Communication system, first optical communication device, second optical communication device, and method for determining transmission path characteristics

Abstract

Provided is a communication system comprising one or more first optical communication devices, a second optical communication device that communicates with the one or more first optical communication devices, and an optical transmission path connecting the one or more first optical communication devices and the second optical communication device, wherein the one or more first optical communication devices include a transmission unit that transmits, to the second optical communication device via the optical transmission path, an optical signal of a wavelength within a wavelength range for checking the transmission characteristics in the optical transmission path, and wherein an identification unit that identifies the transmission characteristics in the optical transmission path on the basis of the optical signal of the wavelength within the wavelength range transmitted from the one or more first optical communication devices is included.　

Description

Technical Field

[0001] The present invention relates to a communication system, a first optical communication device , second optical communication device and a method for specifying transmission path characteristics.

Background Art

[0002] With the spread of IoT (Internet of Things) and the progress of digitalization of society and industry, the amount of data flowing on the Internet is increasing. In addition, service use cases of a type different from the best-effort type have emerged. In order to improve such services, the requirements for bandwidth guarantee and low latency are increasing for communication networks. For example, in a cyber-physical system, uploading a huge amount of sensing data obtained from the real world (physical space) to an information processing infrastructure (digital space) without loss in real time, feeding back control information to the real world with high reliability and low latency, and transmitting high-definition images, etc. are required for the transport infrastructure. A cyber-physical system is a system that realizes optimal control of the real world by analyzing a huge amount of sensing data obtained from the real world on a computer and feeding back the analysis results. Creation of new values and solutions by such cyber-physical systems is expected.

[0003] Based on these, as a new architecture network for accommodating traffic that requires large capacity and low latency, the study of an all-photonics network (APN: All Photonics Network) based on photonics technology has been underway. APN is one of the transparent networks that transmit arbitrary user signals. APN provides an optical path end-to-end without depending on a specific communication protocol and optical modulation method.

[0004] However, a method for determining the integrity (continuity check) of the optical signal path that transparently transmits the main signals of various protocols in an APN has not yet been established. Hereinafter, determining the integrity of the optical signal path will be referred to as "signal path integrity determination." For example, if a communication anomaly occurs, in order to identify the location of the anomaly, the optical signal transmission path is divided, and signal path integrity determination (integrity monitoring) is performed for each divided section. In the signal path integrity determination for each section, the continuity of the optical signal is checked from one section to the other. Here, the continuity check is performed by photoelectric conversion (OE conversion) (hereinafter referred to as "OE conversion") of at least a portion of the optical signal at the endpoint of the section to be determined, terminating it and making a determination, or by using nonlinear optical effects related to that optical signal. Here, utilizing nonlinear optical effects means using the gain of a gain medium or light-absorbing medium, changes in the current or voltage applied to those mediums, changes in the intensity of pump light or gain-clamp light after it passes through the medium, and changes in light generated by nonlinear optical effects such as idler light. In signal path normality determination, the loopback method is mainly used, in which a request is made from one end of the target section and a response is folded back from the other end. In optical signal loopback, an OE conversion is required at one endpoint or beyond of the target section for optical signal path normality determination, where the requested optical signal is transmitted and the response is received, and at the other endpoint or beyond, where the optical signal is folded back in response to the request, an optical-electrical-optical conversion (hereinafter referred to as "OEO conversion") is required.

[0005] Figure 20 shows an example of the frequency of the control signal and the frequency of the main signal (user signal). In Figure 20, the control signal is the AMCC (Auxiliary Management and Control Channel) signal. In an APN, the photonic gateway (hereinafter referred to as "Ph-GW") within the station transmits the AMCC signal, which is frequency superimposed on the main signal, to user equipment and other devices that constitute the network, such as other Ph-GWs. User equipment and other devices that constitute the network, such as other Ph-GWs, may also transmit the AMCC signal, which is frequency superimposed on the main signal, to other user equipment and other devices that constitute the network, such as other Ph-GWs. Users and devices that constitute the network, such as other Ph-GWs, may also receive the AMCC signal.

[0006] Incidentally, generally, an optical transmitter (e.g., user equipment) and an optical receiver (e.g., Ph-GW) are connected via one or more repeaters. A repeater is a relay device that can switch its output destination according to the wavelength of the optical signal, such as a Wavelength Selective Switch (WSS). It is known that optical signals are affected by loss and bandwidth narrowing when passing through repeaters (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Yohei Sakamaki, Takeshi Kawai, and Mitsushi Fukutoku, "Optical Switch Technology for Realizing More Flexible Optical Nodes," NTT Technical Journal, November 2013. [Overview of the project] [Problems that the invention aims to solve]

[0008] Figure 21 is a diagram illustrating the effects on an optical signal as it passes through multiple repeaters. Figure 21 shows an example in which three repeaters 30-1 to 30-3 are provided between the optical transmitter 10 and the optical receiver 20. The middle section of Figure 21 shows the transmission characteristics of the WDM (Wavelength Division Multiplexing) filters provided by each of the repeaters 30-1 to 30-3. For example, the middle section of Figure 21 shows, from left to right, the transmission characteristics of the WDM filter provided by repeater 30-1, the transmission characteristics of the WDM filter provided by repeater 30-2, and the transmission characteristics of the WDM filter provided by repeater 30-3.

[0009] The lower section of Figure 21 shows the cumulative transmission characteristics. Note that in the lower section of Figure 21, the dotted line 40 indicates the individual transmission characteristics. As shown in Figure 21, it can be seen that the transmission characteristics narrow each time the optical signal passes through a repeater. This narrowing degrades the transmission characteristics. Therefore, understanding the transmission characteristics, which are a characteristic of the transmission path, is important.

[0010] Conventionally, the method for monitoring transmission path characteristics involved equipping the transmitting side with a broadband or tunable light source and the receiving side with an optical spectrum analyzer to identify the wavelengths being transmitted. However, because optical spectrum analyzers are expensive measuring instruments, there was a problem in that it was not possible to easily determine the transmission characteristics, which are the characteristics of the transmission path between the optical transmitter and optical receiver, using a less expensive configuration. This problem is not limited to optical transmitters and optical receivers in APNs, but is common to optical communication systems in general that transmit and receive optical signals.

[0011] In view of the above circumstances, the present invention aims to provide a communication system, a first optical communication device, and a method for determining transmission path characteristics that can easily determine transmission characteristics, which are characteristics of the transmission path between an optical transmitter and an optical receiver, with a less expensive configuration. [Means for solving the problem]

[0012] One aspect of the present invention is a communication system comprising one or more first optical communication devices, a second optical communication device that communicates with the one or more first optical communication devices, and an optical transmission path connecting the one or more first optical communication devices and the second optical communication device, wherein the one or more first optical communication devices includes a transmitting unit that transmits an optical signal with a wavelength within a wavelength range for confirming the transmission characteristics of the optical transmission path to the second optical communication device via the optical transmission path, and a identifying unit that identifies the transmission characteristics of the optical transmission path based on the optical signal with a wavelength within the wavelength range transmitted from the one or more first optical communication devices.

[0013] One aspect of the present invention is a first optical communication device in a communication system comprising a first optical communication device, a second optical communication device that communicates with the first optical communication device, and an optical transmission path connecting the first optical communication device and the second optical communication device, the first optical communication device comprising: a transmitting unit that transmits an optical signal with a swept wavelength to the second optical communication device via the optical transmission path; and a identifying unit that receives either the reception result of the swept wavelength optical signal or an optical signal folded back from the second optical communication device and identifies the transmission characteristics in the optical transmission path.

[0014] One aspect of the present invention is a transmission path characteristic identification method for a communication system comprising one or more first optical communication devices, a second optical communication device that communicates with the one or more first optical communication devices, and an optical transmission path connecting the one or more first optical communication devices and the second optical communication device, wherein the one or more first optical communication devices transmit an optical signal with a wavelength within a wavelength range for confirming the transmission characteristics of the optical transmission path to the second optical communication device via the optical transmission path, and an identification unit identifies the transmission characteristics of the optical transmission path based on the optical signal with a wavelength within the wavelength range transmitted from the one or more first optical communication devices. [Effects of the Invention]

[0015] This invention makes it possible to easily determine the transmission characteristics, which are the characteristics of the transmission path between an optical transmitter and an optical receiver, using a less expensive configuration.

Brief Description of the Drawings

[0016] [Figure 1] It is a diagram showing a configuration example of a communication system in the first embodiment. [Figure 2] It is a diagram showing an example of an optical signal transmitted by an optical transmitter in the first embodiment. [Figure 3] It is a diagram showing the flow of the conduction confirmation process of the wavelength channel width performed by the communication system in the first embodiment. [Figure 4] It is a diagram showing an example of an optical signal transmitted by an optical transmitter when the optical signal transmitted by the optical transmitter is a modulated optical signal. [Figure 5] It is a diagram showing a configuration example of a communication system in the second embodiment. [Figure 6] It is a diagram showing the flow of the conduction confirmation process of the wavelength channel width performed by the communication system in the second embodiment. [Figure 7] It is a diagram showing a configuration example of a communication system in the third embodiment. [Figure 8] It is a diagram showing the flow of the conduction confirmation process of the wavelength channel width performed by the communication system in the third embodiment. [Figure 9] It is a diagram showing a configuration example of a communication system that communicates using a communication network such as an all-optical network (APN). [Figure 10] It is a diagram showing a configuration example (Part 1) of a communication system in the fourth embodiment. [Figure 11] It is a supplementary explanatory diagram of the configuration when using AMCC as in the communication system in the fourth embodiment. [Figure 12] It is a diagram showing a configuration example (Part 2) of a communication system in the fourth embodiment. [Figure 13] It is a diagram showing a configuration example (Part 3) of a communication system in the fourth embodiment. [Figure 14] It is a diagram showing a configuration example (Part 4) of a communication system in the fourth embodiment. [Figure 15]This figure shows an example of the configuration of the communication system in modified example 7 of the fourth embodiment. [Figure 16] This figure shows an example of the configuration of the communication system in the fifth embodiment. [Figure 17] This figure shows an example of the configuration of a communication system in a modified example 6 of the fifth embodiment. [Figure 18] This figure shows an example of the configuration of the communication system in the sixth embodiment. [Figure 19] This figure shows an example of the hardware configuration of a communication system in an embodiment. [Figure 20] This diagram shows an example of the relationship between the frequency of the control signal and the frequency of the main signal (user signal). [Figure 21] This diagram illustrates the effects that an optical signal experiences when passing through multiple repeaters. [Modes for carrying out the invention]

[0017] One embodiment of the present invention will be described below with reference to the drawings.

[0018] (overview) The communication system in this invention is a system for identifying transmission characteristics, which are characteristics of the transmission path between an optical transmitter and an optical receiver. Here, identifying transmission characteristics means confirming the width of the wavelength channel (wavelength tunnel) that can be transmitted through the transmission path. The optical transmitter and optical receiver in the communication system share information indicating wavelength (hereinafter referred to as "swept wavelength information"), for example, by time synchronization or message exchange.

[0019] The optical receiver notifies the optical transmitter whether or not it can receive the optical signal at each wavelength. This allows the transmission characteristics to be determined. For example, the bandwidth of the wavelength channel (wavelength tunnel) that can be received by the optical receiver can be determined by performing a wavelength sweep of the wavelength of one light source provided by the first optical communication device (corresponding to an optical transmitter or optical transceiver) according to the width of the wavelength channel to be checked for continuity, and then checking for continuity at each wavelength of the optical signal, or by checking for continuity at each optical signal of multiple first optical communication devices (corresponding to optical transmitters or optical transceivers) corresponding to wavelengths obtained by dividing the wavelength channel width to be checked by multiple light sources. The sweep width may be the width of the wavelength channel to be checked minus the modulation sideband on one side of the modulation. Furthermore, the timing for determining the transmission characteristics may be performed during the initial setup when the main signal is not transmitted, or during loopback. Here, loopback is a method used in signal path normality determination as described above.

[0020] The sweeping status can be identified and confirmed using one of the following methods (1) to (4). (1) The optical transmitter notifies the optical receiver of the sweep status, and the conduction width is confirmed based on the conduction strength corresponding to the notification. (2) The optical receiver is synchronized with the optical receiver, and the sweep speed, sweep start wavelength, and sweep start time are shared. The conduction width is then determined based on the conduction strength at the time after the propagation delay from the start time. (3) The optical receiver notifies the receiver of the reception confirmation according to the conduction strength, and the optical transmitter confirms the conduction width based on the reception confirmation. The reception notification may be a notification that includes strength information, or it may be a return signal with an intensity corresponding to the signal strength received by the opposing device. The received light may also be folded back as is. However, if the received light is folded back as is, the characteristics that are narrowed in the round trip will be observed. (4) When notification is made using an optical signal with a wavelength different from the wavelength of the light being swept, wavelength sweeping can be done with CW (Continuous Wave) light. When notification is made using the light being swept, at least the portion carrying the notification will be modulated light. The following describes the specific configuration required to implement the process for identifying the transparency characteristics mentioned above.

[0021] (First Embodiment) In the first embodiment, a configuration is described in which the optical receiver identifies the transmission characteristics of the transmission path between the optical transmitter and the optical receiver in a communication system comprising an optical transmitter and an optical receiver. More specifically, in the first embodiment, the optical transmitter transmits optical signals of each wavelength while sweeping the wavelength of the light source, and the optical receiver converts the optical signals of each wavelength into electrical signals, measures the received intensity, identifies which wavelength is being transmitted, and determines the conduction width.

[0022] Figure 1 shows an example configuration of the communication system 1 in the first embodiment. The communication system 1 comprises an optical transmitter 10 and an optical receiver 20. The optical transmitter 10 and the optical receiver 20 are connected via a transmission path 35. The transmission path 35 is the path to be measured for transmission characteristics. Note that multiple optical transmitters 10 and optical receivers 20 may be provided.

[0023] If the communication system 1 is equipped with multiple optical transmitters 10, each optical transmitter 10 may emit a single fixed wavelength optical signal within the wavelength range to be checked for continuity, or a sweep width may be defined for each optical transmitter 10. If each optical transmitter 10 emits a single fixed wavelength optical signal within the wavelength range to be checked for continuity, then the number of optical transmitters 10 required will be sufficient to cover the wavelength range to be checked for continuity.

[0024] The optical transmitter 10 comprises a wavelength sweep instruction unit 11 and a light source 12. The wavelength sweep instruction unit 11 instructs the light source 12 to sweep the wavelength channel to be checked for continuity. The light source 12 is a tunable light source whose wavelength can be changed. The light source 12 transmits optical signals of each wavelength included in the sweep width instructed by the wavelength sweep instruction unit 11 in a predetermined order, for example, ascending, descending, or randomly. That is, the light source 12 transmits optical signals with swept wavelengths according to the instructions from the wavelength sweep instruction unit 11. The light source 12 may also transmit optical signals of each wavelength without modulation. The optical transmitter 10 is one embodiment of a first optical communication device. The light source 12 is one embodiment of a transmitting unit.

