Communication device, communication system, and zero dispersion wavelength estimation method

Abstract

This communication device comprises: a transmitting unit that transmits optical signals of one or more wavelengths; one or more receiving units that receive a plurality of optical signals of different wavelengths transmitted from a communication partner communication device connected via an optical transmission path, and a portion of the optical signals of one or more wavelengths transmitted from the transmission unit; and a signal processing unit that, on the basis of the portion of the optical signals of one or more wavelengths transmitted from the transmission unit, acquires pre-transmission data for use when detecting frequencies that have been attenuated due to wavelength dispersion, and estimates a zero dispersion wavelength on the basis of the acquired pre-transmission data and frequency spectra of each of the plurality of optical signals.　

Description

Communication device, communication system, and zero-dispersion wavelength estimation method

[0001] The present invention relates to a communication device, a communication system, and a zero-dispersion wavelength estimation method.

[0002] In optical communication systems that transmit optical signals using optical fibers, if the wavelength deviates from the zero-dispersion wavelength of the optical fiber, the effect of dispersion increases, leading to a larger penalty and making long-distance transmission difficult. Therefore, in order to transmit over long distances, it is necessary to set the wavelength to approach the zero-dispersion wavelength.

[0003] However, because optical fibers exhibit fluctuations in the zero-dispersion wavelength between 1300 and 1324 nm, there is a problem in that the wavelength cannot be set unless the zero-dispersion wavelength value for each optical fiber used is known.

[0004] Therefore, a conventional method for setting the wavelength is to use an OTDR (Optical Time Domain Reflectometer). In this method, for example, light emitted from the OTDR of device A is transmitted to device B, and then reflected back to the OTDR of device A by a mirror in device B to measure the zero dispersion value, thereby switching the path between the transmitter and receiver. However, this method has the problem of complicating the system because it requires additional equipment.

[0005] As described above, a method has also been proposed for estimating the zero-dispersion wavelength of an optical fiber with a simple configuration that does not require additional equipment (see, for example, Patent Document 1). In the method described in Patent Document 1, when detecting the notch frequency, which is the frequency attenuated due to wavelength dispersion, the notch frequency can be detected with greater accuracy by dividing the pre-transmission spectrum data (frequency spectrum data when sent back-to-back) that is held in advance by the spectrum data after transmission (for example, the frequency spectrum of the optical signal received at the receiving end) (taking the difference when viewing the intensity in decibels).

[0006] International Publication No. 2024 / 134710

[0007] However, the method described in Patent Document 1 requires experiments with a pair of transceivers acting as communication partners before the transceivers are shipped or put into operation, in order to obtain the pre-transmission spectral data used to detect the notch frequency. This has resulted in the problem of increased operational costs for estimating the zero-dispersion wavelength of optical fibers in optical communication using optical fibers.

[0008] In view of the above circumstances, the present invention aims to provide a technology that can suppress the increase in operating costs for estimating the zero-dispersion wavelength of optical fibers in optical communications using optical fibers.

[0009] One aspect of the present invention is a communication device comprising: a transmitting unit that transmits one or more optical signals of wavelengths; a plurality of optical signals of different wavelengths transmitted from a communication device of a communication partner connected via an optical transmission path; one or more receiving units that receive a portion of the one or more optical signals of wavelengths transmitted from the transmitting unit; and a signal processing unit that acquires pre-transmission data used to detect frequencies attenuated due to chromatic dispersion based on a portion of the one or more optical signals of wavelengths transmitted from the transmitting unit, and estimates zero-dispersion wavelengths based on the acquired pre-transmission data and the frequency spectra of each of the plurality of optical signals.

[0010] One aspect of the present invention is an optical communication system comprising a first communication device and a second communication device connected via an optical transmission path, wherein the first communication device includes a transmitting unit that transmits a plurality of optical signals of different wavelengths to the second communication device via the optical transmission path, and the second communication device includes a transmitting unit that transmits one or more optical signals of one or more wavelengths, one or more receiving units that receive the plurality of optical signals of different wavelengths transmitted from the first communication device and a portion of the one or more optical signals of one or more wavelengths transmitted from the transmitting unit, and a signal processing unit that acquires pre-transmission data used to detect frequencies attenuated due to chromatic dispersion based on a portion of the one or more optical signals of one or more wavelengths transmitted from the transmitting unit, and estimates a zero-dispersion wavelength based on the acquired pre-transmission data and the frequency spectrum of each of the plurality of optical signals.

[0011] One aspect of the present invention is a zero-dispersion wavelength estimation method that transmits one or more optical signals of one or more wavelengths, receives a plurality of optical signals of different wavelengths transmitted from a communication device of a communication partner connected via an optical transmission path, and a portion of the one or more optical signals of one or more wavelengths transmitted from the device itself, acquires pre-transmission data used to detect frequencies attenuated due to chromatic dispersion based on the portion of the one or more optical signals, and estimates the zero-dispersion wavelength based on the acquired pre-transmission data and the frequency spectrum of each of the plurality of optical signals.

[0012] This invention makes it possible to suppress the increase in operating costs for estimating the zero-dispersion wavelength of optical fibers in optical communications using optical fibers.

[0013] This figure shows an example configuration of the optical communication system in the first embodiment. This is a sequence diagram showing the processing flow in the optical communication system of the first embodiment. This figure shows another example configuration of the optical communication system in the first embodiment. This figure shows an example configuration of the optical communication system in the second embodiment. This is a sequence diagram showing the processing flow in the optical communication system of the second embodiment. This figure shows another example configuration of the optical communication system in the second embodiment. This figure shows an example configuration of the optical communication system in the third embodiment. This is a sequence diagram showing the processing flow in the optical communication system of the third embodiment. This figure shows another example configuration of the optical communication system (part 1) in the third embodiment. This figure shows another example configuration of the optical communication system (part 2) in the third embodiment. This figure shows another example configuration of the optical communication system (part 3) in the third embodiment. This figure shows another example configuration of the optical communication system in the fourth embodiment (part 1). This figure shows another example configuration of the optical communication system in the fourth embodiment (part 2). This figure shows another example configuration of the optical communication system in the fourth embodiment (part 3). This figure shows another example configuration of the optical communication system in the fourth embodiment (part 4). This figure shows another example configuration of the optical communication system in the fourth embodiment (part 5). This figure shows an example configuration of the optical communication system in the fifth embodiment. This figure shows another configuration example (1) of the optical communication system in the fifth embodiment. This figure shows another configuration example (2) of the optical communication system in the fifth embodiment. This figure shows another configuration example (3) of the optical communication system in the fifth embodiment. This figure shows an example of an optical communication system configuration applicable to each embodiment.

[0014] One embodiment of the present invention will be described below with reference to the drawings.

[0015] (First Embodiment) Figure 1 shows an example of the configuration of the optical communication system 10 in the first embodiment. The optical communication system 10 comprises a communication device 100A and a communication device 100B. Communication device 100A and communication device 100B perform optical communication via an optical transmission path. The optical transmission path is made of optical fiber. One or more optical amplifiers that amplify the amplitude of optical signals may be installed in the optical transmission path. Communication device 100A and communication device 100B communicate by two-core transmission using two optical transmission paths.

[0016] In the following description, the direction from communication device 100A to communication device 100B is referred to as the downstream direction, and the direction from communication device 100B to communication device 100A is referred to as the upstream direction. Furthermore, the optical transmission path used by communication device 100A for downstream communication is referred to as the downstream optical transmission path, and the optical transmission path used by communication device 100B for upstream communication is referred to as the upstream optical transmission path.

[0017] The communication device 100A includes a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a plurality of receiving units 140A-1 to 140A-2, and an optical distribution unit 150A.

[0018] The receiving unit 140A-1 receives the optical signal transmitted by the transmitting unit 130A of its own device. The receiving unit 140A-2 receives the optical signal transmitted from the communication device 100B. In this way, the communication device 100A is equipped with multiple receiving units 140A in order to receive not only optical signals transmitted by other communication devices but also optical signals transmitted by its own device.

[0019] The signal processing unit 110A performs various signal processing on the optical signals received by each receiving unit 140A. Furthermore, the signal processing unit 110A sets the wavelength of the optical signal to be transmitted by the transmitting unit 130A. The signal processing unit 110A maintains correspondence information that shows the correspondence between wavelength and temperature. For example, the correspondence information includes information indicating the temperature of the laser corresponding to each wavelength, associated with each wavelength. That is, the correspondence information includes the wavelength λ １ This includes information such as temperature T1 associated with a specific point and temperature T2 associated with a specific wavelength λ2. Note that this is just an example, and the temperature values ​​are determined within a predetermined range.

[0020] Therefore, the signal processing unit 110A obtains temperature information corresponding to the wavelength used for communication by referring to the correspondence information, and sets the temperature controller 120A to the temperature indicated by the obtained temperature information. For example, when the signal processing unit 110A obtains information regarding the transmission wavelength from the communication device 100B, it obtains temperature information corresponding to the wavelength specified by the obtained information regarding the transmission wavelength by referring to the correspondence information, and sets the temperature controller 120A to the temperature indicated by the obtained temperature information. The information regarding the transmission wavelength is information indicating the wavelength used by the communication device 100A to communicate with the communication device 100B, and may be, for example, information indicating the zero-dispersion wavelength. As a result, the signal processing unit 110A sets the wavelength of the optical signal to be transmitted to the communication device 100B in the transmission unit 130A.

[0021] Furthermore, the signal processing unit 110A sets the wavelength of the optical signal to be transmitted by the transmitting unit 130A during operation in order to acquire BtB frequency spectrum data during operation (for example, before or during actual communication). The signal processing unit 110A acquires BtB frequency spectrum data based on the optical signal received by the receiving unit 140A-1.

[0022] The signal processing unit 110A may also have a function for estimating the zero-dispersion wavelength. When the signal processing unit 110A estimates the zero-dispersion wavelength, it estimates it based on the frequency spectrum data of BtB acquired during operation and the optical signals of different wavelengths received by the receiving unit 140A-2. The method for estimating the zero-dispersion wavelength will be described later. In this embodiment, the case in which the zero-dispersion wavelength is estimated in the communication device 100B will be explained as an example.

[0023] The temperature controller 120A adjusts the temperature of the transmitting unit 130A so that it reaches the temperature set by the signal processing unit 110A.

[0024] The transmitting unit 130A is, for example, a tunable laser, and transmits an optical signal with a wavelength corresponding to the temperature adjusted by the temperature controller 120A. In this embodiment, the transmitting unit 130A transmits signals with different wavelengths (for example, wavelength λ ａ and wavelength λｂ The transmitter unit 130A in this embodiment transmits an optical signal of a predetermined wavelength (for example, wavelength λ) in order to acquire frequency spectrum data of BtB.

[0025] The optical distribution unit 150A is positioned at the output destination of the transmitting unit 130A. The optical distribution unit 150A outputs the input optical signal to a predetermined output destination. The optical distribution unit 150A has one or more first ports and L (where L is an integer of 2 or more) second ports. The optical distribution unit 150A may be, for example, a 1 × L optical switch. The first ports of the optical distribution unit 150A are connected to the transmitting unit 130A, and each of the second ports of the optical distribution unit 150A is connected to a downstream optical transmission path and to the receiving unit 140A-1.

[0026] When the optical distribution unit 150A acquires frequency spectrum data of BtB, the connection path between ports is controlled to connect the transmitting unit 130A and the receiving unit 140A-1. When the optical distribution unit 150A communicates with the communication device 100B, the connection path between ports is controlled to connect the transmitting unit 130A and the downstream optical transmission path. The control of the connection path of the optical distribution unit 150A is performed by a control unit (not shown). Thus, the optical distribution unit 150A is an optical component that switches the direction of optical output so that the optical signal transmitted by the device can be received by the device.

[0027] Furthermore, when acquiring BtB frequency spectrum data, the light intensity can be kept within the receiving sensitivity of the receiving unit 140A-1 by weakening the optical output of the transmitting unit 130A. Alternatively, the light intensity can be kept within the receiving sensitivity of the receiving unit 140A-1 by placing an optical attenuator that attenuates the intensity of the optical signal to a predetermined level before (for example, between the transmitting unit 130A and the optical splitting unit 150A) or after (for example, between the optical splitting unit 150A and the receiving unit 140A-1). The optical attenuator may also be provided inside the optical splitting unit 150A.

[0028] The communication device 100B includes a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a plurality of receiving units 140B-1 to 140B-2, and an optical distribution unit 150B.

[0029] The receiving unit 140B-1 receives the optical signal transmitted by the transmitting unit 130B of its own device. The receiving unit 140B-2 receives the optical signal transmitted from the communication device 100A. For example, the receiving unit 140B receives optical signals of different wavelengths transmitted from the communication device 100A. In this way, the communication device 100B is equipped with multiple receiving units 140B in order to receive not only optical signals transmitted by other communication devices but also optical signals transmitted by its own device.

[0030] The signal processing unit 110B performs various signal processing on the optical signals received by each receiving unit 140B. Furthermore, the signal processing unit 110B acquires frequency spectrum data of BtB based on the optical signals received by the receiving unit 140B-1. Then, the signal processing unit 110B estimates the zero-dispersion wavelength based on the received optical signals of different wavelengths and the acquired frequency spectrum data of BtB. The method for estimating the zero-dispersion wavelength will be described later.

[0031] The signal processing unit 110B, like the signal processing unit 110A, stores correspondence information indicating the relationship between wavelength and temperature. By referring to the correspondence information, the signal processing unit 110B obtains temperature information corresponding to the wavelength used for communication and sets the temperature controller 120B to the temperature indicated by the obtained temperature information.

[0032] Furthermore, the signal processing unit 110B sets the wavelength of the optical signal to be transmitted by the transmitting unit 130B during operation in order to acquire BtB frequency spectrum data during operation (for example, before or during actual communication).

[0033] The temperature controller 120B adjusts the temperature of the transmission unit 130B so that it reaches the set temperature.

[0034] The transmitting unit 130B is, for example, a tunable laser, and transmits an optical signal with a wavelength corresponding to the temperature adjusted by the temperature controller 120B. In addition, the transmitting unit 130B in this embodiment transmits an optical signal of a predetermined wavelength (for example, wavelength λ) in order to acquire frequency spectrum data of BtB.

[0035] The optical distribution unit 150B is positioned at the output destination of the transmitting unit 130B. The optical distribution unit 150B outputs the input optical signal to a predetermined output destination. The optical distribution unit 150B has one or more first ports and L second ports. The optical distribution unit 150B may be, for example, a 1 × L optical switch. The first ports of the optical distribution unit 150B are connected to the transmitting unit 130B, and each of the second ports of the optical distribution unit 150B is connected to an upstream optical transmission path and to the receiving unit 140B-1.

[0036] When the optical distribution unit 150B acquires frequency spectrum data of BtB, the connection path between ports is controlled to connect the transmitting unit 130B and the receiving unit 140B-1. When the optical distribution unit 150B communicates with the communication device 100A, the connection path between ports is controlled to connect the transmitting unit 130B and the uplink optical transmission path. The control of the connection path of the optical distribution unit 150B is performed by a control unit (not shown). Thus, the optical distribution unit 150B is an optical component that switches the direction of optical output so that it can receive optical signals transmitted by its own device.

