Analysis device

Abstract

An analysis device according to the present invention analyzes a power profile for signal light from an optical transmission system that uses distributed Raman amplification from backward excitation light. The analysis device comprises an input unit that receives input of information that indicates signal conditions, the characteristics of an optical fiber transmission path, and conditions for Raman excitation light, an amplification characteristics analysis unit that calculates the power profile using the information inputted to the input unit to perform iterative calculation of a coupling equation and performs analysis of distributed Raman amplification characteristics, and an output unit that outputs information that indicates the distributed Raman amplification characteristics analyzed by the amplification characteristics analysis unit. The amplification characteristics analysis unit comprises a first analysis unit that performs first analysis processing that causes convergence to an approximate power profile while avoiding divergence and a second analysis unit that performs second analysis processing that causes convergence to a more accurate power profile using an update formula based on a perturbation approach. The first analysis processing causes convergence to the approximate power profile by analysis of the coupling equation for the reverse direction of only the backward excitation light.

Description

analysis device

[0001] The present invention relates to an analysis device.

[0002] Advances in information communication and processing technologies have led to a steady increase in Internet traffic. This has led to demand for ever-increasing capacity in optical communication systems, which are the foundation of high-speed, large-capacity communications. To achieve this, it is important to design optical communication systems by identifying operating conditions that maximize transmission capacity under multiple constraints. To achieve this, technology is needed to estimate system performance more accurately and with greater computational efficiency.

[0003] Conventionally, there is an estimation technique for distributed Raman amplification, which is often used in large-capacity optical amplifier repeater transmission systems. Distributed Raman amplification can increase the minimum power of signal light in an optical fiber transmission line and suppress degradation of the signal-to-noise ratio (SNR) of the signal light, thereby contributing to an increase in the transmission capacity of the system. Distributed Raman amplification is generally often used together with rare-earth doped optical fiber amplifiers.

[0004] FIG. 1 shows a schematic diagram of the configuration of an optical fiber transmission line during distributed Raman amplification. In FIG. 1, the input end of the optical fiber transmission line is on the left side of the figure, and the output end of the optical fiber transmission line is on the right side of the figure. Signal light is input from the input end. There are two types of distributed Raman amplification: forward pumping and backward pumping. Forward pumping light is input from the input end, and backward pumping light is input from the output end. However, it is not necessary to use both forward pumping light and backward pumping light; only one of them may be used. When high-power pumping light is input into the optical fiber transmission line in addition to the signal light, stimulated Raman scattering (SRS) occurs between the signal light and the pumping light, generating a distributed gain for the signal light.

[0005] When designing an optical transmission system using distributed Raman amplification, the power profile of the signal affected by the distributed Raman amplification (in the longitudinal direction and frequency direction of the optical fiber transmission line) is required. The signal power profile is used to analyze the signal quality or transmission capacity of the optical transmission system, and based on the analyzed signal quality and transmission capacity, it can be used to evaluate the quality of the operating conditions of the optical transmission system.

[0006] One method for determining the power profile of a signal is to analyze coupled equations (Non-Patent Document 1: simultaneous differential equations for signal light and pump light). An example of the coupled equations is shown below.

[0007]

[0008] where i is the index of the frequency component (signal light and pump light), and its center frequency f ｉ is in ascending order (f １ <f ２ <...<f Ｎ－１ <f Ｎ ) and ρ ｉ is a variable that changes depending on the direction of travel, the signal light and forward pumping light are +1, the backward pumping light is -1, and P ｉ is the power, and C Ｒ (f ｓ , f ｐ ) is f ｐ From the frequency components of f ｓ is the Raman gain coefficient for the frequency component of ｉ ) is the power attenuation coefficient of the optical fiber transmission line.

[0009] When analyzing the coupled equations, the power of the signal light and pump light at the input end of the optical fiber transmission line are used as boundary values, and the changes in the power of the signal light and pump light are calculated sequentially along the length of the optical fiber transmission line. The difficulty of obtaining an accurate power profile depends on whether the power at the input end of the optical fiber transmission line (marked with a star in Figure 1) is known. As for the signal light, since it enters the input end of the optical fiber transmission line, the power of the signal light at the input end is known and can be used as a boundary condition in the coupled equation analysis.

[0010] When forward pumping light is used, the forward pumping light is also incident from the input end of the optical fiber transmission line, and thus is similarly known information. The power of the forward pumping light at the input end can be used as a boundary condition in analyzing the coupled equation. On the other hand, when backward pumping light is used, the backward pumping light is incident from the output end of the optical fiber transmission line, and therefore the power of the backward pumping light at the input end cannot be accurately determined unless it is measured or calculated taking into account the interaction with the signal light (and forward pumping light) due to SRS. Note that the power of the backward pumping light cannot always be measured, and even if it could be measured, it would be a time-consuming task, so it is desirable to be able to calculate it. Therefore, when backward pumping light is used, it is difficult to obtain an accurate power profile of the signal light.

[0011] In the past, a common approach was to determine the backward pumping light power at the input end by ignoring the interaction between the signal light (and forward pumping light) and the backward pumping light due to SRS, and then analyze the coupled equations using this as a boundary condition. This is called an approximation that ignores pump depletion. In this case, the power profile can basically be obtained by analyzing the coupled equations once in the forward direction, but an error occurs in the direction that the power profile of the signal light is overestimated.

