JP4994300B2 - Optical termination device - Google Patents

Description

  The present invention relates to an optical termination device, and more particularly to an optical termination device used in a wavelength division multiplexing optical communication system using an optical fiber transmission line branched into a plurality by a power splitter.

  In recent years, with the increase in data communication traffic including the Internet, construction of large-capacity core networks and metro networks using wavelength division multiplexing (WDM) technology is progressing. This WDM technology can contribute not only to an increase in capacity but also to a flexible network construction by assigning different services and users for each wavelength. In the access network, in order to cope with an increase in data communication traffic, an optical access method using time division multiplexing (TDM) technology is introduced. Examples thereof include GE-PON (Gigabit Ethernet (registered trademark) Passive Optical Network) and G-PON (Gigabit-capable Passive Optical Network). In these optical access systems, a power splitter is used to divide the optical fiber transmission line into a plurality of parts, and the optical fiber from the accommodation station to the power splitter is shared by a plurality of subscribers, thereby reducing the cost per subscriber. Yes.

  However, if the current optical access method using TDM technology can cope with further increases in data communication traffic in the future, higher-speed electric circuits will be required, resulting in higher cost of electric components and lower power consumption. It will increase. On the other hand, many studies have been made on WDM-PON in which WDM technology is applied to an access network. According to this system, for example, by assigning one wavelength to one subscriber, the service band per subscriber can be increased without increasing the speed of the electric circuit.

  GE-PON and G-PON service providers are expected to consider using existing networks with power splitters as a premise for introducing WDM-PON. If this is possible, the cost required for changing the existing network can be saved. In addition, it is considered desirable to realize a second optical termination unit (ONU: Optical Network Unit) arranged on the subscriber side that does not depend on the wavelength, that is, a single type (colorless) ONU. This is because if a plurality of types of ONUs having different transmission wavelengths and reception wavelengths are used, convenience is greatly reduced.

  Fig. 1 shows the configuration of a WDM-PON using an existing network. A first optical terminal device (OLT: Optical Line Terminal) 110 arranged on the accommodation station side and N ONUs 120 are coupled by an optical fiber 20 via a power splitter 10 arranged outside the station. In the OLT 110, the obtained outputs of N OSUs (Optical Subscriber Units) 111 are respectively coupled to the wavelength multiplexer / demultiplexer 112. The light from the monitoring light source 113 is combined with the WDM light input / output to / from the wavelength multiplexer / demultiplexer 112 via the monitoring light source multiplexer 114.

  On the other hand, in the ONU 120, the output of the optical transmitter 121 is coupled to the wavelength multiplexer / demultiplexer 124, and the output of the wavelength multiplexer / demultiplexer 124 is coupled to the optical receiver 122 via the wavelength variable filter 123. Part of the light input / output from the wavelength multiplexer / demultiplexer 124 is input to the light receiver 126 via the monitoring light source branching filter 125, and the wavelength control circuit 128 based on the monitoring information obtained by the detector 127. The optical transmitter 121 and the tunable filter 123 are configured to be controlled. The optical transmitter 121 can change the transmission wavelength, and realizes the colorless ONU in cooperation with the wavelength variable filter 123 that selects the reception wavelength. In order to make the ONU 120 colorless, it is necessary to consider the selection of the wavelength multiplexer / demultiplexer 124.

  FIG. 2 shows an example of WDM-PON wavelength arrangement. In FIG. 2, an upward arrow and a downward arrow indicate an upstream signal and a downstream signal, respectively. A dotted line indicates an ITU-T grid. In FIG. 2, the upstream wavelength and the downstream wavelength are divided into different wavelength bands. In this wavelength arrangement, it is desirable to use a low-loss optical filter that collectively multiplexes and demultiplexes the wavelength bands of the upstream signal and downstream signal as the multiplexer / demultiplexer, but an optical coupler can also be used.

