Calculation device, calculation method, and program

Abstract

This calculation device (30) calculates input power to an optical fiber transmission path on each channel in two adjacent bands. The calculation device (30) is characterized in that, assuming a transition of incoming span power caused by the impact of induced Raman scattering depends on the number of existing channels in the optical fiber transmission path, input power for eliminating a gradient of the incoming span power is calculated using a coefficient I that indicates a gradient of an input power spectrum.

Description

[Technical Field]

[0001] The present invention relates to a computing device, a computing method, and a program. [Background technology]

[0002] One of the known nonlinear optical effects of optical fibers that occurs in wavelength division multiplexing transmission is power transition between channels (wavelengths) due to stimulated Raman scattering (SRS) (see, for example, Non-Patent Documents 1 to 4). FIG. 12A is a conceptual diagram of power transition between channels. The first horizontal axis indicates frequency, and the second horizontal axis indicates wavelength. Here, it is assumed that the input power of each channel is equal. The channel value (channel i) is smaller on the right side of the horizontal axis and larger on the left side. The channel adjacent to channel i on the high-frequency, short-wavelength side (right) is channel i-1. The channel adjacent to channel i on the low-frequency, long-wavelength side (left) is channel i+1. Note that the wavelength value corresponding to the channel is smaller on the right side of the horizontal axis and larger on the left side (λ i+1 > λ i > λ i-1 ) On the other hand, the frequency value is larger on the right side of the horizontal axis and smaller on the left side (f i+1 < f i < f i-1 ).

[0003] The optical signal of each channel is transmitted through the optical fiber over a predetermined span length. At this time, the power P of the channel adjacent to the channel i on the higher frequency and shorter wavelength side (right) is increased by SRS. i-1 etc. is the power P of channel i i Also, the power P i is the power P of the adjacent channel on the low-frequency, long-wavelength side (left) i+1 Transition to the side.

[0004] Therefore, the signal quality of the post-transmission power of each channel varies depending on the wavelength. For example, as shown in FIG. 12B, the post-transmission power P i-1 The higher the frequency, the greater the loss. Also, the post-transmission power P of the channel adjacent to channel i on the lower frequency, longer wavelength side (left) i+1 The lower the frequency, the smaller the loss. Therefore, as shown by the two-dot chain line in Fig. 12B, a downward tilt occurs in the spectrum of the post-transmission power of each channel. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Kenta Hirose, Takafumi Fukaya, Masahiro Nakagawa, Takeshi Seki, and Takashi Miyamura, "Analysis of stimulated Raman scattering effects considering changes in the number of wavelengths multiplexed in multi-band wavelength division multiplexing networks," IEICE Technical Report, vol. 121, no. 386, PN2021-57, pp. 29-32, Mar. 2022. [Non-patent document 2] DANIEL SEMRAU,ROBERT KILLEY,POLINA BAYVEL, “Achievable rate degradation of ultra-wideband coherent fiber communication systems due to stimulated Raman scattering,” Optics Express, vol.25, no.12, 13024-13034, June 2017. [Non-patent document 3] Hiroki Kawahara, Kohei Saito, Sachio Suda, Takeshi Seki, and Hideki Maeda, “Cancellation of Static and Dynamic Power Transitions induced by inter-band Stimulated Raman Scattering in C+L-band WDM Transmission,” 25th OptoElectronics and Communications Conference, Taipei, Taiwan, Oct. 2020. [Non-patent document 4] Fukutaro Hamaoka, Kyo Minoguchi, Takeo Sasai, Asuka Matsushita, Masanori Nakamura, Seiji Okamoto, Etsushi Yamazaki, and Yoshiaki Kisaka, “150.3-Tb / s Ultra-Wideband (S, C, and L Bands) Single-Mode Fiber Transmission over 40-km Using >519Gb / s / λ PDM-128QAM Signals,” 44th European Conference on Optical Communication, Rome, Italy, Sept. 2018. Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional single-band, i.e., Dense Wavelength Division Multiplexing (DWDM) technology that uses the C-band (Conventional) or L-band (Long wavelength) wavelength bands, the impact of power transitions between channels can be said to be negligible. The C-band (wavelength, frequency) is (1530-1565 nm, 191.56-195.94 THz). The L-band (wavelength, frequency) is (1565-1625 nm, 184.49-191.56 THz). Therefore, the C-band or L-band wavelength band is approximately 4.8 THz wide.

[0007] On the other hand, when considering DWDM using multiple bands such as the C + L band (approximately 10 THz wide), the effects of power transitions between channels become apparent, resulting in problems such as variations in signal quality due to wavelength. For example, if C-band power shifts to the L-band during optical propagation, excess loss occurs in the C-band, resulting in an excessive drop in signal power at the optical destination. To address this issue, a technique has been proposed to increase the input power of the short-wavelength band where power transitions occur, thereby maintaining a constant received power from short to long wavelengths at the receiving end (output side). However, this technique requires, for example, experimentally determining the rate at which the received power changes and then adjusting the input power (transmit power) for each wavelength based on that value.

