JPH11237282A - Power operating method and spectrometer employing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress fluctuation of relative power by adding the strength of detection signals from three or more light receiving sections including that of an array type photodetector element detecting a peak thereby operating the spectral power. SOLUTION: Measuring light subjected to spectroscopy through a wavelength dispersion element is condensed onto an array element and inputted through a drive means to an operating means. The operating means adds the strength of detection signals from at least three light receiving sections D002, D003, D004 out of D001-D005 including the D003 detecting a peak to determine the power at the D003. When the power at the light receiving section D003 is determined by live point addition, for example, strength of detection signals from the D001-D005 are added. Since fluctuation of relative power is suppressed, flatness is enhanced in the measurement of the quantity of light resulting in a highly accurate control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power calculation method for obtaining the power of the spectrum of a laser beam or the like using an array-type photodetector (hereinafter, referred to as an array element).
The present invention relates to a power calculation method capable of reducing relative power fluctuation and a spectroscopic device using the same.

[0002]

2. Description of the Related Art Conventionally, when a center wavelength of a spectrum of a laser beam or the like is obtained by a spectroscope using an array element, a waveform distribution on the array element is approximated by a Gaussian distribution or a quadratic curve, and the peak position is obtained. Calculate the center wavelength.

[0003] Further, as for the power of the spectrum, the total power of the spectrum is obtained by correcting the output of the light receiving unit that has detected the peak, assuming that the output pattern of each light receiving unit of the array element is a Gaussian distribution.

FIG. 8 is a configuration block diagram showing an example of such a conventional spectroscopic device using an array element. In FIG. 8, 1 is a slit, 2 is a collimating mirror, 3
Is a wavelength dispersion element such as a diffraction grating, 4 is a focusing mirror, 5 is an array element, 6 is driving means, 7 is arithmetic means, 8
Denotes display means, and 100 denotes light to be measured. 1 to 5 constitute the spectroscopic means 50.

The light to be measured 100 is incident on the collimating mirror 2 via the slit 1, and the reflected light from the collimating mirror 2 is incident on the focusing mirror 4 via the wavelength dispersion element 3. The reflected light from the focusing mirror 4 enters the array element 5. An output signal from the array element 5 is connected to an arithmetic unit 7 via a driving unit 6,
The output of the calculating means 7 is connected to the display means 8.

Now, the operation of the conventional example shown in FIG. 8 will be described. The light to be measured 100 is reflected by the collimating mirror 2 as parallel light after passing through the slit 1 and is incident on the wavelength dispersion element 3. In the wavelength dispersion element 3, the light is reflected by the focusing mirror 4 at a reflection angle that differs depending on the wavelength of the incident light, and the focusing mirror 4 condenses the incident light on the array element 5.

On the other hand, the driving means 6 controls the position of the array element 5, reads out an output signal from the array element 5, and outputs it to the arithmetic means 7. The calculating means 7 performs an appropriate calculating process such as a power calculation based on the output signal from the driving means 6 and causes the display means 8 to display.

A method for calculating the power will be described with reference to FIG. FIG. 9 is an explanatory diagram showing a relative position between an incident beam and an array element. Assuming that the pattern of the incident beam as shown in FIG. 9 is a Gaussian distribution, the pitch “r” of each light receiving portion of the array element, the width “d” of the light receiving portion, the light receiving portion detecting the incident beam and the peak ” Considering the deviation “Δx” from the center of D000 ”and the radius“ ω ”of the incident beam, etc.
The power of the light receiving unit “D000” is corrected.

[0009]

However, since the pattern of the incident beam is not an ideal Gaussian distribution in practice,
An operation error occurs in the power operation method based on the Gaussian distribution. In addition, WDM transmission (Wavelength Division Mu
ltiplexing) When monitoring multiple spectra in a system, the power level of each spectrum is important, and it is necessary that the relative power fluctuation with respect to the wavelength axis be small, but this relative power fluctuation is relative to the incident beam and the array element. Since the calculation error is caused by the position, the conventional power calculation method has a problem that the relative power fluctuation is large. Therefore, the problem to be solved by the present invention is:
It is an object of the present invention to realize a power calculation method capable of reducing relative power fluctuation and a spectroscopic device using the same.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, a spectrum dispersed by a wavelength dispersive element is detected by an array type photodetector, and In a power calculation method for calculating the power of a spectrum, the power of the spectrum is calculated by adding the intensities of detection signals of three or more light receiving units including a light receiving unit of the array-type photodetector detecting a peak. As a result, relative power with little fluctuation can be obtained.

