JP4956447B2 - Subscriber premises optical line terminator and optical transmission system - Google Patents

Description

  The present invention relates to an optical line terminator installed in a subscriber's house and an optical transmission system in which this is connected to a center side optical line terminator through a PON type optical transmission line.

  In an optical network such as FTTH and CATV, as described in Patent Document 1 below, an optical transmission path connected to a center is branched by a passive splitter, and an optical transmission path is laid to a plurality of subscriber homes. A PON (Passive Optical Network) type optical transmission system is used. Such an optical transmission system is also called PDS (Passive Double Star).

  In the PON type optical transmission system, as shown in FIG. 8, an optical line termination device (OLT: Optical Line Termination) at the center is connected to a multiplexing end of a splitter 903 via an optical fiber 902, and a plurality of splitter 903 Optical line terminators (ONU: Optical Network Units) 905-1,... 905-n installed in each subscriber's house are connected to the demultiplexing ends via optical fibers 904-1,.

  The configuration of ONUs 905-1,... 905-n is shown in FIG. This figure shows the configuration of the ONU 905-1 as an example. The ONU 905-1 includes an optical transceiver unit 906, an ONU function unit 907, and an Ethernet (registered trademark) interface 908. An optical fiber 904-1 connected to the splitter 903 is connected to the optical transceiver unit 906 via an optical termination unit 909 provided at each subscriber's house.

  As the Ethernet (registered trademark) interface 908, 10/100/1000 BASE-TX or the like can be used, and for example, a LAN cable 910 is connected thereto. A terminal device 914 such as a computer or a printer can be directly connected to the LAN cable 910, or a switch such as a router 912 or a switching hub 913 can be connected to another terminal device 914.

In order for terminal devices, switches, and the like (hereinafter referred to as external nodes) connected to the ONU at the subscriber's home side to be able to communicate, a predetermined communication condition is required between the center-side OLT and the subscriber-side ONU. It must be established. When it is confirmed that a predetermined communication condition is established between the OLT and the ONU, a terminal device or the like connected to the ONU becomes communicable with the OLT on the center side via the ONU.
JP-A-9-214541

  When the communication condition is established between the ONU on the subscriber's home side and the OLT on the center side, and the communication condition is established with the external node connected to the ONU, the external node communicates with the OLT via the ONU. Communication is possible between the two. However, since there has been no means for confirming whether the external node connected to the ONU operates normally and outputs a normal signal, this is detected even when the external node is not operating normally. Therefore, it was not possible to take appropriate measures. For this reason, there is a problem in that an upstream signal from an external node that is not operating normally is also transmitted after being terminated.

  Therefore, the present invention has been made to solve such a problem, and by determining whether or not the connected external node outputs a normal signal, the external node that is not operating normally is determined. It is an object of the present invention to provide a subscriber premises optical line terminating device and an optical transmission system capable of detecting the above.

According to a first aspect of the subscriber-side optical line terminator of the present invention, a downlink signal input from the center-side optical line terminator is terminated and output to an external node, and an uplink signal input from the external node is received. A customer premises optical line terminating device that performs termination processing and outputs the result to the center side optical line terminating device, and is connected to the center side optical line terminating device to perform photoelectric conversion and reverse photoelectric conversion. , An optical line terminator function unit connected to the electrical / optical conversion unit for performing the termination process, and a serial unit connected to the optical line terminator function unit for serial / parallel conversion and inverse serial / parallel conversion / a parallel converter, and an interface module having a connection end of said serial / are connected to the parallel conversion unit said external node, before the said interface module Comprising an uplink signal determination means for determining whether said uplink signal satisfies a predetermined normal signal conditions by entering the upstream signal input to the serial / parallel conversion section, wherein the optical network unit function part Includes a multiplexing unit that inputs the determination result of the normal signal condition from the uplink signal determination unit and multiplexes it with the uplink signal, and the electrical / optical conversion unit receives the determination result by the multiplexing unit. The multiplexed uplink signal is converted into an optical signal and transmitted to the center side optical line termination device .

