Band identifying circuit, wavelength-multiplexed optical signal transmission device, wavelength-multiplexed optical signal transmission system, and band identifying method

In order to identify occupied bands in an optical transmitter with high accuracy, a band identifying circuit includes an optical intensity controller configured to change, by a prescribed level, an optical intensity of an optical signal outputted from a target-of-identification optical transmitter among a plurality of optical signals respectively outputted from a plurality of optical transmitters, constituting a wavelength-multiplexed optical signal, and having mutually different wavelengths, a spectrum acquisition circuit configured to measure an optical intensity of each wavelength of the wavelength-multiplexed optical signal and output a result of the measurement as a spectrum, and a band identifier configured to identify a band occupied by the target-of-identification optical transmitter, based on a change amount of the outputted spectrum.

This application is a National Stage Entry of PCT/JP2017/003588 filed on Feb. 1, 2017, which claims priority form Japanese Patent Application 2016-017632 filed on Feb. 2, 2016, the contents of all of which are incorporated herein by reference, in their entirety.

TECHNICAL FIELD

The present invention relates to a band identifying circuit, a wavelength-multiplexed optical signal transmission device, a wavelength-multiplexed optical signal transmission system, and a band identifying method, and more particularly, to a band identifying circuit, a wavelength-multiplexed optical signal transmission device, a wavelength-multiplexed optical signal transmission system, and a band identifying method, which treat a wavelength-multiplexed optical signal subjected to wavelength multiplexing.

BACKGROUND ART

In a wavelength-multiplexed optical signal treated in optical fiber communication, optical signals are orderly arranged according to a wavelength grid defined in an international telecommunication union telecommunication standardization sector (ITU-T) G.692 and are managed by channel numbers. General optical fiber communication, for example, is disclosed in Patent Literatures 1, 2 and the like.

However, in recent years, in optical fiber communication, an increase in a line demand is significant and higher-density multiplexing of optical signals is required. For example, it is proposed to perform large capacity transmission by multiplexing optical signals with high density to a limitation of frequency utilization efficiency by means of a multi-level modulation technology, a wavelength multiplexing technology, a spectrum control technology and the like.

In such high-density multiplexing transmission, with the development of a control technology of transmission waveforms of optical signals and a separation technology due to a digital computation of optical reception signals, a flexible grid, in which optical signals having mutually different bit rates and modulation schemes are transmitted with high density without depending on a wavelength grid, is introduced. Moreover, with the development of an optical wavelength control technology and an optical modulation technology, a multicarrier/super-channel technology, in which one line is transmitted through a plurality of spectrums is performed, is also applied.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In high-density multiplexing transmission employing the flexible grid, a wavelength band of an optical signal depends on a bit rate and differs in each wavelength. In other words, a plurality of optical signals constituting a wavelength-multiplexed optical signal have an unequal wavelength interval and are not arranged in a wavelength interval. In this case, since a border of a line is not clear, discrimination of a band occupied by one signal is difficult. Moreover, in high-density multiplexing transmission employing a multicarrier and a super channel, it is difficult to recognize a band occupied by one line on a spectrum.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a band identifying circuit, a wavelength-multiplexed optical signal transmission device, a wavelength-multiplexed optical signal transmission system, and a band identifying method, by which it is possible to identify occupied bands in a predetermined optical transmitter with high accuracy even when a plurality of optical signals constituting a wavelength-multiplexed optical signal are not arranged in equidistant wavelength intervals as a result of the application of a digital technology, a super channel and the like.

Solution to Problem

In order to achieve the above object, a band identifying circuit according to the present invention includes: an optical intensity control means for changing, by a prescribed level, an optical intensity of an optical signal outputted from a target-of-identification optical transmitter among a plurality of optical signals respectively outputted from a plurality of optical transmitters, constituting a wavelength-multiplexed optical signal, and having mutually different wavelengths; a spectrum acquisition means for measuring an optical intensity of each wavelength of the wavelength-multiplexed optical signal and outputting a result of the measurement as a spectrum; and a band identifying means for identifying a band occupied by the target-of-identification optical transmitter, based on a change amount of the outputted spectrum.

