JPH08278225A - Measuring method of zero-dispersion wavelength - Google Patents

Abstract

PURPOSE: To obtain a measuring method in which the zero-dispersion wavelength of an optical fiber is measured with good accuracy. CONSTITUTION: In the measuring method of the zero-dispersion wavelength of an optical fiber, at least a beam of output light from one probing light source 7 and a beam of output light from one pumping light source 2 are composed 10, and a beam of output light which has been composed 10 is made incident on an optical fiber 5 to be measured. When the oscillation wavelength of the probing light source 7 is maintained to be constant and the oscillation wavelength of the pumping light source 2 is changed within a prescribed wavelength range, the oscillation wavelength of the probing light source 7 is changed into a plurality of wavelengths so as to be measured regarding the distribution of four-light-wave mixed power as the function of the oscillation wavelength of the pumping light source 2 radiated from the optical fiber 5 to be measured. A plurality of measured results are added or added and averaged for every wavelength position of the pumping light source 2, the oscillation wavelength of the pumping light source 2 giving the maximum value of the distribution of the four-light-wave mixed light power is decided, by which the zero-dispersion wavelength of the optical fiber 5 is found.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zero dispersion wavelength measuring method capable of accurately measuring the zero dispersion wavelength of an optical fiber.

[0002]

2. Description of the Related Art As a conventional method for measuring the zero-dispersion wavelength in an optical fiber, there is JP-A-6-331495 "Zero-dispersion wavelength measuring device and zero-dispersion wavelength measuring method". FIG. 2 shows a configuration example of a measuring device according to the related art. The measuring method by the present apparatus is such that the light outputted from the probe light source 1 and the wavelength tunable pump light source 2 are polarized by the polarization controller 3 and then multiplexed by the optical multiplexer 4, and then the optical fiber 5 is measured. input. The four-wave mixed light power generated in the optical fiber 5 to be measured is measured by the optical spectrum analyzer 6. The four-wave mixing optical power becomes maximum when the oscillation wavelength of the tunable pump light source matches the zero-dispersion wavelength of the optical fiber under measurement. Therefore, the oscillation wavelength of the tunable pump light source is swept to maximize the four-wave mixing optical power. This is a method of measuring the zero-dispersion wavelength of the optical fiber by obtaining the oscillation wavelength of the wavelength tunable pump light source showing the value.

[0003]

However, such a conventional technique has a serious drawback that it cannot cope with the case where the zero-dispersion wavelengths in the optical fiber are distributed in the longitudinal direction. I haven't arrived. This drawback will be specifically described below.

First, a case will be described in which the zero dispersion wavelength is extremely limited to a constant value in the length direction, such as a single optical fiber that does not include a connection point. FIG. 3 shows the zero dispersion wavelength (λ.).
The measurement results of the zero-dispersion wavelength by the conventional method are shown for a dispersion-shifted fiber 1 km with a wavelength of 1550 nm. The measurement is performed by fixing the oscillation wavelength (λprobe) of the probe light source to 1560 nm and measuring the four-wave mixing optical power obtained by sweeping the oscillation wavelength of the pump light source from 1545 nm to 1560 nm with an optical spectrum analyzer. It was The horizontal axis represents the oscillation wavelength of the pump light source, and the vertical axis represents the four-wave mixed light power. From this, when the oscillation wavelength of the probe light source matches the known zero-dispersion wavelength of the measured optical fiber, which is 1550 nm, it is true that the four-wave mixing optical power has a maximum value and a maximum value, and this wavelength is It can be seen that it is the zero dispersion wavelength of the measurement optical fiber. It is understood that the maximum value of the four-wave mixed light power is taken not only when the zero-dispersion wavelength of the measured optical fiber matches 1550 nm, but also at many other wavelengths.
The reason for this is, for example, "Kyo Inoue," Four-Wave Mixing in
an Optical Fiber in the Zero-Dispersion Wavelength
Region, "IEEE Journal of Lightwave Technology, vo
L. 10, no. 11, pp 1553-1561 (November 1992) ”, the four-wave mixing optical power is
This is because the oscillation wavelength of the pump light source (to be precise, the relative difference between the oscillation wavelength of the pump light source and the oscillation wavelength of the probe light source with respect to the zero-dispersion wavelength) is changed periodically. in this way,
It is known that the zero-dispersion wavelength has a constant value in the length direction. In extremely limited cases, the maximum and maximum values of the four-wave mixing light power match the zero-dispersion wavelength of the measured optical fiber. Even in the prior art, the zero dispersion wavelength in the fiber could be measured for the time being.