  According to another aspect of the subscriber premises optical line terminator of the present invention, the upstream signal determination means is provided in the serial / parallel converter or the optical line terminator function unit.

  In another aspect of the subscriber premises optical line termination device of the present invention, the uplink signal determination means determines that the normal signal condition is satisfied when the voltage of the uplink signal is equal to or higher than a predetermined threshold, and otherwise It is characterized by determining that it does not satisfy.

In another aspect of the subscriber premises optical line termination device according to the present invention, the uplink signal determination means is configured to detect the normal signal condition when a bit pattern of a control signal included in the uplink signal matches a predetermined coding rule. It is determined that it is satisfied, and it is determined that it is not satisfied otherwise.

  In another aspect of the subscriber premises optical line terminator according to the present invention, the upstream signal determination means fills in between the pulse signals when the control signal matches a predetermined bit pattern consisting of a pulse signal having a constant period. Thus, it is converted to a constant continuous signal, and it is determined whether or not the continuous signal matches a predetermined coding rule.

  In another aspect of the subscriber premises optical line termination device of the present invention, the uplink signal determination means determines that the normal signal condition is satisfied when the clock of the uplink signal matches a predetermined speed, and otherwise It is determined that it does not satisfy | fill.

  According to another aspect of the subscriber premises optical line terminator of the present invention, the upstream signal determination means uses the optical line terminator function unit to confirm that either PON link or authentication has been established with the center. It is characterized by being executed after being judged.

According to a first aspect of the optical transmission system of the present invention, there is provided a subscriber-side optical line terminator according to any one of the first to seventh aspects , one multiplexing end, and two or more demultiplexing ends. And an optical coupler for connecting the customer premises optical line terminator to the demultiplexing end via an optical fiber, and a center side light connected to the multiplexing end of the optical coupler via another optical fiber. And a line termination device.

  In another aspect of the optical transmission system of the present invention, the center-side optical line terminator includes an external node diagnosis unit that requests the subscriber premises side optical line terminator to execute the uplink signal determination unit. It is characterized by being.

  According to the present invention, it is possible to detect an external node that is not operating normally by determining whether or not the external node connected to the subscriber's premises optical line termination device is outputting a normal signal. It becomes possible.

(First embodiment)
With reference to the drawings, a detailed description will be given of the configuration of a subscriber premises optical line termination device and an optical transmission system in a preferred embodiment of the present invention. 1 and 2 are block diagrams showing schematic configurations of the subscriber premises optical line termination unit (ONU) and the optical transmission system according to the first embodiment of the present invention, respectively. An ONU 100 of the present embodiment shown in FIG. 1 is an apparatus used in the PON type optical transmission system 1 of the present embodiment shown in FIG.

  In the PON type optical transmission system 1 of FIG. 2, the PON interface card 10 provided in the center has an optical line terminator (OLT) 11 and an authentication function unit 12, and performs optical transmission to the optical input / output terminal of the OLT 11. One end of the optical fiber 20 that is a path is connected. The optical coupler (optical multiplexing / demultiplexing unit) 30 has one multiplexing end and two or more demultiplexing ends. The other end of the optical fiber 20 connected to the OLT 11 is connected to the multiplexing end. It is connected.

  One end of each of a plurality of optical fibers 40-1,..., 40-n (n: natural number, hereinafter referred to as 40-1 to n) is connected to the demultiplexing end of the optical coupler 30, and each other end is connected. Are connected to ONUs 50-1 to n. With such a configuration, the downstream signal from the OLT 11 is demultiplexed by the optical coupler 30 and transmitted to each of the ONUs 50-1 to 50-n, while the optical signal transmitted from each of the ONUs 50-1 to 50-n is transmitted to the optical coupler 30. Are combined and transmitted to the OLT 11.