In order to achieve the above object, a wavelength-multiplexed optical signal transmission device according to the present invention includes: a plurality of optical transmitters for respectively outputting a plurality of optical signals having mutually different wavelengths; a multiplexing means for multiplexing the plurality of outputted optical signals and outputting a wavelength-multiplexed optical signal; and the aforementioned band identifying circuit for identifying the band occupied by the target-of-identification optical transmitter.

In order to achieve the above object, a wavelength-multiplexed optical signal transmission system according to the present invention includes: a wavelength-multiplexed optical signal transmission device including a plurality of optical transmitters for respectively outputting a plurality of optical signals having mutually different wavelengths, an optical intensity control means for changing, by a prescribed level, an optical intensity of an optical signal outputted from a target-of-identification optical transmitter among the plurality of outputted optical signals, and a multiplexing means for multiplexing the plurality of optical signals and outputting a wavelength-multiplexed optical signal; and a wavelength-multiplexed optical signal reception device including a reception means for receiving the transmitted wavelength-multiplexed optical signal, a spectrum acquisition means for measuring an optical intensity of each wavelength of the received wavelength-multiplexed optical signal and outputting a result of the measurement as a spectrum, and a band identifying means for acquiring a change amount of the outputted spectrum in synchronization with an operation of the optical intensity control means and identifying a band occupied by the target-of-identification optical transmitter, based on the acquired change amount of the spectrum.

In order to achieve the above object, a band identifying method according to the present invention includes: changing, by a prescribed level, an optical intensity of an optical signal outputted from a target-of-identification optical transmitter among a plurality of optical signals respectively outputted from a plurality of optical transmitters, constituting a wavelength-multiplexed optical signal, and having mutually different wavelengths; measuring an optical intensity of each wavelength of the wavelength-multiplexed optical signal and outputting a result of the measurement as a spectrum; and identifying a band occupied by the target-of-identification optical transmitter, based on a change amount of the outputted spectrum.

Advantageous Effects of Invention

According to the present invention, even when a plurality of optical signals constituting a wavelength-multiplexed optical signal are not arranged in equidistant wavelength intervals as a result of the application of a digital technology, a super channel and the like, it is possible to identify occupied bands in a predetermined optical transmitter with high accuracy.

EXAMPLE EMBODIMENT

First Example Embodiment

The first example embodiment of the present invention will be described. A block configuration diagram of a band identifying circuit according to the present example embodiment is illustrated inFIG. 1. InFIG. 1, a band identifying circuit10includes an optical intensity control means20, a spectrum acquisition means30, and a band identifying means40, and identifies a band occupied by a predetermined optical transmitter6kof n optical transmitters61,62. . .6n.

The optical intensity control means20changes, by a prescribed level, the optical intensity of an optical signal outputted from the target-of-identification optical transmitter6kamong optical signals respectively outputted from the plurality of optical transmitters61,62. . .6n. The optical signals respectively outputted from the plurality of optical transmitters61,62. . .6npass through the optical intensity control means20, are subjected to wavelength multiplexing, and then are outputted as a wavelength-multiplexed optical signal.

The spectrum acquisition means30receives a part of the wavelength-multiplexed optical signal obtained by wavelength-multiplexing the optical signals respectively outputted from the plurality of optical transmitters61,62. . .6n. The spectrum acquisition means30measures the optical intensity of each wavelength of the inputted wavelength-multiplexed optical signal and outputs a result of the measurement as a spectrum.

The band identifying means40identifies the band occupied by the target-of-identification optical transmitter6kbased on a change amount of the spectrum outputted from the spectrum acquisition means30.

