JP4960199B2 - Optical circuit design support apparatus, optical circuit design support program, and optical circuit design support method - Google Patents

Description

  The present invention relates to an optical circuit design support apparatus, an optical circuit design support program, and an optical circuit design support method that support optical circuit design such as calculating a distance that can be transmitted through an optical fiber.

In optical circuit design, for example, when calculating a distance that can be transmitted through an optical fiber, it is necessary to consider the influence of wavelength dispersion of the light source (light emitting element). When the optical fiber is SMF (Single Mode Fiber) and the wavelength range of the light source is wide, conventionally, the half-width of the emission spectrum (spectrum) is used to calculate the distance that can be transmitted by the following formula, for example. It was. Here, the emission spectrum is the intensity distribution of light according to the wavelength, and the half width is the width of two wavelengths that are half the intensity with respect to the peak value of the emission spectrum.
First formula: L ≦ 10 ³ / (4 × ρ × δλ × B)
Second formula: L ≦ 310 / (ρ × δλ × B) × 1 / 0.7
≈ (4.45 × 10 ² ) / (ρ × δλ × B)
L: Transmission distance (km)
B: Transmission speed (= frequency: Gb / s)
ρ: dispersion value at light wavelength of light source (ps / (nm · km))
δλ: half width of spectrum (nm)
There is also known an information processing system that allows a series of design work of an optical communication circuit to be executed in a form of interacting with the system without depending on a person who has design experience (see, for example, Patent Document 1).
JP 2007-114969 A

  By the way, even in the case of different emission spectra, the half-value widths may coincide, and in such a case, in the calculation using the half-value width as described above, the distance that can be transmitted is the same even for different emission spectra. End up. In other words, the emission spectrum characteristics are not expressed accurately (accurately) only with the half-value width, and the calculation using the half-value width as described above calculates the correct transmittable distance suitable for the emission spectrum characteristics. Can not do it. In particular, when the transmission speed is increased, subtle differences in the emission spectrum that cannot be expressed only by the half-value width affect the transmission quality. ) Cannot design. On the other hand, if a design that considers such a problem and considers a sufficient margin (safety) in the calculation result using the half width, an expensive and high-quality light-emitting element is used, or the transmission distance is shortened. It is necessary to do so, and the circuit design becomes uneconomical.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical circuit design support apparatus, an optical circuit design support program, and an optical circuit design support method that support performing an optical circuit design more suitable for the emission spectrum of a light source.

  In order to achieve the above object, the invention described in claim 1 includes an input means for inputting an emission spectrum of a light source, a transmission condition, and the like, an emission spectrum input by the input means, a transmission distance, a dispersion value, and a transmission speed. Processing means for analyzing the signal level after transmission of each wavelength of the emission spectrum in time series based on the transmission conditions including, and calculating the pulse value after transmission in time series from the analysis result. Is an optical circuit design support device characterized by

  According to a second aspect of the present invention, in the optical circuit design support apparatus according to the first aspect, the processing means graphs the calculated pulse value after transmission.

  According to a third aspect of the present invention, in the optical circuit design support device according to the first aspect, the processing means is based on the allowable pulse value input by the input means and the calculated pulse value after transmission. An error rate indicating a ratio of the post-transmission pulse value that is outside the allowable pulse value is calculated.

  According to a fourth aspect of the present invention, in the optical circuit design support apparatus according to the third aspect, the processing means is a transmission distance at which the calculated error rate becomes a maximum allowable error rate input by the input means. The maximum allowable transmission distance is calculated.

  The invention according to claim 5 is the signal level after transmission of each wavelength of the emission spectrum based on the emission spectrum of the light source input to the computer and the transmission conditions including the transmission distance, dispersion value and transmission speed. Is an optical circuit design support program for executing, in a time series, a first step of analyzing a time series of pulse values and a second step of calculating a pulse value after transmission in a time series from the analysis result of the first step. .

  The invention according to claim 6 analyzes the signal level after transmission of each wavelength of the emission spectrum in time series based on the emission spectrum of the light source and the transmission conditions including the transmission distance, dispersion value and transmission speed. An optical circuit design support method comprising: a first step; and a second step of calculating a post-transmission pulse value in time series from the analysis result of the first step.