However, in a general optical communication system, it is usual that a line is constructed by cascading a plurality of optical fibers of different manufacturing lots, and the zero-dispersion wavelength in the optical fiber is long when viewed from the entire system length. Since the zero-dispersion wavelength is distributed in the depth direction, it is indispensable to be able to measure the zero-dispersion wavelength even when the zero-dispersion wavelength is not constant in the length direction but is distributed.

Then, the serious problem of the conventional method that occurs in the case where the zero-dispersion wavelengths are distributed in the lengthwise direction is pointed out. Figure 4 shows a dispersion-shifted fiber with a zero-dispersion wavelength (λ) of 1548 nm, 1550 nm, and 1552 nm, and a 2.1-km dispersion-shifted fiber obtained by cascading 0.8 km, 0.5 km, and 0.8 km, respectively. The results of measuring the zero-dispersion wavelength of the link by the conventional method are shown. The measurement is performed by fixing the oscillation wavelength of the probe light source to 1565 nm and changing the oscillation wavelength of the pump light source from 1545 nm to 1555 nm by 0.2 nm.
The four-wave mixed light power obtained by sweeping each time was measured by an optical spectrum analyzer. From this, it can be confirmed that when the oscillation wavelength of the probe light source coincides with the known zero-dispersion wavelength of the measured optical fiber, which is 1548 nm, 1550 nm, and 1552 nm, the four-wave mixing optical power surely takes the maximum value. It was

However, the maximum value is different from when the oscillation wavelength of the probe light source coincides with the zero-dispersion wavelength of the optical fiber to be measured. For example, the maximum wavelength λ is 1548.7 nm and 1553.5 nm.
, 1555 nm, etc., and the maximum value of the four-wave mixing light power does not necessarily correspond to the zero-dispersion wavelength of the measured optical fiber. Therefore, when the zero-dispersion wavelength of the measured optical fiber is unknown and is not constant in the length direction but is distributed, the maximum value of the observed four-wave mixing light power is equal to the oscillation wavelength of the pump light source. It was impossible to distinguish whether the zero-dispersion wavelengths of the optical fibers to be measured coincided with each other or the periodic fluctuations with respect to the oscillation wavelength of the pump light source caused. Also,
The magnitude relationship between the maximum values of the four-wave mixed light power is also due to the length of each constituent fiber having different zero-dispersion wavelength, or based on the relative difference between the oscillation wavelength of the pump light source and the oscillation wavelength of the probe light source with respect to the zero-dispersion wavelength. It was impossible to distinguish whether or not it was simply due to periodic fluctuations. As described above, in the practical case where the zero-dispersion wavelength is distributed in the fiber length direction, it is impossible to measure the zero-dispersion wavelength in the optical fiber by the conventional technique.

Therefore, the present invention provides a zero-dispersion wavelength measuring method capable of accurately measuring the zero-dispersion wavelength of an optical fiber in a realistic case where the zero-dispersion wavelength is distributed in the length direction of the optical fiber. With the goal.

[0009]

In order to solve the above problems, in the method for measuring a zero dispersion wavelength according to claim 1 of the present invention,
Output light of one probe light source and output light of one pump light source are combined, the combined output light is made incident on the optical fiber to be measured, and the oscillation wavelength of the probe light source is kept constant, When the wavelength is changed in a predetermined wavelength range, the distribution of the four-wave mixed light power as a function of the wavelength of the pump light source emitted from the optical fiber under measurement is measured, and the oscillation wavelength of the probe light source is changed. A plurality of same measurements are performed, and the plurality of measurement results are added or averaged at each wavelength position of the pump light source to determine the oscillation wavelength of the pump light source that gives the maximum value of the distribution of the four-wave mixed light power. It is characterized in that the zero dispersion wavelength of the optical fiber is obtained by.