Specifically, the optical intensity control means20according to the present example embodiment increases the optical intensity of the optical signal outputted from the target-of-identification optical transmitter6kby ΔP from a level when the optical intensity is not controlled. It is assumed that ΔP is a negligible quantity having no influence on optical signal demodulation. The band identifying means40computes a difference between the spectrum after the optical intensity is increased by ΔP and a spectrum (a spectrum before the optical intensity is increased by ΔP) when the optical intensity is not controlled, in synchronization with the operation of the optical intensity control means20. Then, the band identifying means40identifies a band, in which a result of the computation is ΔP, as the band occupied by the target-of-identification optical transmitter6k.

The band identifying means40and the optical intensity control means20operate by a common timing signal shared by signal lines indicated by dotted lines ofFIG. 1. A means for implementing the signal lines is arbitrary. It is preferable that a generation source of the timing signal is the band identifying means40performing measurement. That is, the optical intensity control means20changes the optical intensity of the optical signal by ΔP according to the timing signal, and the band identifying means40calculates a change amount with a spectrum acquired last time with reference to the same timing signal. Since it is possible to reliably acquire a spectrum after the optical intensity is changed by ΔP by sharing the timing signal, it is possible to accurately calculate a difference of ΔP.

After increasing the optical intensity of the optical signal outputted from the target-of-identification optical transmitter6kby ΔP, the optical intensity control means20can also decrease the optical intensity of the optical signal outputted from the target-of-identification optical transmitter6kby ΔP from a level when the optical intensity is not controlled. In this case, the band identifying means40computes a difference between a spectrum when the optical intensity is increased by ΔP and a spectrum when the optical intensity is decreased by ΔP. Then, the band identifying means40identifies a band, in which a result of the computation is ΔP×2, as the band occupied by the target-of-identification optical transmitter6k.

The band identifying circuit10configured as described above can identify an occupied band in the predetermined optical transmitter6kwith high accuracy even when a plurality of optical signals constituting a wavelength-multiplexed optical signal are not arranged in equidistant wavelength intervals as a result of the application of a digital technology, a super channel and the like.

The aforementioned band identifying circuit10can also be arranged in a wavelength-multiplexed optical signal transmission device. A block configuration diagram of the wavelength-multiplexed optical signal transmission device, in which the band identifying circuit10is arranged, is illustrated inFIG. 2. The wavelength-multiplexed optical signal transmission device50ofFIG. 2is configured by n optical transmitters61,62. . .6n, the aforementioned band identifying circuit10, and a multiplexing means70.

The optical transmitters61,62. . .6nrespectively output optical signals having mutually different wavelengths.

In the band identifying circuit10, the optical intensity control means20changes, by a prescribed level, the optical intensity of an optical signal outputted from the target-of-identification optical transmitter6kamong optical signals respectively outputted from the optical transmitters61,62. . .6n.

The multiplexing means70wavelength-multiplexes the optical signals outputted from the optical transmitters61,62. . .6nand passing through the optical intensity control means20, and outputs a wavelength-multiplexed optical signal.

In the band identifying circuit10, the spectrum acquisition means30measures the optical intensity of each wavelength of the wavelength-multiplexed optical signal outputted from the multiplexing means70and outputs a result of the measurement as a spectrum, and the band identifying means40identifies a band occupied by the target-of-identification optical transmitter6kbased on a change amount of the spectrum outputted from the spectrum acquisition means30.

In the aforementioned wavelength-multiplexed optical signal transmission device50, the band identifying circuit10is arranged in such a way that it is possible to identify occupied bands in the predetermined optical transmitter6kwith high accuracy even when a plurality of optical signals constituting a wavelength-multiplexed optical signal are not arranged in equidistant wavelength intervals as a result of the application of a digital technology, a super channel and the like.