[0008] Therefore, an object of the present invention is to solve the above problem and to provide a calculation device, a calculation method, and a program that can calculate the input power that eliminates the tilt of the power arriving at a span in a DWDM system. [Means for solving the problem]

[0009] The calculation device according to the present invention is a calculation device that calculates the input power of each channel in two adjacent bands to an optical fiber transmission line, and is characterized in that it assumes that the transition of the span incoming power due to the influence of stimulated Raman scattering depends on the number of existing channels in the optical fiber transmission line, and calculates the input power that eliminates the slope of the span incoming power using a coefficient 1 that indicates the slope of the input power spectrum. [Effects of the Invention]

[0010] According to the present invention, it is possible to calculate the input power that eliminates the tilt of the power arriving at the span in DWDM. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a system including a computing device and a network device according to a first embodiment of the present invention. [Figure 2A] FIG. 1 is a schematic diagram of a wavelength division multiplexing network. [Figure 2B] FIG. 1 is a schematic diagram of a power spectrum. [Figure 3A] 4 is a flowchart showing the flow of processing by the computing device according to the first embodiment. [Figure 3B] 10 is a flowchart showing the flow of processing by a computing device according to a second embodiment. [Figure 4A] 1 is a graph showing the loss coefficient in a single-mode optical fiber. [Figure 4B] 1 is a graph showing the Raman gain coefficient in a single-mode optical fiber. [Figure 5] 10 is a graph showing a comparative example. [Figure 6A] 1 is a graph showing Example 1. [Figure 6B] 10 is a graph showing Example 2. [Figure 7A] FIG. 1 is a schematic diagram of a wavelength division multiplexing network. [Figure 7B] 10 is an example of a power spectrum before merging. [Figure 7C]10 is another example of the power spectrum before merging. [Figure 7D] 10 is an example of a power spectrum after merging. [Figure 8A] FIG. 10 is a schematic diagram of a set (first set) in which the difference due to wavelength allocation is maximum. [Figure 8B] FIG. 10 is a schematic diagram of a set (second set) in which the difference due to wavelength allocation is maximum. [Figure 8C] FIG. 10 is a schematic diagram of a set (third set) in which the difference due to wavelength allocation is maximum. [Figure 8D] FIG. 10 is a schematic diagram of a set (fourth set) in which the difference due to wavelength allocation is maximum. [Figure 9] 10 is a graph showing coefficient 1 relative to the channel occupancy rate of each band. [Figure 10] 10 is a flowchart showing the flow of processing by a computing device according to a third embodiment. [Figure 11] FIG. 2 is a hardware configuration diagram illustrating an example of a computer that realizes the functions of a computing device according to the present embodiment. [Figure 12A] FIG. 1 is a conceptual diagram of power transition between channels. [Figure 12B] FIG. 1 is a conceptual diagram of the tilt of a power spectrum. DETAILED DESCRIPTION OF THE INVENTION

[0012] The computing device according to this embodiment will be described in detail below with reference to the drawings. [System configuration overview] As shown in FIG. 1, the optical transmission system 1 includes a network facility monitoring device 10 and a network device 20. The network equipment monitoring device 10 is configured by, for example, a network element operation system (NE-OpS). The network equipment monitoring device 10 includes a control unit 11 that monitors the network devices 20.

[0013] The network device 20 is, for example, an optical transmission device such as a ROADM (Reconfigurable Optical Add / Drop Multiplexer). The network device 20 includes, for example, a transponder 21, a wavelength selective switch (WSS) 22, an optical amplifier 23, and a controller 24. The number of network devices 20 is arbitrary. When distinguishing between the three network facilities shown in FIG. 1, they are referred to as NE1, NE2, and NE3, and when not distinguishing between them, they are referred to as network device 20.

[0014] For example, when an electrical signal is input from an external communication device to the transponder 21 of the network device NE1, this electrical signal is converted into an optical signal by the transponder 21, multiplexed by the wavelength selective switch 22, amplified by the optical amplifier 23, and then transmitted to the outside. This optical signal is amplified, for example, by the optical amplifier 23 of the network device NE3. This amplified optical signal is amplified, for example, by the optical amplifier 23 of the network device NE2, then demultiplexed by the wavelength selective switch 22, received by the transponder 21, and transmitted to a communication device (not shown). Note that this optical transmission system 1 is for bidirectional communication. Furthermore, the network device NE3 is a device specialized in amplifying optical signals.

[0015] 2A, optical fiber transmission lines F1 to F11 are laid between a plurality of buildings B1 to B6 to form a wavelength multiplexing network. At least one network device 20 is installed in each of the buildings B1 to B6.