FIG. 3 shows an example of the correspondence between the upstream wavelength and the downstream wavelength and the usage state. Here, for convenience, the correspondence between the upstream wavelength and the downstream wavelength is determined in the order of the smallest wavelength number, that is, the order of the shortest wavelength, but any other combination is possible. The ONU 120 coupled to the power splitter 10 needs to assign unused wavelengths to the optical transmitter 121 and the optical receiver 122 inside. For _{example, ONU 1 120-1~ONU N-1 120} -N-1 is coupled to the power splitter 10, ONU _N where there is already used state combinations to the wavelength No. 1 to N-1 as shown in FIG. 3 Are combined, the combination of wavelength numbers N becomes an unused wavelength. In order to detect this unused wavelength, here, unused wavelength (or used wavelength) information superimposed on the monitoring light source is used. The monitoring light on which the unused wavelength (or used wavelength) information is superimposed is combined with the downstream signal in the monitoring light source multiplexer 114 and sent to each ONU 120. Each ONU 120 demultiplexes the monitoring light and the downstream signal in the monitoring light source demultiplexer 114. The demultiplexed monitoring light is photoelectrically converted by the light receiver 126, reads unused wavelength (or used wavelength) information superimposed on the detector 127, and sends the read result to the wavelength control circuit 128. The wavelength control circuit 128 sends a control signal to the optical transmitter 121 and the wavelength tunable filter 123, and sets each wavelength to an unused wavelength. However, this configuration requires the monitoring light source 113, the monitoring light source multiplexer 114, and the monitoring light source demultiplexer 125 in order to perform this wavelength setting.

  On the other hand, a wavelength setting method that does not require a monitoring light source has also been proposed (see Patent Document 1). FIG. 4 shows the configuration of a conventional ONU that does not require a monitoring light source. The ONU 130 includes an optical transmitter 131, an optical receiver 132, a wavelength tunable filter 133, a wavelength multiplexer / demultiplexer 134, a detector 135, and a wavelength controller 136. As in the configuration of FIG. 1, the optical transmitter 131 can change the transmission wavelength and realizes a colorless ONU in cooperation with the wavelength variable filter 133 that selects the reception wavelength. Differ in the detection method of unused wavelengths. In this method, first, the transmission wavelength of the wavelength tunable filter 133 is swept while matching the downstream wavelength. Next, a part of the signal photoelectrically converted in the optical receiver 132 is sent to the detector 135, the optical power is measured, and the measurement result is sent to the wavelength controller 136.

  In the wavelength controller 136, if the optical power is smaller than or below a certain value, the upstream wavelength of the optical transmitter is set to a wavelength corresponding to the downstream wavelength at this time. If the optical power is greater than or equal to a certain value, the transmission wavelength of the wavelength tunable filter 133 is further swept, and the above operation is performed again. According to this method, since the unused wavelength is detected by measuring the optical power of the downstream signal, there is an advantage that a monitoring light source is not required.

International Publication No. 2007/086514 Pamphlet Makoto Murakami, Takamasa Imai, and Masaharu Aoyama, “A remote supervisory system based on subcarrier overmodulation for submarine optical amplifier systems”, IEEE J. Lightwave Technol., 1996, Vol. 14, No. 5, pp. 671-677

However, it is assumed that ONU _{1 to} ONU _N-1 are coupled to the power splitter 10 and ONU _N is coupled where the combinations of wavelength numbers 1 to N-1 are already in use as shown in FIG. In this case, since N-1 downstream wavelengths have already been used, unused wavelengths are finally detected after sweeping the wavelength tunable filter N times, and it may take a long time to complete the wavelength setting. Can happen.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an optical terminator capable of completing wavelength setting in a short time without using a monitoring light source. .

In order to achieve such an object, the invention according to claim 1 is an optical termination device coupled to an optical fiber transmission line branched into a plurality by a power splitter, and is branched into a plurality by the power splitter. A first optical transmission unit coupled to the optical fiber after the first optical transmission unit, the first optical transmission unit capable of changing the transmission wavelength, the first optical reception unit capable of changing the reception wavelength, and the transmission of the first optical transmission unit A first optical wavelength multiplexer / demultiplexer that multiplexes and demultiplexes the light and the received light of the first optical receiver, and a first detector that detects an unused received wavelength from the output signal of the first optical receiver; The reception wavelength of the first optical reception unit is set to the unused reception wavelength detected by the first detection unit, and the transmission wavelength of the first optical transmission unit is a transmission wavelength corresponding to the set reception wavelength. Wavelength setting means for setting to the power The second optical terminator coupled to the optical fiber before being branched by the splitter receives the second optical transmission unit that transmits transmission light on which unused wavelength information is superimposed, and the transmission light of the first optical transmission unit A plurality of optical transmission / reception devices, and a transmission light and a reception light of the plurality of optical transmission / reception devices, and a second detection unit that detects a reception wavelength from an output signal of the second optical reception unit. And the second optical wavelength multiplexer / demultiplexer, and when the reception wavelength of the second optical reception means is detected by the second detection means, all the reception wavelengths detected by the second detection means are detected. a wavelength monitoring means for generating an unused wavelength information, sends it to the second optical transmission means control signals, and the unused wavelength information for setting the wavelength of the transmission light of the second optical transmission means based, It is provided with.

