery time (T BCDR)) in addition to one additional delay (optical signal generated preparation time (T TXON of repeaters) in) and a signal detector The restoration time t RS2 is stably within the preamble interval. In particular, since the clock of the upstream burst signal transmitted to the OLT by the optical repeater is the same as the clock of the OLT, the delay time for clock recovery of the BCDR part of the OLT is reduced, but the data restoration time t RS2 of the OLT according to 10b is earlier .
Particularly, although not shown, an optical repeater according to an embodiment of the present invention generates a preamble of upstream burst frame data, and a part of them is a preparation time (T RXON ) of electrical signals for both optical transceivers of the optical repeater, It can be assumed that the optical signal is lost at the optical signal generation preparation time (T TXON ) and the burst mode clock data recovery time (T BCDR ) of the optical repeater, and more preamble may be included in preparation for such loss. However, since the loss of the preamble due to the use of the optical repeater may be compensated, the upstream burst frame data received at the OLT side may be maintained substantially similar to the case of not using the optical repeater. Of course, if the remaining period of the preamble actually transmitted to the OLT is sufficient, the preamble generated by the optical repeater may be reduced to reduce the OLT propagation delay of the upstream burst signal.
Even when the
As a result, when the
In another embodiment of the present invention, an optical repeater may further include an optical repeater capable of relaying an up-and-down continuous signal if necessary, by allowing an optical repeater to receive an upstream burst signal and convert the upstream burst signal into an up- So that it can be configured.
As described above, the
Embodiments of the present invention will be described with reference to FIGS. 8 to 12. FIG.
FIG. 8 is a diagram illustrating a relay system for extending a transmission distance of a passive optical network including a continuous signal conversion repeater according to an embodiment of the present invention. As shown in FIG. 8, The ONT (2) is the same as the existing one. However, the continuous signal
The continuous
Here, the
In the above configuration, the
However, if the interpolation signal of a specific pattern and the actual uplink frame data are mixed as a continuous signal, it is difficult to distinguish the actual uplink frame data.
Accordingly, when generating the interpolation signal, the
Referring to FIG. 9, when the interpolation signal is inserted into the non-signal interval existing between the data of the burst frame data as shown in FIG. 9B, continuous frame data as shown in FIG. 9A is obtained. However, since it is difficult to distinguish the actual burst frame data As shown in FIG. 9C, an interpolation signal in which identification information indicating SoF and EoF, that is, a signal pattern is inserted before and after the actual frame data is generated. Of course, it is possible to use only one signal by inserting information on the length of the frame data following the SoF signal pattern. However, in this case, since the configuration of the
Meanwhile, it is not necessary to perform complicated operations such as demodulating the frame data and confirming the internal information according to the frame structure in order to convert the continuous signal, and it is possible to insert the upstream frame data into the continuous signal at the signal level, 240 can be minimized.
Since the continuous
FIG. 10 is a block diagram of a configuration of a continuous
To this end, the upstream continuous signal receiving
In general, an optical transceiver internally uses a module having a photoelectric conversion unit, a continuous clock data restoration unit, and a simple control unit. In most cases, the internal continuous clock data restoration unit is not used. However, in the embodiment of the present invention, an internal continuous clock data restoration unit already provided in the optical transceiver module can be used to restore the clock of the upward continuous signal. On the other hand, since the uplink continuous signal provided by the continuous
In the detection part, SoF and EoF are detected in the continuous data (frame data, interpolation signal including SoF and EoF) restored by the restored clock. Since EoF is located after the frame data, detection delay occurs in detecting EoF . Therefore, the buffer unit is used to provide the recovered continuous data to the clock
11 is a conceptual diagram for explaining a transceiver output of an OLT capable of receiving an upstream continuous signal according to an embodiment of the present invention.
As shown in FIG. 11A, the upstream continuous data received and restored by the upstream continuous signal receiving
On the other hand, in FIG. 10, the clock
The clock
In a 1: N structure OLT-ONT network configuration, the distance of the ONTs varies, and accordingly, the size of the received upstream burst signal also varies. Accordingly, the burst mode clock data reconstruction unit configured in the conventional OLT precedes the automatic gain adjustment for quantizing the amplitude of the received signal in order to recover the clock and data from the upstream burst signals of the plurality of ONTs received at an arbitrary amplitude. The gain control necessarily inevitably degrades the reception sensitivity. Even if the upstream burst signal is regenerated with a uniform amplitude through the repeater and transmitted, the automatic gain control means operates as long as the OLT uses the burst mode clock data restoration unit as it is. In this case, the reception sensitivity is lowered. However, in the embodiment of the present invention, since the uplink burst signal is used, the uplink burst mode clock data recovery unit can be replaced by the continuous signal clock data recovery unit or the phase detector without the automatic gain control unit. No deterioration occurs.