[0016] The network device 20 includes a calculation device 30. Here, the control units 24 of the NE1 and NE2, which are optical transmission devices such as ROADMs, include the calculation device 30 (see FIG. 1). The calculation device 30 calculates the input power of each channel in two adjacent bands to the optical fiber transmission line. The calculation device 30 assumes that the transition of the span arrival power due to the influence of stimulated Raman scattering depends on the number of existing channels in the optical fiber transmission line, and calculates the input power that eliminates the slope of the span arrival power using a coefficient l that indicates the slope of the input power spectrum.

[0017] The calculation device 30 calculates the input power of each channel based on the following formula (1): where i is a channel number (1≦i≦M). i is the center frequency of channel i (f M ≦ f i ≦ f1, 4 THz ≦ f1- f M ≦ 15 THz), where f indicates the center frequency interval of adjacent channels. P i (0) [dBm] is the input power of channel i to the optical fiber transmission line (-10 ≦ P i (0) [dBm] ≦ 10) where l is a coefficient that indicates the slope of the input power spectrum, and P i (0) Indicates the coefficient for controlling [dBm].

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[0018] The calculation device 30 determines the coefficient l that satisfies the condition of equation (2) by iterative calculation using the following equations (2), (3), (4), and (5), assuming that P1(0) [dBm] in equation (1) is 0. Here, ρ i denotes the channel occupancy rate of the band including channel i. L denotes the span length of the optical fiber transmission line. α i is f i g indicates the loss coefficient of the optical fiber transmission line. R (Ω) denotes the Raman gain coefficient as a function of the frequency difference Ω. eff,i indicates the effective length. i indicates the angular frequency. The calculation device 30 fixes the determined coefficient l and calculates the input power based on the formula (1) using the desired communicable P1(0) [dBm] in the formula (1).

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[0019] Equations (2) to (5) use the following assumptions. Assumption 1 is that most of the inter-wavelength power transition due to stimulated Raman scattering occurs within the effective length. Assumption 2 is that the inter-wavelength power transition due to stimulated Raman scattering does not depend on the wavelength allocation in each band.

[0020] [First embodiment] As shown in FIG. 2B, the calculation device 30 according to the first embodiment calculates the input power when all wavelengths are present in each band. As an example, two adjacent bands are the L band and the C band, and M is 144. In the C band, channels 1 (ch1) to 72 (ch72) are set corresponding to the 72 wavelengths. In the L band, channels 73 (ch1) to 144 (ch144) are set corresponding to the 72 wavelengths. Hereinafter, these two bands will be referred to as L 72 ch and C 72 ch.

[0021] In this example, the C-band channel occupancy rate ρ C is 72 / 72 = 1 (100%). Also, the L-band channel occupancy rate ρ L is 72 / 72=1 (100%). That is, the calculation device 30 of this embodiment uses ρ j = 1, the input power is calculated. In this case, the equation (4) can be rewritten as the following equation (4B): Note that in this case, the above-mentioned assumption 2 is unnecessary.

[0022]

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[0023] The calculation device 30 according to the first embodiment determines the coefficient l that satisfies the condition of equation (2) by iterative calculation using equations (2), (3), (4B), and (5) assuming that P1(0) [dBm] is 0 in equation (1). In detail, as shown in FIG. 3A, the calculation device 30 first determines the coefficient l that satisfies the condition of equation (2) by iterative calculation using equations (2), (3), (4B), and (5). i (0) [dBm] is expressed as a function of l (step S11). In this case, equation (1) can be rewritten as the following equation (1B).

[0024]

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[0025] Then, the calculation device 30 determines the coefficient l that satisfies the condition of equation (2) by iterative calculation using equations (2), (3), (4B), and (5) (step S12). j (0), the relationship of formula (1B) is applied. Also, α in formula (4B) i is the loss coefficient α in a single-mode optical fiber shown in Figure 4A. i The horizontal axis of FIG. 4A indicates the frequency ranges of the L band, the C band, and the S band (short wavelength). R The Raman gain coefficient (Ω) in the single-mode optical fiber shown in Figure 4B may be used. The horizontal axis in Figure 4B represents the frequency difference Ω. The span length L is assumed to be 100 km.

[0026] Then, the calculation device 30 fixes the coefficient l and calculates the desired P in equation (1). i (0) [dBm] is used to calculate the input power based on equation (1) (step S13). The calculation device 30 fixes the coefficient l and calculates the desired P i (0) [dBm] may be adjusted.

[0027] Next, a first simulation performed to confirm the effects of the computing device 30 according to this embodiment will be described. Example 1 The calculation device 30 calculates P i (0) = 0 dBm, and l = -0.01001 was determined. Then, the calculation device 30 calculated the input power of L 72 ch and C 72 ch under the condition of l = -0.01001. In detail, when M = 144 and the frequency f i The L 72 ch was set to a frequency range of 186.5 [THz] to 190.05 [THz] with a center frequency interval of f = 50 [GHz], and the C 72 ch was set to a frequency range of 192.55 [THz] to 196.1 [THz] with a center frequency interval of f = 50 [GHz]. Incidentally, it is known that the power change for each channel taking into consideration the inter-wavelength power transition due to stimulated Raman scattering is expressed by the following equation (7) (see Non-Patent Document 2).