  Each of the ONUs 50-1 to 50-n is installed at each subscriber's house, and an external node 70 such as a personal computer or a switch is connected to the ONUs. In FIG. 2, the external node 70 is a switch, and a plurality of terminal devices 80 are connected to a plurality of ports 70a provided in the switch. Examples of the switch used for the external node 70 include an L2 switch, an L3 switch, and a router. With such a configuration, a plurality of terminal devices 80 can be connected to the center OLT 11 via the ONU 100.

  The OLT 11 and the ONUs 50-1 to 50-n include GPON (which is an abbreviation for Gigabit Passive Optical Network, a method compliant with ITU standard G.984.x), GEPON (an abbreviation for Gigabit Ethernet (registered trademark) PON), and IEEE802. A device that conforms to the 3) standard) is used.

  The ONU 100 of this embodiment can be used for the ONUs 50-1 to 50-n shown in FIG. In the following, it is assumed that the ONU 100 is used for the ONU 50-1. As shown in FIG. 1, the ONU 100 according to the present embodiment includes an electrical / optical conversion unit 110, an optical line terminator function unit (hereinafter referred to as an ONU function unit) 120, a serial / parallel conversion unit 130, and an interface module 140. I have.

  The electrical / optical conversion unit 110 and the ONU function unit 120 are connected by first serial transmission lines 150a (downstream signal lines) and 150b (upstream signal lines) that transmit serial electrical signals. The ONU function unit 120 and the serial / parallel converter 130 are connected by parallel transmission paths 160a (downstream signal lines) and 160b (upstream signal lines) for transmitting parallel electrical signals. The parallel signal transmitted through the parallel transmission paths 160a and 160b can be, for example, a 10-bit signal. Further, the serial / parallel converter 130 and the interface module 140 are connected by second serial transmission lines 170a (downstream signal lines) and 170b (upstream signal lines) for transmitting serial electrical signals.

  The electrical / optical conversion unit 110 has an optical input / output terminal for transmitting / receiving an optical signal to / from the center-side OLT 11 via the optical fiber 40, and an optical signal (downlink) transmitted from the center OLT 11. Signal) is converted into an electrical signal (photoelectric conversion). This electrical signal is output to the ONU function unit 120 via the first serial transmission line 150a which is a downstream signal line. In addition, an electrical signal input from the ONU function unit 120 via the first serial transmission line 150b, which is an upstream signal line, is converted into an optical signal (reverse photoelectric conversion). This optical signal is transmitted to the OLT 11 via the optical fiber 40.

  The ONU function unit 120 converts the serial signal input from the electrical / optical conversion unit 110 into a parallel signal, and after performing a predetermined termination process, the signal is serial / parallel via a parallel transmission path 160a that is a downstream signal line. The data is output to the conversion unit 130. The parallel signal input from the serial / parallel converter 130 via the parallel transmission line 160b, which is an upstream signal line, is converted into a serial signal after being subjected to predetermined termination processing, and is output to the electrical / optical converter 110. ing.

  The serial / parallel conversion unit 130 includes serial / parallel conversion means and reverse serial / parallel conversion means (not shown). The parallel signal input from the ONU function unit 120 is converted into a serial signal by the reverse serial / parallel conversion means. The data is output to the interface module 140 via the second serial transmission line 170a which is a downstream signal line. Further, the serial signal input from the interface module 140 via the second serial transmission path 170 b is converted into a parallel signal by the serial / parallel conversion means and output to the ONU function unit 120.

  Further, the interface module 140 is connected to the external node 70 by a serial electric signal. In the ONU 100 of the present embodiment, the interface module 140 corresponds to the MSA (Multi-Source Agreement) interface standard, and can be directly connected to an MSA interface slot (not shown) provided in the external node 70. It is configured. Examples of MSA interface standards include GBIC and SFP.

