JP2003204302A - Wdm signal monitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a WDM signal monitor capable of accurately measuring a modulated WDM signal. <P>SOLUTION: The monitor comprises a spectrophotometer for measuring the spectrum of a WDM signal, a response characteristic data memory for storing response characteristic data for the line spectrum of an optical signal from the spectrophotometer, a corrector for obtaining correction data upon input of properties of the WDM signal inputted to the spectrophotometer, based on the properties of the WDM signal and the response characteristic data in the response characteristic data memory, a correction data memory for storing correction data obtained by the corrector, and an arithmetic unit for computing at least the optical signal level of the WDM signal, based on the spectrum measured by the spectrophotometer and the correction data in the correction data memory. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a WDM (waveleng).
th division multiplexing: A WDM monitor that measures an optical signal level of a signal, an optical SNR (signal to noise ratio), and the like, and more specifically, accurately measures a modulated WDM signal. W that can be done
The present invention relates to a DM signal monitor.

[0002]

2. Description of the Related Art WDM communication is one type of optical communication system for transmitting an optical signal through an optical fiber. This WDM communication is a communication system in which a plurality of optical signals having different wavelengths are transmitted by one optical fiber. Further, a plurality of optical signals having different wavelengths are also called WDM signals. And WD
Each optical signal of the M signal is often counted as one channel or two channels from the short wave side, for example.

In recent years, high-density multiplexing of WDM signals has progressed as the transmission capacity has expanded, and the optical signal level of each channel
Peak wavelength, optical SNR, etc. are important measurement parameters. And monitoring these parameters is essential to maintain the quality of the WDM signal. W
The DM signal monitor uses a wavelength dispersion element to disperse the measured light that is a WDM signal for each wavelength, obtains the optical power existing in an arbitrary wavelength width, and measures these parameters from the obtained optical power. It is a device to perform. Some WDM signal monitors are configured using, for example, a small spectroscope so that they can be incorporated in a part of an optical communication system in an in-line format and constantly monitored.

FIG. 7 is a block diagram showing an embodiment of a WDM signal monitor for measuring such a WDM signal. In FIG. 7, the spectroscope 10 is a WDM that is the measured light.
A signal is input, the spectrum of this WDM signal is measured, and measurement data Po (i) that is sampling data (where i = 1 to m, both i and m are integers) is output. The response characteristic data storage unit 20 stores the response characteristic data of the spectroscope 10 for the line spectrum.

The measurement data Po (i) output from the spectroscope 10 is input to the arithmetic unit 30. In addition, the calculation unit 30
Reads the response characteristic data from the response characteristic data storage unit 20. Then, the calculation unit 30 calculates the optical signal level and the peak wavelength of each channel based on the measurement data and the response characteristic data, and outputs the calculation results.

FIG. 8 is a diagram showing an example of response characteristics of the response characteristic data f (Δλ) stored in the response characteristic data storage section 20 in FIG. In FIG. 8, when a line spectrum is input to the spectroscope 10, the response characteristic to this input is a response spectrum having a spread like a Gaussian distribution near the peak. Response characteristic data f (Δλ) is obtained by normalizing this response spectrum, and becomes a function f (Δλ) represented by the output values of wavelength and optical power. Here, Δλ indicates the wavelength difference from the peak wavelength, and the wavelength difference Δλ
F (0) when = 0 is the maximum value of this function. The response characteristic data f (Δλ) is obtained off-line and stored in the response characteristic data storage unit 20.

FIG. 9 is a block diagram showing a concrete example of the spectroscope 10. Here, as the method of the spectroscope 10, a polychromator method, which can be easily downsized, is mentioned. In FIG. 9, a spectroscope 10 includes an optical fiber 11, a collimating lens 12, a diffraction grating 13 which is a wavelength dispersion element, a focusing lens 14, a photodiode array module (hereinafter abbreviated as PDM) 15, an optical shutter 16, and depolarization. It is composed of the element 17.

The optical fiber 11 is a transmission line through which the measured light 100 is incident on the spectroscope 10. The collimating lens 12 is installed so as to face the emission port of the optical fiber 11 and collimates the measured light 100 emitted from the optical fiber 11 and emits it.

The diffraction grating 13 is installed so as to be tilted with respect to the collimating lens 12 in order to diffract the light emitted from the collimating lens 12 to a desired angle. Further, the diffraction grating 13 disperses the measured light 100 at different angles for each wavelength and emits the light. The focusing lens 14 is
It is installed on the optical path of the emitted light from the diffraction grating 13 and converges the emitted light.