[0028]

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[0029] In equation (7), M represents the total number of channels (total number of wavelengths), and i represents the channel number (i = 1 is the shortest wavelength). i denotes the power of channel i, and ω i denotes the angular frequency of channel i, z denotes the longitudinal distance of the optical fiber, and g R (Ω) denotes the Raman gain coefficient. α i denotes the loss coefficient at the frequency of channel i. Ω denotes the frequency difference between the frequencies of channel i and channel j. The first and second terms on the right side of equation (7) represent the inter-wavelength power transfer due to stimulated Raman scattering. The third term represents the transmission loss of the optical fiber.

[0030] In Example 1, in order to confirm the effect of the calculation device 30, the power before transmission was set to P1(0) = 0 dBm, and the power for each channel after 100 km transmission (post-transmission spectrum) was calculated by numerical calculation based on equation (7). For comparison with Example 1, the power spectrum after transmission for a comparative example in which no special effort was made to adjust the input power was calculated by numerical calculation based on equation (7). Figure 5 shows the results of numerical calculation for the comparative example. Here, the power before transmission is P i The post-transmission power was calculated for L 72 ch and C 72 ch, assuming (0) = 0 dBm. In Figure 5, the horizontal axis represents frequency and the vertical axis represents post-transmission power. In the comparative example, the slope of the span arrival power is clear, and the difference between the maximum and minimum post-transmission power values is approximately 6 dB.

[0031] Fig. 6A is a graph showing Example 1 of the input power spectrum and the post-transmission power spectrum. In Fig. 6A, the horizontal axis represents frequency, and the vertical axis represents post-transmission power and input power, respectively. In the figure, "Input" represents input power. "Numerical output" is the result of numerical calculation of the post-transmission spectrum based on equation (7). In channel 144, the input power was −1.921 dBm and the power after transmission was −20.153 dBm, a loss of approximately 18 dBm. In channel 1, the input power was 0 dBm and the power after transmission was −21.018 dBm, with a loss of approximately 21 dBm. As shown, the power spectrum becomes flat after transmission.

[0032] In Example 1, as shown in FIG. 6A, the slope of the span-incoming power caused by stimulated Raman scattering is eliminated and becomes flat. Example 1 shows good results in improving the variation in signal quality due to wavelength. The calculation device 30 of this embodiment can calculate the input power that keeps the range of the span-incoming power caused by stimulated Raman scattering within 1 dB.

[0033] As shown in Figure 6A, the difference between the maximum and minimum post-transmission power is approximately 1 dB. This is due to transmission loss, separate from the physical phenomenon of stimulated Raman scattering. The wavelength dependence of the loss in the transmission path of this optical fiber itself can be expressed as 0.01 dB / km × L. When the span length L is 100 km, the transmission loss is 1 dB.

[0034] The network device 20 equipped with the calculation device 30 inputs light of two adjacent bands into the optical fiber transmission line at the calculated input power, and sets the range of the span incoming power to 0.01 dB / km × L + 1 dB or less for both the channel center frequency and the number of existing channels in the optical fiber transmission line, where L is the span length [km] of the optical fiber transmission line.

[0035] By doing this, when the network device 20 inputs light of two adjacent bands into the optical fiber transmission line at the calculated input power, it flattens the span incoming power under conditions that also include the wavelength dependency of the loss inherent in the transmission line of the optical fiber itself, thereby improving the variation in signal quality due to wavelength.

[0036] Example 2 The calculation device 30 fixed the previously determined coefficient l to −0.01001, set P1(0)=3 dBm, and calculated the input power of L 72 ch and C 72 ch using equation (1). In addition, in Example 2, in order to confirm the effect of the calculation device 30, the power before transmission was set to P1(0) = 3 dBm, and the power for each channel after 100 km transmission (post-transmission spectrum) was calculated by numerical calculation based on Equation (6). 6B is a graph showing the input power spectrum and the post-transmission power spectrum of Example 2. Like Example 1, Example 2 shows good results in that variations in signal quality due to wavelength can be improved.