  According to the first, fifth and sixth aspects of the invention, the signal level after transmission of each wavelength of the emission spectrum is analyzed in time series based on the emission spectrum of the light source and the transmission conditions, and the transmission is performed from the analysis result. Later pulse values are calculated in time series. That is, the post-transmission pulse value is calculated based on the characteristics of the emission spectrum itself, not the half width of the emission spectrum. For this reason, it is possible to design an optical circuit that is more suitable for the emission spectrum of the light source based on the pulse value after transmission, for example, to calculate a more accurate transmission distance.

  According to the invention described in claim 2, since the calculated pulse value after transmission is made into a graphic, the pulse (waveform) after transmission can be confirmed visually and more easily, and a more appropriate optical circuit design Makes it possible to do.

  According to the third aspect of the present invention, the error rate indicating the ratio of the post-transmission pulse value that is outside the allowable pulse value is calculated. Based on this error rate, the optical circuit design adapted to the emission spectrum of the light source Can be performed.

  According to the invention described in claim 4, since the maximum allowable transmission distance at which the error rate becomes the maximum allowable error rate is calculated, the light emission of the light source is performed by setting the maximum allowable error rate to a desired value (optimum value). It is possible to obtain a transmittable distance that is more suitable for the spectrum and that is suitable for a desired design tolerance (design concept).

  The present invention will be described below based on the illustrated embodiments.

  FIG. 1 is a schematic block diagram of an optical circuit design support apparatus 1 according to this embodiment. The optical circuit design support apparatus 1 is an apparatus that supports optical circuit design such as calculating a distance that can be transmitted through an optical fiber. The optical circuit design support apparatus 1 mainly includes an input unit (input unit) 11, a display unit 12, 1 task (processing means) 13, a second task (processing means) 14, and a CPU (Central Processing Unit) 15 for controlling them.

The input unit 11 inputs a light emission spectrum of a light source (light emitting element), transmission conditions, and the like, and includes a keyboard and a mouse. Here, the emission spectrum indicates the light intensity distribution according to the wavelength of the light source. As shown in FIG. 2, the center wavelength is the origin (zero) and the light output level is “1”. The optical output level Sλ for each wavelength deviation (wavelength difference) dλ from the center wavelength is shown. The emission spectrum may be input as an emission spectrum graph (curve) as shown in FIG. 2, or as shown in the G1 column of FIGS. 3 and 4, the level value (spectrum characteristic value) for each wavelength deviation dλ. ) Sλ may be input. Here, FIGS. 3 and 4 are spreadsheet sheets showing analysis, calculation results, and the like by the first task 13 described later. In addition, the following parameters are input as transmission conditions.
Transmission distance L
Variance ρ
Transmission speed f = frequency Maximum signal level Smax
Pulse identification level Sc
Here, the maximum signal level Smax is a value defining (specifying) the maximum value of the signal level, and the pulse identification level Sc is a value for specifying an allowable pulse value as will be described later. That is, in this embodiment, the allowable pulse value is indirectly input by inputting the pulse identification level.

  The display unit 12 is a display that displays analysis, calculation results (spreadsheet), pulse waveforms before and after transmission by a first task 13 described later.

The first task 13 is a task (an optical circuit design) that analyzes and calculates a pulse before transmission and a pulse after transmission based on the emission spectrum and transmission conditions input by the input unit 11, and compares and analyzes the two. Support program), which is based on the flowcharts shown in FIGS. Here, the case where the wavelength deviation dλ and the spectral characteristic value Sλ (the emission spectrum of FIG. 2) shown in the G1 column of FIGS. 3 and 4 are input as the emission spectrum, and the following parameter values are input as the transmission conditions. An example will be described. Further, the pulse value calculation cycle (pulse resolution) δt is set to 1 bit / 15 (1 / (transmission speed f × 15) = 667 ps).
Transmission distance L = 50km
Dispersion value ρ = 16.43 ps / (nm · km)
Transmission speed f = 100 Mb / s
Maximum signal level Smax = 1
Pulse identification level Sc = 50%
First, a pulse value (transmission pulse value) Ps before transmission is calculated in time series (step S1). That is, based on the transmission speed f and the pulse amplitude (maximum signal level) Smax input as the transmission conditions, the pulse value calculation is performed for an NRZ (Non Return to Zero) rectangular wave value that repeats the values “1” and “0”. Calculated for each cycle δt. Specifically, it is calculated by the following equation (first equation). Here, “t” in the equation is an elapsed time.
“1” when Ps = Smax × (sin (πft)> 0,
“0” when sin (πft) ≦ 0)
The pulse value Ps calculated in this way is input to the G3 column in FIG. 3 for each elapsed time t. Further, the elapsed time t is entered in the G2 column of FIG.