The PDM 15 is installed at a position where the measured light 100 converges. The PDM 15 is provided with a PD array in which a plurality of photodiodes (hereinafter abbreviated as PD), which are strip-shaped or dot-shaped light receiving elements, are arranged. This P
At D, a current (photocurrent) corresponding to the optical power of the incident measured light 100 is generated. The PDM 15 sequentially outputs the photocurrent of the PD from the PD on the short wavelength side, for example.

A wavelength is assigned to each PD in advance. The wavelength allocation corresponds to the position where the measured light 100 is spectrally separated by the diffraction grating 13 for each wavelength and converges in the PD array.

The optical shutter 16 is provided between the optical fiber 11 and the collimating lens 12, and the measured light 1
00 can be blocked. The optical shutter 16 blocks the light to be measured 100, measures the dark current level of the PD at that time, and subtracts this value from the measurement data of the light to be measured 100, so that the influence of the dark current drift can be eliminated, and the high Accurate measurement can be realized.

The depolarizing element 17 is provided between the collimating lens 12 and the diffraction grating 13 and is provided with the measured light 10
By transmitting 0, it is possible to remove the polarization dependence particularly in the diffraction grating 13.

The operation of such a spectroscope 10 will be described.
It is assumed that the measured light 100 has wavelengths λA and λB different from each other. The light under measurement 100 emitted from the optical fiber 11 is collimated by the collimating lens 12. The measured light 100 that has passed through the collimating lens 12 passes through the depolarizer 17 and the diffraction grating 13
Incident on. The measured light 100 is reflected by the diffraction grating 13.
The wavelengths λA and λB are split into measured lights 100A and 100B. Light under measurement 1 split by the diffraction grating 13
00A and 100B are converged on the PD array of the PDM 15 by the focusing lens 14, but the converged positions are shifted corresponding to the wavelengths λA and λB of the measured lights 100A and 100B.

The photocurrent generated in each PD is sequentially output from the PD on the short wavelength side. The conversion unit not shown is P
The photocurrent output from D is converted into a voltage. Further, since the signal converted into this voltage is an analog signal, the conversion unit converts this analog signal into a digital signal, and the measured data P
It is output to the arithmetic unit 30 as o (i). In this way, the measurement data Po (i) is sampling data sampled by the PD.

Next, the operation of the arithmetic unit 30 for obtaining the optical signal level and peak wavelength of each channel will be described in detail. FIG. 10 is a diagram schematically showing an example in which the PD of the PDM 15 shown in FIG. 9 has a strip shape, and a part of the PD array is irradiated with the measured light 100A. In FIG. 10, the PDs 15a to 15e are arranged along the direction in which the measured light 100 is separated into wavelengths λA and λB by the diffraction grating 13. Further, wavelengths λ _{a to} λ _e (λ _a <λ _b <... <λ _e ) are assigned to the PDs 15 _{a to} 15 _e , respectively.

The PD array is a PD 15a in which a photocurrent is generated.
~ 15e are not lined up in the arrangement direction without a gap,
In the arrangement direction, the PD 15a having the width Δp, the dead zone having the width Δq,
PD15b having a width Δp is formed as
The width of the pitch is the sum of the width Δp of each PD 15a to 15e and the dead zone width Δq. In addition, PD15a ~
15e each have a width Δp, but generally PD
The central position of the arrangement direction of 15a to 15e is made to correspond to each of the allocated wavelengths λ _{a to} λ _e . Then, the distance on the PD array (for example, width Δp, width Δq
Etc.) is the wavelength λ assigned to each PD 15a to 15e.
_The wavelength can be converted by _{a to} λ _e .

A photocurrent is output from one or both sides of the PDs 15a to 15e by a signal line (not shown).

When the measured light 100A has a line spectrum such as a laser beam, the measured light 1 formed on the PD array 1
The 00A light spot has an elliptical or circular shape in which the optical power has a Gaussian distribution. The light spot is a portion where the light power is 1 / e ² times the light peak power, and the distance from the center of the light spot to the circumference is
The beam radius becomes ω. And this light spot is PD
It is set equal to or wider than the pitch of the array. That is, the measured light 100A is sampled by the PDs 15a to 15e having a wavelength width narrower than the spread of the light spot on the wavelength axis.