In the zero-dispersion wavelength measuring method according to the second aspect of the present invention, the output lights of one probe light source and one pump light source are multiplexed, and the combined output light is incident on the optical fiber to be measured. And, when the oscillation wavelength difference between the probe light source and the pump light source is kept constant and the oscillation wavelength of the pump light source is changed within a predetermined wavelength range, the pump light source emitted from the optical fiber under test. The distribution of the four-wave mixed light power as a function of the oscillation wavelength is measured, the same measurement is performed a plurality of times while changing the oscillation wavelength difference, and the plurality of measurement results are added or added at each wavelength position of the pump light source. On average, by determining the oscillation wavelength of the pump light source that gives the maximum of the distribution of the four-wave mixed light power,
It is characterized in that the zero dispersion wavelength of the optical fiber is obtained.

In the zero-dispersion wavelength measuring method according to a third aspect of the present invention, the oscillation wavelength of the probe light source is set to a shorter wavelength side than the oscillation wavelength of the pump light source. The zero dispersion wavelength of the optical fiber is obtained by the method for measuring the zero dispersion wavelength of the optical fiber described above.

In the zero-dispersion wavelength measuring method according to claim 4 of the present invention, the oscillation wavelength of the probe light source is set to a longer wavelength side than the oscillation wavelength of the pump light source.
Alternatively, the zero dispersion wavelength of the optical fiber is obtained by the method for measuring the zero dispersion wavelength of the optical fiber described in 2.

In the zero-dispersion wavelength measuring method according to claim 4 of the present invention, the results measured by the measuring method according to claim 3 or 4 are further added or averaged to obtain the maximum distribution of the four-wave mixed light power. The zero-dispersion wavelength of the optical fiber is obtained by determining the oscillation wavelength of the pump light source that gives a value.

In the zero-dispersion wavelength measuring method according to claim 5 of the present invention, the results measured by the measuring method according to claim 3 or 4 are further added or averaged, and the distribution of the four-wave mixed light power is maximized. The zero-dispersion wavelength of the optical fiber is obtained by determining the oscillation wavelength of the pump light source that gives a value.

In the zero-dispersion wavelength measuring method according to claim 6 of the present invention, the measuring method according to any one of claims 1 to 5 is performed by switching the incident end and the emitting end of the optical fiber to be measured. The zero dispersion wavelength of the optical fiber is obtained by further adding or averaging the measurement results before and after the replacement and determining the oscillation wavelength of the pump light source that gives the maximum value of the four-wave mixing light power. .

[0016]

According to the measuring method of the present invention, as in the conventional method, the four-wave mixed light power reaches the maximum value and the maximum value only when the oscillation wavelength of the pump light source matches the zero dispersion wavelength of the optical fiber to be measured. Utilizing the well-known fact of taking.

However, only by utilizing this fact, accurate measurement cannot be performed when the zero dispersion wavelength is not constant and distributed in the length direction of the optical fiber as described above.
Therefore, in the present invention, when the oscillation wavelength of the pump light source with respect to the zero-dispersion wavelength and the oscillation wavelength of the probe light source are variously changed, the wavelength position showing the maximum power of the four-wave mixed light emitted from the optical fiber under measurement is determined. , The fact that there is no change at the wavelength position corresponding to the zero-dispersion wavelength, but the value of the power of the four-wave mixed light that occurs at a wavelength other than the zero-dispersion wavelength varies variously in accordance with the change in the oscillation wavelength. Are using. That is, if the oscillation wavelength of the pump light source with respect to the zero-dispersion wavelength and the power distribution of the four-wave mixed light obtained by variously changing the oscillation wavelength position of the probe light source are added for each oscillation wavelength position of the pump light source, The power value of the four-wave mixed light at the wavelength position of the zero-dispersion wavelength increases with the number of additions, but the power value of the four-wave mixed light generated at a wavelength other than the zero-dispersion wavelength has a maximum value for each measurement case. Since the wavelength position showing the minimum value is slightly shifted, it becomes 4 when added.
The periodic fluctuations of the light wave mixing light power are canceled and the dependence on the oscillation wavelength of the pump light source becomes flat. Therefore, the fact that the wavelength position giving the maximum value caused by the zero-dispersion wavelength can be very easily identified by adding or averaging the plurality of measurement results described above is utilized. Further, when the zero-dispersion wavelength is distributed in the length direction of the optical fiber, the four-wave mixing optical power of the zero-dispersion wavelength on the incident side is relatively large due to the attenuation of light in the measured optical fiber. , The power of the four-wave mixed light of zero dispersion wavelength on the emission side tends to appear relatively small. In consideration of this, in this measurement method, the incident end and the emission end are exchanged and the same measurement results are added. And get more accurate results.