Moreover, the functions of the band identifying circuit10ofFIG. 1can be provided to a wavelength-multiplexed optical signal transmission device and a wavelength-multiplexed optical signal reception device. In this case, a system configuration diagram of a wavelength-multiplexed optical signal transmission system is illustrated inFIG. 3. A wavelength-multiplexed optical signal transmission system80ofFIG. 3is configured by a wavelength-multiplexed optical signal transmission device50B and a wavelength-multiplexed optical signal reception device90.

The wavelength-multiplexed optical signal transmission device50B includes n optical transmitters61,62. . .6n, the optical intensity control means20, and the multiplexing means70. The wavelength-multiplexed optical signal transmission device50B changes, by a prescribed level, the optical intensity of an optical signal outputted from the target-of-identification optical transmitter6k, and transmits a wavelength-multiplexed optical signal obtained by wavelength-multiplexing a plurality of optical signals outputted from the optical transmitters61,62. . .6nin the multiplexing means70.

The wavelength-multiplexed optical signal reception device90includes a reception means91, the spectrum acquisition means and the band identifying means40. As the wavelength-multiplexed optical signal reception device90, for example, an undersea repeater can be applied. The wavelength-multiplexed optical signal reception device90receives the wavelength-multiplexed optical signal in the reception means91, and measures the optical intensity of each wavelength of the received wavelength-multiplexed optical signal and outputs a result of the measurement as a spectrum in the spectrum acquisition means30. The band identifying means40acquires a change amount of the spectrum in synchronization with the operation of the optical intensity control means20of the wavelength-multiplexed optical signal transmission device50B, and identifies a band occupied by the target-of-identification optical transmitter6kbased on the acquired change amount of the spectrum.

The synchronization of the operation of the band identifying means40and the operation of the optical intensity control means20inFIG. 3can be performed similarly to that ofFIG. 1.

Also in the wavelength-multiplexed optical signal transmission system80ofFIG. 3, even when a plurality of optical signals constituting a wavelength-multiplexed optical signal are not arranged in wavelength units at equidistant intervals as a result of the application of a digital technology, a super channel and the like, it is possible to identify occupied bands in the predetermined optical transmitter6kwith high accuracy.

Second Example Embodiment

The second example embodiment will be described. A block configuration diagram of a wavelength-multiplexed optical signal transmission device according to the present example embodiment is illustrated inFIG. 4. InFIG. 4, a wavelength-multiplexed optical signal transmission device100includes four first optical transmitters200A to200D, one second optical transmitter300, an optical signal level control circuit400, a wavelength multiplexing circuit500, a wavelength-multiplexed signal monitoring circuit600, and a monitoring circuit700. The wavelength-multiplexed optical signal transmission device100ofFIG. 4wavelength-multiplexes a plurality of optical signals outputted from the first optical transmitters200A to200D and the second optical transmitter300, and transmits one wavelength-multiplexed optical signal to a transmission path.

The first optical transmitters200A to200D respectively include optical transmission circuits210A to210D and variable loss circuits220A to220D, and generate and output an optical signal having a single wavelength. The first optical transmitter200A outputs an optical signal1ofFIG. 5, the first optical transmitter200B outputs an optical signal2ofFIG. 5, the first optical transmitter200C outputs an optical signal3ofFIG. 5, and the first optical transmitter200D outputs an optical signal5ofFIG. 5.

Each of the optical transmission circuits210A to210D generates the optical signal by coding an optical carrier.

The variable loss circuits220A to220D respectively adjust optical output levels of the optical signals inputted from the optical transmission circuits210A to210D, under the control of the optical signal level control circuit400. The optical signals having passed through the variable loss circuits220A to220D are outputted to the wavelength multiplexing circuit500.

The second optical transmitter300includes a multiple wavelength optical transmission circuit310and four variable loss circuits321to324, and generates and outputs an optical signal of one line including four subcarriers. The second optical transmitter300outputs optical signals4ofFIG. 5.