The center of the measured light 100A is PD1.
It is assumed to be near 5c. FIG. 11 shows a part of the measurement data Po (i) output from the PDM 15 (PD 15a to 15a).
It is a figure showing e). The horizontal axis represents each PD 15a to 15e
Of wavelengths λ _a to λ _e assigned to
The outputs of 5a to 15e are relatively represented. Where each P
The D15a~15e respective outputs and _P a to P _e.
Since the center of the measured light 100A is near the PD 15c,
The output P _{c of the} PD 15c is the other outputs P _a , P _b , P _d , P
Obviously, it is larger than _e . Further, the wavelength difference [Delta] [lambda] _{P D} between adjacent PD, is obtained by converting the width of the PD array one pitch to the wavelength.

The response of the spectroscope 10 to the line spectrum input to the spectroscope 10 is approximated by a Gaussian distribution, and the peak wavelength λ _peak of the measured light 100A can be expressed by the equation (1). λ _peak = λ ₀ + δλ (1) where λ ₀ is the wavelength λ _c assigned to the PD 15c closest to the optical peak power, and δλ is the peak wavelength λ
_It shows the wavelength difference between the _peak and the wavelength λ _c assigned to the PD 15c closest to the optical peak power. Further, the wavelength difference δλ is obtained by converting the relative shift amount δx, which indicates the shift between the center of the PD 15c and the center of the light spot of the measured light 100A in FIG. 10, into a wavelength.

The relative shift amount δx is determined by the PD 15c closest to the center of the light spot of the measured light 100A and the PDs 15 on both sides thereof.
It can be expressed by the equation (2) from the output ratio of b and 15d.

[0023]

[Equation 1] Here, _{P 0} corresponds to the output _{P c} of the optical peak power closest _{PD15c, P} - _{1, P +1,} respectively _P b,
Corresponds to P _d .

The wavelength difference Δλ can be expressed by the equation (3).

[Equation 2]

Optical signal level P _sig of measured light 100A
Is the integral of the spectrum spread on the PD array or near the optical peak power, for example, three PD15 near the peak.
It can be obtained from the sum of the output values P _{b to} P _d of _{b to} 15 _d . However, since the PD array has a dead zone, even if the optical signal level is the same, P is determined by the relative shift amount δx.
The added values of D15b to 15d are not the same.

FIG. 12 is a graph showing the relationship between the relative shift amount δx and the added values of the PDs 15b to 15d near the peak. In FIG. 12, the horizontal axis represents the relative shift amount δx and the vertical axis represents the relative power fluctuation. The unit is the pitch of the PD array and the logarithm (dB), and the curve of the graph is obtained from the response characteristic data f (Δλ). If the correction function α (δx) that corrects the relative power fluctuation is obtained from this graph, the optical signal level P _Sig of the measured light 100A can be accurately calculated by the equation (4). P _sig = α (δx) · (P ₋₁ + P ₀ + P ₊₁ ) (4)

Therefore, the calculation unit 30 determines the measurement data Po.
(I) and the wavelength λ assigned to each PD 15a to 15e
_{From a to} λ _e , the measured light 10 is calculated by the equations (1) to (3).
Determine the peak wavelength of 0A. Further, the calculation unit 30 calculates the equation (2) from the measured data Po (i) and the pitch width of the PD array.
The relative shift amount δx is calculated by the following formula, this relative shift amount is substituted into the correction function α (δx) for correcting the optical power, and the optical signal level of the measured light 100A is obtained by the formula (4).

The operation of the arithmetic unit 30 to obtain the optical signal level and the peak wavelength of the measured light 100B which is the other channel is also the same, and the description thereof will be omitted. Then, the arithmetic unit 30
Outputs the calculation result to an output unit (not shown), and the output unit displays the calculation result on the screen of the display unit or outputs it to an external device (not shown).

[0029]

The WDM signal is modulated and transmitted for each channel. In recent years, various modulation methods have been adopted with the increase of transmission distance and transmission speed in communication systems. Is being considered. As an example of a modulation method, in order to avoid chromatic dispersion and non-linear effects of an optical fiber, an optical carrier frequency component is suppressed and an occupied wavelength range is narrowed.
ero) modulation, SSB using only one sideband
There are RZ (signale side band return to zero) modulation and the like. In addition, the modulation speed is generally set to exceed 10 Gbps.