  According to a second aspect of the present invention, in the optical termination device according to the first aspect, the first detection unit measures whether or not the received optical power of the first optical reception unit is equal to or higher than a predetermined threshold value, or An unused reception wavelength is detected by reading unused wavelength information superimposed on the transmission light of the second optical transmission means.

  According to a third aspect of the present invention, in the optical termination device according to the second aspect, when the first detection unit cannot read unused wavelength information superimposed on the transmission light of the second optical transmission unit , Re-sweep the reception wavelength of the first optical reception means, and measure again whether the reception optical power of the first optical reception means is equal to or higher than a predetermined threshold value, or use the transmission light of the second optical transmission means An unused reception wavelength is detected by reading the superposed unused wavelength information.

  According to a fourth aspect of the present invention, in the optical termination device according to the second aspect, the first detection unit detects a first unused reception wavelength, and the wavelength control unit detects the first unused unit. When the first optical receiving means does not detect the transmission wavelength from the second optical transmission means even though the transmission wavelength of the first optical transmission means corresponding to the reception wavelength is set, the first optical reception The reception wavelength of the means is swept again, and it is measured again whether the received optical power of the first optical receiving means is equal to or higher than a predetermined threshold value, or the unused light superimposed on the transmitted light of the second optical transmitting means The second unused reception wavelength is detected by reading the wavelength information.

  According to a fifth aspect of the present invention, in the optical termination device according to the second aspect, the first detection unit detects a first unused reception wavelength, and the wavelength control unit detects the first unused unit. When the first optical receiving means does not detect the transmission wavelength from the second optical transmission means even though the transmission wavelength of the first optical transmission means corresponding to the reception wavelength is set, the first detection means Measures again whether or not the received optical power of the first optical receiving means is equal to or higher than a predetermined threshold after the elapse of a random time determined by generating a random number, or the transmitted light of the second optical transmitting means The second unused reception wavelength is detected by reading the unused wavelength information superimposed on.

  According to a sixth aspect of the present invention, in the optical terminal device according to the fifth aspect, the first detection unit detects a second unused reception wavelength, and the second unused reception wavelength is detected by the wavelength control unit. When the first optical receiving means does not detect the transmission wavelength from the second optical transmission means despite setting the transmission wavelength of the first optical transmission means corresponding to the reception wavelength, the wavelength control means is , Re-sweep the reception wavelength of the first optical reception means, and measure again whether the reception optical power of the first optical reception means is equal to or higher than a predetermined threshold value, or use the transmission light of the second optical transmission means A third unused reception wavelength is detected by reading the superimposed unused wavelength information.

  According to a seventh aspect of the present invention, in the optical terminator according to the fourth or sixth aspect, the wavelength control unit determines a reception wavelength after the sweeping of the first optical reception unit by generating a random number. A random wavelength is set.

  According to an eighth aspect of the present invention, in the optical termination device according to any one of the first to seventh aspects, the first optical transmission means superimposes transmission wavelength information transmitted from the first optical wavelength multiplexer / demultiplexer. The transmission light is transmitted, and the second detection means detects the transmission wavelength by reading the transmission wavelength information superimposed on the transmission light of the first transmission means, and the second optical transmission means can change the transmission wavelength. The wavelength monitoring means sets the transmission wavelength of the second optical transmission means to the transmission wavelength detected by the second detection means.

  According to the present invention, wavelength setting can be completed in a short time without using a monitoring light source in the optical termination device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment)
FIG. 5 shows a configuration of a first optical terminal device (OLT) coupled to the optical fiber before being branched by the power splitter according to the first embodiment of the present invention. The OLT 210 includes N OSUs 211, a wavelength multiplexer / demultiplexer 212, and a wavelength monitoring circuit 213. Each OSU 211 includes an optical transmitter 214, an optical receiver 215, and a detector 216.

When the upstream signal light from the ONU reaches the optical receiver 215 of the OSU _i , the upstream signal is subjected to photoelectric conversion, and the received wavelength information is detected by the detector 216 and sent to the wavelength monitoring circuit 213. However, if the same upstream signal light arrives simultaneously from another ONU, the detector 216 determines that the signal light has not arrived from the ONU, and does not send the received wavelength information to the wavelength monitoring circuit 213. The wavelength monitoring circuit 213 is coupled to all the N OSUs 211 and grasps the OSU 211 that is not in the operating state (or in the operating state). In other words, the unused wavelength (or used wavelength) information is grasped.

