JP2007178258A - Optical spectrum analyzer and optical fiber sensor system using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical spectrum analyzer capable of performing accuracy confirmation of wavelength measurement even during measurement accurately with high reliability in a short time, and an optical fiber sensor system using the same. <P>SOLUTION: The analyzer is acquired by improving an optical spectrum analyzer having a spectroscope for sampling input light and outputting it as sampling data, and a wavelength operation means for performing wavelength measurement of a spectrum of the input light by the sampling data from the spectroscope, and is characterized by having a reference wavelength light source part for outputting reference light having an optical power with a prescribed wavelength; a wavelength filter into which light to be measured having a light signal is input, outputting the light after removing light having a prescribed wavelength; a photosynthesis part for synthesizing the reference light from the reference wavelength light source part with light from the wavelength filter, and outputting it as an input light to the spectroscope; and a determination means for determining a wavelength error from the wavelength of the reference light from the reference wavelength light source part and a result of the wavelength measurement measured by the wavelength operation means, and performing accuracy confirmation of the wavelength measurement. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical spectrum analyzer for measuring the wavelength of an optical signal contained in light to be measured and an optical fiber sensor system using the optical spectrum analyzer. The present invention relates to an optical spectrum analyzer capable of confirming the accuracy of wavelength measurement, and an optical fiber sensor system using the same.

  An optical spectrum analyzer is a measuring apparatus that samples a light to be measured with a desired wavelength width using a wavelength dispersion element, and analyzes and measures the spectrum of the light to be measured from this sampling data.

  The optical spectrum analyzer is, for example, an optical fiber sensor system (for example, refer to Patent Documents 1 to 3) using a fiber black grating (hereinafter abbreviated as FBG (Fiber Bragg Grating)), or a plurality of optical signals having different wavelengths. Used in an optical communication system using a WDM (wavelength division multiplexing) signal (see, for example, Patent Document 4).

  If the optical spectrum analyzer is an optical fiber sensor system, the optical signal, which is reflected light from the FBG, is spectrally divided for each wavelength, and the wavelength, signal level, etc. of each optical signal are obtained from the obtained spectrum. On the other hand, in the case of an optical communication system, a WDM signal is dispersed for each wavelength, and the wavelength and signal level of each optical signal are obtained from the obtained spectrum.

  In such an optical spectrum analyzer, in order to measure the wavelength with high accuracy, a reference wavelength light source unit is built in the optical spectrum analyzer, and the reference light from this reference wavelength light source unit is measured, so that wavelength measurement is performed with high accuracy. (For example, refer to Patent Document 4).

  FIG. 4 is a diagram showing a configuration example of a conventional optical spectrum analyzer. In FIG. 4, the spectroscope 10 receives light to be measured and reference light including an optical signal, samples the optical power of the light to be measured and the reference light with a desired wavelength width by a wavelength dispersion element (not shown), and measures sampling data. Output as data.

  The reference wavelength light source unit 20 outputs reference light having a large light output peak at a predetermined wavelength. Of course, the reference wavelength light source unit 20 has very little wavelength fluctuation and high stability.

  The optical coupler 30 combines the light to be measured and the reference light from the reference wavelength light source unit 20 and outputs the combined light to the spectrometer 10. In general, the light to be measured and the reference light are transmitted to the spectrometer 10 by an optical fiber (not shown).

  The calculation unit 40 includes a wavelength calculation unit 41 and a determination unit 42, and performs wavelength measurement of each of the light under measurement and the reference light from the measurement data of the spectrometer 10. Further, the accuracy of wavelength measurement is confirmed from the result of wavelength measurement of the reference light. The wavelength calculation means 41 measures the wavelengths of the measured light and the reference light from the measurement data of the spectrometer 10. The determination unit 42 confirms the accuracy of wavelength measurement based on the wavelength measurement result of the reference light from the wavelength calculation unit 41.

