JP2003139655A - Apparatus and method for measurement of characteristic of optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for the measurement of the characteristic of an optical fiber wherein the measurement of a wavelength dispersion characteristic and the measurement of a nonlinear constant can be performed by one optical fiber measuring apparatus, the structure of the apparatus can be simplified, the number of operating processes in the measurements can be reduced and costs related to the apparatus can be reduced. SOLUTION: With reference to the measurement of the wavelength dispersion characteristic and the measurement of the nonlinear constant, a light source used to generate two beams of light, a light modulation means, a directional coupling means and the like are not installed separately but are constituted of a common apparatus, a clock signal is supplied to the light modulation means when the wavelength dispersion characteristic is measured by a computing means, and a signal at a fixed level is supplied to the light modulation means when the nonlinear constant is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber characteristic measuring apparatus and its measuring method, and more particularly to a measuring apparatus and its measuring method for measuring chromatic dispersion distribution and non-linear constant of an optical fiber.

[0002]

2. Description of the Related Art Currently, in the field of ultra-high-speed optical communication, various studies are being conducted on communication quality control and compensation techniques for optical fiber lines in order to achieve and maintain high communication quality. Along with this, the market demand for optical fiber characteristic evaluation is higher than ever.

Among optical fiber characteristics, chromatic dispersion characteristics are particularly important for limiting transmission speed and wavelength band, and nonlinear refractive index is an important item for determining transmission limitation due to accumulation of signal distortion. Has been done.

Dispersion and non-linear optical phenomena are one of the factors that hinder the speeding up of transmission signals and wavelength division multiplexing in optical communication systems. Among these factors, chromatic dispersion is a phenomenon in which the speed of a transmission signal propagating through an optical fiber differs depending on each wavelength. Then, in order to minimize the deterioration of the transmission signal due to chromatic dispersion, it is necessary to control the chromatic dispersion value in the optical transmission line.

The non-linear optical phenomenon is a phenomenon in which distortion of signals propagating in an optical fiber for several thousand km is accumulated, and has a close relationship with the power density in the optical fiber. Therefore, the nonlinear refractive index is an essential parameter for constructing a communication system. Therefore, in an optical communication system, a technique for accurately measuring a nonlinear constant necessary for calculating a wavelength dispersion characteristic and a nonlinear refractive index of an optical fiber is important.

For measuring such chromatic dispersion characteristics, for example, four-wave mixing light generated by the interaction of optical pulses of two different wavelengths into the fiber under test and the interaction of the optical pulses of different wavelengths is used. One wavelength component of the backscattered light is cut out by an optical bandpass filter,
Japanese Unexamined Patent Publication No. 10-83006 discloses a technique for measuring the dispersion distribution in the longitudinal direction of an optical fiber to be measured by measuring with a TDR (0ptical Time Domain Reflectometer).

FIG. 4 shows the configuration of a conventional chromatic dispersion distribution measuring apparatus, and its measuring method will be described. As shown in FIG. 4, the conventional chromatic dispersion distribution measurement apparatus uses the light source LS.
1 (LS: Laser Source), light source LS2, and optical coupler A
, AO modulator 11, optical fiber amplifier 12, directional coupler 13, optical fiber 14, terminator 15, and optical band pass filter 16 (OBPF: Optical Band Pass Fi).
lter) and OTDR17 (OTDR: 0ptical Time Domain)
Reflectometer) and PC18 (PC: Personal Compute)
r) and.

The light source LS1 produces coherent light of wavelength λ _{1 and} the light source LS2 produces coherent light of wavelength λ ₂ , and these emitted lights are combined by the optical coupler A. The light synthesized by the optical coupler A is A
The O modulator 11 shapes the pulse in synchronization with the clock signal supplied from the PC 18, and the optical fiber amplifier 12 amplifies the pulse.