The multiple wavelength optical transmission circuit310generates four optical signals having mutually different wavelengths by coding four subcarriers having mutually different wavelengths, and outputs the generated optical signals to the variable loss circuits321to324. In the present example embodiment, an optical signal of one line is formed by the four optical signals outputted from the multiple wavelength optical transmission circuit310.

The variable loss circuits321to324respectively adjust optical output levels of the optical signals inputted from the multiple wavelength optical transmission circuit310, under the control of the optical signal level control circuit400. The optical signals having passed through the variable loss circuits321to324are outputted to the wavelength multiplexing circuit500.

The optical signal level control circuit400controls the specific variable loss circuits220A to220D of the first optical transmitters200A to200D and the specific variable loss circuits321to324of the second optical transmitter300based on a control signal inputted from the monitoring circuit700. The optical signal level control circuit400controls the specific variable loss circuits220A to220D and321to324based on the control signal, in such a way that optical signals, whose optical output levels are changed between ±ΔP, are outputted from the controlled variable loss circuits220A to220D and321to324.

The wavelength multiplexing circuit500wavelength-multiplexes the optical signal having a single wavelength and the optical signal of one line including four subcarriers outputted from the first optical transmitters200A to200D and the second optical transmitter300, thereby outputting a wavelength-multiplexed optical signal. The wavelength multiplexing circuit500according to the present example embodiment outputs the wavelength-multiplexed optical signal in which optical signals having mutually different bands are arranged close together in a wavelength direction and have a continuous optical spectrum.

An example of the spectrum of the wavelength-multiplexed optical signal outputted from the wavelength multiplexing circuit500illustrated inFIG. 5. In the wavelength-multiplexed optical signal illustrated inFIG. 5, wavelength intervals differ in each optical signal. This is because a bit rate and a modulation scheme differ in each optical signal and a wavelength band to be occupied differs in each optical signal. In the wavelength-multiplexed optical signal illustrated inFIG. 5, when a bandwidth of the optical signal2outputted from the first optical transmitter200B is set to 1 (a reference width), the optical signal1outputted from the first optical transmitter200A is ¼ of the band and the optical signals3and5outputted from the first optical transmitters200C and200D are ½ of the band. On the other hand, the optical signal4outputted from the second optical transmitter300is configured with subcarriers of four waves of the band equal to that of the optical signal2, but a wavelength interval is narrowed by densification and the band is nearly four times as wide as the optical signal2.

The wavelength-multiplexed optical signal ofFIG. 5outputted from the wavelength multiplexing circuit500is divided into two signals, wherein one wavelength-multiplexed optical signal is outputted to the wavelength-multiplexed signal monitoring circuit600, and the other wavelength-multiplexed optical signal is transmitted from the wavelength-multiplexed optical signal transmission device100to an exterior.

The wavelength-multiplexed signal monitoring circuit600measures an optical output level (a spectrum) of an optical signal of each wavelength in the full band of the inputted wavelength-multiplexed optical signal by the control signal inputted from the monitoring circuit700. The wavelength-multiplexed signal monitoring circuit600sweeps the wavelength of the wavelength-multiplexed optical signal, and outputs a spectrum of the wavelength-multiplexed optical signal obtained by the wavelength sweeping to the monitoring circuit700as a monitoring result.

The monitoring circuit700identifies bands occupied by the desired first optical transmitters200A to200D and second optical transmitter300. For example, when the monitoring circuit700identifies a band occupied by a first optical transmitter200k, the monitoring circuit700generates a control signal for controlling an optical output level of and optical signal outputted from the first optical transmitter200kand outputs the control signal to the optical signal level control circuit400. Then, the monitoring circuit700computes a change amount of the monitoring result inputted from the wavelength-multiplexed signal monitoring circuit600, thereby identifying the band occupied by the first optical transmitter200k. The monitoring circuit700according to the present example embodiment computes the change amount of the monitoring result in synchronization with the output of the control signal.