According to a second aspect of the present invention, in the power calculation method according to the first aspect, three or more light sources including a reference light having a known incident power and a light receiving portion detecting a peak of the reference light. By correcting the absolute value of the power of the spectrum using the added value obtained by adding the intensity of the detection signal of the light receiving unit, the absolute value of the power of the light receiving unit detecting the peak can be obtained.

According to a third aspect of the present invention, there is provided a spectral means for detecting a spectrum dispersed by the wavelength dispersive element with an array-type photodetector, and a driving means for reading out and outputting an output signal from the array-type photodetector. Calculating means for calculating the power of the spectrum by adding the intensities of the detection signals of three or more light receiving units including the light receiving unit of the array type photodetector detecting the peak. And a relative power of less.

According to a fourth aspect of the present invention, in the spectroscopic apparatus according to the third aspect, the calculating means includes a reference light having a known incident power and a light receiving section detecting a peak of the reference light. The absolute value of the power of the spectrum is corrected by using the added value obtained by adding the intensities of the detection signals of the one or more light receiving units, so that the absolute value of the power of the light receiving unit detecting the peak can be obtained.

According to a fifth aspect of the present invention, there is provided a spectroscopic apparatus according to the third and fourth aspects, wherein the spectrometer is configured to measure an optical signal wavelength or power and control an output light wavelength or an output light power of a light source. By using as a measuring means of the wavelength or power of the optical signal of the multiplex communication system,
Even in the light receiving sections of the array elements arranged discretely, the flatness performance of the optical power measurement with respect to the wavelength axis can be made the same as in the case of no modulation, so that high-precision power measurement becomes possible.

According to a sixth aspect of the present invention, there is provided a spectroscope according to the third and fourth aspects of the present invention, comprising: a plurality of semiconductor laser light sources for emitting output lights of different wavelengths; A plurality of scramblers for randomizing the polarization of light, a multiplexer for multiplexing the output light of these scramblers to generate an optical communication signal, and a measurement for measuring the wavelength or power of the output light of the multiplexer Means for controlling the output light wavelength or the output light power of the plurality of semiconductor laser light sources based on the output of the measuring means. Even in the light receiving portions of the array elements arranged in a uniform manner, the flatness performance of the optical power measurement with respect to the wavelength axis can be performed in the same manner as in the case of no modulation.

According to a seventh aspect of the present invention, the spectrometer according to the third and fourth aspects measures the wavelength or power of an optical signal and controls the amount of light of each wavelength incident on the multiplexer. By using as a means for measuring the wavelength or power of the optical signal of the optical wavelength division multiplex communication system, the relative power fluctuation is reduced, so that the flatness of the light quantity measurement is improved,
Highly accurate control becomes possible.

According to an eighth aspect of the present invention, there is provided the spectroscopic device according to the third and fourth aspects, wherein the splitter splits an incident optical communication signal into each wavelength, and the split light. An optical circulator, an optical / electrical converter for converting an optical signal from the optical circulator into an electric signal, and an input electric signal converted into an optical signal and applied to the optical circulator for extracting a part of the communication signal. An electrical / optical converter and the optical / optical converter
An electric node device that takes in the output signal of the electric converter and applies the electric signal to the electric / optical converter, and adjusts the level of the light amount of the output light of the duplexer and the output light from the optical circulator, respectively. A plurality of attenuators, a multiplexer for multiplexing the output lights of these attenuators, a measuring unit for measuring the wavelength or power of the output light of the multiplexer, and the plurality of attenuators based on the output of the measuring unit. By using as the measuring means of the optical wavelength division multiplexing communication system including the light amount control device for controlling the attenuation amount of the attenuator, the relative power fluctuation is reduced, so that the flatness of the light amount measurement is improved, and the accuracy is improved. High control becomes possible.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration block diagram showing one embodiment of a spectrometer using an array element according to the present invention. In FIG. 1, 1 to 6, 8 and 100 are denoted by the same reference numerals as in FIG. 8, and 9 is an operation means. Further, the connection relation is the same as that of the conventional example shown in FIG. 8, and the difference is that the operation means 7 is replaced by the operation means 9.