Next, the signal level Prλ after transmission of each component wavelength of the emission spectrum is analyzed in time series (first step). Specifically, first, the optical output level Sλ of the first component wavelength (wavelength deviation) dλ is acquired from the input emission spectrum (step S2). Here, the wavelength deviation dλ of “−0.2” is set as the first component wavelength, and the optical output level Sλ is acquired as “0.9877”. Then, the signal level Prλ after transmission at each elapsed time t is calculated (step S3). Specifically, it is calculated by the following equation (second equation).
“1” when Prλ = Sλ × (sin {2πf × (t + ρ × dλ × L)}>0;
sin {2πf × (t + ρ × dλ × L)} ≦ 0, “0”)
By this equation, a rectangular wave value having the light output level Sλ as a pulse amplitude is calculated, and (ρ × dλ × L) indicates a delay time from the center wavelength (a degree of spread of the pulse). The signal level Prλ after transmission calculated in this way is input to the corresponding wavelength deviation dλ in the G4 column of FIGS.

  Subsequently, when there is an optical output level Sλ of the next wavelength deviation dλ (in the case of “Y” in step S4), the optical output level Sλ is acquired (step S5), and each elapsed time of this wavelength deviation dλ is obtained. The signal level Prλ after transmission at t is calculated (step S6). Specifically, the signal level Prλ is calculated by the above second equation. In this way, the signal level Prλ after transmission of all the wavelength deviations dλ is analyzed and calculated.

Next, the post-transmission pulse value (reception pulse value) Pr is calculated in time series based on the analysis result of the first step (second step). First, a composite pulse value ΣPrλ at each elapsed time t is calculated (step S7). Specifically, the signal level Prλ after transmission of each wavelength deviation dλ at each elapsed time t is added up. Then, the calculated composite pulse value ΣPrλ is input to the G5 column in FIG. 3 for each elapsed time t. Subsequently, the pulse value Pr after transmission at each elapsed time t is calculated (step S8). This calculation is performed by converting the composite pulse value ΣPrλ to a value of 0 to Smax, and specifically, is calculated by the following equation (third equation).
Pr = Smax / MAX (ΣPrλ) × ΣPrλ
Here, MAX (ΣPrλ) means the maximum value of ΣPrλ (“12.71” in the example of FIG. 3). Then, the calculated post-transmission pulse value Pr is input in the G6 column of FIG. 3 for each elapsed time t.

Next, based on the input allowable pulse value (pulse identification level Sc) and the calculated post-transmission pulse value Pr, a bit error rate (error) indicating the ratio of the post-transmission pulse value Pr that is outside the allowable pulse value Rate) E is calculated. Here, the allowable pulse value indicates the maximum value or the minimum value of the post-transmission pulse value Pr that is allowed in optical circuit design (in terms of circuit quality), and the pre-transmission pulse value Ps is Smax (= 1). Smax × Sc (= 1 × 50% = 0.5) is the minimum allowable pulse value, and when the pulse value Ps before transmission is zero, Smax × Sc (= 0.5) is the maximum. Allowable pulse value. First, it is determined whether or not the post-transmission pulse value Pr at each elapsed time t is outside the allowable pulse value (whether or not) (step S9). That is, the determination is made as follows.
When the pulse value Ps before transmission is Smax,
If Pr ≧ Smax × Sc, “Yes”
“No” if Pr <Smax × Sc
When the pulse value Ps before transmission is zero,
“No” if Pr ≧ Smax × Sc
“Possible” if Pr <Smax × Sc
If it is determined as “No”, “Error” is input at the corresponding elapsed time t in the G7 column of FIG.

