JP2012109760A - Optical transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmission device capable of accurately monitoring a system which transmits a frequency-multiplexed carrier modulation signal.SOLUTION: An optical transmission device 12-1 according to the present invention includes a failure determiner 51 comprising: a photoelectric conversion unit 25 which photoelectrically converts a part of an optical signal branched by an optical brancher 24 and outputs a frequency-multiplexed carrier signal; a carrier level detection unit 56 which receives the frequency-multiplexed carrier signal outputted from the photoelectric conversion unit 25 and detects, as carrier levels, signal strengths in predetermined bandwidths centering on respective frequencies in which the carrier modulation signal may be possibly included; a memory unit 57 for storing the carrier levels detected by the carrier level detection unit 56; and a determination unit 58 which compares the carrier levels detected by the carrier level detection unit 56 with past carrier levels stored in the memory unit 57 to determine states of carriers.

Description

  The present invention relates to a monitoring function of an optical transmission device used in a system for optically transmitting a plurality of frequency-multiplexed carrier modulation signals.

  When a multi-channel video signal is distributed to each home, a method is generally used, such as CATV, in which individual video signals are carrier-modulated and a frequency-multiplexed signal is distributed. As a transmission path from the video center to each home, there are a coaxial cable, a coaxial cable after being transmitted halfway through an optical fiber, and FTTH (Fiber-To-The-Home) using an optical fiber. FIG. 1 is a configuration example of FTTH.

  The head end 11 receives terrestrial analog broadcasting, terrestrial digital broadcasting, satellite (BS, CS) broadcasting, and the like, and performs level adjustment and frequency conversion as necessary. These signals are frequency-multiplexed and then passed to the optical transmitter 12. The optical transmission device 12 converts the signal from electricity to light and sends it to the optical transmission line 13. The transmitted video signal is transmitted to a video system ONU 15 (ONU: Optical Network Unit) installed in a video viewer's home after long-distance transmission by the optical amplifier 14 or optical multi-distribution. FIG. 2 is a diagram for explaining a method for monitoring the state of such a multi-channel video transmission system.

  FIG. 2 shows the case where monitoring is performed by the optical transmission device 12, but the same applies to the case of other devices on the optical transmission line 13. The pilot signal generation unit 21 frequency-multiplexes the pilot signal with the video signal to be transmitted, and the pilot signal detection unit 27 extracts a part of the optical signal before output and detects the level of the pilot signal. And the determination part 28 monitors the abnormality of a system with the value of the level of a pilot signal (for example, refer nonpatent literature 1). Further, as shown in FIG. 3, the optical transmission device 12 may have a pilot signal generation unit 21 and may be frequency-multiplexed with an input signal in the optical transmission device 12. In addition to the level, a noise level at a frequency in the vicinity of the pilot signal may also be measured and monitored by a CNR (Carrier-To-Noise Ratio) value.

  By such a method, the abnormality of the apparatus or the entire system in the section from the position where the pilot signal is inserted to the pilot signal detection unit 27 is monitored. That is, this system monitors the device failure of the optical transmission device 12 when the pilot signal detector 27 is in the optical transmission device 12, and from the pilot signal insertion point to the optical amplifier when it is in the optical amplifier on the transmission line. Monitor faults in intervening equipment or fiber transmission lines.

  As another method, there is a method of monitoring the input signal itself as shown in FIG. That is, the level or CNR of the input signal is detected by each device on the transmission line, and the system is monitored based on the level (see Non-Patent Document 2).

New Media Technology Series CATV, edited by IEICE, pp. 129-130 First-class cable television broadcasting technology text, Japan CATV Technology Association, pp. 121

  Depending on the failure status of the transmission apparatus, the degradation does not necessarily occur over the entire band in which the signal is transmitted, and a failure in which a part of the transmission band degrades actually occurs. In the pilot signal level monitoring method, when this deteriorated band is away from the pilot signal frequency, failure detection becomes difficult. In addition, when a drop in the level of the pilot signal is detected, it is difficult to distinguish whether the signal transmitted due to a device abnormality has deteriorated or the pilot signal detection unit has failed. Thus, the pilot signal level monitoring system of Non-Patent Document 1 has a problem in monitoring accuracy.