Here, the operation and the power calculation method of the embodiment shown in FIG. 1 will be described. The light to be measured 100 is reflected by the collimating mirror 2 as parallel light after passing through the slit 1 and is incident on the wavelength dispersion element 3. In the wavelength dispersion element 3, the light is reflected by the focusing mirror 4 at a reflection angle that differs depending on the wavelength of the incident light, and the focusing mirror 4 condenses the incident light on the array element 5.

On the other hand, the driving means 6 controls the position of the array element 5, reads out an output signal from the array element 5, and outputs it to the arithmetic means 9. The calculating means 9 performs an appropriate calculating process based on the output signal from the driving means 6 and causes the display means 8 to display.

The method of calculating the power will be described with reference to FIGS. 2, 3, 4 and 5. FIG. 2 is an explanatory view showing the relative position between the incident beam and the array element, FIG. 3 is an explanatory view showing the output pattern of the light receiving section, and FIGS. 4 and 5 are relative powers in the power calculation method according to the present invention and the conventional calculation method. FIG. 9 is a characteristic diagram showing a change. In FIG. 2, “r”, “d” and “Δx” are the same as those in FIG.

In the power calculating method according to the present invention, the calculating means 9 detects the peak by using the light receiving section "D0" shown in FIG.
The power of the light receiving unit “D003” is obtained by adding the intensities of the detection signals of at least three light receiving units including “03”.

For example, as shown in FIG. 3, "D00" in FIG.
1 "," D002 "," D003 "," D004 ", and" D005 "indicate that the intensity of the detection signal at the light receiving unit is" P1, "" P2, "" P3, "" P4, "and" P. "
5 ", and if it is determined by adding three points,
The power detected by the light receiving unit “D003” is “P (3)”
Then, P (3) = P2 + P3 + P4 (1)

When the power detected by the light receiving section "D003" is "P (5)" when the five points are added, P (5) = P1 + P2 + P3 + P4 + P5 (2)

Further, the absolute value "Pabs" of the power detected by the light receiving section "D003" is equal to the known incident power "Pbs".
If the added value of the incident beam of “in” as in the equation (2) is “Pin (5)”, then Pabs = P (5) × Pin / Pin (5) (3)

That is, correction is performed using an addition value obtained by adding the intensities of detection signals of three or more light receiving units including a light receiving unit that detects a peak of the reference light and a reference light whose incident power is known. It becomes possible to correct the absolute value of the power.

FIG. 4A shows the relative power fluctuation when the incident beam moves by the pitch "r" of each light receiving portion of the array element at the added value of five points as shown in equation (2). FIG. 4B shows the relative power fluctuation when the calculation is performed by approximating the conventional Gaussian distribution. In addition, the incident beam has a Gaussian distribution with an asymmetrical intensity distribution, in other words, the radius of the left / right beam is “50/50 μm”, “
55/50 μm ”,“ 60/50 μm ”and“ 65/5
0 μm ”is shown.

From FIG. 4B to FIG. 4, a beam having a symmetrical Gaussian distribution (50/50 μm) indicated by “x” in FIG.
In the case of a beam having a beam radius of “55/50 μm” indicated by ▲, the relative power fluctuation is more stable than the power calculation method based on the five-point addition shown in FIG.
The beam radius indicated by “■” and “◆” is “60 / 50μ”
In the case of “m” and “65/50 μm”, it is understood that the relative power fluctuation is more stable in the power calculation method based on the five-point addition shown in FIG.

FIG. 5A shows the relative power fluctuation when the incident beam moves by the pitch "r" of each light receiving portion of the array element at the added value of five points as shown in the equation (2). FIG. 5B shows a relative power fluctuation when the calculation is performed by approximating with a conventional Gaussian distribution. The incident beam has a laterally asymmetrical Gaussian distribution, in other words, the radius of the left / right beam. To “90/90 μm”, “9”
9/90 μm ”,“ 108/90 μm ”and“ 117 /
90 μm ”is shown.

