Calculation device, network device, calculation method and program

Abstract

Calculation devices (30) calculate input power of each channel in two adjacent bands to an optical fiber transmission path. The calculation devices (30) are characterized by determining that a transition of span incoming power due to the effect of stimulated Raman scattering depends on the number of existing channels in the optical fiber transmission path, and using a factor r indicative of the power ratio between a target channel and an adjacent channel to calculate the input power for eliminating a gradient in the span incoming power.

Description

[Technical Field]

[0001] The present invention relates to a computing device, a network 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. 15A 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 a 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. 15B, 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. 15B, 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 provide a calculation device, a network device, a calculation method, and a program that can solve the above problem and calculate the input power that eliminates the gradient of the span arrival power in DWDM. [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 gradient of the span incoming power using a coefficient r that indicates the ratio of the power of the target channel to the adjacent channel. [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 4C] 4C is a graph showing a portion of FIG. 4B. [Figure 4D] 4D is a graph showing a linear approximation of the Raman gain coefficient of FIG. 4C. [Figure 5] 10 is an example of a relational expression between coefficient r and power P1(0). [Figure 6A] 1 is a graph showing Example 1. [Figure 6B] 6B is a graph showing an enlarged view of FIG. 6A. [Figure 6C] 10 is a graph showing a comparative example. [Figure 6D] 10 is a graph showing Example 2. [Figure 6E] 10 is a graph showing Example 3. [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 9A] 10 is a graph showing Example 4. [Figure 9B] 10 is a graph showing Example 5. [Figure 9C] 10 is a graph showing Example 6. [Figure 9D] 10 is a graph showing Example 7. [Figure 10A] 10 is a graph showing Example 8. [Figure 10B] 10 is a graph showing Example 9. [Figure 10C] 10 is a graph showing Example 10. [Figure 11A] 1 is a graph showing Example 11. [Figure 11B] 10 is a graph showing Example 12. [Figure 11C] 1 is a graph showing Example 13. [Figure 12A] 1 is a graph showing Example 14. [Figure 12B] 1 is a graph showing Example 15. [Figure 12C] 1 is a graph showing Example 16. [Figure 13A] 1 is a graph showing Example 17. [Figure 13B] 10 is a graph showing Example 18. [Figure 13C] 1 is a graph showing Example 19. [Figure 14] 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 15A] FIG. 1 is a conceptual diagram of power transition between channels. [Figure 15B] 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 devices 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 r that indicates the ratio of the power of the target channel to the adjacent channel.

[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) is the input power of channel i to the optical fiber transmission line (0.1 mW ≦ P i (0) ≦ 10 mW). r is P i (0) [dBm] indicates the coefficient for controlling. ρ1 indicates the channel occupancy rate of Band 1 on the high-frequency short-wavelength side. ρ2 indicates the channel occupancy rate of Band 2 on the low-frequency long-wavelength side. L indicates the span length of the optical fiber transmission line. α indicates the loss coefficient of the optical fiber transmission line. k indicates the slope of the Raman gain coefficient.

number

[0018] [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.

[0019] In this example, the high frequency short wavelength band 1 is the C band, so ρ1 is C Also, since the low frequency long wavelength band 2 is the L band, ρ2 is expressed as ρ L It is written as ρ C The channel occupancy rate of ρ is 72 / 72=1 (100%). L The channel occupancy rate of is 72 / 72=1 (100%). That is, the calculation device 30 of this embodiment calculates the input power assuming that ρ1=ρ2=1 in equation (1). In this case, equation (1) can be rewritten as the following equation (1B).

[0020]

number

[0021] The calculation device 30 according to the first embodiment determines a coefficient r when applying P1(0) that enables desired communication when i is 1 in equation (1B), fixes the determined coefficient r, and calculates the input power of each channel based on equation (1B). In detail, as shown in FIG. 3A, the calculation device 30 first expresses P1(0) as a function of r assuming that i is 1 in equation (1B) (step S11). In this case, equation (1B) is rewritten as the following equation (1C).