Since the clock
As a result, the continuous
Therefore, in the case of the relay system using the continuous
The conventional photoelectric conversion repeater has a function of relaying a downward continuous signal and a function of relaying an upward burst signal. Since the upward continuous signal can also be relayed by relaying the upward burst signal, For example.
In addition, when the up / down continuous signal is relayed, the optical transceiver is always in the operating state, and the clock recovery is performed only once, so that the signal loss due to the continuous signal relay does not occur.
Therefore, general photoelectric conversion repeaters capable of relaying a plurality of up-and-down continuous signals between the continuous signal
12 is a configuration example of a relay system for extending a transmission distance of a passive optical network according to an exemplary embodiment of the present invention. The
Therefore, if the transmission delay is extended and the simple delay due to the internal operation of the repeater is considered, the transmission distance can be greatly extended.
Now, an embodiment in which the transmission line failure can be recovered by duplicating one of the optical repeaters according to the embodiment of the present invention and the OLT will be described with reference to FIG. 13 through FIG. The optical repeater shown hereafter has the configuration according to FIG. 6 or FIG. 8, and the OLT can have the existing OLT or the OLT configuration described in FIG.
FIG. 13 shows an example of the configuration of a passive optical network relay system having a line failure recovery function according to an embodiment of the present invention. As shown in the figure, optical paths P1 and P2 are provided between the
2, since the
In general, the OLT carries out a registration process for an ONT (ONU) at the time of activation. Through the registration process, the OLT confirms information about all connected ONTs (ONUs) . On the other hand, when a new ONT (new face) is connected or a configured ONT deviates during operation of a communication network, the distance information (distance information corresponding to the ONT identifier) is also updated through the registration process.
Since the distance information used by the OLT is essential for reception of upstream information due to the characteristics of the PON and is dependent on the physical line, when the optical path switching or replacement occurs, the distance information collection for all the ONTs must be activated again And the activation process requires several tens of seconds to several minutes.
Since the lengths of the substantially redundant light lines (P1 and P2 in the illustrated example) are physically different from each other, if the
It is possible to consider a method in which the OLT collects distance information for each of the different physical lines and provides individual distance information and uses the corresponding distance information in the line switching. However, this is effective only when there is no ONT change, The distance information must be updated every time there is a change such as a new registration, a replacement, a separation, etc., so that it is difficult to apply the method of using a plurality of distance information because the line can not be changed every time.
Therefore, in the embodiment of the present invention shown in FIG. 13, the transmission distance can be extended even in a PON having a transmission speed of at least Gigabit through the optical repeater having the configuration according to FIG. 6 or FIG. 8 and the existing OLT or the configuration shown in FIG. In addition, a failure occurring in an extended transmission line can be recovered in real time by electrically compensating for a change in physical distance.
In an embodiment of the present invention,
14, the
At this time, the output of the transmission unit of each
With such a configuration, the wavelength used by the physical optical path separation can be the wavelength (? 1) for the down signal and the wavelength (? 2) for the up signal, as in the case of using a single optical line. Accordingly, the transmitter and receiver modules used in the
Through this connection configuration, the
The
The
That is, the
In the illustrated example, the operation line is selected by the
On the other hand, in case of extending the electrical length through the delay compensation, it is difficult to transfer the upstream signals received by the
Therefore, it is necessary to take into consideration even this case so that switching at the complete bit level is possible.
FIG. 15 is a configuration example of an OLT having a line failure recovery function according to an embodiment of the present invention. The
The
As described above, the
The
Referring to FIG. 16, a specific operation example of the
Thereafter, if a line failure occurs at a specific time point p1, the uplink frame data through the operation line is no longer reliable. However, the switching
Therefore, even when a light path switching occurs in which the physical length of the
Meanwhile, in the case of the failure recovery method according to the embodiment described with reference to FIGS. 13 to 16, there is a problem that the configuration of the
17 and 18 relate to a passive optical network relay system having a line failure recovery function capable of extending a line length by an optical repeater while using an existing OLT as it is, and capable of quick recovery in case of line failure. The configuration of the
17, the
18, the
The
Also in this configuration, the wavelength used for the downstream signal and the wavelength used for the upstream signal can be used, as in the case of using a single optical line. Accordingly, the transmitter and receiver modules used in the
The
However, when the operation line is determined (for example, P1), the
It may be necessary to prepare the optical signal generation time for the laser diode of the transmission unit to be switched at the switching time of the optical transceiver transmission unit, so that some bits of the uplink frame data may be damaged. However, since the activation / registration process of the OLT is not necessary, the communication change of the electric length compensating method does not cause a communication error that can be recognized. That is, since the data retention due to data damage can occur during the normal communication environment, significant communication failure does not occur due to partial data corruption at the switching time.
