JP2019071513A - Transmission apparatus and channel interval measurement method - Google Patents

Abstract

To provide a transmission apparatus and a channel interval measurement method that can easily measure a channel interval of an optical signal.SOLUTION: A transmission apparatus includes a receiving unit that receives an optical signal assigned to one of channels in wavelength units provided in a wavelength multiplexed optical signal, a detection unit that detects a spectrum centered on the channel of the optical signal, a calculation unit that calculates an average value of power in a frequency band of a predetermined width across a channel of the optical signal and the adjacent channel from the spectrum, a storage unit that stores a correspondence between the average value of the power and the center frequency interval of the channel of the optical signal and the adjacent channel, and an acquisition unit that acquires the center frequency interval corresponding to the average value of the power calculated by the calculation unit from the storage unit.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a transmission apparatus and a channel spacing measurement method.

  In wavelength multiplexing transmission, an optical signal allocated to each channel for each wavelength is wavelength multiplexed and transmitted. In recent years, channel spacing has become narrower along with the demand for higher density, so it is important in network management to detect and manage channel spacing.

  On the other hand, Patent Document 1 describes a method of estimating the channel spacing from the gap width between the channels of the spectrum of the optical signal (the size of the gap of the spectrum between adjacent channels). Further, Patent Document 2 describes a method of obtaining a channel spacing from the ratio of power at a frequency near the edge of a channel and power at a frequency shifted from the frequency to an adjacent channel by a predetermined amount.

US Patent Application Publication No. 2016/0226683 JP, 2016-10040, A

  According to the method of Patent Document 1, for example, a large amount of signal data (for example, 20000 symbols) is acquired, its spectrum is detected, and a spectrum correction process is required to improve estimation accuracy. Therefore, when this method is adopted, high-performance hardware capable of complex arithmetic processing is required. Further, even with the method of Patent Document 2, for example, calculation of the frequency of the edge of the channel requires complicated arithmetic processing.

  Therefore, the object of the present invention is to provide a transmission apparatus and a channel spacing measurement method capable of easily measuring the channel spacing of an optical signal.

  In one aspect, the transmission apparatus detects a spectrum centered on the channel of the optical signal, and a receiving unit that receives the optical signal assigned to one of the channels of the wavelength unit provided in the wavelength multiplexing optical signal. A detection unit; a calculation unit for calculating an average value of power in a frequency band of a predetermined width across the channel of the optical signal and the adjacent channel from the spectrum; an average value of the power; a channel of the optical signal; A storage unit stores the correspondence with the center frequency interval of the adjacent channel, and an acquisition unit acquires the center frequency interval corresponding to the average value of the power calculated by the calculation unit from the storage unit.

  In one aspect, the transmission apparatus detects a spectrum centered on the channel of the optical signal, and a receiving unit that receives the optical signal assigned to one of the channels of the wavelength unit provided in the wavelength multiplexing optical signal. A detection unit, an average value of power in a first frequency band of a predetermined width across the channel of the optical signal and the adjacent channel from the spectrum, and a second frequency band of a predetermined width different from the first frequency band A calculation unit for calculating a difference from the average value of power, a difference between average values of powers in the first frequency band and the second frequency band, and a center frequency interval of the channel of the optical signal and the adjacent channel And the storage unit storing the correspondence relationship between the central frequency intervals corresponding to the difference between the average value of each power of the first frequency band and the second frequency band calculated by the calculation unit. Having an acquisition unit that acquires from the parts.

  In one aspect, a transmission apparatus includes: a receiving unit that receives an optical signal assigned to one of channels of wavelength units provided in a wavelength multiplexing optical signal; and a frequency control unit that changes a center frequency of the optical signal. A detection unit for detecting a spectrum centered on the channel of the optical signal; and an average of power within a frequency band of a predetermined width across the channel of the optical signal and the adjacent channel with respect to the center frequency of the optical signal from the spectrum. Calculation unit for calculating a rate of change of a value, a storage unit for storing a correspondence between the rate of change, and a center frequency interval of a channel of the optical signal and the adjacent channel, and the rate of change calculated by the calculator And an acquisition unit for acquiring the corresponding center frequency interval from the storage unit.

  In one aspect, the channel spacing measurement method receives an optical signal assigned to one of channels of wavelength units provided in a wavelength-multiplexed optical signal, and detects a spectrum centered on the channel of the optical signal, From the spectrum, an average value of power in a frequency band of a predetermined width across the channel of the optical signal and the adjacent channel is calculated, and the average value of the power and the center frequency interval of the channel of the optical signal and the adjacent channel The center frequency interval corresponding to the calculated average value of the power is acquired from the table in which the correspondence relationship of.

  In one aspect, the channel spacing measurement method receives an optical signal assigned to one of channels of wavelength units provided in a wavelength-multiplexed optical signal, and detects a spectrum centered on the channel of the optical signal, From the spectrum, an average value of power in a first frequency band of a predetermined width across the channel of the optical signal and the adjacent channel, and an average value of power in a second frequency band of a predetermined width different from the first frequency band And the corresponding relationship between the difference between the average value of each power in the first frequency band and the second frequency band, and the center frequency interval of the channel of the optical signal and the adjacent channel is registered. The center frequency interval corresponding to the difference between the calculated average values of the first frequency band and the second frequency band is obtained from the table.

  In one aspect, an optical signal assigned to one of channels of wavelength units provided in a wavelength-multiplexed optical signal is received, a center frequency of the optical signal is changed, and a spectrum centered on the channel of the optical signal is received. The rate of change of the average value of the power within a frequency band of a predetermined width across the channel of the optical signal and the adjacent channel with respect to the center frequency of the optical signal is calculated from the spectrum; The center frequency interval corresponding to the calculated rate of change is obtained from a table in which the correspondence relationship between the channel of the optical signal and the center frequency interval of the adjacent channel is registered.

  In one aspect, the channel spacing of the optical signal can be easily measured.

It is a block diagram which shows an example of a transmission system. It is a block diagram which shows an example of a transmitter-receiver. It is a block diagram which shows the channel space | interval measurement part in 1st Example. It is a figure which shows an example of a channel space | interval measuring method. It is a figure which shows an example of a channel space | interval table. It is a figure which shows an example of spectrum narrowing. It is a figure which shows an example of the production | generation method of a channel space | interval table. It is a flow chart which shows an example of a channel interval measuring method. It is a flow chart which shows an example of output processing of an alarm. It is a figure which shows an example of adjustment of a gap area | region. It is a figure which shows an example of an index value in case the gap area | region is fixed. It is a figure which shows an example of an index value in case a gap area | region is variable. It is a block diagram which shows the channel space | interval measurement part in 2nd Example. It is a figure which shows an example of the channel spacing measurement method which considered the influence of ASE (Amplified Spontaneous Emission). It is a figure which shows the example of a channel space | interval table. It is a figure which shows an example of the channel spacing measurement method using the power average value of each gap area | region of high frequency side and low frequency side. It is a figure which shows an example of the determination method of the initial value of the center frequency of each gap area | region of the high frequency side and the low frequency side. It is a block diagram which shows the channel space | interval measurement part in 3rd Example. It is a figure which shows an example of the channel spacing measurement method using the change rate of the power average value with respect to the center frequency of an optical signal. It is a figure which shows an example of a change of the power average value of the gap area | region with respect to channel spacing. It is a figure which shows an example of a channel space | interval table. It is a flow chart which shows an example of a channel interval measuring method. It is a figure which shows the analysis result of the channel space | interval by a comparative example. It is a figure which shows the analysis result of the channel space | interval by an Example. It is a figure which shows an example of the effect of the channel space | interval measurement which used the power average value.

  FIG. 1 is a block diagram showing an example of a transmission system. The transmission system includes nodes Na and Nb provided with a plurality of transceivers 1 and ROADMs (Reconfigurable Optical Add / Drop Multiplexers), and a Software Defined Network (SDN) controller 3.

  The ROADMs 2 of the nodes Na and Nb mutually transmit and receive the wavelength-multiplexed optical signal Smux. The wavelength-multiplexed optical signal Smux is provided with channels in units of wavelengths, and the optical signals S assigned to the respective channels are wavelength-multiplexed. The wavelength-multiplexed optical signal Smux transmitted from the ROADM 2 of the node Na is transmitted through the optical fiber 90, which is a transmission path, and is received by the ROADM 2 of the node Nb. The wavelength-multiplexed optical signal Smux transmitted from the ROADM 2 of the node Nb is transmitted through the optical fiber 91, which is a transmission path, and received by the ROADM 2 of the node Na.

  The transmitter / receiver 1 is an example of a transmission apparatus, and transmits / receives an optical signal assigned to one of the channels according to, for example, a digital coherent optical transmission system. The optical signal S transmitted from the transmitter / receiver 1 is input to the ROADM 2 and wavelength-multiplexed into the wavelength-multiplexed optical signal Smux.