[0037] Furthermore, when acquiring frequency spectrum data of BtB, the light intensity can be kept within the receiving sensitivity of the receiving unit 140B-1 by weakening the optical output of the transmitting unit 130B. Alternatively, the light intensity can be kept within the receiving sensitivity of the receiving unit 140B-1 by placing an optical attenuator that attenuates the intensity of the optical signal to a predetermined level before (for example, between the transmitting unit 130B and the optical attenuator 150B) or after (for example, between the optical attenuator 150B and the receiving unit 140B-1). The optical attenuator may also be provided inside the optical attenuator 150B.

[0038] In the following explanation, communication device 100A will be described as the transmitting communication device, and communication device 100B will be described as the receiving communication device. As mentioned above, the receiving communication device has not only a wavelength setting function but also a function to estimate the zero-dispersion wavelength in the signal processing unit. Since communication devices 100A and 100B have similar configurations, communication device 100A also has a function to estimate the zero-dispersion wavelength in addition to the wavelength setting function. Therefore, communication device 100A can also estimate the zero-dispersion wavelength.

[0039] [Operation of Optical Communication System 10] Next, the processing flow in the optical communication system 10 will be described. Figure 2 is a sequence diagram showing the processing flow in the optical communication system 10 of the first embodiment. At the start of processing in Figure 2, the optical distribution unit 150A is controlled to connect the transmission unit 130A with the downstream optical transmission path.

[0040] The optical distribution unit 150B of the communication device 100B sets a connection path to connect the transmitting unit 130B and the receiving unit 140B-1 in accordance with the control of a control unit (not shown) (step S101). As a result, the optical signal transmitted from the transmitting unit 130B is input to the receiving unit 140B-1 via the optical distribution unit 150B. In other words, the optical signal transmitted from the transmitting unit 130B is not output to the upstream optical transmission path.

[0041] The communication device 100B transmits an optical signal of an arbitrary wavelength λ. Specifically, the signal processing unit 110B obtains temperature information corresponding to wavelength λ by referring to correspondence information. The signal processing unit 110B sets the temperature controller 120B to the temperature indicated by the obtained temperature information. The temperature controller 120B adjusts the temperature of the transmitting unit 130B to the set temperature. As a result, the transmitting unit 130B transmits an optical signal of wavelength λ.

[0042] The optical signal of wavelength λ transmitted from the transmitting unit 130B is input to the first port of the optical distribution unit 150B. The optical distribution unit 150B forwards the optical signal of wavelength λ input to the first port to the second port to which the receiving unit 140B-1 is connected. As a result, the optical distribution unit 150B outputs the optical signal of wavelength λ from the second port to which the receiving unit 140B-1 is connected. The optical signal of wavelength λ output from the second port of the optical distribution unit 150B is then received by the receiving unit 140B-1.

[0043] The receiving unit 140B-1 outputs the received optical signal with wavelength λ to the signal processing unit 110B. The signal processing unit 110B creates a frequency spectrum from the optical signal with wavelength λ output from the receiving unit 140B-1. As a result, the signal processing unit 110B acquires the frequency spectrum data of BtB (step S102). The signal processing unit 110B stores the acquired frequency spectrum data of BtB in a memory not shown.

[0044] Subsequently, the optical distribution unit 150B sets a connection path to connect the transmitting unit 130B and the upstream optical transmission path, in accordance with the control of a control unit (not shown) (step S103). As a result, the optical signal transmitted from the transmitting unit 130B is input to the communication device 100A via the upstream optical transmission path. In other words, the optical signal transmitted from the transmitting unit 130B is not output to the receiving unit 140B-1.

[0045] The communication device 100A uses a wavelength λ ａ The optical signal is transmitted (step S104). Specifically, the signal processing unit 110A refers to the corresponding information and determines the wavelength λ ａ The system acquires temperature information corresponding to the wavelength λ. The signal processing unit 110A sets the temperature controller 120A to the temperature indicated by the acquired temperature information. The temperature controller 120A adjusts the temperature of the transmitting unit 130A to the set temperature. As a result, the transmitting unit 130A transmits at a wavelength λ ａ It transmits an optical signal.

[0046] Note that there is no particular restriction on the data pattern on the transmission side, and for example, a 01 signal or a PRBS (Pseudo-Random Binary Sequence) signal is also possible. There is also no particular restriction on the modulation method, and an NRZ (Non Return to Zero) signal or a PAM4 (Pulse Amplitude Modulation 4) signal is also possible.

[0047] The wavelength λ transmitted from the transmitter 130A ａ 's optical signal is input to an optical splitter 150A. In the optical splitter 150A, control is performed so as to connect the transmitter 130A and the downstream optical transmission path, so the optical splitter 150A outputs the input wavelength λ ａ 's optical signal to the downstream optical transmission path. The wavelength λ output from the optical splitter 150A ａ 's optical signal propagates through the downstream optical transmission path and reaches the communication device 100B. The receiver 140B-2 of the communication device 100B receives the wavelength λ that has propagated through the downstream optical transmission path ａ 's optical signal (step S105).

[0048] The receiver 140B-2 outputs the received wavelength λ ａ 's optical signal to a signal processing unit 110B. The signal processing unit 110B, based on the wavelength λ output from the receiver 140B-2 ａ 's optical signal and the BtB frequency spectrum data stored in a memory (not shown), calculates the notch frequency at which a notch appears at a position other than a frequency multiple of the wavelength λ ａ 's optical signal. The notch frequency is a position where the slope of the average line of the frequency spectrum changes from negative to positive, and is a position other than a frequency multiple of the transmission signal of the opposing device (e.g., the communication device 100A).

[0049] Specifically, the signal processing unit 110B receives the wavelength λ ａA first frequency spectrum is created from the optical signal. Next, the signal processing unit 110B divides the created first frequency spectrum by the frequency spectrum data of BtB stored in memory (not shown) (since the spectral intensity is expressed in dB, the difference is taken in dB) to obtain a frequency spectrum for estimating the zero-dispersion wavelength (hereinafter referred to as the "estimation frequency spectrum"). Then, based on the obtained estimation frequency spectrum, the signal processing unit 110B calculates the wavelength λ ａ The notch frequency f is the frequency at which a notch appears outside of the frequency multiples of the optical signal. ｎ,ａ The notch frequency f is calculated (step S106). ｎ,ａ is the wavelength λ ａ In the frequency spectrum of an optical signal, this refers to the (n+1)th notch frequency from the low-frequency side. Here, n is a non-negative integer.

[0050] Subsequently, the communication device 100A uses a wavelength λ ｂ The optical signal is transmitted (step S107). Specifically, first the signal processing unit 110A of the communication device 100A refers to the correspondence information and determines the wavelength λ ｂ The system acquires temperature information corresponding to the wavelength λ. The signal processing unit 110A sets the temperature controller 120A to the temperature indicated by the acquired temperature information. The temperature controller 120A adjusts the temperature of the transmitting unit 130A to the set temperature. As a result, the transmitting unit 130A transmits at a wavelength λ ｂ It transmits an optical signal.

[0051] The processing in step S107 may be performed at a predetermined time interval (for example, 10 seconds) after the start time of the processing in step S104, or it may be performed using a low-speed control channel, a different wavelength, or a different line control that is different from the main signal. This can be achieved if the communication devices 100A and 100B have functions to read high-speed, low-speed, or waveforms. The start timing and execution method of the processing in step S107 described above are just examples, and other start timings and execution methods may be used.

[0052] Note that the wavelengths used by the communication device 100A in steps S104 and S107 only need to be pre-set; for example, two wavelengths can be selected from among a plurality of wavelengths that the transmitting unit 130A can output. In Figure 4, for the sake of simplicity, a configuration is shown in which the communication device 100A transmits optical signals of different wavelengths at different timings, but the communication device 100A may also transmit two optical signals of two wavelengths simultaneously.

[0053] Wavelength λ transmitted from the transmitting unit 130A ｂ The optical signal is input to the optical splitter 150A. The optical splitter 150A is controlled to connect the transmitter 130A and the downstream optical transmission path, so the optical splitter 150A receives the input wavelength λ ｂ The optical signal is output to the downstream optical transmission path. The wavelength λ output from the optical distribution unit 150A ｂ The optical signal propagates down the optical transmission path and reaches the communication device 100B. The receiving unit 140B-2 of the communication device 100B receives the optical signal that has propagated down the optical transmission path (step S108). The receiving unit 140B-2 outputs the received optical signal to the signal processing unit 110B. The signal processing unit 110B processes the wavelength λ output from the receiving unit 140B-2. ｂ Based on the optical signal and the frequency spectrum data of BtB stored in a memory not shown, wavelength λ ｂ The notch frequency at which the notch appears is calculated, except at frequency multiples of the optical signal.

[0054] Specifically, the signal processing unit 110B receives the wavelength λ ｂ A second frequency spectrum is created from the optical signal. Next, the signal processing unit 110B obtains an estimated frequency spectrum by dividing the created second frequency spectrum by the frequency spectrum data of BtB stored in memory (not shown) (since the spectral intensity is expressed in dB, the difference is taken in dB). Then, based on the obtained estimated frequency spectrum, the signal processing unit 110B calculates the wavelength λ ｂ The notch frequency f is the frequency at which a notch appears outside of the frequency multiples of the optical signal. ｍ,ｂ The notch frequency f is calculated (step S109). Note that m is a non-negative integer. ｍ,ａThis refers to the wavelength λ ｂ In the frequency spectrum of an optical signal, this refers to the (m+1)th notch frequency from the low-frequency side.

[0055] Furthermore, the signal processing unit 110B will find a local maximum if the method of calculating the difference between the frequency spectrum data of BtB and the spectrum after fiber transmission is reversed (for example, frequency spectrum data of BtB - spectrum after fiber transmission). In the following explanation, it is assumed that the notch frequency is obtained using the local minimum (spectrum after transmission - frequency spectrum data of BtB).

[0056] Next, the signal processing unit 110B calculates multiple notch frequencies f ｎ,ａ , f ｍ,ｂ And, the multiple chirp values ​​α that were determined in advance a , α b Using and based on equation (1), multiple wavelengths λ ０ Calculate (step S110). Multiple wavelengths λ ０ This is a wavelength that is a candidate for the zero-dispersion wavelength. Therefore, the multiple wavelengths λ calculated ０ any of the wavelengths λ ０ This is the zero-dispersion wavelength.

[0057] Chirp's Vα a The wavelength of the light signal is wavelength λ ａ The chirp value in this case is assumed to be pre-calculated. The chirp value α ｂ The wavelength of the light signal is wavelength λ ｂ The chirp value in this case is assumed to be calculated in advance. Between communication device 100A and communication device 100B, the wavelength λ ０ The different wavelengths used when calculating are assumed to be predetermined. Here, in equation (1), λ ａ and λ ｂ This represents the wavelength of the transmission signal sent by the communication device 100A.

[0058]

[0059] In equation (1), "A" and "B" can be any of the patterns shown in equations (2) to (5) below. Therefore, the signal processing unit 110B considers the wavelength λ when "A" and "B" in equation (1) are any of the patterns shown in equations (2) to (5). ０ This will result in the calculation of the four wavelengths λ. ０ Calculate.

[0060] Here, the wavelength λ is calculated using "A" and "B" shown in equation (2). ０ Wavelength λ of Pattern 1 ０ The wavelength λ was calculated using "A" and "B" shown in equation (3). ０ Wavelength λ of pattern 2 ０ The wavelength λ was calculated using "A" and "B" shown in equation (4). ０ Wavelength λ of pattern 3 ０ The wavelength λ was calculated using "A" and "B" shown in equation (5). ０ Wavelength λ of pattern 4 ０ Let's assume that.

[0061]

[0062]

[0063]

[0064]

[0065] Subsequently, the signal processing unit 110B calculates the wavelength λ of each pattern. ０ However, it is determined whether the conditions in each of equations (2) to (5) are met (step S111). Specifically, the signal processing unit 110B determines the wavelength λ of pattern 1. ０ However, the condition in equation (2) is the wavelength λ ａ and wavelength λ ｂ Smaller than, and S ０ L is greater than 0 (for example, (λ) ０ <λ ａ and λ ０ <λ ｂ and 0 < S ０ Determine whether the condition L) is met.

[0066] Similarly, the signal processing unit 110B determines whether the wavelength λ of pattern 2 ０ satisfies the condition of being larger than the wavelengths λ ａ and λ ｂ specified as conditions in formula (3), and that S ０ L is greater than 0 (for example, (λ ａ <λ ０ and λ ｂ <λ ０ and 0<S ０ L)).

[0067] Similarly, the signal processing unit 110B determines whether the wavelength λ of pattern 3 ０ satisfies the condition of being smaller than the wavelength λ ａ specified as a condition in formula (4), larger than the wavelength λ ｂ specified as a condition in formula (4), and that S ０ L is greater than 0 (for example, (λ ａ >λ ０ and λ ｂ <λ ０ and 0<S ０ L)).

[0068] Similarly, the signal processing unit 110B determines whether the wavelength λ of pattern 4 ０ satisfies the condition of being larger than the wavelength λ ａ specified as a condition in formula (5), smaller than the wavelength λ ｂ specified as a condition in formula (5), and that S ０ L is greater than 0 (for example, (λ ａ <λ ０ and λ ｂ >λ ０ and 0<S ０ L)).

[0069] Here, the above S ０ is a dispersion slope, which may be, for example, a value specified in a standardization (0.092 [ps / km / nm ２ for a single-mode fiber), or calculation may be performed using a value of S ０ ×L obtainable by an existing estimation method. Note that L is the distance between the communication device 100A and the communication device 100B. S ０L is calculated based on the following formula (6). Note that in systems where the upper limit of distance L is fixed, the fixed upper limit L is used. ｍａｘ Use [km] ０ L < 0.092L ｍａｘ The condition (i.e., 0 < S) ０ L < 0.092L ｍａｘ ) is added to equations (2) through (5). For example, if the distance is less than 100 km, S ０ The condition L < 9.2 is added to equations (2) through (5). For example, the upper limit of distance L can be determined based on the requirements of the transceiver used and the maximum transmission distance expected in the network configuration. Note that this is just one example, and the upper limit of distance L may be determined by other methods.

[0070]

[0071] The signal processing unit 110B calculates the wavelength λ of each pattern. ０ If the value does not satisfy the conditions of equations (2) to (5) corresponding to each pattern (i.e., it is outside the range of equations (2) to (5)), or if it is outside the range of the zero-dispersion wavelength of the optical fiber being used, the calculated wavelength λ ０ The value of is excluded. Here, we will explain in detail the cases where the conditions of equations (2) to (5) corresponding to each pattern are not met. As described above, the signal processing unit 110B receives the wavelength λ obtained for each pattern. ０ However, it determines whether the conditions in each of equations (2) through (5) are met.

[0072] The signal processing unit 110B processes the wavelength λ of pattern 1. ０ However, if the conditions in equation (2) are met, the wavelength λ of pattern 1 ０ This is retained as a candidate for the zero-dispersion wavelength. Meanwhile, the signal processing unit 110B considers the wavelength λ of pattern 1. ０ However, if the conditions in equation (2) are not met, the wavelength λ of pattern 1 ０ This is excluded from the list of zero-dispersion wavelength candidates. In this way, the signal processing unit 110B uses "A" and "B" shown in equation (2) to calculate the wavelength λ based on equation (1). ０For this, we determine whether the conditions in equation (2) are met (conditions in other equations are irrelevant) to determine whether or not to exclude candidates for zero-dispersion wavelengths.