[0018]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

The first embodiment will be described. In Figure 5,
The relationship between the pump light wavelength dependency of the four-wave mixed light power obtained by the first embodiment and the known zero dispersion wavelength (λ) is shown. FIG. 1 shows a zero-dispersion wavelength measuring device used in this embodiment. Optical fiber to be measured 5 to be measured in the present embodiment
Is composed of 2.1 km optical fibers obtained by cascade-connecting 0.8 km, 0.5 km, and 0.8 km of dispersion-shifted fibers with zero-dispersion wavelengths of 1548 nm, 1550 nm, and 1552 nm, respectively.

The measurement of the zero dispersion wavelength of the optical fiber to be measured is
First, the variable wavelength probe light source 7 and the variable wavelength pump light source 2
After the polarization plane of the output light is adjusted by the polarization controller 3, it is combined by the optical fiber coupler 10, and the combined output light is incident on the optical fiber 5 to be measured, and the probe light source 7 oscillates. The wavelength is tuned in the range of 1530 nm to 1537 nm, which is shorter than the oscillation wavelength of the pump light source 2, in 1 nm steps, and the oscillation wavelength of the pump light source 2 is changed from 1545 nm to 1555 nm in 0.2 nm steps each time. Swept.

The distribution value of the four-wave mixed light power (hereinafter, simply referred to as a distribution value) as a function of the pump light source wavelength contained in the output light emitted from the optical fiber 5 to be measured, obtained at this time, is used as an optical spectrum analyzer. The same measurement was performed multiple times according to No. 6.

A plurality of measurement results corresponding to the changed oscillation wavelength of the probe light source were added and averaged for each wavelength position of the oscillation wavelength of the pump light source. This is plotted in FIG. 5 with the averaging value (hereinafter simply referred to as the distribution addition value) of the distribution values of the four-wave mixed light power as the vertical axis and the oscillation wavelength of the pump light source 2 as the horizontal axis. For easy understanding, the known zero-dispersion wavelengths are 1548 nm, 1550 nm, and 1552 n.
The position on the horizontal axis of m (λ.) is indicated by an arrow. It should be noted that the distributions measured are the same, but the scales of the optical powers are changed by simply adding instead of averaging.

From FIG. 5, the oscillation wavelength of the pump light source is 1548 nm, 1550, which is the known zero dispersion wavelength of the optical fiber to be measured.
There is a maximum at each wavelength position corresponding to nm and 1552 nm.
Although a minute peak can be seen at a wavelength position other than the zero-dispersion wavelength, its size is very small compared to the maximum value at the zero-dispersion wavelength position, and it is extremely easy to distinguish between them. Therefore, it can be seen that the zero-dispersion wavelength of the optical fiber to be measured can be measured very accurately from the oscillation wavelength of the pump light source that gives the maximum distribution added value. In this embodiment, the oscillation wavelength of the probe light source is set on the shorter wavelength side than the oscillation wavelength of the pump light source, but the same tendency is exhibited on the longer wavelength side.