  The ROADM 2 is provided with, for example, a wavelength selective switch (WSS) 20 for wavelength multiplexing the optical signal S. The wavelength selective switch 20 includes a filter having a passband corresponding to each channel.

  Further, the ROADM 2 is provided with an optical splitter 21 for branching the wavelength-multiplexed optical signal Smux input from the opposing nodes Na and Nb toward each of the transceivers 1. Each transceiver 1 receives an optical signal S corresponding to a predetermined channel from the wavelength multiplexed optical signal Smux.

  Further, the ROADM 2 is provided with optical amplifiers 22 and 23 for amplifying the wavelength multiplexed optical signal Smux. The optical amplifiers 22 and 23 are made of, for example, an erbium-doped fiber or the like. The optical amplifier 22 amplifies the wavelength multiplexing optical signal Smux output from the wavelength selective switch 20 to the optical fibers 90 and 91, and the optical amplifier 23 amplifies the wavelength multiplexing optical signal input from the optical fibers 90 and 91 to the optical splitter 21. Amplify Smux.

  The SDN controller 3 monitors and controls the nodes Na and Nb based on the technology of SDN. The SDN controller 3 manages the channel of the optical signal S, and sets the wavelength of the optical signal S of the corresponding channel in the transmitter / receiver 1 and the wavelength selective switch 20. The SDN controller 3 also receives an alarm output from the transmitter / receiver 1 and notifies, for example, the operator.

  FIG. 2 is a block diagram showing an example of the transmitter / receiver 1. The transmitter / receiver 1 includes a transmitter 1a that transmits an optical signal S, a receiver 1b that receives an optical signal S, and a controller 1c that controls the transmitter 1a and the receiver 1b. Although FIG. 2 shows only the configuration of a pair of transmitting unit 1a and receiving unit 1b for transmitting and receiving optical signal S, the other transmitting unit 1a and receiving unit 1b have the same configuration as this. .

  The transmission unit 1 a includes a transmission processing circuit 110, DACs (Digital-to-Analog Converters) 111 and 112, amplifiers 113 and 114, a laser diode (LD: Laser Diode) 115, and an optical modulator 116. The transmission processing circuit 110 is configured by, for example, a DSP (Digital Signal Processor), but is not limited to this. The transmission processing circuit 110 may be configured by an FPGA (Field Programmable Gate Array) or a CPU (Central Processing Unit) circuit.

  The transmission processing circuit 110 converts the data signal Dt input from, for example, a LAN (Local Area Network) into each symbol of the in-phase component and the quadrature-phase component of the data signal Dt according to a predetermined modulation scheme such as QAM (Quadrature Amplitude Modulation). Map In addition, as a format of the data signal Dt, although an Ethernet (registered trademark) frame is mentioned, it is not limited to this.

  The transmission processing circuit 110 outputs the in-phase component and the quadrature-phase component of the data signal Dt to the DACs 111 and 112, respectively. In addition to the mapping process, the transmission process circuit 110 may perform a process of generating a forward error correction (FEC) code for error correction of the data signal Dt.

  The DACs 111 and 112 convert the data signal Dt from a digital signal to an analog signal and output the converted signal to the amplifiers 113 and 114, respectively. The amplifiers 113 and 114 amplify analog signals and input them to the optical modulator 116. The optical modulator 116 is configured by, for example, a Mach-Zehnder modulator (MZM: Mach-Zehnder Modulator).

  The laser diode 115 generates transmission light and outputs it to the light modulator 116. The optical modulator 116 generates and transmits an optical signal S by optically modulating transmission light based on the in-phase component and the quadrature-phase component of the data signal Dt. The optical signal S is input from the ROADM 2 to the opposing nodes Na and Nb via the optical fiber, branched by the ROADM 2, and received by the receiver 1 b of the corresponding transceiver 1.

  The receiver 1 b includes a coherent receiver 100, ADCs (analog-to-digital converters) 101 and 102, a reception processing circuit 103, and a laser diode (LD) 104. The coherent receiver 100 is called a reception light front end or the like, and receives an optical signal S assigned to one of the channels provided in the wavelength multiplexing optical signal Smux as an example of a reception unit.

  Local emission is input from the laser diode 104 to the coherent receiver 100. The coherent receiver 100 receives the optical signal S of the corresponding channel from the wavelength multiplexed optical signal Smux based on the central frequency of the local light. More specifically, the coherent receiver 100 acquires, from the wavelength multiplexed light signal Smux, signal components within a predetermined frequency range with reference to the center frequency of the light signal S. The coherent receiver 100 converts a signal component into an electrical signal, separates the signal component into an in-phase component and a quadrature-phase component, and outputs them to the ADCs 101 and 102, respectively.

  The ADCs 101 and 102 convert the in-phase component and the quadrature-phase component of the data signal Dt from an analog signal to a digital signal, respectively, and output the converted signal to the reception processing circuit 103. The reception processing circuit 103 is configured by, for example, a DSP, but is not limited to this, and may be configured by an FPGA or a CPU circuit.

  The reception processing circuit 103 restores the original data signal Dt by demapping the symbols of the in-phase component and the quadrature phase component, and outputs the signal to, for example, the LAN. The reception processing circuit 103 performs processing other than demapping processing, for example, processing for compensating wavelength dispersion and nonlinear optical effects in the optical fibers 90 and 91, and processing for correcting data errors based on FEC.

  Further, the reception processing circuit 103 is provided with a channel interval measurement unit 4. The channel spacing measurement unit 4 detects a spectrum centered on the channel of the optical signal to be received, and based on the spectrum, the center frequency spacing between the channel and the adjacent channel (hereinafter referred to as "channel spacing") Measure The configuration of the channel interval measurement unit 4 will be described later.

  The control unit 1 c includes, for example, a CPU circuit and controls the transmission unit 1 a and the reception unit 1 b. The controller 1 c controls the center frequency of the optical signal S by setting, for example, the center frequency of the transmission light of the laser diode 115 and the center frequency of the local light emission of the laser diode 104. Further, the control unit 1 c performs various controls on the processing of the light signal S (data signal Dt) with respect to the transmission processing circuit 110 and the reception processing circuit 103. The control unit 1 c communicates with, for example, the SDN controller 3 and performs control in accordance with an instruction of the SDN controller 3.

  Next, the channel interval measurement unit 4 will be described.

(First embodiment)
FIG. 3 is a block diagram showing the channel interval measurement unit 4 in the first embodiment. The channel interval measurement unit 4 includes a capture processing unit 40, an FFT (Fast Fourier Transform) unit 41, a spectrum data storage unit 42, an index value calculation unit 43, a channel interval acquisition unit 44, and a table storage unit 45. And a table generation unit 46.

  The capture processing unit 40 captures the data signal Dt, for example, at a constant cycle, under the control of the control unit 1c, for example. The capture processing unit 40 outputs the data of the captured data signal Dt to the FFT unit 41.

  The FFT unit 41 is an example of a detection unit, and detects a frequency spectrum centered on the channel of the optical signal S received by the coherent receiver 100 (hereinafter referred to as “spectrum”). More specifically, the FFT unit 41 converts data of the data signal Dt from data in the time domain into data in the frequency domain, that is, spectrum data, by fast Fourier transform (FFT). The FFT unit 41 stores spectrum data in the spectrum data storage unit 42.

  The spectrum data storage unit 42 is configured of, for example, a memory area of a DSP, but is not limited to this, and may be configured of a memory or the like different from the DSP. The spectrum data storage unit 42 stores the spectrum data written from the FFT unit 41. The spectrum data is read by the index value calculation unit 43.

  The index value calculation unit 43 is an example of a calculation unit, and from the spectrum detected by the FFT unit 41, an average value of power within a frequency band of a predetermined width across the channel of the optical signal S and its adjacent channel (hereinafter referred to as “power Calculate “average value”. The index value calculation unit 43 calculates the power average value as an index value indicating the channel interval, and outputs the power average value to the channel interval acquisition unit 44.

  The table storage unit 45 is an example of a storage unit, and stores correspondences between index values and channel intervals. More specifically, the table storage unit 45 stores a channel interval table 450 in which the index value and the channel interval are associated with each other and registered. The table storage unit 45 includes, for example, a memory area of the DSP, but is not limited to this. The table storage unit 45 may be configured by a memory other than the DSP.

  The table generation unit 46 generates the channel interval table 450 prior to the measurement of the channel interval, for example, according to the instruction of the control unit 1c. At this time, the control unit 1 c changes the channel interval by changing the center frequency of the optical signal S at, for example, a predetermined interval, and the table generation unit 46 acquires an index value for each channel interval from the index value calculation unit 43 The channel interval table 450 is generated according to

  The channel interval acquisition unit 44 is an example of an acquisition unit, and acquires from the table storage unit 45 a channel interval corresponding to the index value calculated by the index value calculation unit 43. More specifically, the channel interval acquisition unit 44 acquires the channel interval corresponding to the index value by referring to the channel interval table 450. The channel interval acquisition unit 44 notifies the control unit 1 c of the channel interval acquired from the channel interval table 450.