[0073] Similarly, the signal processing unit 110B processes the wavelength λ of pattern 2. ０ However, if the conditions in equation (3) are met, the wavelength λ of pattern 2 ０ This is retained as a candidate for the zero-dispersion wavelength. Meanwhile, the signal processing unit 110B considers the wavelength λ of pattern 2. ０ However, if the conditions in equation (3) are not met, the wavelength λ of pattern 2 ０ This is excluded from the list of zero-dispersion wavelength candidates. In this way, the signal processing unit 110B uses "A" and "B" shown in equation (3) to calculate the wavelength λ based on equation (1). ０ For this, we determine whether the conditions in equation (3) are met (the conditions in other equations are irrelevant) to determine whether or not it is necessary to exclude candidates for zero-dispersion wavelengths.

[0074] Similarly, the signal processing unit 110B processes the wavelength λ of pattern 3. ０ However, if the conditions in equation (4) are met, the wavelength λ of pattern 3 ０ This is retained as a candidate for the zero-dispersion wavelength. Meanwhile, the signal processing unit 110B considers the wavelength λ of pattern 3. ０ However, if the conditions in equation (4) are not met, the wavelength λ of pattern 3 ０ This is excluded from the list of zero-dispersion wavelength candidates. In this way, the signal processing unit 110B uses "A" and "B" shown in equation (4) to calculate the wavelength λ based on equation (1). ０ For this, we determine whether the conditions in equation (4) are met (the conditions in other equations are irrelevant) to determine whether or not to exclude the candidate for zero-dispersion wavelength.

[0075] Similarly, the signal processing unit 110B processes the wavelength λ of pattern 4. ０ However, if the conditions in equation (5) are met, the wavelength λ of pattern 4 ０ This is retained as a candidate for the zero-dispersion wavelength. Meanwhile, the signal processing unit 110B considers the wavelength λ of pattern 4. ０ However, if the conditions in equation (5) are not met, the wavelength λ of pattern 4 ０This is excluded from the list of zero-dispersion wavelength candidates. In this way, the signal processing unit 110B uses "A" and "B" shown in equation (5) to calculate the wavelength λ based on equation (1). ０ For this, we determine whether the conditions in equation (5) are met (the conditions in other equations are irrelevant) to determine whether or not to exclude the candidate for zero-dispersion wavelength.

[0076] As described above, the signal processing unit 110B processes multiple wavelengths λ calculated for each pattern. ０ Among them, wavelength λ that does not satisfy the conditions for the corresponding pattern ０ The wavelength λ is excluded from the list of zero-dispersion wavelength candidates. Also, if the optical fiber being used is a standard single-mode fiber, the signal processing unit 110B will use the wavelength λ ０ If the value falls outside the wavelength range of 1300 to 1324 nm, it will be excluded.

[0077] Then, the signal processing unit 110B checks the wavelength λ that satisfies the conditions. ０ And, the speed of light c and the wavelength λ ａ And, wavelength λ ｂ Based on this, the wavelength range including the upper and lower limits of the wavelength dispersion (= wavelength dispersion D × distance L) is calculated by solving for λ using the following equations (7) and (8) (step S112). In equations (7) and (8), "A" and "B" are the wavelength λ that satisfies the conditions. ０ It is one of the values ​​from equations (2) to (5) that correspond to it. For example, the wavelength λ that satisfies the conditions. ０ However, if the values ​​are calculated using the values ​​of "A" and "B" shown in equation (2), then "A" and "B" in equations (7) and (8) are the values ​​of "A" and "B" shown in equation (2).

[0078]

[0079]

[0080] The signal processing unit 110B determines the wavelength λ used for downlink communication within the wavelength range determined based on equations (7) and (8) described above. ＤＳ Determine the wavelength (step S113). ＤＳThis is the wavelength used for transmission from communication device 100A to communication device 100B, when communication device 100A is viewed as a downstream device. In this case, communication device 100B transmits information indicating the wavelength range determined based on the above-described equations (7) and (8) to communication device 100A as information regarding the transmission wavelength (step S114).

[0081] In the signal processing unit 110B, wavelength λ ＤＳ When determining this, the value closest to the center of the wavelength corresponding to the wavelength within the wavelength range (the range between the upper and lower limits of the allowable amount of wavelength dispersion) is the wavelength λ. ＤＳ This could be the decision. Doing so would minimize penalties and enable even longer-distance transmission.

[0082] As a method for transmitting information regarding the transmission wavelength to a counterpart communication device 100 (for example, communication device 100A), a low-speed control signal can be used. Furthermore, by applying processing such as an equalizer at the signal processing stage, information can be acquired with a relatively high-speed signal. Additionally, for paths where the zero-dispersion wavelength value is known in advance, communication device 100B can set the transmission wavelength to a value near that value, thereby enabling notification with a high-speed signal.

[0083] In step S103, the connection path of the optical distribution unit 150B is set to connect the transmitting unit 130B and the upstream optical transmission path. As a result, the optical signal containing information about the transmission wavelength transmitted from the transmitting unit 130B reaches the communication device 100A via the upstream optical transmission path.

[0084] The receiving unit 140A-2 of the communication device 100A receives information regarding the transmission wavelength transmitted from the communication device 100B. The receiving unit 140A-2 outputs the received information regarding the transmission wavelength to the signal processing unit 110A. The signal processing unit 110A refers to the correspondence information and identifies the wavelength λ specified by the information regarding the transmission wavelength output from the receiving unit 140A-2. ＤＳ The signal processing unit 110A acquires the corresponding temperature information. The signal processing unit 110A sets the temperature controller 120A to the temperature indicated by the acquired temperature information (step S115). As a result, the signal processing unit 110A sets the transmission wavelength to wavelength λ.ＤＳ Change it.

[0085] Subsequently, the same processing as in steps S101 to S115 is performed in the uplink direction (step S116). In this case, communication device 100B performs the processing in steps S104, S107 and S115. Communication device 100A performs the processing in steps S101 to S103, S105, S106 and S108 to S114. As a result, the signal processing unit 110A determines the wavelength λ used for uplink communication within the wavelength range determined based on the above-described equations (7) and (8). ｕＳ Determine the wavelength λ. ＵＳ This is the wavelength used for transmission from communication device 100B to communication device 100A, when communication device 100B is viewed as upstream. In this case, communication device 100A transmits information indicating the wavelength range determined based on the above-described equations (7) and (8) to communication device 100B as information regarding the transmission wavelength.

[0086] In the signal processing unit 110A, wavelength λ ｕＳ When determining this, the value closest to the center of the wavelength corresponding to the wavelength within the wavelength range (the range between the upper and lower limits of the allowable amount of wavelength dispersion) is the wavelength λ. ｕＳ This could be the decision. Doing so would minimize penalties and enable even longer-distance transmission.

[0087] As a method for transmitting information regarding the transmission wavelength to the opposing communication device 100 (for example, communication device 100B), a low-speed control signal can be used. Furthermore, by applying processing such as an equalizer at the signal processing stage, information can be acquired with a relatively high-speed signal. Additionally, for paths where the zero-dispersion wavelength value is known in advance, communication device 100A can set the transmission wavelength to a value near that value, thereby enabling notification with a high-speed signal.

[0088] The receiving unit 140B-2 of the communication device 100B receives information regarding the transmission wavelength transmitted from the communication device 100A. The receiving unit 140B-2 outputs the received information regarding the transmission wavelength to the signal processing unit 110B. The signal processing unit 110B refers to the correspondence information and identifies the wavelength λ specified by the information regarding the transmission wavelength output from the receiving unit 140B-2. ｕＳ The signal processing unit 110B acquires the corresponding temperature information. The signal processing unit 110B sets the temperature controller 120B to the temperature indicated by the acquired temperature information. As a result, the signal processing unit 110B sets the transmission wavelength to wavelength λ. ｕＳ This is changed to allow the transmission wavelength to be set in both communication device 100A and communication device 100B. As a result, communication is initiated between communication device 100A and communication device 100B (step S116).

[0089] Furthermore, if the communication device 100B notifies information indicating a wavelength range as information regarding the transmission wavelength, the signal processing unit 110A of the communication device 100A will select the wavelength λ from the range between the upper and lower limits of the permissible value of the chromatic dispersion amount specified by the information indicating the wavelength range. ＤＳ The signal processing unit 110A determines a value close to the center value of the wavelength corresponding to the wavelength λ. ＤＳ It may also be determined as follows. Furthermore, the signal processing unit 110A maintains a list of penalty values ​​due to chromatic dispersion for each chromatic dispersion amount, finds the wavelength value corresponding to the chromatic dispersion amount for which the penalty value is minimized, and sets the value near the found wavelength λ ＤＳ It may be decided as such.

[0090] Furthermore, if the communication device 100A notifies information indicating a wavelength range as information regarding the transmission wavelength, the signal processing unit 110B of the communication device 100B will select the wavelength λ from the range between the upper and lower limits of the permissible value of the chromatic dispersion amount specified by the information indicating the wavelength range. ｕＳ The signal processing unit 110B determines a value close to the center value of the wavelength corresponding to the wavelength λ. ｕＳIt may also be determined as follows. Furthermore, the signal processing unit 110B maintains a list of penalty values ​​due to wavelength dispersion for each wavelength dispersion amount, finds the wavelength value corresponding to the wavelength dispersion amount for which the penalty value is minimized, and sets the value near the found wavelength λ ｕＳ It may be decided as such.

[0091] In Figure 2, the process of acquiring the frequency spectrum data of BtB may be performed before the calculation of the notch frequency (for example, in steps S106 or S109). Therefore, the process of acquiring the frequency spectrum data of BtB may be performed after the communication device 100B has processed receiving optical signals of different wavelengths transmitted from the communication device 100A. Furthermore, the process of calculating the notch frequency (for example, in steps S106 or S109) may be performed after the process of acquiring the frequency spectrum data of BtB has been performed.

[0092] The above process was explained using the example of estimating the zero-dispersion wavelength in communication device 100B. However, when estimating the zero-dispersion wavelength in communication device 100A, one should simply replace communication device 100A with communication device 100B and communication device 100B with communication device 100A in Figure 2. This allows communication device 100A to also acquire frequency spectrum data of BtB.

[0093] (Other Configurations) Here, other configurations of communication devices 100A and 100B will be described. Figure 3 is a diagram showing other configuration examples of the optical communication system 10 in the first embodiment. The communication device 100A shown in Figure 3 comprises a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a receiving unit 140A, and an optical distribution unit 150A. The communication device 100B shown in Figure 3 comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a receiving unit 140B, and an optical distribution unit 150B. Since communication devices 100A and 100B have the same configuration, the explanation will use communication device 100A as an example.

[0094] The optical distribution unit 150A shown in Figure 3 has M (where M is an integer of 2 or more) first ports and N (where N is an integer of 2 or more) second ports. The optical distribution unit 150A may be, for example, an M x N optical switch. When the optical distribution unit 150A is a 2 x 2 optical switch, each of the first ports of the optical distribution unit 150A is connected to the transmitting unit 130A and the receiving unit 140A, and each of the second ports of the optical distribution unit 150A is connected to the downstream optical transmission path and the upstream optical transmission path. With this configuration, the receiving unit 140A can be reduced to one unit.

[0095] [Operation of Optical Communication System 10] Next, the processing flow in the optical communication system 10 shown in Figure 3 will be explained. The basic processing flow is the same as the processing shown in Figure 2. The following explanation will focus on the differences from the processing shown in Figure 2. For example, in the optical communication system 10 shown in Figure 3, the following processing is performed instead of steps S101 to S103.

[0096] The optical distribution unit 150B (for example, a 2x2 optical switch) of the communication device 100B sets a connection path to connect the transmitting unit 130B and the receiving unit 140B according to the control of a control unit (not shown). As a result, the optical signal transmitted from the transmitting unit 130B is input to the receiving unit 140B via the optical distribution unit 150B. In other words, the optical signal transmitted from the transmitting unit 130B is not output to the upstream optical transmission path.

[0097] The transmitting unit 130B of the communication device 100B transmits an optical signal of an arbitrary wavelength λ. The optical signal of wavelength λ transmitted from the transmitting unit 130B is input to the first port of the optical distribution unit 150B. The optical distribution unit 150B forwards the optical signal of wavelength λ input to the first port to which the receiving unit 140B-1 is connected. As a result, the optical distribution unit 150B outputs an optical signal of wavelength λ from the first port to which the receiving unit 140B is connected. The optical signal of wavelength λ output from the first port of the optical distribution unit 150B is then received by the receiving unit 140B.

[0098] The receiving unit 140B outputs the received optical signal with wavelength λ to the signal processing unit 110B. The signal processing unit 110B creates a frequency spectrum from the optical signal with wavelength λ output from the receiving unit 140B. As a result, the signal processing unit 110B obtains the frequency spectrum data of BtB. The signal processing unit 110B stores the obtained frequency spectrum data of BtB in a memory not shown.

[0099] Subsequently, the optical distribution unit 150B, in accordance with the control of a control unit (not shown), sets a connection path to connect the transmitting unit 130B to the upstream optical transmission path, and sets a connection path to connect the receiving unit 140B to the downstream optical transmission path. As a result, the optical signal transmitted from the transmitting unit 130B is input to the communication device 100A via the upstream optical transmission path, and the optical signal transmitted from the communication device 100A is input to the communication device 100B via the downstream optical transmission path. After that, the processing from step S104 onward is executed.

[0100] The process of acquiring the frequency spectrum data of BtB may be performed before the calculation of the notch frequency (for example, in steps S106 or S109). Therefore, the process of acquiring the frequency spectrum data of BtB may be performed after the communication device 100B has processed receiving optical signals of different wavelengths transmitted from the communication device 100A. Furthermore, the process of calculating the notch frequency (for example, in steps S106 or S109) may be performed after the process of acquiring the frequency spectrum data of BtB has been performed.

[0101] According to the optical communication system 10 in the first embodiment configured as described above, the communication devices 100A and 100B include: transmitting units 130A and 130B that transmit one or more optical signals of wavelengths; receiving units 140A and 140B that receive a plurality of optical signals of different wavelengths transmitted from a communication device of a communication partner connected via an optical transmission path, and a portion of the one or more optical signals of wavelengths transmitted from the transmitting units 130A and 130B; and signal processing units 110A and 110B that acquire frequency spectrum data of BtB based on a portion of the one or more optical signals of wavelengths transmitted from the transmitting units 130A and 130B, and estimate the zero-dispersion wavelength based on the acquired frequency spectrum data of BtB and the frequency spectra of each of the plurality of optical signals.

[0102] Thus, communication devices 100A and 100B can acquire BtB frequency spectrum data by receiving the optical signal they transmit within their own devices during operation. This eliminates the need to conduct experiments using different transceiver combinations to acquire BtB frequency spectrum data. Therefore, it becomes possible to suppress the increase in operational costs for estimating the zero-dispersion wavelength of optical fibers in optical communication using optical fibers.