The operation of such an apparatus will be described.
First, the normal measurement, that is, the case of measuring the light to be measured will be described. The switch of the reference wavelength light source unit 20 is turned off to stop the output of the reference light, and only the measured light is input to the spectrometer 10 via the optical coupler 30. The spectroscope 10 samples the light to be measured for each desired wavelength width, for example, from the short wavelength side, and outputs measurement data having a relationship between the wavelength and the optical power to the calculation unit 40. And the wavelength calculating means 41 of the calculating part 40 calculates | requires the wavelength of each optical signal. That is, measurement data (hereinafter abbreviated as peak data) having a value significantly larger than the nearby measurement data is detected, and the wavelength corresponding to the detected peak data is obtained. Then, the calculation unit 40 displays the wavelength obtained by the wavelength calculation unit 41, for example, on a screen of a display unit (not shown) or outputs it to an external device (not shown).

  Next, a case where wavelength accuracy is confirmed (also referred to as wavelength calibration or wavelength adjustment), that is, a case where the reference light of the reference wavelength light source unit 20 is measured will be described. The switch of the reference wavelength light source unit 20 is turned on to output the reference light. The reference and the measured light from the reference wavelength light source unit 20 are input to the spectroscope 10 via the optical coupler 30.

  Then, the spectroscope 10 outputs measurement data having a relationship between the wavelength and the optical power to the calculation unit 40 in the same manner as in normal measurement. Then, the wavelength calculation means 41 of the calculation unit 40 detects the peak data of the reference light, obtains the wavelength corresponding to the detected peak data, and outputs the obtained wavelength to the determination means 42. Since the wavelength of the reference light is determined in advance, the wavelength that is closest to the wavelength of the reference light among the obtained wavelengths is output.

  Then, the judging means 42 compares the wavelength of the reference light peak data obtained by the wavelength calculating means 41 with a predetermined wavelength of the reference light. If the wavelength error is within a desired range, it is accurate. Judge that measurement is possible. On the other hand, if the wavelength error is not within the desired range, it is determined that there is a failure. For example, an alarm is displayed on the screen of a display unit (not shown) or an alarm signal is output to an external device (not shown).

JP 2000-352524 A JP 2001-221615 A JP 2002-131022 A JP 2004-077416 A

  Thus, by measuring the reference light having a fixed wavelength, the accuracy of wavelength measurement can be confirmed, so that the wavelength of the light to be measured can be accurately measured.

  Normally, a wavelength range (first wavelength range) in which an optical signal exists is determined for each system regardless of whether it is an optical fiber sensor system or an optical communication system. Therefore, the wavelength of the reference light of the reference wavelength light source unit 20 is set outside the first wavelength range where the optical signal exists. Of course, it is set within a wavelength range (second wavelength range) that can be measured by the optical spectrum analyzer, that is, the spectroscope 10, and the second wavelength range is wider than the first wavelength range.

  However, the optical signal included in the light to be measured may exist outside the first wavelength range due to, for example, a failure on the system side. This will be described with reference to FIG. FIG. 5 shows the measured light (FIG. 5C) to which the measured light (FIG. 5A), the reference light (FIG. 5B), and the reference light input to the spectrometer 10 are added. It is the figure which showed the characteristic. In FIG. 5, the horizontal axis represents the wavelength, and the vertical axis represents the optical power.

  Note that a plurality of light signals or one light signal exists in the light to be measured. Here, in order to simplify the description, two light signals 100 and 101 are used, and one of the light signals 100 has a first wavelength range. An example in which the other optical signal 101 exists outside and exists in the first wavelength range is shown.

  As shown in FIG. 5C, when the wavelength of the reference light 102 of the reference wavelength light source unit 20 and the wavelength of the optical signal 100 are substantially the same, the reference light 102 and the optical signal 100 are overlapped by the optical coupler 30, and the reference The spectral shape of the light 102 changes significantly. For this reason, it is difficult for the synthesized light to accurately determine the wavelength of the reference light 102, and it is difficult to accurately check the wavelength accuracy.