When such modulation is carried out, the spectrum of each channel becomes a plurality of line spectra due to the generation of a plurality of sidebands with respect to the carrier. The shape of the response spectrum of the spectroscope 10 in this modulated optical signal is a superposition of the response spectra of the carrier and sideband line spectra. As a result, the shape of the response characteristic data f (Δλ) in the response characteristic data storage unit 20 is significantly different from the shape of the response spectrum of the spectroscope 10 for the modulated optical signal. Therefore, in the correction function α (δx) obtained from the response characteristic data f (Δλ), the effect of correcting the optical power with respect to the relative shift amount δx decreases.

An object of the present invention is to realize a WDM signal monitor capable of accurately measuring a modulated WDM signal.

[0032]

The invention according to claim 1 is
The spectroscope for measuring the spectrum of the WDM signal, the response characteristic data storage section for storing the response characteristic data for the line spectrum of the optical signal of the spectroscope, and the characteristic of the WDM signal input to the spectroscope are input. An adjustment unit for obtaining correction data based on the characteristics of the WDM signal and the response characteristic data in the response characteristic data storage unit; and a correction data storage unit for storing the correction data obtained by the adjustment unit,
It has a calculating part which calculates at least the optical signal level of the WDM signal based on the spectrum measured by the spectroscope and the correction data of the correction data storage part.

According to a second aspect of the present invention, in the first aspect of the invention, the spectroscope measures the sampling data on the wavelength axis with a narrower wavelength width than the spread of the response spectrum with respect to the line spectrum. It is a feature.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the invention described above, the spectroscope is characterized by having a wavelength dispersion element that disperses a WDM signal and a photodiode array including a plurality of photodiodes that receive the dispersed light.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the adjusting section includes a modulation system for modulating the WDM signal and a multiplexing component for multiplexing or demultiplexing the WDM signal. W which is at least one of the optical filter characteristics of the wave filter
It is characterized in that the correction data is obtained from the characteristics of the DM signal.

According to a fifth aspect of the invention, in the invention according to any one of the first to fourth aspects, the adjusting section is corrected based on the response characteristic data in the response characteristic data storage section and the characteristic of the WDM signal. It is characterized in that correction data which is at least one of the response characteristic data and the optical power correction data for correcting the optical power obtained from the corrected response characteristic data is obtained.

According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, at least one of the response characteristic data storage section and the adjusting section is connected during adjustment. is there.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the first embodiment of the present invention. Here, the same parts as those in FIG. 7 are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 1, the adjustment unit 4
0 is provided between the response characteristic data storage unit 20 and the calculation unit 30, and has an input unit 41 and a correction unit 42. The adjustment unit 40 creates and outputs correction data based on the response characteristic data from the response characteristic data storage unit 20 and the characteristic of the WDM signal from the outside.

The input means 41 receives the characteristics of the WDM signal input to the spectroscope 10 from the outside. The characteristics of the WDM signal are, for example, a modulation method (including a modulation speed) for modulating the WDM signal, an optical filter characteristic of a multiplexer / demultiplexer for multiplexing or demultiplexing the WDM signal, and the like. The correction means 42 is
Response characteristic data f (Δλ) of the response characteristic data storage unit 20
Of the WDM signal input by the input means 41. Then, based on the characteristics of the read WDM signal and the response characteristic data f (Δλ), correction data is created and output.

The correction data storage unit 50 is provided between the response characteristic data storage unit 20 and the calculation unit 30, receives and stores the correction data of the adjustment unit 40, and outputs the correction data to the calculation unit 30.

The operation of the apparatus shown in FIG. 1 will be described with reference to the flowchart of FIG. WD by input means 41
The characteristics of the M signal are input. This input is performed at the time of adjustment, for example, before the device shown in FIG. 1 operates in the communication system, or when the characteristics of the WDM signal input to the spectrometer 10 from the communication system are changed. (S11).

The correction means 42 comprises the response characteristic data storage unit 2
The response characteristic data f (Δλ) of 0 is read, the characteristic of the WDM signal input by the input means 41 is read (S12), and the correction data is created based on the characteristic of the WDM signal and the response characteristic data f (Δλ). (S13).