[0103] Furthermore, the communication devices 100A and 100B are equipped with optical distribution units 150A and 150B, which output the optical signal of wavelength λ transmitted from the transmitting units 130A and 130B toward the receiving units 140A and 140B. With this configuration, the communication devices 100A and 100B receive the optical signal of wavelength λ transmitted from the transmitting units 130A and 130B within their own devices. Therefore, it is possible to acquire BtB frequency spectrum data even while actual signal exchange is taking place with the communication device of the communication partner. This eliminates the need to conduct experiments using combinations of transceivers to acquire BtB frequency spectrum data. As a result, it becomes possible to suppress the increase in operational costs for estimating the zero-dispersion wavelength of optical fibers in optical communication using optical fibers.

[0104] (Modification of the first embodiment) The optical distribution units 150A and 150B may be provided outside the communication devices 100A and 100B.

[0105] (Second Embodiment) In the first embodiment, a configuration was described in which each communication device inputs the optical signal transmitted from the transmitting unit to its receiving unit by folding it back using an optical splitting unit in order to acquire BtB frequency spectrum data. In the second embodiment, other configurations for each communication device to acquire BtB frequency spectrum data will be described.

[0106] Figure 4 shows an example configuration of the optical communication system 20 in the second embodiment. The optical communication system 20 includes a communication device 200A and a communication device 200B. Communication devices 200A and 200B communicate via an optical transmission path. Communication devices 200A and 200B communicate using two-core transmission with two optical transmission paths.

[0107] In the following explanation, the direction from communication device 200A to communication device 200B will be referred to as the downstream direction, and the direction from communication device 200B to communication device 200A will be referred to as the upstream direction. Furthermore, the optical transmission path used by communication device 200A for downstream communication will be referred to as the downstream optical transmission path, and the optical transmission path used by communication device 200B for upstream communication will be referred to as the upstream optical transmission path.

[0108] Communication device 200A comprises a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a plurality of receiving units 140A-1 to 140A-2, and an optical splitter 155A. Communication device 200B comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a plurality of receiving units 140B-1 to 140B-2, and an optical splitter 155B. Since communication devices 200A and 200B have the same configuration, communication device 200A will be used as an example for explanation.

[0109] Communication device 200A differs from communication device 100A in that it includes an optical splitter 155A instead of an optical distribution unit 150A. Other configurations of communication device 200A are the same as those of communication device 100A. The following explanation will focus on the differences from communication device 100A.

[0110] The optical splitter 155A is located at the output destination of the transmitting unit 130A. The optical splitter 155A splits the input optical signal into a downstream optical transmission path and a receiving unit 140A-1. The optical splitter 155A is, for example, an optical coupler. When using an optical coupler, the splitting ratio does not have to be 1:1; any splitting ratio that results in a received power within the receiving sensitivity range of the receiving unit 140A-1 is acceptable. In this way, the optical splitter 155A is an optical component that outputs light so that the optical signal transmitted by its own device can be received by its own device.

[0111] The communication device 200A may be equipped with a circulator instead of the optical splitter 155A, and the input optical signal may be output to the downstream optical transmission path and the receiving unit 140A-1. Similarly, the communication device 200B may be equipped with a circulator instead of the optical splitter 155B.

[0112] [Operation of Optical Communication System 20] Next, the processing flow in the optical communication system 20 will be described. Figure 5 is a sequence diagram showing the processing flow in the optical communication system 20 of the second embodiment. The transmitting unit 130B of the communication device 200B transmits an optical signal of an arbitrary wavelength λ (step S201). The optical signal of wavelength λ transmitted from the transmitting unit 130B is input to the optical splitter 155B. The optical splitter 155B splits the input optical signal of wavelength λ at a predetermined splitting ratio and outputs it to the receiving unit 140B-1 and the upstream optical transmission path (step S202). As a result, the optical signal of wavelength λ output from the optical splitter 155B is received by the receiving unit 140B-1.

[0113] The optical signal of wavelength λ output from the optical splitter 155B is received by the receiving unit 140A-2 of the communication device 200A via the upstream optical transmission path. However, since no special processing is required for the optical signal of wavelength λ, the signal processing unit 110A may discard the optical signal of wavelength λ received by the receiving unit 140A-2.

[0114] The receiving unit 140B-1 outputs the received optical signal of wavelength λ to the signal processing unit 110B. The signal processing unit 110B creates a frequency spectrum from the optical signal of wavelength λ output from the receiving unit 140B-1. As a result, the signal processing unit 110B acquires the frequency spectrum data of BtB (step S203). The signal processing unit 110B stores the acquired frequency spectrum data of BtB in a memory not shown. After that, the processing from step S104 onwards is executed.

[0115] In step S104, the wavelength λ transmitted from the transmitting unit 130A of the communication device 100A ａ The optical signal is split by the optical splitter 155A and output to the downstream optical transmission path and to the receiving unit 140A-1. The wavelength λ output to the receiving unit 140A-1 ａ Since the optical signal does not require any special processing, the signal processing unit 110A processes the wavelength λ received by the receiving unit 140A-1. ａ The optical signal may be discarded. Alternatively, the signal processing unit 110A may receive the wavelength λ received by the receiving unit 140A-1. ａ The frequency spectrum data of BtB may be obtained based on the optical signal. The same applies to the process in step S107.

[0116] The process of acquiring the frequency spectrum data of BtB may be performed before the calculation of the notch frequency (for example, in steps S106 or S109). Therefore, the process of acquiring the frequency spectrum data of BtB may be performed after the communication device 200B has processed receiving optical signals of different wavelengths transmitted from the communication device 200A. Furthermore, the process of calculating the notch frequency (for example, in steps S106 or S109) may be performed after the process of acquiring the frequency spectrum data of BtB has been performed.

[0117] (Other Configurations) Here, other configurations of communication devices 200A and 200B will be described. Figure 6 is a diagram showing other configuration examples of the optical communication system 20 in the second embodiment. The communication device 200A shown in Figure 6 comprises a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a receiving unit 140A, an optical distribution unit 150A, and an optical splitter 155A. The communication device 200B shown in Figure 6 comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a receiving unit 140B, an optical distribution unit 150B, and an optical splitter 155B. Since communication devices 200A and 200B have the same configuration, the explanation will use communication device 200A as an example.

[0118] The optical distribution unit 150A shown in Figure 6 may be a 1xL optical switch, similar to the optical distribution unit 150A in Figure 1. The first port of the optical distribution unit 150A is connected to the receiving unit 140A, and each of the second ports of the optical distribution unit 150A is connected to the optical splitter 155A and the upstream optical transmission path. In this way, the optical signal branched by the optical splitter 155A may be received by the receiving unit 140A using an optical switch or the like. In this case, it can be achieved by managing the timing of receiving the optical signal transmitted from the communication device 200B at a certain time interval and switching the connection path of the optical distribution unit 150A.

[0119] For example, when the optical distribution unit 150A acquires frequency spectrum data of BtB, the connection path between ports is controlled to connect the optical splitter 155A and the receiving unit 140A. Then, when the optical distribution unit 150A communicates with the communication device 200B, the connection path between ports is controlled to connect the upstream optical transmission path and the receiving unit 140A. The control of the connection path of the optical distribution unit 150A is performed by a control unit (not shown).

[0120] [Operation of Optical Communication System 20] Next, the processing flow in the optical communication system 20 shown in Figure 6 will be explained. The basic processing flow is the same as the processing shown in Figure 5. The following explanation will focus on the differences from the processing shown in Figure 5. The optical distribution unit 150B (for example, a 1xL optical switch) provided in the communication device 200B sets a connection path to connect the optical splitter 155B and the receiving unit 140B according to the control of the control unit (not shown). As a result, the optical signal transmitted from the transmitting unit 130B is input to the receiving unit 140B via the optical splitter 155B and the optical distribution unit 150B.

[0121] The transmitting unit 130B of the communication device 200B transmits an optical signal of an arbitrary wavelength λ. The optical signal of wavelength λ transmitted from the transmitting unit 130B is input to the optical splitter 155B. The optical splitter 155B splits the input optical signal of wavelength λ at a predetermined splitting ratio and outputs it to the optical distribution unit 150B and the upstream optical transmission path. Through the above process, the optical distribution unit 150B sets a connection path to connect the optical splitter 155B and the receiving unit 140B. As a result, the optical signal of wavelength λ output from the optical splitter 155B is received by the receiving unit 140B via the optical distribution unit 150B.

[0122] The optical signal of wavelength λ output from the optical splitter 155B is received by the receiving unit 140A of the communication device 200A via the upstream optical transmission path and the optical distribution unit 150A. However, since no special processing is required for the optical signal of wavelength λ, the signal processing unit 110A may discard the optical signal of wavelength λ received by the receiving unit 140A.

[0123] The receiving unit 140B outputs the received optical signal with wavelength λ to the signal processing unit 110B. The signal processing unit 110B creates a frequency spectrum from the optical signal with wavelength λ output from the receiving unit 140B. As a result, the signal processing unit 110B obtains the frequency spectrum data of BtB. The signal processing unit 110B stores the obtained frequency spectrum data of BtB in a memory not shown.

[0124] The optical distribution unit 150B (for example, a 1xL optical switch) of the communication device 200B sets a connection path to connect the downstream optical transmission path and the receiving unit 140B, in accordance with the control of a control unit (not shown). As a result, the optical signal transmitted from the communication device 200A is input to the receiving unit 140B via the optical distribution unit 150B. Subsequently, the processing from step S104 onward is executed.

[0125] The process of acquiring the frequency spectrum data of BtB may be performed before the calculation of the notch frequency (for example, in steps S106 or S109). Therefore, the process of acquiring the frequency spectrum data of BtB may be performed after the communication device 200B has processed receiving optical signals of different wavelengths transmitted from the communication device 200A. Furthermore, the process of calculating the notch frequency (for example, in steps S106 or S109) may be performed after the process of acquiring the frequency spectrum data of BtB has been performed.

[0126] According to the optical communication system 20 in the second embodiment configured as described above, the communication devices 200A and 200B can obtain the same effects as in the first embodiment by including optical splitters 155A and 155B.

[0127] (Modification of the second embodiment) In the configuration shown in Figure 4, the optical splitters 155A and 155B may be provided outside the communication devices 200A and 200B. In the configuration shown in Figure 5, the optical distribution units 150A and 150B and the optical splitters 155A and 155B may be provided outside the communication devices 200A and 200B.

[0128] (Third Embodiment) In the third embodiment, a configuration is described in which each communication device is equipped with multiple lasers to acquire BtB frequency spectrum data.

[0129] Figure 7 shows an example configuration of the optical communication system 30 in the third embodiment. The optical communication system 30 comprises a communication device 300A and a communication device 300B. Communication devices 300A and 300B communicate via an optical transmission path. Communication devices 300A and 300B communicate using two-core transmission with two optical transmission paths.

[0130] In the following description, the direction from communication device 300A to communication device 300B will be referred to as the downstream direction, and the direction from communication device 300B to communication device 300A will be referred to as the upstream direction. Furthermore, the optical transmission path used by communication device 300A for downstream communication will be referred to as the downstream optical transmission path, and the optical transmission path used by communication device 300B for upstream communication will be referred to as the upstream optical transmission path.

[0131] The communication device 300A includes a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a receiving unit 140A, a wavelength filter 160A, and an optical distribution unit 165A. The transmitting unit 130A includes a plurality of lasers 131A-1 to 131A-2, an optical distribution unit 132A, a signal generation unit 133A, and an optical modulator 134A.

[0132] Although not shown in Figure 7, the communication device 300B has the same configuration as the communication device 300A. Specifically, the communication device 300B comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a receiving unit 140B, a wavelength filter 160B, and an optical distribution unit 165B. The transmitting unit 130B comprises a plurality of lasers 131B-1 to 131B-2, an optical distribution unit 132B, a signal generation unit 133B, and an optical modulator 134B. As the communication devices 300A and 300B have the same configuration, the explanation will use the communication device 300A as an example.

[0133] Lasers 131A-1 to 131A-2 output light of different wavelengths in response to the control of the temperature controller 120A. Laser 131A-1 is used for communication with the communication device 300B. Laser 131A-1 may output light of wavelengths in the O-band (wavelength band of 1260 nm to 1360 nm), for example, as the wavelength corresponding to the zero-dispersion wavelength of a standard single-mode fiber.

[0134] Laser 131A-2 is a laser used to acquire frequency spectrum data of BtB. Laser 131A-2 may output light with a wavelength in the C-band (wavelength band of 1530 nm to 1565 nm). Here, C-band is used as an example, but other wavelength bands may be used. For example, O-band, L-band, S-band, or E-band may be used. This is also true in other embodiments. Laser 131A-2 only needs to be able to output light with a specific wavelength in order to acquire frequency spectrum data of BtB. Therefore, laser 131A-2 may be a fixed-wavelength laser or a tunable-wavelength laser.

[0135] The optical distribution unit 132A is positioned at the output destination of each laser 131. The optical distribution unit 132A outputs the light output from any of the lasers 131 to the optical modulator 134A. The optical distribution unit 132A has L first ports and 1 second port. The optical distribution unit 132A may be, for example, a 1 × L optical switch. Each of the first ports of the optical distribution unit 132A is connected to lasers 131A-1 and 131A-2, and the second port of the optical distribution unit 132A is connected to the optical modulator 134A.

[0136] When the optical distribution unit 132A acquires frequency spectrum data of BtB, the connection path between ports is controlled to connect laser 131A-2 and optical modulator 134A. When the optical distribution unit 132A communicates with the communication device 300B, the connection path between ports is controlled to connect laser 131A-1 and optical modulator 134A. The control of the connection path of the optical distribution unit 132A is performed by a control unit (not shown).

[0137] The signal generation unit 133A generates the main signal. The optical modulator 134A is a modulator capable of modulating the main signal data generated by the signal generation unit 133A using the light from each laser 131A. As a result, the optical modulator 134A generates a modulated signal (optical signal) corresponding to the wavelength of the light output from the laser 131A.

[0138] The wavelength filter 160A is a filter capable of separating an input optical signal according to its wavelength. For example, the wavelength filter 160A outputs light of the wavelength output from laser 131A-1 to the downstream optical transmission path and outputs light of the wavelength output from laser 131A-2 to the optical distribution unit 165A. In this way, the wavelength filter 160A is an optical component that changes the direction of light output according to its wavelength so that the optical signal transmitted by the device can be received by the device.

[0139] The optical distribution unit 165A may be a 1×L optical switch, similar to the optical distribution unit 150A in Figure 1. The first port of the optical distribution unit 165A is connected to the receiving unit 140A, and each of the second ports of the optical distribution unit 165A is connected to the wavelength filter 160A and the upstream optical transmission path. In this way, an optical switch or the like may be used to allow the receiving unit 140A to receive light separated according to wavelength by the wavelength filter 160A. In this case, it can be achieved by managing the timing of receiving the optical signal transmitted from the communication device 200B at a certain time interval and switching the connection path of the optical distribution unit 165A.

[0140] For example, when the optical distribution unit 165A acquires frequency spectrum data of BtB, the connection path between ports is controlled to connect the wavelength filter 160A and the receiving unit 140A. When the optical distribution unit 165A communicates with the communication device 300B, the connection path between ports is controlled to connect the upstream optical transmission path and the receiving unit 140A. The control of the connection path of the optical distribution unit 165A is performed by a control unit (not shown).