  Note that an optical switch can be used instead of the optical coupler 30 as shown in Patent Document 4 described above. However, in the case of an optical switch, the connection of the optical switch is switched, and the reference light and the measured light are measured separately. Therefore, since the measurement light and the reference light cannot be measured at the same time, the measurement of the measurement light is interrupted during the wavelength calibration, and it is difficult to perform the wavelength measurement continuously. In addition, since there are movable parts, switching of the optical switch has a problem of inferior reliability, switching time, and cost.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to realize an optical spectrum analyzer and an optical fiber sensor system using the optical spectrum analyzer that can confirm the accuracy of wavelength measurement even during measurement in a short time with high accuracy and reliability.

The invention described in claim 1
In an optical spectrum analyzer having a spectrometer that samples input light and outputs it as sampling data, and wavelength calculation means that performs wavelength measurement of the spectrum of the input light by sampling data from the spectrometer,
A reference wavelength light source unit that outputs reference light having optical power at a predetermined wavelength;
A first wavelength filter that receives light to be measured having an optical signal and outputs the light except the light of the predetermined wavelength;
A light combining unit that combines the reference light from the reference wavelength light source unit and the light filtered by the first wavelength filter and outputs the input light to the spectrometer;
And a determination unit that obtains a wavelength error from the wavelength of the reference light of the reference wavelength light source unit and the wavelength measurement result measured by the wavelength calculation unit and confirms the accuracy of the wavelength measurement.
The invention according to claim 2 is the invention according to claim 1,
The reference wavelength light source unit outputs a plurality of reference lights having different wavelengths.
The invention according to claim 3 is the invention according to claim 1 or 2,
The reference wavelength light source unit is a gas laser.
The invention according to claim 4 is the invention according to claim 1 or 2,
The reference wavelength light source is
A broadband light source;
And a second wavelength filter that outputs only light of the predetermined wavelength out of the light from the broadband light source.
The invention according to claim 5 is the invention according to any one of claims 1 to 4,
The first wavelength filter is a band pass filter.
The invention according to claim 6 is the invention according to claim 4,
The second wavelength filter of the reference wavelength light source unit is a band pass filter.
The invention according to claim 7 is the invention according to claim 5,
The first wavelength filter is a fiber grating formed by giving a periodic refractive index change in the longitudinal direction to the core of the optical fiber.
The invention according to claim 8 is the invention according to claim 6,
The second wavelength filter of the reference wavelength light source unit is a fiber grating formed by applying a periodic refractive index change in the longitudinal direction to the core of the optical fiber.
The invention according to claim 9
Fiber gratings having different reflection wavelengths are connected in cascade, the fiber gratings connected in cascade are installed in a measurement target, and a measured light output unit that outputs the measured light including reflected light from the fiber grating; and
9. The optical spectrum analyzer according to claim 1, wherein the measured light from the measured light output unit is input.

The present invention has the following effects.
According to Claims 1 to 8, the first wavelength filter provided in the front stage of the light combining unit filters light in a wavelength range that overlaps the reference light of the reference wavelength light source unit among the measured light, and the light combining unit includes: The measured light after filtering and the reference light are combined and output to the spectrometer. Then, from the wavelength measurement result obtained by the wavelength calculation means based on the sampling data of the spectrometer and the wavelength of the reference light, the judgment means obtains a wavelength error and confirms the accuracy of the wavelength measurement. There is no need to interrupt. Thereby, it is accurate and reliable in a short time, and the accuracy of wavelength measurement can be confirmed even during measurement. Accordingly, it is possible to quickly detect an abnormality or change in the optical signal.
According to the ninth aspect, since the optical spectrum analyzer according to any one of the first to sixth aspects measures the measured light from the measured light output unit, it is accurate and reliable in a short time, and is being measured. Even so, the accuracy of wavelength measurement can be confirmed. Accordingly, it is possible to quickly detect an abnormality or change in the optical signal.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment (optical fiber sensor system) of the present invention. Here, the same components as those in FIG. 4 are denoted by the same reference numerals, and description thereof is omitted.
The measured light output unit 50 includes an ASE light source 51, a circulator 52, and a plurality of FBGs 53 (1) and 53 (2) having different reflection wavelengths, and is used to measure physical quantities such as displacement, weight, pressure, and acceleration of the measurement target. The optical signal based on this is output to the optical spectrum analyzer SA. The ASE light source 51, the circulator 52, and the FBGs 53 (1) and 53 (2) are connected by optical fibers.