The light amplified by the optical fiber amplifier 12 is emitted by the directional coupler 13 to the optical fiber 14 to be measured. Further, the directional coupler 13 guides the total backscattered light generated by the light incident on the optical fiber 14 to the optical bandpass filter 16. The optical bandpass filter 16 transmits only a specific wavelength, and
Give to 17. The terminator 15 suppresses Fresnel reflection at the far end of the optical fiber 14. In the optical bandpass filter 16, one of the wavelength components of the backscattered light of the four-wave mixed light generated by the interaction of the incident two wavelengths out of the total backscattered light due to the optical pulse signal input to the optical fiber under measurement. The action of cutting out.

The OTDR 17 uses the optical bandpass filter 16 to transmit a specific wavelength light that transmits only one wavelength component of the backscattered light of the four-wave mixed light generated by the interaction of the two incident wavelengths of the total backscattered light. Is received and data is calculated. The intensity variation data calculated by the OTDR 17 is stored in the RAM in the PC 18 and used for the dispersion distribution calculation.

Next, a conventional procedure for measuring the chromatic dispersion distribution characteristic will be described below with reference to a flowchart of FIG. As shown in FIG. 4, the chromatic dispersion distribution characteristic is measured by the following procedure with the optical fiber 14 connected to the measuring device.

(1) Two light sources LS1 and L having different wavelengths
The measurement conditions such as S2, OTDR 17 and optical fiber amplifier 12 are set (step S51). (2) After setting the measurement conditions in step S51, OTDR1
The measurement of the intensity fluctuation data of the optical fiber 14 to be measured is executed by 7 (step S52). (3) The measurement data measured in step S52 is sent to the PC 18
(Step S53). (4) The PC 18 processes the measurement data from the OTDR 17 to execute the calculation processing of the chromatic dispersion value and the like (step S54). (5) The numerical value and the waveform of the chromatic dispersion value and the total dispersion value obtained by the process of step S54 are displayed on the display unit (not shown) (step S55).

Regarding the conventional method for measuring the non-linear constant, FIG. 6 shows the configuration of the conventional non-linear measuring device, and the measuring method will be described below. As shown in FIG. 6, the conventional non-linear constant measuring apparatus includes a light source LS1 and a light source LS2.
, An optical coupler A, an AO modulator 11, an optical fiber amplifier 12, an optical bandpass filter 21, an optical coupler B, an optical fiber 14, and an OPM 22 (OPM: Optical P
ower Meter), OPM23, OSA24 (OSA: Opt
ical Spectrum Analyzer) and PC18.

The light source LS1 generates coherent light of wavelength λ _{1 and} the light source LS2 generates coherent light of wavelength λ ₂ , and the emitted lights are combined by the optical coupler A. The AO modulator 11 directly outputs the combined light combined by the optical coupler A to the optical fiber amplifier 12. The combined light emitted from the AO modulator 11 is amplified by the optical fiber amplifier 12.

The optical band pass filter 21 removes unnecessary spontaneous emission light from the combined light amplified by the optical fiber amplifier 12, and only the light of a specific wavelength component is transmitted. The optical coupler B emits the combined light emitted from the optical bandpass filter 21 to the optical fiber 14 and the OPM 23. On the other hand, the total backscattered light reflected from the optical fiber 14 is emitted to the OPM 22.

The OPM 22 receives the total backscattered light emitted from the optical coupler B, calculates the optical power value, and outputs the calculated data to the PC 18. The OPM 23 inputs the combined light emitted from the optical coupler B, calculates the optical power value, and outputs the calculated data to the PC 18. OSA
Reference numeral 24 measures the optical spectrum of the transmitted light transmitted from the optical fiber, and outputs the measured data to the PC 18.

Next, a conventional procedure for measuring a non-linear constant will be described below with a flowchart shown in FIG. As shown in FIG. 6, with the optical fiber 14 connected to the measuring device, the non-linear constant is measured by the following procedure.