[0025] The optical receiver 20 comprises a receiving unit 21 and a wavelength sweep identification unit 22. The receiving unit 21 receives optical signals of each wavelength transmitted from the optical transmitter 10. The receiving unit 21 includes a receiver that is sufficiently wavelength-independent at the wavelength to be measured for transmission characteristics. An example of a wavelength-independent receiver is a photodiode equipped with a wavelength filter. For example, in the 1500 nm band, a photodiode made of InGaAs, a semiconductor material with a bandgap corresponding to the desired wavelength and which exhibits small changes with wavelength, is a candidate. Note that wavelength dependence may be compensated for by multiplying by a multiplier corresponding to the specified wavelength or by changing the bias, thereby effectively making it independent. The receiving unit 21 converts the received optical signal into an electrical signal and then measures the received intensity. The receiving unit 21 identifies the conduction width based on the measurement result and the information held by the wavelength sweep identification unit 22. The optical receiver 20 is one embodiment of a second optical communication device. The receiving unit 21 is one embodiment of a identification unit.

[0026] The wavelength sweep identification unit 22 stores sweep wavelength information obtained in advance through message exchange between the optical transmitter 10 and the optical receiver 20. The sweep wavelength information includes at least information that identifies the wavelength to be swept.

[0027] Figure 2 shows an example of an optical signal transmitted by the optical transmitter 10 in the first embodiment. As shown in Figure 2, the optical transmitter 10 transmits an optical signal corresponding to the swept wavelength to the optical receiver 20 by sweeping the wavelength. For example, as shown in Figure 2, if the wavelength channel to be checked is indicated by the wavelength sweep identification unit 22, the optical transmitter 10 should transmit an optical signal while sweeping the wavelength with a width equal to or slightly wider than the width of the wavelength channel to be checked. This makes it possible to check the continuity of at least the width of the wavelength channel to be checked. Note that the continuity check may also include checking the wavelength dependence of the loss in the transmission path (which may include a relay device) between the optical transmitter 10 and the optical receiver 20.

[0028] Figure 3 shows the flow of the wavelength channel width continuity confirmation process performed by the communication system 1 in the first embodiment. In Figure 3, the process is described in the case where the optical transmitter 10 and the optical receiver 20 share swept wavelength information through message exchange. The process in Figure 3 is performed, for example, during initial setup when the main signal is not conducting, or during continuity confirmation.

[0029] The optical transmitter 10 and the optical receiver 20 share swept wavelength information through message exchange (step S101). Specifically, the optical transmitter 10 shares the swept wavelength information by sending a message containing the swept wavelength information to the optical receiver 20. Here, the swept wavelength information includes information indicating which wavelength of optical signal the optical transmitter 10 will transmit. The wavelength sweep instruction unit 11 instructs the light source 12 to sweep the wavelength channel to be checked. For example, the wavelength sweep instruction unit 11 instructs the light source 12 to sweep the wavelength channel along with information on the sweep width of the wavelength channel to be checked.

[0030] The sweep wavelength information may be a combination of the transmission start time, the transmission start wavelength, the wavelength change per unit time, and the transmission end wavelength; or a combination of the transmission start time, the transmission start wavelength, the wavelength change per unit time, and the sweep end time; or a combination of the transmission start time, the transmission start wavelength, the wavelength change per unit time, and the sweep width; or the time from instruction to transmission start, the wavelength change per unit time, and the sweep end time or sweep width may be predetermined between the optical transmitter 10 and the optical receiver 20, and the information may be the transmission start wavelength, the center wavelength of the sweep, or the wavelength channel to be checked (equivalent to (2) of the sweep status). Also, although it deviates from the flow in Figure 3, the transmission wavelength may be instructed, the transmission wavelength corresponding to the instruction is transmitted, the received intensity is measured, then the transmission wavelength is changed and instructed, the received intensity is measured, and this is repeated until all the wavelength widths to be checked are measured (equivalent to (1) of the sweep status). Furthermore, although Figure 3 shows the conduction width being identified by the optical receiver 20, the reception result may also be transmitted to the optical transmitter 10 from the receiving side (e.g., the optical receiver 20) via message exchange, and identified on the optical transmitter 10 side (corresponding to sweep status (3)). The sweep status can be identified and confirmed using any of the methods (1) to (4) described above.

[0031] The light source 12, in accordance with the instructions from the wavelength sweep instruction unit 11, transmits an optical signal of each wavelength to the optical receiver 20 via the transmission line 35 while sweeping the wavelength to be checked based on the sweep width information (step S102). For example, the light source 12 repeatedly emits light within the wavelength range defined by the sweep width while continuously changing the laser wavelength at a predetermined sweep speed. However, unless there is a reason to reduce errors, the light source 12 may transmit an optical signal only once for each wavelength instead of repeatedly emitting light within the wavelength range defined by the sweep width.

[0032] The receiving unit 21 of the optical receiver 20 receives optical signals of each wavelength transmitted from the optical transmitter 10. Each time the receiving unit 21 receives an optical signal, it converts the received optical signal into an electrical signal and measures the received intensity (step S103). For example, the optical transmitter 10 transmits from wavelength λ1 to wavelength λ 10 When repeatedly transmitting an optical signal in the wavelength range up to λ1, the receiving unit 21 receives signals from wavelength λ1 to wavelength λ 10 The optical signals at each wavelength up to a certain point are converted into electrical signals, and the received intensity is measured.

[0033] The receiving unit 21 identifies the conduction width based on the swept wavelength information held by the wavelength sweep identification unit 22 and the measured received intensity (step S104). Specifically, the receiving unit 21 determines that if a received intensity of a predetermined threshold or higher is obtained, the optical signal of the wavelength for which a received intensity of a threshold or higher is obtained is receivable. Alternatively, the receiving unit 21 may measure the wavelength-dependent loss for each received optical signal and identify the conduction width based on the received intensity and wavelength-dependent loss. For example, the receiving unit 21 determines that an optical signal of a wavelength where the wavelength-dependent loss is less than the threshold and the received intensity is above the threshold is receivable. On the other hand, the receiving unit 21 determines that an optical signal of a wavelength where the wavelength-dependent loss is above the threshold or the received intensity is below the threshold is unreceivable.

[0034] On the other hand, the receiving unit 21 determines that if it obtains a reception intensity below a predetermined threshold, the optical signal for the wavelength for which the reception intensity is below the threshold is unreceivable. The threshold is determined for each wavelength. The receiving unit 21 performs this process for all optical signals of each wavelength transmitted from the optical transmitter 10. The receiving unit 21 then identifies the range of wavelengths that it has determined to be receivable as the conduction width.

[0035] With the communication system 1 configured as described above, it becomes possible to easily determine the transmission characteristics, which are the characteristics of the transmission path between the optical transmitter and the optical receiver, using a less expensive configuration. Specifically, in the communication system 1, the optical receiver 20 converts the received optical signal into an electrical signal and determines the conduction width based on the received intensity of the electrical signal and the swept wavelength information. In this way, the transmission characteristics, which are the characteristics of the transmission path, can be determined even if the optical receiver 20 does not have an optical spectrum analyzer. Therefore, it becomes possible to easily determine the transmission characteristics, which are the characteristics of the transmission path between the optical transmitter and the optical receiver, using a less expensive configuration.

[0036] (Modification 1 of the first embodiment) The optical transmitter 10 may modulate and transmit optical signals of each wavelength. In this configuration, the optical transmitter 10 includes a modulation unit for modulating the optical signal. When the optical signal transmitted by the optical transmitter 10 is a modulated optical signal, the optical transmitter 10 may transmit the optical signal by wavelength sweeping over a wavelength range with a width equal to the width of the wavelength channel to be checked minus one of the modulation sidebands, as shown in Figure 4. Figure 4 shows an example of an optical signal transmitted by the optical transmitter 10 when the optical signal transmitted by the optical transmitter 10 is a modulated optical signal. By configuring it in this way, the sweep width can be reduced. Furthermore, when modulating and transmitting optical signals of each wavelength, messages can be exchanged. However, when exchanging messages, the spread and depth of the modulation sidebands change depending on the content of the message. Therefore, it is desirable to continue the measurement for each wavelength for a time that includes a message that can be considered random on a time average, or to transmit random data that can be considered random in addition to the message.

[0037] As described above, from the perspective of reducing the sweep width, when the optical transmitter 10 modulates optical signals of each wavelength, it is desirable to use steep modulation or random modulation so that there are wide frequency components. For example, when modulated with a single sine wave, the main sidebands consist of only one ±1st order modulation sideband on each side of the carrier wave, with a width equal to the frequency fluctuation of the sine wave, resulting in gaps. From the perspective of increasing the sensitivity of conduction in the modulated component, it is desirable for the modulation sidebands to be deep. It is also acceptable for the modulation to be deep enough that the unmodulated component disappears.

[0038] (Modification 2 of the first embodiment) When time synchronization is performed between the optical transmitter 10 and the optical receiver 20, the sweep wavelength information may include information on the sweep speed, the sweep start wavelength, and the sweep start time. In this configuration, the receiving unit 21 of the optical receiver 20 compares the sweep start time included in the sweep wavelength information with the time of reception of the optical signal to identify the wavelength of the received optical signal (corresponding to sweep status (2)).

[0039] (Second Embodiment) In the second embodiment, a configuration is described in which the optical transmitter determines the transmission characteristics of the transmission path between the optical transmitter and the optical receiver in a communication system comprising an optical transmitter and an optical receiver. More specifically, in the second embodiment, the optical transmitter transmits optical signals of each wavelength while sweeping the wavelength of the light source, and the optical receiver determines the conduction width by transmitting information to the optical transmitter as a response indicating whether the optical signal was successfully received or not.

[0040] Figure 5 shows an example configuration of the communication system 1a in the second embodiment. The communication system 1a comprises an optical transmitter 10a and an optical receiver 20a. The optical transmitter 10a and the optical receiver 20a are connected via a transmission line 35. Note that multiple optical transmitters 10a and optical receivers 20a may be provided.

[0041] If the communication system 1a is equipped with multiple optical transmitters 10a, each optical transmitter 10a may emit a single fixed wavelength optical signal within the wavelength range to be checked for continuity, or a sweep width may be defined for each optical transmitter 10a. If each optical transmitter 10a emits a single fixed wavelength optical signal within the wavelength range to be checked for continuity, then the number of optical transmitters 10a required will be sufficient to cover the wavelength range to be checked for continuity.

[0042] The optical transmitter 10a comprises a wavelength sweep indicator unit 11, a light source 12, and a response receiving unit 13. The optical transmitter 10a differs from the optical transmitter 10 in that it newly includes a response receiving unit 13. The other components of the optical transmitter 10a are the same as those of the optical transmitter 10.

[0043] The response receiving unit 13 receives the optical signal transmitted from the optical receiver 20a. The optical signal transmitted from the optical receiver 20a contains information on whether reception was successful or unsuccessful for each wavelength of optical signal swept by the light source 12. The optical transmitter 10a can determine the conduction width based on the wavelength information of the optical signal successfully received by the optical receiver 20a. The response receiving unit 13 is one embodiment of the identification unit.

[0044] The optical receiver 20a comprises a receiving unit 21 and a response unit 23. The optical receiver 20a differs from the optical receiver 20 in that it does not have a wavelength sweep identification unit 22, but does have a response unit 23. The other components of the optical receiver 20a are the same as those of the optical receiver 20. Note that the optical receiver 20a may be equipped with a wavelength sweep identification unit 22 if wavelength dependence needs to be compensated for and identified.

[0045] The response unit 23 transmits a response to the optical transmitter 10a, based on the optical signal received by the receiving unit 21, which includes information indicating either successful or unsuccessful reception for each wavelength of optical signal. The method for determining whether reception is successful or unsuccessful can be based on the received signal strength, as in the first embodiment.

[0046] Figure 6 shows the flow of the wavelength channel width continuity confirmation process performed by the communication system 1a in the second embodiment. In Figure 6, the process is described in the case where the sweep wavelength information is shared between the optical transmitter 10a and the optical receiver 20a by message exchange. The process in Figure 6 is performed, for example, during initial setup when the main signal is not conducting, or during continuity confirmation.

[0047] The optical transmitter 10a and the optical receiver 20a share sweep wavelength information through message exchange (step S201). Specifically, the optical transmitter 10a shares sweep wavelength information by sending a message containing the sweep wavelength information to the optical receiver 20a. If the optical receiver 20a is the entity that confirms the conduction width, the optical receiver 20a shares the sweep wavelength information by sending the sweep wavelength information to the optical transmitter 10a. However, if the optical transmitter 10a is the one that determines the conduction width, message exchange to share sweep wavelength information may be performed.

[0048] The wavelength sweep instruction unit 11 of the optical transmitter 10a instructs the light source 12 to sweep the wavelength channel to be checked. For example, the wavelength sweep instruction unit 11 instructs the light source 12 to sweep the wavelength channel along with information on the sweep width of the wavelength channel to be checked. The light source 12, in accordance with the instruction from the wavelength sweep instruction unit 11 and based on the sweep width information, sweeps the wavelength to be checked and transmits the optical signal for each wavelength to the optical receiver 20a via the transmission line 35 (step S202).

[0049] The receiving unit 21 of the optical receiver 20a receives optical signals of each wavelength transmitted from the optical transmitter 10a. Each time the receiving unit 21 receives an optical signal, it converts the received optical signal into an electrical signal and measures the received intensity (step S203). Based on the measured received intensity, the receiving unit 21 determines whether the reception of each wavelength of optical signal has been successful or unsuccessful. Specifically, the receiving unit 21 determines that if a received intensity of a wavelength equal to or greater than a predetermined threshold is obtained, the optical signal of the wavelength for which a received intensity equal to or greater than the threshold is receivable. The receiving unit 21 may also measure the wavelength-dependent loss for each received optical signal and determine the conduction width based on the received intensity and wavelength-dependent loss. For example, the receiving unit 21 determines that an optical signal of a wavelength where the wavelength-dependent loss is less than the threshold and the received intensity is equal to or greater than the threshold is receivable. On the other hand, the receiving unit 21 determines that an optical signal of a wavelength where the wavelength-dependent loss is equal to or greater than the threshold, or where the received intensity is less than the threshold, is unreceivable.

[0050] The receiving unit 21 outputs the determination result to the response unit 23. The response unit 23 generates a response containing information on whether or not the signal can be received for each wavelength of optical signal, according to the determination result output from the receiving unit 21 (step S204). The response unit 23 transmits the generated response to the optical transmitter 10a via the transmission line 35 (step S205).