[0037] [Second embodiment] In the first embodiment, the input power was calculated when all wavelengths were available in each band. However, considering the wavelength usage status of an actual wavelength multiplexing network, it is unlikely that all available channels will be wavelength-multiplexed. Furthermore, in an actual wavelength multiplexing network, the number of multiplexed wavelengths changes over time, and the optimal transmission conditions change from moment to moment. In this embodiment, as shown in FIG. 7A, a network device 20 equipped with a calculation device 30 is installed in each of buildings B1 to B6. For example, an optical signal passing through an optical fiber transmission line F7 and an optical signal passing through an optical fiber transmission line F10 are combined in the network device 20 installed in building B6 and then pass through an optical fiber transmission line F11. FIG. 7B shows the power spectrum of an optical signal passing through the optical fiber transmission line F7. FIG. 7C shows the power spectrum of an optical signal passing through the optical fiber transmission line F10. FIG. 7D shows the power spectrum of an optical signal passing through the optical fiber transmission line F11. Thus, in an actual wavelength multiplexing network, each wavelength repeatedly joins and splits. Therefore, in the second embodiment, the channel occupancy rate ρ of each band is calculated. i In the following, we will consider the C-band channel occupancy rate as ρ C Also, the L-band channel occupancy rate is expressed as ρ L It is written as follows.

[0038] Considering the power transition between channels (wavelengths) due to stimulated Raman scattering, the following four pairs have the same number of wavelengths and the largest difference in wavelength allocation between two adjacent bands. As shown in FIG. 8A, the first set is a set consisting of all the L-band channels and half the C-band channels (lowest frequency side). The second set is a set consisting of all the L-band channels and half the C-band channels (on the highest frequency side), as shown in FIG. 8B. The third set is a set consisting of half of the L-band channels (lowest frequency side) and all of the C-band channels, as shown in FIG. 8C. The fourth set is a set consisting of half of the L-band channels (highest frequency side) and all of the C-band channels, as shown in FIG. 8D. The difference between these four arrangements is small, at 0.5 dB. In other words, the power transition is not dependent on the wavelength arrangement of each band, but is determined by the number of wavelengths. This number of wavelengths is determined by the total number of channels M and the C-band channel occupancy rate ρ C The product of the total number of channels M and the L-band channel occupancy rate ρ L It is expressed as the sum of the product of and.

[0039] The calculation device 30 according to the second embodiment determines the coefficient l that satisfies the condition of equation (2) by iterative calculation using equations (2), (3), (4), and (5) assuming that P1(0) [dBm] is 0 in equation (1). In detail, as shown in FIG. 3B, the calculation device 30 first determines the coefficient l that satisfies the condition of equation (2) by iterative calculation using equations (2), (3), (4), and (5). i (0) [dBm] is expressed as a function of l (step S21). In this case, equation (1) can be rewritten as equation (1B) described above.

[0040] Then, the calculation device 30 determines the coefficient l that satisfies the condition of equation (2) by iterative calculation using equations (2), (3), (4), and (5) (step S22). j The relationship of formula (1B) is applied to (0). j For C-band channel occupancy rate ρ C and L-band channel occupancy rate ρ L After defining (ρ C , ρ L ) for the α i In Fig. 4A, i You can also use the value of g R (Ω) is the g shown in Figure 4B R The value of (Ω) may be used. The span length L is assumed to be 100 km. Then, the calculation device 30 fixes the coefficient l and calculates the desired P in equation (1). i (0) [dBm] is used to calculate the input power based on equation (1) (step S23). The calculation device 30 fixes the coefficient l and calculates the desired Pi (0) [dBm] may be adjusted.

[0041] Next, the coefficient 1 determined by the calculation device 30 according to this embodiment will be described. As described above, the calculation device 30 calculates the C-band channel occupancy rate ρ C and L-band channel occupancy rate ρ L After determining the value of (ρ C , ρ L ) to determine l. The graph in Figure 9 shows the relationship between (ρ C , ρ L This is a contour graph that shows the numerical range of l for each of the following three-dimensional data using a plane (rectangle) where a rectangular parallelepiped intersects with a specified plane. The channel occupancy rate ρ of the band containing channel i i By definition, ρ is a number between 0 and 1. C ,ρ L The range of is 0 ≦ ρ C ≦ 1,0 ≦ ρ L ≦ 1. This contour graph is divided into 10 equal parts between l=-0.010 and l=0.000. In the graph, the lower vertex, (ρ C ,ρ L )=(1,1), l=0.000. In the graph, the upper vertex, (ρ C ,ρ L )=(0,0), l=-0.010. In the graph, the left vertex, (ρ C ,ρ L )=(1,0), l=-0.006. In the graph, the right vertex, (ρ C ,ρ L )=(0,1), l=-0.005.

[0042] As shown in FIG. 9, the calculation device 30 of the second embodiment determines l corresponding to the channel occupancy rate of each band and performs the calculation of equation (1), thereby making it possible to calculate the input power that keeps the range of the span incoming power generated by stimulated Raman scattering at 1 dB or less.