(1) Input the chromatic dispersion value, fiber parameter, etc. of the optical fiber to be measured into the PC 18 (step S
61) (2) Based on the data input in step S61,
The two light sources LS1 and LS2 having different wavelengths are driven to emit light (step S62). (3) Two lights having different wavelengths emitted in step S62 are combined, and the combined light is incident on the optical fiber 14 (step S63). (4) The optical power of the total backscattered light of the optical fiber 14 due to the combined light incident in step S63 is measured by the OPM 22 to monitor whether stimulated Brillouin scattering has occurred (step S64). (5) The optical power of the combined light incident on the optical fiber 14 in step S63 is measured by the OPM 23 (step S
65). (6) The OSA 24 measures the optical spectrum of the transmitted light of the optical fiber 14 which is the combined light incident in step S63 (step S66). (7) Based on the optical spectrum of the transmitted light measured in step S66, the ratio I ₀ / of the optical powers of the measurement light and the first sideband
I ₁ is calculated (step S67). (8) A non-linear constant is calculated from the fiber parameter and the measurement data sent to the PC 18 (step S6).
8).

Further, a method of calculating the nonlinear constant and a method of calculating the nonlinear refractive index n ₂ will be described in detail below with reference to FIG. As described above, the wavelength interval Δλ (LS2
When _two CW lights of λ ₂ −λ _{1 of} LS ₁ ) are incident on the optical fiber 14 to be measured, self-phase modulation (SPM: Self Phase Modulation) is performed at the emission end of the optical fiber 14 to be measured.
As a result, a plurality of sidebands are observed in the frequency domain (see the OSA output waveform shown in (d) of FIG. 8).

When the influence of the chromatic dispersion of the optical fiber to be measured can be ignored, the ratio I ₀ / I ₁ of the optical powers of the measurement light and the first sideband is the phase shift amount φ _{SP M} and the phase shift amount due to self-phase modulation. The relationship is as shown in Expression 1 shown in (a) of FIG. 8 using the _n- th order Bessel function J _n .

Further, the relationship between the phase shift amount φ _SPM due to self-phase modulation and the average input light intensity P is as shown in the equation 2 in FIG. 8B. Also, the effective length L _eff of the optical fiber
Is calculated by the equation 3 shown in FIG.

Using these equations 1, 2 and 3,
Power of the measuring light measured by the OSA 24 in step S66
Peak value I₀ , The peak value I of the first sideband₁And step
Input optical power P measured by OPM23 in S64, flux
Fiber parameter (effective length L _effEtc.) into the expression
Linear constant (= nonlinear refractive index n₂/ Effective core area A_eff)
Can be calculated. Furthermore, the effective core area A_effSubstituting
And nonlinear refractive index n₂Can be calculated.

[0023]

However, in the conventional technique, the measurement of the chromatic dispersion characteristic and the measurement of the nonlinear constant are performed by different independent devices. Therefore, when performing both measurements, there is a problem that the number of measuring devices increases and the cost of the devices increases. Further, since the measurement is performed by different measuring devices, there is a problem that the number of working steps in the measurement increases.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to make it possible to measure chromatic dispersion characteristics and nonlinear constants with a single optical fiber measuring device, and to improve the structure of the device. An object of the present invention is to provide an optical fiber measuring apparatus and a measuring method thereof, which can be simplified, the number of working steps in measurement can be reduced, and the cost of the apparatus can be reduced.

[0025]