[0022]

number

[0023] Then, the calculation device 30 determines the coefficient r when the desired P1(0) is applied in the relational expression (Equation (1C)) between P1(0) and r (step S12). Then, the calculation device 30 fixes the coefficient r and calculates the input power based on Equation (1B) (step S13).

[0024] Here, the derivation of equation (1) will be briefly explained using mathematical formulas. It is known that the power change for each channel taking into account the power transition between wavelengths due to stimulated Raman scattering is expressed by the following equation (2) (see Non-Patent Document 2).

[0025]

number

[0026] In equation (2), 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 idenotes the loss coefficient at the frequency of channel i. Ω denotes the difference between the frequency of channel i and the frequency of channel j (hereafter referred to as the frequency difference). The first and second terms on the right side of equation (2) represent the inter-wavelength power transfer due to stimulated Raman scattering. The third term represents the transmission loss of the optical fiber.

[0027] The following assumptions are used to derive equation (1). Assumption 1 is that most of the inter-wavelength power transfer due to stimulated Raman scattering occurs within the effective length. Assumption 2 is that the following approximate equations (3a), (3b), (3c), and (3d) hold true. g R = kΩ … Equation (3a) ω j / ω i ? 1 … Formula (3b) α i = α … Equation (3c) L eff, i = L eff … Formula (3d)

[0028] Equation (3a) shows that the Raman gain coefficient is linear with respect to the frequency difference. Note that k is the slope of the Raman gain coefficient. Equation (3b) shows that the angular frequency is almost constant regardless of the channel. Equation (3c) shows that the loss coefficient is constant regardless of the channel frequency. Equation (3d) shows that the effective length is constant regardless of the channel.

[0029] Figure 4A shows the loss coefficient α in a single-mode optical fiber. i Figure 4B shows an example of the Raman gain coefficient in a single-mode optical fiber. The horizontal axis indicates the frequency range of the L-band, C-band, and S-band (short wavelength). Figure 4B shows an example of the Raman gain coefficient in a single-mode optical fiber. The horizontal axis indicates the frequency difference. When considering the combined frequency range of two adjacent bands (approximately 10 THz wide), the frequency difference is at most 10 THz, so we only need to consider the left half of the graph in Figure 4B. Figure 4C is a graph showing a portion of Figure 4B. Figure 4D shows the Raman gain coefficient linearly approximated against the frequency difference, which corresponds to equation (3a).

[0030] Furthermore, assumption 3 is that the power transfer between wavelengths due to stimulated Raman scattering does not depend on the wavelength arrangement in each band. From equations (2), (3a), (3b), (3c) and (3d), the effective length L eff The spectrum at can be formulated as the following pair of equations (4a) and (4b). Note that the channel occupancy rate ρ j When is set to 1, the effective length L eff The spectrum at can be formulated as the following pair of equations (4a) and (4c):

[0031]

number

[0032] According to equation (4a), the effective length L eff The recurrence formula for flattening the spectrum at is expressed by the following formula (5a) using the relationship of formula (4b), and further rearranged, it is expressed by the following formula (5b).

[0033]

number

[0034] In addition, the channel occupancy rate ρ j When is set to 1, the effective length L between channel i and channel i+1 is calculated by equation (4a). eff The recurrence formula for flattening the spectrum at is expressed by the following formula (5c) using the relationship of formula (4c), and when further rearranged, it is expressed by the following formula (5d).

[0035]

number

[0036] Then, solving equation (5b) as a geometric progression leads to equation (1). Furthermore, solving equation (5d) as a geometric progression leads to equation (1B). The calculation device 30 according to the first embodiment calculates the input power of each channel based on equation (1B) where ρ1 = ρ2 = 1 in equation (1). FIG. 5 shows an example of P1(0) expressed as a function of r by the calculation device 30 assuming that i is 1 in equation (1B). The calculation device 30 may adjust r from the relationship (r, P1 [dBm]) taking into account the generalized signal-to-noise ratio (GSNR).