Here, based on the characteristics of the WDM signal input by the input means 41 and the response characteristic data f (Δλ) of the response characteristic data storage section 20, the correcting means 42 specifically obtains the correction data of the spectroscope 10. An example will be described with reference to FIG. Here, it is assumed that the WDM signal is subjected to SSB-RZ modulation and the optical filter characteristic can be ignored. Since the SBS-RZ modulation is performed on the measured light 100, the correction unit 42 estimates the sideband 201 composed of a plurality of line spectra generated by the modulation with respect to the carrier 200 composed of a single line spectrum. , The input spectrum to the spectroscope 10 is obtained.

The response spectrum (corrected response characteristic data) 202 of the spectroscope 10 with respect to the input spectra 200 and 201 is a response spectrum similar to the response characteristic data f (Δλ) (broken line in FIG. 3) for each line spectrum. ) Is a shape that is superimposed. That is, no matter how complicated modulation is performed, the modulated input spectra 200 and 201 can be approximated by a plurality of line spectra,
Furthermore, the response spectrum for the input spectra 200 and 201 is wavelength Δλ based on the response characteristic data f (Δλ).
It can be represented by a function g (Δλ) having as a parameter.

Further, from the response characteristic data g (Δλ) corrected by the correction means 42, the relation between the relative deviation amount δx and the added value of PD near the peak can be obtained. Figure 4
Is the relative shift amount δx in the modulated signal, and P
It is a figure showing an example of the relation of the added value of D. In FIG. 4, the vertical axis and the horizontal axis are the same as in FIG. From this graph, the correction function G (δx) for correcting the optical power of the modulated signal can be obtained.

In FIG. 2, the correction means 42 stores the obtained correction function G (δx) in the correction data storage section 50 as correction data (S14). Incidentally, the operation of the correction means 42 creating the correction data and storing the correction data in the correction data storage unit 50 (S12 to S1).
4) is performed every time adjustment is made when the characteristic of the WDM signal is input by the input means 41.

The spectroscope 10 measures the spectrum of the WDM signal and outputs the measurement data Po (i) to the arithmetic unit 30 (S15). The calculation unit 30 calculates the measurement data Po (i).
Then, the peak of each channel is detected and the relative shift amount δx is obtained for each channel (S16). The calculation unit 30 reads the correction data G (δx) from the correction data storage unit 50 (S17), and uses the correction data G (δx) instead of the correction function α (δx) in the equation (4) for each channel. The optical signal level of is calculated and the calculation result is output (S1
8).

As described above, based on the characteristics of the WDM signal input by the input means 41, the correction means 42 causes the spectroscope 1
The input spectrum input to 0 is obtained. Then, the response characteristic data f (Δλ) is corrected from the response characteristic data f (Δλ) of the response characteristic data storage unit 20 and the obtained input spectrum, and the relative deviation amount is calculated from the corrected response characteristic data g (Δλ). The correction data G (δx) for correcting the fluctuation of the optical power due to δx is obtained. The calculation unit 30 calculates the optical signal level using the correction data G (δx). As a result, even if the measured lights 100A and 100B are optical signals that have been modulated, the optical signal level can be accurately calculated.

FIG. 5 is a block diagram showing the second embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals,
The description is also omitted. In FIG. 5, the correction data storage unit 60
Is provided in place of the correction data storage unit 50 and stores the correction data output from the adjustment unit 40.

The calculation unit 70 is provided in place of the calculation unit 30, and the measurement data Po (i) output from the spectroscope 10 is provided.
Is entered. The calculation unit 70 reads the correction data from the correction data storage unit 70. Then, the calculation unit 70 determines the SNR
It has a calculating means 71, and the SNR calculating means 71 obtains an optical signal level and an optical SNR for each channel. Then, the calculation unit 70 outputs these calculation results. Here, the optical SNR is defined by the equation (5). Optical SNR = 10 · log (optical signal level / optical noise level) (5)

The operation of the apparatus shown in FIG. 5 will be described with reference to the flowchart of FIG. WD by input means 41
The characteristics of the M signal are input. This input is performed at the time of adjustment, for example, before the device shown in FIG. 5 operates in the communication system, or when the characteristics of the WDM signal input to the spectrometer 10 from the communication system are changed. (S21).