  Subsequently, the ratio of the number of “Error” to the total number of pulse values (Ps, Pr) is calculated as the bit error rate E (step S10). Then, the pre-transmission pulse value Ps calculated in step S1 and the post-transmission pulse value Pr calculated in step S8 are graphed (graphed) (step S11). That is, as shown in FIG. 7, the pulse waveform indicating the pulse value Ps before transmission at each elapsed time t and the pulse waveform indicating the pulse value Pr after transmission are superimposed.

  The second task 14 is a task for calculating a maximum allowable transmission distance Lmax, which is a transmission distance at which the bit error rate E calculated as described above becomes the maximum allowable error rate ES input at the input unit 11. 8 is based on the flowchart shown in FIG. Here, the maximum allowable error rate ES is the maximum value of the bit error rate E that is allowed in consideration of necessary line quality. The line importance of the optical fiber cable, the allowable value of the system using the line, etc. It is determined based on.

  First, steps S1 to S10 in the first task 13 are executed (step S21), and a bit error rate E according to the input emission spectrum and transmission conditions is calculated. Next, it is determined whether or not the calculated bit error rate E is the maximum allowable error rate ES (step S22). If the maximum allowable error rate ES is not the maximum allowable error rate ES ("Y" in step S23), the transmission distance L is shortened by a predetermined distance (step S24), and the process returns to step S21. The bit error rate E is recalculated. At this time, step S1 in the first task 13, that is, calculation of the pulse value Ps before transmission, is not affected by the transmission distance L, and therefore may not be executed.

  On the other hand, when the calculated bit error rate E is smaller than the maximum allowable error rate ES (in the case of “N” in step S23), the transmission distance L is extended by a predetermined distance (step S25), and the process returns to step S21 to return the bit. The error rate E is recalculated. When such a process is repeated and the calculated bit error rate E reaches the maximum allowable error rate ES (in the case of “Y” in step S22), the transmission distance L at that time is set as the maximum allowable transmission distance Lmax. (Step S26).

  Next, the operation of the optical circuit design support apparatus 1 having such a configuration and the optical circuit design support method by the optical circuit design support apparatus 1 will be described with reference to FIG.

  First, when the emission spectrum of the light source and the transmission conditions are input from the input unit 11 (steps S31 and S32) and the start command for the first task 13 is input, the first task 13 is started (step S33). 3 and 4 are displayed on the display unit 12, and the bit error rate E calculated as described above is displayed on the display unit 12 (step S34). The pulse values Ps and Pr (pulse waveform) before and after transmission, which are made into a graphic as described above, are displayed on the display unit 12 (step S35). Here, FIGS. 2 to 4 and FIG. 7 show examples of the emission spectrum graph (FIG. 2), spreadsheet (FIGS. 3 and 4), and pulse waveform (FIG. 7) when the bit error rate E is zero, respectively. FIGS. 10 to 13 respectively show an example of an emission spectrum graph (FIG. 10), a spreadsheet (FIGS. 11 and 12), and a pulse waveform (FIG. 13) when the bit error rate E is 4%. Then, based on the displayed bit error rate E and pulse waveform, it is determined whether or not the required line quality is satisfied (step S36). If not satisfied, the emission spectrum and transmission conditions are changed. Then, the first task 13 is activated again. In this way, the emission spectrum and transmission conditions are changed until the line quality is satisfied, and the emission spectrum and transmission conditions satisfying the required line quality are examined and acquired.

  Further, the maximum allowable transmission distance Lmax is acquired as follows. That is, as shown in FIG. 14, when the emission spectrum of the light source and the transmission conditions are input from the input unit 11 (steps S41 and S42) and the start command for the second task 14 is input, the second task 14 is started. (Step S43). Then, the maximum allowable transmission distance Lmax calculated as described above is displayed on the display unit 12 (step S44).

  As described above, according to the optical circuit design support device 1 and the optical circuit design support method, the post-transmission pulse value Pr is calculated based on the characteristics of the emission spectrum itself, not the half width of the input emission spectrum. The Therefore, based on the pulse value Pr after transmission, it is possible to examine in detail the influence of chromatic dispersion due to the emission spectrum characteristics that cannot be represented by the half width. That is, it is possible to calculate a more accurate transmittable distance suitable for the light emission spectrum of the light source, and to perform more detailed circuit design and examination, thereby making it possible to construct an economical facility.