  FIG. 4 is a diagram showing an example of a channel spacing measurement method. In FIG. 4, the horizontal axis indicates frequency (GHz) and the vertical axis indicates power (mW). The symbol Ro indicates the range of the spectrum detected by the FFT unit 41 (hereinafter referred to as “detection range”). The detection range Ro includes one end of adjacent channels # (n + 1) and # (n-1) on both sides of the corresponding channel #n (n: positive integer).

  The symbol Sn indicates the spectrum of the optical signal S of the corresponding channel. The code Sn + 1 indicates the spectrum of the optical signal S of the adjacent channel # (n + 1) on the high frequency side (that is, the short wavelength side), and the code Sn-1 indicates the adjacent channel # on the low frequency side (that is, the long wavelength side). The spectrum of the optical signal S of (n-1) is shown. In addition, the part shown with a dashed-dotted line among spectrum Sn + 1, Sn-1 is a part out of the detection range Ro.

  In this example, the interval between the central frequency fc of the optical signal S of the channel #n and the central frequency fc 'of the optical signal S of the adjacent channel # (n + 1) on the high frequency side is the channel interval L to be measured. However, even when the distance between the center frequency fc of the optical signal S of the channel #n and the center frequency of the optical signal S of the adjacent channel # (n-1) on the low frequency side is Similar measurement methods are used.

  The index value calculation unit 43 calculates the average value of the power within the frequency band of a predetermined width W1 (hereinafter referred to as “gap region”) A1 covering the channel #n and the adjacent channel # (n + 1). More specifically, the gap area A1 is an area including one end of the frequency band of the channel #n and one end of the frequency band of the adjacent channel # (n + 1). Thus, the gap region A1 includes the spectrum Sn of the channel #n and the spectrum Sn + 1 of the adjacent channel # (n + 1). The center frequency f1 and the width W1 of the gap area A1 are set in advance to appropriate values.

  For example, when the adjacent channel # (n + 1) approaches the channel #n as shown by the code d, that is, when the channel spacing L is narrowed, the spectrum Sn + 1 in the gap region A1 is represented by the code S ′. As shown, the power changes in the increasing direction. Therefore, the power average value P1 of the gap area A1 increases.

  Also, contrary to the above case, when the adjacent channel # (n + 1) is separated from the channel #n, that is, when the channel spacing L becomes wide, the power of the spectrum Sn + 1 in the gap region A1 decreases. Change in the direction. Therefore, the power average value P1 of the gap region A1 decreases.

  Therefore, the channel interval measurement unit 4 can measure the channel interval L by calculating the power average value P1 as an index value by the index value calculation unit 43. For example, the index value calculation unit 43 detects the power in the gap area A1 at constant intervals, and divides the sum of the powers by the number of detections or the width W1 to calculate the power average value P1. Further, the channel interval acquisition unit 44 acquires, from the channel interval table 450, the channel interval L corresponding to the power average value (index value) P1.

  FIG. 5 is a diagram showing an example of the channel interval table 450. As shown in FIG. In the channel interval table 450, the power average value P1 of index values and the channel interval L (GHz) are registered in association with each other. The channel interval table 450 is an example of a table.

  For example, when the index value is 0.30, the channel interval acquisition unit 44 acquires 35.0 (GHz) as the channel interval L, and when the index value is 0.24, the channel interval L is 36.5 as the channel interval L. Get (GHz). The channel interval acquisition unit 44 notifies the control unit 1 c of the acquired channel interval L.

  Further, when the power average value, which is the index value calculated by the index value calculation unit 43, is not registered in the channel interval table 450, the channel interval acquisition unit 44 selects the channel interval L from the value closer to the calculated power average value P1. To get The channel interval acquisition unit 44 acquires, for example, 35.0 (GHz) as the channel interval L when the power average value P1 is 0.31.

  Thus, the channel interval acquisition unit 44 can easily acquire the channel interval L from the channel interval table 450 based on the power average value P1, which is the index value calculated by the index value calculation unit 43.

  Further, since the index value calculation unit 43 calculates the power average value P1 in the gap region A1, even if there is an error in each power, the influence of the error can be reduced by averaging. For this reason, the index value calculation unit 43 does not have to perform, for example, correction processing of the spectra Sn-1, Sn, and Sn + 1. Furthermore, since the gap area A1 is a frequency band of a predetermined width W1 covering the channel #n and the adjacent channel # (n + 1), the index value calculation unit 43 needs to perform complicated calculation to specify the gap area A1. Nor.

  Therefore, the transmitter / receiver 1 can easily measure the channel spacing L of the optical signal S. Further, the control unit 1 c can control the center frequency fc of the optical signal S of the channel #n based on the channel interval L.

  For example, as shown by a symbol d in FIG. 4, when the controller 1 c determines that the adjacent channel # (n + 1) is approaching the channel #n from the channel interval L, an optical signal of the channel #n The channel spacing L can be increased by changing the center frequency fc of S in the direction indicated by the symbol d ′. At this time, the control unit 1c controls the central frequency of the local light emission to the laser diode 104 of the receiving unit 1b, and further transmits the transmitted light to the laser diode 115 of the transmitting unit 1a of the opposing nodes Na and Nb. Control the center frequency. The controller 1 c may transmit an instruction for frequency control to the opposing nodes Na and Nb via the SDN controller 3 or alternatively, the frequency control signal may be wavelength-multiplexed into the wavelength multiplexing optical signal Smux to obtain an optical fiber 90. , 91 may be transmitted.

  Referring again to FIG. 5, in the channel interval table 450, the channel interval L corresponding to the index value of 0.10 or less is registered as, for example, “N / A”. This is because, when the index value is abnormally small, it is estimated that there is an abnormality in the spectrum Sn of the channel #n. As abnormality of spectrum Sn, narrowing (PBN: Pass Band Narrowing) of spectrum Sn is mentioned, for example.

  FIG. 6 is a diagram showing an example of spectrum narrowing. 6, the same reference numerals are given to the same components as those in FIG. 4, and the description thereof will be omitted.

  As described above, the ROADM 2 is provided with the wavelength selective switch 20 having the passband. For example, in the transmission system of FIG. 1, when a plurality of ROADMs 2 for relaying the wavelength-multiplexed optical signal Smux are provided between the nodes Na and Nb, accumulation of the passbands of the plurality of wavelength selective switches 20 results in The edge is scraped off.

  The code Rp indicates the cumulative passband Rp of the plurality of wavelength selective switches 20. If the passband Rp is sufficiently wide with respect to the width of the spectrum Sn, the spectrum Sn is not scraped, but as shown by the code D, when the passband Rp narrows, the end of the spectrum Sn (hatched portion Reference is removed to narrow the spectrum Sn. As a result, the quality of the optical signal S of the channel #n is degraded.

  When the spectrum Sn is narrowed, the power in the gap region A1 decreases, and the power average value P1, which is an index value, decreases. Therefore, if “N / A” is registered in the channel interval table 450 as the channel interval L corresponding to the index value equal to or less than the predetermined threshold (0.1 in this example), the channel interval acquisition unit 44 “N / A” can be determined as the abnormal channel interval L and notified to the control unit 1 c.

  Note that the above threshold is determined based on, for example, an index value when the spectrum Sn + 1 of the adjacent channel # (n + 1) does not exist. This is because, if there is a spectrum Sn + 1 of the adjacent channel # (n + 1), the power in the gap region A1 includes the power of the optical signal S of the channel #n and the power of the optical signal S of the adjacent channel # (n + 1) This is because it is difficult to determine the narrowing of the spectrum Sn with high accuracy. Therefore, it is desirable that the channel spacing acquisition unit 44 determine “N / A” as the abnormal channel spacing L when the spectrum Sn + 1 of the adjacent channel # (n + 1) does not exist.

  When the channel interval acquisition unit 44 acquires “N / A” from the channel interval table 450, the channel interval acquisition unit 44 notifies the control unit 1c of the abnormality of the channel interval L. At this time, the control unit 1 c determines that the spectrum Sn is narrowed, and outputs an alarm to the SDN controller 3. That is, when the channel interval L acquired by the channel interval acquisition unit 44 is equal to or less than a predetermined threshold, the control unit 1 c outputs an alarm. Thereby, the SDN controller 3 can detect the narrowing of the spectrum Sn. The control unit 1 c is an example of an alarm output unit.

  Also, prior to measurement of the channel spacing L, the channel spacing table 450 is generated, for example, by the following generation method.

  FIG. 7 is a diagram showing an example of a method of generating the channel interval table 450. As shown in FIG. In FIG. 7, the same reference numerals are given to the same components as those in FIG.