[0012] JP 2010-160514 A

[0013] S. Tariq and JC Palais, "A Computer Model of Non-Dispersion-Limited Stimulated Raman Scattering in Optical Fiber Multiple-Channel Communications," Journal of Lightwave Technology, vol.11, no.12, pp.1914-1924, doi:10.1109 / 50.257951, December 1993.

[0014] In order to obtain an accurate power profile of signal light taking into account pump depletion of backward pumping light due to SRS interaction between signal light and backward pumping light, it is necessary to initialize the power of the backward pumping light at a virtual input end as a boundary condition, analyze the coupling equation multiple times, and gradually converge to an accurate power profile. However, there is a problem in that no calculation method has been proposed to date that can efficiently calculate an accurate power profile of signal light in an optical transmission system using distributed Raman amplification, even when backward pumping light is used.

[0015] In view of the above circumstances, an object of the present invention is to enable efficient calculation of an accurate power profile of signal light in an optical transmission system using distributed Raman amplification, even when backward pumping light is used.

[0016] One aspect of the present invention is an analysis device that analyzes a power profile of signal light in an optical transmission system that uses distributed Raman amplification with backward pumping light, the analysis device comprising: an input unit that accepts input of information indicating signal conditions, characteristics of an optical fiber transmission line, and conditions of Raman pumping light; an amplification characteristic analysis unit that calculates the power profile by iteratively calculating a coupled equation using the information input to the input unit, and analyzes distributed Raman amplification characteristics; and an output unit that outputs information indicating the distributed Raman amplification characteristics analyzed by the amplification characteristic analysis unit, wherein the amplification characteristic analysis unit comprises: a first analysis unit that performs a first analysis process that converges to an approximate power profile while avoiding divergence; and a second analysis unit that performs a second analysis process that converges to a more accurate power profile by using an update equation based on perturbation approximation, and the first analysis process converges to the approximate power profile by analyzing the coupled equation in the reverse direction of only the backward pumping light.

[0017] Another aspect of the present invention is an analysis device that analyzes a power profile of signal light in an optical transmission system that uses distributed Raman amplification with backward pumping light, the analysis device comprising: an input unit that accepts input of information indicating signal conditions, characteristics of an optical fiber transmission line, and conditions of Raman pumping light; an amplification characteristic analysis unit that calculates the power profile by iteratively calculating a coupled equation using the information input to the input unit, and analyzes distributed Raman amplification characteristics; and an output unit that outputs information indicating the distributed Raman amplification characteristics analyzed by the amplification characteristic analysis unit, wherein the amplification characteristic analysis unit comprises: a first analysis unit that performs a first analysis process that converges to an approximate power profile while avoiding divergence; and a second analysis unit that performs a second analysis process that converges to a more accurate power profile by using an update equation based on perturbation approximation, and the first analysis process converges to the approximate power profile by taking into account only loss in the optical fiber transmission line.

[0018] Another aspect of the present invention is an analysis device that analyzes a power profile of signal light in an optical transmission system that uses distributed Raman amplification with backward pumping light, the analysis device comprising: an input unit that accepts input of information indicating signal conditions, characteristics of an optical amplifier, and characteristics of a transceiver; an amplification characteristic analysis unit that calculates the power profile by iteratively calculating coupled equations using the information input to the input unit and analyzes distributed Raman amplification characteristics; a signal quality analysis unit that analyzes signal quality by calculating effects of signal distortion and noise in the optical transmission system based on the power profile calculated by the amplification characteristic analysis unit and the information input to the input unit; and an output unit that outputs information indicating the signal quality analyzed by the signal quality analysis unit, wherein the amplification characteristic analysis unit comprises: a first analysis unit that performs a first analysis process that converges to an approximate power profile while avoiding divergence; and a second analysis unit that performs a second analysis process that converges to a more accurate power profile by using an update equation based on perturbation approximation,

[0019] Another aspect of the present invention is an analysis device that analyzes a power profile of signal light in an optical transmission system that uses distributed Raman amplification with backward pumping light, the analysis device comprising: an input unit that accepts input of information indicating signal conditions, characteristics of an optical amplifier, and characteristics of a transceiver; an amplification characteristic analysis unit that calculates the power profile by iteratively calculating a coupled equation using the information input to the input unit, and analyzes distributed Raman amplification characteristics; a signal quality analysis unit that analyzes signal quality by calculating effects of signal distortion and noise in the optical transmission system based on the power profile calculated by the amplification characteristic analysis unit and the information input to the input unit; and an output unit that outputs information indicating the signal quality analyzed by the signal quality analysis unit, wherein the amplification characteristic analysis unit comprises: a first analysis unit that performs a first analysis process that converges to an approximate power profile while avoiding divergence; and a second analysis unit that performs a second analysis process that converges to a more accurate power profile by using an update equation based on perturbation approximation, the first analysis process converging to the approximate power profile taking into account only loss in an optical fiber transmission line.

[0020] According to the present invention, it is possible to efficiently calculate an accurate power profile of signal light in an optical transmission system using distributed Raman amplification, even when backward pumping light is used.