  The ASE light source 51 is a broadband light source, and outputs continuous spectrum light having a predetermined optical power at least in the second wavelength range. The ASE light source 51 preferably outputs continuous spectrum light having the same optical power per unit wavelength width.

  The circulator 52 outputs the light from the ASE light source 51 to the FBGs 53 (1) and 53 (2), and outputs the optical signals reflected by the FBGs 53 (1) and 53 (2) to the optical spectrum analyzer SA.

  The FBGs 53 (1) and 53 (2) reflect light having a desired wavelength in ASE (amplified spontaneous emission). Note that the FBGs 53 (1) and 53 (2) are connected in cascade, have different reflection wavelengths, and are installed on the measurement target. For example, the FBG 53 (1) reflects light having the wavelength λ1 in the ASE, and the FBG 53 (2) reflects light having the wavelength λ2 (λ1 ≠ λ2) in the ASE.

  Note that FBG 53 (1) and 53 (2) are a kind of fiber grating, and the fiber bug rating is, for example, edited by Shunichi Tanaka, Yasuharu Suematsu, Takayoshi Ohkoshi, “Optoelectronic Glossary”, Ohmsha, 1996, As shown in the first edition, pp 424 to 425, there are a plurality of types of blazed gratings, chirped gratings, etc. in addition to FBGs 53 (1) and 53 (2), but FBGs 53 (1) and 53 having high wavelength selectivity. (2) is most preferred.

  The FBGs 53 (1) and 53 (2) are diffraction gratings in which a periodic refractive index change is formed in the longitudinal direction on the core of the optical fiber, and the reflected wavelength is determined by the period of the refractive index change. And the high wavelength selectivity is implement | achieved by changing the refractive index of a core periodically to a longitudinal direction. The period of the refractive index change varies depending on the temperature at which the FBGs 53 (1) and 53 (2) are installed, the temperature applied to the FBGs 53 (1) and 53 (2), pressure, strain, and the like. That is, by monitoring the wavelength of the optical signal that is the reflected light from each of the FBGs 53 (1) and 53 (2), physical quantities such as displacement, weight, pressure, and acceleration can be measured.

  The optical spectrum analyzer SA includes the spectroscope 10, the reference wavelength light source unit 20, the optical coupler 30, and the arithmetic unit 40 shown in FIG. 4, and is connected to the measured light output unit 50 through an optical fiber. The reference wavelength light source unit 20 is, for example, a gas laser, and has a narrow spectral line width and a predetermined wavelength λ3 (for example, λ1≈λ3, and the spectra of the reference light and the reflected light overlap each other) as in FIG. A reference light having a large light output peak is output. The reference light output from the reference wavelength light source unit 20 has very little wavelength fluctuation and high wavelength stability. Further, the wavelength of the reference light is set in advance so as not to overlap the first wavelength range and to be within the second wavelength range in which the spectrometer 10 can measure the measured light.

  Further, the optical spectrum analyzer SA has an FBG 60. The FBG 60 is a first wavelength filter, to which the measured light including the optical signal from the measured light output unit 50 (that is, the reflected light of the FBGs 53 (1) and 53 (2)) is input, and the wavelength of the reference light The light of λ3 is removed and output to the optical coupler 30. Note that the wavelength width filtered by the FBG 60 may be at least the spectral width of the reference light, but will be described as the spectral width of the reflected light of the FBGs 53 (1) and 53 (2) as an example.

  Here, FIG. 2 is a diagram illustrating an example of light characteristics in each unit. In FIG. 2, the horizontal axis is the wavelength, and the vertical axis is the optical power. 2A shows the measured light output from the measured light output unit 50, FIG. 2B shows the measured light after filtering by the FBG 60, and FIG. 2C shows the reference wavelength. Reference light from the light source unit 20 is shown in FIG. 2D, which is combined light (combined light of measured light and reference light) combined by the optical coupler 30. The optical signals 100 and 101 are reflected light from the FBGs 53 (1) and 53 (2), and the reference light 102 is light from the reference wavelength light source unit 20.