An optical fiber characteristic measuring device according to the present invention, as set forth in claim 1, has a light source for continuously generating two lights having different wavelengths and two light sources for different wavelengths. A means for combining light into a combined light, an optical pulse signal obtained by shaping the combined light into a pulse shape, or an optical modulation means for emitting the combined light as it is, and unnecessary from the optical pulse signal or the combined light Means that removes natural spontaneous emission light and transmits only light of a specific wavelength component,
The optical pulse signal or the combined light is input to the optical fiber under measurement through an optical coupler, and the directional coupling means for guiding the total backscattered light from the optical fiber under measurement to the wavelength cutting means, and the total backscattering 2 of the incident light
Wavelength cutting means for transmitting only one wavelength component of the backscattered light of four-wave mixing light generated by the interaction of wavelengths, first measuring means for measuring intensity fluctuation data from the cut wavelength component, Second measuring means for measuring the optical power of the total backscattered light of the measured optical fiber, third measuring means for measuring the optical power of the combined light incident on the measured optical fiber, and the measured optical fiber Fourth measuring means for measuring the optical spectrum of the transmitted light, and a chromatic dispersion value calculated from the intensity variation data measured by the first measuring means, and the combined light measured by the third measuring means. And a calculation means for calculating a non-linear constant from the optical spectrum of the transmitted light measured by the fourth measurement means, and the optical coupler includes the directional coupling. The optical pulse signal or the combined light emitted from the means is emitted to the measured optical fiber and the second measuring means, and the total backscattered light from the measured optical fiber is directionally coupled to the third measuring means. It is characterized in that it is connected to the measuring means so as to be emitted. As a result, for the measurement of the chromatic dispersion characteristic and the measurement of the non-linear constant, it is possible to perform measurement and analysis with a shared device without separately providing a light source that generates two lights, a light modulation means, a directional coupling means, and the like. The structure of the device can be simplified, the number of working steps in measurement can be reduced, the cost of the device can be reduced, and the above object can be achieved.

Further, in the optical fiber characteristic measuring method according to the present invention, as described in claim 2, the arithmetic means is:
When measuring the chromatic dispersion characteristic, the clock signal is supplied to the optical modulator, and when measuring the non-linear constant, the fixed level signal is supplied to the optical modulator. Thereby, the measurement of the chromatic dispersion characteristic and the measurement of the non-linear constant can be switched by the calculation means (for example, PC: personal computer), and the work man-hours of the operator of the apparatus can be reduced.

Further, in the optical fiber characteristic measuring method according to the present invention, as described in claim 3, when the optical modulating means is supplied with the clock signal from the computing means, it is shaped into a pulse waveform. The optical pulse signal is emitted to the optical fiber to be measured, and when a fixed level signal is supplied from the calculating means, the combined light is directly emitted to the optical fiber to be measured. By configuring the optical modulation means in this way, an optical pulse signal for measuring the chromatic dispersion characteristic and a synthetic light for measuring the non-linear constant are automatically supplied under the control of the calculating means. You can

According to the optical fiber characteristic measuring method of the present invention, as described in claim 4, the second measuring means measures the optical power of the total backscattered light so that the stimulated Brillouin scattering occurs. It is characterized in that it can monitor whether or not it has occurred. This makes it possible to monitor whether stimulated Brillouin scattering has occurred when measuring the nonlinear constant.

The optical fiber characteristic measuring method according to the present invention is, as described in claim 5, an optical fiber characteristic measuring method for measuring a chromatic dispersion distribution characteristic and a non-linear constant. The backscattered light of the four-wave mixed light generated by the interaction of the incident two wavelengths out of the total backscattered light after shaping the combined light of the two input lights into the optical pulse signal and emitting it to the measured optical fiber. OT of one wavelength component of
A step of measuring the chromatic dispersion distribution characteristic of the optical fiber under measurement by the DR, a step of calculating a chromatic dispersion value by processing the measurement data from the OTDR, and combining two input lights having different wavelengths. The combined light is emitted to the optical fiber under measurement, and the optical power of the combined light is set to O.
Measuring with PM, measuring the optical spectrum of the transmitted light of the optical fiber with OSA, and calculating the nonlinear constant by processing the optical power, the optical spectrum, and the fiber parameter. . A light source that generates two lights by the above measuring method,
The chromatic dispersion characteristic and the non-linear constant can be measured with an optical fiber characteristic measuring device that can be shared without separately providing an optical modulator and a directional coupling means.