[0021] FIG. 1 is a schematic diagram showing an example of the configuration of an optical fiber transmission line during distributed Raman amplification. FIG. 2 is a diagram showing an overall image of a calculation method by an analysis device according to a first embodiment of the present invention. FIG. 3 is a schematic diagram of a power profile. FIG. 4 is a flowchart showing a first-stage calculation flow according to a first embodiment of the present invention. FIG. 5 is a flowchart showing a first-stage calculation flow according to the first embodiment of the present invention. FIG. 6 is a flowchart showing a second-stage calculation flow according to the first embodiment of the present invention. FIG. 7 is a flowchart showing a first-stage calculation flow according to a second embodiment of the present invention. FIG. 8 is a schematic diagram showing a first-stage calculation flow according to a second embodiment of the present invention. FIG. 9 is a diagram showing a comparison of on-off Raman amplification gain. FIG. 10 is a schematic diagram of a distributed Raman amplification characteristic analysis device 1a according to a first embodiment of the present invention. FIG. 11 is a schematic diagram of a distributed Raman amplification characteristic analysis device 1b according to a second embodiment of the present invention. FIG. 12 is a schematic diagram of a signal quality analysis device 1c according to the first embodiment of the present invention. FIG. 13 is a schematic diagram of a signal quality analysis device 1d according to a second embodiment of the present invention.

[0022] Hereinafter, an analysis device according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0023] In the calculation method of the embodiment, the power profile of the signal light is gradually converged to an accurate power profile that takes into account the pump depletion of the backward pumping light by repeatedly analyzing the coupled equations multiple times (it is also possible to obtain the power profile of the pumping light). Here, the optical spectrum (P ｉ and f ｉ ) are assumed to be known, and the power profile of the signal light is calculated from these optical spectra. Other optical fiber transmission line characteristics (loss, Raman gain coefficient, etc.) required for coupled equation analysis are also assumed to be known.

[0024] The power profile is gradually updated so that the calculated spectrum of backward pumping light at the output end of the optical fiber transmission line approaches the known spectrum of backward pumping light input from the output end of the optical fiber transmission line. A state in which there is a small error between the known spectrum of backward pumping light and the calculated spectrum of backward pumping light corresponds to a state in which the power profile is calculated with pump depletion accurately taken into account.

[0025] FIG. 2 shows an overview of a method for efficiently calculating an accurate signal power profile when using backward-pumping distributed Raman amplification. To improve convergence, two stages of calculation are performed. As shown in FIG. 2, the first stage is a low-precision calculation (step S1), and the second stage is a high-precision calculation (step S2). The purpose of the first stage is to avoid divergence of the signal power profile and to make the calculated signal power profile approximate the final desired accurate power profile with approximate accuracy.

[0026] To explain the divergence of the power profile, Fig. 3 shows a schematic diagram of the signal power profile along the longitudinal direction of an optical fiber transmission line. In Fig. 3, the solid line represents a normal case where there is no divergence, and the dashed line represents a case where the power profile diverges. The divergence of the power profile occurs when the power of the backward pumping light at the input end of the optical fiber transmission line is set to a value that is too high and deviates from reality. This corresponds to the case where the pump depletion is underestimated (overestimated in terms of power). As a result, the distributed Raman amplification gain is overestimated and accumulates along the longitudinal direction of the optical fiber, causing the power to diverge in the +∞ direction.

[0027] In the second stage, the power profile is updated while taking into account the frequency dependence of pump depletion, thereby converging the approximate power profile obtained in the first stage to an accurate power profile. By combining the first and second stages, the convergence of the power profile can be improved (i.e., the calculation speed can be increased) while avoiding divergence of the power profile.

[0028] The calculation methods of the two embodiments will be explained below. For simplicity, the case where only the signal light and the backward pumping light are used will be explained here, without including the forward pumping light. Even when the forward pumping light is included, the calculation method can be expanded by paying attention to the order of the frequency indexes.

[0029] First Embodiment A first embodiment will be described below. In the first stage of calculation, the objective function f ｃｏｓｔ is minimized (searched for a local minimum value) with respect to the variable X (one dimension). The range of X is as shown in the following formula (2).

[0030]

[0031] Here, max(C Ｒ ) is the maximum value of the Raman gain coefficient, and P ｓｉｇ (0) = [P １ (0), P ２ (0), ..., P ｋ (0)] Ｔ (k is the final index representing the frequency of the signal light) is a vector representing the signal light power at the input end (z=0), and L is the length of the optical fiber transmission line.

[0032] The lower limit value of the formula (2) is exp(-max(C Ｒ )ΣP ｓｉｇ (0)L) corresponds to a generous estimate of pump depletion and is obtained by analogy with the approximate solution of distributed Raman amplification gain ignoring pump depletion. The upper limit value 1 corresponds to the case where pump depletion is ignored. Therefore, by searching within the range of equation (2), it is possible to find X where the objective function takes a minimum value. This X is a one-dimensional variable and represents the amount of attenuation of the pump light power due to pump depletion, ignoring frequency dependence.

[0033] f ｃｏｓｔ is the calculated power of the backward pumping light (P ｂｐ (L) = [P ｋ＋１ (L), P ｋ＋２ (L), ..., P Ｎ (L)] Ｔ) and the power of the target backward pumping light given as a boundary condition (P ｂｐ，ｔ (L) = [P ｋ＋１，ｔ (L), P ｋ＋２，ｔ (L), ..., P Ｎ，ｔ (L)] Ｔ , t is an abbreviation for target) is defined to represent the error. ｃｏｓｔ is set, for example, as shown in the following equation (3).