  The controller 1 c sweeps the center frequency fc of the optical signal S of the channel #n in accordance with, for example, an instruction of the SDN controller 3. At this time, the control unit 1 c changes the channel interval L by changing the central frequency fc in the direction of the code M at constant intervals, for example, and notifies the table generation unit 46 of the channel interval L each time it changes. The control method of the center frequency fc is as described above.

  The table generation unit 46 instructs the index value calculation unit 43 to calculate an index value for each channel interval L. The table generation unit 46 registers the combination of the channel interval L and the index value in the channel interval table 450. Thus, the table generation unit 46 can easily generate the channel interval table 450.

  FIG. 8 is a flowchart showing an example of a channel spacing measurement method. The coherent receiver 100 receives the optical signal S of the channel #n from the opposite nodes Na and Nb (step St1). Next, the capture processing unit 40 captures data of the data signal Dt obtained from the light signal S (step St2). Next, the FFT unit 41 detects a spectrum centered on the channel #n from the data of the data signal Dt (step St3).

  Next, the index value calculation unit 43 calculates, as an index value, the power average value P1 in the gap area A1 across the channel #n of the optical signal and the adjacent channel # (n + 1) (step St4). Next, the channel interval acquisition unit 44 acquires the channel interval L corresponding to the calculated index value from the table in which the correspondence between the index value and the channel interval L is registered (step St5).

  Next, the channel interval acquisition unit 44 notifies the acquired channel interval L to the control unit 1c (Step St6). In this way, the channel spacing measurement method is implemented.

  FIG. 9 is a flowchart showing an example of alarm output processing. The control unit 1c determines the presence or absence of the notification of the channel interval L from the channel interval acquisition unit 44 (step St11). Control part 1c ends processing, when there is no notice (Step St11, No).

  When the control unit 1c receives the notification (Yes in step St11), the control unit 1c determines whether the channel interval L is abnormal based on the notification (step St12). If the channel interval L is normal (No in step St12), the control unit 1c ends the process.

  When the channel interval L is abnormal (Yes in step St12), the control unit 1c outputs an alarm to the SDN controller 3 (step St13). In this way, the alarm output process is performed.

  In this example, the position of the gap area A1 is a fixed value, but as described below, the frequency at which the power is minimum in the gap area A1 is the center frequency, in order to measure the channel spacing L more accurately. It may be adjusted to be

  FIG. 10 is a diagram showing an example of adjustment of the gap area A1. In FIG. 10, the same components as in FIG. 4 will be assigned the same reference numerals and descriptions thereof will be omitted.

  In this example, the index value calculation unit 43 determines the frequency f1 'at which the position of the gap area A1 is minimum in the gap area A1 according to the change of the spectrum Sn + 1 of the adjacent channel # (n + 1) indicated by the code S'. Adjust to be at the center. Here, gap area A1 of a dotted line frame shows gap area A1 before adjustment, and gap area A1 of a solid line frame shows gap area A1 after adjustment. In the present example, the position of the gap area A1 is adjusted to move to the low frequency side, but may be adjusted to move to the high frequency side.

  More specifically, the index value calculation unit 43 detects the position P 'of the minimum power in the gap area A1 before adjusting the position of the gap area A1. At this time, since the position P 'of the minimum power coincides with the position of the initial center frequency f1, the index value calculation unit 43 does not adjust the position of the gap area A1.

  Thereafter, as shown by the code S ', when the spectrum Sn + 1 of the adjacent channel # (n + 1) changes, the position P of the minimum power in the gap area A1 deviates from the position of the initial center frequency f1. Therefore, the index value calculation unit 43 adjusts the center frequency of the gap area A1 to a frequency f1 'that matches the position P of the minimum power so as to follow the position P of the minimum power. Thereby, gap area A1 is adjusted to the range of width W1 which makes center frequency frequency f1 'used as the minimum power.

  As described above, since the index value calculation unit 43 adjusts the position of the gap area A1 so that the frequency f1 ′ at which the power is minimum in the gap area A1 is at the center, the position of the gap area A1 is fixed. The accuracy of the measurement of the channel spacing L is improved compared to the case of

  FIG. 11 is a diagram showing an example of the index value when the gap area A1 is fixed. FIG. 11 shows an example of a graph of the spectra Sn and Sn + 1 in the case where the channel spacing L is 35.0 (GHz) to 37.5 (GHz), and the same graph is shown in the upper part and the lower part of the paper. Is described.

  In the graph at the upper part of the drawing, the magnitude of the power average P1 is indicated by the length of the dotted line frame as an index value in the case of channel spacing L = 37.5 (GHz). The magnitude of the power average value P1 is indicated by the length of the dotted line frame as an index value in the case of the interval L = 35.0 (GHz). Further, in this example, it is assumed that the center frequency f1 of the gap area A1 is fixed at 22.0 (GHz).

  Since the index value in the case of channel spacing L = 37.5 (GHz) has a large difference from the index value in the case of other channel spacing L, the channel spacing L = 37.5 (GHz) is highly accurate. It is measured. However, the index value in the case of the channel spacing L = 35.0 (GHz) is, for example, different from the index value in the case of the channel spacing L = 35.5 (GHz), the channel spacing L = 35.0, 35 The measurement accuracy of .5 (GHz) is low.

  FIG. 12 is a diagram showing an example of the index value when the gap area A1 is variable. The same graph as FIG. 11 is described in the upper part and lower part of the paper surface of FIG.

  In the graph at the top of the drawing, the magnitude of the power average value P1 is indicated by the length of the dotted line frame as an index value in the case of the channel spacing L = 37.5 (GHz). Here, as an example, the center frequency f1 of the gap region A1 is adjusted to about 19.6 (GHz) (= f1 ') at which the power is minimum.

  The index value in the case of the channel spacing L = 37.5 (GHz) has a large difference from the index value in the case of the other channel spacing L as described above, so the channel spacing L = 37.5 (GHz ) Is measured with high accuracy.

  Further, in the graph at the lower part of the drawing, the magnitude of the power average value P1 is indicated by the length of the dotted line frame as an index value in the case of channel spacing L = 35.0 (GHz). Here, the center frequency f1 of the gap region A1 is adjusted to, for example, about 17.5 (GHz) (= f1 ') at which the power is minimum.

  The index value in the case of channel spacing L = 35.0 (GHz) is, for example, the difference from the index value in the case of channel spacing L = 35.5 (GHz) is greater than the index value shown in FIG. The measurement accuracy of the interval L = 35.0, 35.5 (GHz) is improved.

  As described above, the accuracy of measurement of the channel spacing L is improved when the position of the gap area A1 is variable as compared with the case where the position of the gap area A1 is fixed.

Second Embodiment
FIG. 13 is a block diagram showing the channel interval measurement unit 4 in the second embodiment. In FIG. 13, the same components as in FIG. 3 will be assigned the same reference numerals and descriptions thereof will be omitted.

  The channel interval measurement unit 4 includes a capture processing unit 40, an FFT unit 41, a spectrum data storage unit 42, an index value calculation unit 43a, a channel interval acquisition unit 44a, a table storage unit 45, and a table generation unit 46. , Channel position determination unit 48. The table storage unit 45 also stores a channel interval table 450a.

  In the present embodiment, the index value calculation unit 43a calculates an index value different from that of the first embodiment in order to reduce the influence of ASE generated by the optical amplifier 22. The index value calculation unit 43a determines, from the spectrum, the power average value P1 in the gap region A1 and the power average value P0 in a frequency band of a predetermined width different from the gap region A1 (hereinafter referred to as “reference region”). The difference is calculated as an index value (P1-P2).

  In the channel interval table 450a, the correspondence between the difference (index value (P1-P0)) between the power average value P1 in the gap area A1 and the power average value P2 in the reference area and the channel interval L is registered. There is. The channel interval acquisition unit 44a acquires, from the channel interval table 450, the channel interval L corresponding to the index value (P1-P0) calculated by the index value calculation unit 43a. This reduces the effect of ASE in the measurement of channel spacing L, as described below.

  FIG. 14 is a diagram showing an example of a channel spacing measurement method in which the influence of ASE is taken into consideration. In FIG. 14, the same components as in FIG. 4 will be assigned the same reference numerals and descriptions thereof will be omitted.

  The spectra Sn-1, Sn, and Sn + 1 of this example include the power Pase of ASE light, which is a noise component. Therefore, the index value calculation unit 43a calculates not only the power average value P1 of the gap area A1 but also the power average value P0 of the reference area A0 different from the gap area A1, and the difference ΔPu (= P1−P0) By calculating, the powers P0ase and P1ase of the ASE included in the respective power average values P0 and P1 are offset.