Further, in the optical fiber characteristic measuring method according to the present invention, as described in claim 6, in the step of measuring the chromatic dispersion distribution characteristic, the combined light obtained by synthesizing two input lights having different wavelengths, Synchronized with a clock signal supplied from a PC, shaped into an optical pulse signal, emitted to the optical fiber to be measured, and in the step of calculating the nonlinear constant, the clock signal is set to a fixed level, whereby the combined light Is directly output to the optical fiber to be measured. Thereby, the measurement of the chromatic dispersion characteristic and the measurement of the non-linear constant can be automatically switched, and the work man-hours of the operator of the apparatus can be reduced.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing a configuration of an optical fiber characteristic measuring apparatus according to the present embodiment. As shown in FIG. 1, the optical fiber characteristic measuring apparatus according to the present embodiment is provided with a light source LS1 (LS: Laser Source).
, Light source LS2 (LS: Laser Source), and optical coupler A
, AO modulator 11, optical fiber amplifier 12, and optical band pass filter 21 (OBPF: Optical Band Pass Filter).
er), a directional coupler 13, an optical fiber 14, and an optical band pass filter 16 (OBPF: Optical Band Pass Filt).
er) and the first measuring means OTDR17 (OTDR: 0p
tical Time Domain Reflectometer) and PC18 (P
C: Personal Computer), optical coupler B, and second measurement means OPM22 (OPM: Optical Power Meter)
And OPM23 which is the third measuring means and OSA24 (OSA: Optical Spectrum Analyze) which is the fourth measuring means.
r) and.

In FIG. 1, the wavelength λ ₁ is emitted from the light source LS1.
Of the coherent light of the wavelength λ ₁ from the light source LS2.
Coherent light is generated, and the emitted lights are combined by the optical coupler A. The AO modulator 11 synchronizes the combined light combined by the optical coupler A with the clock of the synchronization signal supplied from the PC 18 to form a pulse-shaped optical pulse signal, or outputs the combined light as it is to the optical fiber. The light is emitted to the amplifier 12. The optical pulse signal or the combined light emitted from the AO modulator 11 is amplified by the optical fiber amplifier 12.

The optical pulse signal or the combined light amplified by the optical fiber amplifier 12 is passed through the optical bandpass filter 2
Unwanted spontaneous emission light is removed by 1, and only light having a specific wavelength component is transmitted. The light amplified by the optical fiber amplifier 12 is emitted by the directional coupler 13 through the optical coupler B to the optical fiber 14 which is the measurement target.

The directional coupler 13 is composed of the optical fiber 1
The total backscattered light generated by the light incident on the light beam No. 4 is branched, only a specific wavelength is transmitted through the optical bandpass filter 16, and is given to the OTDR 17.

In the optical bandpass filter 16, of the total backscattered light due to the optical pulse signal input to the optical fiber to be measured, one of the backscattered light of the four-wave mixed light generated by the interaction of the incident two wavelengths is used. The wavelength component of is cut out.

In the OTDR 17, the optical bandpass filter 16 transmits only the light of one wavelength component of the backscattered light of the four-wave mixed light generated by the interaction of the two incident wavelengths of the total backscattered light. Based on, the data indicating the intensity fluctuation data of the total backscattered light of the optical fiber 14 as the measurement target is calculated. The intensity fluctuation data of the total backscattered light calculated by the OTDR 17 is accumulated in the RAM in the PC 18 and used for various calculations.

The optical coupler B converts the optical pulse signal or the combined light emitted from the directional coupler 13 into the optical fiber 14
And OPM23. On the other hand, the total backscattered light reflected from the optical fiber 14 is transmitted to the directional coupler 13 and the OPM 2
Emit to 2 and.

The OPM 22 receives the total backscattered light emitted from the optical coupler B, calculates the optical power value, and outputs the calculated data to the PC 18. The OPM 23 inputs the combined light emitted from the optical coupler B, calculates the optical power value, and outputs the calculated data to the PC 18. OSA
Reference numeral 24 measures the optical spectrum of the transmitted light transmitted from the optical fiber, and outputs the measured data to the PC 18.