InFIG. 4, the monitoring circuit700generates a timing signal and hands over the timing signal to the variable loss circuits220A to220D of the first optical transmitters200A to200D and the variable loss circuits321to324of the second optical transmitter300via the optical signal level control circuit400. Since the timing signal corresponds to each optical transmitter, it is possible to control optical output of an arbitrary optical transmitter. The first optical transmitters200A to200D and the second optical transmitter300change the optical intensities of the optical signals1to5by ΔP by the optical signal level control circuit according to the timing signal. The monitoring circuit700receives the spectrum of the wavelength-multiplexed optical signal from the wavelength-multiplexed signal monitoring circuit600simultaneously to a change in the optical intensities. The spectrum is received according to the timing signal of the monitoring circuit700and is compared with a spectrum received last time in terms of optical intensity, in such a way that a band, in which a change of ΔP occurs, is identified. As a consequence, bands occupied by each optical transmitter are identified.

A procedure for identifying bands in the wavelength-multiplexed optical signal transmission device100will be described in detail with reference toFIG. 6andFIG. 7. Hereinafter, a description will be provided for a procedure when the wavelength-multiplexed optical signal transmission device100identifies a band occupied by the second optical transmitter300.

When the monitoring circuit700identifies bands occupied by the optical signals4outputted from the second optical transmitter300, the monitoring circuit700generates a control signal1for changing the optical output levels of the optical signals4outputted from the second optical transmitter300by +ΔP and outputs the control signal1to the optical signal level control circuit400(S101).

The optical signal level control circuit400controls the variable loss circuits321to324of the second optical transmitter300based on the inputted control signal1, and respectively changes the optical output levels of four optical signals outputted from the multiple wavelength optical transmission circuit310by +ΔP from optical output levels when the optical output levels are not controlled (S102). In this way, the optical output levels of the optical signals4outputted from the multiple wavelength optical transmission circuit310are changed by +ΔP. The optical signals4, whose optical output levels have changed by +ΔP, are wavelength-multiplexed with the optical signals1to3and5outputted from the optical transmission circuits210A to210D in the wavelength multiplexing circuit500, and are outputted as a wavelength-multiplexed optical signal.

The wavelength-multiplexed signal monitoring circuit600receives a part of the wavelength-multiplexed optical signal outputted from the wavelength multiplexing circuit500. That is, the wavelength-multiplexed signal monitoring circuit600receives the wavelength-multiplexed optical signal including the optical signals4whose optical output levels have changed by +ΔP. The wavelength-multiplexed signal monitoring circuit600acquires the full band spectrum of the inputted wavelength-multiplexed optical signal and outputs the spectrum to the monitoring circuit700as a first monitoring result. An example of the first monitoring result illustrated inFIG. 7 (a).

The monitoring circuit700stores the inputted first monitoring result (S103). After the first monitoring result is stored, the monitoring circuit700generates a control signal2for changing the optical output levels of the optical signals4outputted from the second optical transmitter300by −ΔP and outputs the control signal2to the optical signal level control circuit400(S104).

The optical signal level control circuit400controls the variable loss circuits321to324of the second optical transmitter300based on the inputted control signal2, and respectively changes the optical output levels of four optical signals outputted from the multiple wavelength optical transmission circuit310by −ΔP from optical output levels when the optical output levels are not controlled (S105). In this way, the optical output levels of the optical signals4outputted from the multiple wavelength optical transmission circuit310are changed by −ΔP. The optical signals4, whose optical output levels have changed by −ΔP, are wavelength-multiplexed with the optical signals1to3and5outputted from the optical transmission circuits210A to210D in the wavelength multiplexing circuit500, and are outputted as a wavelength-multiplexed optical signal.