[0034]

[0035] Here, m is a weight that adjusts the power region in which the power profile contributes to the objective function, and the larger the value of m, the greater the contribution of the region with high power. ｃｏｓｔ The smaller the value, the closer the pump depletion is taken into account and the closer the power profile is to the correct value.

[0036] Figure 4 shows the calculation flow for the first stage. Figure 5 illustrates the iterative calculation part of the calculation flow. In both figures, (a), (b), (c), (d) and (e) correspond to each other. First, the input signal power P ｓｉｇ (0) and the backward pumping optical power P ｂｐ，ｔ (L) is set (step S001).

[0037] Then, the process enters the iterative calculation section (L0s to L0e in FIG. 4). The iterative calculation section first initializes X (in the first iteration). Alternatively, the iterative calculation section first updates X (in the second iteration or later (i.e., during iterative calculation)) (step S002). The search range at this time is as shown in the above-mentioned formula (2), and an optimization algorithm such as a golden section search can be used.

[0038] Next, P ｂｐ (L) is multiplied by X (step S003), and a coupled equation analysis is performed in the backward direction using only the backward pumping light to obtain P ｂｐ (0) is calculated (step S004). This allows the interaction between pump lights due to SRS to be taken into consideration to some extent. ｂｐ (0) and the boundary condition P ｓｉｇ (0) and perform a forward coupled equation analysis to obtain P ｂｐ(L) is obtained (step S005). ｂｐ (L) is used to evaluate the objective function (step S006).

[0039] The above process is repeated until the termination condition is met (note that, here, the termination condition is basically that X at which the objective function is minimized is found, but other termination conditions may be added). After the iterative calculation (L0s to L0e in FIG. 4) is completed, P when the objective function value is minimized is ｓｉｇ (z) and P ｂｐ (z) (step S007), and these values ​​are passed to the second stage of calculation.

[0040] The first-stage calculation converges quickly because the variable X is one-dimensional. Furthermore, the final X is not necessarily limited to the value that minimizes the objective function value within the search range, but may be the value that minimizes the objective function value. The objective function having a minimum value means that divergence of the power profile has been avoided. Therefore, an accurate power profile can be obtained in the second-stage calculation.

[0041] In the second stage of calculation, the analysis of the coupled equations and the updating of the power of the backward pumping light at the input end using an update formula based on perturbation approximation are repeated until an accurate power profile is converged. In the second stage, the frequency dependence of the pump depletion is taken into account, so the power profile converges to an accurate one. Furthermore, considering the frequency dependence increases the dimension of the update amount, which generally increases the calculation time, but using an update formula based on perturbation approximation speeds up the calculation.

[0042] Figure 6 shows the calculation flow of the second stage. Figure 7 shows the iterative calculation part (L1s to L1e in Figure 6). First, P ｂｐ ε for updating (0) ｂｐ (0) = [ε ｋ＋１ (0), ε ｋ＋２ (0), ..., ε Ｎ (0)] is calculated (step S101). ｂｐ (0) represents the error in the power of the backward pumping light at the input end of the optical fiber transmission line, and P ｓｉｇ (z) and P ｂｐ(z). The derivation of the calculation formula is shown below.

[0043] However, in the following, ε ｂｐ (0) = [ε １ (0), ε ２ (0), ..., ε ｋ This derivation method is similar to the method described in Patent Document 1, but the output terminal error ε ｂｐ (L) to the input terminal error ε ｂｐ This method differs from the method described in Patent Document 1 in that it calculates (0) and specifically describes the matrix used in the update equation. In addition, the technology described in Patent Document 1 does not aim to obtain a power profile, but aims to optimize the power of the pump light to achieve a desired Raman gain, which is also a major difference from the present embodiment.

[0044] Perturbation solutions of signal light and backward pumping light and P ｂｐ，ｐ (z) is expressed as in the following equations (4) and (5).

[0045]

[0046]

[0047] Here, P ｓｉｇ (z) and P ｂｐ (z) is the non-perturbative solution (same definition as in the first step), w ｐ ×ε ｓｉｇ (z) and w ｐ ×ε ｂｐ (z) corresponds to the perturbation term. ｐ is a weight to ensure that the perturbation term is sufficiently small relative to the non-perturbed solution, and is set so that the value of the objective function decreases with updating. By substituting equations (4) and (5) into equation (1), we obtain the equation for the perturbation term shown in equation (6) below.

[0048]

[0049] Here, the second-order perturbation term is ignored as its contribution is small. ｐ is a weight on the perturbation term (a parameter that adjusts the contribution to the non-perturbation solution), and therefore does not appear in the relational expression (6) for the perturbation term.

[0050] Using this, an N×N matrix A is defined as follows:

[0051]

[0052] where A(z) = (a ｉ，ｊ ), the following equations (8) and (9) are obtained. When i<N,

[0053]

[0054] When i<N,

[0055]

[0056] where ε ｉ (Z + dz) = (∂ε ｉ / ∂z)dz+ε ｉ (Z), and dz is the step size in the longitudinal direction of the optical fiber transmission line. In other words, P ｓｉｇ (z) and P ｂｐ (z) is the interval of z over which the calculation is performed. This gives the following equation (10):

[0057]

[0058] where E is an NxN identity matrix. B(z) = (b ｉ，ｊ ), the following equations (11) and (12) are obtained. When i<N,

[0059]

[0060] When i<N,

[0061]

[0062] Using B(z), the relationship of the non-perturbative terms between the input end and the output end of the optical fiber transmission line is expressed as in the following equation (13).