  When monitoring the input signal itself, in actual operation, the case where the broadcast ends and the unmodulated carrier wave is received at the head end, the case where the broadcast station itself does not receive the radio wave due to maintenance, or the head The status and level of individual carriers vary depending on the operational status, such as maintenance of end-side equipment. For this reason, the method of Non-Patent Document 2 has a problem in monitoring accuracy because it is difficult to distinguish between level fluctuations that occur in operation and level fluctuations caused by device failure.

  Accordingly, in order to solve the above-described problems, an object of the present invention is to provide an optical transmission apparatus that can accurately monitor a system that transmits a frequency-multiplexed carrier modulation signal.

  In order to achieve the above object, the optical transmission apparatus according to the present invention sequentially measures levels within a certain bandwidth centered on each frequency for all frequencies where carriers may stand in the transmission band. The value is stored in the memory, and from the past and present values of the measured carrier level, the presence / absence of a carrier at each frequency, the state of the carrier being interrupted due to broadcast suspension or maintenance, It has a function of identifying the carrier non-modulation state, the transmission carrier type change state, and the rain attenuation state as an event different from the device failure, and it is possible to avoid failure determination due to carrier power fluctuation factors other than device failure.

  In this specification, “carrier” means an individual carrier wave modulated by a video signal, such as terrestrial analog broadcast, digital terrestrial broadcast, satellite (BS, CS) broadcast, etc., which is frequency-multiplexed. It does not depend on the state of “A frequency at which a carrier may stand” means a center frequency of a frequency band that may be assigned to the carrier modulation signal of the carrier.

  Specifically, an optical transmission device according to the present invention includes an optical branching device that branches a part of the optical signal from an optical signal that transmits a frequency-multiplexed carrier signal in which carrier modulation signals of a plurality of carriers are frequency-multiplexed. , Photoelectrically converting a part of the optical signal branched by the optical splitter, and outputting the frequency multiplexed carrier signal, receiving the frequency multiplexed carrier signal output by the photoelectric converter, A carrier level detection unit that detects, as a carrier level, signal strength of a predetermined bandwidth centered on each frequency that may contain the carrier modulation signal, and stores the carrier level detected by the carrier level detection unit The carrier level detected by the memory unit and the carrier level detection unit is compared with the past carrier level stored by the memory unit to compare the key. And a failure determination device having a determination unit for determining the rear state.

  The optical transmission apparatus according to the present invention directly monitors the carrier levels of all carrier modulation signals that are main signals, and determines the state of the carrier. Therefore, the present invention can provide an optical transmission apparatus that can accurately monitor a system that transmits a frequency-multiplexed carrier modulation signal.

  The determination unit of the failure determination unit provided in the optical transmission device according to the present invention has a first set value set in advance, and the carrier level detected by the carrier level detection unit is a past carrier stored in the memory unit. The carrier state of the carrier-modulated signal whose carrier level has fluctuated when the level rises or falls below the first set value with reference to the level is determined to be an abnormal state. The present optical transmission apparatus determines that an abnormal state occurs when the carrier level fluctuation amount of the carrier modulation signal becomes large.

  The determination unit of the failure determination unit provided in the optical transmission device according to the present invention is preset with a second setting value that is larger than the first setting value, and the carrier level detected by the carrier level detection unit is Determining that the carrier state of the carrier modulation signal whose carrier level has fluctuated is a state other than an abnormal state when the carrier level has fallen below the second set value with reference to a past carrier level stored in the memory unit. It is characterized by. For example, the output of the carrier modulation signal is stopped during maintenance. This optical transmission apparatus can avoid judging such a state as abnormal.