[0141] [Operation of Optical Communication System 30] Next, the processing flow in the optical communication system 30 will be described. Figure 8 is a sequence diagram showing the processing flow in the optical communication system 30 of the third embodiment. The optical distribution unit 132B of the communication device 300B sets a connection path to connect the laser 131B-2 and the optical modulator 134B according to the control of a control unit (not shown). Furthermore, the optical distribution unit 165B of the communication device 300B sets a connection path to connect the wavelength filter 160B and the receiving unit 140B according to the control of a control unit (not shown) (step S301). As a result, the optical signal based on the light output from the laser 131B-2 is input to the receiving unit 140B via the wavelength filter 160B and the optical distribution unit 165B. In other words, the optical signal based on the light output from the laser 131B-2 is not output to the upstream optical transmission path.

[0142] Laser 131B-2 outputs light of any wavelength λ (for example, any wavelength in the C-band). The light of any wavelength λ output from laser 131B-2 is input to optical modulator 134B via optical distribution unit 132A. Optical modulator 134B modulates the input light of any wavelength λ based on the main signal output from signal generation unit 133B. As a result, optical modulator 134B generates an optical signal (modulated signal) of any wavelength λ. Optical modulator 134B transmits the generated optical signal of any wavelength λ (step S302).

[0143] An optical signal of any wavelength λ transmitted from the optical modulator 134B is separated according to wavelength by the wavelength filter 160B. The wavelength filter 160B outputs the input optical signal of any wavelength λ to the optical distribution unit 165B. In step S301, the optical distribution unit 165B sets a connection path to connect the wavelength filter 160B and the receiving unit 140B. As a result, the optical signal of wavelength λ output from the wavelength filter 160B is received by the receiving unit 140B via the optical distribution unit 165B.

[0144] The receiving unit 140B outputs the received optical signal of wavelength λ to the signal processing unit 110B. The signal processing unit 110B creates a frequency spectrum from the optical signal of wavelength λ output from the receiving unit 140B. As a result, the signal processing unit 110B acquires the frequency spectrum data of BtB (step S304). The signal processing unit 110B stores the acquired frequency spectrum data of BtB in a memory not shown.

[0145] The optical distribution unit 132B of the communication device 300B sets a connection path to connect the laser 131B-1 and the optical modulator 134B in accordance with the control of a control unit (not shown). Furthermore, the optical distribution unit 165B of the communication device 300B sets a connection path to connect the wavelength filter 160B and the downstream optical transmission path in accordance with the control of a control unit (not shown) (step S305). As a result, the light output from the laser 131B-1 is input to the optical modulator 134B, and the optical signal transmitted from the communication device 300A is input to the receiving unit 140B via the optical distribution unit 165B. After that, the processing from step S104 onwards is executed.

[0146] (Other Configuration 1) Here, three other configurations of the communication device 300A and the communication device 300B will be described using Figures 9 to 11. Figure 9 is a diagram showing another example of the configuration (1) of the optical communication system 30 in the third embodiment. The communication device 300A shown in Figure 9 includes a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a plurality of receiving units 140A-1 to 140A-2, and a wavelength filter 160A. The transmitting unit 130A includes a plurality of lasers 131A-1 to 131A-2, an optical distribution unit 132A, a signal generation unit 133A, and an optical modulator 134A.

[0147] Although not shown in Figure 9, the communication device 300B has the same configuration as the communication device 300A. Specifically, the communication device 300B comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a plurality of receiving units 140B-1 to 140B-2, and a wavelength filter 160B. The transmitting unit 130B comprises a plurality of lasers 131B-1 to 131B-2, an optical distribution unit 132B, a signal generation unit 133B, and an optical modulator 134B. As the communication devices 300A and 300B shown in Figure 9 have the same configuration, the explanation will use the communication device 300A as an example.

[0148] The wavelength filter 160A shown in Figure 9 outputs, for example, light of the wavelength output from laser 131A-1 to the downstream optical transmission path, and light of the wavelength output from laser 131A-2 to the receiving unit 140A-1.

[0149] The receiving unit 140A-1 receives the optical signal transmitted by the transmitting unit 130A of its own device. The receiving unit 140A-1 also receives the optical signal output by, for example, the wavelength filter 160A. The receiving unit 140A-2 receives the optical signal transmitted from the communication device 300B. In this way, the communication device 300A is equipped with multiple receiving units 140A in order to receive not only optical signals transmitted by other communication devices but also optical signals transmitted by its own device.

[0150] [Operation of Optical Communication System 30] Next, the processing flow in the optical communication system 30 shown in Figure 9 will be explained. The basic processing flow is the same as the processing shown in Figure 8. The following explanation will focus on the differences from the processing shown in Figure 8. The optical distribution unit 132B of the communication device 300B sets a connection path to connect the laser 131B-2 and the optical modulator 134B according to the control of the control unit (not shown). As a result, the optical signal based on the wavelength of light output from the laser 131B-2 is input to the receiving unit 140B-1 via the wavelength filter 160B. In other words, the optical signal based on the wavelength of light output from the laser 131B-2 is not output to the upstream optical transmission path.

[0151] Laser 131B-2 outputs light of any wavelength λ (for example, any wavelength in the C-band). The light of any wavelength λ output from laser 131B-2 is input to optical modulator 134B via optical distribution unit 132A. Optical modulator 134B modulates the input light of any wavelength λ based on the main signal output from signal generation unit 133B. As a result, optical modulator 134B generates an optical signal (modulated signal) of any wavelength λ. Optical modulator 134B transmits the generated optical signal of any wavelength λ.

[0152] An optical signal of any wavelength λ transmitted from the optical modulator 134B is separated according to wavelength by the wavelength filter 160B. The wavelength filter 160B outputs the input optical signal of any wavelength λ to the receiving unit 140B-1. As a result, the optical signal of wavelength λ output from the wavelength filter 160B is received by the receiving unit 140B-1.

[0153] The receiving unit 140B-1 outputs the received optical signal of wavelength λ to the signal processing unit 110B. The signal processing unit 110B creates a frequency spectrum from the optical signal of wavelength λ output from the receiving unit 140B-1. As a result, the signal processing unit 110B obtains the frequency spectrum data of BtB. The signal processing unit 110B stores the obtained frequency spectrum data of BtB in a memory not shown.

[0154] The optical distribution unit 132B of the communication device 300B sets a connection path to connect the laser 131B-1 and the optical modulator 134B in accordance with the control of a control unit (not shown) (step S352). As a result, the light output from the laser 131B-1 is input to the optical modulator 134B. After that, the processing from step S104 onwards is executed.

[0155] (Other Configuration 2) Figure 10 shows another configuration example (part 2) of the optical communication system 30 in the third embodiment. The communication device 300A shown in Figure 10 includes a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a receiving unit 140A, and an optical distribution unit 165A. The transmitting unit 130A includes a plurality of lasers 131A-1 to 131A-2, a signal generation unit 133A, and a plurality of optical modulators 134A-1 to 134A-2.

[0156] Although not shown in Figure 10, the communication device 300B has the same configuration as the communication device 300A. Specifically, the communication device 300B comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a receiving unit 140B, and an optical distribution unit 165B. The transmitting unit 130B comprises a plurality of lasers 131B-1 to 131B-2, a signal generation unit 133B, and a plurality of optical modulators 134B-1 to 134B-2. As the communication devices 300A and 300B shown in Figure 10 have the same configuration, the explanation will use the communication device 300A as an example.

[0157] The signal generation unit 133A shown in Figure 10 generates the main signal. The signal generation unit 133A outputs the generated main signal to optical modulators 134A-1 and 134A-2. In Figure 10, there is only one signal generation unit 133A, but a signal generation unit 133A may be provided for each optical modulator 134A.

[0158] Optical modulator 134A-1 is a modulator capable of modulating the main signal generated by the signal generation unit 133A using the light from laser 131A-1. Optical modulator 134A-2 is a modulator capable of modulating the main signal generated by the signal generation unit 133A using the light from laser 131A-2. Optical modulators 134A-1 and 134A-2 may be modulators having the same bandwidth.

[0159] The optical distribution unit 165A may be a 1×L optical switch, similar to the optical distribution unit 150A in Figure 1. The first port of the optical distribution unit 165A is connected to the receiving unit 140A, and each of the second ports of the optical distribution unit 165A is connected to the optical modulator 134A-2 and the upstream optical transmission path. In this way, an optical switch or the like may be used to allow the receiving unit 140A to receive the optical signal of wavelength λ generated by the optical modulator 134A-2.

[0160] For example, when the optical distribution unit 165A acquires frequency spectrum data of BtB, the connection path between ports is controlled to connect the optical modulator 134A-2 and the receiving unit 140A. When the optical distribution unit 165A communicates with the communication device 300B, the connection path between ports is controlled to connect the upstream optical transmission path and the receiving unit 140A. The control of the connection path of the optical distribution unit 165A is performed by a control unit (not shown).

[0161] [Operation of Optical Communication System 30] Next, the processing flow in the optical communication system 30 shown in Figure 10 will be explained. The basic processing flow is the same as the processing shown in Figure 8. The following explanation will focus on the differences from the processing shown in Figure 8. The optical distribution unit 165B of the communication device 300B sets a connection path to connect the optical modulator 134B-2 and the receiving unit 140B in accordance with the control of the control unit (not shown). As a result, the optical signal transmitted from the optical modulator 134B-2 is input to the receiving unit 140B via the optical distribution unit 165B.

[0162] Laser 131B-2 outputs light of any wavelength λ (for example, any wavelength in the C-band). The light of any wavelength λ output from laser 131B-2 is input to optical modulator 134B-2. Optical modulator 134B-2 modulates the input light of any wavelength λ based on the signal output from signal generation unit 133B. As a result, optical modulator 134B-2 generates an optical signal (modulated signal) of any wavelength λ. Optical modulator 134B-2 transmits the generated optical signal of any wavelength λ.

[0163] An optical signal of any wavelength λ transmitted from the optical modulator 134B-2 is input to the optical distribution unit 165B. Through the above process, the optical distribution unit 165B sets a connection path to connect the optical modulator 134B-2 and the receiving unit 140B. As a result, the optical signal of wavelength λ output from the optical modulator 134B-2 is received by the receiving unit 140B via the optical distribution unit 165B.

[0164] The receiving unit 140B outputs the received optical signal with wavelength λ to the signal processing unit 110B. The signal processing unit 110B creates a frequency spectrum from the optical signal with wavelength λ output from the receiving unit 140B. As a result, the signal processing unit 110B obtains the frequency spectrum data of BtB. The signal processing unit 110B stores the obtained frequency spectrum data of BtB in a memory not shown.

[0165] The optical distribution unit 165B of the communication device 300B sets a connection path to connect the wavelength filter 160B and the downstream optical transmission path, in accordance with the control of a control unit (not shown). As a result, the optical signal transmitted from the communication device 300A is input to the receiving unit 140B via the optical distribution unit 165B. Subsequently, the processing from step S104 onward is executed.

[0166] (Other Configuration 3) Figure 11 shows another configuration example (number 3) of the optical communication system 30 in the third embodiment. The communication device 300A shown in Figure 11 comprises a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, and a plurality of receiving units 140A-1 to 140A-2. The transmitting unit 130A comprises a plurality of lasers 131A-1 to 131A-2, a signal generation unit 133A, and a plurality of optical modulators 134A-1 to 134A-2.

[0167] Although not shown in Figure 11, the communication device 300B has the same configuration as the communication device 300A. Specifically, the communication device 300B comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, and a plurality of receiving units 140B-1 to 140B-2. The transmitting unit 130B comprises a plurality of lasers 131B-1 to 131B-2, a signal generating unit 133B, and a plurality of optical modulators 134B-1 to 134B-2. As the communication devices 300A and 300B shown in Figure 11 have the same configuration, the explanation will use the communication device 300A as an example.

[0168] The receiving unit 140A-1 receives the optical signal transmitted by the transmitting unit 130A of its own device. The receiving unit 140A-1 also receives the optical signal output by, for example, the optical modulator 134A-2. The receiving unit 140A-2 receives the optical signal transmitted from the communication device 300B. In this way, the communication device 300A is equipped with multiple receiving units 140A in order to receive not only optical signals transmitted by other communication devices but also optical signals transmitted by its own device.

[0169] [Operation of Optical Communication System 30] Next, the processing flow in the optical communication system 30 shown in Figure 11 will be explained. The basic processing flow is the same as the processing shown in Figure 8. The following explanation will focus on the differences from the processing shown in Figure 8. The laser 131B-2 provided in the communication device 300B outputs light of an arbitrary wavelength λ. The light of an arbitrary wavelength λ output from the laser 131B-2 is input to the optical modulator 134B-2. The optical modulator 134B-2 modulates the input light of an arbitrary wavelength λ based on the signal output from the signal generation unit 133B. As a result, the optical modulator 134B-2 generates an optical signal (modulated signal) of an arbitrary wavelength λ. The optical modulator 134B-2 transmits the generated optical signal of an arbitrary wavelength λ.

[0170] An optical signal of an arbitrary wavelength λ transmitted from the optical modulator 134B-2 is received by the receiver 140B-1. The receiver 140B-1 outputs the received optical signal of wavelength λ to the signal processing unit 110B. The signal processing unit 110B creates a frequency spectrum from the optical signal of wavelength λ output from the receiver 140B-1. As a result, the signal processing unit 110B obtains frequency spectrum data of BtB. The signal processing unit 110B stores the obtained frequency spectrum data of BtB in a memory not shown.

[0171] The optical distribution unit 132B of the communication device 300B sets a connection path to connect the laser 131B-1 and the optical modulator 134B in accordance with the control of a control unit (not shown). Subsequently, the processing from step S104 onward is executed.

[0172] According to the optical communication system 30 in the third embodiment configured as described above, even when the communication devices 300A and 300B are equipped with multiple lasers as transmitting units 130A and 130B, the same effects as in the first embodiment can be obtained.

[0173] (Modification 1 of the third embodiment) In the configuration shown in Figure 7, the communication devices 300A and 300B may be equipped with optical couplers or circulators instead of optical distribution units 132A and 132B. Furthermore, in the configuration shown in Figure 7, the communication devices 300A and 300B may be equipped with optical couplers or circulators instead of optical distribution units 165A and 165B.

[0174] (Modification 2 of the third embodiment) In the configuration shown in Figure 9, the communication devices 300A and 300B may be equipped with optical couplers or circulators instead of optical distribution units 132A and 132B. In this case, the acquisition of the frequency spectrum data of BtB may be performed at the same timing as the acquisition of data after transmission.

[0175] (Modification 3 of the third embodiment) In the configuration shown in Figure 10, the communication devices 300A and 300B may be equipped with optical couplers or circulators instead of optical distribution units 165A and 165B.

[0176] (Modification 4 of the third embodiment) The process of acquiring the frequency spectrum data of BtB may be performed before the calculation of the notch frequency (for example, in step S106 or step S109). Therefore, the process of acquiring the frequency spectrum data of BtB may be performed after the communication device 100B has processed receiving optical signals of different wavelengths transmitted from the communication device 100A. Then, the process of calculating the notch frequency (for example, in step S106 or step S109) may be performed after the process of acquiring the frequency spectrum data of BtB has been performed.