The second embodiment will be described. In Figure 6,
The relationship between the distribution addition value obtained by the second embodiment and the known zero-dispersion wavelength (λ) is shown. Measured optical fiber 5 is the first
The configuration is the same as that of the above embodiment. To measure the zero-dispersion wavelength of the optical fiber to be measured, first, the tunable probe light source 7 and
The output light from the wavelength tunable pump light source 2 is converted into the optical fiber coupler 10
The combined output light is input to the optical fiber 5 to be measured, and the oscillation wavelength of the probe light source 7 is set to 1530.
The wavelength of the pump light source 2 is changed from 1545 nm to 1555 nm by 0.2 nm each time in the range of 1 nm to 1537 nm.
Swept every time.

The distribution value of the output light emitted from the optical fiber 5 to be measured obtained at this time is measured by the optical spectrum analyzer 6 for each of a plurality of different oscillation wavelengths of the probe light source 7, and the respective averages are added, The distribution addition value was calculated.

Next, the incident end and the emitting end of the optical fiber 5 to be measured were replaced with each other, and the same measurement and arithmetic averaging were performed to obtain the distribution addition value. The distribution added values before and after the exchange of the incident end and the emission end were further averaged to obtain a target distribution added value, which was plotted in FIG.

From FIG. 6, the oscillation wavelength of the pump light source is 1548 nm, 1550 which is the known zero dispersion wavelength of the optical fiber to be measured.
There is a maximum at each wavelength position corresponding to nm and 1552 nm.
Although minute peaks can be seen at wavelength positions other than the zero-dispersion wavelength, they are extremely small compared to the maximum value at the zero-dispersion wavelength position, and it is extremely easy to distinguish between them. Therefore, it can be seen that the zero-dispersion wavelength of the optical fiber to be measured can be measured very accurately from the oscillation wavelength of the pump light source that gives the maximum distribution added value.

In this embodiment, the fiber to be measured is
The optical fiber lengths of the zero-dispersion wavelengths of 1548 nm and 1552 nm are the same 0.8 km, and the maximums of the same magnitude −55 dBm appear at those wavelength positions correspondingly, and in the case of Example 1 shown in FIG. , Zero dispersion wavelength is 1552 nm
The former appears smaller because it enters from the end on the side of, while the measurement accuracy is improved. This is due to the effect of mutually adding the results of measurements with the entrance end and the exit end of the optical fiber switched.

The third embodiment will be described. In Figure 7,
The relationship between the distribution addition value obtained by the third embodiment and the known zero-dispersion wavelength (λ) is shown. The optical fiber 5 to be measured also has the same configuration as the above-described embodiments. The measurement of the zero-dispersion wavelength of the optical fiber to be measured is performed by the tunable probe light source 7
The output light from the wavelength tunable pump light source 2 is converted into the optical fiber coupler 10
The combined output light is incident on the optical fiber 5 to be measured, and the oscillation wavelength of the probe light source 7 is 1530 nm, which is shorter than the emission wavelength of the pump light source 2.
To 1537 nm, and from 1563 nm to 1570 nm, which is on the longer wavelength side than the emission wavelength of the same light source, the emission wavelength of the pump light source 2 is changed by 1 nm each time.
Sweep was performed from 5 nm to 1555 nm in 0.2 nm steps. The distribution value of the four-wave mixed light power included in the output light emitted from the measured optical fiber 5 obtained at this time was measured by the optical spectrum analyzer 6, and the distribution addition value was obtained by averaging each. This is plotted in FIG.

From FIG. 7, the oscillation wavelength of the pump light source is 1548n, which is the known zero-dispersion wavelength (λ.) Of the optical fiber to be measured.
There is a maximum at each wavelength position corresponding to m 1, 1550 nm, and 1552 nm. Although minute peaks can be seen at wavelength positions other than the zero-dispersion wavelength, they are extremely small compared to the maximum value at the zero-dispersion wavelength position, and it is extremely easy to distinguish between them. Therefore,
It can be seen that the zero-dispersion wavelength of the measured optical fiber can be measured very accurately from the oscillation wavelength of the pump light source that gives the maximum of the distribution added value.