[0043] [Third embodiment] In the first and second embodiments, the calculation device 30 determines the coefficient l by iterative calculation so as to satisfy the condition of equation (2), but the method for determining the coefficient l is not limited to this. The calculation device 30 of the third embodiment calculates P i (0) [dBm] The coefficient l for controlling is determined by iterative calculation. In equation (6), ρ i denotes the channel occupancy rate of the band including channel i. L denotes the span length of the optical fiber transmission line. α i is f i g indicates the loss coefficient of the optical fiber transmission line. R (Ω) indicates the Raman gain coefficient, which is a function of the frequency difference Ω. mW indicates the unit milliwatt. The calculation device 30 fixes the determined coefficient l and calculates the input power based on equation (1) using the desired communicable P1(0) [dBm] in equation (1). Note that in equation (6), 1 mW can be expressed in units of α1 or α M This is to match the unit of [ / km], which is the same as the

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[0044] In detail, as shown in FIG. 10, the calculation device 30 first calculates P i (0) The coefficient l for controlling [dBm] is determined by iterative calculation (step S31). The calculation device 30 calculates ρ j For C-band channel occupancy rate ρ C and L-band channel occupancy rate ρ L After defining (ρ C , ρ L) is determined. In addition, α1 in equation (6) is the α at the frequency of ch1 in the graph shown in Figure 4A. i Similarly, the value of α M In the graph shown in FIG. 4A, α at the frequency of ch M (=ch 144) i The value of g can be used. R (Ω) is the g shown in Figure 4B R The value of (Ω) may be used. The span length L is, for example, 100 km. Then, the calculation device 30 fixes the coefficient l and calculates the desired P in equation (1). i (0) [dBm] is used to calculate the input power based on equation (1) (step S32).

[0045] The calculation device 30 of the third embodiment determines l based on equation (6) and performs the calculation of equation (1), thereby making it possible to calculate the input power that keeps the range of the span incoming power generated by stimulated Raman scattering at 1 dB or less.

[0046] [Hardware configuration] The computing device 30 according to the embodiment is realized by a computer 900 having a configuration as shown in Fig. 11. Fig. 11 is a hardware configuration diagram showing an example of the computer 900 that realizes the functions of the computing device 30 according to the embodiment. The computer 900 has a CPU (Central Processing Unit) 901, a ROM (Read Only Memory) 902, a RAM (Random Access Memory) 903, an HDD (Hard Disk Drive) 904, an input / output I / F (Interface) 905, a communication I / F 906, and a media I / F 907.

[0047] The CPU 901 operates based on a program stored in the ROM 902 or the HDD 904. The ROM 902 stores a boot program executed by the CPU 901 when the computer 900 is started up, programs related to the hardware of the computer 900, and the like.

[0048] The CPU 901 controls an input device 910 such as a mouse or keyboard, and an output device 911 such as a display or printer, via an input / output I / F 905. The CPU 901 acquires data from the input device 910 via the input / output I / F 905, and outputs generated data to the output device 911. Note that a GPU (Graphics Processing Unit) or the like may be used as a processor together with the CPU 901.

[0049] The HDD 904 stores programs executed by the CPU 901 and data used by the programs, etc. The communication I / F 906 receives data from other devices via the communication network 920 and outputs the data to the CPU 901, and also transmits data generated by the CPU 901 to other devices via the communication network 920.

[0050] The media I / F 907 reads a program or data stored in the recording medium 912 and outputs it to the CPU 901 via the RAM 903. The CPU 901 loads a program related to a target process from the recording medium 912 onto the RAM 903 via the media I / F 907, and executes the loaded program. The recording medium 912 is an optical recording medium such as a DVD (Digital Versatile Disc) or a PD (Phase Change Rewritable Disc), a magneto-optical recording medium such as an MO (Magneto Optical Disk), a magnetic recording medium, or a semiconductor memory.

[0051] For example, when the computer 900 functions as the computing device 30 according to the embodiment, the CPU 901 executes a program loaded onto the RAM 903 to realize the functions of the computing device 30. The HDD 904 stores data in the RAM 903. The CPU 901 reads and executes a program related to a target process from the recording medium 912. Alternatively, the CPU 901 may read a program related to a target process from another device via the communication network 920.

[0052] [effect] As described above, the calculation device calculates the input power of each channel in two adjacent bands to an optical fiber transmission line, and is characterized in that it assumes that the transition of the span incoming power due to the influence of stimulated Raman scattering depends on the number of existing channels in the optical fiber transmission line, and calculates the input power that eliminates the slope of the span incoming power using a coefficient 1 that indicates the slope of the input power spectrum.

[0053] By doing this, the calculation device calculates the input power of each channel in two adjacent bands, and can therefore calculate the optimal amount of input power for the short wavelength band to be boosted in advance in order to maintain a constant incoming power from the short wavelength band to the long wavelength band on the receiving side.

[0054] The calculation device calculates the input power of each channel by: i is a channel number (1≦i≦M), f i is the center frequency of channel i (f M ≦ f i ≦ f1, 4 THz ≦ f1- f M ≦ 15 THz), f is the center frequency interval of adjacent channels, P i (0) [dBm] is the input power of channel i to the optical fiber transmission line (-10 ≦ P i (0) [dBm] ≦ 10), where l is a coefficient indicating the slope of the input power spectrum, the method is characterized by being executed based on the following equation (1).