  The ONU 100 of the present embodiment configured as described above has a processing function for enabling communication between the OLT 11 and the external node 70. The processing function for enabling communication is provided in the ONU function unit 120. The ONU function unit 120 includes two MAC units, a first MAC unit 121 and a second MAC unit 122, a management interface 123, and a multiplexing unit. 124. The first MAC unit 121 and the second MAC unit 122 perform media access control (MAC) in compliance with IEEE 802.3ah. The first MAC unit 121 performs MAC processing related to communication with the center OLT 11, and the second MAC 122 unit performs MAC processing related to communication with the external node 70.

  The management interface 123 connected to the first MAC unit 121 performs a predetermined procedure for establishing communication with the OLT 11 via the first MAC unit 121 and confirms that a predetermined communication condition is established. Process to enable communication between the two. As one of the communication conditions, a predetermined optical signal transmitted from the OLT 11 is confirmed (confirmation of the optical SD), and a predetermined signal is exchanged with the OLT 11 to confirm that the predetermined condition is satisfied. . If this is confirmed, a PON link is established with the OLT 11. The establishment of the PON link corresponds to the establishment of the second layer link in the OSI (Open Systems Interconnection) reference model.

  Furthermore, after the PON link is established, the authentication function unit 12 provided on the center side accesses the ONU 100 to acquire authentication mode data, and identifies and authenticates the ONU 100 based on this. Authentication modes include a MAC address authentication mode and an automatic authentication mode. As a communication condition required for enabling communication between the OLT 11 and the ONU 100, either the above-described PON link or authentication can be established.

  The second MAC unit 122 has, for example, 10 Mbps, 100 Mbps, and 1 Gbps Ethernet (registered trademark) MAC functions, and may have a 10-bit interface (TBI) unit (not shown) as a parallel interface. The TBI unit is connected to the serial / parallel conversion unit 130 via 10 downstream signal lines 160a and 10 upstream signal lines 160b.

  As described above, when a communication condition is established between the ONU 100 and the OLT 11 by establishing a PON link or authentication, a signal for notifying communication permission to the external node 70 connected to the ONU 100 Is output. As a result, the external node 70 becomes communicable with the center-side OLT 11 via the ONU 100, and a signal can be transmitted from the external node 70 to the OLT 11.

  However, in the conventional ONU, it was not possible to confirm whether the signal output from the external node is normal. Therefore, even if an abnormal signal is output from the external node, the conventional processing is terminated as it is. Had been sent to. Further, the center side cannot know whether or not the signal transmitted from the external node is normal.

  On the other hand, in the ONU 100 of the present embodiment, it is possible to diagnose whether the signal output from the external node 70 (hereinafter referred to as the upstream signal A) is normal (whether the normal signal condition is satisfied). In addition, an upstream signal determination unit 180 and a multiplexing unit 124 are further provided. The uplink signal determination unit 180 has a function of diagnosing the uplink signal A input from the external node 70 to the ONU 100 via the interface module 140 based on a predetermined determination criterion. The multiplexing unit 124 It has a function for notifying the OLT 11 when the determining means 180 determines that the upstream signal A is abnormal. Alternatively, in any case where the upstream signal A is determined to be normal or abnormal, the determination result may be notified to the OLT 11.

  In the present embodiment, in order to diagnose the upstream signal A when it is input from the external node 70 to the serial / parallel converter 130 via the interface module 140, the upstream signal determination unit 180 is included in the serial / parallel converter 130. It is set as the structure to provide. Further, the multiplexing means 124 is provided in the ONU function unit 120, and is used for a predetermined channel (for example, a maintenance channel) of an upstream signal (hereinafter referred to as upstream signal B) when termination processing is performed by the ONU function unit 120. The results determined by the uplink signal determining means 180 can be multiplexed.

  The uplink signal determination means 180 can be configured to always execute this or to execute it at predetermined intervals. Alternatively, it may be executed upon receipt of a predetermined request signal. As an example, a request signal can be read from a predetermined channel of a downlink signal transmitted from the OLT 11, and the uplink signal determination unit 180 can be executed when the request signal is on.

