JPH09297090A - Method for measuring peak wavelength and noise figure of multi-channel signal, and spectrum analyzer with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure an NF of each channel by finding a maximum value in sampling data, deciding a threshold value working out at a specified rate of the maximum value, and regarding, in data which exceeds the threshold value, what is larger than data before and after as a peak of each channel signal. SOLUTION: In a peak retrieving part 104, when a wave form is inputted, input data for a specified number of sampling data is added, and then divided by the number of sampling data, for smoothing. Then, a maximum value in the inputted data which is smoothing-processed is found, and further, a threshold value is decided from the maximum value, and a peak exceeding the threshold value is detected. With an NF analyzing part 105, a valley between each peak which is found with the retrieving part 104 is found. A finding method for the peak in the retrieving part 104 and that for the NF in the analyzing part 105 are, by inputting an input light after covering into an electric signal, applied to an electrical spectrum analyzer, too, in which the inputted signal is mixed with a lamp signal for wavelength analysis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectrum analyzer for analyzing a waveform of input light, and more particularly to a spectrum analyzer having a noise figure measuring function.

[0002]

2. Description of the Related Art In recent years, optical amplifiers, particularly optical fiber amplifiers, have been used for optical communication systems, optical submarine cables, and other long-distance backbone communication to optical subscriber systems for reasons such as improved transmission quality. , Optical CATV is often used.

In an optical communication system using these amplifiers, the noise characteristic of the optical amplifier is the S of information to be transmitted.
Has a great effect on / N. Therefore, when constructing an optical communication system using an optical amplifier, it is important to accurately grasp the noise figure (hereinafter referred to as NF (Noise Figure ₎₎ which is the basic performance of the optical amplifier.

FIG. 6 is a block diagram showing the configuration of a conventional example of an optical spectrum analyzer for measuring an optical amplifier NF.

The optical spectrum analyzer shown in FIG.
Spectrometer 601 for splitting the measured light into light in the measurement target region
An O / E converter 602 that converts the output of the spectroscope 601 into an electric signal, an A / D converter 603 that converts the output of the O / E converter 602 into a digital signal, and an A / D converter 603
A peak search unit 604 that searches for a peak value in the waveform shown in the output, an NF analysis unit 605 that calculates NF based on the peak value calculated by the peak search unit 604, and a display unit that displays the analysis results. It is composed of 606.

The peak search unit 604 uses the maximum value of the input as a peak, and the NF analysis unit 605 calculates the spontaneous emission light level P _ASE from the peak value and calculates NF from the following equation.

NF = P _ASE / hνGΔν (1) where h is Planck's constant, ν is signal light frequency, and Δν is measurement frequency resolution.

In order to measure NF with high accuracy, it is necessary to accurately obtain each component in the above equation. The signal light frequency ν and the measurement frequency resolution Δν can be obtained from the output wavelength and the resolution of the spectroscope 601, and the most problematic point in obtaining NF is that the analyzing unit 605 causes the spontaneous emission light level P _ASE.
Is to seek.

As a method for obtaining the spontaneous emission light level P _ASE, an "estimation method" which is obtained by fitting from the spectrum shape of the spontaneous emission light near the signal light is often used. In the estimation method, the quadratic function is approximated by the least squares method using the data in the predetermined designated sections on both sides of the output optical spectrum which is the peak value, and the fitting is performed by the Gaussian curve.

[0010]

In recent years, optical communication uses multi-channel signals in order to increase the amount of information. In such a signal, a peak occurs for each signal, but in the above-mentioned conventional spectrum analyzer, NF is calculated by obtaining the maximum value of the input signal, and therefore one channel of one input waveform There is a problem that only the peak and NF can be obtained.

The present invention has been made in view of the problems of the above-mentioned conventional techniques, and is to realize a method and a spectrum analyzer capable of measuring the NF of each channel of a multi-channel signal. With the goal.

[0012]

A method for measuring the peak wavelength of a multi-channel signal according to the present invention is a method for measuring the peak wavelength of a multi-channel signal represented by a plurality of sampling data, wherein Obtain the value, set a threshold value that is a predetermined ratio of the maximum value,
Among the sampling data that exceeds the threshold value, one that is larger than the preceding and following sampling data is set as the peak of each channel signal that constitutes the multi-channel signal.

The noise figure measuring method of the multi-channel signal of the present invention is a method of measuring the noise figure using the peak determined by the above-mentioned measuring method of the peak wavelength of the multi-channel signal. A characteristic is characterized in that a valley is obtained, a quadratic curve connecting the valleys is obtained as a curve showing a spontaneous emission light level, and a level corresponding to each peak wavelength in the quadratic curve is taken as a spontaneous emission light level of each channel to obtain a noise figure. And

In this case, the minimum value between the peaks may be the valley, or the center between the peaks may be the valley.

The spectrum analyzer of the present invention is an A / D converter for converting an input signal into a plurality of sampling data and a maximum value in the sampling data in the spectrum analyzer for wavelength analysis of the input multi-channel signal. A peak search unit that determines a threshold value that is a predetermined ratio of the maximum value, and that among the sampling data that exceeds the threshold value, one that is larger than the preceding and following sampling data is the peak of each channel signal that constitutes the multi-channel signal, A valley between each peak is obtained, a quadratic curve connecting the valleys is obtained as a curve showing a spontaneous emission level, and a level corresponding to each peak wavelength in the quadratic curve is taken as a spontaneous emission level of each channel and a noise figure. And an NF analysis unit for obtaining

[Operation] In the present invention configured as described above, since all peaks exceeding the threshold value determined by the maximum value are detected, by adjusting the threshold value,
The peaks of the signals forming the multi-channel signal can be detected respectively.