[0063]

[0064] Here, equation (13) is ｓｉｇ This is a calculation formula that includes (z), but here, ε ｂｐ Since only (0) is required, it is only necessary to calculate the following equation (14).

[0065]

[0066] In equation (14), B(z) is an (N−k)×(N−k) matrix. That is, ε ｓｉｇ (z) and ε ｂｐ B(z) corresponding to both (z) is an N × N matrix, but ε ｓｉｇ Using an (N−k) × (N−k) matrix obtained by excluding the elements of the 1st to kth rows and columns of B(z) corresponding to (z), ε ｂｐ Only calculations for (L) need to be performed. ｂｐ (L) is calculated using the following equation (15).

[0067]

[0068] Using equations (14) and (15), ε ｂｐ Calculate (0).

[0069] Returning to the explanation of FIG. 6, ε ｂｐ (0) as in equation (5) ｂｐ (0) is updated (step S102). ｂｐ (0) and P ｓｉｇ (0) and perform a forward coupled equation analysis to obtain P ｂｐ (L) is obtained (step S103). ｂｐ The value of the objective function is evaluated using (L) (step S104). Termination conditions are set such as the value of the objective function being equal to or less than a threshold value or the number of iterations exceeding a threshold value, and the above calculation is repeated until the termination conditions are met (L1s to L1e in FIG. 6).

[0070] After the iterative calculation is completed, the signal light power profile P ｓｉｇ (z) is output (step S105) and the process ends. ｐ The setting is important. ｐ If is too small, the amount of update of the power profile will be small, and it will be difficult to converge to an accurate power profile, and if is too large, the error in the power profile will increase.

[0071] According to this method, the multidimensional update quantity ε ｂｐ(0) can be obtained by one coupled equation analysis and one linear calculation of equation (14). On the other hand, ε ｂｐ When trying to find (0), approximately ε ｂｐ It is necessary to analyze the coupled equations the same number of times as the number of dimensions of (0). Therefore, by using the calculation method of this embodiment, it is possible to calculate the power profile more efficiently than when using the nonlinear least squares method.

[0072] Second Embodiment A second embodiment will now be described. In the second embodiment, the first stage of calculation is different from that in the first embodiment, but the second stage of calculation is the same as that in the first embodiment.

[0073] Figure 8 shows the calculation flow for the first stage. Figure 9 illustrates the iterative calculation part of the calculation flow. In both figures, parts (a), (b), (c), (d), and (e) correspond to each other. In the first embodiment, by analyzing the coupling equation in the backward direction of only the backward pumping light, P ｂｐ (L) to P ｂｐ In the second embodiment, however, P ｂｐ (L) to P ｂｐ (0) is obtained (that is, the process in step S204 differs from that in the first embodiment).

[0074] In the calculation method of the second embodiment, P ｂｐ (L) to P ｂｐ Although the interaction between the backward pumping lights is not taken into consideration when calculating (0), the number of times of analyzing the coupled equation can be reduced. Therefore, when the interaction between the pumping lights is small, the calculation method of the second embodiment can calculate the power profile more efficiently and accurately.

[0075] 10 shows a comparison of on-off Raman gain to confirm the effect of the calculation method of the embodiment. The on-off Raman gain is evaluated for the C+L band signal, and the results are compared between an experiment (plotted with circles), a calculation ignoring pump depletion (plotted with squares), and a calculation taking pump depletion into account (plotted with triangles, embodiment).

[0076] As shown in Fig. 10, the calculation ignoring the pump depletion has a large error from the experiment, whereas the calculation taking the pump depletion into account roughly matches the experiment, indicating that the power profile is accurately calculated in the calculation taking the pump depletion into account.

[0077] Four examples using the calculation method of the first or second embodiment will be described below. Example 1 is an example of a distributed Raman amplification characteristic analysis device using the calculation method of the first embodiment, Example 2 is an example of a distributed Raman amplification characteristic analysis device using the calculation method of the second embodiment, Example 3 is an example of a signal quality analysis device using the calculation method of the first embodiment, and Example 4 is an example of a signal quality analysis device using the calculation method of the second embodiment.

[0078] Example 1 Example 1 will be described below. Fig. 11 shows a distributed Raman amplification characteristic analysis device 1a using the calculation method of the first embodiment. Here, the distributed Raman amplification characteristics refer to various characteristics that can be calculated from the power profile of signal light. Specifically, the distributed Raman amplification characteristics include the distributed Raman amplification gain and the effective noise figure of the distributed Raman amplification. As shown in Fig. 11, the distributed Raman amplification characteristic analysis device 1a includes an input unit 11a, a distributed Raman amplification characteristic analysis unit 12a, and an output unit 14a.

[0079] The input unit 11a receives input of conditions and characteristics required for analysis, such as signal conditions (such as the frequency and power of each channel), optical fiber transmission line characteristics (such as loss and Raman gain coefficient), and Raman pump light conditions (such as frequency and power).

[0080] The distributed Raman amplification characteristic analyzer 12a calculates the power profile of the signal light using the calculation method of the first embodiment described above.

[0081] The output section 14a outputs the analyzed distributed Raman amplification characteristic, which may be fed back to the Raman pump light and used to optimize its operating conditions.