[0051] The response receiving unit 13 of the optical transmitter 10a receives the response transmitted from the optical receiver 20a. The response receiving unit 13 determines the conduction width based on the information regarding receivability included in the received response (step S206). Specifically, the response receiving unit 13 determines the range of wavelengths that have been indicated as receivable as the conduction width.

[0052] In the communication system 1a configured as described above, the optical receiver 20a notifies the optical transmitter 10a of a response indicating whether or not each optical signal of each wavelength transmitted by the optical transmitter 10a can be received, and the optical transmitter 10a determines the conduction width. In this way, the transmission characteristics, which are characteristics of the transmission path, can be determined even if the optical receiver 20a does not have an optical spectrum analyzer. Therefore, it becomes possible to easily determine the transmission characteristics, which are characteristics of the transmission path between the optical transmitter and the optical receiver, with a less expensive configuration.

[0053] (Modification 1 of the second embodiment) The optical transmitter 10a may modulate and transmit optical signals of each wavelength. In this configuration, the optical transmitter 10a includes a modulation unit for modulating the optical signal. When the optical signal transmitted by the optical transmitter 10a is a modulated optical signal, the optical transmitter 10a may, as in the first embodiment, transmit the optical signal by wavelength sweeping over a wavelength range with a width obtained by subtracting one of the modulation sidebands from the width of the wavelength channel to be checked for continuity. This configuration reduces the sweep width. Furthermore, when transmitting optical signals of each wavelength, messages can be exchanged. However, when messages are exchanged, the spread and depth of the modulation sidebands change depending on the content of the message. Therefore, it is desirable to continue the measurement for each wavelength for a time that includes a message that can be considered random on a time-averaged basis, or to transmit random data that can be considered random in addition to the message.

[0054] As described above, from the perspective of reducing the sweep width, when the optical transmitter 10a modulates optical signals of each wavelength, it is desirable to use steep modulation or random modulation so that there are wide frequency components. For example, when modulating with a single sine wave, there are only one modulation sideband on each side, which is the width of the frequency fluctuation of the sine wave, so gaps are created. From the perspective of increasing the sensitivity of conduction in the modulated component, it is desirable for the modulation sidebands to be deep. It is also acceptable for the modulation to be deep enough that the unmodulated component disappears.

[0055] (Modification 2 of the second embodiment) When time synchronization is performed between the optical transmitter 10a and the optical receiver 20a, the sweep wavelength information may include information on the sweep speed, the sweep start wavelength, and the sweep start time. In this configuration, the receiving unit 21 of the optical receiver 20a compares the sweep start time included in the sweep wavelength information with the time of reception of the optical signal to identify the wavelength of the received optical signal (corresponding to sweep status (2)).

[0056] (Modification 3 of the second embodiment) In the example described above, the optical receiver 20a is configured to transmit information to the optical transmitter 10a as a response indicating whether the optical signal was successfully received or not. In addition to transmitting information on whether the optical signal was successfully received or not, the optical receiver 20a may also transmit information on the received signal strength to the optical transmitter 10a as a response. In this configuration, the response receiving unit 13 of the optical transmitter 10a performs the same determination as the optical receiver 20a. For example, the response receiving unit 13 determines whether or not optical signals of each wavelength can be received based on the received signal strength information. The response receiving unit 13 then identifies the range of wavelengths that it has determined can be received as the conduction width. As a result, if the optical receiver 20a or optical transmitter 10a is wavelength-dependent, there is no need to transmit wavelength information to the optical receiver 20a.

[0057] (Third embodiment) In the third embodiment, a configuration is described in which the optical transmitter identifies the transmission characteristics of the transmission path between the optical transceiver and the optical receiver in a communication system comprising an optical transceiver and an optical receiver. More specifically, in the third embodiment, the optical transceiver transmits optical signals of each wavelength while sweeping the wavelength of the light source, a refolding device refolds (reflects) the optical signals transmitted from the optical transceiver as light, and the optical transceiver identifies which wavelength is being transmitted and determines the conduction width by receiving the optical signals folded back by the refolding device.

[0058] Figure 7 shows an example configuration of the communication system 1b in the third embodiment. The communication system 1b comprises an optical transceiver 15 and a loopback device 18. The optical transceiver 15 and the loopback device 18 are connected via a transmission line 35. Note that multiple optical transceivers 15 and loopback devices 18 may be provided.

[0059] The optical transceiver 15 comprises a wavelength sweep instruction unit 11, a light source 12, a response receiving unit 13, and a wavelength sweep identification unit 14. The optical transceiver 15 differs from the optical transmitter 10 in that it newly includes a response receiving unit 13 and a wavelength sweep identification unit 14. The other components of the optical transceiver 15 (for example, the wavelength sweep instruction unit 11 and the light source 12) are the same as those of the optical transmitter 10. The optical transceiver 15 is one embodiment of the first optical communication device.

[0060] The response receiving unit 13 receives the optical signal that has been folded back by the folding device 18. The response receiving unit 13 determines the conduction width based on the received optical signal and the information held by the wavelength sweep identification unit 14.

[0061] The wavelength sweep identification unit 14 holds the sweep wavelength information instructed by the wavelength sweep instruction unit 11 to the light source 12. The sweep wavelength information includes at least information that identifies the wavelength to be swept.

[0062] The refraction device 18 includes a reflection and transmission section 24. The refraction device 18 differs in configuration from the optical receiver 20 in that it does not include a receiving section 21 and a wavelength sweep identification section 22, but does include a reflection and transmission section 24. The refraction device 18 is one embodiment of a second optical communication device.

[0063] The reflection-transmission unit 24 switches its operating mode in response to a re-folding instruction from another device. If no instruction to re-fold the optical signal is received from another device, the reflection-transmission unit 24 transmits the optical signal (user signal) transmitted from the optical transceiver 15. In this case, the re-folding device 18 processes the optical signal transmitted from the optical transceiver 15 internally or outputs it externally. The other device may be the optical transceiver 15, or it may be a control device (not shown) that manages and controls the optical transceiver 15 and the re-folding device 18 in the communication system 1b (for example, wavelength allocation).

[0064] If instructed by another device to fold back the optical signal, the reflection-transmission unit 24 folds back the optical signal transmitted from the optical transceiver 15 to the optical transceiver 15 as is. In other words, the reflection-transmission unit 24 performs loopback for all channels. That is, the reflection-transmission unit 24 folds back the loopback signal to the optical transceiver 15 without changing any of the bits in the bit sequence of the received loopback signal. In other words, the reflection-transmission unit 24 reflects the optical signal transmitted from the optical transceiver 15. For example, the reflection-transmission unit 24 is a half-mirror.

[0065] The fact that the optical signal is folded back without modulation is the closest to full-channel loopback among the three loopback mechanisms for "Layer 1" maintenance in the "JT-I430" standard. The three loopback mechanisms are (1) full-channel loopback, (2) partial loopback, and (3) logical loopback. In full-channel loopback, the optical signal is folded back to the transmitting station (in this case, optical transceiver 15) without any change to the entire bit sequence. The fact that the optical signal is folded back without modulation differs in several ways from "Layer 1" in the "JT-I430" standard.

[0066] First, the turning point is not near the "T" reference point within "NT1," but rather far away. Therefore, it is not "Loop 2."

[0067] Furthermore, APNs contain signals that are not treated as bit sequences (analog signals, etc.), in which case the communication device cannot send back the bit sequence. However, if the information is sent back as is, even if the bit sequence cannot be sent back, then this point (difference) can be ignored.

[0068] Furthermore, if the reflectivity differs between wavelength-dependent and polarization-dependent elements, the optical signal is not simply sent back without modulation. Modulating, amplifying, or attenuating a portion of the optical signal in at least one of the time domain or frequency domain and then folding the signal back can be considered equivalent to "(2) partial loopback" or "(3) logical loopback." In partial loopback, the received bit sequence of one or more specified channels is sent back to the transmitting station unchanged. Therefore, if the modulation frequency is considered a channel, then partially modulating and folding back an optical signal is similar to partial loopback, because there may be certain changes in the folded-back information. Also, modulating and folding back an optical signal is similar to logical loopback.

[0069] Each of the three loopback mechanisms can be further classified into (a) transparent loopback and (b) opaque loopback. This classification concerns the signal transmitted beyond the loopback point without being folded back during the loopback process. Thus, "(a) transparent loopback" and "(b) opaque loopback" can be realized by reflecting some of the optical signal while transmitting the remaining optical signal. In "(a) transparent loopback," the signal transmitted beyond the folding point (forward signal) and the received signal at the folding point are the same. In "(b) opaque loopback," the signal transmitted beyond the folding point (forward signal) and the received signal at the folding point are the same. However, it is mainly assumed that the optical signal will not be transmitted. The received signal may be amplified, or modulation (on / off modulation, intensity modulation, polarization modulation, etc.) performed on the received signal may be performed on the optical signal.

[0070] The method for switching between reflecting or transmitting the optical signal transmitted from the optical transceiver 15 is not limited to a specific method. For example, the reflection-transmission unit 24 may switch between reflecting or transmitting the optical signal (on and off aliasing) by the reflection-transmission unit 24 by inserting and removing the optical fiber connected to the reflection-transmission unit 24, utilizing Fresnel reflection at the endpoint of the optical fiber.

[0071] Figure 8 shows the flow of the wavelength channel width continuity confirmation process performed by the communication system 1b in the third embodiment. In Figure 8, the case where swept wavelength information is shared between the optical transceiver 15 and the loopback device 18 by message exchange is described. When swept wavelength information is shared by message exchange, it is suitable when the characteristics of the reflection transmission section 24 (e.g., half mirror) or the reflection method are changed according to the wavelength. It is also possible that the swept wavelength information is not shared. If the swept wavelength information is not shared, the loopback setting is made in advance on the loopback device 18 side before the process in Figure 8 is executed. The process in Figure 8 is executed, for example, during initial setup when the main signal is not conducted or during continuity confirmation.

[0072] The optical transceiver 15 and the refraction device 18 share swept wavelength information through message exchange (step S301). In the third embodiment, when the refraction device refolds the optical signal transmitted from the optical transceiver as light, a message exchange regarding reflection instructions takes place between the optical transceiver 15 and the refraction device 18. Specifically, the optical transceiver 15 sends a message to the refraction device 18 in advance, which includes instructions for the refraction device 18 to perform reflection, and this message exchange takes place in this manner. The message may also include instructions regarding modulation during reflection, wavelength-dependent reflection, etc. As described above, if swept wavelength information is not shared, the processing in step S301 is not necessary.

[0073] The wavelength sweep instruction unit 11 of the optical transceiver 15 instructs the light source 12 to sweep the wavelength channel to be checked. For example, the wavelength sweep instruction unit 11 instructs the light source 12 to sweep the wavelength channel along with information on the sweep width of the wavelength channel to be checked. Furthermore, the wavelength sweep instruction unit 11 outputs the swept wavelength information to the wavelength sweep identification unit 14. The light source 12, in accordance with the instruction from the wavelength sweep instruction unit 11 and based on the sweep width information, sweeps the wavelength to be checked and transmits the optical signal of each wavelength to the loopback device 18 via the transmission path 35 (step S302).

[0074] The reflection-transmission section 24 of the refraction device 18 refolds the optical signals of each wavelength transmitted from the optical transceiver 15 while keeping them as light (step S303). The reflection-transmission section 24 of the refraction device 18 folds the optical signals of each wavelength transmitted from the optical transceiver 15 back to the refraction device 18.

[0075] The response receiving unit 13 of the aliasing device 18 receives optical signals of each wavelength that have been aliased by the aliasing device 18. Each time the response receiving unit 13 receives an optical signal, it converts the received optical signal into an electrical signal and measures the received intensity (step S304). The response receiving unit 13 identifies the conduction width based on the measured received intensity and the swept wavelength information output from the wavelength sweep identification unit 14 (step S305).

[0076] In the communication system 1b configured as described above, optical signals of each wavelength transmitted from the optical transceiver 15 are folded back by the folding device 18 while remaining as optical signals and received by the optical transceiver 15. In this configuration, the product of the widths in both directions can be determined. The optical transceiver 15 determines the conduction width based on the optical signal folded back by the folding device 18 and the swept wavelength information held by the device itself. In this way, the transmission characteristics, which are characteristics of the transmission path, can be determined even if the folding device 18 does not have an optical spectrum analyzer. Therefore, it becomes possible to easily determine the transmission characteristics, which are characteristics of the transmission path between the optical transmitter and the optical receiver, with a less expensive configuration.

[0077] (Modification 1 of the third embodiment) The optical transceiver 15 may modulate and transmit optical signals of each wavelength. In this configuration, the optical transceiver 15 includes a modulation unit for modulating the optical signal. When the optical signal transmitted by the optical transceiver 15 is a modulated optical signal, the optical transceiver 15 may, as in the first embodiment, transmit the optical signal by wavelength sweeping over a wavelength range with a width obtained by subtracting one of the modulation sidebands from the width of the wavelength channel to be checked for continuity. This configuration reduces the sweep width. Furthermore, when modulating and transmitting optical signals of each wavelength, messages can be exchanged. However, when exchanging messages, the spread and depth of the modulation sidebands change depending on the content of the message. Therefore, it is desirable to continue the measurement for each wavelength for a time that includes messages that can be considered random on a time-averaged basis, or to transmit random data that can be considered random in addition to the message.

[0078] As described above, from the perspective of reducing the sweep width, when the optical transceiver 15 modulates optical signals of each wavelength, it is desirable to use steep modulation or random modulation so that there are wide frequency components. For example, when modulating with a single sine wave, there are only one modulation sideband on each side, which is the width of the frequency fluctuation of the sine wave, so gaps are created. From the perspective of increasing the sensitivity of conduction in the modulated component, it is desirable for the modulation sidebands to be deep. It is also acceptable for the modulation to be deep enough that there is no unmodulated component.

[0079] (Fourth Embodiment) In the fourth embodiment, a configuration in which the configurations shown in the first to third embodiments are applied to the APN will be described. In the fourth embodiment, the user device transmits optical signals of each wavelength while sweeping the wavelength of the light source, and the Ph-GW converts the optical signals of each wavelength into electrical signals, measures the received intensity of the electrical signals, identifies which wavelengths are being transmitted, and determines the conduction width. In the following description, the direction from the user device to the Ph-GW will be described as the upstream direction, and the direction from the Ph-GW to the user device will be described as the downstream direction. In the fourth embodiment, the conduction width in the upstream direction will be determined.

[0080] (Basic APN configuration example) Because APN employs a flat architecture, it eliminates the need for electrical termination of optical signals between layers in communication networks used as a comparative example with APN. In APN, latency is extremely low due to end-to-end optical path connectivity. Furthermore, APN offers high flexibility and scalability, enabling the easy provision of high-capacity, low-latency communication networks on a functional basis, without depending on a specific communication protocol.