  When the determination unit determines that the state of the carrier is an abnormal state, the failure determination unit provided in the optical transmission device according to the present invention determines the state of the carrier at a frequency near the carrier that is in an abnormal state. A determination unit is configured to determine that a failure of the optical transmission device itself or the communication system is detected when the state of the carrier at a nearby frequency is also an abnormal state.

  Usually, the carrier levels of a plurality of carrier modulation signals fluctuate at the time of failure. For this reason, the accuracy of failure determination is improved by considering the carrier level of the carrier modulation signal in the vicinity of the carrier modulation signal whose carrier level has fluctuated.

  The determination unit of the failure determination device provided in the optical transmission device according to the present invention is preset with a third setting value and a fourth setting value for determining the carrier state as a deletion state, and the failure determination device includes: The carrier adjacent to the carrier modulation signal whose carrier level fluctuates when the carrier level detected by the carrier level detector rises above the third set value with reference to the past carrier level stored in the memory unit When the carrier level of the modulation signal is lower than the fourth set value with reference to the past carrier level stored in the memory unit, the carrier state of the carrier modulation signal whose carrier level has fluctuated is in a state other than an abnormal state. It is judged that there exists.

  The present optical transmission apparatus can make a failure determination even when a BS digital broadcast down-convert signal, a BS digital broadcast signal, or a CS110 degree signal is included in the carrier modulation signal.

  The determination unit of the failure determination unit provided in the optical transmission device according to the present invention is preset with a fifth set value for determining the carrier state as a rainy state, and is at least one detected by the carrier level detection unit. When the carrier level of the carrier modulation signal is within the fifth set value with reference to the past carrier level stored in the memory unit, it is determined that it is in a rain state.

  The present optical transmission apparatus can determine that the cause of the decrease in the carrier level of the carrier modulation signal is rain.

  The failure determiner included in the optical transmission device according to the present invention receives the frequency-multiplexed carrier signal output from the photoelectric conversion unit, and has a block band including a plurality of frequencies that may include the carrier modulation signal. It further has a block band level detection unit for detecting power as a block band level, the memory unit also stores a block band level detected by the block band level detection unit, and the determination unit determines the state of the carrier In this case, a result of comparing the block band level detected by the block band level detection unit with the past block band level stored in the memory unit is also used.

  This optical transmission apparatus divides the entire transmission band into predetermined blocks and measures the level in each block band, thereby reducing the failure detection time and detecting a failure detection unit abnormality.

  The failure determiner included in the optical transmission apparatus according to the present invention includes a block band level detected by the block band level detection unit and a carrier level of the carrier modulation signal included in the block band detected by the carrier level detection unit. A difference from the sum is calculated, and when the difference is equal to or greater than a predetermined value, it is determined that there is a failure of itself. This optical transmission apparatus can determine the failure of the failure determiner itself.

  The present invention can provide an optical transmission apparatus that can accurately monitor a system that transmits a frequency-multiplexed carrier modulation signal.

It is a figure explaining the structural example of FTTH. It is a figure explaining the means to monitor the conventional optical transmission system. It is a figure explaining the means to monitor the conventional optical transmission system. It is a figure explaining the means to monitor the conventional optical transmission system. It is a figure explaining the optical transmission apparatus which concerns on this invention. It is a figure explaining the state of a carrier. It is a figure explaining the method of determining the state of a carrier. It is a figure explaining the optical transmission apparatus which concerns on this invention. It is a figure explaining the state of a block band. It is a figure explaining the carrier frequency of 90 MHz-770 MHz. It is a figure explaining the carrier frequency of BS and CS band. It is a figure explaining a signal classification and a carrier level. The carrier level is a required CNR (Carrier vs. Noise Ratio).