P0 = P0 '+ P0ase (1)
P1 = P1 '+ P1ase (2)

  The power average value P0 of the reference area A0 is the sum of the power average value P0 'of the optical signal S and the power average value P0ase of the ASE light, as shown in the above equation (1). Further, the power average value P1 of the gap region A1 is the sum of the power average value P1 'of the optical signal S and the power average value P1ase of the ASE light, as shown by the above-mentioned equation (2). Further, the powers P0ase and P1ase of each ASE in the reference area A0 and the gap area A1 are the same (P0ase = P1ase = Pase).

  Therefore, the difference ΔPu between the power average values P0 and P1 becomes the difference (P1′−P0 ′) between the power average values P0 ′ and P1 ′ of the optical signal S, and becomes a value independent of the ASE powers P0ase and P1ase . Therefore, the index value calculation unit 43a can reduce the influence of the ASE by calculating the difference ΔPu as the index value. In addition, although difference (DELTA) Pu which is an index value of this example is set to P1-P0, you may be P0-P1.

  The reference area A0 is set, for example, in an area of a predetermined width W0 including the center frequency fc of the optical signal S of the channel #n. Here, the center frequency of the reference area A0 matches the center frequency fc of the optical signal S, but may not match. The position of the reference area A0 is not limited as long as the power average value P0 therein is a stable value with little fluctuation. Further, the width W0 of the reference area A0 may be the same as or different from the width W1 of the gap area A1. The gap area A1 is an example of a first frequency band, and the reference area A0 is an example of a second frequency band.

  The symbol Ga in FIG. 15 indicates the channel interval table 450a of this example. In the channel interval table 450a, the correspondence between the index value difference ΔPu and the channel interval L is registered. The channel interval acquisition unit 44a acquires the channel interval L = 35.0 (GHz) from the channel interval table 450a, for example, when the difference ΔPu = -9.70 which is the index value. The channel interval table 450a is an example of a table.

  As described above, since the difference ΔPu between the power average values P1 and P0 of the reference area A0 and the gap area A1 is used as an index value, not only an effect similar to that of the first embodiment can be obtained, but also measurement of the channel spacing L Can reduce the effects of ASE.

  Further, the index value calculation unit 43a further determines that the adjacent channel # (n-1) on the opposite side to the adjacent channel # (n + 1) with respect to the channel and the frequency band of the predetermined width W3 across the channel #n The difference ΔPd between the power average value P2 in the side gap region and the power average value P0 in the reference region A0 may be calculated as an index value. That is, the index value calculation unit 43a calculates the differences ΔPu and ΔPd as index values. In the following description, the gap area A1 covering the channel #n and the adjacent channel # (n + 1) is described as the high frequency side gap area A1, and the gap area covering the channel #n and the adjacent channel # (n-1) is It is described as the low frequency side gap region.

  Further, in the channel interval table 450a, as indicated by a symbol Gb, the correspondence relationship between the difference ΔPu, the difference ΔPd, and the channel interval L is registered. The channel interval acquisition unit 44a acquires, from the channel interval table 450a, the channel intervals L corresponding to the differences ΔPu and ΔPd, which are index values calculated by the index value calculation unit 43a. Thus, as described above, not only the influence of ASE is reduced in the measurement of the channel spacing L, but the accuracy of the channel spacing L is improved by using the differences ΔPu and ΔPd as two index values.

  FIG. 16 is a diagram showing an example of a channel spacing measurement method using the power average value of each of the high frequency side and low frequency side gap regions A1 and A2. In FIG. 16, the same components as in FIG. 14 will be assigned the same reference numerals and descriptions thereof will be omitted.

  The low frequency side gap region A2 is an example of a third frequency band, and is a frequency band of a predetermined width W3 across the adjacent channel # (n-1) and the channel #n. The center frequency f2 and the width W2 of the low frequency side gap region A2 are set in advance to appropriate values.

  P2 = P2 '+ P2ase (3)

  The power average value P2 of the low frequency side gap region A2 is the sum of the power average value P2 'of the optical signal S and the power average value P2ase of the ASE light, as shown by the above equation (3). Further, the powers P0ase, P1ase and P2ase of each ASE in the reference area A0, the high frequency side gap area A1, and the low frequency side gap area A2 are the same (P0ase = P1ase = P2ase = Pase).

  Therefore, the difference ΔPd between the power average value P0 of the reference area A0 and the low frequency side gap area A2 becomes the difference (P2′−P0 ′) of the power average values P0 ′ and P2 ′ of the optical signal S, and the power P0ase of ASE , The value does not depend on P2ase. Therefore, the index value calculation unit 43a can reduce the influence of ASE by calculating the difference ΔPd as the index value, as in the case of the difference ΔPu. In addition, although difference (DELTA) Pd which is an index value of this example is set to P2-P0, it may be P0-P2.

  As described above, in this example, since two differences ΔPu and ΔPd are used as index values, the measurement accuracy of the channel interval L is improved.

  Referring back to FIG. 13, when the table generation unit 46 generates the channel interval table 450a of the symbol Ga in FIG. 15, the difference from the index value calculation unit 43a is accompanied by the sweep of the center frequency fc as in the first embodiment. The ΔPu is acquired, and the correspondence between the channel interval L and the difference ΔPu is registered in the channel interval table 450a. Further, when generating the channel interval table 450a of the code Gb in FIG. 15, the table generation unit 46 acquires the differences ΔPu and ΔPd from the index value calculation unit 43a along with the sweep of the center frequency fc, and The correspondence relationship between ΔPu and ΔPd is registered in the channel interval table 450a.

  Further, the channel position determination unit 48 calculates the difference between the power average value P1 of the high frequency side gap region A1 and the power average value P2 of the low frequency side gap region A2, and based on the calculated difference, The positional relationship between the adjacent channel # (n + 1) and the adjacent channel # (n-1) is determined. At this time, the channel position determination unit 48 acquires the power average values P1 and P2 from the index value calculation unit 43a.

  More specifically, the channel position determination unit 48 determines that the adjacent channel # (n + 1) and the adjacent channel # (n-1) are closer to the channel #n from the difference between the power average values P1 and P2. Can be determined. The channel position determination unit 48 determines that the adjacent channel # (n + 1) is closer to the channel #n than the adjacent channel # (n−1) when the difference (P1−P2) of the power average values P1 and P2> 0. Do.

  Further, when the difference (P1−P2) of power average values P1 and P2 is smaller than 0, channel position determination unit 48 makes adjacent channel # (n−1) closer to channel #n than adjacent channel # (n + 1). It is determined that Furthermore, when the difference (P1−P2) of the power average values P1 and P2 = 0, the channel position determination unit 48 places the adjacent channel # (n−1) and the adjacent channel # (n + 1) across the channel #n. It determines that it is in a symmetrical position. The reason why such determination can be made is that the shape of the spectrum Sn is symmetrical with respect to the center frequency fc.

  Note that P2-P1 may be calculated instead of P1-P2 as the difference between the power average values P1 and P2. Further, since the powers P1ase and P2ase of the ASE light are not included in the difference between the power average values P1 and P2 as described above, the influence of the ASE on the determination result is reduced.

  Also, the channel position determination unit 48 calculates the difference and the sum of the power average values P1 and P2, and based on the difference and the sum, the adjacent channel # (n + 1) and the adjacent channel # (n-1) for the channel #n Simultaneous approaches can be determined. More specifically, channel position determination unit 48 periodically calculates the difference and the sum of power average values P1 and P2, and when the difference is maintained at 0, when the total is increased, It is determined that the adjacent channel # (n + 1) and the adjacent channel # (n-1) approach the channel #n simultaneously. At this time, in order to reduce the influence of ASE, the channel position determination unit 48 may subtract a value twice as large as the power average value P0 of the reference area A0 from the sum of the power average values P1 and P2.

  The channel position determination unit 48 notifies the control unit 1 c of the determination result of the positional relationship between the adjacent channel # (n + 1) and the adjacent channel # (n−1) with respect to the channel #n. Therefore, the control unit 1c can control the center frequency fc according to the positional relationship, for example, via the SDN controller 3.

  Next, an example of a method of determining the initial value of the center frequency f1 of the high frequency side gap region A1 and the center frequency f2 of the low frequency side gap region A2 will be described.

  FIG. 17 is a diagram showing an example of a method of determining the initial values of the center frequencies f1 and f2 of the gap regions A1 and A2 on the high frequency side and the low frequency side. In FIG. 17, the same components as in FIG. 16 will be assigned the same reference numerals and descriptions thereof will be omitted.

  The control unit 1c sets the positions separated by a half of the width Wsig of the spectrum Sn of the channel #n toward the high frequency side and the low frequency side from the predetermined center frequency fc to the gap areas on the high frequency side and the low frequency side. The temporary center frequencies f1 and f2 of A1 and A2 are set in the index value calculation unit 43a. Thereby, the center frequency f1 is set to fc + 0.5 × Wsig, and the center frequency f2 is set to fc−0.5 × Wsig. The width Wsig of the spectrum Sn is obtained by adding a predetermined margin value α to the baud rate of the optical signal S. For example, if the baud rate is 32 GBaud, it becomes 32 (GHz) + α.