[0081] APN includes two types of optical nodes, a photonic gateway (Ph-GW) and a photonic exchange (hereinafter referred to as "Ph-EX"), as optical nodes that minimize electrical processing such as switching, multiplexing, and exchange. The Ph-GW is connected to the full mesh. The Ph-GW is an optical node located at the entrance of the full mesh network and accommodates various user equipment. The Ph-EX is an optical node that provides a vast number of optical paths. A full mesh is a connection configuration in which all elements constituting the communication network are individually and directly connected. The Ph-EX is an optical node that provides a vast number of optical paths. These vast number of optical paths transparently traverse the optical backbone network.

[0082] This configuration allows APN to directly connect any user device installation locations using optical signals without requiring any electrical processing. This enables high-capacity, low-latency communication through dedicated wavelength allocation for user services. APN allows for the flexible combination of necessary service function processing at the required locations, enabling the provision of diverse services. Furthermore, APN provides a communication environment that eliminates the need to be aware of service type, protocol, and optical wavelength.

[0083] To achieve end-to-end optical direct connectivity and service function processing at the required locations, the Ph-GW has the following five basic functions:

[0084] The first basic function is to determine which wavelengths the user equipment will use and to remotely set the wavelength information on the user equipment. In order to establish an end-to-end optical path, the Ph-GW is required to assign wavelengths to each optical path so that there is no overlap in the wavelengths of optical signals between optical paths that share the transmission medium (optical fiber, etc.) within the APN. Furthermore, the Ph-GW is required to remotely set the wavelength information of the optical signals from the user equipment, which is the endpoint of the optical path.

[0085] The second basic function is to stop unnecessary signals caused by incorrect wavelength settings on user equipment, etc., by allowing optical signals to communicate between the access network port and the full-mesh network port in conjunction with the opening of the optical path. Here, the access network is the network between the Ph-GW and the user equipment, and the full-mesh network is the network consisting of Ph-GWs or Ph-GWs and Ph-EXs. Depending on the destination, the Ph-GW forwards (distributes) optical signals input from the access network to the access network, optical signals input from the access network to the full-mesh network, optical signals input from the full-mesh network to the access network, and optical signals input from the full-mesh network to the full-mesh network, all while maintaining their optical nature.

[0086] The third basic function is to concentrate and distribute optical paths that share the transmission medium within a full mesh network.

[0087] The fourth basic function is a loopback function for directly connecting user devices housed in the same Ph-GW. Instead of loopback occurring at higher-level optical nodes, loopback is enabled at the Ph-GW located at the entry point of the full-mesh network, thereby achieving direct optical connection via the shortest path.

[0088] The fifth basic function is the extraction and insertion function. From the perspective of transmitting optical signals, the extraction and insertion function enables electrical processing at the Ph-GW location in order to perform optical signal regeneration and relay, and to perform service function processing.

[0089] (Overview of APN) Figure 9 shows an example configuration of a communication system 1a that communicates using a communication network such as an All-Photonics Network (APN). The communication system 1a transmits an optical signal from a device at one end of the section to be judged, and the user device at the other end performs optical-to-electrical-to-optical conversion (OEO conversion) to return the optical signal, thereby determining the normality of the optical signal path in the section to be judged.

[0090] Communication system 1c comprises Ph-GW100-1, Ph-GW100-2, APN controller 200, user device 300-1, and user device 300-2. For simplicity of explanation, Figure 9 shows two Ph-GWs and two user devices. In an actual communication system, multiple Ph-GWs and user devices are likely to be deployed, and it is conceivable that Ph-EXs may be used between Ph-GWs, or that user devices may be connected via only a single Ph-GW.

[0091] The Ph-GW100 transmits and receives optical signals for determining the normality of user equipment and other Ph-GW100 sections, and for monitoring and controlling user equipment; therefore, it is equipped with a device for transmitting and receiving optical signals (transceiver). Note that if the location of the Ph-GW100 is not at the end of the section, the optical signal may be transmitted.

[0092] Furthermore, the Ph-GW100 is a device (distribution device) that distributes optical signals to their destinations. The Ph-GW100-1 comprises an optical distribution unit 101-1, a wavelength division multiplexing / decoupling unit 102-1, and an access system management control unit 103-1. The Ph-GW100-2 comprises an optical distribution unit 101-2, a wavelength division multiplexing / decoupling unit 102-2, and an access system management control unit 103-2. The optical distribution unit 101 is equipped with multiple input / output ports (not shown). Note that the wavelength division multiplexing / decoupling unit 102 does not necessarily have to be provided in the path of the target optical signal.

[0093] Optical distribution units 101-1 and 101-2 forward (distribute) optical signals input from the access network and full mesh network according to their destination, while remaining as optical signals. In this way, optical distribution units 101-1 and 101-2 realize the function of loopback for direct optical connection (the fourth basic function described above).

[0094] Optical distribution units 101-1 and 101-2 implement a loopback function (the fourth basic function described above) for directly optically connecting user devices 300 housed in the same Ph-GW100. Furthermore, optical distribution units 101-1 and 101-2 implement an optical add-drop function (the fifth basic function described above) to an electrical processing unit (not shown).

[0095] The wavelength division multiplexing (WDM) separation unit 102-1 wavelength-multiplexes the optical signals output from the optical distribution unit 101-1 that have the same destination. The wavelength division multiplexing unit 102-1 outputs the wavelength-multiplexed optical signals to the full mesh network. The wavelength division multiplexing unit 102-1 separates the wavelength-multiplexed signals input from the full mesh network on a wavelength basis.

[0096] The wavelength division multiplexing (WDM) separation unit 102-2 wavelength-multiplexes the optical signals output from the optical distribution unit 101-2 that have the same destination. The wavelength division multiplexing unit 102-2 outputs the wavelength-multiplexed optical signals to the full-mesh network. The wavelength division multiplexing unit 102-2 separates the wavelength-multiplexed signals input from the full-mesh network on a wavelength basis (the third basic function described above).

[0097] The access system management control unit 103-1 exchanges control information with the user device 300-1 during the initial connection of the user device 300-1. The access system management control unit 103-1 transmits a wavelength setting instruction to the user device 300-1.

[0098] The access system management control unit 103-2 exchanges control information with the user device 300-2 during the initial connection of the user device 300-2. The access system management control unit 103-2 transmits a wavelength setting instruction to the user device 300-2 (the first basic function described above).

[0099] The optical signals transmitted and received by the access system management control unit 103 (hereinafter referred to as "access system optical signals") may be multiplexed and separated at any point along the path to the user device 300. For example, the access system optical signals may be multiplexed and separated in the wavelength division multiplexing unit 102, or between the wavelength division multiplexing unit 102 and the optical distribution unit 101, or in the optical distribution unit 101, or between the optical distribution unit 101 and the user device 300.

[0100] The access system management control unit 103 may, instead of multiplexing the access system optical signal with the main signal optical signal using spatial division multiplexing, polarization division multiplexing, wavelength division multiplexing, etc., multiplex the control signal with the main signal optical signal in the form of time division multiplexing, code division multiplexing, frequency division multiplexing such as AMCC, or multiplex the control signal on the main signal optical signal by modulating it in the form of intensity modulation, phase modulation, frequency modulation, or polarization modulation. In this case, instead of using a splitter or multiplexer / demultiplexer, multiplexing may be performed using a modulator or an amplifier or attenuator capable of modulating the amplification factor or attenuation factor. The following explanation will mainly describe the case where the control signal is multiplexed on the main signal optical signal, but it is clear that this can also be used when multiplexing an access system optical signal separate from the main signal optical signal. Furthermore, if the access optical signal is multiplexed on the loopback side, and the optical transmitters and receivers for the access optical signal and the main signal are separate, the optical transmitter and receiver for the main signal will be excluded from the normality check. Therefore, it is desirable to perform a further loopback between the optical transmitter and receiver, or to confirm normality by means other than loopback, in order to check the normality of the section that has been excluded from the normality check. Also, if the loopback signal is looped back from the optical transmitter of the access optical signal only after the normality of the optical transmitter and receiver of the main signal has been confirmed by these methods, the normality of the optical transmitter and receiver of the main signal can be notified with a single loopback. Of course, the optical transmitter and receiver of the main signal and the optical transmitter and receiver of the access optical signal can be checked separately and notified separately.

[0101] The access system optical signal may be combined into the path to the user device 300 at any point. For example, the access system optical signal may be combined in the wavelength division multiplexing / decompression unit 102, or between the wavelength division multiplexing / decompression unit 102 and the optical distribution unit 101, or in the optical distribution unit 101, or between the optical distribution unit 101 and the user device 300.

[0102] To easily provide dedicated networks for different wavelengths based on function, APNs supporting diverse social infrastructure networks are required to be able to configure optical paths for various user devices. Therefore, a mechanism is needed in which the optical path is immediately activated simply by connecting user devices 300-1 and 300-2 to optical fiber.

[0103] Firstly, user devices 300-1 and 300-2 declare their own device information and opposing device information to Ph-GW100-1 and Ph-GW100-2. User device 300-1 or user device 300-2 may also declare their own device information and opposing device information to Ph-GW100-1 or Ph-GW100-2.

[0104] Although the report is to be submitted to the most recent Ph-GW100, it is also permissible to submit to a Ph-GW100 other than the most recent one. For example, user device 300-1 or user device 300-2 may submit its own device information and the opposing device information to Ph-GW100-2 or Ph-GW100-1. The latter is preferable, for example, when restoring a connection and the information of the Ph-GW to which the opposing device is connected is known. The following explanation will mainly focus on the case where the report is submitted to the most recent device.

[0105] Secondly, the APN controller 200 performs wavelength resource management and optical path design within the APN. In response to a declaration from user device 300-1 or user device 300-2, Ph-GW100-1 or Ph-GW100-2, in cooperation with the APN controller 200, determines the allocated wavelengths for user device 300-1 and user device 300-2. Ph-GW100-1 or Ph-GW100-2 then notifies user device 300-1 or user device 300-2 of the wavelengths.

[0106] Thirdly, the internal routes of Ph-GW100-1, the internal routes of Ph-GW100-2, and the internal routes of Ph-EX are set. In Figure 9, the internal routes of Ph-GW100-1, the internal routes of Ph-GW100-2, and the routes connecting Ph-GW100-1 and Ph-GW100-2 are set. If Ph-GW100-1 and Ph-GW100-2 are connected via Ph-EX (not shown), then the internal routes of Ph-GW100-1, the routes of Ph-GW100-1 and Ph-EX (not shown), the internal routes of Ph-EX (not shown), the routes of Ph-EX (not shown) and Ph-GW100-2, and the internal routes of Ph-GW100-2 are set.

[0107] In APN, optical signals corresponding to signals from various communication protocols are transmitted from user device 300-1 and user device 300-2. Therefore, a management and control method that is independent of the communication protocol is required. For such access system control and management, AMCC is used, for example.

[0108] Furthermore, the communication system 1c includes the following configuration in order to identify the transmission characteristics, which are the characteristics of the transmission path between the optical transmitter and the optical receiver. The optical transmitter includes a tunable transmitting unit capable of transmitting an optical signal of at least the wavelength channel whose transmission characteristics are to be confirmed. The optical receiver includes a wavelength-independent optical receiving unit. Here, the optical transmitter may be the user device 300 in the communication system 1c or the Ph-GW100. The optical receiver is the Ph-GW100 when the optical transmitter is the user device 300, and the user device 300 when the optical transmitter is the Ph-GW100.

[0109] Figure 10 shows an example configuration (part 1) of the communication system 1c in the fourth embodiment. In Figure 10, only the devices related to one section that is the target of the signal path normality determination and the continuity width confirmation are shown among the devices included in the communication system 1c. In the fourth embodiment, the access system management control unit 103 performs a signal path normality determination on the user device 300 connected to its own device (Ph-GW100). For example, the access system management control unit 103-2 in Figure 9 performs a signal path normality determination on the user device 300-2. In relation to Figure 9 and Figure 10, the transmission path 35 shown in Figure 10 represents only the transmission path when the access system management control unit 103 is located closer to the user device 300 than the optical distribution unit 101, and includes both the transmission path and the optical distribution unit 101 when the optical distribution unit 101 is located closer to the user device 300 than the access system management control unit 103.

[0110] That is, as shown in Figure 10 and the following Figures 13, 14, 15, 16, and 17, the configuration in which the access system management control unit 103 is equipped with a combining / separating unit that multiplexes / separates or superimposes control signals on the main signal can also be viewed as follows. For example, a transmitter is positioned to output an optical signal to a device (e.g., user device 300) that folds back an optical signal via an optical combiner or optical combiner / demultiplexer installed outside the input port or output port to the optical distribution unit 101. For example, a transmitter is positioned in a monitoring unit that monitors the optical intensity of the optical signal on at least one of the input and output sides of the Ph-GW100, or exchanges control signals with the user device 300. Instead of outputting combined or combined light via an optical combiner or optical combiner / demultiplexer, light generated by the optical nonlinear effects of the light to be folded back may be output.

[0111] For example, a receiver is positioned to receive at least a portion of the optical signal or its components that have been folded back from a device that folds back an optical signal, via an optical combiner or optical demultiplexer installed outside the input or output port to the optical distribution unit 101. For example, a receiver is positioned in a monitoring unit that monitors the light intensity of the optical signal on at least one of the input and output sides of the Ph-GW100, or exchanges control signals with the user device 300. Instead of receiving light that has been branched or demultiplexed via an optical combiner or optical demultiplexer, light generated by the optical nonlinear effects of the folded light may be received.

[0112] As shown in Figure 12, a configuration in which the access system management control unit 103 does not have a splitting unit for multiplexing or superimposing control signals onto the main signal may be considered as follows. For example, if a transmitter that transmits optical signals folded back by the opposing device is located in the Ph-GW100, the transmitter is located in the access system management control unit 103 which is connected via the optical distribution unit 101. For example, if a receiver that receives at least a portion of the optical signals folded back by the opposing device is located in the Ph-GW100, the receiver is located in a place other than the access system management control unit 103 which is connected via the optical distribution unit 101.

[0113] Furthermore, in the fourth embodiment, a process is also performed to identify the transmission characteristics of the transmission path 35 between the Ph-GW100, which includes the access system management control unit 103, and the user device 300 (wavelength channel width continuity confirmation process). In the fourth embodiment, the communication system 1c will be described in the case where the user device 300 is configured as an optical transmitter 10 and the Ph-GW100, which includes the access system management control unit 103, is configured as an optical receiver 20. That is, in the communication system 1c of the fourth embodiment, the user device 300 transmits optical signals of each wavelength while sweeping the wavelength of the light source, and the Ph-GW100, which includes the access system management control unit 103, converts the optical signals of each wavelength into electrical signals, measures the received intensity of the electrical signals, identifies which wavelength is being transmitted, and determines the continuity width.