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
FIG. 5 is a diagram illustrating an example of the optical transmission apparatus according to the first embodiment. Although FIG. 5 shows the case where the optical transmission apparatus is the optical transmission apparatus 12-1, the concept for the monitoring function unit 50-1 is the same even in the case of other apparatuses.

  The optical transmission device 12-1 includes a signal processor 22, an electro-optical converter 23, and a monitoring function unit 50-1. The monitoring function unit 50-1 includes an optical branching device 24 that branches a part of an optical signal that transmits a frequency-multiplexed carrier signal in which carrier modulation signals of a plurality of carriers are frequency-multiplexed, and a failure determination device 51. Prepare. The failure determination unit 51 photoelectrically converts a part of the optical signal branched by the optical branching unit 24 and outputs a frequency multiplexed carrier signal, and the frequency multiplexed carrier signal output by the photoelectric converting unit 25 is output. A carrier level detection unit 56 that detects a signal intensity of a predetermined bandwidth centered on each frequency that may be received and includes a carrier modulation signal as a carrier level, and a carrier level detected by the carrier level detection unit 56 And a determination unit 58 that compares the carrier level detected by the carrier level detection unit 56 with the past carrier level stored by the memory unit 57 to determine the state of the carrier.

  The signal input to the optical transmitter 12-1 is converted into an optical signal by the electro-optical converter 23 via the signal processor 22. In the case of the FM batch conversion method, the signal processor 22 includes processing for FM modulation of input signals in a batch in addition to level adjustment and input signal monitoring in the optical transmitter 12-1.

  The optical branching device 24 takes out a part of this optical signal, and the photoelectric conversion unit obtains a frequency multiplexed carrier signal by O / E converting a part of the optical signal. Thereafter, if the frequency multiplexed carrier signal is an FM batch conversion method, the signal inverse processing unit 26 performs inverse processing as necessary and is input to the carrier level detection unit 56.

  The carrier level detection unit 56 detects a signal intensity in a band in the vicinity of a predetermined frequency as a center as a carrier level. For example, in the 90 MHz to 770 MHz band, which is the VHF / UHF broadcast band, the normal carrier signal bandwidth is 6 MHz or less, and the frequency band in which individual carriers stand is determined. Specifically, the band where the signal carrier to be transmitted stands is divided at intervals of 6 MHz in the band of 90 MHz to 770 MHz, with some exceptions, and the center frequency is determined as shown in FIG. In BS broadcasting and CS broadcasting, the intermediate frequency after down-converting the RF frequency from the satellite is determined as shown in FIG.

  The carrier level detector 56 measures the carrier level after passing through a band pass filter having a band narrower than 6 MHz with respect to the center frequency of this frequency band. The carrier level detection unit 56 performs this measurement for all frequencies where the carrier may stand. In order to detect carrier levels for all frequencies, the carrier level detection circuits are provided in parallel for the number of target frequencies and measured, or by scanning the measurement frequencies, one carrier level detection circuit for all frequencies. Levels will be measured sequentially. In fact, the latter sequential measurement is considered appropriate from the viewpoint of circuit scale and cost.

  The memory unit 57 stores the measured carrier level together with the measured time information. The carrier level is also transferred to the determination unit 58. Even for BS broadcasting and CS110 degree broadcasting, although the signal bandwidth is different, since the center frequency at which the signal stands is determined, the carrier level can be measured by the same method. A signal obtained by down-converting BS digital broadcasting may flow in the UHF broadcasting band. Since this down-converted signal has a bandwidth of about 30 MHz, one carrier of the down-converted signal corresponds to 4 to 5 carrier signals in the normal VHF / UHF band. In the case of the down-converted signal, these carriers are simultaneously transmitted. Will work.

  The determination unit 58 compares the current carrier level with the past carrier level stored in the memory unit 57 for each carrier, and determines the presence / absence of a carrier modulation signal such as a video signal at the frequency and the state of each carrier.