  Next, the control unit 1 c sweeps the center frequency fc toward the high frequency side and the low frequency side within a certain range. The index value calculation unit 43a determines, for example, the power average value Pi1 within the band of 0.5 × W1 on the low frequency side and the low frequency side in the high frequency side gap region A1 along with the sweep of the center frequency fc. For example, a power average value Pi2 within a band of 0.5 × W2 on the high frequency side in the gap area A2 is calculated. As described above, the index value calculation unit 43a calculates the power average values Pi1 and Pi2 for half of the high frequency side gap area A1 and the low frequency side gap area A2 to calculate the adjacent channel # (n + 1) or the adjacent area. The influence of spectrum Sn + 1, Sn-1 of channel # (n-1) is reduced.

  For example, every time the center frequency fc changes at predetermined intervals, the index value calculation unit 43a calculates the absolute value (| Pi1−Pi2 |) or the sum (Pi1 + Pi2) of the difference between the power averages Pi1 and Pi2, and the calculated value is The center frequency fc which is the minimum is detected. The index value calculation unit 43a notifies the detected center frequency fc to the control unit 1c.

  The control unit 1c determines center frequencies f1 and f2 of the high frequency side gap region A1 and the low frequency side gap region A2 from the notified center frequency fc. For example, the center frequency f1 is determined to be fc + 0.5 × Wsig, and the center frequency f2 is determined to be fc−0.5 × Wsig. The controller 1c sets the determined center frequencies f1 and f2 in the index value calculator 43a.

  Further, based on the notified center frequency fc, the control unit 1c controls the center frequency of the local light with respect to the laser diode 104 of the reception unit 1b, and further controls the laser diode 104 of the opposing nodes Na and Nb. The central frequency of the transmission light is controlled for the laser diode 115.

  As described above, the control unit 1c detects the high frequency side gap region A1 and the low frequency side gap region A2 according to the center frequency of the channel of the optical signal at which the absolute value or the sum of the differences of the power averages Pi1 and Pi2 is minimized. A tentative center frequency is determined for each center frequency. As a result, the high frequency side gap region A1 and the low frequency side gap region A2 are set to positions where the influence from the adjacent channel # (n + 1) and the adjacent channel # (n-1) is the least. The control unit 1c is an example of a determination unit that determines the center frequency of the high frequency side gap region A1 and the low frequency side gap region A2.

Third Embodiment
In the second embodiment, the effect of ASE is reduced by using the difference ΔPu of the power average values P0 and P1 of the reference area A0 and the high frequency side gap area A1 as an index value, but a method of reducing the effect of ASE Is not limited to this. For example, if the change rate of the power average value P1 of the high frequency side gap region A1 with respect to the center frequency fc is used as an index value, the index value is not influenced by the ASE because the power Pase of ASE light is constant.

  FIG. 18 is a block diagram showing the channel spacing measurement unit 4 in the third embodiment. In FIG. 18, the same components as in FIG. 3 will be assigned the same reference numerals and descriptions thereof will be omitted.

  The channel interval measurement unit 4 includes a capture processing unit 40, an FFT unit 41, a spectrum data storage unit 42, an index value calculation unit 43b, a channel interval acquisition unit 44b, a table storage unit 45, and a table generation unit 46. Have. The table storage unit 45 stores a channel interval table 450b.

  The index value calculation unit 43b calculates, from the spectra Sn and Sn + 1, the rate of change of the power average value P1 in the gap area A1 with respect to the center frequency fc as an index value. The controller 1 c is an example of a frequency controller, and changes the center frequency fc. More specifically, control unit 1 c changes center frequency fc by ± Δf / 2 (Δf> 0), and index value calculation unit 43 b calculates the power average in gap region A1 at center frequency fc + Δf / 2. A value P1p and a power average value P1m in the gap area A1 at the center frequency fc−Δf / 2 are calculated. Note that Δf is a value preset in the control unit 1c.

  k = (P1p−P1m) / Δf (4)

  Based on the above equation (4), the index value calculation unit 43b determines the rate of change k of the power average value P1 in the gap region A1 with respect to the center frequency fc from the power average values P1p and P1m and the change amount .DELTA.f of the center frequency fc. Calculated as an index value. The index value calculation unit 43b outputs the change rate k to the channel interval acquisition unit 44b.

  In the channel interval table 450b, the correspondence between the change rate k, which is an index value, and the channel interval L is registered. The channel interval acquisition unit 44b acquires, from the channel interval table 450b, the channel interval L corresponding to the change rate k, which is the index value calculated by the index value calculation unit 43b.

  FIG. 19 is a diagram showing an example of a channel interval measurement method using the change rate k of the power average value P1 with respect to the center frequency of the optical signal S. The controller 1 c changes the center frequency fc by ± Δf / 2. Such frequency dithering may be performed by the control of the laser diodes 104 and 115 as described above, or the phase of the data signal Dt is rotated by superimposing the control signal on the data signal Dt in the reception processing circuit 103. It may be carried out by

The latter method is described in the following documents.
・ Thesis Z.Tao et al., “Simple, Robust, and Wide-Range Frequency Offset Monitor for Automatic Frequency Control in Digital Coherent Receivers”, ECOC 2007 ”
-JP 2010-178090-JP 2012-12010-JP 2013-165407

  The index value calculation unit 43b determines from the power average value P1p of the gap area A1 when the center frequency is fc + Δf / 2 and the power average value P1m of the gap area A1 when the center frequency is fc−Δf / 2. The change rate k is calculated based on the equation (4). The rate of change k is not affected by ASE as described below.

  FIG. 20 is a diagram showing an example of a change of the power average value P1 of the gap region A1 with respect to the channel interval L. The code R ′ indicates the change of the power average value P1 when the power Pase ′ of the ASE light is small, and the code R indicates the change of the power average value P1 when the power Pase (> Pase ′) of the ASE light is large .

  The slope of a straight line Lr connecting points (see white circles) whose power average value P1 is P1p, P1m matches the rate of change k. Here, since the power average value P1 gradually decreases as the channel interval L increases, the rate of change k, which is the slope, changes according to the channel interval L. Further, since the powers Pase and Pase ′ of ASE light are constant regardless of the channel spacing L, the slope of the straight line Lr is the straight line Lr ′ when the power Pase of the ASE light is small if the channel spacing L is the same. It is identical to the slope. Therefore, the change rate k of the power average value P1 with respect to the channel interval L is not affected by the ASE.

  Therefore, the index value calculation unit 43b calculates the change rate k as the index value, and the channel interval acquisition unit 44b acquires the channel interval L corresponding to the change ratio k from the channel interval table 450b, thereby measuring the channel interval L. Can reduce the effects of ASE.

  FIG. 21 shows an example of the channel interval table 450b. In the channel interval table 450b, the correspondence between the change rate k, which is an index value, and the channel interval L is registered. For example, when the index value is −0.02, the channel interval acquisition unit 44 b acquires 35.0 (GHz) as the channel interval L. The channel interval table 450 b is an example of a table. The table generation unit 46 generates, for example, a channel interval table 450 having the power average value P1 as an index value as shown in FIG. 5, and calculates the change rate k from the channel interval table 450, thereby generating A channel interval table 450b may be generated.

  FIG. 22 is a flowchart showing an example of a channel spacing measurement method. In FIG. 22, the same processing as in FIG. 8 is assigned the same reference numeral, and the description thereof is omitted.

  After the processing of step St3, the control unit 1c changes the center frequency fc by + Δf (step St40). Next, the index value calculation unit 43b calculates the power average value P1p (step St41).

  Next, control unit 1 c changes center frequency fc by −Δf (step St <b> 42). Next, the index value calculation unit 43b calculates the power average value P1m (step St43). Steps St42 and St43 may be executed prior to steps St40 and St41.

  Next, the index value calculation unit 43b calculates a change rate k as an index value from the power average values P1p and P1m and the change amount Δf of the center frequency fc (Step St44). Next, the channel interval acquisition unit 44b acquires the channel interval L corresponding to the calculated change rate k from the channel interval table 450b (step St5a). In this way, the channel spacing measurement method is implemented.

  Next, quantitative effects according to each example will be described.

  FIG. 23 is a diagram showing an analysis result of the channel spacing L according to the comparative example. As a comparative example, the technology disclosed in Patent Document 1 mentioned above is mentioned.

  The code G1 indicates the change characteristic (spectrum) of the power (dB) with respect to the frequency (GHz) for each channel spacing L. The channel spacing L changes every 0.5 (GHz) in the range of 35.0 to 37.5 (GHz).