When the wavelength monitoring circuit 213 receives the received wavelength information of the OSU _i 211, the wavelength monitoring circuit 213 sends a control signal for transmitting a downstream signal from the optical transmitter 214 and unused wavelength (or used wavelength) information to the optical transmitter 214. . The optical transmitter 214 transmits a downlink signal on which unused wavelength (or used wavelength) information is superimposed. When superimposing unused wavelength information on downstream signals, for example, in GE-PON, channels that are logically separated from the main signal, such as monitoring frames used to grant transmission permission to upstream signals, are used. Can be used. In addition, a channel physically separated from the main signal by a subcarrier multiplexing (SCM) technique or the like can be used (see Non-Patent Document 1).

  On the other hand, FIG. 6 shows a configuration of a second optical terminator (ONU) coupled to the optical fiber after being branched into a plurality by the power splitter according to the first embodiment of the present invention. The configuration of this ONU 220 is the same as the ONU of FIG. 4, but the wavelength setting process of the wavelength controller 226 is different. First, the transmission wavelength of the wavelength tunable filter 223 is swept while matching the downstream wavelength. With respect to the set wavelength by the first sweep, for example, a rule such as selecting a combination of wavelength number 1 for the wavelength arrangement of FIG. 3 may be determined.

  Next, a part of the signal photoelectrically converted in the optical receiver 222 is sent to the detector 225 to measure whether or not the received optical power of the optical receiver 222 is equal to or higher than a predetermined threshold value. If the received light power is greater than or equal to the threshold value, unused wavelength (or used wavelength) information superimposed on the downlink signal is read. These results are sent to the wavelength controller 226. The wavelength controller 226 sets the wavelength of the optical transmitter 221 to a wavelength corresponding to the downstream wavelength at this time if the optical power is less than or less than the threshold. If the optical power is greater than or equal to the threshold value, the transmission wavelength of the wavelength tunable filter 223 is swept to the unused downstream wavelength based on the unused wavelength (or used wavelength) information, and the optical transmitter The upstream wavelength of 221 is set to the corresponding wavelength. When there are a plurality of unused wavelengths, there is a problem as to which wavelength to set, but this can be solved by setting a rule in advance. For example, with respect to the wavelength arrangement of FIG. 3, rules such as selecting a combination with the smallest wavelength number among unused wavelengths, generating a random number, and selecting an arbitrary set among combinations of unused wavelengths are set. Apply.

According to this method, the unused wavelength is detected not only by measuring the optical power of the downstream signal wavelength but also by reading the unused wavelength (or used wavelength) information superimposed on the downstream signal. If the number of ONUs 220 is not large, the wavelength setting is completed in a short time by sweeping the transmission wavelength of the tunable filter 223 at most twice. Specifically, for example, ONU ₁ ~ONU _N-1 220 is coupled to the power splitter 10, as shown in FIG. 3, ONU _N where the combination of up to a wavelength No. 1 to N-1 are already in use state Assume that 220 is coupled. In that case, even if the transmission wavelength of the wavelength tunable filter 223 is first adjusted to the wavelengths from the wavelength numbers 1 to N−1, the unused wavelength information is read there, and the next wavelength tunable filter 223 sweeps the wavelength. The unused wavelength number N can be reached. Needless to say, if the transmission wavelength of the wavelength tunable filter 223 is first matched with the wavelength of the wavelength number N, the unused wavelength can be reached by one sweep.

  According to the present embodiment, since the unused wavelength is detected from the optical power measurement value of the downlink signal and the unused wavelength (or used wavelength) information superimposed on the downlink signal, additional monitoring light is required. There is no such thing as.

  FIG. 7 shows a wavelength setting process of the second optical terminator (ONU) according to the embodiment of the present invention. When this wavelength setting process is started (S600), the wavelength tunable filter 223 is swept through the wavelength control circuit 226 (S601), the transmission wavelength is set to a predetermined downstream signal wavelength, and the unused wavelength is set by the following method. Is detected (S602, S603). In the detection of the unused wavelength, when the optical power is smaller than or below the predetermined threshold, the downstream wavelength at that time is detected as an unused wavelength. When the optical power is greater than or equal to a predetermined threshold, unused wavelength (or used wavelength) information superimposed on the downlink signal is read, and the unused wavelength is detected based on the result. Thereafter, a second sweep of the wavelength tunable filter 223 is performed via the wavelength control circuit 226, and the detected unused wavelength is set (S604).