Further, since the spontaneous emission light level which is the most important when measuring NF is obtained as a quadratic curve connecting the valleys between the peaks, by using the level of the part corresponding to the curve, The NF of the channel can be obtained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. Spectrometer 101, O / E in this embodiment
Converter 102, A / D converter 103, peak search unit 10
4, the configuration of the NF analysis unit 105 and the display unit 106 is shown in FIG.
The same as the spectroscope 601, the O / E converter 602, the A / D converter 603, the peak search unit 604, the NF analysis unit 605, and the display unit 606 shown in FIG. And the method of obtaining NF in the NF analysis unit 105 is different from the conventional example.
A method for obtaining these will be described.

2A and 2B are diagrams showing input waveforms for explaining the peak calculating method in the present embodiment, and FIG. 4 is a flow chart showing the calculating procedure.

When a waveform is input to the peak search unit 104, smoothing is performed in which input data for a predetermined number of sampling data (for example, 5 data after the target data) is added and divided by the number of sampling data. Perform (step S401). Next, the maximum value P _P in the input data that has been subjected to the smoothing processing as described above is obtained (step S402), and the threshold value is determined from the maximum value P _P.
The peaks P _{0 to} P ₂ that exceed the threshold value are detected (step S
403). In determining the threshold value, a predetermined ratio (eg 70%) of the maximum value P _P is set.

Further, in detecting the peaks P _{0 to} P ₂ which exceed the threshold value, three sampling data q _(n-1) , q _(n) and q _{(n + 1} ) are obtained as shown in FIG. 2B. ₎ Is confirmed every q ₎ , and q _(n) is a peak when q _(n-1) <q _(n) > q _{(n + 1)} is satisfied.

Next, how to obtain the NF in the NF analysis unit 105 will be described. FIG. 3 shows the NF in this embodiment.
FIG. 5 is a wave system diagram for explaining the method of obtaining, and FIG. 5 is a flowchart showing the operation.

In the NF analysis unit 105, first, each peak (P ₀ to in FIG. 3) obtained by the peak search unit 104 is calculated.
The valleys r _{0 to} r ₅ between P ₄ ) are obtained (step S501).
Examples of the method of obtaining the valley include the center of each peak, the minimum value between the peaks, and the like, and the value obtained by averaging the values in the vicinity thereof or the smoothed value is considered. May be

Next, a quadratic curve connecting the valleys r _{0 to} r ₅ in succession is obtained, and this is used as a spontaneous emission light level P _ASE curve (step S502). Subsequently, the level corresponding to each peak wavelength in the P _ASE curve obtained in step S502 is set as the spontaneous emission light level P _ASE of each channel,
NF is obtained by the equation (1).

In the embodiment described above, the measurement is performed using the optical spectrum analyzer. However, the method of obtaining the peak in the peak searching section 104 and the NF analyzing section 105 which are the features of the present invention. NF
Can be applied to an electric spectrum analyzer that performs wavelength analysis by mixing the input signal with a lamp signal by converting the input light into an electric signal and inputting it. Good.

[0027]

As described above, the present invention obtains the maximum value in sampling data, defines a threshold value that is a predetermined ratio of the maximum value, and selects sampling data exceeding the threshold value from the sampling data before and after it. There is an effect that the NF of each channel of the multi-channel signal can be measured by setting a large one as the peak of each channel signal forming the multi-channel signal.

[Brief description of drawings]

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

FIG. 2A and FIG. 2B are diagrams showing input waveforms for explaining a peak calculation method in an embodiment of the present invention.

FIG. 3 is a wave system diagram for explaining how to obtain NF in the example of the present invention.

FIG. 4 is a flowchart showing a peak calculation procedure in the embodiment of the present invention.

FIG. 5 is a flowchart showing how to obtain NF in the embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 101 spectroscope 102 O / E converter 103 A / D converter 104 peak search unit 105 NF analysis unit 106 display unit

Claims (5)

[Claims] 1. A method for measuring a peak wavelength of a multi-channel signal represented by a plurality of sampling data, wherein a maximum value in the sampling data is obtained, a threshold value that is a predetermined ratio of the maximum value is determined, and the threshold value is set. A method for measuring the peak wavelength of a multi-channel signal, characterized in that, of the sampling data that exceeds, the peak data of each channel signal that constitutes the multi-channel signal is larger than the sampling data before and after. 2. A method for measuring a noise figure using a peak determined by the method for measuring a peak wavelength of a multi-channel signal according to claim 1, wherein valleys between peaks are obtained, and the valleys are connected. A quadratic curve is obtained as a curve showing a spontaneous emission light level, and a noise figure is obtained using the level corresponding to each peak wavelength in the quadratic curve as the spontaneous emission light level of each channel. Measuring method. 3. The noise figure measuring method for a multi-channel signal according to claim 2, wherein a minimum value between peaks is used as a valley. 4. The noise figure measuring method for a multi-channel signal according to claim 2, wherein the center between peaks is used as a valley. 5. A spectrum analyzer for analyzing the wavelength of an input multi-channel signal, the A / D converting the input signal into a plurality of sampling data.
A converter and a maximum value in the sampling data are obtained, a threshold value that is a predetermined ratio of the maximum value is determined, and among the sampling data that exceeds the threshold value, the one that is larger than the preceding and following sampling data forms a multi-channel signal. A peak search unit that is a peak of each channel signal and a valley between the peaks are obtained, and a quadratic curve connecting the valleys is obtained as a curve indicating the spontaneous emission light level and corresponds to each peak wavelength in the quadratic curve. A spectrum analyzer, comprising: an NF analysis unit that obtains a noise figure using the level as the spontaneous emission light level of each channel.