The PC 18 has OTDRs 17, OPMs 22,
A RAM for temporarily storing each data output from the OPM 23 and the OSA 24 is provided, and the chromatic dispersion distribution and the nonlinear constant are calculated using the data stored in the RAM.

Next, a flow chart of the method for measuring the optical fiber characteristics according to the present embodiment is shown in FIG. 2 and will be described with reference to FIG. As shown in FIG. 1, with the optical fiber 14 connected to the measuring device, the chromatic dispersion distribution characteristic is measured by the following procedure.

(1) Input the fiber parameters of the optical fiber to be measured into the PC 18 (step S1) (2) The chromatic dispersion distribution characteristic is measured as follows (step S2). Two light sources LS1 and L with different wavelengths
Measurement conditions such as S2, OTDR 17, optical fiber amplifier 12 are set, and a clock signal is supplied from the PC 18 to the AO modulator 11. As a result, the light emitted from the AO modulator 11 is shaped into a pulse and becomes an optical pulse signal.
The OTDR 17 receives the specific wavelength light that has transmitted only one wavelength component of the backscattered light of the four-wave mixed light generated by the interaction of the two incident wavelengths of the total backscattered light from the measured optical fiber 14. , Calculate the data. (3) The PC 18 processes the measurement data from the OTDR 17 to calculate the chromatic dispersion value (step S
3). (4) The setting of the AO modulator 11 is changed by the PC 18. At this time, the clock signal supplied from the PC 18 is set to "H".
Fixed to level. As a result, the light emitted from the AO modulator 11 becomes combined light. (Step S4) (5) Nonlinear constant measurement is performed as follows (step S5). Based on the data input from the PC 18, the two light sources LS1 and LS2 having different wavelengths are driven to emit light. Two lights having different wavelengths are combined and the combined light is made incident on the optical fiber 14. The optical power of the total backscattered light of the optical fiber 14 is measured by the OPM 22 to monitor whether stimulated Brillouin scattering has occurred. The optical power of the combined light incident on the optical fiber 14 is measured by the OPM 23. O of the optical spectrum of the transmitted light of the optical fiber 14
Measured by SA24. (6) Based on the optical spectrum measured in step 5, the ratio I ₀ / I ₁ of the optical powers of the measurement light and the first sideband is calculated,
A nonlinear constant is calculated from this I ₀ / I ₁ , the optical power measured by the OPM 23, and the fiber parameter (step S6).

FIG. 3 shows the output waveform of one measurement example obtained by the above-described procedure. In FIG. 3, (a) is a waveform (optical spectrum) before entering the measured optical fiber 14,
(B) is an output waveform (optical spectrum) of the OSA 24. When the waveforms of the light sources LS1 and LS2 incident on the optical fiber 14 shown in FIG. 3A are emitted from the emission end of the optical fiber 14, as shown in FIG. 3B, self-phase modulation (SPM: Self Due to the effect of (Phase Modulation), a plurality of sidebands are observed in the frequency domain, and the values of the peak I ₀ of the optical power of the measurement light by the light source LS1 and the peak I ₁ of the optical power of the first sideband thereof can be obtained. .

Further, the measured input optical power P, fiber parameters (effective length L _eff , effective core cross-sectional area A)
_eff, etc.) and the like measured wavelength dispersion values of the above equation 1 in FIG. 8 described above, the formula 2, nonlinear refractive index n ₂ using Equation 3
Can be asked.

[0044]

As described above in detail, according to the present invention,
As described in claim 1, for the measurement of the chromatic dispersion characteristic and the measurement of the non-linear constant, a shared device is used without separately providing a light source that generates two lights, a light modulation means, a directional coupling means, and the like. Since measurement and analysis can be performed, the structure of the device can be simplified, the number of working steps in the measurement can be reduced, and the cost of the device can be reduced.