[0037] According to the graph of FIG. 5, for example, when P1 [dBm] = 0 [dBm], r = 0.9975. When P1 [dBm] = 3 [dBm], r = 0.9955. When P1 [dBm] = 5 [dBm], r = 0.9937. The calculation device 30 can calculate the r corresponding to the set value from the relational expression (r, P1 [dBm]) based on a set value previously stored as P1 [dBm]. Alternatively, the calculation device 30 may calculate the r corresponding to the input value from the relational expression (r, P1 [dBm]) based on an input value entered by a user as P1 [dBm].

[0038] 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 calculated the input power of L 72 ch and C 72 ch under the condition of r = 0.9975 (corresponding to P1(0) = 0 dBm) in equation (1B). 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]. The loss coefficient α was calculated by the α iThe slope k of the Raman gain coefficient was assumed to be the slope of the graph shown in Figure 4D. The span length L was assumed to be 100 [km]. In addition, 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 (2).

[0039] 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 (2). In channel 144, the input power was -2.175 dBm and the power after transmission was -20.412 dBm, a loss of approximately 18 dBm. In channel 1, the input power was 0 dBm and the power after transmission was −20.060 dBm, with a loss of approximately 20 dBm. As shown, the power spectrum becomes flat after transmission.

[0040] FIG. 6B is a graph showing an enlarged view of the post-transmission power spectrum of FIG. 6A. 6C is a graph showing the post-transmission power spectrum of a comparative example where no input power adjustment is made. 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. Meanwhile, the calculation device 30 can calculate the input power that keeps the range of the span arrival power generated by stimulated Raman scattering within 1 dB. In Example 1, as shown in FIG. 6B, the slope of the span arrival power generated by stimulated Raman scattering is eliminated and becomes flat. Example 1 shows good results in improving the variation in signal quality due to wavelength.

[0041] As shown in Figure 6B, 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.

[0042] 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.

[0043] Example 2 As in the first embodiment, the calculation device 30 calculated the input power of L 72 ch and C 72 ch under the condition of r 2 =0.9955 (corresponding to P1(0)=3 dBm) in equation (1B). 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 (2). 6D is a graph showing the input power spectrum and the power spectrum after transmission in Example 2. Example 2 shows good results in that the variation in signal quality due to wavelength can be improved.

[0044] Example 3 As in the first embodiment, the calculation device 30 calculated the input power of L 72 ch and C 72 ch under the condition of r 2 =0.9937 (corresponding to P1(0) =5 dBm) in equation (1B). In addition, in Example 3, in order to confirm the effect of the calculation device 30, the power before transmission was set to P1(0) = 5 dBm, and the power for each channel after 100 km transmission (post-transmission spectrum) was calculated by numerical calculation based on equation (2). 6E is a graph showing the input power spectrum and the power spectrum after transmission in Example 3. Example 3 shows good results in that the variation in signal quality due to wavelength can be improved.

[0045] [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 branches. Therefore, in the second embodiment, the channel occupancy rate ρ C ,ρ L Consider:

[0046] 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 channel occupancy rate ρ C The product of the total number of channels M and the channel occupancy rate ρ L It is expressed as the sum of the product of and.

[0047] The calculation device 30 according to the second embodiment determines a coefficient r when applying P1(0) that enables desired communication when i is 1 in equation (1), fixes the determined coefficient r, and calculates the input power of each channel based on equation (1). In detail, as shown in FIG. 3B, the calculation device 30 first expresses P1(0) as a function of r assuming that i is 1 in equation (1) (step S21). In this case, equation (1) is rewritten as the following equation (1D):

[0048]

number

[0049] Then, the calculation device 30 determines the coefficient r when the desired P1(0) is applied in the relational expression (Equation (1D)) between P1(0) and r (step S22).The calculation device 30 then fixes the coefficient r and calculates the input power based on Equation (1) (step S23). The calculation device 30 according to the second embodiment calculates the input power of each channel based on equation (1). For simplicity, the graph in FIG. 5 is assumed to be P1(0) expressed as a function of r, where i is 1 in equation (1). The calculation device 30 calculates the input power of each channel based on equation (1). C , ρ L , P1[dBm]), r can be adjusted taking into account the GSNR.