  Moreover, since the pulse values Ps and Pr before and after the transmission are displayed on the display unit 12, the pulse waveforms before and after the transmission can be confirmed visually and easily (intuitively). Further, a bit error rate E is calculated and displayed. As a result, it is possible to perform more appropriate circuit design, for example, more appropriately determine whether or not the required line quality is satisfied in step S36. In addition, by starting the second task 14, the maximum allowable transmission distance Lmax at which the bit error rate E becomes the maximum allowable error rate ES is calculated, so the maximum allowable error rate ES is set to a desired value (optimum value). By doing so, it is possible to acquire the transmittable distance Lmax that matches the emission spectrum of the light source and that is suitable for a desired design tolerance (design concept).

  Although the embodiment of the present invention has been described above, the specific configuration is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention, the present invention is not limited to this embodiment. include. For example, in the above embodiment, the pulse identification level Sc is directly input as the transmission condition, but the pulse identification level Sc is determined in advance according to the line importance and the line importance is input as the transmission condition. The pulse identification level Sc may be set by (indirect input). As a result, it is possible to design an optical circuit more easily and appropriately by only considering the importance of the line without considering the meaning of the numerical value of the pulse identification level Sc.

1 is a schematic block diagram of an optical circuit design support device according to an embodiment of the present invention. It is a figure which shows the 1st example of the light emission spectrum graph input with the optical circuit design assistance apparatus of FIG. It is a figure which shows the 1st example of the spreadsheet sheet produced by the optical circuit design support apparatus of FIG. It is a figure which shows the continuation of the spreadsheet sheet of FIG. 3 is a flowchart of a first task of the optical circuit design support apparatus of FIG. 1. It is a flowchart following the flowchart of FIG. It is a figure which shows the 1st example of the pulse waveform produced by the 1st task of FIG. 4 is a flowchart of a second task of the optical circuit design support device of FIG. 1. 2 is a flowchart showing an operation of the optical circuit design support apparatus of FIG. It is a figure which shows the 2nd example of the emission spectrum graph input with the optical circuit design assistance apparatus of FIG. It is a figure which shows the 2nd example of the spreadsheet sheet produced by the optical circuit design assistance apparatus of FIG. It is a figure which shows the continuation of the spreadsheet sheet of FIG. It is a figure which shows the 2nd example of the pulse waveform produced by the 1st task of FIG. 6 is a flowchart when a maximum allowable transmission distance is acquired by the optical circuit design support device of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical circuit design support apparatus 11 Input part (input means)
12 Display unit 13 First task (processing means)
14 Second task (processing means)
15 CPU
Ps Pulse value before transmission Pr Pulse value after transmission Prλ Signal level after transmission

Claims (6)

Input means for inputting the emission spectrum of the light source and transmission conditions;
Based on the emission spectrum input by the input means and the transmission conditions including transmission distance, dispersion value and transmission speed, the signal level after transmission of each wavelength of the emission spectrum is analyzed in time series, and the analysis result Processing means for calculating the pulse values after transmission from the time series,
An optical circuit design support device comprising:   The optical circuit design support apparatus according to claim 1, wherein the processing unit graphs the calculated pulse value after transmission.   The processing unit calculates an error rate indicating a ratio of the post-transmission pulse value that is outside the allowable pulse value based on the allowable pulse value input by the input unit and the calculated post-transmission pulse value. The optical circuit design support apparatus according to claim 1.   4. The optical circuit design support according to claim 3, wherein the processing means calculates a maximum allowable transmission distance, which is a transmission distance at which the calculated error rate becomes a maximum allowable error rate input by the input means. apparatus. On the computer,
A first step of analyzing a signal level after transmission of each wavelength of the emission spectrum in time series based on an input emission spectrum of the light source and a transmission condition including a transmission distance, a dispersion value, and a transmission speed;
A second step of calculating a pulse value after transmission in a time series from the analysis result of the first step;
Optical circuit design support program for executing A first step of analyzing a signal level after transmission of each wavelength of the emission spectrum in time series based on an emission spectrum of the light source and a transmission condition including a transmission distance, a dispersion value, and a transmission speed;
A second step of calculating a pulse value after transmission in a time series from the analysis result of the first step;
An optical circuit design support method comprising:

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