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[0055] By doing this, the calculation device calculates the input power of each channel in two adjacent bands based on equation (1). Equation (1) was created by focusing on changes in the wavelength of adjacent channels, assuming that transitions in the span arrival power due to the influence of stimulated Raman scattering do not depend on the wavelength allocation of each band, but on the number of existing channels in the optical fiber transmission line. By using an appropriate coefficient l in equation (1), the calculation device can calculate the input power that eliminates the slope of the span arrival power in DWDM.

[0056] In the computing device, ρ i is the channel occupancy rate of the band including channel i, L is the span length of the optical fiber transmission line, α i f i Loss coefficient of the optical fiber transmission line, g R (Ω) is the Raman gain coefficient as a function of the frequency difference Ω, L eff,i is the effective length, ω i is the angular frequency, P1(0) [dBm] is assumed to be 0 in equation (1), and a coefficient l that satisfies the condition of equation (2) is determined by iterative calculation using the following equations (2), (3), (4), and (5), and the determined coefficient l is fixed, and a desired communicable P1(0) [dBm] is used in equation (1) to calculate the input power of each channel based on equation (1).

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[0057] By doing this, the calculation device uses equations (2) to (5) to search for the coefficient l that minimizes the difference between the power at each effective length and its average value for all wavelengths from the shortest wavelength to the longest wavelength. The coefficient l obtained by the iterative calculation using equations (2) to (5) thus indicates the condition under which the power spectrum at the effective length becomes flat. Therefore, by applying the coefficient l to equation (1), the calculation device can calculate the input power that eliminates the slope of the incoming power at the span in DWDM. Furthermore, once the coefficient l is determined and fixed by the iterative calculation, the calculation device can easily find the optimal input power for each channel using equation (1) each time, even if the input power (P1(0) [dBm]) of the highest frequency at the input end in each band is changed.

[0058] In the calculation device, ρ in Eq. (4) i is 1, the coefficient l is determined, and the input power of each channel is calculated based on the equation (1) by fixing the determined coefficient l and using the desired communicable P1(0) [dBm] in the equation (1).

[0059] By doing this, the calculation device searches for the coefficient l that minimizes the difference between the power at each effective length and its average value for all wavelengths from the shortest to the longest, assuming that the channel occupancy rate of the band including channel i is 1. As a result, the calculation device can calculate the input power when all channels are active (all channels are occupied) in two adjacent bands.

[0060] The computing device is i is the channel occupancy rate of the band including channel i, L is the span length of the optical fiber transmission line, α i f i Loss coefficient of the optical fiber transmission line, g RWhen (Ω) is the Raman gain coefficient that is a function of the frequency difference Ω, and mW is milliwatts, the coefficient l that indicates the slope of the input power spectrum is determined by iterative calculation using the following equation (6), and the input power of each channel is calculated based on equation (1) by fixing the determined coefficient l and using the desired communicable P1(0) [dBm] in equation (1).

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[0061] By doing this, the calculation device uses equation (6) to search for the coefficient l that minimizes the difference between the power at the effective length of the longest wavelength and the power at the effective length of the shortest wavelength. The coefficient l obtained by iterative calculation using equation (6) thus indicates the condition under which the power spectrum at the effective length becomes flat. Therefore, by applying coefficient l to equation (1), the calculation device can calculate the input power that eliminates the slope of the incoming power at the span in DWDM. Furthermore, once coefficient l is determined and fixed by iterative calculation, the calculation device can easily find the optimal input power for each channel using equation (1) each time, even if the input power (P1(0) [dBm]) of the highest frequency at the input end in each band is changed.

[0062] The calculation method is a calculation method of a calculation device 30 that calculates the input power of each channel in two adjacent bands to an optical fiber transmission line, and is characterized in that the transition of the span incoming power due to the influence of stimulated Raman scattering is assumed to depend on the number of existing channels in the optical fiber transmission line, and the input power that eliminates the tilt of the span incoming power is calculated using a coefficient 1 that indicates the tilt of the input power spectrum.

[0063] In this way, the calculation device 30 calculates the input power of each channel in two adjacent bands, and therefore, the calculation device 30 can calculate the optimum amount of input power for the short wavelength band to be increased in advance in order to maintain constant incoming power from the short wavelength band to the long wavelength band on the receiving side.

[0064] The calculation method is to calculate the input power of each channel, where i is the channel number (1 ≦ i ≦ M), and f i is the center frequency of channel i (f M ≦ f i ≦ f1, 4 THz ≦ f1- f M ≦ 15 THz), f is the center frequency interval of adjacent channels, P i (0) [dBm] is the input power of channel i to the optical fiber transmission line (-10 ≦ P i (0) [dBm] ≦ 10), l to P i (0) [dBm] is the coefficient for controlling the frequency response, the frequency response is executed based on the following equation (1).