[0114] The access system management control unit 103 transmits a control signal to a user device 300 (target user device) connected to the section subject to signal path normality determination, instructing it to loopback. In the loopback in the fourth embodiment, the normality of the path between UNI_PHY and MAC is not determined. The control signal used is a control signal that is used in common by multiple user devices 300 (which may be all user devices 300 of the communication system 1). A specific example of such a control signal is AMCC. To realize this processing, the access system management control unit 103 includes a determination control unit 401, an optical interface unit (optical IF unit) 405, an optical interface unit (optical IF unit) 406, a coupling / splitting unit 407, and a coupling / splitting unit 408.

[0115] The judgment control unit 401 performs signal path normality determination processing. The judgment control unit 401 is composed of one or more processors such as a CPU (Central Processing Unit) and one or more memories. The judgment control unit 401 functions by one or more processors executing a program. All or part of the functions of the judgment control unit 401 may be implemented using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The above program may be recorded on a computer-readable recording medium. Computer-readable recording media include, for example, portable media such as flexible disks, magneto-optical disks, ROMs (Read Only Memory), CD-ROMs (Compact Disc Read Only Memory), semiconductor memory devices (e.g., SSDs: Solid State Drives), and memory devices such as hard disks and semiconductor memory devices built into computer systems. The above program may be transmitted via a telecommunications line.

[0116] The determination control unit 401 outputs a control signal to the optical interface unit 405 indicating the execution of loopback. The control signal used is a signal that can be used in common by multiple user devices 300. The control signal output by the determination control unit 401 is an electrical signal. When the determination control unit 401 receives the control signal looped back from the user device 300, it determines the normality of the path to be judged based on the received signal. For example, the determination control unit 401 receives the control signal looped back from the user device 300 via the coupling / canceling unit 408 and the optical interface unit 406. In this way, the determination control unit 401 outputs the control signal, which is an electrical signal, to the optical interface unit 405 and obtains the control signal, which has been converted back into an electrical signal, from the optical interface unit 406.

[0117] The optical interface unit 405 converts the control signal, which is an electrical signal output from the determination control unit 401, into an optical signal. The optical interface unit 405 outputs the converted optical signal to the matching / separating unit 407.

[0118] The coupling / canceling unit 407 receives the optical signal output from the optical interface unit 405 and the main signal addressed to the user device 300 (hereinafter referred to as the "downlink main signal") as input. The coupling / canceling unit 407 superimposes the optical signal onto the input downlink main signal. For example, the coupling / canceling unit 407 may frequency superimpose the optical signal onto the main signal. Although the configuration shown in Figure 10 superimposes a control signal separate from the downlink main signal, frequency superimposition is also possible in the configuration shown in Figure 10 when modulation is performed by nonlinear optical effects, etc. Furthermore, the configuration when frequency superimposition is performed by a modulator, etc., will be specifically explained in Figure 13.

[0119] The coupling / splitting unit 408 separates or splits the signal received from the user device 300. For example, if the control signal and the upstream main signal can be separated by wavelength separation or the like, the coupling / splitting unit 408 separates the signal received from the user device 300 into the control signal and the upstream main signal. The upstream main signal is the main signal transmitted from the user device 300 in the upstream direction (for example, to the opposing user device). In this case, the coupling / splitting unit 408 outputs the separated control signal to the optical interface unit 406. The coupling / splitting unit 408 outputs the separated upstream main signal to other devices.

[0120] Furthermore, for example, when a control signal such as AMCC is frequency superimposed, the coupling / canceling unit 408 splits the signal received from the user device 300 (the upstream main signal including the control signal). In this case, the coupling / canceling unit 408 outputs the split signal (the upstream main signal including the control signal) to the interface unit 406 and other devices.

[0121] The optical interface unit 406 acquires the optical signal output from the coupling / separating unit 408. The optical signal acquired by the optical interface unit 406 is the upstream main signal, which includes the control signal separated by the coupling / separating unit 408, or the branched control signal. The optical interface unit 406 converts the acquired optical signal into an electrical signal. The optical interface unit 406 outputs the electrical signal obtained by the conversion to the determination control unit 401.

[0122] Furthermore, the optical interface unit 406 includes the receiving unit 21 and wavelength sweep identification unit 22 in the first embodiment, and performs the same processing as the optical receiver 20 in the first embodiment.

[0123] The user device 300 includes an optical transceiver 301 and a control unit 330. The optical transceiver 301 includes an optical interface unit 321 (optical IF unit), a coupling / canceling unit 322, a processing unit 323, a UNI_PHY(Tx) 324, a UNI_PHY(Rx) 325, and an optical interface unit 326 (optical IF unit).

[0124] The optical interface unit 321 converts the optical signal received from the Ph-GW100 into an electrical signal. The optical interface unit 321 outputs the electrical signal obtained by the conversion to the combination / separation unit 322.

[0125] The splitting unit 322 separates the signal received from the Ph-GW100 into a control signal and a downlink main signal. The splitting unit 322 outputs the separated control signal to the control unit 330. The splitting unit 322 outputs the separated downlink main signal to the processing unit 323. The splitting unit 322 superimposes the control signal output from the control unit 330 onto the uplink main signal output from the processing unit 323. For example, the splitting unit 322 may frequency superimpose the control signal onto the uplink main signal.

[0126] If it is a MAC, the processing unit 323 performs media access control on the downstream main signal output from the coupling / separating unit 322. For example, the processing unit 323 defines and assigns an address (MAC address) for identifying the device. For example, the processing unit 323 may control the signal transmission timing. The processing unit 323 outputs the main signal to UNI_PHY(Tx)324. The processing unit 323 may perform media access control on the electrical signal output from UNI_PHY(Rx)325. The processing unit 323 outputs the main signal to the coupling / separating unit 322.

[0127] UNI_PHY(Tx)324 is the receiving function unit in the physical layer of the user network interface. UNI_PHY(Tx)324 performs predetermined receiving processing on electrical signals output from the processing unit 323.

[0128] UNI_PHY(Rx)325 is the transmission function unit in the physical layer of the user network interface. UNI_PHY(Rx)325 outputs an electrical signal corresponding to the main signal to the processing unit 323 by executing a predetermined transmission process.

[0129] The optical interface unit 326 converts the electrical signals (e.g., the upstream main signal and the control signal) output from the coupling / separating unit 322 into optical signals. The optical interface unit 326 may output the control signal and the upstream main signal from different light sources or with different wavelengths and polarizations. The optical interface unit 326 transmits the optical signals obtained by the conversion to the Ph-GW100. Furthermore, the optical interface unit 326 is equipped with the light source 12 in the first embodiment and transmits optical signals of each wavelength included in the sweep width instructed by the wavelength sweep instruction unit 11 provided in the control unit 330 in a predetermined order.

[0130] The control unit 330 is configured using one or more processors such as a CPU and one or more memories. The control unit 330 functions as at least a control signal receiving unit 331, a control signal transmitting unit 332, a loopback unit 333, and a wavelength sweep instruction unit 11, when one or more processors execute a program. All or part of the functions of the control unit 330 may be implemented using hardware such as an ASIC, PLD, or FPGA. The program may be recorded on a computer-readable recording medium. Computer-readable recording media include, for example, portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and semiconductor storage devices (e.g., SSDs), as well as storage devices such as hard disks and semiconductor storage devices built into computer systems. The program may be transmitted via a telecommunications line.

[0131] The control signal receiving unit 331 receives the control signals separated by the coupling / splitting unit 322 from the coupling / splitting unit 322. The control signal receiving unit 331 operates according to the information indicated by the received control signals. If the control signal indicates an instruction to perform a loopback, the control signal receiving unit 331 instructs the loopback unit 333 to perform a loopback according to the instruction.

[0132] The control signal transmission unit 332 outputs the control signal to be transmitted to the matching / separating unit 322. When the loopback unit 333 receives an instruction from the control signal receiving unit 331 to perform loopback, it performs loopback processing according to the instruction. The target of the loopback processing in the loopback unit 333 is, for example, a control signal. The loopback processing may be performed, for example, as a full-channel loopback, as a partial loopback, or as a logical loopback. The looped-back control signal is converted into an optical signal in the optical interface unit 326 and transmitted to the access system management control unit 103.

[0133] The wavelength sweep instruction unit 11 performs the same processing as the wavelength sweep instruction unit 11 in the first embodiment. Specifically, the wavelength sweep instruction unit 11 instructs the light source 12 provided in the optical interface unit 326 to sweep the wavelength channels to be checked for continuity. The wavelength sweep instruction unit 11 may instruct the light source 12 at any timing during initial setup, or it may instruct the light source 12 when it receives a control signal transmitted from the access system management control unit 103.

[0134] The processing flow for determining the normality of the signal path in the fourth embodiment will now be described. At a predetermined timing, the determination control unit 401 generates a control signal to instruct the execution of loopback. The determination control unit 401 outputs the generated control signal to the optical interface unit 405. The predetermined timing may be, for example, the timing at which a problem is detected in communication with the user device 300. The optical interface unit 405 converts the control signal output from the determination control unit 401 into an optical signal and outputs it to the signal splitting unit 407. The signal splitting unit 407 receives the downstream main signal transmitted from another device and the optical signal output from the optical interface unit 405 as inputs. The signal splitting unit 407 combines the input downstream main signal and optical signal (for example, superimposing the optical signal on the downstream main signal) and transmits the combined optical signal to the user device 300 via the transmission path.

[0135] When the optical interface unit 321 of the user device 300 receives the combined optical signal from the access system management control unit 103, it converts the received combined optical signal into an electrical signal and outputs it to the combining / separating unit 322. The combining / separating unit 322 separates the downstream main signal and the control signal from the received signal. The combining / separating unit 322 outputs the separated control signal to the control unit 330 and the separated downstream main signal to the processing unit 323.

[0136] When the control signal receiving unit 331 of the control unit 330 receives a control signal from the signal splitting unit 322, it operates according to the content of the control included in the control signal. The control signal includes a signal indicating an instruction to perform loopback. In response to this instruction, the control signal receiving unit 331 instructs the loopback unit 333 to perform loopback of the control signal. The loopback unit 333 performs loopback processing on the received control signal and outputs the control signal to the signal splitting unit 322. The signal splitting unit 322 combines the control signal output from the control unit 330 and the upstream main signal output from the processing unit 323. The control signal and upstream main signal combined by the signal splitting unit 322 are looped back to the access system management control unit 103.

[0137] The looped-back upstream main signal and control signal are separated in the coupling / separating unit 408. For example, the coupling / separating unit 408 separates the upstream main signal and the control signal. The control signal separated in the coupling / separating unit 408 is converted into an electrical signal in the optical interface unit 406 and input to the determination control unit 401, which was the source of the control signal. The determination control unit 401 performs a predetermined evaluation of the input control signal according to the continuity check. For example, an evaluation may be performed to determine whether the loopback was performed correctly. Based on the evaluation result, the determination control unit 401 makes a determination of the signal path normality for the target user device. The determination control unit 401 may output the determination result to another device or record it as a log in a storage device.

[0138] In the fourth embodiment, the communication system 1c may perform the wavelength channel width continuity check process offline during initial setup, similar to the first embodiment. Alternatively, the communication system 1c in the fourth embodiment may perform the wavelength channel width continuity check process at the same time as the signal path normality determination process is performed, or at the time the signal path normality determination process is completed. The wavelength channel width continuity check process is the same as in the first embodiment.

[0139] Figure 11 is a diagram illustrating the configuration when AMCC is used, as in the communication system 1c of the fourth embodiment. The modulation sideband of AMCC has a narrower spectral width compared to the modulation sideband of the main signal, which has a higher modulation speed. For example, even if the main signal does not conduct due to bandwidth limitations during the second stage modulation in the first stage conduction band, it may conduct if the main signal is unmodulated and only the AMCC is modulating. Therefore, even with a signal modulated only by AMCC, which has a narrow modulation sideband, the main signal with a wider modulation sideband is simulated by changing the wavelength, thereby mitigating the effects of bandwidth limitations. Even when the modulation of the main signal has stopped, and even if there is a wavelength shift in the optical transmitter or the effect of bandwidth limitations in the transmission line 35, it is possible to confirm whether the main signal can conduct by checking the AMCC's conduction.

[0140] With the communication system 1c in the fourth embodiment configured as described above, the same effects as in the first embodiment can be obtained even with APN.

[0141] (Modification 1 of the fourth embodiment) In the embodiments described above, an example was shown in which the user device 300 has a configuration corresponding to the optical transmitter 10 in the first embodiment, and the access system management control unit 103 has a configuration corresponding to the optical receiver 20 in the first embodiment. In the communication system 1c of the fourth embodiment, the user device 300 may be configured to have a configuration corresponding to the optical transmitter 10a in the second embodiment or the optical transceiver 15 in the third embodiment, and the access system management control unit 103 may be configured to have a configuration corresponding to the optical receiver 20a in the second embodiment or the loopback device 18 in the third embodiment.

[0142] For example, if the user device 300 has the configuration of the optical transmitter 10a in the second embodiment, the wavelength sweep instruction unit 11 is provided in the control unit 330, the light source 12 is provided in the optical interface unit 326, and the response receiving unit 13 is provided in the optical interface unit 321. If the access system management control unit 103 has the configuration of the optical receiver 20a in the second embodiment, the receiving unit 21 is provided in the optical interface unit 406, and the response unit 23 is provided in the optical interface unit 405. The specific processing is the same as in the second embodiment.

[0143] For example, if the user device 300 has the configuration of the optical transceiver 15 in the third embodiment, the wavelength sweep instruction unit 11 is provided in the control unit 330, the light source 12 is provided in the optical interface unit 326, and the response receiving unit 13 and the wavelength sweep identification unit 14 are provided in the optical interface unit 321. If the access system management control unit 103 has the configuration of the reversal device 18 in the third embodiment, the reflection transmission unit 24 is provided in front of the optical interface units 405 and 406 (closer to the transmission path 35 than the optical interface units 405 and 406), and transmits an optical signal of a specific wavelength and reverses the optical signal of the swept wavelength. The specific processing is the same as in the third embodiment.

[0144] (Modification 2 of the fourth embodiment) In the embodiments described above, the user device 300 is configured to determine the conduction width by transmitting optical signals of each wavelength while sweeping the wavelength of the light source. In the communication system 1c of the fourth embodiment, the access system management control unit 103 may also be configured to transmit optical signals of each wavelength while sweeping the wavelength of the light source, thereby determining the conduction width bidirectionally. The following description will use an example using the configuration of the first embodiment, but the configurations of the second and third embodiments may also be used.

[0145] In this configuration, the access system management control unit 103 further comprises a wavelength sweep instruction unit 11, and the optical interface unit 405 further comprises the light source 12 in the first embodiment. The light source 12 of the optical interface unit 405 sequentially transmits optical signals of each wavelength included in the sweep width instructed by the wavelength sweep instruction unit 11.