  The carrier state includes a registration state, an abnormal state, a maintenance state, and a deletion state. FIG. 6 is a diagram for explaining the relationship between the states. The registration state is a state in which there is a carrier at the frequency and there is no abnormality in the carrier level. An abnormal state is a state in which the carrier level of the frequency is considered to be deteriorated due to a device failure or the like. The maintenance state is different from the abnormal state. For example, the maintenance state is a state in which the carrier in the registration state is temporarily disconnected by an artificial operation such as headend maintenance. The deleted state is a state in which the frequency is not used and no carrier exists.

Next, determination conditions for determination performed by the determination unit 58 regarding the four states of the carrier will be described.
If the current carrier level is compared with the past carrier level and the level fluctuation is equal to or less than a certain first set value A [dB], the carrier state does not change except for some exceptions described later.
When the carrier level is detected at startup for the frequency that is the carrier level detection target, or when the past carrier state is in a state other than the registered state and the current carrier level is above a certain level, the state transits to the registered state. To do. Further, when the carrier level is below a certain level at the time of activation, the state transits to the deletion state.

Other state transitions of the carrier will be described.
The state in which the current carrier level of the carrier in the registered state transitions according to the fluctuation amount x [dB] from the past carrier level will be described with reference to FIG. If the carrier level fluctuation amount x of the carrier in the registered state is an increase greater than or equal to the first set value A [dB] or deterioration of A <x <second set value B [dB], the determination unit 58 determines that the carrier is abnormal. It is determined that the state has been reached. Further, when the fluctuation amount x is a deterioration of x> B, the determination unit 58 determines that the carrier is in a maintenance state. This is because there are few cases where the carrier level is greatly deteriorated at a stroke due to an actual failure, while the signal level is lowered at a time in order to turn off the carrier output at the time of headend maintenance.

  Also, if the carrier level of the carrier in the maintenance state has recovered to a certain value or more, the carrier level has fluctuated by more than the first set value A with reference to the carrier level in the past registration state In addition, the determination unit 58 determines that the state of the carrier is not an abnormal state and is newly registered. Then, the memory unit 57 stores the carrier level as a new past value. In this case, it is considered that the signal type of the carrier corresponding to the frequency has been changed. Since the required transmission quality varies depending on the signal type, the carrier level also varies depending on the required quality. An example of the difference in carrier level depending on the signal type of CNR (Carrier-to-Noise Ratio), which is a parameter representing required quality, is shown in FIG.

  When a certain time elapses in the maintenance state of a certain carrier, the determination unit 58 determines that the carrier has changed from the maintenance state to the deletion state. This is because the carrier level is usually recovered when the maintenance is completed, and it is considered that the carrier is deleted when the maintenance is not recovered. The fixed time in this case can be determined based on a standard time required for maintenance.

  Also, in BS broadcasting and CS broadcasting, there is a case where the radio wave of a certain carrier received at the head end becomes weak due to rain, and finally attenuates to such an extent that it cannot be viewed. In this way, when the received radio wave is significantly attenuated, the satellite signal processing device at the head end 11 turns off the output to the optical transmission device 12-1 (squelch function ON), or the optical transmission device 12 One of the operations for continuously outputting noise components to -1 (squelch function OFF) can be set.

  In general, the satellite signal processing device of the head end 11 turns on the squelch function so that unnecessary noise components are not generated when rain falls. Here, if only a part of predetermined carriers among the plurality of satellite broadcast carriers is turned off, the predetermined carrier level can always be obtained from the carrier even when the rain is attenuated. For example, the determination unit 58 sets the fifth setting value for determining the carrier state as a rainy state, and sets the carrier level when the carrier level of the squelch-off carrier being monitored is in the past registered state. If it is within the fifth set value as a reference, it can be determined that rain has occurred. That is, even if the carrier level of another carrier is attenuated, the determination unit 58 can determine that the rain attenuation state is in effect at that time if the carrier level of the squelch OFF carrier is the fifth set value. .