5 (B) to FIG. 5, beam radii indicated by “▲”, “■”, and “◆” other than the beam having a symmetrical Gaussian distribution (90/90 μm) indicated by “x” in FIG. But"
99/90 μm ”,“ 108/90 μm ”and“ 117 ”
/ 90 μm ”, it can be seen that the relative power fluctuation is more stable in the power calculation method based on the five-point addition shown in FIG.

As a result, by adding the intensities of the detection signals of at least three light receiving sections including the light receiving section detecting the peak, relative power with little fluctuation can be obtained. Further, the absolute value of the power of the light receiving unit that detects the peak can be obtained by performing correction using the known incident power and the added value of the incident beam.

FIG. 6 is a block diagram showing an example of a transmitter of an optical wavelength division multiplexing communication system using the spectrometer shown in FIG. In FIG. 6, 10 is a transmitter control device, 11, 12, and 13 are semiconductor laser light sources, and 14, 1
5 and 16 are scramblers, 17 is a multiplexer, 18 is FIG.
, 200 is transmission data, and 201 is an optical communication signal.

The transmission data 200 is input to the transmitter controller 10, and control signals from the transmitter controller 10 are connected to the semiconductor laser light sources 11, 12, and 13, respectively.
The output lights of the semiconductor laser light sources 11, 12 and 13 are passed through scramblers 14, 15 and 16, respectively, to a multiplexer 17.
Is incident on. The output light of the multiplexer 17 is an optical communication signal 201.
And a part of the output light from the multiplexer 17 is incident on the spectroscopic device 18. The output of the spectrometer 18 is connected to the transmitter controller 10.

Here, the operation of the transmitter of the optical wavelength division multiplexing communication system shown in FIG. 6 will be described. The transmission data 200 is input to the transmitter control device 10, which allocates the transmission data 200 to each channel and controls the oscillation wavelength and power of the semiconductor laser light sources 11, 12, and 13. The output lights of the semiconductor laser light sources 11, 12, and 13 are randomly polarized by scramblers 14, 15, and 16, respectively. Then, they are multiplexed by the multiplexer 17 to generate an optical communication signal 201 for optical wavelength multiplex communication.

On the other hand, the spectroscope 18 extracts a part of the optical communication signal 201 and measures the wavelength and the power. The transmitter control device 10 controls the semiconductor laser light sources 11 to 13 based on information from the spectroscopic device 18 so as to reduce signal deterioration on the receiving device side.

A phase modulator or the like is often used as the scramblers 14 to 16, and the scramblers 14 to 16 are used.
Since the spectrum of the output light from # 16 to # 16 spreads beyond the line width of the semiconductor laser light source due to the influence of the modulation, it is difficult to approximate the spectrum by a Gaussian distribution or the like.

On the other hand, in the spectroscope 18 according to the present invention, the relative power can be obtained only by adding the detection intensities of the respective light receiving portions of the array elements. Since the flatness performance of the power measurement can be made similar to the case of no modulation, high-precision power measurement becomes possible. That is, the power calculation method of the present invention does not assume a distribution such as a Gaussian distribution, so that, for example, even if the spectrum is widened by modulation, it is not affected.

As a result, by using the spectroscopic device according to the present invention as a transmitter in an optical wavelength division multiplexing communication system, even the light receiving sections of the array elements arranged discretely have no flatness performance of the optical power measurement with respect to the wavelength axis. Since the modulation can be performed in the same manner as the modulation, the power measurement can be performed with high accuracy.

FIG. 7 is a block diagram showing an example of an ADD / DROP module part of an optical wavelength division multiplexing communication system using the spectrometer shown in FIG. ADD
The / DROP module is a module for dropping (DROP) a specific wavelength on which a signal is carried at each node or additionally inserting (ADD) a specific wavelength.

In FIG. 7, 19 is a duplexer, 20 is an optical circulator, 21 is an optical / electrical converter, 22 is an electrical system node device, 23 is an electrical / optical converter, 24, 25 and 26 are attenuators, 27 Is a multiplexer, 28 is the spectrometer shown in FIG.
9 is a light amount control device, and 300 and 301 are optical communication signals.

The optical communication signal 300 enters the demultiplexer 19, and the output light of each of the demultiplexers 19 is attenuator 24, 25.
And 26 are input to the multiplexer 27. Duplexer 19
An optical circulator 20 is provided between the optical circulator 20 and the attenuator 25.
1, and the output light of the electric / optical converter 23 is incident on the optical circulator 20.