[0146] The optical interface unit 321 of the optical transceiver 301 of the user device 300 further includes a receiving unit 21 and a wavelength sweep identification unit 22 in the first embodiment, and performs the same processing as the optical receiver 20 in the first embodiment.

[0147] (Modification 4 of the fourth embodiment) The access system management control unit 103 shown in Figure 10 may be configured as shown in Figure 12. Figure 12 is a diagram showing an example of the configuration of the communication system 1c in the fourth embodiment (part 2). In Figure 12, only the devices related to one section that is the target of the signal path normality determination and the conduction width confirmation are shown among the devices included in the communication system 1c. In relation to Figure 9 and Figure 12, the transmission path 35 shown in Figure 12 represents only the transmission path when the access system management control unit 103 is located closer to the user device 300 than the optical distribution unit 101, and includes both the transmission path and the optical distribution unit 101 when the optical distribution unit 101 is located closer to the user device 300 than the access system management control unit 103.

[0148] The access system management control unit 103 shown in Figure 12 comprises a determination control unit 401, an optical interface unit (optical IF unit) 405, and an optical interface unit (optical IF unit) 406. The access system management control unit 103 shown in Figure 12 differs in configuration from the access system management control unit 103 shown in Figure 10 in that it does not include a coupling / uncoupling unit 407 and a coupling / uncoupling unit 408. The differences from the access system management control unit 103 shown in Figure 10 will be explained below.

[0149] The optical interface unit 405 converts the control signal (labeled as the downlink control signal in Figure 12), which is an electrical signal output from the determination control unit 401, into an optical signal. The optical interface unit 405 transmits the converted optical signal to the user device 300 via the transmission line 35.

[0150] The optical interface unit 406 receives the optical signal transmitted from the user device 300 via the transmission path 35. The optical signal received by the optical interface unit 406 is an uplink control signal. The optical interface unit 406 converts the received optical signal into an electrical signal. The optical interface unit 406 outputs the electrical signal obtained by the conversion to the decision control unit 401.

[0151] Furthermore, the optical interface unit 406 includes the receiving unit 21 and wavelength sweep identification unit 22 in the first embodiment, and performs the same processing as the optical receiver 20 in the first embodiment.

[0152] Thus, the access system management control unit 103 shown in Figure 12 does not transmit or receive main signals, but only transmits and receives control signals. The user device 300 shown in Figure 12 performs the same processing as the user device 300 shown in Figure 10, except for the processing that uses the upstream main signal and downstream main signal, as described in Figure 10.

[0153] Figure 10 shows a configuration in which the control signal is multiplexed with the main signal, but the configuration shown in Figure 12 corresponds to a configuration in which the optical distribution unit 101 switches to inputting and outputting the up and down control signals instead of the up and down main signals.

[0154] (Modification 5 of the fourth embodiment) The access system management control unit 103 shown in Figure 10 may be configured as shown in Figure 13. Figure 13 is a diagram showing an example of the configuration of the communication system 1c in the fourth embodiment (part 3). In Figure 13, only the devices related to one section that is the target of the signal path normality determination and the conduction width confirmation are shown among the devices included in the communication system 1c. In relation to Figure 9 and Figure 13, the transmission path 35 shown in Figure 13 represents only the transmission path when the access system management control unit 103 is located closer to the user device 300 than the optical distribution unit 101, and includes both the transmission path and the optical distribution unit 101 when the optical distribution unit 101 is located closer to the user device 300 than the access system management control unit 103.

[0155] The access system management control unit 103 shown in Figure 13 comprises a determination control unit 401, a modulation unit 409, and a monitor unit 410. The access system management control unit 103 shown in Figure 13 differs in configuration from the access system management control unit 103 shown in Figure 10 in that it does not include the optical interface unit 405, optical interface unit 406, coupling / uncoupling unit 407, and coupling / uncoupling unit 408, but newly includes the modulation unit 409 and the monitor unit 410. The differences from the access system management control unit 103 shown in Figure 10 will be explained below. The configuration shown in Figure 13 assumes in-channel monitoring in the access system management control unit 103.

[0156] The modulation unit 409 receives a control signal output from the determination control unit 401 and a downlink main signal input from an external device as input. The modulation unit 409 modulates the input downlink main signal with the control signal to generate an optically modulated signal. The modulation unit 409 transmits the optically modulated signal to the user device 300 via the transmission line 35.

[0157] The monitor unit 410 monitors the signals (upstream main signal and control signal) received from the user device 300 and outputs them to the decision control unit 401 and other devices. More specifically, the monitor unit 410 has the same functions as the matching / separating unit 408 and the optical interface unit 406, and receives the signals (upstream main signal and control signal) transmitted from the user device 300. The monitor unit 410 branches the received signal, converts the upstream main signal including the branched control signal into an electrical signal, and outputs it to the decision control unit 401. The access system management control unit 103 may further include the receiving unit 21 and wavelength sweep identification unit 22 in the first embodiment, and may perform the same processing as the optical receiver 20 in the first embodiment based on the optical signal transmitted from the user device 300. The receiving unit 21 and wavelength sweep identification unit 22 may be located inside the monitor unit 410 or outside the monitor unit 410, as long as they can be acquired after the optical signal transmitted from the user device 300 has been converted into an electrical signal. Furthermore, the monitor unit 410 outputs the upstream main signal, including the branched control signals, as an optical signal to an external device.

[0158] The operations performed by the user device 300 are the same as those shown in Figure 10.

[0159] (Modification 6 of the fourth embodiment) The access system management control unit 103 shown in Figure 10 may be configured as shown in Figure 14. Figure 14 is a diagram showing an example of the configuration of the communication system 1c in the fourth embodiment (part 4). In Figure 14, only the devices related to one section that is the target of the signal path normality determination and the conduction width confirmation are shown among the devices included in the communication system 1c. In relation to Figure 9 and Figure 14, the transmission path 35 shown in Figure 14 represents only the transmission path when the access system management control unit 103 is located closer to the user device 300 than the optical distribution unit 101, and includes both the transmission path and the optical distribution unit 101 when the optical distribution unit 101 is located closer to the user device 300 than the access system management control unit 103.

[0160] The access system management control unit 103 shown in Figure 14 comprises a determination control unit 401, an optical interface unit 406, a coupling / uncoupling unit 408, and a modulation unit 409. The access system management control unit 103 shown in Figure 14 differs in configuration from the access system management control unit 103 shown in Figure 10 in that it does not include the optical interface unit 405, optical interface unit 406, and coupling / uncoupling unit 407, but newly includes a modulation unit 409. The differences from the access system management control unit 103 shown in Figure 10 will be explained below.

[0161] The modulation unit 409 receives a control signal output from the determination control unit 401 and a downlink main signal input from an external device as input. The modulation unit 409 modulates the input downlink main signal with the control signal to generate an optically modulated signal. The modulation unit 409 transmits the optically modulated signal to the user device 300 via the transmission line 35.

[0162] The coupling / separation unit 408 and the interface unit 406 perform the same processing as the coupling / separation unit 408 and interface unit 406 shown in Figure 10.

[0163] (Modification 7 of the fourth embodiment) The embodiments and modifications 1 to 6 described above show a configuration in which the AMCC signal is looped back to determine the normality of the signal path. The access system management control unit 103 may be configured to loop back the main signal at the user device 300 to determine the normality of the signal path. Figure 15 shows an example of the configuration of the communication system 1c in modification 7 of the fourth embodiment. Figure 15 shows only the devices included in the communication system 1c that are related to one section that is the target of the signal path normality determination and the target of the conduction width confirmation. In the fourth embodiment, the access system management control unit 103 performs a signal path normality determination on the user device 300 connected to its own device (Ph-GW100). For example, the access system management control unit 103-2 in Figure 9 performs a signal path normality determination on the user device 300-2. In relation to Figure 9 and Figure 15, the transmission path 35 shown in Figure 15 represents only the transmission path when the access system management control unit 103 is located closer to the user device 300 than the optical distribution unit 101, and includes both the transmission path and the optical distribution unit 101 when the optical distribution unit 101 is located closer to the user device 300 than the access system management control unit 103.

[0164] When the main signal is looped back by the user device 300, unlike the explanation in Figure 10, the main signal is looped back to the access system management control unit 103 via the processing unit 323, UNI_PHY(Tx) 324, and UNI_PHY(Rx) 325. More specifically, the splitting unit 322 separates the control signal from the signal received from the Ph-GW 100 and outputs the separated control signal to the control unit 330. The control signal includes, for example, information indicating an instruction to loop back the main signal. The splitting unit 322 outputs the signal with the separated control signal (main signal) to the processing unit 323. Based on the control signal, the control unit 330 instructs the optical transceiver 301 to loop back the main signal. Furthermore, the wavelength sweep instruction unit 11 of the control unit 330 instructs the optical transceiver 301 to perform a wavelength channel width continuity check process when looping back.

[0165] The optical transceiver 301, in accordance with instructions from the control unit 330, loops back the main signal output from the coupling / separating unit 322 to the access system management control unit 103 via the processing unit 323, UNI_PHY(Tx) 324, UNI_PHY(Rx) 325, coupling / separating unit 322, and optical interface unit 326.

[0166] Furthermore, the optical interface unit 326 of the optical transceiver 301 transmits optical signals of each wavelength while sweeping the wavelength of the light source according to instructions from the control unit 330.

[0167] The main signal looped back in the user device 300 is input to the access system management control unit 103. The configuration of the access system management control unit 103 is basically the same as that shown in Figure 10. The difference between the access system management control unit 103 shown in Figure 15 and the access system management control unit 103 shown in Figure 10 is that the main signal separated in the coupling / uncoupling unit 408 is input to the optical interface unit 406. Subsequently, the optical interface unit 406 converts the main signal separated in the coupling / uncoupling unit 408 into an electrical signal and outputs it to the determination control unit 401. The determination control unit 401 performs a predetermined evaluation of the input main signal according to the continuity check. For example, an evaluation may be performed on whether or not the loopback was performed correctly. Based on the evaluation result, the determination control unit 401 makes a judgment on the normality of the signal path for the target user device. The determination control unit 401 may output the judgment result to another device or record it as a log in a storage device. Furthermore, if the main signal is looped back by the user device 300, the access system management control unit 103 shown in Figure 15 may have the same configuration as the access system management control unit 103 shown in Figure 13.

[0168] Furthermore, the optical interface unit 406 of the access system management control unit 103 converts the optical signals of each wavelength transmitted from the user device 300 into electrical signals, measures the received intensity of the electrical signals, identifies which wavelengths are being transmitted, and determines the conductivity width.

[0169] (Fifth embodiment) In the fifth embodiment, a configuration in which the configurations shown in the first to third embodiments are applied to the APN will be described. In the fifth embodiment, the Ph-GW transmits optical signals of each wavelength while sweeping the wavelength of the light source, and the user device converts the optical signals of each wavelength into electrical signals, measures the received intensity of the electrical signals, identifies which wavelengths are being transmitted, and determines the conduction width. In the fifth embodiment, the conduction width in the downstream direction is determined.

[0170] Figure 16 shows an example of the configuration of the communication system 1c in the fifth embodiment. In Figure 16, only the devices related to one section that is the target of the signal path normality determination and the continuity width confirmation are shown among the devices included in the communication system 1c. In the fifth embodiment, the access system management control unit 103 performs a signal path normality determination on the user device 300 connected to its own device (Ph-GW100). For example, the access system management control unit 103-2 in Figure 9 performs a signal path normality determination on the user device 300-2. In relation to Figure 9 and Figure 16, the transmission path 35 shown in Figure 16 represents only the transmission path when the access system management control unit 103 is located closer to the user device 300 than the optical distribution unit 101, and includes both the transmission path and the optical distribution unit 101 when the optical distribution unit 101 is located closer to the user device 300 than the access system management control unit 103.

[0171] Furthermore, in the fifth embodiment, the access system management control unit 103 also performs a process to identify the transmission characteristics of the transmission path 35 between the Ph-GW 100, which includes the access system management control unit 103, and the user device 300 (wavelength channel width continuity confirmation process). In the communication system 1c of the fifth embodiment, the case in which the Ph-GW 100, which includes the access system management control unit 103, is configured as an optical transmitter 10 and the user device 300 is configured as an optical receiver 20 will be described. That is, in the communication system 1c of the fifth embodiment, the Ph-GW 100, which includes the access system management control unit 103, transmits optical signals of each wavelength while sweeping the wavelength of the light source, and the user device 300 converts the optical signals of each wavelength into electrical signals, measures the received intensity of the electrical signals, identifies which wavelength is being transmitted, and determines the continuity width. The differences from the fourth embodiment will be described below.

[0172] The access system management control unit 103 includes a determination control unit 401, an optical interface unit (optical IF unit) 405, an optical interface unit (optical IF unit) 406, a matching / separating unit 407, a matching / separating unit 408, and a wavelength sweep instruction unit 11.

[0173] The wavelength sweep instruction unit 11 performs the same processing as the wavelength sweep instruction unit 11 in the first embodiment. Specifically, the wavelength sweep instruction unit 11 instructs the light source 12 provided in the optical interface unit 405 to sweep the wavelength channels to be checked for continuity. The wavelength sweep instruction unit 11 may instruct the light source 12 at any timing during initial setup, or it may instruct the light source 12 at the timing when the access system management control unit 103 transmits a control signal.

[0174] The optical interface unit 405 converts the control signal output from the determination control unit 401 into an optical signal. The optical interface unit 405 outputs the converted optical signal to the matching / separating unit 407. Furthermore, the optical interface unit 405 is equipped with the light source 12 in the first embodiment and sequentially transmits optical signals of each wavelength included in the sweep width instructed by the wavelength sweep instruction unit 11.

[0175] The combining / separating unit 407 receives the optical signal output from the optical interface unit 405 and the downstream main signal as inputs. The combining / separating unit 407 superimposes the optical signal onto the input downstream main signal. For example, the combining / separating unit 407 may frequency superimpose the optical signal onto the main signal.

[0176] The coupling / splitting unit 408 separates or splits the signal received from the user device 300. For example, if the control signal and the upstream main signal can be separated by wavelength separation or the like, the coupling / splitting unit 408 separates the signal received from the user device 300 into the control signal and the upstream main signal. The upstream main signal is the main signal transmitted from the user device 300 in the upstream direction (for example, to the opposing user device). In this case, the coupling / splitting unit 408 outputs the separated control signal to the optical interface unit 406. The coupling / splitting unit 408 outputs the separated upstream main signal to other devices.

[0177] Furthermore, for example, when a control signal such as AMCC is frequency superimposed, the coupling / canceling unit 408 splits the signal received from the user device 300 (the upstream main signal including the control signal). In this case, the coupling / canceling unit 408 outputs the split signal (the upstream main signal including the control signal) to the interface unit 406 and other devices.