  The failure determiner 51 can determine the failure of the optical transmission apparatus or system based on such a carrier state. Specifically, since a failure in which only one carrier deteriorates is not normally possible, when the determination unit 58 detects an abnormal state of a carrier, the failure determination unit 51 notifies the determination unit 58 in the vicinity of the carrier. The states of the carriers are searched, and when both are in the abnormal state, it is determined that the optical transmission device or the system is abnormal. By determining the state of nearby carriers in this way, it is possible to prevent a failure from being determined for an artificial operation that causes the level of the head end 11 to fluctuate by one carrier for some reason, thereby improving the accuracy of the failure determination. ing. Here, the nearby carriers can be two or more carriers centering on the carriers in an abnormal state.

  When the carrier level of a certain carrier frequency rises by a third set value C [dB] or more in a band where there is a BS digital broadcast down-convert signal, a BS digital broadcast signal, and a CS 110 degree signal, the determination unit 58 The carrier level at the frequency ± 6 MHz corresponding to the adjacent carrier position in the UHF band is confirmed. If the carrier level of the adjacent carrier has decreased by the fourth set value D [dB] or more at the same timing as the increase of the carrier, it is considered that the BS digital broadcast has ended, and the failure determination unit 51 is a device for any frequency. Not determined as a failure.

The optical transmitter 12-1 can obtain the following effects by including the monitoring function unit 50-1.
The monitoring function unit 50-1 is a method of determining a device failure by monitoring the main signal, but the main signal level fluctuation factors other than the device failure such as headend equipment maintenance, signal type change, and rain attenuation Can be detected, it is possible to avoid issuing a device failure alarm due to factors other than device failure, and to improve the accuracy of system monitoring.
In addition, the monitoring function unit 50-1 can detect a failure in which a part of the transmission band deteriorates, and can improve the accuracy of system monitoring.

(Embodiment 2)
FIG. 8 is a diagram illustrating an example of the optical transmission apparatus according to the second embodiment. Although FIG. 8 shows the case where the optical transmission device is the optical transmission device 12-2, the concept for the monitoring function unit 50-2 is the same in the case of other devices. The optical transmission device 12-2 has a configuration in which a block band level detection unit 66 is added as compared with the optical transmission device 12-1 of FIG. In FIG. 8, the photoelectric conversion unit 25 and the signal reverse processing unit 26 are also added, but are not essential. The possibility of addition may be determined in consideration of ease of actual circuit design or whether to include the photoelectric conversion unit 25 and the signal inverse processing unit 26 in the failure determination of the failure determination unit 52 itself described later. .

  The optical transmission device 12-2 includes a signal processor 22, an electro-optical converter 23, and a monitoring function unit 50-2. The monitoring function unit 50-2 includes an optical branching device 24 that branches a part of an optical signal that transmits a frequency-multiplexed carrier signal in which carrier modulation signals of a plurality of carriers are frequency-multiplexed, and a failure determination device 52. Prepare. The failure determiner 52 receives the frequency multiplexed carrier signal output from the photoelectric conversion unit 25 to the failure determiner 51 of FIG. 5 and blocks the power of the block band including a plurality of frequencies that may include the carrier modulation signal. A block band level detection unit 66 that detects the band level is further included.

  The memory unit 57 also stores the block band level detected by the block band level detection unit 66, and the determination unit 58 determines the block band level detected by the block band level detection unit 66 when determining the carrier state. The result of comparing the past block band level stored in the memory unit 57 is also used.

  The block band level detection unit 66 divides the transmission band into one or more blocks and determines the total power in each block band (hereinafter referred to as “total power in the block band”) as the “block band level”. ”))). The memory unit 57 stores the detected block bandwidth level together with the detected time information. The block band level detection unit 66 also outputs the block band level to the determination unit 58. Based on the current block band level and the past block band level stored in the memory unit 57, the determination unit 58 determines the presence / absence of a video signal at a frequency within the band of the block and the state of each carrier.