The fourth embodiment will be described. Figure 8
The relationship between the distribution addition value obtained by the fourth embodiment and the known zero-dispersion wavelength (λ) is shown. The optical fiber 5 to be measured has the same configuration as the above-described embodiments. The measurement of the zero-dispersion wavelength of the optical fiber to be measured is performed by the tunable probe light source 7
The output light from the wavelength tunable pump light source 2 is converted into the optical fiber coupler 10
1530 nm, in which the output wavelength of the probe light source 7 is shorter than the emission wavelength of the pump light source 2, and the combined output light is input to the optical fiber 5 to be measured.
To 1537 nm and from 1563 nm to 1570 nm, which is the long wavelength side of the emission wavelength of the same light source, every 1 nm, the emission wavelength of the pump light source 2 is changed to 1545 nm.
To 1555 nm was swept in 0.2 nm steps. The distribution value of the four-wave mixed light power included in the output light emitted from the measured optical fiber 5 obtained at this time is measured by the optical spectrum analyzer 6 for a plurality of different oscillation wavelengths of the probe light source 7, and the distribution addition is performed. The value was calculated.

Next, the incident end and the emitting end of the optical fiber 5 to be measured were replaced with each other, and the same measurement and arithmetic averaging were performed to obtain the distribution addition value. The distribution added values before and after the exchange of the incident end and the emission end were further averaged to obtain a target distribution added value and plotted in FIG.

From FIG. 8, the oscillation wavelength of the pump light source is 1548n, which is the known zero-dispersion wavelength (λ.) Of the optical fiber to be measured.
There is a maximum at each wavelength position that coincides with m, 1550 nm, and 1552 nm. Although minute peaks can be seen at wavelength positions other than the zero-dispersion wavelength, they are extremely small compared to the maximum value at the zero-dispersion wavelength position, and it is extremely easy to distinguish between them. Therefore,
It can be seen that the zero-dispersion wavelength of the measured optical fiber can be measured very accurately from the oscillation wavelength of the pump light source that gives the maximum of the distribution added value. In addition, in this embodiment, the measurement accuracy is improved as compared with the third embodiment of FIG. 7 by adding the result of the measurement in which the entrance end and the exit end of the optical fiber are exchanged.

In the embodiment described above, the oscillation wavelength of the pump light source is swept while the oscillation wavelength of the probe light source is constant, but the oscillation wavelength difference between the probe light source and the pump light source is constant. Similar results are obtained when the oscillation wavelength of the pump light source is swept in this state. For example, even when the oscillation wavelength difference between the two light sources was changed to 1 nm and 5 nm, the same result as above could be obtained.

Needless to say, the zero-dispersion wavelength of not only the optical fiber but also other optical waveguides can be similarly measured.

[0036]

As described above, the zero-dispersion wavelength measuring method according to the present invention can measure the zero-dispersion wavelength of an optical waveguide such as an optical fiber with extremely high accuracy. That is, if the oscillation wavelength of the pump light source with respect to the zero-dispersion wavelength and the power distribution of the four-wave mixed light obtained by variously changing the oscillation wavelength position of the probe light source are added for each oscillation wavelength position of the pump light source, The power value of the four-wave mixed light at the wavelength position of the zero-dispersion wavelength increases with the number of additions, but the power value of the four-wave mixed light generated at a wavelength other than the zero-dispersion wavelength has a maximum value for each measurement case. Since the wavelength positions showing the minimum are slightly shifted, when added, the periodic fluctuation of the four-wave mixing light power is canceled and the dependence on the oscillation wavelength of the pump light source becomes flat. By adding or averaging the measurement results of, the wavelength position giving the maximum value generated by the zero-dispersion wavelength can be identified and measured very easily.

[Brief description of drawings]

FIG. 1 is a zero-dispersion wavelength measuring device used in an embodiment of the present invention.

FIG. 2 is an example of a zero-dispersion wavelength measuring device according to the prior art.

FIG. 3 shows the relationship between the distribution of four-wave mixed light power and the zero-dispersion wavelength of the optical fiber when the zero-dispersion wavelength is constant in the length direction of the optical fiber, which is obtained by the conventional method.