[0178] The optical interface unit 406 acquires the optical signal output from the coupling / separating unit 408. The optical signal acquired by the optical interface unit 406 is the upstream main signal, which includes the control signal separated by the coupling / separating unit 408, or the branched control signal. The optical interface unit 406 converts the acquired optical signal into an electrical signal. The optical interface unit 406 outputs the electrical signal obtained by the conversion to the determination control unit 401.

[0179] The user device 300 includes an optical transceiver 301 and a control unit 330. The optical interface unit 321 of the optical transceiver 301 further includes a receiving unit 21 and a wavelength sweep identification unit 22 in the first embodiment, and performs the same processing as the optical receiver 20 in the first embodiment.

[0180] In the fifth embodiment, the communication system 1c may perform the wavelength channel width continuity check process offline during initial setup, similar to the first embodiment. Alternatively, the communication system 1c in the fifth embodiment may perform the wavelength channel width continuity check process at the same time as the signal path normality determination process is performed, or at the time the signal path normality determination process is completed. The wavelength channel width continuity check process is the same as in the first embodiment.

[0181] With the communication system 1c in the fifth embodiment configured as described above, the same effects as in the first embodiment can be obtained even with APN.

[0182] (Modification 1 of the fifth embodiment) In the embodiments described above, an example was shown in which the access system management control unit 103 has a configuration corresponding to the optical transmitter 10 in the first embodiment, and the user device 300 has a configuration corresponding to the optical receiver 20 in the first embodiment. In the communication system 1c of the fifth embodiment, the access system management control unit 103 may be configured to have a configuration corresponding to the optical transmitter 10a in the second embodiment or the optical transceiver 15 in the third embodiment, and the user device 300 may be configured to have a configuration corresponding to the optical receiver 20a in the second embodiment or the loopback device 18 in the third embodiment.

[0183] For example, if the access system management control unit 103 has the configuration of the optical transmitter 10a in the second embodiment, the light source 12 is provided in the optical interface unit 405, and the response receiving unit 13 is provided in the optical interface unit 406. If the user device 300 has the configuration of the optical receiver 20a in the second embodiment, the receiving unit 21 is provided in the optical interface unit 321, and the response unit 23 is provided in the optical interface unit 326. The specific processing is the same as in the second embodiment.

[0184] For example, if the access system management control unit 103 has the configuration of the optical transceiver 15 in the third embodiment, the light source 12 is provided in the optical interface unit 405, and the response receiving unit 13 and wavelength sweep identification unit 14 are provided in the optical interface unit 406. If the user device 300 has the configuration of the reversing device 18 in the third embodiment, the reflection transmission unit 24 is provided in front of the optical interface units 321 and 326 (closer to the transmission path 35 than the optical interface units 321 and 326), and transmits optical signals of a specific wavelength and reverses optical signals of a swept wavelength. The specific processing is the same as in the third embodiment.

[0185] (Modification 2 of the fifth embodiment) In the embodiments described above, the access system management control unit 103 is configured to determine the conduction width by transmitting optical signals of each wavelength while sweeping the wavelength of the light source. In the communication system 1c of the fifth embodiment, the user device 300 may also be configured to transmit optical signals of each wavelength while sweeping the wavelength of the light source, and to determine the conduction width bidirectionally. The following description will use an example using the configuration of the first embodiment, but the configurations of the second and third embodiments may also be used.

[0186] In this configuration, the control unit 330 of the user device 300 further comprises a wavelength sweep instruction unit 11, and the optical interface unit 326 further comprises the light source 12 in the first embodiment. The light source 12 of the optical interface unit 326 sequentially transmits optical signals of each wavelength included in the sweep width instructed by the wavelength sweep instruction unit 11.

[0187] The optical interface unit 406 of the access system management control unit 103 further includes the receiving unit 21 and the wavelength sweep identification unit 22 in the first embodiment, and performs the same processing as the optical receiver 20 in the first embodiment.

[0188] (Modification 4 of the fifth embodiment) The access system management control unit 103 shown in Figure 16 does not necessarily have to include the matching / separating unit 407 and the matching / separating unit 408. In this configuration, the access system management control unit 103 shown in Figure 16 is configured to have a wavelength sweep instruction unit 11 added to the access system management control unit 103 shown in Figure 12. The differences from the access system management control unit 103 shown in Figure 12 will be explained below.

[0189] The optical interface unit 405 converts the control signal, which is an electrical signal output from the determination control unit 401, into an optical signal. The optical interface unit 405 transmits the converted optical signal to the user device 300 via the transmission line 35. Furthermore, the optical interface unit 405 includes the light source 12 in the first embodiment and sequentially transmits optical signals of each wavelength included in the sweep width instructed by the wavelength sweep instruction unit 11.

[0190] (Modification 5 of the fifth embodiment) In the above-described embodiment, a configuration was shown in which the AMCC signal is looped back to determine the normality of the signal path. The access system management control unit 103 may be configured to loop back the main signal at the user device 300 to determine the normality of the signal path, as shown in Modification 7 of the fourth embodiment. The process of looping back the main signal at the user device 300 to determine the normality of the signal path is the same as the process shown in Modification 7 of the fourth embodiment.

[0191] (Modification 6 of the fifth embodiment) The configuration for performing signal loopback in the user device 300 may be the configuration shown in Figure 17. Figure 17 is a diagram showing an example of the configuration of the communication system 1c in modification 6 of the fifth embodiment. In relation to Figure 9 and Figure 17, the transmission path 35 shown in Figure 17 represents only the transmission path when the access system management control unit 103 is located closer to the user device 300 than the optical distribution unit 101, and includes both the transmission path and the optical distribution unit 101 when the optical distribution unit 101 is located closer to the user device 300 than the access system management control unit 103.

[0192] In the communication system 1c of the modified example 6 of the fifth embodiment, the Ph-GW100 (access system management control unit 103 in Figure 17) transmits optical signals of each wavelength while sweeping the wavelength of the light source, the user device 300 folds (reflects) the optical signals transmitted from the access system management control unit 103 as light, and the access system management control unit 103 receives the folded optical signals back to the user device 300 to identify which wavelengths are being transmitted and to determine the conduction width.

[0193] The process by which the access system management control unit 103 performs both wavelength sweeping and conduction width determination of the light source is the same as the process performed by the communication system 1b in the third embodiment shown in Figure 7. In this case, the access system management control unit 103 comprises a wavelength sweep instruction unit 11, a light source 12, a response receiving unit 13, and a wavelength sweep identification unit 14, and the user device 300 comprises a reflection transmission unit 24. A detailed explanation follows below.

[0194] The user device 300 comprises an optical transceiver 301, a control unit 330, and a reflection-transmission unit 350. The user device 300 shown in Figure 17 differs in configuration from the user device 300 shown in Figure 16 in that it newly includes the processing of the control unit 330 and the reflection-transmission unit 350. The differences will be explained below. Note that the user device 300 has the reflection-transmission unit 350 on the side closer to the APN (Ph-GW). The user device 300 may also have the reflection-transmission unit 350 in the optical IF unit (for example, the optical interface unit 321).

[0195] When the reflection-transmission unit 350 receives a loopback instruction from the access system management control unit 103, it outputs a loopback instruction to the control unit 330. The reflection-transmission unit 350 switches its operating mode according to the control of the control unit 330. The operating modes are, for example, reflection mode and transmission mode. Reflection mode is a mode in which the reflection-transmission unit 350 operates by not transmitting the optical signal input to it, but by looping it back as light. Transmission mode is a mode in which the reflection-transmission unit 350 operates by transmitting or partially transmitting the optical signal input to it. If the loopback instruction does not include an instruction to loop back the optical signal, that is, if the access system management control unit 103 (instruction device) does not instruct the reflection-transmission unit 350 to loop back the optical signal, the reflection-transmission unit 350 operates in transmission mode, transmits the optical signal (user signal) transmitted from the Ph-GW100, and outputs it to the optical interface unit 321.

[0196] If the loopback instruction includes an instruction to loop back the optical signal, that is, if the access system management control unit 103 instructs to loop back the optical signal, the reflection transmission unit 350 operates in reflection mode and, as a loopback signal, loops back the optical signal transmitted from the Ph-GW100 or the opposing user device to the Ph-GW100 as optical without photoelectric conversion, depending on the period during which normality is confirmed. In other words, the reflection transmission unit 350 performs loopback for all channels. That is, the reflection transmission unit 350 (loopback point) loops back the loopback signal to the Ph-GW100 (transceiver) without changing any of the bits in the bit sequence of the received loopback signal. In other words, the reflection transmission unit 350 reflects the optical signal transmitted from the Ph-GW100. In Figure 17, the arrows returning from the network side through the reflection transmission unit 350 to the network side represent the loopback of the optical signal.

[0197] The control unit 330 does not include a control signal receiving unit 331, a control signal transmitting unit 332, and a loopback unit 333, but includes a switching control unit 334. The switching control unit 334 acquires a loopback instruction from the reflection transmission unit 350. The switching control unit 334 controls the switching of the operating mode of the reflection transmission unit 350 according to the acquired loopback instruction. For example, if the loopback instruction includes an instruction indicating that the optical signal should be loopbacked, the switching control unit 334 controls the reflection transmission unit 350 to loop back the optical signal. For example, if the loopback instruction does not include an instruction indicating that the optical signal should be loopbacked, the switching control unit 334 controls the reflection transmission unit 350 to transmit the optical signal. Through this process, the reflection transmission unit 350 can achieve both optical signal loopback and optical signal transmission.

[0198] The processing performed by each functional unit of the optical transceiver 301, as shown below, is carried out while the reflective transmission unit 350 is transmitting or partially transmitting the optical signal. The optical interface unit 321 (optical IF unit) converts the optical signal transmitted through the reflection-transmission unit 350 into an electrical signal. In this way, photoelectric conversion may be performed inside the user device 300. The optical signal transmitted through the reflection-transmission unit 350 may be the optical signal of the main signal (user signal) or the optical signal of the loopback signal. The optical interface unit 321 outputs an electrical signal corresponding to the optical signal transmitted through the reflection-transmission unit 350 to the coupling / canceling unit 322. Here, even if OE conversion is performed, the remaining optical signal, excluding the part that is OE converted, is not OEO converted and is folded back. In a normal loopback, during loopback, the signal from the user is not transmitted to the network side. Also, the signal from the network is not transmitted to the user side. Therefore, the following explanation of transmitting the signal from the user device to the network and the signal from the network to the user side is an explanation of the operation when loopback is not performed. Depending on the method of loopback, the signal may be transmitted even during loopback using a half mirror or the like.

[0199] The splitting unit 322 separates the main signal (user signal) and the control signal in the optical signal output from the optical interface unit 321. The splitting unit 322 outputs the main signal in the optical signal output from the optical interface unit 321 to the processing unit 323.

[0200] The splitting unit 322 multiplexes the control signal onto the main signal (user signal) in the electrical signal output from the processing unit 323. For example, if the control signal is an AMCC signal, the splitting unit 322 frequency-superimposes the control signal onto the main signal. The splitting unit 322 outputs the electrical signal containing the main signal and the control signal to the optical interface unit 326.

[0201] The processing unit 323 is, for example, a regenerative repeater and includes reshaping, retiming, and regenerating functions. For example, it is a multiplexing unit and a decoupling unit. For example, it is a conversion unit that converts signals from the user network into a signal format that can be transmitted via the APN. For example, it is a framer that multiplexes and decouples signals from the user network into transmission frames. The processing unit 323 is, for example, a MAC and performs media access control. For example, the MAC may perform media access control when sending and receiving user signals that define and assign addresses (MAC addresses) for identifying devices. For example, the MAC may control the transmission timing of optical signals. The MAC performs media access control on optical signals output from the splitting unit 322. The MAC receives signals from the user, sends signals to the user, receives signals from the network, and sends signals to the network according to the media access control. During loopback, the process of preventing signals from passing from the user device to the network side and from the network side to the user side may be performed using media access control. The MAC may perform media access control to prevent signals from UNI_PHY(Tx)324 from being output from the network side to the user side, and to prevent signals from UNI_PHY(Rx)325 from being output from the user side to the network side.

[0202] Furthermore, the configuration of the coupling / splitting unit and the processing unit is not limited to those described above. For example, the coupling / splitting unit may be located on the network side of the optical IF unit. In this case, the coupling / splitting unit performs AMCC superposition and separation in the optical signal. Also, if control signals are exchanged using OTN frames or GCC, the coupling / splitting unit and the processing unit equivalent may function as an OTN framer.

[0203] UNI_PHY(Tx)324 is the receiving function unit at the physical layer of the user network interface. UNI_PHY(Rx)325 performs predetermined receiving processing on the electrical signal (main signal) output from the processing unit 323. The user-side receiver (Rx) receives signals from the user side, and the network-side receiver (Rx) receives signals from the network side.

[0204] UNI_PHY(Rx)325 is the transmission function unit in the physical layer of the user network interface. UNI_PHY(Tx)324 outputs an electrical signal corresponding to the main signal (user signal) to the processing unit 323 by executing a predetermined transmission process. The user-side transmitter (Tx) transmits the signal to the user side. The network-side transmitter (Tx) transmits the signal to the network side.

[0205] The transmitting optical interface unit 326 (optical IF unit) converts the electrical signal output from the splitting unit 322 into an optical signal. Thus, the optical transceiver 301 may perform the process of converting electrical signals into optical signals internally. The optical interface unit 326 outputs the converted optical signal to the reflection / transmission unit 350. The receiving optical interface unit 326 converts the optical signal back into an electrical signal. If the optical signal is not looped back, the optical interface unit performs OE conversion or EO (Electrical-Optical conversion). If the reflection / transmission unit 350 does not transmit the optical signal, the optical interface unit performs OE conversion or EO conversion during loopback. Also, if the optical signal from the network is folded back, a portion of it is branched and received, and a portion of the optical signal is multiplexed into the folded-back optical signal, the optical interface unit performs OE conversion or EO conversion during loopback. UNI_PHY(Rx)325 receives the signal from the user side. The received signal is output to the network side via the device. The received signal may be terminated within the device. UNI_PHY(Tx)324 outputs signals from the network side or from within the device to the user side. The UNI_PHY(Rx)325 side of the optical interface receives signals from the network. The received signal is output to the user side via the device. The received signal may be terminated within the device. The UNI_PHY(Tx)324 side of the optical interface outputs signals from the user side or from within the device to the network side. Note that the user-side receiver (Rx) and the network-side receiver (Rx) are not shown.

[0206] The access system management control unit 103 includes a determination control unit 401, an optical interface unit (optical IF unit) 405, an optical interface unit (optical IF unit) 406, a matching / separating unit 407, a matching / separating unit 408, and a wavelength sweep instruction unit 11.