[0177] (Fourth Embodiment) The first to third embodiments described the case where two optical fibers connect the communication devices. The fourth embodiment describes the case where one optical fiber connects the communication devices.

[0178] Figure 12 shows an example of the configuration of the optical communication system 40 in the fourth embodiment. The optical communication system 40 comprises a communication device 400A and a communication device 400B. Communication devices 400A and 400B communicate via an optical transmission path. Communication devices 400A and 400B communicate by single-core bidirectional transmission using a single optical transmission path. In the following description, the direction from communication device 400A to communication device 400B is referred to as the downstream direction, and the direction from communication device 400B to communication device 400A is referred to as the upstream direction.

[0179] Communication device 400A is equipped with a circulator 170A as shown in Figure 12. Communication device 400B is equipped with a circulator 170B as shown in Figure 12. Note that optical switches may be used instead of circulators 170A and 170B. In the following description, the case in which communication devices 400A and 400B are equipped with circulators 170A and 170B will be described as an example.

[0180] Communication device 400A includes a signal processing unit 110A, a temperature controller 120A, a transmission unit 130A, a reception unit 140A, and a circulator 170A. Communication device 400B includes a signal processing unit 110B, a temperature controller 120B, a transmission unit 130B, a reception unit 140B, and a circulator 170B. By including the circulator 170A in communication device 400A and the circulator 170B in communication device 400B, a single-core bidirectional configuration can be achieved. The other functional units of communication devices 400A and 400B are the same as in the first embodiment.

[0181] The circulator 170A outputs the optical signal output from the transmitter 130A to the optical transmission path. The circulator 170A also outputs the optical signal transmitted from the optical transmission path to the receiver 140A.

[0182] The circulator 170B outputs the optical signal output from the transmitter 130B to the optical transmission path. The circulator 170B also outputs the optical signal transmitted from the optical transmission path to the receiver 140B.

[0183] In the following explanation, communication device 400A will be described as the transmitting communication device, and communication device 400B will be described as the receiving communication device. As mentioned above, the receiving communication device has not only a wavelength setting function but also a function to estimate the zero-dispersion wavelength in the signal processing unit. Since communication devices 400A and 400B have similar configurations, communication device 400A also has a function to estimate the zero-dispersion wavelength in addition to the wavelength setting function. Therefore, communication device 400A can also estimate the zero-dispersion wavelength.

[0184] Next, the difference between the optical communication system 40 and the optical communication system 10 is that the processing performed by the optical communication system 400 includes additional processing by circulators 170A and 170B in the communication between communication device 400A and communication device 400B. For example, as shown in Figure 12, in single-core bidirectional transmission, when communication device 400B acquires frequency spectrum data of BtB, communication device 400B may receive the leaked light from circulator 170B with the receiving unit 140B and use the spectral data of the received leaked light as frequency spectrum data of BtB. In this case, it is possible if the leaked light from circulator 170B is within the receiving sensitivity of the receiving unit 140B, and the penalty caused by the leaked light in the main signal from communication device 400A is within the system's specified limits. The same applies when communication device 400A acquires frequency spectrum data of BtB.

[0185] The signal processing units 110A and 110B estimate the zero-dispersion wavelength in the same manner as in the first embodiment.

[0186] The placement of the circulators 170A and 170B and the optical switch is not particularly limited and may be provided outside the communication devices 400A and 400B.

[0187] [Operation of Optical Communication System 40] Next, the processing flow in the optical communication system 40 will be explained. Note that the processing up to a certain point is the same as the processing shown in Figure 2, so the processing shown in Figure 2 will be used as a reference for explanation. When the processing from step S101 to step S112 is executed, the signal processing unit 110B determines the wavelength λ used for uplink communication within the wavelength range determined based on the above-mentioned equations (7) and (8). ｕＳ To decide.

[0188] In this case, the communication device 400B transmits to the communication device 400A information indicating the wavelength range determined based on the above-described equations (7) and (8) as information regarding the transmission wavelength. Alternatively, the signal processing unit 110B specifies the wavelength λ used for uplink communication within the wavelength range determined based on the above-described equations (7) and (8). ＵＳ And the wavelength λ used for downlink communication ＤＳ Both may be determined. Note that the concepts of upstream and downstream directions may be reversed. In this case, the communication device 400B determines the wavelength λ ＤＳ Information indicating this may be transmitted to the communication device 400A as information regarding the transmission wavelength. Subsequently, the communication device 400A and the communication device 400B each transmit at different wavelengths λ ＵＳ and wavelength λ ＤＳ Configure the settings and start communication.

[0189] (Other Configuration 1) Here, nine other configurations of the communication device 400A and the communication device 400B will be described using Figures 13 to 21. Figure 13 is a diagram showing another example of the configuration (1) of the optical communication system 40 in the fourth embodiment. The communication device 400A shown in Figure 13 includes a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a receiving unit 140A, an optical distribution unit 150A, an optical distribution unit 165A, and a circulator 170A.

[0190] Although not shown in Figure 13, the communication device 400B has the same configuration as the communication device 400A. Specifically, the communication device 400B comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a receiving unit 140B, an optical distribution unit 150B, an optical distribution unit 165B, and a circulator 170B. As the communication devices 400A and 400B shown in Figure 13 have the same configuration, the explanation will use the communication device 400A as an example.

[0191] When acquiring BtB frequency spectrum data in the communication device 400A, the connection path between the ports of the optical distribution unit 165A is controlled to connect the circulator 170A and the receiving unit 140A. The control of the connection path of the optical distribution unit 165A is performed by a control unit (not shown).

[0192] When communication device 400A communicates with communication device 400B, the connection path between the ports of optical distribution unit 150A is controlled to connect the circulator 170A to the optical transmission path, and the connection path between the ports of optical distribution unit 165A is controlled to connect the optical distribution unit 150A to the receiving unit 140A. The control of the connection paths of optical distribution units 150A and 165A is performed by a control unit (not shown).

[0193] (Other Configuration 2) Figure 14 shows another configuration example (part 2) of the optical communication system 40 in the fourth embodiment. The communication device 400A shown in Figure 14 comprises a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a plurality of receiving units 140A-1 to 140A-2, an optical distribution unit 165A, and a circulator 170A.

[0194] Although not shown in Figure 14, the communication device 400B has the same configuration as the communication device 400A. Specifically, the communication device 400B comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a plurality of receiving units 140B-1 to 140B-2, an optical distribution unit 165B, and a circulator 170B. As the communication devices 400A and 400B shown in Figure 14 have the same configuration, the explanation will use the communication device 400A as an example.

[0195] When acquiring frequency spectrum data of BtB in the communication device 400A, the communication device 400A may receive the leaked light from the circulator 170A with the receiving unit 140A-1 and use the spectral data of the received leaked light as frequency spectrum data of BtB.

[0196] When communication device 400A transmits a signal to communication device 400B, the connection path between the ports of the optical distribution unit 165A is controlled to connect the circulator 170A and the optical transmission path. This allows different wavelengths (for example, wavelength λ) transmitted from the transmitting unit 130A to be connected. ａ and wavelength λ ｂ The optical signal of ) is output to the optical transmission path via the circulator 170A. As a result, the communication device 400B receives signals of different wavelengths (for example, wavelength λ ａ and wavelength λ ｂ The optical signal of the optical distribution unit 165A can be received. The control of the connection path of the optical distribution unit 165A is performed by a control unit (not shown). The same applies when the communication device 400B transmits an optical signal of a different wavelength to the communication device 400A.

[0197] When communication device 400A receives a signal transmitted from communication device 400B, the connection path between the ports of the optical distribution unit 165A is controlled to connect the receiving unit 140A-2 and the optical transmission path. As a result, the optical signal input via the optical transmission path is input to the receiving unit 140A-2 via the optical distribution unit 165A. Consequently, communication device 400A can receive the optical signal transmitted from communication device 400B. The control of the connection path of the optical distribution unit 165A is performed by a control unit (not shown). The same applies when communication device 400B receives an optical signal from communication device 400A.

[0198] (Other Configuration 3) Figure 15 shows another configuration example (part 3) of the optical communication system 40 in the fourth embodiment. The communication device 400A shown in Figure 15 comprises a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a receiving unit 140A, an optical distribution unit 165A, and a circulator 170A.

[0199] Although not shown in Figure 15, the communication device 400B has the same configuration as the communication device 400A. That is, the communication device 400B comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a receiving unit 140B, an optical distribution unit 165B, and a circulator 170B. As the communication devices 400A and 400B shown in Figure 15 have the same configuration, the explanation will use the communication device 400A as an example.

[0200] In the communication device 400A shown in Figure 15, when acquiring frequency spectrum data of BtB, the optical distribution unit 165A controls the connection path between ports to connect the transmitting unit 130A and the receiving unit 140A. As a result, the optical signal of wavelength λ transmitted from the transmitting unit 130A is received by the receiving unit 140A via the optical distribution unit 165A. Consequently, the signal processing unit 110A can acquire frequency spectrum data of BtB. The same applies when acquiring frequency spectrum data of BtB in the communication device 400B.

[0201] In the configuration shown in Figure 15, when communication is performed between communication device 400A and communication device 400B, the optical distribution unit 165A controls the connection path between ports so as to connect the transmitting unit 130A and the circulator 170A. As a result, different wavelengths (for example, wavelength λ) transmitted from the transmitting unit 130A are connected. ａ and wavelength λ ｂ The optical signal of ) is output to the optical transmission path via the circulator 170A. As a result, the communication device 400B receives signals of different wavelengths (for example, wavelength λ ａ and wavelength λ ｂ The optical signals of the two devices can be received. The same applies when the communication device 400B transmits optical signals of different wavelengths to the communication device 400A.

[0202] (Other Configuration 4) Figure 16 shows another configuration example (number 4) of the optical communication system 40 in the fourth embodiment. The communication device 400A shown in Figure 16 includes a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a plurality of receiving units 140A-1 to 140A-2, an optical splitter 155A, and a circulator 170A.

[0203] Although not shown in Figure 16, the communication device 400B has the same configuration as the communication device 400A. Specifically, the communication device 400B comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a plurality of receiving units 140B-1 to 140B-2, an optical splitter 155B, and a circulator 170B. As the communication devices 400A and 400B shown in Figure 16 have the same configuration, the explanation will use the communication device 400A as an example.

[0204] In the communication device 400A shown in Figure 16, when acquiring frequency spectrum data of BtB, the transmitting unit 130A transmits an optical signal with wavelength λ. The optical signal with wavelength λ transmitted from the transmitting unit 130A is branched by the optical splitter 155A and input to the receiving unit 140A-1. The receiving unit 140A-1 receives the optical signal with wavelength λ that has been branched by the optical splitter 155A. As a result, the signal processing unit 110A can acquire frequency spectrum data of BtB. The same applies when acquiring frequency spectrum data of BtB in the communication device 400B.

[0205] In the configuration shown in Figure 16, when communication is performed between communication device 400A and communication device 400B, the transmitting unit 130A uses different wavelengths (for example, wavelength λ). ａ and wavelength λ ｂ It transmits an optical signal of a different wavelength (for example, wavelength λ) transmitted from the transmitting unit 130A. ａ and wavelength λ ｂ The optical signal of ) is output to the optical transmission path via the circulator 170A. As a result, the communication device 400B receives signals of different wavelengths (for example, wavelength λ ａ and wavelength λ ｂ The optical signals of the two devices can be received. The same applies when the communication device 400B transmits optical signals of different wavelengths to the communication device 400A.

[0206] (Other Configuration 5) Figure 17 shows another configuration example (number 5) of the optical communication system 40 in the fourth embodiment. The communication device 400A shown in Figure 17 includes a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a receiving unit 140A, an optical splitter 155A, an optical distribution unit 165A, and a circulator 170A.

[0207] Although not shown in Figure 17, the communication device 400B has the same configuration as the communication device 400A. Specifically, the communication device 400B includes a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a receiving unit 140B, an optical splitter 155B, an optical distribution unit 165B, and a circulator 170B. As the communication devices 400A and 400B shown in Figure 17 have the same configuration, the explanation will use the communication device 400A as an example.

[0208] In the communication device 400A shown in Figure 17, when acquiring frequency spectrum data of BtB, the optical splitter 165A controls the connection path between ports to connect the optical splitter 155A and the receiving unit 140A. As a result, the optical signal of wavelength λ transmitted from the transmitting unit 130A is received by the receiving unit 140A via the optical splitter 155A and the optical splitter 165A. Consequently, the signal processing unit 110A can acquire frequency spectrum data of BtB. The same applies when acquiring frequency spectrum data of BtB in the communication device 400B.

[0209] In the configuration shown in Figure 17, when communication is performed between communication device 400A and communication device 400B, the optical distribution unit 165A controls the connection path between ports to connect the circulator 170A and the receiving unit 140A. As a result, the receiving unit 140A can receive optical signals of different wavelengths transmitted from communication device 400B via the circulator 170A and the optical distribution unit 165A. By performing similar control in communication device 400B, the same effect can be obtained when transmitting optical signals of different wavelengths from communication device 400A to communication device 400B.

[0210] With the optical communication system 40 configured as described above, the same effects as in the first embodiment can be obtained even in a single-core bidirectional configuration.

[0211] (Modification 1 in the fourth embodiment) Instead of the circulator 170A, a wavelength filter that separates the optical signal according to its wavelength may be used.

[0212] (Modification 2 in the fourth embodiment) The communication devices 400A and 400B shown in Figure 13 may be equipped with optical couplers instead of optical distribution units 165A and 165B. Also, in the configuration shown in Figure 13, the optical distribution unit 150A, the optical distribution unit 165A, and the circulator 170A may be provided outside the communication device 400A, or they may be configured as a single device, for example. The same applies to the communication device 400B.

[0213] (Modification 3 in the fourth embodiment) The communication devices 400A and 400B shown in Figure 14 may be equipped with optical couplers instead of optical distribution units 165A and 165B. Also, in the configuration shown in Figure 14, the optical distribution unit 165A and the circulator 170A may be provided outside the communication device 400A, or they may be configured as a single device, for example. The same applies to the communication device 400B.

[0214] (Modification 4 in the fourth embodiment) The communication devices 400A and 400B shown in Figure 15 may be equipped with optical couplers instead of optical distribution units 165A and 165B. Also, in the configuration shown in Figure 15, the circulator 170A may be provided outside the communication device 400A. The same applies to the communication device 400B.

[0215] (Modification 5 in the fourth embodiment) In the configuration shown in Figure 16, the circulator 170A may be provided outside the communication device 400A, or it may be configured as a single device, for example. The same applies to the communication device 400B.

[0216] (Modification 6 in the fourth embodiment) The communication devices 400A and 400B shown in Figure 17 may be equipped with optical couplers instead of optical distribution units 165A and 165B. Also, in the configuration shown in Figure 17, the circulator 170A may be provided outside the communication device 400A, or it may be configured as a single device, for example. The same applies to the communication device 400B.

[0217] (Fifth Embodiment) In the fifth embodiment, a configuration is described in which communication devices are connected by a single optical transmission line, and each communication device is equipped with multiple lasers to acquire BtB frequency spectrum data.