[0050] Next, a second simulation performed to confirm the effects of the computing device 30 according to this embodiment will be described. In the graph of FIG. 5, for example, r=0.9975, 0.9981, 0.9980, 0.9986 are all assumed to be P1[dBm]=0 [dBm], and the channel occupancy rate ρ C , ρ L Calculations were carried out for four patterns in which the value is 0.5 or 1.0 (hereinafter referred to as Example 4, Example 5, Example 6, and Example 7). In addition, in the second simulation, 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 (2).

[0051] Example 4 The calculation device 30 calculates (r, ρ C , ρ L , P1[dBm]) = (0.9975, 1.0, 1.0, 0). The detailed conditions are the same as in Example 1. 9A is a graph showing Example 4 of the input power spectrum and the power spectrum after transmission. The graph can be read in the same way as the graph in FIG. 6A. As shown in the figure, the power spectrum after transmission has become flat.

[0052] Example 5 The calculation device 30 calculates (r, ρ C , ρ L , P1[dBm]) = (0.9980, 1.0, 0.5, 0). The detailed conditions are the same as in Example 1. 9B is a graph showing Example 5 of the input power spectrum and the power spectrum after transmission. The graph can be read in the same way as the graph in FIG. 6A. As shown in the figure, the power spectrum after transmission has become flat.

[0053] Example 6 The calculation device 30 calculates (r, ρ C , ρ L , P1[dBm]) = (0.9981, 0.5, 1.0, 0). The detailed conditions are the same as in Example 1. 9C is a graph showing Example 6 of the input power spectrum and the power spectrum after transmission. The graph can be read in the same way as the graph in FIG. 6A. As shown in the figure, the power spectrum after transmission has become flat.

[0054] Example 7 The calculation device 30 calculates (r, ρ C , ρ L , P1[dBm]) = (0.9986, 0.5, 0.5, 0). The detailed conditions are the same as in Example 1. 9D is a graph showing Example 7 of the input power spectrum and the power spectrum after transmission. The graph can be read in the same way as the graph in FIG. 6A. As shown in the figure, the power spectrum after transmission has become flat.

[0055] Next, a third simulation performed to confirm the effects of the computing device 30 according to this embodiment will be described. In the graph of FIG. 5, for example, r=0.9975 (P i (0) = 0 dBm) for various channel occupancy rates ρ C , ρ L For these 12 patterns (hereinafter referred to as Examples 8 to 19), the input power was calculated based on equation (1) under the same conditions as in Example 1. In the third simulation, in order to confirm the effect of the calculation device 30, the power before transmission is set to P i (0) = 0 dBm, the power for each channel after 100 km transmission (post-transmission spectrum) was calculated numerically based on equation (2).

[0056] Example 8 The calculation device 30 calculated the input power of L 72 ch and C 36 ch (lower) in equation (1), where C 36 ch (lower) means ch37 to ch72. Example 9 The calculation device 30 calculated the input power of L 72 ch and C 36 ch (higher) in equation (1), where C 36 ch (higher) refers to ch1 to ch36. Example 10 The calculation device 30 calculated the input power of L 72 ch and C 36 ch (alternate) in equation (1), where C 36 ch (alternate) refers to the odd-numbered channels (1, 3, ..., 71) in the C band.

[0057] Example 11 The calculation device 30 calculated the input power of L 36 ch (lower) and C 72 ch in equation (1), where L 36 ch (lower) means ch109 to ch144. Example 12 The calculation device 30 calculated the input power of L 36 ch (higher) and C 72 ch in equation (1), where L 36 ch (higher) refers to ch73 to ch108. Example 13 The calculation device 30 calculated the input power of L 36 ch (alternate) and C 72 ch in equation (1), where L 36 ch (alternate) refers to the odd-numbered channels (73, 75, ..., 143) in the L band.