In particular, since the conventional OLT can be used as it is when using the OLT, the OLT can be selected according to the necessity of the configuration and the lossless recovery configuration shown in FIG.
FIG. 19 is a flowchart for explaining a line failure recovery method according to an embodiment of the present invention. FIG. 19 is a diagram illustrating a line failure recovery function in which an OLT and a photoelectric conversion optical repeater connected through a pair of optical paths are switched to a
First, in the initial operation, the optical repeater confirms the delay of each duplicated path to designate an operation line to be used, stores the corresponding length compensation delay information, and the OLT activates / regenerates based on the corresponding operation line. And generates distance information for each ONT.
The OLT manages the communication of the PON by using the distance information, operates the communication network, confirms the reception delay information between the upstream frame data received at the same time, and buffers the upstream frame data received through the spare line.
When a line failure occurs and a switching is required, the OLT receives the data from the preliminary line and uses the buffered uplink frame data and the confirmed reception delay information to secure some data to be received after the occurrence of a failure, The optical repeater delays the uplink relay signal according to the determined length compensation delay information and provides the downlink relay signal received from the OLT to the OLT through the preliminary line, The length of the line is compensated by relaying the delay to the ONT.
Through this process, reliable real-time line failure recovery becomes possible.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or essential characteristics thereof. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.
1: OLT 1a: optical transceiver
1b:
1d: OLT clock 2: ONT
2a: optical transceiver 100: optical repeater
110, 170: optical transceiver 120: BCDR unit
130: Signal detection unit 140:
150: asynchronous buffer unit 160: CDR unit
200: continuous signal
220: BCDR unit 230: Signal detection unit
240: control unit 250: asynchronous buffer unit
360: CDR unit 300: OLT
310: Upstream continuous signal receiving optical transceiver 320: Clock recovery unit
330: control unit 340: OLT clock
400,600:
420: control unit 430:
500, 700:
530, 730:
Claims (10)
A delay for the same downlink signal simultaneously provided through the pair of optical paths to the OLT is checked to calculate delay information between the optical lines, and then the delayed information is calculated from the operating line to the protecting line in the transmission / reception signal And a photoelectric conversion optical repeater for applying delay to the distance information provided in the OLT,
The photoelectric conversion optical repeater transmits an upstream signal to the OLT using the OLT clock recovered from the downstream signal received from the OLT,
The OLT checks the inter-line delay information based on the identifiable bit data of the upstream frame data simultaneously transmitted from the photoelectric conversion optical repeater and received through each line, buffers the upstream frame data received through the spare line, A data transfer unit for providing data following the bits of the normally received uplink frame data through the pre-transfer operation line using the uplink frame data of the buffered spare line at the time of transfer, And a processing unit for detecting a failure of the optical line network.
The photoelectric conversion optical repeater includes one transmitter for separating and outputting an optical signal to a pair of optical paths connected to the OLT, and a pair of receiving portions for receiving optical signals received through the pair of optical paths. And a transceiver. The passive optical network relay system has a line failure recovery function.
Wherein the photoelectric conversion optical repeater comprises a pair of receiving portions each for receiving optical signals received through a pair of optical paths and a pair of transmitting portions for selectively outputting optical signals only to the optical path to be used,
The OLT optical transceiver further includes a splitter unit dividing an output optical signal of the OLT optical transceiver into a pair of optical paths and providing an optical signal received through one of the pair of optical paths to a receiver of the OLT optical transceiver Passive Optical Network Relay System with Line Failure Recovery Function.
The OLT receives the uplink continuous signal received from the photoelectric conversion repeater, restores uplink data based on the local OLT clock, and transmits frame data through identification information indicating start and end of frame data identified from the recovered uplink data. Wherein the optical line communication system includes a line failure recovery function.
Collecting the distance information of the ONT using a physically longer optical line as a working line among a pair of optical lines connected to the OLT;
Confirming a delay between adjacent optical lines by confirming a delay for the same downstream signal simultaneously provided through a pair of optical lines connected to the OLT;
When the line is switched, the photoelectric conversion optical repeater delays the upstream relay signal according to the confirmed delay information to provide the OLT with a physically shorter spare line of the pair of optical lines, and confirms the downlink relay signal received from the OLT And relaying the delayed ONT according to the delay information;
Checking the inter-line delay information based on the identifiable bit data among the upstream frame data simultaneously received from the photoelectric conversion optical repeater and received through the respective lines, and buffering the upstream frame data received through the preliminary line; ;
Receiving the upstream frame data from the upstream frame data of the preliminary line buffered at the time of the line transfer successively from the bits subsequent to the bits of the normally received upstream frame data through the pre- A method for repairing a line fault characterized by:
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| KR102521102B1 (en) * | 2022-12-27 | 2023-04-12 | (주)자람테크놀로지 | Optical network device registering delay reduction apparatus for passive optical LAN and optical network device registering method using the same |
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