  The upstream signal B obtained by multiplexing the determination result by the upstream signal determination unit 180 by the multiplexing unit 124 is output from the ONU function unit 120 to the electrical / optical conversion unit 110, where it is converted into an optical signal and transmitted to the OLT 11. The The OLT 11 reads out the determination result by the upstream signal determination means 180 from a predetermined channel of the input upstream signal B, and can know from this whether or not the external node 70 is outputting a normal signal. As described above, since it is possible to detect an abnormality of the external node 70 on the center side, for example, it is possible to promptly take appropriate measures such as making the ONU 100 outputting an abnormality signal in a state where communication is impossible. become able to.

  In addition, when the ONU 100 of the present embodiment is used, it is possible to appropriately request diagnosis from the center side for a plurality of external nodes 70 connected to the optical transmission system 1. FIG. 3 shows an embodiment of the optical transmission system of the present invention configured to request diagnosis of the external node 70 connected to the ONU 100 from the center side.

  In the optical transmission system 2 of the embodiment shown in FIG. 3, when the external node diagnosis means 13 is provided in the PON interface card 10 and the external node diagnosis means 13 is executed on the center side, a diagnosis request for requesting the upstream signal determination means 180 to be executed. The signal is output to the OLT 11, and the diagnosis request signal can be multiplexed to a predetermined channel of the downlink signal and transmitted to the ONU 100 in the OLT 11. The ONU 100 reads the diagnosis request signal from a predetermined channel of the downlink signal transmitted from the OLT 11, and causes the uplink signal determination means 180 to be executed when this request signal is on.

  Next, a method for determining whether or not the upstream signal A satisfies the normal signal condition in the upstream signal determination unit 180 of the present embodiment will be described below. As a first method, there is a method of diagnosing the voltage of the upstream signal A input from the interface module 140 in the upstream signal determination means 180. The voltage of the upstream signal A includes, for example, the amplitude of the upstream signal A. As shown in FIG. 4, the upstream signal A is a signal corresponding to “0” or “1” in a predetermined cycle. In the method of diagnosing the voltage of the upstream signal A, since it is necessary to diagnose the voltage of the signal corresponding to “1”, it is equivalent to “1” by diagnosing the voltage of the upstream signal A over a certain period. It is necessary to be able to diagnose the voltage of the signal to be transmitted.

  As an example, when the upstream signal A is generated by the 8B10B system, the voltage of the upstream signal A in a period corresponding to 10 bits may be diagnosed. A signal generated by the 8B10B system includes a bit of “1” in a 10-bit signal a plurality of times.

  By diagnosing whether the voltage of the upstream signal A is equal to or higher than a predetermined threshold value (threshold value L) over the predetermined period, the voltage of the signal corresponding to “1” is at least once or more as shown in FIG. It can be compared with a threshold value L. As a result, if a signal having a threshold value L or more is detected, it is determined that the upstream signal A satisfies the normal signal condition. On the other hand, if a signal that is equal to or greater than the threshold value L is not detected once in a certain period, it is determined that the upstream signal A does not satisfy the normal signal condition. Such determination based on the voltage of the upstream signal A is hereinafter referred to as LOS (Loss of Signal) determination.

  A second method for determining whether or not the upstream signal A satisfies the normal signal condition in the upstream signal determination unit 180 will be described below. The upstream signal A output from the external node 70 is generated with a bit string having a predetermined number of bits as one unit according to a predetermined encoding rule. The predetermined control signal included in the upstream signal A includes a signal that repeats a predetermined number of times with the same bit pattern. Therefore, in the second method for determining the upstream signal A, the upstream signal determining means 180 detects the repetitive pattern in the control signal, and when the repetitive pattern matches a predetermined coding rule, the upstream signal A is detected. Is determined to satisfy the normal signal condition, otherwise it is determined that the normal signal condition is not satisfied. Hereinafter, such determination is referred to as COMMA determination.