Subsequently, the operation of the apparatus shown in FIG. 1 will be described.
First, the normal measurement, that is, the case of measuring the light to be measured will be described. The switch of the reference wavelength light source unit 20 is turned off to stop the output of the reference light 102. On the other hand, ASE is output from the ASE light source 51 and output to the FBGs 53 (1) and 53 (2) via the circulator 52. Then, the FBGs 53 (1) and 53 (2) reflect the light of the wavelengths λ 1 and λ 2 in the ASE and output the reflected light to the circulator 52.

  Then, the circulator 52 outputs the reflected lights 100 and 101 from the FBGs 53 (1) and 53 (2) to the optical spectrum analyzer SA (see FIG. 2A).

  Further, the FBG 60 of the optical spectrum analyzer SA filters light having a predetermined wavelength width λ3 ± Δλ centered on the wavelength λ3 from the measured light, and outputs the measured light after filtering to the optical coupler 30 (FIG. 2 (b)).

  Then, only the light to be measured is input to the spectroscope 10 via the optical coupler 30, and the spectroscope 10 samples the light to be measured for each desired wavelength width, for example, from the short wavelength side, and the wavelength and the optical power. Related measurement data is output to the calculation unit 40. And the wavelength calculating means 41 of the calculating part 40 calculates | requires the wavelength of each optical signal. That is, peak data is detected, and a wavelength corresponding to the detected peak data is obtained. Then, the calculation unit 40 displays the wavelength obtained by the wavelength calculation unit 41, for example, on a screen of a display unit (not shown) or outputs it to an external device (not shown).

  An analysis unit (not shown) analyzes the wavelength from the calculation unit 40, measures physical quantities such as displacement, weight, pressure, acceleration, etc. of the measurement target, analyzes temporal changes in the wavelength, Obtain temporal changes in physical quantities.

  Note that although the optical signal 100 that is the reflected light from the FBG 53 (1) cannot be measured, it is outside the first wavelength range that is the measurement range, so there is almost no influence even if the measurement cannot be performed.

  Next, a case where wavelength accuracy is confirmed (also referred to as wavelength calibration or wavelength adjustment), that is, a case where the reference light of the reference wavelength light source unit 20 is measured will be described.

  Here, the operation until the light to be measured filtered by the FBG 60 is input to the optical coupler 30 is the same as that in normal measurement, and thus the description thereof is omitted.

  On the other hand, the switch of the reference wavelength light source unit 20 is turned on, and the reference wavelength light source unit 20 outputs the reference light 102 (see FIG. 2C). Then, the optical coupler 30 combines the reference light from the reference wavelength light source unit 20 and the measured light from the FBG 60, and outputs the combined light to the spectrometer 10 (see FIG. 2D).

  Then, the spectroscope 10 outputs measurement data having a relationship between the wavelength and the optical power to the calculation unit 40 in the same manner as in normal measurement. Then, the wavelength calculation means 41 of the calculation unit 40 detects the peak data of the reference light, obtains the wavelength corresponding to the detected peak data, and outputs the obtained wavelength to the determination means 42. Since the wavelength of the reference light is determined in advance, the wavelength that is closest to the wavelength of the reference light among the obtained wavelengths is output.

  Then, the judging means 42 compares the wavelength of the reference light peak data obtained by the wavelength calculating means 41 with a predetermined wavelength of the reference light. If the wavelength error is within a desired range, it is accurate. Judge that measurement is possible. On the other hand, if the wavelength error is not within the desired range, it is determined that there is a failure. For example, an alarm is displayed on the screen of a display unit (not shown) or an alarm signal is output to an external device (not shown).