The output light of the multiplexer 27 is output as an optical communication signal 301, and a part of the output light of the multiplexer 27 is incident on the spectroscope 28. The output of the spectroscopic device 28 is connected to a light amount control device 29, and a control signal from the light amount control device 29 is connected to control terminals of the attenuators 24, 25, and 26. Further, the output of the optical / electrical converter 21 is connected to the electric node device 22, and the output of the electric node device 22 is connected to the electric / optical converter 23.

Here, the operation of the ADD / DROP portion of the optical wavelength multiplex communication system shown in FIG. 7 will be described. The optical communication signal 300 is split by the splitter 19 for each wavelength. A part of the demultiplexed optical communication signal is taken out via the optical circulator 20 and enters the optical / electrical converter 21. The output signal of the optical / electrical converter 21 is taken into the electric node device 22. Further, the electric node device 22 applies a signal to the electric / optical converter 23, and the electric / optical converter 23 outputs, via the optical circulator 20, an optical communication signal having the same wavelength as the wavelength of the previously acquired optical communication signal. The voltage is applied to the attenuator 25.

The attenuators 24 and 26 indicate the level of the light amount of the optical communication signal from the demultiplexer 19, and the attenuator 25 indicates the level of the light amount of the optical communication signal incident from the electric system node device 22 via the optical circulator 20. Are adjusted to combiner 2
7 is incident. The multiplexer 27 includes attenuators 24, 25 and 2
6 are multiplexed and emitted as an optical communication signal 301.

Here, the spectroscopic device 28 transmits the optical communication signal 301
Is monitored and the wavelength and power of the optical communication signal 301 are measured. The light amount control device 29 adjusts the attenuation amount of the attenuators 24, 25 and 26 based on the measurement value of the spectroscopic device 28 to adjust the level of the light amount of each wavelength.

As a result, by using the spectroscopic device according to the present invention in the ADD / DROP part of the optical wavelength division multiplexing communication system, the relative power fluctuation is reduced, so that the flatness of the light quantity measurement is improved and the control with high accuracy is achieved. Will be possible.

[0047]

As is apparent from the above description,
According to the present invention, the following effects can be obtained. According to the first aspect of the invention, by adding the detection signal intensities of at least three light receiving units including the light receiving unit that detects the peak, relative power with little fluctuation can be obtained.

Further, according to the second aspect of the present invention, the absolute value of the power of the light receiving unit that detects the peak can be obtained by using the known incident power and the added value of the incident beam.

According to the third aspect of the present invention, the arithmetic means adds the detection signal intensities of at least three light receiving sections including the light receiving section for which the peak is being detected, whereby
Relative power with little fluctuation is obtained.

According to the fourth aspect of the present invention, the absolute value of the power of the light-receiving unit for detecting the peak can be obtained by using the known incident power and the sum of the incident beams in the calculating means. it can.

According to the fifth and sixth aspects of the present invention, the spectroscopic device according to the present invention measures the wavelength or power of an optical signal and controls the output light wavelength or output light power of a light source. By using it as a means for measuring the wavelength or power of the optical signal of the system, the flatness performance of the optical power measurement with respect to the wavelength axis can be made similar to the case of non-modulation even in the light receiving sections of the array elements arranged discretely. High-precision power measurement becomes possible.

According to the seventh and eighth aspects of the present invention, the spectroscopic device according to the present invention measures the wavelength or power of an optical signal and controls the amount of light of each wavelength incident on the multiplexer. By using the optical signal as a means for measuring the wavelength or the power of the optical signal of the multiplex communication system, the relative power fluctuation is reduced, so that the flatness of the light quantity measurement is improved, and highly accurate control becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing one embodiment of a spectroscopic device using an array element according to the present invention.

FIG. 2 is an explanatory diagram showing a relative position between an incident beam and an array element.

FIG. 3 is an explanatory diagram illustrating an output pattern of a light receiving unit.

FIG. 4 is a characteristic diagram showing relative power fluctuations in a power calculation method according to the present invention and a conventional calculation method.

FIG. 5 is a characteristic diagram showing relative power fluctuations in the power calculation method according to the present invention and a conventional calculation method.