  In addition, the code G2 shows the analysis result of the relationship between the channel spacing L and the gap width (GHz) for each block number (see “block”) of the 512-stage fast Fourier transform circuit (see “FFT 512”) that detects the spectrum. Show. The analysis result is based on the change characteristic of the code G1.

  The channel spacing L and the gap width are in a substantially proportional relationship when the number of blocks is 8 or 16 while they are in an irregular relationship when the number of blocks is 32 or 128. That is, when the number of blocks is 32 or 128, highly accurate measurement of the channel spacing L is impossible.

  Therefore, in the case of the comparative example, in order to measure the channel spacing L with high accuracy, 20000 (≒ 512 steps × 32 blocks) or more symbols are required.

  FIG. 24 is a diagram showing analysis results of the channel spacing L according to the example. The code G3 indicates the change characteristic (spectrum) of the power (dB) with respect to the frequency (GHz) for each channel spacing L. The channel spacing L changes every 0.5 (GHz) in the range of 35.0 to 37.5 (GHz).

  The code G4 indicates the analysis result of the relationship between the channel interval L and the index value for each block number (see “block”) of the 512-stage fast Fourier transform circuit (see “FFT 512”) that detects the spectrum. This analysis result is obtained by using the power average value P1 of the high frequency side gap region A1 in the change characteristic of the code G3 as the index value. The fast Fourier transform circuit corresponds to the FFT unit 41.

  The channel interval L and the index value have a fixed relationship, for example, even when the number of blocks is two. Therefore, in the case of the embodiment, it is possible to measure the channel spacing L with high accuracy even with about 1024 (= 512 stages × 2 blocks) symbols.

  As described above, in the comparative example, a large amount of signal data is required, which complicates the process. However, in the embodiment, the process is easy because the signal data may be smaller than the comparative example. Further, in the embodiment, since the channel spacing L is measured using the power average value P1, as described below, the averaging effect is obtained even if the noise increases due to the small number of symbols. Enables highly accurate measurement.

  FIG. 25 is a diagram showing an example of the effect of channel spacing measurement using the power average value P1. A code G5 indicates a change characteristic (spectrum) of power (dB) with respect to a frequency (GHz) at every channel interval L when there are few symbols (8192). Further, a code G6 indicates a change characteristic (spectrum) of power (dB) with respect to a frequency (GHz) at every channel interval L when there are many symbols (65536). The channel spacing L changes every 0.5 (GHz) in the range of 35.0 to 37.5 (GHz).

  The symbol W indicates the gap width of Patent Document 1 described above. When the number of symbols is large, the gap width W can be associated with the channel spacing L because there is little noise. However, when the number of symbols is small, the gap width W is too noisy (see, eg, the symbol Ns). Matching is difficult.

  On the other hand, in the embodiment, since the power average value P1 in the gap region A1 is used, even when the number of symbols is small and the noise is large, the channel spacing L can be clearly correlated by the averaging effect. Therefore, according to the embodiment, the channel spacing L can be easily measured.

  The embodiments described above are examples of preferred implementations of the invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

The following appendices will be further disclosed in connection with the above description.
(Supplementary Note 1) A receiving unit for receiving an optical signal assigned to one of channels of wavelength units provided in a wavelength multiplexing optical signal,
A detection unit that detects a spectrum centered on the channel of the optical signal;
A calculator configured to calculate an average value of power in a frequency band of a predetermined width across the channel of the optical signal and the adjacent channel from the spectrum;
A storage unit that stores the correspondence between the average value of the power and the center frequency interval of the channel of the optical signal and the adjacent channel;
And an acquisition unit for acquiring the center frequency interval corresponding to the average value of the power calculated by the calculation unit from the storage unit.
(Supplementary Note 2) The transmission apparatus according to Supplementary note 1, wherein the calculation unit adjusts the position of the frequency band such that the frequency at which the power is minimum is in the frequency band.
(Supplementary Note 3) The transmission apparatus according to Supplementary note 1 or 2, further comprising an alarm output unit that outputs an alarm when the center frequency interval acquired by the acquisition unit is equal to or less than a predetermined threshold.
(Supplementary Note 4) A receiving unit that receives an optical signal assigned to one of the wavelength unit channels provided in the wavelength multiplexing optical signal,
A detection unit that detects a spectrum centered on the channel of the optical signal;
From the spectrum, an average value of power in a first frequency band of a predetermined width across the channel of the optical signal and the adjacent channel, and an average value of power in a second frequency band of a predetermined width different from the first frequency band A calculation unit that calculates the difference between
A storage unit that stores the correspondence between the difference between the average values of the powers in the first frequency band and the second frequency band, and the center frequency intervals of the channel of the optical signal and the adjacent channel;
And a acquiring unit configured to acquire the central frequency interval corresponding to the difference between the first frequency band calculated by the calculating unit and the average value of the powers of the second frequency band from the storage unit. apparatus.
(Supplementary Note 5) The calculation unit further calculates an average value of power in a third frequency band of a predetermined width across the channel of the optical signal and the adjacent channel on the opposite side to the adjacent channel with respect to the channel of the optical signal. Calculating a difference with an average value of power in the second frequency band,
The storage unit includes a difference between average values of powers in the first frequency band and the second frequency band, and a difference between average values of powers in the third frequency band and the second frequency band. , Storing the correspondence with the center frequency interval,
The acquisition unit is a difference between average values of powers in the first frequency band and the second frequency band calculated by the calculation unit, and each in the third frequency band and the second frequency band. The transmission apparatus according to claim 4, wherein the center frequency interval corresponding to a difference of an average value of power is acquired from the storage unit.
(Supplementary Note 6) A frequency determination unit configured to determine center frequencies of the first frequency band and the third frequency band, respectively.
The frequency determination unit
Positions separated from each other by half the width of the spectrum of the channel of the optical signal from the center frequency of the channel of the optical signal toward the high frequency side and the low frequency side are assumed to be temporary for the first frequency band and the third frequency band. Center frequency of
Sweeping the center frequency of the channel of the optical signal to a high frequency side and a low frequency side within a certain range;
The calculation unit
Calculating, among the first frequency band, a power average value within a low frequency side constant width band and a power average value within a third frequency band high frequency side constant width band; ,
Calculating an absolute value or a sum of a difference between the power average value in the low frequency side constant width band and the power average value in the high frequency side constant width band;
The frequency determination unit
Temporary center frequencies of the first frequency band and the third frequency band according to the center frequency of the channel of the optical signal for which the calculated value is minimum, center frequencies of the first frequency band and the third frequency band The transmission apparatus according to appendix 5, wherein each of the transmission apparatuses is determined.
(Supplementary Note 7) The difference between the average value of the power in the first frequency band and the average value of the power in the third frequency band is calculated, and the adjacent channel or the adjacent channel to the channel of the optical signal is calculated based on the calculated difference. The transmission apparatus according to any one of claims 5 and 6, further comprising a determination unit that determines the positional relationship of the adjacent channel on the opposite side.
(Supplementary Note 8) A receiving unit that receives an optical signal assigned to one of the wavelength unit channels provided in the wavelength multiplexing optical signal,
A frequency control unit that changes a center frequency of the optical signal;
A detection unit that detects a spectrum centered on the channel of the optical signal;
A calculation unit that calculates, from the spectrum, a change rate of an average value of power in a frequency band of a predetermined width across the channel of the optical signal and the adjacent channel with respect to the center frequency of the optical signal;
A storage unit that stores the correspondence between the rate of change and the center frequency interval of the channel of the optical signal and the adjacent channel;
And an acquisition unit configured to acquire the central frequency interval corresponding to the change rate calculated by the calculation unit from the storage unit.
(Supplementary Note 9) A lightwave signal allocated to one of the wavelength unit channels provided in the wavelength multiplexing light signal is received,
Detecting a spectrum centered on the channel of the optical signal;
Calculating an average value of power in a frequency band of a predetermined width across the channel of the optical signal and the adjacent channel from the spectrum;
The center frequency interval corresponding to the calculated average value of the power is acquired from a table in which the correspondence between the average value of the power and the center frequency interval of the channel of the optical signal and the adjacent channel is registered. A channel spacing measurement method characterized by
(Supplementary note 10) The channel spacing measurement method according to supplementary note 9, characterized in that the position of the frequency band is adjusted so that the frequency at which the power is minimum is at the center in the frequency band.
(Supplementary note 11) The channel spacing measurement method according to supplementary note 9 or 10, wherein an alarm is output when the acquired center frequency spacing is equal to or less than a predetermined threshold.
(Supplementary Note 12) An optical signal assigned to one of the wavelength unit channels provided in the wavelength multiplexing optical signal is received,
Detecting a spectrum centered on the channel of the optical signal;
From the spectrum, an average value of power in a first frequency band of a predetermined width across the channel of the optical signal and the adjacent channel, and an average value of power in a second frequency band of a predetermined width different from the first frequency band Calculate the difference with
Calculated from the table in which the correspondence between the difference of the average value of each power in the first frequency band and the second frequency band, and the center frequency interval of the channel of the optical signal and the adjacent channel is registered A channel spacing measurement method, comprising: acquiring the center frequency spacing corresponding to a difference between average values of powers of the first frequency band and the second frequency band.
(Supplementary Note 13) An average value of power in a third frequency band of a predetermined width across the adjacent channel on the opposite side to the adjacent channel with respect to the channel of the optical signal and the channel of the optical signal, and in the second frequency band Calculate the difference with the average value of the power of
A difference between average values of powers in the first frequency band and in the second frequency band, a difference between average values of powers in the third frequency band and the second frequency band, and the center frequency interval The difference between the average values of the respective powers in the first frequency band and in the second frequency band, calculated from the table in which the correspondence relationship with is registered, and the third frequency band and the second frequency band The channel spacing measurement method according to claim 12, characterized in that the center frequency spacing corresponding to the difference between the average values of the respective powers is acquired.
(Supplementary Note 14) The first frequency band and the third position are separated from each other by half the width of the spectrum of the channel of the optical signal from the center frequency of the channel of the optical signal toward the high frequency side and the low frequency side. As a tentative center frequency of the frequency band,
Sweeping the center frequency of the channel of the optical signal to a high frequency side and a low frequency side within a certain range;
Calculating, among the first frequency band, a power average value within a low frequency side constant width band and a power average value within a third frequency band high frequency side constant width band; ,
Calculating an absolute value or a sum of a difference between the power average value in the low frequency side constant width band and the power average value in the high frequency side constant width band;
Temporary center frequencies of the first frequency band and the third frequency band according to the center frequency of the channel of the optical signal for which the calculated value is minimum, center frequencies of the first frequency band and the third frequency band The channel spacing measurement method according to appendix 13, characterized in that each is determined.
(Supplementary Note 15) A difference between an average value of powers in the first frequency band and an average value of powers in the third frequency band is calculated,
The positional relationship of the said adjacent channel with respect to the channel of the said optical signal or the adjacent channel on the said opposite side is determined based on the said calculated difference, The channel spacing measurement method of the additional notes 13 or 14 characterized by the above-mentioned.
(Supplementary note 16) receiving an optical signal assigned to one of the wavelength unit channels provided in the wavelength multiplexing optical signal,
Changing the center frequency of the optical signal,
Detecting a spectrum centered on the channel of the optical signal;
From the spectrum, a change rate of an average value of power in a frequency band of a predetermined width across the channel of the optical signal and the adjacent channel with respect to the center frequency of the optical signal is calculated;
The center frequency interval corresponding to the calculated rate of change is acquired from a table in which the correspondence between the rate of change, the channel of the optical signal, and the center frequency interval of the adjacent channel is registered. Channel spacing measurement method.