  As described above, the FBG 60 filters light in a wavelength range that overlaps the reference light of the reference wavelength light source unit 20 among the measured light from the measured light output unit 50, and the optical coupler 30 performs the filtered measured light. And the reference light are combined and output to the spectrometer 10. Then, from the measurement data of the spectroscope 10, the wavelength calculation unit 41 performs wavelength measurement, and the determination unit 42 further confirms the accuracy of wavelength measurement based on the wavelength of the reference light and the wavelength measurement result obtained from the measurement data. There is no need to interrupt the measurement of the light under measurement. Thereby, it is accurate and reliable in a short time, and the accuracy of wavelength measurement can be confirmed even during measurement. Accordingly, it is possible to quickly detect an abnormality or change in the optical signal 101.

  Further, since the FBG 60 can be formed in an optical fiber that is a transmission path of light to be measured, the light is output from the optical fiber and transmitted or reflected through the optical filter like a wavelength filter using a dielectric multilayer film. There is no need to input the light again into the optical fiber. This facilitates alignment of the optical system of the apparatus.

  Further, since the optical spectrum analyzer SA measures the measured light from the measured light output unit 50, it is not necessary to interrupt the measurement of the measured light and check the accuracy of the wavelength measurement. Thereby, it is accurate and reliable in a short time, and the accuracy of wavelength measurement can be confirmed even during measurement. Accordingly, it is possible to quickly detect an abnormality or change in the optical signal.

The present invention is not limited to this, and may be as shown below.
(1) Although the determination means 42 has shown the structure which calculates | requires the wavelength error of the wavelength measurement result of the wavelength calculating means 41, and the wavelength of the reference light of the reference wavelength light source part 20, and confirms the accuracy of wavelength measurement, An error correction unit that corrects the wavelength measurement result of the wavelength calculation unit 41 based on the wavelength error 42 may be provided. Specifically, correction is performed by subtracting the wavelength error obtained by the determination means 42 from the result of wavelength measurement of the optical signal 101. Then, the value corrected by the error correction means by the calculation unit 40 is displayed as a calculation result, for example, on a screen of a display unit (not shown) or output to an external device (not shown). As described above, the error correction unit corrects the wavelength measurement result of the wavelength calculation unit 41 based on the wavelength error obtained by the determination unit 42, so that the wavelength of the optical signal 101 can be obtained with high accuracy.

(2) The configuration in which the optical coupler 30 synthesizes the measured light after filtering and the reference light is shown. However, the optical coupler 30 may not be an optical coupler as long as it can synthesize two lights.

(3) Although the reference wavelength light source unit 20 is configured to output one reference light, any number of reference lights may be output. For example, the reference light may be output on both sides of the first wavelength range, that is, on the longer wavelength side and the shorter wavelength side than the first wavelength range.

(4) As an example of the reference wavelength light source unit 20, a configuration using a gas laser has been shown. However, any light source may be used as long as the wavelength is stable and the spectrum width is narrow. For example, a broadband light source and an FBG (second wavelength filter) that reflects broadband light from the broadband light source may be combined, and the reflected light of the FBG may be used as the reference light. Here, FIG. 3 is a diagram illustrating another example of the reference wavelength light source unit 20, and the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof is omitted.

  In FIG. 3, the reference wavelength light source unit 20 includes an ASE light source 21, a circulator 22, and FBGs 23 (1) and 23 (2) that are a kind of broadband light source. The ASE light from the ASE light source 21 is input to the FBGs 23 (1) and 23 (2) through the circulator. The FBG 23 (1) reflects light having the wavelength λ3 in the ASE, and the FBG 23 (2) reflects light having the wavelength λ4. Then, the reflected lights 102 and 103 are output to the optical coupler 30 as the reference lights 102 and 103, respectively.

  As described above, since the FBGs 23 (1) and 23 (2) of the second wavelength filter reflect the light having the wavelength serving as the reference light, the reference light can be simply changed by changing the FBGs 23 (1) and 23 (2). Λ3 and λ4 can be easily changed.

  Of course, it is preferable to adjust the temperature of the FBG so that the period of the refractive index of the FBGs 23 (1) and 23 (2) does not change, or to use a silica-based optical fiber with a small period variation of the refractive index change. Alternatively, a second wavelength filter of a bandpass filter such as a dielectric multilayer film may be combined with a broadband light source, and light transmitted through the second wavelength filter may be used as reference light. An optical coupler may be used instead of the circulator 22. Further, a wavelength tunable light source may be used as the reference wavelength light source unit 20.