FIG. 6 is a configuration block diagram illustrating an example of a transmitter of an optical wavelength division multiplexing communication system using a spectrometer.

FIG. 7 shows an optical wavelength division multiplexing communication system A using a spectrometer.
FIG. 3 is a configuration block diagram illustrating an example of a DD / DROP module part.

FIG. 8 is a configuration block diagram illustrating an example of a conventional spectroscopic device using an array element.

FIG. 9 is an explanatory diagram showing a relative position between an incident beam and an array element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slit 2 Collimating mirror 3 Wavelength dispersive element 4 Focusing mirror 5 Array element 6 Driving means 7,9 Computing means 8 Display means 10 Transmitter control device 11,12,13 Semiconductor laser light source 14,15,16 Scrambler 17, Reference Signs List 27 multiplexer 18, 28 spectral device 19 demultiplexer 20 optical circulator 21 optical / electrical converter 22 electrical system node device 23 electrical / optical converter 24, 25, 26 attenuator 29 light amount control device 50 spectral device 100 measured Optical 200 Transmission data 201, 300, 301 Optical communication signal

Claims (8)

[Claims] 1. A power calculation method for detecting a spectrum separated by a wavelength dispersive element with an array-type photodetector and obtaining the power of the spectrum, wherein a light-receiving portion of the array-type photodetector detecting a peak is provided. A power calculation method, wherein the power of the spectrum is calculated by adding the intensities of the detection signals of three or more light-receiving units. 2. The power of the spectrum using an added value obtained by adding the intensities of detection signals of three or more light receiving units including a light receiving unit that detects a peak of the reference light and a reference light whose incident power is known. 2. The power calculation method according to claim 1, wherein the absolute value is corrected. 3. A spectral means for detecting a spectrum dispersed by the wavelength dispersive element with an array-type photodetector, a driving means for reading and outputting an output signal from the array-type photodetector, and detecting a peak. A spectrometer comprising: a calculating means for calculating the power of the spectrum by adding the intensities of the detection signals of three or more light receiving units including the light receiving units of the array type photodetector. 4. The arithmetic means uses an added value obtained by adding the intensities of detection signals of three or more light receiving portions including a light receiving portion detecting a peak of the reference light and a reference light having a known incident power. 4. The spectroscopic device according to claim 3, wherein an absolute value of the power of the spectrum is corrected. 5. An optical wavelength division multiplexing communication system for measuring the wavelength or power of an optical signal and controlling the output light wavelength or output light power of a light source, wherein the wavelength or power of the optical signal is measured. The spectroscopic device according to claim 3. 6. A plurality of semiconductor laser light sources for emitting output lights of different wavelengths, a plurality of scramblers for randomizing the polarization of output light of each of these semiconductor lasers, and combining the output lights of these scramblers. A multiplexer for generating an optical communication signal, measuring means for measuring a wavelength or power of output light of the multiplexer, and an output light wavelength or output of the plurality of semiconductor laser light sources based on an output of the measuring means. 5. The spectroscopic device according to claim 3, wherein the spectroscopic device is used as the measuring means of an optical wavelength multiplex communication system including a control device for controlling optical power. 7. An optical wavelength division multiplexing communication system for measuring the wavelength or power of an optical signal and controlling the amount of light of each wavelength incident on a multiplexer is used as a means for measuring the wavelength or power of the optical signal. The spectroscopic device according to claim 3, wherein 8. A splitter for splitting an incident optical communication signal into respective wavelengths, an optical circulator for extracting a part of the split optical communication signal, and an optical signal from the optical circulator for converting an optical signal from the optical circulator into an electric signal. An optical / electrical converter for converting an input electric signal into an optical signal and applying the same to the optical circulator; An electrical node device for applying an electrical signal to the optical converter; a plurality of attenuators for respectively adjusting the levels of the amounts of light output from the demultiplexer and the output light from the optical circulator; outputs of these attenuators A multiplexer for multiplexing light; measuring means for measuring the wavelength or power of output light of the multiplexer; a light amount control device for controlling the attenuation of the plurality of attenuators based on the output of the measuring means; Composed of Spectroscopic apparatus according to claim 3 and claim 4, wherein the used as the measuring means of the wavelength-division multiplexing system.