[0082] Example 2 Example 2 will now be described. Fig. 12 shows a distributed Raman amplification characteristic analysis device 1b using the calculation method of the second embodiment. As shown in Fig. 12, the distributed Raman amplification characteristic analysis device 1b includes an input unit 11b, a distributed Raman amplification characteristic analysis unit 12b, and an output unit 14b.

[0083] The configuration and input / output of the distributed Raman amplification characteristic analysis device 1b are similar to the configuration and input / output of the distributed Raman amplification characteristic analysis device 1a of the aforementioned Example 1. Example 2 differs from the aforementioned Example 1 in that the distributed Raman amplification characteristic analysis unit 12b calculates the power profile using the calculation method of the second embodiment.

[0084] Example 3 Example 3 will be described below. Fig. 13 shows a signal quality analysis device 1c using the calculation method of the first embodiment. Here, signal quality refers to, for example, SNR (Signal to Noise Ratio) characteristics. As shown in Fig. 13, the signal quality analysis device 1c includes an input unit 11c, a distributed Raman amplification characteristic analysis unit 12c, a signal quality analysis unit 13c, and an output unit 14c.

[0085] The input unit 11c accepts input of conditions and characteristics necessary for analysis, specifically, signal conditions (frequency and power of each channel, modulation format, etc.), optical fiber transmission line characteristics (loss, chromatic dispersion, nonlinear coefficient, Raman gain coefficient, etc.), Raman pump light conditions (frequency, power, etc.), optical amplifier characteristics (gain, noise figure, etc.), transceiver characteristics, etc.

[0086] The distributed Raman amplification characteristic analyzer 12c performs the same analysis as the distributed Raman amplification characteristic analyzer 12c of the first embodiment described above.

[0087] The signal quality analysis unit 13c performs signal quality analysis using the analyzed distributed Raman amplification characteristics and the input conditions and characteristics required for analysis.

[0088] For example, the signal quality analyzer 13c performs the following signal quality analysis on each WDM channel.

[0089] From the optical fiber transmission line characteristics, a Gaussian noise model is used to analyze signal distortion (NLI: Nonlinear interference) due to nonlinear optical effects in the optical fiber transmission line (signal power P ｓｉｇｎａｌ Noise power P ＮＬＩ (The power profile analyzed by the distributed Raman amplification characteristic analysis unit 12c is calculated.) The PNLI analysis is performed using the power profile analyzed by the distributed Raman amplification characteristic analysis unit 12c.

[0090] - Analyzes signal quality degradation due to amplified spontaneous emission (ASE) from optical amplifiers based on optical fiber transmission line characteristics and optical amplifier characteristics (signal power P ｓｉｇｎａｌ Calculate the noise power PASE for P ｓｉｇｎａｌ is determined by the power profile analyzed by the distributed Raman amplification characteristic analysis unit 12c.

[0091] Consider the signal quality limitations due to the characteristics of the transmitter and receiver as noise (signal power P ｓｉｇｎａｌ Noise power P ＴＸ／ＲＸ (Calculate the

[0092] Combining the above, the signal quality SNR (Signal to Noise Ratio) is calculated using the following equation (16).

[0093]

[0094] The output unit 14c outputs the analyzed signal quality of each channel. Based on this signal quality, gain equalization (signal power equalization) of WDM signals in a WDM (Wavelength Division Multiplexing) MUX (Multiplexer) and operating conditions of an optical amplifier and Raman pump light may be optimized.

[0095] Example 4 Hereinafter, Example 4 will be described. Fig. 14 shows a signal quality analysis device 1d using calculation procedure 2. As shown in Fig. 14, the signal quality analysis device 1d includes an input unit 11d, a distributed Raman amplification characteristic analysis unit 12d, a signal quality analysis unit 13d, and an output unit 14d.

[0096] The configuration and input / output of the signal quality analysis device 1d are similar to those of the signal quality analysis device 1c of the above-described Example 3. Example 4 differs from the above-described Example 3 in that the distributed Raman amplification characteristic analysis unit 12d calculates the power profile using the calculation method of the second embodiment.

[0097] As described above, in the embodiment of the present invention, the analysis device improves the convergence of the power profile by performing two-stage calculations. In the first stage of calculation, divergence of the power profile can be avoided without trial and error to find an appropriate input end backward pumping light power, which particularly improves the ease of calculation. In the second stage, an update formula based on perturbation approximation is used to efficiently converge to an accurate power profile.

[0098] That is, an analysis device according to an embodiment of the present invention is an analysis device that determines the power profile of signal light in an optical transmission system using distributed Raman amplification by analyzing coupled equations multiple times. The analysis device includes a first distributed Raman amplification characteristic analysis unit (not shown) that converges to a low-accuracy power profile while avoiding divergence based on the first-stage calculation method of the first embodiment (flow shown in FIG. 4 ) or the first-stage calculation method of the second embodiment (flow shown in FIG. 8 ), and a second distributed Raman amplification characteristic analysis unit (not shown) that converges to an accurate power profile by using an update equation based on perturbation approximation based on the second-stage calculation method (flow shown in FIG. 6 ).

[0099] With this configuration, the analysis device according to the embodiment of the present invention can efficiently calculate the accurate power profile of signal light in an optical transmission system using distributed Raman amplification, even when using backward pumping light. This enables accurate and efficient calculation of Raman amplification gain, effective noise figure, signal quality, etc. As a result, the analysis device according to the embodiment of the present invention contributes to improving the efficiency of system design that involves calculation of multiple conditions.