[0218] Figure 18 shows an example configuration of the optical communication system 50 in the fifth embodiment. The optical communication system 50 comprises a communication device 500A and a communication device 500B. Communication devices 500A and 500B communicate via an optical transmission path. Communication devices 500A and 500B communicate by single-core bidirectional transmission using a single optical transmission path. In the following description, the direction from communication device 500A to communication device 500B is referred to as the downstream direction, and the direction from communication device 500B to communication device 500A is referred to as the upstream direction.

[0219] The communication device 500A comprises a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a receiving unit 140A, a wavelength filter 160A, an optical distribution unit 165A, and a circulator 170A. The transmitting unit 130A comprises a plurality of lasers 131A-1 to 131A-2, an optical distribution unit 132A, a signal generation unit 133A, and an optical modulator 134A. The communication device 500A shown in Figure 18 differs in configuration from the communication device 300A shown in Figure 7 in that it includes a circulator 170A. The other functional units of the communication device 500A perform the same processing as the communication device 300A shown in Figure 7.

[0220] Although not shown in Figure 18, the communication device 500B has the same configuration as the communication device 500A. Specifically, the communication device 500B comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a receiving unit 140B, a wavelength filter 160B, an optical distribution unit 165B, and a circulator 170B. As the communication devices 500A and 500B shown in Figure 18 have the same configuration, the explanation will use the communication device 500A as an example.

[0221] In communication devices 500A and 500B, when acquiring frequency spectrum data of BtB, the same process as shown in Figure 8 is performed.

[0222] During communication between communication device 500A and communication device 500B, the optical distribution unit 165A sets the connection path to connect the receiving unit 140A and the circulator 170A, and the optical distribution unit 165B sets the connection path to connect the receiving unit 140B and the circulator 170B. In this configuration, the optical signal transmitted from communication device 500B is output to the optical distribution unit 165A by the circulator 170A. The optical distribution unit 165A outputs the optical signal output from the circulator 170A to the receiving unit 140A. Similarly, the optical signal transmitted from communication device 500A is output to the optical distribution unit 165B by the circulator 170B. The optical distribution unit 165B outputs the optical signal output from the circulator 170B to the receiving unit 140B.

[0223] (Other Configuration 1) Here, three other configurations of the communication device 500A and the communication device 500B will be described using Figures 19 to 21. Figure 19 is a diagram showing another configuration example (part 1) of the optical communication system 50 in the fifth embodiment. The communication device 500A shown in Figure 19 includes a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a plurality of receiving units 140A-1 to 140A-2, a wavelength filter 160A, and a circulator 170A. The transmitting unit 130A includes a plurality of lasers 131A-1 to 131A-2, an optical distribution unit 132A, a signal generation unit 133A, and an optical modulator 134A. The communication device 500A shown in Figure 19 differs in configuration from the communication device 300A shown in Figure 9 in that it includes a circulator 170A. The other functional units of the communication device 500A perform the same processing as the communication device 300A shown in Figure 9.

[0224] Although not shown in Figure 19, the communication device 500B has the same configuration as the communication device 500A. Specifically, the communication device 500B comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a plurality of receiving units 140B-1 to 140B-2, a wavelength filter 160B, and a circulator 170B. The transmitting unit 130B comprises a plurality of lasers 131B-1 to 131B-2, an optical distribution unit 132B, a signal generation unit 133B, and an optical modulator 134B. As the communication devices 500A and 500B shown in Figure 19 have the same configuration, the explanation will use the communication device 500A as an example.

[0225] In communication devices 500A and 500B, when acquiring frequency spectrum data of BtB, the same process as described in Figure 9 is performed.

[0226] During communication between communication device 500A and communication device 500B, the optical signal transmitted from communication device 500B is output to the receiving unit 140A-2 by the circulator 170A. Similarly, the optical signal transmitted from communication device 500A is output to the receiving unit 140B-2 by the circulator 170B.

[0227] (Other Configuration 2) Figure 20 shows another configuration example (part 2) of the optical communication system 50 in the fifth embodiment. The communication device 500A shown in Figure 20 includes a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a receiving unit 140A, an optical distribution unit 165A, and a circulator 170A. The transmitting unit 130A includes a plurality of lasers 131A-1 to 131A-2, a signal generation unit 133A, and a plurality of optical modulators 134A-1 to 134A-2. The communication device 500A shown in Figure 20 differs in configuration from the communication device 300A shown in Figure 10 in that it includes a circulator 170A. The other functional units of the communication device 500A perform the same processing as the communication device 300A shown in Figure 10.

[0228] Although not shown in Figure 20, the communication device 500B has the same configuration as the communication device 500A. Specifically, the communication device 500B includes a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a receiving unit 140B, an optical distribution unit 165B, and a circulator 170B. The transmitting unit 130B includes a plurality of lasers 131B-1 to 131B-2, a signal generation unit 133B, and a plurality of optical modulators 134B-1 to 134B-2. As the communication devices 500A and 500B shown in Figure 20 have the same configuration, the explanation will use the communication device 500A as an example.

[0229] In the communication devices 500A and 500B, when acquiring frequency spectrum data of BtB, the same process as described in Figure 10 is performed.

[0230] During communication between communication device 500A and communication device 500B, the optical distribution unit 165A sets the connection path to connect the receiving unit 140A and the circulator 170A, and the optical distribution unit 165B sets the connection path to connect the receiving unit 140B and the circulator 170B. In this configuration, the optical signal transmitted from communication device 500B is output to the optical distribution unit 165A by the circulator 170A. The optical distribution unit 165A outputs the optical signal output from the circulator 170A to the receiving unit 140A. Similarly, the optical signal transmitted from communication device 500A is output to the optical distribution unit 165B by the circulator 170B. The optical distribution unit 165B outputs the optical signal output from the circulator 170B to the receiving unit 140B.

[0231] (Other Configuration 3) Figure 21 shows another configuration example (part 3) of the optical communication system 50 in the fifth embodiment. The communication device 500A shown in Figure 21 includes a signal processing unit 110A, a temperature controller 120A, a transmitting unit 130A, a plurality of receiving units 140A-1 to 140A-2, and a circulator 170A. The transmitting unit 130A includes a plurality of lasers 131A-1 to 131A-2, a signal generation unit 133A, and a plurality of optical modulators 134A-1 to 134A-2. The communication device 500A shown in Figure 21 differs in configuration from the communication device 300A shown in Figure 11 in that it includes a circulator 170A. The other functional units of the communication device 500A perform the same processing as the communication device 300A shown in Figure 11.

[0232] Although not shown in Figure 21, the communication device 500B has the same configuration as the communication device 500A. Specifically, the communication device 500B comprises a signal processing unit 110B, a temperature controller 120B, a transmitting unit 130B, a plurality of receiving units 140B-1 to 140B-2, and a circulator 170B. The transmitting unit 130B comprises a plurality of lasers 131B-1 to 131B-2, a signal generating unit 133B, and a plurality of optical modulators 134B-1 to 134B-2. As the communication devices 500A and 500B shown in Figure 21 have the same configuration, the explanation will use the communication device 500A as an example.

[0233] In the communication devices 500A and 500B, when acquiring frequency spectrum data of BtB, the same process as described in Figure 11 is performed.

[0234] During communication between communication device 500A and communication device 500B, the optical signal transmitted from communication device 500B is output to the receiving unit 140A-2 by the circulator 170A. Similarly, the optical signal transmitted from communication device 500A is output to the receiving unit 140B-2 by the circulator 170B.

[0235] With the optical communication system 50 configured as described above, the same effects as in the first embodiment can be obtained even in a single-core bidirectional configuration.

[0236] (Modification 1 in the fifth embodiment) Instead of the circulator 170A, a wavelength filter that separates the optical signal according to its wavelength may be used.

[0237] (Modification 2 in the fifth embodiment) The communication devices 500A and 500B shown in Figure 18 may be equipped with optical couplers instead of optical distribution units 132A and 132B. The communication devices 500A and 500B shown in Figure 18 may be equipped with optical couplers instead of optical distribution units 165A and 165B. In addition, in the configuration shown in Figure 18, the wavelength filter 160A, the optical distribution unit 165A, and the circulator 170A may be provided outside the communication device 500A, and may be configured as a single device, for example. The same applies to the communication device 500B.

[0238] (Modification 3 in the fifth embodiment) The communication devices 500A and 500B shown in Figure 19 may be equipped with optical couplers instead of optical distribution units 132A and 132B. Also, in the configuration shown in Figure 19, the wavelength filter 160A and the circulator 170A may be provided outside the communication device 500A, or they may be configured as a single device, for example. The same applies to the communication device 500B.

[0239] (Modification 4 in the fifth embodiment) The communication devices 500A and 500B shown in Figure 20 may be equipped with optical couplers instead of optical distribution units 165A and 165B. Also, in the configuration shown in Figure 20, the optical distribution unit 165A and the circulator 170A may be provided outside the communication device 500A, or they may be configured as a single device, for example. The same applies to the communication device 500B.

[0240] (Modification 5 in the fifth embodiment) In the configuration shown in Figure 21, the circulator 170A may be provided outside the communication device 500A. The same applies to the communication device 500B.

[0241] (Other Application Examples) Each communication device in the first to fifth embodiments can also be applied to the configuration shown in Figure 22. Figure 22 is a diagram showing an example of the configuration of an optical communication system 60 applicable to each embodiment. In Figure 22, the case where it is applied to the communication device 100A and communication device 100B in the first embodiment is shown as an example. The optical communication system 60 comprises a plurality of communication devices 100A-1 to 100A-P (P is an integer of 2 or more), a plurality of communication devices 100B-1 to 100B-Q (Q is an integer of 2 or more), a control device 600, and an optical distribution unit 650. Thus, in the optical communication system 60 shown in Figure 22, an optical distribution unit 550 is provided between each communication device 100A and each communication device 100B.

[0242] The optical distribution unit 550 outputs an optical signal input from one optical transmission path to another transmission path. The optical distribution unit 550 may be an optical switch, a ROADM (Reconfigurable Optical Add-Drop Multiplexer), or any configuration that can switch the destination of the optical signal. The optical distribution unit 550 switches the connection path according to the instructions of the control device 600.

[0243] The control device 600 controls the optical distribution unit 550. For example, the control device 600 controls the destinations to which the optical distribution unit 550 is connected so that communication devices connected to the optical distribution unit 550 can communicate with each other.

[0244] (Modifications common to the fourth and fifth embodiments) In the fourth and fifth embodiments, the communication devices 400A and 400B, and the communication devices 500A and 500B have similar configurations. Therefore, both the signal processing unit 110A in the communication devices 400A and 500A, and the signal processing unit 110B in the communication devices 400B and 500B, have both a function to set the wavelength and a function to estimate the zero-dispersion wavelength. Here, the function to set the wavelength is a function to control the transmission wavelength of the transmission units 130A and 130B by controlling the temperature controllers 120A and 120B. The function to estimate the zero-dispersion wavelength is a function to estimate the deviation amount Δλ from the zero-dispersion wavelength or the zero-dispersion wavelength.

[0245] When connected by a single optical fiber, the same path is used for transmission and reception, so the zero-dispersion wavelength is assumed to be the same. Therefore, the function of estimating the zero-dispersion wavelength only needs to be possessed by either the signal processing unit 110A or the signal processing unit 110B. For example, the signal processing unit 110B may have both the function of setting the wavelength and the function of estimating the zero-dispersion wavelength, while the signal processing unit 110A may have only the function of setting the wavelength (without the function of estimating the zero-dispersion wavelength). Conversely, the signal processing unit 110A may have both the function of setting the wavelength and the function of estimating the zero-dispersion wavelength, while the signal processing unit 110B may have only the function of setting the wavelength (without the function of estimating the zero-dispersion wavelength). In such configurations, the signal processing unit 110A or 110B may use the estimated zero-dispersion wavelength value to control the wavelengths of both the transmitting unit 130B of its own device (communication device 400B, 500B) and the transmitting unit 130A of the communication device 400A, 500A.

[0246] Here, we will explain how the signal processing unit 110B controls the wavelengths of both the transmitter 130B of its own device (communication devices 400B, 500B) and the transmitter 130A of the communication devices 400A, 500A. For example, the signal processing unit 110B controls the transmitter 130A to transmit information indicating the estimated zero-dispersion wavelength to the communication devices 400A, 500A. As a result, information indicating the zero-dispersion wavelength is transmitted to the communication devices 400A, 500A. This allows the wavelength of the transmitter 130A of the communication devices 400A, 500A to be controlled. Furthermore, the signal processing unit 110B refers to the correspondence information and obtains temperature information corresponding to the estimated zero-dispersion wavelength. The signal processing unit 110B sets the temperature controller 120B so that the temperature is as indicated by the acquired temperature information. The temperature controller 120B adjusts the temperature of the transmitter 130B so that the temperature is as set. This allows the signal processing unit 110A to control the transmission wavelength of the transmitting unit 130B that the device is equipped with.

[0247] As another example, the signal processing unit 110B may have only the function of estimating the zero-dispersion wavelength (without the function of setting the wavelength), and the signal processing unit 110A may have only the function of setting the wavelength (without the function of estimating the zero-dispersion wavelength). Conversely, the signal processing unit 110B may have only the function of setting the wavelength (without the function of estimating the zero-dispersion wavelength), and the signal processing unit 110A may have only the function of estimating the zero-dispersion wavelength (without the function of setting the wavelength). In this configuration, the signal processing unit 110A controls the wavelength of the transmitter unit 130B of the communication devices 400B and 500B using the estimated zero-dispersion wavelength value, and the signal processing unit 110B controls the wavelength of the transmitter unit 130A of the communication devices 400A and 500A using the estimated zero-dispersion wavelength value. For example, in such cases, it is conceivable that communication devices 400A and 500A transmit signals that are susceptible to wavelength dispersion, such as high-speed signals, while communication devices 400A and 500A transmit low-speed signals that are less susceptible to wavelength dispersion, or high-speed signals that have been made less susceptible to wavelength dispersion through pre-compensation or multi-leveling.

[0248] As another example, the signal processing unit 110B may have both a function to set the wavelength and a function to estimate the zero-dispersion wavelength, while the signal processing unit 110A may not have either a function to estimate the zero-dispersion wavelength or a function to set the wavelength (neither a function to set the wavelength nor a function to estimate the zero-dispersion wavelength). Conversely, the signal processing unit 110B may not have either a function to estimate the zero-dispersion wavelength or a function to set the wavelength (neither a function to set the wavelength nor a function to estimate the zero-dispersion wavelength), while the signal processing unit 110A may have both a function to set the wavelength and a function to estimate the zero-dispersion wavelength. In such a configuration, the signal processing unit 110A or 110B controls the wavelength of the transmitter unit 130B provided in its device using the estimated value of the zero-dispersion wavelength. For example, in such cases, it is conceivable that communication devices 400A and 500A transmit relatively slow signals that are less susceptible to chromatic dispersion (slow signals that produce notches) or high-speed signals that have been made less susceptible to chromatic dispersion through pre-compensation or multi-leveling, while communication devices 400B and 500B transmit high-speed signals that can reduce the effects of chromatic dispersion by setting the wavelength.