  Since the control signal used for the COMMA determination has a bit pattern that repeats the pulse signal at a certain period, it can be converted into a constant continuous signal so as to fill the space between the pulse signals. FIG. 5 shows an embodiment in which pulse signals are filled and converted into a constant continuous signal. By performing the COMMA determination using the continuous signal C as shown in FIG. 5, the processing in the upstream signal determination means 180 can be facilitated.

  A third method for determining whether or not the upstream signal A satisfies the normal signal condition in the upstream signal determination means 180 will be described below. The upstream signal A output from the external node 70 includes clock information that is a transmission rate. Therefore, in the third method for determining the upstream signal A, the clock information is read from the upstream signal A, and it is determined whether or not it matches the clock (for example, 1.25 Gbps) set in the ONU 100. Hereinafter, such determination is referred to as sync determination.

  As a result of performing the sync determination in the upstream signal determination means 180, when it is determined that the clock of the upstream signal A and the clock of the ONU 100 match, it is determined that the upstream signal A satisfies the normal signal condition, Otherwise, it is determined that the normal signal condition is not satisfied.

  As another embodiment of the subscriber-side optical line termination device of the present invention, it is determined that the upstream signal determination means 180 satisfies the normal signal condition when any of the above-described LOS determination, COMMA determination, and sync determination is satisfied. However, it can also be determined that the other conditions are not satisfied.

  In the ONU 100 of the above-described embodiment, the upstream signal determination unit 180 is provided in the serial / parallel converter 130. However, the present invention is not limited to this, and the upstream signal determination unit 180 may be provided in another location of the ONU 100. FIG. 6 shows an ONU 200 in which the upstream signal determination means 180 is provided in the ONU function unit 120 as another embodiment of the subscriber premises optical line termination device of the present invention.

  In the ONU 200 of the present embodiment, the upstream signal determination unit 180 is executed using an LSI included in the ONU function unit 120. Further, the upstream signal A can be input from the serial / parallel conversion unit 130 to the ONU function unit 120, and the upstream signal determination unit 180 can determine the normal signal condition using the upstream signal A. In the ONU 200 of this embodiment, the determination result of the uplink signal determination unit 180 can be directly output to the multiplexing unit 124 provided in the same ONU function unit 120.

  FIG. 7 shows an ONU 300 in which the upstream signal determination means 180 is provided in a single processing device 301 as still another embodiment of the customer premises optical line termination device of the present invention. In the present embodiment, the upstream signal A is input from the serial / parallel converter 130 to the processing device 301, and the upstream signal determination means 180 provided in the processing device 301 uses the upstream signal A to set the normal signal condition. It can be configured to determine. The determination result of the upstream signal determination unit 180 is output to the multiplexing unit 124 in the ONU function unit 120 via a predetermined signal line.

  Note that the description in the present embodiment shows an example of a subscriber premises optical line terminating device and an optical transmission system according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of the subscriber premises optical line terminating device and the optical transmission system in the present embodiment can be changed as appropriate without departing from the spirit of the present invention.

It is a block diagram which shows schematic structure of the subscriber premises optical line termination | terminus apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows an example of the optical transmission system which concerns on embodiment of this invention. It is a block diagram which shows an example of the optical transmission system which concerns on another embodiment of this invention. It is a schematic diagram which shows one Example of the change of the voltage of an upstream signal. It is a schematic diagram which shows one Example which filled between the pulse signals of a control signal and converted into the fixed continuous signal. It is a block diagram which shows schematic structure of another embodiment of the subscriber optical fiber terminal device of this invention. It is a block diagram which shows schematic structure of another embodiment of the subscriber premises optical line termination | terminus apparatus of this invention. It is a block diagram which shows the conventional optical transmission system. It is a block diagram which shows schematic structure of the subscriber premises optical line termination | terminus apparatus of the conventional optical transmission system.