DESCRIPTION OF SYMBOLS 1 transceiver 1a transmitter 1b receiver 1c receiver 1 controller 4 channel space | interval measurement part 41 FFT part 43, 43a, 43b index value calculation part 44, 44a, 44b channel space | interval acquisition part 45 table memory part 48 channel position determination part 103 reception processing Circuit 110 Coherent receiver A0 Reference area A1 High frequency side gap area A2 Low frequency side gap area L Channel spacing Sn-1, Sn, Sn + 1 Spectrum P0 to P2 Power average value k Change rate fc, f1, f2 Center frequency

Claims (10)

A receiving unit for receiving an optical signal assigned to one of the channels of the wavelength unit provided in the wavelength multiplexed optical signal;
A detection unit that detects a spectrum centered on the channel of the optical signal;
A calculator configured to calculate an average value of power in a frequency band of a predetermined width across the channel of the optical signal and the adjacent channel from the spectrum;
A storage unit that stores the correspondence between the average value of the power and the center frequency interval of the channel of the optical signal and the adjacent channel;
And an acquisition unit for acquiring the center frequency interval corresponding to the average value of the power calculated by the calculation unit from the storage unit.   The transmission apparatus according to claim 1, wherein the calculation unit adjusts the position of the frequency band such that the frequency at which the power is minimum in the frequency band is at the center.   The transmission apparatus according to claim 1, further comprising an alarm output unit that outputs an alarm when the center frequency interval acquired by the acquisition unit is equal to or less than a predetermined threshold. A receiving unit for receiving an optical signal assigned to one of the channels of the wavelength unit provided in the wavelength multiplexed optical signal;
A detection unit that detects a spectrum centered on the channel of the optical signal;
From the spectrum, an average value of power in a first frequency band of a predetermined width across the channel of the optical signal and the adjacent channel, and an average value of power in a second frequency band of a predetermined width different from the first frequency band A calculation unit that calculates the difference between
A storage unit that stores the correspondence between the difference between the average values of the powers in the first frequency band and the second frequency band, and the center frequency intervals of the channel of the optical signal and the adjacent channel;
And a acquiring unit configured to acquire the central frequency interval corresponding to the difference between the first frequency band calculated by the calculating unit and the average value of the powers of the second frequency band from the storage unit. apparatus. The calculation unit further includes an average value of power in a third frequency band of a predetermined width across the adjacent channel on the opposite side to the adjacent channel with respect to the channel of the optical signal and the channel of the optical signal; Calculate the difference with the average value of power in the frequency band,
The storage unit includes a difference between average values of powers in the first frequency band and the second frequency band, and a difference between average values of powers in the third frequency band and the second frequency band. , Storing the correspondence with the center frequency interval,
The acquisition unit is a difference between average values of powers in the first frequency band and the second frequency band calculated by the calculation unit, and each in the third frequency band and the second frequency band. 5. The transmission apparatus according to claim 4, wherein the center frequency interval corresponding to a difference of an average value of power is acquired from the storage unit. A frequency determination unit configured to determine center frequencies of the first frequency band and the third frequency band, respectively;
The frequency determination unit
Positions separated from each other by half the width of the spectrum of the channel of the optical signal from the center frequency of the channel of the optical signal toward the high frequency side and the low frequency side are assumed to be temporary for the first frequency band and the third frequency band. Center frequency of
Sweeping the center frequency of the channel of the optical signal to a high frequency side and a low frequency side within a certain range;
The calculation unit
Calculating, among the first frequency band, a power average value within a low frequency side constant width band and a power average value within a third frequency band high frequency side constant width band; ,
Calculating an absolute value or a sum of a difference between the power average value in the low frequency side constant width band and the power average value in the high frequency side constant width band;
The frequency determination unit
Temporary center frequencies of the first frequency band and the third frequency band according to the center frequency of the channel of the optical signal for which the calculated value is minimum, center frequencies of the first frequency band and the third frequency band The transmission apparatus according to claim 5, wherein each of   The difference between the average value of the power in the first frequency band and the average value of the power in the third frequency band is calculated, and the adjacent channel to the channel of the optical signal or the opposite side is calculated based on the calculated difference. 7. The transmission apparatus according to claim 5, further comprising a determination unit that determines a positional relationship between adjacent channels. A receiving unit for receiving an optical signal assigned to one of the channels of the wavelength unit provided in the wavelength multiplexed optical signal;
A frequency control unit that changes a center frequency of the optical signal;
A detection unit that detects a spectrum centered on the channel of the optical signal;
A calculation unit that calculates, from the spectrum, a change rate of an average value of power in a frequency band of a predetermined width across the channel of the optical signal and the adjacent channel with respect to the center frequency of the optical signal;
A storage unit that stores the correspondence between the rate of change and the center frequency interval of the channel of the optical signal and the adjacent channel;
And an acquisition unit configured to acquire the central frequency interval corresponding to the change rate calculated by the calculation unit from the storage unit. Receiving an optical signal assigned to one of the wavelength unit channels provided in the wavelength multiplexed optical signal;
Detecting a spectrum centered on the channel of the optical signal;
Calculating an average value of power in a frequency band of a predetermined width across the channel of the optical signal and the adjacent channel from the spectrum;
The center frequency interval corresponding to the calculated average value of the power is acquired from a table in which the correspondence between the average value of the power and the center frequency interval of the channel of the optical signal and the adjacent channel is registered. A channel spacing measurement method characterized by Receiving an optical signal assigned to one of the wavelength unit channels provided in the wavelength multiplexed optical signal;
Detecting a spectrum centered on the channel of the optical signal;
From the spectrum, an average value of power in a first frequency band of a predetermined width across the channel of the optical signal and the adjacent channel, and an average value of power in a second frequency band of a predetermined width different from the first frequency band Calculate the difference with
Calculated from the table in which the correspondence between the difference of the average value of each power in the first frequency band and the second frequency band, and the center frequency interval of the channel of the optical signal and the adjacent channel is registered A channel spacing measurement method, comprising: acquiring the center frequency spacing corresponding to a difference between average values of powers of the first frequency band and the second frequency band.

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