FIG. 4 is a relationship between the distribution of the four-wave mixed light power and the zero-dispersion wavelength of the optical fiber when the zero-dispersion wavelength is distributed in the length direction of the optical fiber, obtained by the conventional method.

FIG. 5 is a relationship between the distribution of the four-wave mixing light power as a function of the pump light source wavelength and the zero-dispersion wavelength of the optical fiber, which is obtained based on the first embodiment.

FIG. 6 shows the relationship between the distribution of the four-wave mixing light power as a function of the pump light source wavelength and the zero-dispersion wavelength of the optical fiber, obtained based on the second embodiment.

FIG. 7 shows the relationship between the distribution of the four-wave mixing light power as a function of the pump light source wavelength and the zero-dispersion wavelength of the optical fiber, obtained based on the third embodiment.

FIG. 8 is a relationship between the distribution of the four-wave mixing light power as a function of the pump light source wavelength and the zero-dispersion wavelength of the optical fiber, which is obtained based on the fourth embodiment.

[Explanation of symbols]

 1: Probe light source 2: Variable wavelength pump light source 3: Polarization controller 4: Optical multiplexer 5: Optical fiber under test 6: Optical spectrum analyzer 7: Variable probe light source 10: Optical fiber coupler

Claims (6)

[Claims] 1. A probe light source and an output light of a pump light source are combined, the combined output light is incident on an optical fiber to be measured, and the oscillation wavelength of the probe light source is kept constant. Measuring the distribution of the four-wave mixed light power as a function of the oscillation wavelength of the pump light source emitted from the optical fiber under test when the oscillation wavelength of the pump light source is changed within a predetermined wavelength range. A plurality of the same measurements are performed by changing the oscillation wavelength of the light source, and the plurality of measurement results are added or averaged at each wavelength position of the pump light source to give the maximum value of the distribution of the four-wave mixed light power. A method for measuring the zero-dispersion wavelength of an optical fiber, characterized in that the zero-dispersion wavelength of the optical fiber is determined by determining the oscillation wavelength of the optical fiber. 2. A probe light source and an output light of one pump light source are combined, the combined output light is incident on an optical fiber to be measured, and the oscillation wavelengths of the probe light source and the pump light source are combined. Distribution of the four-wave mixed light power as a function of the oscillation wavelength of the pump light source emitted from the optical fiber under measurement when the oscillation wavelength of the pump light source is changed within a predetermined wavelength range while keeping the difference constant. Is measured, the same measurement is performed a plurality of times while changing the oscillation wavelength difference, and the plurality of measurement results are added or averaged at each wavelength position of the pump light source to obtain the maximum value of the distribution of the four-wave mixed light power. A method for measuring the zero-dispersion wavelength of an optical fiber, characterized in that the zero-dispersion wavelength of the optical fiber is obtained by determining the oscillation wavelength of the pump light source that gives 3. The method for measuring the zero-dispersion wavelength of an optical fiber according to claim 1, wherein the oscillation wavelength of the probe light source is set to a shorter wavelength side than the oscillation wavelength of the pump light source. 4. The method for measuring the zero-dispersion wavelength of an optical fiber according to claim 1, wherein the oscillation wavelength of the probe light source is set to a longer wavelength side than the oscillation wavelength of the pump light source. 5. The oscillation wavelength of the pump light source that gives the maximum value of the distribution of the four-wave mixed light power is further determined by adding or averaging the results measured by the measuring method according to claim 3 or 4. , A method for measuring the zero-dispersion wavelength of an optical fiber, characterized in that the zero-dispersion wavelength of the optical fiber is obtained. 6. The measuring method according to claim 1, wherein the entrance end and the exit end of the optical fiber to be measured are interchanged, and the measurement results before and after the interchange are further added or arithmetically averaged. The zero-dispersion wavelength of the optical fiber is determined by determining the oscillation wavelength of the pump light source that gives the maximum value of the four-wave mixed light power. Dispersion wavelength measurement method.