According to the present invention, as described in claim 2, the calculating means supplies the clock signal to the optical modulating means when measuring the chromatic dispersion characteristic, and fixed when measuring the nonlinear constant. Since the level signal is supplied to the optical modulation means, the measurement of the chromatic dispersion characteristic and the measurement of the non-linear constant can be switched by the calculation means (for example, PC: personal computer), and the work man-hours of the operator of the apparatus can be changed. It is possible to provide an optical fiber characteristic measuring device capable of reducing

Further, according to the present invention, as described in claim 3, when the optical modulating means is supplied with the clock signal from the calculating means, the optical modulating means converts the optical pulse signal shaped into a pulse waveform into the measured light. When the signal is output to the fiber and the fixed level signal is supplied from the calculation means, the combined light is directly output to the optical fiber to be measured. Therefore, the calculation means automatically controls the measurement of the chromatic dispersion characteristics. It is possible to provide an optical fiber characteristic measuring apparatus that can be configured to supply synthetic light to an optical pulse signal for measuring a nonlinear constant.

Further, according to the present invention, as described in claim 4, the second measuring means monitors whether or not stimulated Brillouin scattering has occurred by measuring the optical power of the total backscattered light. It is possible to provide an optical fiber characteristic measuring device configured as possible.

Further, according to the present invention, as described in claim 5, the combined light obtained by combining two input lights having different wavelengths,
One wavelength component of the backscattered light of the four-wave mixed light generated by the interaction of the incident two wavelengths out of the total backscattered light after being shaped into an optical pulse signal and emitted to the optical fiber under measurement is O
Detecting with TDR, measuring the chromatic dispersion distribution characteristic of the optical fiber under test, and calculating the chromatic dispersion value by processing the measurement data from the OTDR,
The combined light obtained by combining the two input lights having different wavelengths is emitted to the optical fiber under measurement, the optical power of the combined light is measured by the OPM, and the optical spectrum of the transmitted light of the optical fiber is measured by the OSA.
And a step of calculating a non-linear constant by processing the optical power, the optical spectrum, and the fiber parameter, the light source for generating two lights, the optical modulation means, the directional coupling means, etc. It is possible to measure the chromatic dispersion characteristic and the non-linear constant with an optical fiber characteristic measuring device which can be shared without being provided in the optical fiber.

Further, according to the present invention, as described in claim 6, in the step of measuring the chromatic dispersion distribution characteristic, the combined light obtained by combining the two input lights having different wavelengths is
Synchronized with the clock signal supplied from the device, shaped into an optical pulse signal, emitted to the optical fiber under test, and in the step of calculating the nonlinear constant, the clock signal is set to a fixed level, so that the combined light is directly measured. By emitting to the fiber, it is possible to automatically switch between measurement of chromatic dispersion characteristics and measurement of nonlinear constants.
The work man-hours of the operator of the apparatus can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical fiber characteristic measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart of an optical fiber characteristic measuring method according to an embodiment of the present invention.

FIG. 3 is an output waveform of one measurement example obtained by the optical fiber characteristic measuring method according to the embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional wavelength dispersion distribution measuring apparatus.

FIG. 5 is a flowchart showing a conventional procedure for measuring chromatic dispersion distribution characteristics.

FIG. 6 is a diagram showing a configuration of a conventional non-linear measurement device.

FIG. 7 is a flowchart showing a conventional non-linear constant measurement procedure.

FIG. 8 is a diagram of a non-linear constant calculation formula and an OSA output waveform.

[Explanation of symbols]

11 AO modulator 12 Optical fiber amplifier 13 Directional coupler 14 optical fiber 15 Terminator 16,21 Optical bandpass filter 17 OTDR 18 PC 22,23 OPM 24 OSA A, B optical coupler LS1, LS2 light source

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Emiko Fujiwara             529-3 Kamata, Ota-ku, Tokyo Andoden             Ki Co., Ltd. (72) Inventor Takao Suzuki             529-3 Kamata, Ota-ku, Tokyo Andoden             Ki Co., Ltd.