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[0065] In this way, in the calculation method, the calculation device 30 calculates the input power of each channel in two adjacent bands based on equation (1). Equation (1) is a mathematical equation created by focusing on changes in the wavelength of adjacent channels, assuming that the transition of the span arrival power due to the influence of stimulated Raman scattering does not depend on the wavelength allocation of each band but on the number of existing channels in the optical fiber transmission line. By using an appropriate coefficient l in equation (1), the calculation device 30 can calculate the input power that eliminates the gradient of the span arrival power in DWDM.

[0066] The present invention is not limited to the above-described embodiments, and many modifications can be made by a person skilled in the art within the technical concept of the present invention. For example, although the two adjacent bands are the L band and the C band, they may be the C band and the S band, or the U band (ultralong wavelength) and the L band.

[0067] Furthermore, although the control units 24 of the network devices NE1 and NE2 are described as being equipped with the calculation device 30, this is not limitative. For example, the control unit 24 of the network device NE3 may be equipped with the calculation device 30. Furthermore, the control unit 11 of the network equipment monitoring device 10 may be equipped with the calculation device 30. [Explanation of symbols]

[0068] 1 Optical transmission system 10 Network equipment monitoring device 11 Control section 20 Network Equipment 21 Transponder 22 Wavelength Selective Switch 23 Optical amplifier 24 Control Unit 30 Computing equipment

Claims

1. A calculation device for calculating input power of each channel in two adjacent bands to an optical fiber transmission line, comprising: A calculation device characterized by assuming that the transition of the span incoming power due to the influence of stimulated Raman scattering depends on the number of existing channels in the optical fiber transmission line, and calculating the input power that eliminates the slope of the span incoming power using a coefficient l that indicates the slope of the input power spectrum.

2. Calculating the input power for each channel: i is the channel number (1 ≦ i ≦ M), f i is the center frequency of channel i (f M ≦ f i ≦ f 1 , 4 THz ≦ f 1 -f M ≦ 15 THz), f is the center frequency interval of adjacent channels, P i (0) [dBm] is the input power of channel i to the optical fiber transmission line (-10 ≦ P i (0) [dBm] ≦ 10), where l is the coefficient indicating the slope of the input power spectrum.

2. The computing device according to claim 1, wherein the computing device executes the computation based on the following formula (1): [Equation 1]

3. ρ i is the channel occupancy rate of the band including channel i, L is the span length of the optical fiber transmission line, α i f i Loss coefficient of the optical fiber transmission line, g R (Ω) is the Raman gain coefficient as a function of the frequency difference Ω, L eff,i is the effective length, ω i When is the angular frequency, In the formula (1), P 1 (0) [dBm] is assumed to be 0, and the coefficient l that satisfies the condition of equation (2) is determined by iterative calculation using the following equations (2), (3), (4), and (5); The determined coefficient l is fixed, and the desired communication possible P 1 3. The calculation device according to claim 2, wherein the calculation of the input power of each channel is performed based on the formula (1) using (0) [dBm]. [Equation 2]

4. In the formula (4), ρ i determining the coefficient l assuming that is 1; The determined coefficient l is fixed, and the desired communication possible P 1 4. The calculation device according to claim 3, wherein the calculation of the input power of each channel is performed based on the formula (1) using (0) [dBm].

5. ρ i is the channel occupancy rate of the band including channel i, L is the span length of the optical fiber transmission line, α i f i Loss coefficient of the optical fiber transmission line, g R where (Ω) is the Raman gain coefficient as a function of the frequency difference Ω, and mW is milliwatts. A coefficient l indicating the slope of the input power spectrum is determined by iterative calculation using the following equation (6): The determined coefficient l is fixed, and the desired communication possible P 1 3. The calculation device according to claim 2, wherein the calculation of the input power of each channel is performed based on the formula (1) using (0) [dBm]. [Equation 3]

6. A calculation method for a calculation device that calculates input power of each channel in two adjacent bands to an optical fiber transmission line, comprising: A calculation method characterized by assuming that the transition of the span incoming power due to the influence of stimulated Raman scattering depends on the number of existing channels in the optical fiber transmission line, and calculating the input power that eliminates the slope of the span incoming power using a coefficient l that indicates the slope of the input power spectrum.

7. Calculating the input power for each channel: i is the channel number (1 ≦ i ≦ M), f i is the center frequency of channel i (f M ≦ f i ≦ f 1 , 4 THz ≦ f 1 -f M ≦ 15 THz), f is the center frequency interval of adjacent channels, P i (0) [dBm] is the input power of channel i to the optical fiber transmission line (-10 ≦ P i (0) [dBm] ≦ 10), where l is the coefficient indicating the slope of the input power spectrum.

7. The calculation method according to claim 6, wherein the calculation method is performed based on the following formula (1): [Equation 4]

8. A program for causing a computer to function as the computing device according to any one of claims 1 to 5.

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