[0058] Example 14 The calculation device 30 calculated the input power of L 72 ch and C 1 ch (lowest) in equation (1), where C 1 ch (lowest) means ch72. Example 15 The calculation device 30 calculated the input power of L 72 ch and C 1 ch (highest) in equation (1), where C 1 ch (highest) means ch1. Example 16 The calculation device 30 calculated the input power of L 72 ch and C 1 ch (middle) in equation (1), where C 1 ch (middle) means ch 36.

[0059] Example 17 The calculation device 30 calculated the input power of L 1 ch (lowest) and C 72 ch in equation (1), where L 1 ch (lowest) means ch144. Example 18 The calculation device 30 calculated the input power of L 1 ch (highest) and C 72 ch in equation (1), where L 1 ch (highest) means ch73. Example 19 The calculation device 30 calculated the input power of L 1 ch (middle) and C 72 ch in equation (1), where L 1 ch (middle) means ch108.

[0060] 10A, 10B, 10C, 11A, 11B, 11C, 12A, 12B, 12C, 13A, 13B, and 13C show the results of numerical calculations of post-transmission power spectra for Examples 8 to 19, respectively.

[0061] The calculation device 30 of the second embodiment can calculate the input power that keeps the range of the span incoming power generated by stimulated Raman scattering at 1 dB or less. Examples 4 to 19 show good results in improving the variation in signal quality due to wavelength.

[0062] [Hardware configuration] The computing device 30 according to the embodiment is realized by, for example, a computer 900 configured as shown in Fig. 14. Fig. 14 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] [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 gradient of the span incoming power using a coefficient r that indicates the ratio of the power of the target channel to the adjacent channel.

[0069] 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.

[0070] 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) is the input power of channel i to the optical fiber transmission line (0.1 mW ≦ P i (0) ≦ 10 mW), r is a coefficient indicating the power ratio between the target channel and the adjacent channel, ρ1 is the channel occupancy rate of the high-frequency short-wavelength side band 1, ρ2 is the channel occupancy rate of the low-frequency long-wavelength side band 2, L is the span length of the optical fiber transmission line, α is the loss coefficient of the optical fiber transmission line, and k is the slope of the Raman gain coefficient, which is characterized by being executed based on the following equation (1).

number

[0071] 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. The coefficient r corresponds to the common ratio of a geometric progression. By using an appropriate coefficient r in equation (1), the calculation device can calculate the input power that eliminates the slope of the span arrival power in DWDM.

[0072] The calculation device is characterized in that it determines a coefficient r when applying the desired communicable P1(0) when i is 1 in equation (1), fixes the determined coefficient r, and calculates the input power of each channel based on equation (1).

[0073] By doing so, when the left side of equation (1) is P1(0), the calculation device determines the coefficient r when the desired P1(0) is applied to the relationship between r and P1(0) when r on the right side is changed. This coefficient r is smaller than 1. Using equation (1), the calculation device can calculate an input power spectrum with a slope such that the power of a channel decreases as the channel number increases. Therefore, using the calculated input power, it is possible to flatten the span incoming power, which normally has a slope such that the incoming power of a channel increases as the channel number increases. Furthermore, even if the input power (P1(0) [dBm]) of the highest frequency at the input terminal in each band is changed, the calculation device can easily find the optimal value of the input power for each channel using equation (1) by determining the coefficient r each time.

[0074] The calculation device is characterized in that it determines a coefficient r when ρ1=ρ2=1 in equation (1), fixes the determined coefficient r, and calculates the input power of each channel based on equation (1) when ρ1=ρ2=1 in equation (1).

[0075] By doing this, the calculation device determines the coefficient r by assuming that the channel occupancy rate of the high-frequency short-wavelength side band 1 and the channel occupancy rate of the low-frequency long-wavelength side band 2 are both 1. As a result, the calculation device can calculate the input power when all channels are open (all channels are filled) in two adjacent bands.

[0076] The network device includes the calculation device, and is characterized in that when light of two adjacent bands is input to an optical fiber transmission line at the input power calculated by the calculation device and the span length of the optical fiber transmission line is L km, the range of the span incoming power is 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.