Claims (6)

[Claims] 1. A light source for continuously generating two lights having different wavelengths, a means for combining the two lights having different wavelengths to form a combined light, and an optical pulse signal obtained by shaping the combined light into a pulse shape. Alternatively, an optical modulator that emits the combined light as it is, a means that removes unnecessary spontaneous emission light from the optical pulse signal or the combined light, and transmits only light of a specific wavelength component, the optical pulse signal or While inputting the combined light into the optical fiber to be measured through an optical coupler, a directional coupling means for guiding all the backscattered light from the optical fiber to be measured to a wavelength cut-out means, and of all the backscattered light, the incident light Wavelength cut-out means for transmitting only one wavelength component of the backscattered light of the four-wave mixed light generated by the interaction of the two wavelengths, and the intensity variation data from the cut-out wavelength component. A first measuring means for measuring the optical power, a second measuring means for measuring the optical power of the total backscattered light of the optical fiber to be measured, and an optical power of the combined light incident on the optical fiber to be measured. Third measuring means, fourth measuring means for measuring the optical spectrum of the transmitted light of the optical fiber to be measured, chromatic dispersion value is calculated from the intensity fluctuation data measured by the first measuring means, and The optical power of the combined light measured by the third measuring means, and the calculating means for calculating a nonlinear constant from the optical spectrum of the transmitted light measured by the fourth measuring means, The coupler outputs the optical pulse signal or the combined light emitted from the directional coupling means to the optical fiber under measurement and the second measuring means, and all backscattered light from the optical fiber under measurement is emitted. Apparatus for measuring optical fiber characteristics, wherein connected it to emit to the tropism coupling means and the third measuring means. 2. The optical fiber characteristic measuring device according to claim 1, wherein the arithmetic means supplies the clock signal to the optical modulating means to measure a nonlinear constant when measuring the chromatic dispersion characteristic. In this case, the optical fiber characteristic measuring device is characterized in that the fixed level signal is supplied to the optical modulator. 3. The optical fiber characteristic measuring device according to claim 2, wherein, when the optical modulation means is supplied with a clock signal from the arithmetic means, the optical pulse signal shaped into a pulse waveform. Is emitted to the optical fiber to be measured, and when a fixed level signal is supplied from the calculating means, the combined light is directly emitted to the optical fiber to be measured. 4. The optical fiber characteristic measuring device according to claim 1, wherein the second measuring means measures the optical power of the total backscattered light, whereby the stimulated Brillouin scattering occurs. An optical fiber characteristic measuring device characterized in that it can monitor whether or not it has occurred. 5. An optical fiber characteristic measuring method for measuring a chromatic dispersion distribution characteristic and a non-linear constant, wherein the combined light obtained by combining two input lights having different wavelengths is shaped into an optical pulse signal, and the optical fiber to be measured. Out of the total backscattered light, one wavelength component of the backscattered light of the four-wave mixing light generated by the interaction of the incident two wavelengths is detected by the OTDR, and the chromatic dispersion distribution of the measured optical fiber is detected. Measuring the characteristics, calculating the chromatic dispersion value by processing the measurement data from the OTDR, and combining light that is obtained by combining two input lights having different wavelengths to the measured optical fiber, The optical power of the combined light is measured by OPM, and the optical spectrum of the transmitted light of the optical fiber is
And a step of calculating the nonlinear constant by processing the optical power, the optical spectrum, and the fiber parameter. 6. The optical fiber characteristic measuring method according to claim 5, wherein in the step of measuring the chromatic dispersion distribution characteristic, combined light obtained by combining two input lights having different wavelengths is supplied from a PC. Synchronized by a clock signal, shaped into an optical pulse signal, emitted to the optical fiber under measurement, and in the step of calculating the nonlinear constant, by setting the clock signal at a fixed level, the combined light is directly measured under the condition. A method for measuring an optical fiber characteristic, which is characterized in that the optical fiber is emitted to an optical fiber.