  Next, the ONU 220 sets the wavelength of the optical transmitter 221 to the detected unused wavelength via the wavelength control circuit 226, and transmits the upstream wavelength corresponding to the unused downstream wavelength (S605). After transmitting the upstream wavelength, the ONU 220 confirms whether or not there is a wavelength received from the OLT 210 at the corresponding downstream wavelength (S606). When the reception wavelength is confirmed, the ONU 220 and the OSU 211 start communication (S607) and end the wavelength setting process (S610).

  However, in S606, when the upstream wavelength reaches the corresponding OSU 211 simultaneously from another ONU 220, or when the OSU 211 fails, the received wavelength is not confirmed within a certain time. In that case, the wavelength can be set in a short time by performing the following two processes.

  In the first method, the entire wavelength setting process is repeated after the wavelength variable filter 223 is swept again and set to another downstream signal wavelength. When the ONUs 220 are simultaneously connected, when the process is executed, a plurality of ONUs 220 may simultaneously sweep the wavelength tunable filter 223. Therefore, it is desirable to select an arbitrary set of unused wavelength combinations based on random numbers in order to avoid re-competition (S609).

  In the second method, the optical power measurement (S602) and subsequent processes are retried without re-sweeping the wavelength tunable filter 223, and the same upstream wavelength is retransmitted. At this time, the retry process is performed after the elapse of a random time determined by generating a random number, thereby reducing the probability of contention in the OSU 211 with other ONUs 220 (S608).

  As shown in FIG. 7, S609 can be performed after S608 is performed. Further, both S608 and S609 are not necessarily performed, and only one of S608 and S609 may be performed.

  Similarly, when the unused wavelength information superimposed on the downlink signal cannot be read, the wavelength tunable filter 223 is similarly swept again, set to another downlink signal wavelength, and then quickly repeated by repeating the entire wavelength setting process. Wavelength setting is possible.

  The transmission wavelength of each OSU 211 is determined by the initial setting of the optical transmitter 214. If the optical transmitter 214 of the OSU 211 is made variable in wavelength and wavelength information is superimposed on the upstream signal by the ONU, it is designated on the ONU side. The optical transmitter 214 can be set to the transmission wavelength. That is, the transmission wavelength information is transmitted from the wavelength control circuit 226 of the ONU 220 to the optical transmitter 221, and the optical transmitter 221 transmits the transmission wavelength information to the upstream signal in the same manner as the optical transmitter 214 superimposes the wavelength information on the downstream signal. Superimpose. The OSU 211 that has received the upstream signal reads the transmission wavelength information by the detector 216 and sends it to the wavelength monitoring circuit 213. The wavelength monitoring circuit 213 can set the transmission wavelength of the optical transmitter 214 of the OSU 211 based on the transmission wavelength information sent from the ONU 220.

It is a figure which shows the structure of WDM-PON using the existing network. It is a figure which shows an example of WDM-PON wavelength arrangement | positioning. It is a figure which shows an example of the correspondence of an upstream wavelength, and a downstream wavelength, and a use condition. It is a figure which shows the structure of ONU which does not require a monitoring light source. It is a figure which shows the structure of the 1st optical termination device (OLT) couple | bonded with the optical fiber before branching with the power splitter which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the 2nd optical termination device (ONU) couple | bonded with the optical fiber after branching into multiple with the power splitter which concerns on Embodiment 1 of this invention. It is a flowchart which shows the wavelength setting process of the 2nd optical termination unit (ONU) concerning embodiment of this invention.

Explanation of symbols

10 Power splitter 20 Optical fiber 110, 220 OLT
111, 211 OSU
112, 124, 134, 212, 224 Wavelength multiplexer / demultiplexer 113 Monitoring light source 114 Monitoring light source multiplexer 120, 130, 220 ONU
121, 131, 214, 221 Optical transmitters 122, 132, 215, 222 Optical receivers 123, 133, 223 Tunable filter 125 Monitoring light source demultiplexer 126 Receivers 127, 135, 216, 225 Detectors 128, 136, 226 Wavelength control circuit 213 Wavelength monitoring circuit

Claims (8)