The wavelength-multiplexed signal monitoring circuit600receives a part of the wavelength-multiplexed optical signal outputted from the wavelength multiplexing circuit500. That is, the wavelength-multiplexed signal monitoring circuit600receives the wavelength-multiplexed optical signal including the optical signals4whose optical output levels have changed by −ΔP. The wavelength-multiplexed signal monitoring circuit600acquires the overall band spectrum of the inputted wavelength-multiplexed optical signal and outputs the spectrum to the monitoring circuit700as a second monitoring result. An example of the second monitoring result illustrated inFIG. 7 (b).

The monitoring circuit700acquires the second monitoring result and computes a difference between the stored first monitoring result and the newly acquired second monitoring result (S106). The difference between the first monitoring result illustrated inFIG. 7 (a)and the second monitoring result illustrated inFIG. 7 (b)is illustrated inFIG. 7 (c).

As apparent fromFIG. 7 (c), when the optical output levels of the optical signals4outputted from the second optical transmitter300by +ΔP and −ΔP, and a difference between the spectrums at this time is computed, a difference among the optical output levels of the optical signals4is about ΔP×2. On the other hand, differences among the optical output levels of the optical signal1to3and5, for which the optical output levels is not controlled, are offset to one another and becomes nearly zero. Consequently, the monitoring circuit700according to the present example embodiment identifies a band, in which the difference between the spectrums is ΔP×2, as a band occupied by the optical signal4outputted from the second optical transmitter300(S107).

As described above, the wavelength-multiplexed optical signal transmission device100according to the present example embodiment controls the variable loss circuits220A to220D of the desired first optical transmitters200A to200D and the variable loss circuits321to324of the desired second optical transmitter300, thereby changing the optical output levels of the optical signals outputted from the desired first optical transmitters200A to200D and the desired second optical transmitter300by ±ΔP. Then, the wavelength-multiplexed optical signal transmission device100computes the difference between the first monitoring result when the optical output level has changed by +ΔP and the second monitoring result when the optical output level has changed by −ΔP, and identifies a band, in which the difference between the optical output levels is ΔP×2, as a band occupied by the optical signals outputted from the desired first optical transmitters200A to200D and the second optical transmitter300.

That is, the monitoring circuit700makes synchronization of the generation of the control signal and the acquisition of the monitoring result, changes, by ±ΔP, the optical output levels outputted from the first optical transmitters200A to200D and the second optical transmitter300(band measurement targets) at a timing before monitoring is started, and computes a difference between spectrums, in such a way that it is possible to easily and accurately identify bands occupied by the desired first optical transmitters200A to200D and the second optical transmitter300.

In the present example embodiment, a case where the wavelength-multiplexed optical signal transmission device100includes four first optical transmitters200A to200D and one second optical transmitter300has been described; however, the number of the first optical transmitters200A to200D and the number of the second optical transmitter300are not limited thereto. Furthermore, in the wavelength-multiplexed optical signal transmission device, it is also possible to arrange an optical transmitter that outputs an optical signal having a single wavelength, or only an optical transmitter that outputs an optical signal of one line including a plurality of subcarriers.

Moreover, in the present example embodiment, a difference between spectrums, when the optical output levels outputted from the first optical transmitters200A to200D and the second optical transmitter300(band measurement targets) are changed by ±ΔP, is computed; however, the present invention is not limited thereto. For example, after the optical output levels are changed to a plus side by ΔP, it is also possible to compute a difference between the spectrum illustrated inFIG. 7 (a)and the spectrum illustrated inFIG. 5in the state in which the optical output levels are not controlled. In this case, the monitoring circuit700identifies a band, in which the difference between the optical output levels is ΔP, as a band occupied by the optical signals outputted from the desired first optical transmitters200A to200D and the second optical transmitter300.

The present invention is not limited to the aforementioned example embodiments and design changes and the like in the range of not departing from the scope of the present disclosure are also included in the present invention.

Priority is claimed on Japanese Patent Application No. 2016-017632 filed on Feb. 2, 2016, the contents of which are incorporated herein by reference.

REFERENCE SIGNS LIST