Explanation of symbols

1, 2 Optical transmission system 10 PON interface card 11, 901 OLT
12 Authentication Function Unit 13 External Node Diagnosis Means 20, 40, 902, 904 Optical Fiber 30, 903 Optical Coupler 50 ONU
70 External node 80, 914 Terminal equipment 100, 200, 300, 905 Subscriber-side optical line termination device 110 Electrical / optical conversion unit 120, 907 ONU function unit 121 First MAC unit 122 Second MAC unit 123 Management interface 124 Multiplexing Means 130 Serial / Parallel Conversion Unit 140 Interface Modules 150a and 150b First Serial Transmission Lines 160a and 160b Parallel Transmission Lines 170a and 170b Second Serial Transmission Line 180 Upstream Signal Determination Means 301 Processing Device

Claims (9)

Terminate the downlink signal input from the center side optical line terminator and output it to the external node, and terminate the uplink signal input from the external node and output it to the center side optical line terminator An optical line termination device,
An electrical / optical converter connected to the center side optical line terminator for performing photoelectric conversion and reverse photoelectric conversion;
An optical line terminator function unit connected to the electrical / optical conversion unit and performing the termination process;
A serial / parallel converter connected to the optical line terminator function unit for performing serial / parallel conversion and inverse serial / parallel conversion;
An interface module connected to the serial / parallel converter and having a connection end to the external node;
And a uplink signal determination means for determining whether the or the serial / parallel converter said uplink signal enter the upstream signal input to meet the predetermined normal signal condition from the interface module,
The optical line terminating device function unit has a multiplexing unit that inputs the determination result of the normal signal condition from the uplink signal determination unit and multiplexes it to the uplink signal,
The electrical / optical conversion unit converts the uplink signal in which the determination result is multiplexed by the multiplexing unit into an optical signal and transmits the optical signal to the center-side optical line terminating device. Subscriber premises optical line termination equipment. 2. The subscriber premises optical line terminator according to claim 1 , wherein the uplink signal determination means is provided in the serial / parallel converter or the optical line terminator function unit. The uplink signal determining means, the voltage of the uplink signal is determined to the normal signal condition is satisfied when the predetermined threshold value or more, in claim 1 or 2, characterized in that determined not to satisfy the otherwise The subscriber premises optical line terminator as described. The uplink signal determination means determines that the normal signal condition is satisfied when a bit pattern of a control signal included in the uplink signal matches a predetermined coding rule, and determines that the other is not satisfied 3. The subscriber premises optical line terminator according to claim 1 or 2 . The upstream signal determining means converts the control signal into a constant continuous signal so as to fill a space between the pulse signals when the control signal matches a predetermined bit pattern made up of a pulse signal having a constant period, and the continuous signal 5. The subscriber premises optical line termination device according to claim 4 , wherein it is determined whether or not the stipulation rules are met. The uplink signal determining means, said determining a normal signal condition is satisfied when the uplink signal clock matches the predetermined speed, according to claim 1 or 2, characterized in that determined not to satisfy the otherwise A subscriber-side optical line termination device as described in 1. The uplink signal determining means according to claim 1 or 2, characterized in that it is performed that either PON links or authentication with the center is established after it is determined by the optical line terminal function unit A subscriber-side optical line termination device as described in 1. A subscriber premises optical line termination device according to any one of claims 1 to 7 ,
An optical coupler that has one multiplexing end and two or more demultiplexing ends, and connects the customer premises optical line terminator to the demultiplexing end via an optical fiber;
An optical transmission system comprising: a center-side optical line terminator connected to a multiplexing end of the optical coupler via another optical fiber. The center optical network unit is as claimed in claim 8, characterized in that to the customer premises ONU has an external node diagnosis means for requesting execution of the uplink signal determining means Optical transmission system.

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