The correction means 42 comprises the response characteristic data storage unit 2
The response characteristic data f (Δλ) of 0 is read out, the characteristic of the WDM signal input by the input means 41 is read out (S22), and the correction data is created based on the characteristic of the WDM signal and the response characteristic data f (Δλ). (S23).
However, the correction data is corrected by the correction means 4 in the apparatus of FIG.
2 becomes the corrected response characteristic data g (Δλ). Then, the correction unit 42 stores the correction data in the correction data storage unit 60 (S24). Incidentally, the correction means 4
2 creates the correction data and stores the correction data in the correction data storage unit 60 (S22 to S24)
Is performed every time the characteristic of the WDM signal is input by the input unit 41.

The spectroscope 10 measures the spectrum of the WDM signal and outputs the measurement data Po (i) to the arithmetic unit 70 (S25). The calculation unit 70 measures the measurement data Po (i).
Then, N peaks of each channel (where N <m and N is an integer) are detected (S26), and the correction data g (Δλ) of the correction data storage unit 60 is read (S27). The SNR calculation means 71 uses the optical signal level Ps (k) of each channel (where k = 1 to N and k is an integer) and the optical noise level Pn.
With (k) as an unknown number, these unknown numbers are obtained from the simultaneous equations shown in equation (6) using the correction data g (Δλ) and the measurement data Po (i) (S28).

[0054]

[Equation 3] Here, Fs _k and Fn _k are approximate expressions for obtaining parameters corresponding to the optical signal level Ps (k) and the optical noise level Pn (k) from the measurement data Po (k), and the matrix M is
This is a matrix determined by Fs _k , Fn _k, and correction data g (Δλ).

Then, the SNR calculating means 71 calculates the optical SNR from the optical signal level Ps (k) and the optical noise level Pn (k) by the equation (5), and outputs the optical signal level Ps.
(K), the calculation result of the optical SNR or the like is output (S29).

As described above, based on the characteristics of the WDM signal input by the input unit 41, the correction unit 42 determines that the spectroscope 1
The input spectrum input to 0 is obtained. Then, the response characteristic data f (Δλ) is corrected from the response characteristic data f (Δλ) of the response characteristic data storage unit 20 and the obtained input spectrum. The calculation unit 30 uses the corrected response characteristic data g (Δλ) to determine the optical signal level Ps (k) and the optical SN.
Calculate R. As a result, the measured lights 100A, 100
Even if B is a modulated optical signal, the optical signal level Ps (k) and the optical SNR can be accurately calculated.

The present invention is not limited to this, and may be as follows. The spectroscope 10 uses the fixed diffraction grating 13 and PDM 15 to measure the light 1 to be measured.
Although the configuration for sampling the spectrum of 00 is shown, the diffraction grating 13 is rotated forward and backward in the wavelength dispersion direction, and
Instead of M15, a slit and a PD for receiving the transmitted light transmitted through this slit may be provided. However, the width of the slit is set to be narrower on the wavelength axis than the spread of the response spectrum with respect to the line spectrum. In this configuration, the wavelength dispersion element rotates in the forward and reverse directions to sweep the wavelength of the measured light 100, sample the light having the wavelength transmitted through the slit in time series, and output the measurement data Po (i). It

Although the polychromator type spectroscope has been described, all spectroscopes configured to disperse the measured light 100 and sample the spectroscopic spectrum are included in the present invention.

The measured light 100 has wavelengths λA and λB.
Although the example in which the two channels are multiplexed is shown, any number of channels may be multiplexed.

Further, although the example in which the diffraction grating 13 is used as the wavelength dispersion element is shown, a prism or the like may be used.

Although the spectroscope 10 is a transmission type optical system using the lenses 12 and 14, it may be a reflection type optical system using a parabolic mirror or the like.

Further, the apparatus shown in FIG. 5 is configured to store the corrected response characteristic data g (Δλ) as the correction data in the correction data storage unit 60, but the corrected response characteristic data g (Δλ) is stored. , The correction function G (δx) may be stored. Specifically, the optical signal level Ps (k) of each channel may be previously calculated by the correction function G (δx), and the unknowns may be the optical noise level Pn (k) alone to solve the simultaneous equations. This allows
The unknown number of simultaneous equations can be reduced and the calculation time can be shortened.

Further, at least one of the response characteristic data storage section 20 and the adjusting section 40 may be connected to the apparatus shown in FIG. 1 or 5 only at the time of adjustment.
As a result, it is not necessary to prepare the response characteristic data storage unit 20 and the adjusting unit 40 for each device shown in FIGS. Therefore, the cost can be reduced, and the installation space can be reduced when the system is installed.