(5) As an example of the wavelength filter and the second wavelength filter, the configuration using the FBG 23 (1), 23 (2), 53 (1), 53 (2) is shown. Any material may be used, for example, a dielectric multilayer film. The filtering may be any of low pass, band pass, and high pass.

(6) The configuration using the ASE light source 51 is shown as an example of the broadband light source. However, any light source having a predetermined optical power at the reflection wavelengths of the FBGs 53 (1) and 53 (2) may be used. For example, a light emitting diode or a white light source may be used. Similarly, the ASE light source 21 may be any light source having a predetermined optical power at the reflection wavelengths of the FBGs 23 (1) and 23 (1), and may be, for example, a light emitting diode or a white light source.

(7) The light combining unit may combine not only the reference light and the light to be measured with the same optical power but also a ratio (for example, 1: 9).

(8) Although the reflected light from the optical fiber sensor has been described as an example of the input light to the optical spectrum analyzer SA, the WDM signal of the optical communication system may be used as the input light.

It is the block diagram which showed the 1st Example of this invention. It is the figure which showed an example of the characteristic of the light in each part in the system shown in FIG. It is the figure which showed an example of the structure of the reference | standard wavelength light source part 20 of the apparatus shown in FIG. It is the figure which showed the structure of the conventional optical spectrum analyzer. FIG. 5 is a diagram illustrating an example of light characteristics at each unit in the apparatus illustrated in FIG. 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Spectrometer 20 Reference wavelength light source part 21, 51 ASE light source 22, 52 Circulator 23 (1), 23 (3), 53 (1), 53 (2) FBG
30 Optical Coupler 41 Wavelength Calculation Unit 42 Determination Unit

Claims (9)

In an optical spectrum analyzer having a spectrometer that samples input light and outputs it as sampling data, and wavelength calculation means that performs wavelength measurement of the spectrum of the input light by sampling data from the spectrometer,
A reference wavelength light source unit that outputs reference light having optical power at a predetermined wavelength;
A first wavelength filter that receives light to be measured having an optical signal and outputs the light except the light of the predetermined wavelength;
A light combining unit that combines the reference light from the reference wavelength light source unit and the light filtered by the first wavelength filter and outputs the input light to the spectrometer;
An optical spectrum analyzer, comprising: a determination unit that obtains a wavelength error from the wavelength of the reference light of the reference wavelength light source unit and the wavelength measurement result measured by the wavelength calculation unit and confirms the accuracy of the wavelength measurement.   The optical spectrum analyzer according to claim 1, wherein the reference wavelength light source unit outputs a plurality of reference lights having different wavelengths.   3. The optical spectrum analyzer according to claim 1, wherein the reference wavelength light source unit is a gas laser. The reference wavelength light source is
A broadband light source;
3. The optical spectrum analyzer according to claim 1, further comprising a second wavelength filter that outputs only light of the predetermined wavelength out of light from the broadband light source.   The optical spectrum analyzer according to claim 1, wherein the first wavelength filter is a band pass filter.   5. The optical spectrum analyzer according to claim 4, wherein the second wavelength filter of the reference wavelength light source unit is a bandpass filter.   6. The optical spectrum analyzer according to claim 5, wherein the first wavelength filter is a fiber grating formed by applying a periodic refractive index change in the longitudinal direction to the core of the optical fiber.   7. The optical spectrum analyzer according to claim 6, wherein the second wavelength filter of the reference wavelength light source unit is a fiber grating formed by giving a periodic refractive index change in the longitudinal direction to the core of the optical fiber. Fiber gratings having different reflection wavelengths are connected in cascade, the fiber gratings connected in cascade are installed in a measurement target, and a measured light output unit that outputs the measured light including reflected light from the fiber grating; and
An optical fiber sensor system comprising: the optical spectrum analyzer according to claim 1, to which measured light from the measured light output unit is input.

Images