[0207] The wavelength sweep instruction unit 11 performs the same processing as the wavelength sweep instruction unit 11 in the first embodiment. Specifically, the wavelength sweep instruction unit 11 instructs the light source 12 provided in the optical interface unit 405 to sweep the wavelength channels to be checked for continuity. The wavelength sweep instruction unit 11 may instruct the light source 12 at any timing during initial setup, or it may instruct the light source 12 at the timing when the access system management control unit 103 transmits a control signal.

[0208] The optical interface unit 405 converts the control signal output from the determination control unit 401 into an optical signal. The optical interface unit 405 outputs the converted optical signal to the matching / separating unit 407. Furthermore, the optical interface unit 405 is equipped with the light source 12 in the first embodiment and sequentially transmits optical signals of each wavelength included in the sweep width instructed by the wavelength sweep instruction unit 11.

[0209] The optical interface unit 406 acquires the optical signal output from the matching / separating unit 408. The optical interface unit 406 converts the acquired optical signal into an electrical signal. The optical interface unit 406 outputs the electrical signal obtained by the conversion to the determination control unit 401.

[0210] Furthermore, the optical interface unit 406 includes a response receiving unit 13 and a wavelength sweep identification unit 14 in the third embodiment, and performs the same processing as the optical transceiver 15 in the third embodiment. For example, the response receiving unit 13 receives a control signal separated by the combination / separation unit 408. The response receiving unit 13 identifies the conduction width based on the received control signal (optical signal) and the information held by the wavelength sweep identification unit 14.

[0211] The access system management control unit 103 shown in Figure 17 does not necessarily have to include the coupling / canceling unit 407 and coupling / canceling unit 408 as shown in Figure 12. In this configuration, the optical interface unit 405 of the access system management control unit 103 converts the control signal, which is an electrical signal output from the determination control unit 401, into an optical signal, and transmits the converted optical signal to the user device 300 via the transmission line 35. The optical signal is folded back by the reflection / transmission unit 350 of the user device 300 and received by the optical interface unit 406 of the access system management control unit 103. The optical interface unit 406 determines the conduction width based on the received control signal (optical signal) and the information held by the wavelength sweep identification unit 14.

[0212] The access system management control unit 103 shown in Figure 17 may loop back the main signal at the user device 300 as shown in Figure 15, and determine the conduction width based on the looped-back optical signal.

[0213] Figure 17 shows a configuration in which the reflective transmission unit 350 is provided in the user device 300, but the reflective transmission unit 350 may also be provided in the Ph-GW100. If the reflective transmission unit 350 is provided in the Ph-GW100, the reflective transmission unit 350 may use the fourth function of the Ph-GW100, which is the reverse function.

[0214] (Sixth Embodiment) In the sixth embodiment, a configuration in which the configurations shown in the first to third embodiments are applied to a WDM-PON (WDM-Passive Optical Network) will be described. Specifically, in the sixth embodiment, in a communication system in which an OLT (Optical Line Terminal) and one or more ONUs (Optical Network Units) are connected via a WDM coupler that performs multiplexing and demultiplexing of optical signals such as an AWG (Arrayed Waveguide Grating), the conduction width of the WDM coupler is specified.

[0215] Figure 18 shows an example configuration of communication system 1d in the sixth embodiment. Communication system 1d comprises an OLT 510, one or more ONUs 520, and a WDM coupler 530. The OLT 510 and the WDM coupler 530, and the one or more ONUs 520 and the WDM coupler 530 are connected via optical fiber.

[0216] The OLT510 is an optical line termination device installed on the central office side. The OLT510 comprises, for example, one of the following configurations: optical transmitters 10, 10a, or optical transceivers 15, and performs the same processing as any of the optical transmitters 10, 10a, or optical transceivers 15 of the first to third embodiments.

[0217] The ONU520 is an optical subscriber line termination device installed on the customer side. The ONU520 comprises, for example, one of the optical receivers 20, 20a, or 20b and performs the same processing as any of the optical receivers 20, 20a, or 20b in the first to third embodiments.

[0218] The WDM coupler 530 is a device that performs multiplexing and demultiplexing of optical signals such as AWG (Arrayed Waveguide Grating).

[0219] In the case of WDM-PON, which uses the same route for both outbound and return journeys, the characteristics of the one-way journey are easily estimated because the same characteristics are traversed twice along the same route. For example, if it can be approximated as a Gaussian, the characteristics of the one-way journey can be estimated by halving the exponent.

[0220] With the communication system 1d in the sixth embodiment configured as described above, the same effects as those of any of the first to fourth embodiments can be obtained even with WDM-PON.

[0221] (Example hardware configuration) Figure 19 shows an example of the hardware configuration of communication systems 1a, 1b, 1c, and 1d in an embodiment. Some or all of the functional units of communication systems 1a, 1b, 1c, and 1d are implemented as software by one or more processors 201, such as a CPU, executing a program stored in a storage device 203 having a non-volatile recording medium (non-temporary recording medium) and a memory 202. The program may be recorded on a computer-readable non-temporary recording medium. A computer-readable non-temporary recording medium is, for example, a portable medium such as a flexible disk, magneto-optical disk, ROM, CD-ROM, or a storage device such as a hard disk built into a computer system. The communication unit 204 performs predetermined communication processing. The communication unit 204 may acquire data of an optical signal transmitted through an optical fiber (e.g., main signal data, wavelength data) and a program.

[0222] Some or all of the functional parts of communication systems 1a, 1b, 1c, and 1d may be implemented using hardware including electronic circuits (or circuits) such as LSIs (Large Scale Integrated Circuits), ASICs, PLDs, or FPGAs.

[0223] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention. [Industrial applicability]

[0224] The present invention is applicable to optical communication systems such as all-photonic networks (APNs). [Explanation of symbols]

[0225] 1, 1a, 1b, 1c, 1d…Communication system, 10, 10a…Optical transmitter, 11…Wavelength sweep instruction unit, 12…Light source, 13…Response receiving unit, 14…Wavelength sweep identification unit, 15…Optical transceiver, 18…Folding device, 20, 20a, 20b…Optical receiver, 21…Receiver, 22…Wavelength sweep identification unit, 23…Response unit, 24, 350…Reflection transmission unit, 100…Ph-GW, 101…Optical distribution unit, 102…Wavelength division multiplexing / deletion unit, 103…Access system management control unit, 200…APN controller, 201…Processor, 202…Memory, 203…Storage device, 204 ...Communication unit, 300...User equipment, 301...Optical transceiver, 321, 326...Optical interface unit (Optical IF unit), 322, 407, 408...Matching / separating unit, 323...Processing unit, 324...UNI_PHY(Tx), 325...UNI_PHY(Rx), 330...Control unit, 331...Control signal receiving unit, 332...Control signal transmitting unit, 333...Loopback unit, 401...Decision control unit, 404...Matching / separating unit, 405, 406...Optical interface unit (Optical IF unit), 409...Modulation unit, 410...Monitor unit, 510...OLT, 520...ONU, 530...WDM coupler

Claims

1. A communication system comprising a first optical communication device, a second optical communication device, and an optical transmission path connecting the first optical communication device and the second optical communication device, The first optical communication device is A transmitting unit that transmits a modulated optical signal to the second optical communication device via the optical transmission path at a wavelength in the wavelength range obtained by excluding the one-sided modulation sideband of the modulation from the wavelength range used to check the transmission characteristics in the optical transmission path. Equipped with, A specific unit that identifies the transmission characteristics in the optical transmission path based on the optical signal transmitted from the first optical communication device, A communication system equipped with [the following features].

2. A communication system comprising a first optical communication device, a second optical communication device, and an optical transmission path connecting the first optical communication device and the second optical communication device, The first optical communication device is A transmitting unit that transmits an optical signal to the second optical communication device via the optical transmission path at a wavelength within the wavelength range for confirming the transmission characteristics in the optical transmission path. Equipped with, The second optical communication device is A unit that identifies the transmission characteristics in the optical transmission path based on the optical signal transmitted from the first optical communication device, A wavelength sweep identification unit that shares and stores information about each optical signal with the first optical communication device in advance, Equipped with, The identification unit identifies the transmission characteristics in the optical transmission path using the optical signal transmitted from the first optical communication device and the optical signal information held by the wavelength sweep identification unit. Communication system.

3. A communication system comprising a first optical communication device, a second optical communication device, and an optical transmission path connecting the first optical communication device and the second optical communication device, The first optical communication device is A transmitting unit that transmits an optical signal to the second optical communication device via the optical transmission path at a wavelength within a wavelength range for confirming the transmission characteristics in the optical transmission path, A unit for identifying the transmission characteristics in the optical transmission path, Equipped with, The second optical communication device is A receiving unit that receives optical signals of each wavelength transmitted from the first optical communication device and converts them into electrical signals, A response unit that responds to the first optical communication device with information on the received strength of the electrical signal, or notification of whether or not the signal can be received according to the received strength of the electrical signal, Equipped with, The identifying unit identifies the transmission characteristics in the optical transmission path based on the response transmitted from the second optical communication device. Communication system.

4. A communication system comprising a first optical communication device, a second optical communication device, and an optical transmission path connecting the first optical communication device and the second optical communication device, The first optical communication device is A transmitting unit that transmits an optical signal to the second optical communication device via the optical transmission path at a wavelength within a wavelength range for confirming the transmission characteristics in the optical transmission path, A unit that identifies the transmission characteristics in the optical transmission path based on the optical signal transmitted from the first optical communication device, Equipped with, The second optical communication device is A re-folding unit that returns the optical signal transmitted from the first optical communication device to the first optical communication device while keeping it as light, Equipped with, The specified unit identifies the transmission characteristics in the optical transmission path based on the optical signal folded back from the second optical communication device. Communication system.

5. Each transmitting unit of the first optical communication device modulates and transmits an optical signal. The wavelength sweep range is the wavelength range obtained by subtracting the one-sided modulation sideband from the predetermined wavelength sweep range. The communication system according to any one of claims 2 to 4.

6. The system further includes a determination control unit that determines whether a signal path, including the signal path between the first optical communication device and the second optical communication device, and the signal path inside the device, is normal. The first optical communication device transmits an optical signal to the second optical communication device via the optical transmission path by sweeping the wavelength, either in the same way as or after the process for determining whether the signal path is normal. A communication system according to any one of claims 1 to 4.

7. The first optical communication device in a communication system comprising a first optical communication device, a second optical communication device, and an optical transmission path connecting the first optical communication device and the second optical communication device, A transmitting unit that sweeps the modulated optical signal over a wavelength range obtained by excluding the one-sided modulation sideband of the modulation from the wavelength range used to check the transmission characteristics in the optical transmission path, and transmits it to the second optical communication device via the optical transmission path. A specific unit that receives either the result of receiving an optical signal or an optical signal folded back from the second optical communication device, and identifies the transmission characteristics in the optical transmission path, A first optical communication device comprising:

8. The second optical communication device in a communication system comprising a first optical communication device, a second optical communication device, and an optical transmission path connecting the first optical communication device and the second optical communication device, A specification unit that identifies the transmission characteristics in the optical transmission path based on an optical signal obtained by sweeping the wavelength transmitted from the first optical communication device, A wavelength sweep identification unit that shares and stores information about each optical signal with the first optical communication device in advance, Equipped with, The identification unit is a unit that identifies the transmission characteristics in the optical transmission path using the optical signal transmitted from the first optical communication device and the optical signal information held by the wavelength sweep identification unit. The second optical communication device.

9. The first optical communication device in a communication system comprising a first optical communication device, a second optical communication device, and an optical transmission path connecting the first optical communication device and the second optical communication device, A transmitting unit that transmits an optical signal with a swept wavelength to the second optical communication device via the optical transmission path, A specific unit that receives optical signals of each wavelength transmitted from the first optical communication device transmitted by the second optical communication device, converts them into electrical signals, receives information on the received strength of the electrical signals, or a notification of whether reception is possible according to the received strength of the electrical signals, and identifies the transmission characteristics in the optical transmission path, A first optical communication device comprising:

10. The first optical communication device in a communication system comprising a first optical communication device, a second optical communication device, and an optical transmission path connecting the first optical communication device and the second optical communication device, A transmitting unit that transmits an optical signal with a swept wavelength to the second optical communication device via the optical transmission path, A unit that receives the optical signal folded back from the second optical communication device and identifies the transmission characteristics in the optical transmission path, A first optical communication device comprising:

11. A method for determining the characteristics of a transmission path in a communication system comprising a first optical communication device, a second optical communication device, and an optical transmission path connecting the first optical communication device and the second optical communication device, The first optical communication device transmits the modulated optical signal to the second optical communication device via the optical transmission path at a wavelength in the wavelength range obtained by excluding the one-sided modulation sideband of the modulation from the wavelength range used to check the transmission characteristics in the optical transmission path. The identification unit identifies the transmission characteristics in the optical transmission path based on the optical signal transmitted from the first optical communication device. Method for determining transmission line characteristics.

12. A method for determining the characteristics of a transmission path in a communication system comprising a first optical communication device, a second optical communication device, and an optical transmission path connecting the first optical communication device and the second optical communication device, The first optical communication device transmits an optical signal to the second optical communication device via the optical transmission path at a wavelength within the wavelength range for confirming the transmission characteristics in the optical transmission path. The second optical communication device uses information on optical signals that it has previously shared and held with the first optical communication device to determine the transmission characteristics in the optical transmission path based on the optical signal transmitted from the first optical communication device. Method for determining transmission line characteristics.

13. A method for determining the characteristics of a transmission path in a communication system comprising a first optical communication device, a second optical communication device, and an optical transmission path connecting the first optical communication device and the second optical communication device, The first optical communication device transmits an optical signal to the second optical communication device via the optical transmission path at a wavelength within the wavelength range for confirming the transmission characteristics in the optical transmission path. The second optical communication device receives the optical signal transmitted from the first optical communication device, converts it into an electrical signal, and responds to the first optical communication device with information on the received strength of the converted electrical signal, or with notification of whether or not reception is possible according to the received strength of the electrical signal. The identification unit identifies the transmission characteristics in the optical transmission path based on the response transmitted from the second optical communication device. Method for determining transmission line characteristics.

14. A method for determining the characteristics of a transmission path in a communication system comprising a first optical communication device, a second optical communication device, and an optical transmission path connecting the first optical communication device and the second optical communication device, The first optical communication device transmits to the second optical communication device via the optical transmission path at a wavelength within the wavelength range for confirming the transmission characteristics in the optical transmission path. The second optical communication device returns the optical signal transmitted from the first optical communication device to the first optical communication device as light, The first optical communication device determines the transmission characteristics in the optical transmission path based on the optical signal folded back from the second optical communication device. Method for determining transmission line characteristics.

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