[0064]

The present invention has the following effects. According to the first to sixth aspects, the adjusting unit obtains the input spectrum input to the spectroscope from the characteristic of the WDM signal, and obtains the correction data based on the response characteristic data of the response characteristic data storage unit and the obtained input spectrum. The calculation unit calculates at least the optical signal level based on the spectrum measured by the spectroscope and the correction data, and performs measurement. Thereby, the modulated WDM signal can be accurately measured.

According to the sixth aspect, since at least one of the response characteristic data storage section and the adjusting section is connected to the apparatus only at the time of adjustment, it is necessary to prepare the response characteristic data storage section and the adjusting section for each apparatus. Absent. Therefore, the cost can be reduced, and the installation space can be reduced when the system is installed.

[0066]

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

2 is a flowchart showing an optical signal level calculation operation in the device shown in FIG.

FIG. 3 is a diagram showing an example in which a correction unit 42 in the apparatus shown in FIG. 1 obtains corrected response characteristic data g (Δλ).

FIG. 4 is a diagram showing a relationship between relative deviation amount δx and relative power fluctuation of an added value of PD, which is obtained from corrected response characteristic data g (Δλ).

FIG. 5 is a block diagram showing a second embodiment of the present invention.

6 is a flowchart showing an optical signal level and optical SNR calculation operation in the device shown in FIG.

FIG. 7 is a block diagram showing an embodiment of a conventional WDM signal monitor.

FIG. 8 is a diagram showing an example of response characteristics of a spectroscope to a line spectrum.

9 is a block diagram of a spectroscope in the apparatus shown in FIG. 7. FIG.

FIG. 10 is a schematic view showing a part of a photodiode array.

FIG. 11 is a diagram showing an example of the relationship between the photodiode array and the output of the photodiode.

FIG. 12 is a diagram showing a relationship between relative deviation amount δx and relative power fluctuation of an added value of PD, which is obtained from response characteristic data f (Δλ).

[Explanation of symbols]

10 Spectrometer 13 diffraction grating 15 Photodiode module 15a to 15e Photodiode 20 Response characteristic data storage 30, 70 Operation part 40 Adjuster 41 Input means 42 Correction means 50, 60 Correction data storage section 71 SNR calculation means 100, 100A, 100B Measured light

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04J 14/02 (72) Inventor Yasuyuki Suzuki 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. (72) Inventor Yoruki Okada 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. (72) Inventor Shuhei Okada 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. F Term (reference) 2G020 BA20 CB04 CC02 CC13 CC48 CC63 CD03 CD24 CD36 CD37 5K002 BA05 CA14 DA02 EA05 FA01

Claims (6)

[Claims] 1. A spectroscope for measuring a spectrum of a WDM signal, a response characteristic data storage section for storing response characteristic data for a line spectrum of an optical signal of the spectroscope, and a characteristic of a WDM signal input to the spectroscope. Is entered,
An adjusting unit that obtains correction data based on the characteristic of the WDM signal and the response characteristic data of the response characteristic data storage unit, a correction data storage unit that stores the correction data obtained by the adjusting unit, and the spectroscope. A WDM signal monitor comprising: a calculation unit that calculates at least an optical signal level of the WDM signal based on the measured spectrum and the correction data of the correction data storage unit. 2. The WDM signal monitor according to claim 1, wherein the spectroscope measures sampling data on the wavelength axis with a wavelength width narrower than the spread of the response spectrum with respect to the line spectrum. 3. The spectroscope has a wavelength dispersive element that disperses a WDM signal, and a photodiode array that includes a plurality of photodiodes that receive the dispersed light. WDM signal monitor. 4. The adjusting unit obtains correction data based on a WDM signal characteristic that is at least one of a modulation method for modulating a WDM signal and an optical filter characteristic of a multiplexing / demultiplexing apparatus that multiplexes or demultiplexes the WDM signal. Claims 1 to 1 characterized in that
The WDM signal monitor according to any one of 3 above. 5. The adjusting section corrects the response characteristic data corrected based on the response characteristic data of the response characteristic data storage section and the characteristic of the WDM signal, and the optical power obtained from the corrected response characteristic data. The WDM signal monitor according to claim 1, wherein correction data that is at least one of optical power correction data is obtained. 6. The WDM signal monitor according to claim 1, wherein at least one of the response characteristic data storage unit and the adjustment unit is connected at the time of adjustment.