  The block band level state includes a registration state, an abnormal state, and a deletion state. FIG. 9 is a diagram for explaining the relationship between the states. The registration state is a state in which carriers exist in the block band and there is no abnormality in each block band level. The abnormal state is a state in which the block band level in the block band is considered to be deteriorated due to a device failure or the like. The deletion state is a state in which there is no carrier in the block band, that is, there is no signal to be transmitted. In this case, the value is not used for the determination condition described later.

  The measurement of each block band level is sequentially repeated.

  The following is an example of a block bandwidth. The signal band to be transmitted is classified into three types: VHF / UHF band (70 to 770 MHz), BS band (about 1 to 1.5 GHz), and CS band (about 1.6 to 2.1 GHz), and each block Band. Since the VHF / UHF band (70 to 770 MHz) has a large number of carriers, this band may be further divided. Similar to the carrier state determination based on the carrier level described in the first embodiment, the determination unit 58 compares the current block band level and the past block band level to determine the block band state.

  The determination unit 58 determines that the state of the block band is in the registration state when the state of the previous block band is in the deleted state or when the current block band level is equal to or higher than a certain level. In addition, the determination unit 58 determines the state of the block band if the past block band state is in an abnormal state and the current block band level is within a certain range from the block band level when the current block band level is the registered state in the past. Is determined to be registered. Further, the determination unit 58 determines that the state of the block band is in the deleted state when the block band level is equal to or lower than a certain level at the time of activation. On the other hand, the determination unit 58 determines that the state of the block band is abnormal when the fluctuation amount x [dB] from the past block band level in the registered state to the current block band level increases or deteriorates beyond a certain value. It is determined that a state has been reached.

  The failure determiner 52 can determine the failure of the optical transmission apparatus or system based on such a block band level state. Specifically, when the determination unit 58 determines an abnormal state at the block band level, the carrier level detection unit 56 measures the carrier levels of a plurality of representative carriers in the block band. The failure determination unit 52 determines that the optical transmission device 12-2 or the system is abnormal when the same deterioration tendency is observed in the carrier level of any representative carrier. This determination can be made only by the carrier level detection performed by the optical transmission device 12-1 in FIG. 5, but since it is necessary to sequentially detect the carrier levels of all the carriers, the number of carriers is several tens. It takes time to determine that there are ~ a few dozen. For this reason, in a system in which power is reduced over the entire band due to the occurrence of a failure and the number of carriers in an abnormal state increases, the block bandwidth level detection method of the failure determiner 52 is used rather than the failure determiner 51 of FIG. A failure can be determined quickly.

  Further, the failure of the failure determiner 52 itself can be determined from the block band level and each carrier level. When the value of the block band level is compared with the sum of the carrier levels in the block band, the difference is usually less than a certain value (level detection error range). However, when the two values are different from each other by a certain value or more, the failure determination unit 52 determines that the failure is its own failure, for example, the failure of the photoelectric conversion unit 25 or the signal reverse processing unit 26.

The optical transmission device 12-2 can obtain the following effects in addition to the effects of the optical transmission device 12-1 by including the monitoring function unit 50-2.
The monitoring function unit 50-2 can quickly detect a fault having a high influence level across the entire band by combining the block band state determination and the carrier state determination.
Further, the monitoring function unit 50-2 can detect a failure of the monitoring function unit 50-2 itself by combining the block band state determination and the carrier state determination.