[0100] According to the above-described embodiment, the analyzer analyzes the power profile of signal light in an optical transmission system using distributed Raman amplification with backward pumping light. For example, the analyzer is a distributed Raman amplification characteristic analyzer 1a in the embodiment. The analyzer includes an input unit, an amplification characteristic analyzer, and an output unit. For example, the input unit is the input unit 11a in the embodiment, the amplification characteristic analyzer is the distributed Raman amplification characteristic analyzer 12a in the embodiment, and the output unit is the output unit 14a in the embodiment.

[0101] The input unit accepts input of information indicating signal conditions, characteristics of the optical fiber transmission line, and conditions of the Raman pump light. The amplification characteristic analysis unit calculates a power profile by iteratively calculating a coupled equation using the information input to the input unit, thereby analyzing the distributed Raman amplification characteristics. The output unit outputs information indicating the distributed Raman amplification characteristics analyzed by the amplification characteristic analysis unit. The amplification characteristic analysis unit includes a first analysis unit and a second analysis unit. The first analysis unit performs a first analysis process that converges to an approximate power profile while avoiding divergence. The second analysis unit performs a second analysis process that converges to a more accurate power profile by using an update equation based on perturbation approximation. The first analysis process converges to an approximate power profile by analyzing the coupled equation in the backward direction of only the backward pump light.

[0102] Furthermore, according to the above-described embodiment, an analysis device analyzes the power profile of signal light in an optical transmission system using distributed Raman amplification with backward pumping light. For example, the analysis device is the distributed Raman amplification characteristic analysis device 1b in the embodiment. The analysis device includes an input unit, an amplification characteristic analysis unit, and an output unit. For example, the input unit is the input unit 11b in the embodiment, the amplification characteristic analysis unit is the distributed Raman amplification characteristic analysis unit 12b in the embodiment, and the output unit is the output unit 14b in the embodiment.

[0103] The input unit accepts input of information indicating signal conditions, characteristics of the optical fiber transmission line, and conditions of the Raman pump light. The amplification characteristic analysis unit calculates a power profile by iteratively calculating a coupled equation using the information input to the input unit, thereby analyzing the distributed Raman amplification characteristics. The output unit outputs information indicating the distributed Raman amplification characteristics analyzed by the amplification characteristic analysis unit. The amplification characteristic analysis unit includes a first analysis unit and a second analysis unit. The first analysis unit performs a first analysis process that converges to an approximate power profile while avoiding divergence. The second analysis unit performs a second analysis process that converges to a more accurate power profile by using an update equation based on perturbation approximation. The first analysis process converges to an approximate power profile by taking into account only the loss of the optical fiber transmission line.

[0104] Furthermore, according to the above-described embodiment, an analyzer analyzes the power profile of signal light in an optical transmission system using distributed Raman amplification with backward pumping light. For example, the analyzer is the signal quality analyzer 1c in the embodiment. The analyzer includes an input unit, an amplification characteristic analyzer, a signal quality analyzer, and an output unit. For example, the input unit is the input unit 11c in the embodiment, the amplification characteristic analyzer is the distributed Raman amplification characteristic analyzer 12c in the embodiment, the signal quality analyzer is the signal quality analyzer 13c in the embodiment, and the output unit is the output unit 14c in the embodiment.

[0105] The input unit accepts input of information indicating signal conditions, optical amplifier characteristics, and transceiver characteristics. The amplification characteristic analysis unit calculates a power profile by iteratively calculating a coupled equation using the information input to the input unit, and analyzes distributed Raman amplification characteristics. The signal quality analysis unit analyzes signal quality by calculating the effects of signal distortion and noise in the optical transmission system based on the power profile calculated by the amplification characteristic analysis unit and the information input to the input unit. The output unit outputs information indicating the signal quality analyzed by the signal quality analysis unit. The amplification characteristic analysis unit includes a first analysis unit and a second analysis unit. The first analysis unit performs a first analysis process that converges to an approximate power profile while avoiding divergence. The second analysis unit performs a second analysis process that converges to a more accurate power profile by using an update equation based on perturbation approximation. The first analysis process converges to an approximate power profile by analyzing the coupled equation in the backward direction of only the backward pumping light.

[0106] Furthermore, according to the above-described embodiment, an analyzer analyzes the power profile of signal light in an optical transmission system using distributed Raman amplification with backward pumping light. For example, the analyzer is the signal quality analyzer 1d in the embodiment. The analyzer includes an input unit, an amplification characteristic analyzer, a signal quality analyzer, and an output unit. For example, the input unit is the input unit 11d in the embodiment, the amplification characteristic analyzer is the distributed Raman amplification characteristic analyzer 12d in the embodiment, the signal quality analyzer is the signal quality analyzer 13d in the embodiment, and the output unit is the output unit 14d in the embodiment.

[0107] The input unit accepts input of information indicating signal conditions, optical amplifier characteristics, and transceiver characteristics. The amplification characteristic analysis unit calculates a power profile by iteratively calculating a coupled equation using the information input to the input unit, and analyzes distributed Raman amplification characteristics. The signal quality analysis unit analyzes signal quality by calculating the effects of signal distortion and noise in the optical transmission system based on the power profile calculated by the amplification characteristic analysis unit and the information input to the input unit. The output unit outputs information indicating the signal quality analyzed by the signal quality analysis unit. The amplification characteristic analysis unit includes a first analysis unit and a second analysis unit. The first analysis unit performs a first analysis process that converges to an approximate power profile while avoiding divergence. The second analysis unit performs a second analysis process that converges to a more accurate power profile by using an update equation based on perturbation approximation. The first analysis process converges to an approximate power profile by taking into account only loss in the optical fiber transmission line.