An optical termination device coupled to an optical fiber transmission line branched into a plurality by a power splitter,
The first optical terminator coupled to the optical fiber after being branched into a plurality by the power splitter,
A first optical transmission means capable of changing a transmission wavelength;
First optical receiving means capable of changing the reception wavelength;
A first optical wavelength multiplexer / demultiplexer for multiplexing / demultiplexing the transmission light of the first optical transmission means and the reception light of the first optical reception means;
First detection means for detecting an unused reception wavelength from an output signal of the first optical reception means;
The reception wavelength of the first optical reception unit is set to the unused reception wavelength detected by the first detection unit, and the transmission wavelength of the first optical transmission unit is a transmission wavelength corresponding to the set reception wavelength. And wavelength setting means for setting to
The second optical terminator coupled to the optical fiber before being branched by the power splitter,
Second optical transmission means for transmitting transmission light on which unused wavelength information is superimposed;
Second optical receiving means for receiving the transmission light of the first optical transmission means;
Second detection means for detecting a reception wavelength from an output signal of the second optical reception means;
A plurality of optical transmission / reception devices comprising:
A second optical wavelength multiplexer / demultiplexer that multiplexes / demultiplexes the transmission light and reception light of the plurality of optical transceivers;
When the reception wavelength of the second optical reception means is detected by the second detection means, unused wavelength information is generated based on all reception wavelengths detected by the second detection means, and each of the second optical transmission means a wavelength monitoring means for sending control signals to set the wavelength of the transmission light, and the unused wavelength information to the second optical transmission means,
An optical termination device comprising:   The first detecting means measures whether or not the received optical power of the first optical receiving means is greater than or equal to a predetermined threshold value, or reads unused wavelength information superimposed on the transmitted light of the second optical transmitting means 2. The optical termination device according to claim 1, wherein an unused reception wavelength is detected by the method.   When the first detection unit cannot read the unused wavelength information superimposed on the transmission light of the second optical transmission unit, the reception wavelength of the first optical reception unit is swept again, and the first optical unit again An unused received wavelength is detected by measuring whether the received optical power of the optical receiving means is equal to or greater than a predetermined threshold or by reading unused wavelength information superimposed on the transmitted light of the second optical transmitting means The optical terminal device according to claim 2. Although the first detection means detects a first unused reception wavelength and the wavelength control means sets the transmission wavelength of the first optical transmission means corresponding to the first unused reception wavelength. When the first optical receiving means does not detect the transmission wavelength from the second optical transmitting means,
Re-sweep the reception wavelength of the first optical receiving means and measure again whether the received optical power of the first optical receiving means is equal to or higher than a predetermined threshold value, or to the transmitted light of the second optical transmission means 3. The optical termination device according to claim 2, wherein the second unused reception wavelength is detected by reading the superimposed unused wavelength information. 4. Although the first detection means detects a first unused reception wavelength and the wavelength control means sets the transmission wavelength of the first optical transmission means corresponding to the first unused reception wavelength. When the first optical receiving means does not detect the transmission wavelength from the second optical transmitting means,
The first detecting means measures again whether or not the received light power of the first light receiving means is equal to or higher than a predetermined threshold after the elapse of a random time determined by generating a random number, or the second light 3. The optical termination device according to claim 2, wherein the second unused reception wavelength is detected by reading unused wavelength information superimposed on the transmission light of the transmission means. Although the first detection means detects a second unused reception wavelength, and the wavelength control means sets the transmission wavelength of the first optical transmission means corresponding to the second unused reception wavelength. When the first optical receiving means does not detect the transmission wavelength from the second optical transmitting means,
The wavelength control unit re-sweeps the reception wavelength of the first optical reception unit and measures again whether or not the received optical power of the first optical reception unit is equal to or higher than a predetermined threshold value, or the second optical transmission 6. The optical termination device according to claim 5, wherein the third unused reception wavelength is detected by reading unused wavelength information superimposed on the transmission light of the means.   7. The optical termination device according to claim 4, wherein the wavelength control unit sets the reception wavelength after the re-sweep of the first optical reception unit to a random wavelength determined by generating a random number. 8. .   The first optical transmission unit transmits transmission light on which transmission wavelength information transmitted from the first optical wavelength multiplexer / demultiplexer is superimposed, and the second detection unit is superimposed on the transmission light of the first transmission unit. The transmission wavelength is detected by reading the transmission wavelength information, the second optical transmission means can change the transmission wavelength, and the wavelength monitoring means determines the transmission wavelength of the second optical transmission means by the second detection means. 8. The optical termination device according to claim 1, wherein the detected transmission wavelength is set.

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