[0249] Here, we will describe an example configuration in which the signal processing unit 110B of communication devices 400B and 500B has both a function to set the wavelength and a function to estimate the zero-dispersion wavelength, while the signal processing unit 110A of communication devices 400A and 500A does not have either a function to estimate the zero-dispersion wavelength or a function to set the wavelength (it has neither a function to set the wavelength nor a function to estimate the zero-dispersion wavelength). The signal processing unit 110B controls the wavelength of the transmitter unit 130B equipped with its own device using one of the zero-dispersion wavelength candidates (up to two candidates) estimated by the method described in the embodiment. The signal processing unit 110B first selects one of the wavelengths that are candidates for the zero-dispersion wavelength (for example, the first wavelength λ ０,１ Select ).

[0250] The signal processing unit 110B selects the first wavelength λ ０,１ The system acquires temperature information corresponding to the acquired temperature information and transmits from the transmission unit 130B at the first wavelength λ ０,１The optical signal is transmitted to the communication devices 400A and 500A. When the receiving unit 140A of the communication devices 400A and 500A receives the optical signal transmitted from the communication devices 400B and 500B, the communication devices 400A and 500A begin communication with the communication devices 400B and 500B. Here, "successful reception" refers to situations such as when, within a specific time frame in which a series of operations can be performed—including when communication devices 400A and 500A send an optical signal to communication devices 400B and 500B, communication devices 400B and 500B estimate the zero-dispersion wavelength, communication devices 400B and 500B set the estimated zero-dispersion wavelength to the transmitter unit 130B and oscillate, and communication devices 400A and 500A receive the signal—communication device 400A notifies communication devices 400B and 500B to notify an optical signal of a specific piece of information, and within that specific time frame, communication devices 400B and 500B notify communication devices 400A and 500A of an optical signal of a specific piece of information. In this case, communication devices 400A and 500A transmit using low-speed signals or high-speed signals that are less susceptible to wavelength dispersion through pre-compensation or multi-leveling.

[0251] On the other hand, if the receiving unit 140A of the communication devices 400A and 500A is unable to receive the optical signal transmitted from the communication devices 400B and 500B, the communication devices 400A and 500A will notify the communication devices 400B and 500B that the signal could not be received. Here, a case where reception failed is, for example, when, within a specific time frame in which a series of operations can be performed—where communication devices 400A and 500A send an optical signal to communication devices 400B and 500B, communication devices 400B and 500B estimate the zero-dispersion wavelength, communication devices 400B and 500B set the estimated zero-dispersion wavelength to the transmitter unit 130B and oscillate, and communication devices 400A and 500A receive it—communication devices 400A and 500A notify communication devices 400B and 500B to notify an optical signal of a specific piece of information, but within that specific time frame, communication devices 400B and 500B do not notify communication devices 400A and 500A of an optical signal of a specific piece of information. ０,２The device oscillates using an optical signal. Subsequently, communication begins between communication devices 400A, 500A and 400B, 500B. The method for determining whether reception is possible shown here is just one example; other methods may be used to determine whether reception is possible, and the method is not restricted.

[0252] With this configuration, it is not necessary for both communication devices 400A, 500A and 400B, 500B to have the function of estimating the zero-dispersion wavelength. Therefore, the cost of communication device 200, which does not have the function of estimating the zero-dispersion wavelength, can be reduced. Furthermore, one communication device 200 (for example, communication devices 400B, 500B) can estimate the zero-dispersion wavelength and control the wavelength used for communication between the transmitting unit 130 (for example, transmitting unit 130A) of the opposing communication devices 400, 500 (for example, communication devices 400A, 500A) and the transmitting unit 130 (for example, transmitting unit 130B) of its own device. This enables efficient communication.

[0253] Furthermore, as described above, the present invention can be applied even if one of the communication devices 400, 500 does not have either a function to estimate the zero-dispersion wavelength or a function to set the wavelength (i.e., it has neither a function to set the wavelength nor a function to estimate the zero-dispersion wavelength).

[0254] (Modification 1 common to the first to fifth embodiments) In the embodiments described above, each communication device (for example, communication devices 100A, 100B, 200A, 200B, 300A, 300B, 400A, 400B, 500A, 500B) is shown to change the transmission wavelength of the transmitting units 130A, 130B using temperature controllers 120A, 120B. However, the configuration for changing the transmission wavelength in each communication device is not limited to this. For example, a configuration using a current controller or a configuration using an array laser may be applied as a configuration for changing the transmission wavelength in each communication device.

[0255] First, we will explain the case where a configuration using a current controller is applied. Similar configurations can be assumed for each communication device, but here we will explain using communication device 100A as an example. Communication device 100A includes a signal processing unit 110A, a transmitting unit 130A, a plurality of receiving units 140A-1 to 140A-2, an optical distribution unit 150A, and a current controller. Communication device 100A is equipped with a current controller in place of the temperature controller 120A.

[0256] The signal processing unit 110A performs various signal processing on the optical signal received by the receiving unit 140A. Furthermore, the signal processing unit 110A sets the wavelength of the optical signal to be transmitted to the communication device 100B by the transmitting unit 130A. The signal processing unit 110A maintains correspondence information that shows the correspondence between wavelength and current. This correspondence information includes, for example, information indicating the current to be applied to the laser corresponding to each wavelength, associated with each wavelength. That is, the correspondence information includes the wavelength λ １ Corresponding to current C １ , wavelength λ ２ Corresponding to current C ２ This includes information such as the above. Note that this is just one example, and the current value is determined within a predetermined range.

[0257] Therefore, the signal processing unit 110A obtains current information corresponding to the wavelength used for communication by referring to the correspondence information, and sets the current controller to the current indicated by the obtained current information. For example, if the signal processing unit 110A obtains information indicating a zero-dispersion wavelength from the communication device 100B, it obtains current information corresponding to the wavelength specified by the obtained zero-dispersion wavelength information by referring to the correspondence information, and sets the current controller to the current indicated by the obtained current information. As a result, the signal processing unit 110A sets the wavelength of the optical signal to be transmitted to the communication device 100B in the transmission unit 130A.

[0258] The current controller applies current to the transmitting unit 130A at a current value set by the signal processing unit 110A. The transmitting unit 130A is, for example, a tunable laser, and transmits an optical signal with a wavelength corresponding to the current value.

[0259] Next, we will describe the case where a configuration using an array laser is applied. Similar configurations can be assumed for each communication device, but here we will explain using communication device 100A as an example. Communication device 100A includes a signal processing unit 110A, a plurality of receiving units 140A-1 to 140A-2, an optical distribution unit 150A, an array laser, and a multiplexer. Communication device 100A includes an array laser and a multiplexer in place of the temperature controller 120A and the transmitting unit 130A.

[0260] The signal processing unit 110A performs various signal processing on the optical signal received by the receiving unit 140A. Furthermore, the signal processing unit 110A selects an oscillating laser corresponding to a desired wavelength and sets the array laser to output a signal from the selected oscillating laser. While the desired wavelength is preferably a zero-dispersion wavelength, it is conceivable that there may be no laser corresponding to the zero-dispersion wavelength value. Therefore, if there is no laser corresponding to the zero-dispersion wavelength value, the signal processing unit 110A may select a laser with the value closest to the zero-dispersion wavelength value. The array laser has a wavelength λ １ from λ ｋ The array laser system comprises multiple lasers capable of oscillating at various wavelengths up to (k being an integer greater than or equal to 1). The array laser drives the set oscillating lasers to output optical signals. The multiplexer combines the optical signals of one or more wavelengths output from the array laser. The multiplexer outputs the combined optical signal to an optical transmission path.

[0261] As described above, any method can be used to change the wavelength. This embodiment is applicable as long as the zero-dispersion wavelength of the optical fiber and the range of the transmission wavelength overlap (it is not limited to wavelengths of 1300 to 1324 nm).

[0262] (Modification 2 common to the first to fifth embodiments) In each of the embodiments described above, the transmitting communication device (for example, communication devices 100A, 200A, 300A, 400A, 500A) that transmits an optical signal for estimating the zero-dispersion wavelength may simultaneously transmit optical signals of two wavelengths to the receiving communication device (for example, communication devices 100B, 200B, 300B, 400B, 500B). In this configuration, the transmitting communication device comprises two or more transmitting units (for example, transmitting unit 130A), and the receiving communication device comprises two or more receiving units (for example, receiving unit 140B) for receiving the optical signals transmitted from the transmitting communication device. Furthermore, the receiving communication device is equipped with an optical filter (a tunable filter set to cut one wavelength and allow the other wavelength to pass through) in front of each receiving unit (for example, receiving unit 140B). This allows the receiving communication device to receive two optical signals of different wavelengths transmitted through the same optical fiber using different receiving units (for example, receiving unit 140B).

[0263] (Modification 3 common to the first to fifth embodiments) Zero-dispersion wavelength λ ０ The method for narrowing down to one is not limited to the method described above. If it is not possible to narrow down the candidates for the zero-dispersion wavelength to one, communication devices 100B, 200B, 300B, 400B, and 500B may narrow down the candidates for the zero-dispersion wavelength to one using the method shown below. Here, communication device 100B will be used as an example. Communication device 100B uses the first wavelength λ ０,１ Information indicating the value of the first wavelength λ is transmitted to the communication device 100A, ０,１ The optical signal is received from the communication device 100A. The signal processing unit 110B receives the first wavelength λ ０,１ From the frequency spectrum data of the optical signal, f ｎ,ａ Check if a notch appears at the following frequencies. More specifically, the signal processing unit 110B checks the first wavelength λ ０,１ In the frequency spectrum data of the optical signal, the (n+1)th notch frequency f ｎ,（０,１） However, wavelength λ ａ The (n+1)th notch frequency f in the spectral data obtained at that time (i.e., the first data obtained) ｎ,ａIt may not be present at a lower frequency, or it may be related to the first wavelength λ. ０,１ In the frequency spectrum data of an optical signal, the notch is wavelength λ ａ The f obtained at that time (i.e., the first one obtained) ０,ａ Check if it's appearing at a lower frequency. f ｎ,ａ If no notch is present at the following frequencies, the signal processing unit 110B controls the transmission unit 130B to send information that the wavelength setting is correct (for example, notch appearance information (none)) to the communication device 100A using a low-speed signal. Upon receiving the information that the wavelength setting is correct (for example, notch appearance information (none)), the communication device 100A determines that the zero-dispersion wavelength is the first wavelength λ. ０,１ It can be determined that this is the case.

[0264] On the other hand, f ｎ,ａ If a notch appears at the following frequencies, the signal processing unit 110B controls the transmission unit 130B to provide information that the wavelength setting is incorrect (for example, notch appearance information (present)) and the second wavelength λ ０,２ Information indicating this is sent to the communication device 100A. As a result, the communication device 100A will know that the zero-dispersion wavelength is the second wavelength λ. ０,２ It can be determined that this is the case.

[0265] In the embodiments described above, the signal processing units 110A and 110B may be configured using a processor such as a CPU (Central Processing Unit) and memory. In this case, the signal processing units 110A and 110B function when the processor executes a program. Furthermore, all or part of the functions of the signal processing units 110A and 110B 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).

[0266] 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, CD-ROMs, and semiconductor memory devices (e.g., SSDs: Solid State Drives), as well as storage devices such as hard disks and semiconductor memory devices built into computer systems. The above program may also be transmitted via telecommunications lines.

[0267] 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.

[0268] The present invention is applicable to optical communication systems that communicate via optical transmission paths.

[0269] 10, 20, 30, 40, 50, 60... Optical communication system, 100A, 100B, 200A, 200B, 300A, 300B, 400A, 400B, 500A, 500B, 100A-1 to 100A-P, 100B-1 to 100B-Q... Communication device, 110A, 110B... Signal processing unit, 120A, 120B... Temperature controller, 130A, 130B... Transmitter, 131A, 131A-1 to 131A-2, 131B, 131B-1 to 131B-2... Laser, 132A, 132B... Optical distribution unit, 133A, 133B... Signal generation unit, 134A, 134A-1 to 134A-2, 134B, 134B-1 to 134B-2... Optical modulators, 140A, 140A-1 to 140A-2, 140B, 140B-1 to 140B-2... Receiving units, 150A, 150B... Optical distribution units, 155A, 155B... Optical splitters, 160A, 160B... Wavelength filters, 165A, 165B... Optical distribution units, 170A, 170B... Circulators

Claims

1. A communication device comprising: a transmitting unit that transmits one or more optical signals of wavelengths; a plurality of optical signals of different wavelengths transmitted from a communication device of a communication partner connected via an optical transmission path; one or more receiving units that receive a portion of the one or more optical signals of wavelengths transmitted from the transmitting unit; and a signal processing unit that acquires pre-transmission data used to detect frequencies attenuated due to chromatic dispersion based on a portion of the one or more optical signals of wavelengths transmitted from the transmitting unit, and estimates zero-dispersion wavelengths based on the acquired pre-transmission data and the frequency spectra of each of the plurality of optical signals.

2. The communication device according to claim 1, further comprising one or more optical components that output a portion of the one or more wavelength optical signals transmitted from the transmitting unit toward one or more receiving units.

3. The communication device according to claim 2, wherein the one or more optical components are at least one of an optical coupler that branches an input optical signal at a predetermined branching ratio, an optical distribution unit that outputs an input optical signal to another path, a filter that separates an input optical signal according to wavelength, or a circulator.

4. The communication device according to any one of claims 1 to 3, wherein the transmitting unit includes a plurality of lasers that output light in different wavelength bands, and one or more modulators that generate one or more optical signals of one or more wavelengths based on the light output from the plurality of lasers, and one or more receiving units that receive a portion of the one or more optical signals of one or more wavelengths generated by the one or more modulators based on the light output from at least one of the plurality of lasers.

5. The communication device according to any one of claims 1 to 3, wherein the one or more receiving units include a first receiving unit that directly or indirectly receives a portion of the one or more optical signals of the one or more wavelengths transmitted from the transmitting unit, and a second receiving unit that receives a plurality of optical signals of different wavelengths transmitted from the communication device of the communication partner.

6. An optical communication system comprising a first communication device and a second communication device connected via an optical transmission path, wherein the first communication device comprises a transmitting unit that transmits a plurality of optical signals of different wavelengths to the second communication device via an optical transmission path, and the second communication device comprises a transmitting unit that transmits one or more optical signals of one or more wavelengths, one or more receiving units that receive the plurality of optical signals of different wavelengths transmitted from the first communication device and a portion of the one or more optical signals of one or more wavelengths transmitted from the transmitting unit, and a signal processing unit that acquires pre-transmission data used to detect frequencies attenuated due to chromatic dispersion based on a portion of the one or more optical signals of one or more wavelengths transmitted from the transmitting unit, and estimates a zero-dispersion wavelength based on the acquired pre-transmission data and the frequency spectrum of each of the plurality of optical signals.

7. A zero-dispersion wavelength estimation method that transmits one or more optical signals of wavelengths, receives a portion of the one or more optical signals of wavelengths transmitted from a communication device of a communication partner connected via an optical transmission path, acquires pre-transmission data used to detect frequencies attenuated due to chromatic dispersion based on the portion of the one or more optical signals of wavelengths, and estimates the zero-dispersion wavelength based on the acquired pre-transmission data and the frequency spectra of each of the multiple optical signals.

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