[0077] By doing this, the network equipment's calculation device calculates the input power to keep the span arrival power within a range of 1 dB or less, with the goal of eliminating the slope of the span arrival power caused by the physical phenomenon known as stimulated Raman scattering. Furthermore, apart from stimulated Raman scattering, the wavelength dependence of loss inherent in the transmission line of the optical fiber itself can be expressed as 0.01 dB / km × L. When light of two adjacent bands is input into the optical fiber transmission line at the calculated input power, the network equipment flattens the span arrival power under conditions that also include the wavelength dependence of loss inherent in the transmission line of the optical fiber itself, thereby improving variations in signal quality due to wavelength.

[0078] The calculation method is a calculation method of 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 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 gradient of the span incoming power is calculated using a coefficient r that indicates the ratio of the power of the target channel to the adjacent channel.

[0079] 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.

[0080] The calculation method is to calculate the input power of each channel by using i as the channel number (1 ≦ i ≦ M), fi 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) is the input power of channel i to the optical fiber transmission line (0.1 mW ≦ P i (0) ≦ 10 mW), r is a coefficient indicating the power ratio between the target channel and the adjacent channel, ρ1 is the channel occupancy rate of the high-frequency short-wavelength side band 1, ρ2 is the channel occupancy rate of the low-frequency long-wavelength side band 2, L is the span length of the optical fiber transmission line, α is the loss coefficient of the optical fiber transmission line, and k is the slope of the Raman gain coefficient, which is characterized by being executed based on the following equation (1).

number

[0081] By doing this, 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 formula 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. The coefficient r corresponds to the common ratio of a geometric progression. By using an appropriate coefficient r in equation (1), the calculation device 30 can calculate the input power that eliminates the slope of the span arrival power in DWDM.

[0082] 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.

[0083] 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]

[0084] 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 that calculates an input power that eliminates the gradient of the span incoming power, using a coefficient r that indicates the ratio of the power of a target channel to that of an adjacent channel, 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.

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) is the input power of channel i to the optical fiber transmission line (0.1 mW ≦ P i (0) ≦ 10 mW), r is the coefficient indicating the power ratio between the target channel and the adjacent channel, ρ 1 is the channel occupancy rate of the high-frequency short-wavelength band 1, ρ 2 is the channel occupancy rate of the low-frequency long-wavelength band 2, L is the span length of the optical fiber transmission line, α is the loss coefficient of the optical fiber transmission line, and k is the slope of the Raman gain coefficient, 2. The computing device according to claim 1, wherein the computing device executes the computation based on the following formula (1): [Equation 1]

3. In the above formula (1), when i is 1, the desired communicable P 1 Determine the coefficient r when applying (0), 3. The calculation device according to claim 2, wherein the input power of each channel is calculated based on the equation (1) while the determined coefficient r is fixed.

4. In the formula (1), ρ 1 = ρ 2 determining the coefficient r when The determined coefficient r is fixed, and ρ in the above equation (1) is 1 = ρ 2 4. The computing device according to claim 3, wherein when .times. ...

5. A computing device according to any one of claims 1 to 4, inputting light of two adjacent bands into an optical fiber transmission line at the input power calculated by the calculation device; When the span length of the optical fiber transmission line is L km, A network device characterized in that the range of span incoming power is 0.01 dB / km × L + 1 dB or less for both the channel center frequency and the number of existing channels in an optical fiber transmission line.

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 gradient of the span incoming power using a coefficient r that indicates the ratio of the power of the target channel to the adjacent channel.

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) is the input power of channel i to the optical fiber transmission line (0.1 mW ≦ P i (0) ≦ 10 mW), r is the coefficient indicating the power ratio between the target channel and the adjacent channel, ρ 1 is the channel occupancy rate of the high-frequency short-wavelength band 1, ρ 2 is the channel occupancy rate of the low-frequency long-wavelength band 2, L is the span length of the optical fiber transmission line, α is the loss coefficient of the optical fiber transmission line, and k is the slope of the Raman gain coefficient, 7. The calculation method according to claim 6, wherein the calculation method is performed based on the following formula (1): [Equation 2]

8. A program for causing a computer to function as the computing device according to any one of claims 1 to 4.

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