11: Head end 12, 12 ', 12 ", 12-1, 12-2: Optical transmitter 13: Optical transmission line 14: Optical amplifier 15: ONU
21: Pilot signal generator 22: Signal processor 23: Electro-optic converter 24: Optical splitter 25: Opto-electric converter 26: Signal inverse processor 27: Pilot signal detector 27 ': Main signal detector 28: Determination Units 50-1, 50-2: monitoring function units 51, 52: failure determination unit 56: carrier level detection unit 57: memory unit 58: determination unit 66: block band level detection unit

Claims (8)

An optical branching device for branching a part of the optical signal from an optical signal transmitting a frequency-multiplexed carrier signal in which carrier modulation signals of a plurality of carriers are frequency-multiplexed;
A photoelectric conversion unit that photoelectrically converts a part of the optical signal branched by the optical splitter and outputs the frequency-multiplexed carrier signal;
A carrier that receives the frequency-multiplexed carrier signal output from the photoelectric conversion unit and detects a signal intensity of a predetermined bandwidth centered on each frequency that may contain the carrier-modulated signal as a carrier level. Level detector,
A memory unit for storing a carrier level detected by the carrier level detector;
And a failure determiner having a determination unit that compares the carrier level detected by the carrier level detection unit with the past carrier level stored in the memory unit to determine the state of the carrier;
An optical transmission device comprising: The determination unit of the failure determiner is
The first set value is preset,
When the carrier level detected by the carrier level detection unit rises or falls below the first set value with reference to the past carrier level stored in the memory unit, the carrier level of the carrier modulation signal whose carrier level has changed The optical transmission device according to claim 1, wherein the state is determined to be an abnormal state. The determination unit of the failure determiner is
A second set value that is greater than the first set value is preset,
When the carrier level detected by the carrier level detection unit is lower than the second set value with reference to the past carrier level stored in the memory unit, the carrier state of the carrier modulation signal whose carrier level has fluctuated is changed. The optical transmission device according to claim 2, wherein it is determined that the state is other than an abnormal state. The failure determiner is
When the determination unit determines that the state of the carrier is an abnormal state, the determination unit causes the determination unit to determine the state of the carrier that is in the vicinity frequency of the carrier that is in the abnormal state, and the state of the carrier that is in the vicinity frequency is also The optical transmission device according to claim 2, wherein when the optical transmission device is in an abnormal state, it is determined that the optical transmission device itself or a communication system has a failure. The determination unit of the failure determiner is
A third setting value and a fourth setting value for determining the state of the carrier as a deletion state are set in advance;
The failure determiner is
The carrier adjacent to the carrier modulation signal whose carrier level fluctuates when the carrier level detected by the carrier level detector rises above the third set value with reference to the past carrier level stored in the memory unit When the carrier level of the modulation signal is lower than the fourth set value with reference to the past carrier level stored in the memory unit, the carrier state of the carrier modulation signal whose carrier level has fluctuated is in a state other than an abnormal state. The optical transmission device according to claim 1, wherein the optical transmission device is determined to be present. The determination unit of the failure determiner is
A fifth setting value for determining the state of the carrier as a rainy state is preset,
When the carrier level of at least one of the carrier modulation signals detected by the carrier level detection unit is within the fifth set value with reference to the past carrier level stored in the memory unit, it is determined that it is raining. The optical transmission device according to claim 1, wherein the optical transmission device is an optical transmission device. The failure determiner is
A block band level detection unit that receives the frequency-multiplexed carrier signal output from the photoelectric conversion unit and detects power of a block band including a plurality of frequencies that may include the carrier modulation signal as a block band level; Have
The memory unit is
The block band level detected by the block band level detection unit is also stored,
The determination unit
2. When determining the state of the carrier, a result obtained by comparing a block band level detected by the block band level detecting unit with a past block band level stored in the memory unit is also used. 7. The optical transmission device according to any one of items 1 to 6. The failure determiner is
A difference between a block band level detected by the block band level detection unit and a sum of carrier levels of the carrier modulation signals included in the block band detected by the carrier level detection unit is calculated, and the difference is equal to or greater than a predetermined value. The optical transmission device according to claim 7, wherein the optical transmission device is determined to be a failure of itself.

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