[0108] The analysis device according to the embodiment of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network.

[0109] The analysis device of the above-described embodiment, and the distributed Raman amplification characteristic analysis devices 1a, 1b and signal quality analysis devices 1c, 1d in Examples 1 to 4 described above, may be implemented by a computer in part or in whole. In this case, a program for implementing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into a computer system and executed. Note that the term "computer system" as used herein includes hardware such as an OS and peripheral devices. Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, the term "computer-readable recording medium" may also include media that dynamically store programs for a short period of time, such as communication lines when transmitting programs via networks such as the Internet or communication lines such as telephone lines, and media that store programs for a certain period of time, such as volatile memory within the computer systems that serve as the server or client in such cases. Furthermore, the above program may be one that realizes part of the above-mentioned functions, or may be one that can realize the above-mentioned functions in combination with a program already recorded in a computer system, or may be one that is realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0110] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the present invention that do not deviate from the gist of the present invention.

[0111] 1a, 1b... distributed Raman amplification characteristic analyzer, 1c, 1d... signal quality analyzer, 11a to 11d... input section, 12a to 12d... distributed Raman amplification characteristic analyzer, 13c, 13d... signal quality analyzer, 14a to 14d... output section

Claims

1. An analysis device for analyzing the power profile of signal light in an optical transmission system using distributed Raman amplification with backward pumping light, comprising: an input unit that accepts input of information indicating signal conditions, characteristics of the optical fiber transmission line, and conditions of the Raman pumping light; an amplification characteristics analysis unit that calculates the power profile by iteratively calculating coupled equations using the information input to the input unit, and analyzes the distributed Raman amplification characteristics; and an output unit that outputs information indicating the distributed Raman amplification characteristics analyzed by the amplification characteristics analysis unit, wherein the amplification characteristics analysis unit comprises: a first analysis unit that performs a first analysis process that converges to an approximate power profile while avoiding divergence; and a second analysis unit that performs a second analysis process that converges to a more accurate power profile by using an update equation based on perturbation approximation, wherein the first analysis process converges to the approximate power profile by analyzing the coupled equations in the reverse direction of only the backward pumping light.

2. An analysis device for analyzing the power profile of signal light in an optical transmission system using distributed Raman amplification with backward pumping light, comprising: an input unit that accepts input of information indicating signal conditions, characteristics of the optical fiber transmission line, and conditions of the Raman pumping light; an amplification characteristics analysis unit that calculates the power profile by iteratively calculating a coupled equation using the information input to the input unit, and analyzes the distributed Raman amplification characteristics; and an output unit that outputs information indicating the distributed Raman amplification characteristics analyzed by the amplification characteristics analysis unit, wherein the amplification characteristics analysis unit comprises: a first analysis unit that performs a first analysis process that converges to an approximate power profile while avoiding divergence; and a second analysis unit that performs a second analysis process that converges to a more accurate power profile by using an update equation based on perturbation approximation, wherein the first analysis process converges to the approximate power profile by taking into account only the loss of the optical fiber transmission line.

3. An analysis device for analyzing the power profile of signal light in an optical transmission system using distributed Raman amplification with backward pumping light, comprising: an input unit that accepts input of information indicating signal conditions, optical amplifier characteristics, and transceiver characteristics; an amplification characteristics analysis unit that calculates the power profile by iteratively calculating coupled equations using the information input to the input unit and analyzes distributed Raman amplification characteristics; a signal quality analysis unit that analyzes signal quality by calculating the effects of signal distortion and noise in the optical transmission system based on the power profile calculated by the amplification characteristics analysis unit and the information input to the input unit; and an output unit that outputs information indicating the signal quality analyzed by the signal quality analysis unit, wherein the amplification characteristics analysis unit comprises: a first analysis unit that performs a first analysis process to converge to an approximate power profile while avoiding divergence; and a second analysis unit that performs a second analysis process to converge to a more accurate power profile by using an update equation based on perturbation approximation, wherein the first analysis process converges to the approximate power profile by analyzing the coupled equations in the reverse direction of only the backward pumping light.

4. An analysis device for analyzing the power profile of signal light in an optical transmission system using distributed Raman amplification with backward pumping light, comprising: an input unit that accepts input of information indicating signal conditions, optical amplifier characteristics, and transceiver characteristics; an amplification characteristics analysis unit that calculates the power profile by iteratively calculating coupled equations using the information input to the input unit and analyzes distributed Raman amplification characteristics; a signal quality analysis unit that analyzes signal quality by calculating the effects of signal distortion and noise in the optical transmission system based on the power profile calculated by the amplification characteristics analysis unit and the information input to the input unit; and an output unit that outputs information indicating the signal quality analyzed by the signal quality analysis unit, wherein the amplification characteristics analysis unit comprises: a first analysis unit that performs a first analysis process that converges to an approximate power profile while avoiding divergence; and a second analysis unit that performs a second analysis process that converges to a more accurate power profile by using an update equation based on perturbation approximation, wherein the first analysis process converges to the approximate power profile taking into account only loss in the optical fiber transmission line.

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