WO2002046715A1 - Procede et equipement de mesure de dispersion de longueur d'onde - Google Patents

Procede et equipement de mesure de dispersion de longueur d'onde Download PDF

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Publication number
WO2002046715A1
WO2002046715A1 PCT/JP2001/010185 JP0110185W WO0246715A1 WO 2002046715 A1 WO2002046715 A1 WO 2002046715A1 JP 0110185 W JP0110185 W JP 0110185W WO 0246715 A1 WO0246715 A1 WO 0246715A1
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Prior art keywords
light
dispersion
signal
intensity
modulated
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PCT/JP2001/010185
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English (en)
Japanese (ja)
Inventor
Yuichi Takushima
Kazuro Kikuchi
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Center For Advanced Science And Technology Incubation, Ltd.
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Priority to AU2002224067A priority Critical patent/AU2002224067A1/en
Priority to JP2002548405A priority patent/JPWO2002046715A1/ja
Publication of WO2002046715A1 publication Critical patent/WO2002046715A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
    • G01M11/33—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face
    • G01M11/333—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face using modulated input signals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
    • G01M11/33—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face
    • G01M11/335—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face using two or more input wavelengths
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
    • G01M11/33—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face
    • G01M11/338—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter being disposed at one fibre or waveguide end-face, and a light receiver at the other end-face by measuring dispersion other than PMD, e.g. chromatic dispersion

Definitions

  • the present invention relates to chromatic dispersion measurement of an optical element such as an optical fiber.
  • Group velocity dispersion (called chromatic dispersion or simply dispersion) is a phenomenon in which the speed at which light travels depends on the frequency (wavelength).
  • chromatic dispersion When an optical pulse propagates through an optical element having chromatic dispersion, the speed is different for each optical frequency component constituting the optical pulse, so that the waveform is distorted as the optical pulse propagates, and the pulse width is increased.
  • waveform distortion and pulse width broadening due to dispersion limit the transmission rate, so the technology for accurately evaluating dispersion is very important in designing and constructing optical communication systems.
  • the measurement wavelength is sequentially changed, and the group velocity dispersion is obtained from the phase difference of the intensity modulation component when the wavelength is changed.
  • the phase comparator outputs only a value between 0 and 2 ⁇ even if a phase change of 2 ⁇ or more occurs.
  • the modulation frequency is reduced in accordance with the dispersion of the fiber, the phase change is reduced, and the accuracy is reduced.
  • the light at the wavelength to be measured must be injected from the outside, so the service at the measured wavelength must be stopped. This is a practical problem.
  • most of the conventional methods cannot be used because the input / output terminals (transmitter and receiver) to be measured are located far apart.
  • the wavelength of the light source is swept near the measurement wavelength and numerical processing (wavelength Variance can be obtained by differentiating with. Therefore, to measure the polarization dependence, fix the input light to a certain polarization state, sweep the wavelength, measure the dispersion, and repeat this procedure to obtain the maximum and minimum dispersion values. Find out. Therefore, it takes time because the wavelength sweep must be repeated, and there is no guarantee that the maximum and minimum values will be found in a finite number of procedures if the polarization state in the fiber changes during measurement.
  • Another object of the present invention is to easily and satisfactorily measure the polarization dependence of group velocity dispersion. Disclosure of the invention
  • the technical means adopted by the present invention is that the optical frequency modulation and the intensity modulation obtained by performing the optical frequency modulation and the intensity modulation are injected into the optical element to be measured, and the intensity modulation caused by the group velocity dispersion is performed. It is characterized by measuring a phase modulation component of the component.
  • optical frequency modulation and intensity modulation are simultaneously performed on a light source, and a phase modulation component of an intensity modulation component caused by group velocity dispersion is measured.
  • Phase delay due to disturbance ⁇ Fluctuation of group delay time is separated on the frequency axis, so it is not affected by disturbance.
  • the light source according to the present invention is a wavelength tunable light source such that the wavelength (frequency) can be continuously swept (for example, in the range of several GHz).
  • a light source itself is known, and a so-called mode-hop-free wavelength variable light source is exemplified.
  • an external mirror type wavelength tunable light source and an external resonator type wavelength tunable light source are exemplified, and these light sources themselves include, for example, a semiconductor laser, a laser diode, a DBR laser, and a DFB laser.
  • Many tunable light sources of this kind already exist as products, and there are many patents. For example, Japanese Unexamined Patent Publication No. 7-23927 (US Pat. No.
  • the modulation waveform of the modulation signal for obtaining the optical frequency modulated light is, in one preferred embodiment, an asymmetric waveform.
  • An asymmetric waveform means a waveform whose shape changes when the sign is reversed.
  • An example of an asymmetric waveform is an asymmetric triangular wave or an asymmetric square wave.
  • the modulation waveform of the modulation signal is not limited to an asymmetric waveform, and in another preferred embodiment, the modulation signal is a sine wave.
  • the modulation wave for optical frequency modulation is a sine wave signal
  • the sign of the variance value can be reproduced by performing a kick-in detection using the sine wave signal.
  • the signal that modulates the intensity of the light whose optical frequency has been modulated is a sine wave signal in one preferred embodiment.
  • intensity modulation can be performed using a digital data signal (binary random code) instead of the sine wave signal.
  • light modulated with a digital data signal can be used as the probe light, so there is almost no change to the existing transmission system, the transmission signal is used as it is, and the transmission path is used in real time without service interruption. Can be measured.
  • the means for measuring the phase modulation component can be suitably selected from known demodulation or detection means.
  • a detection method using a phase locked loop (PLL) is advantageous.
  • PLL phase locked loop
  • the polarization dependence of group velocity dispersion which is one component of higher-order polarization dispersion, can be measured.
  • a polarization controller is provided in front of the entrance of the measurement object, dispersion is specified while changing the polarization state of the injected signal light, and the maximum and minimum values of the dispersion are recorded. The difference between the maximum value and the minimum value indicates the polarization dependence of the group velocity dispersion.
  • FIG. 1 is a schematic configuration diagram showing a chromatic dispersion measuring apparatus according to a first embodiment of the present invention
  • FIG. 2 shows a time change of an optical frequency and intensity of light (optical frequency modulation, intensity modulated light) to be used.
  • A shows the optical frequency (upper figure) and intensity (lower figure) before being injected into the measurement target
  • (b) shows the light intensity after exiting the measurement target
  • FIG. 3 shows the light intensity.
  • FIG. 4 is a diagram for explaining the concept of the frequency modulation method.
  • FIG. 4 is a configuration diagram showing code reproduction by mouth lock-in detection.
  • FIG. 5 is a diagram showing a spectrum of a feedback signal voltage to a VCO measured at a wavelength of 150 nm.
  • FIG. 6 is a diagram plotting the magnitude of the 320 Hz Z component while changing the wavelength
  • Fig. 7 is a diagram illustrating the case where various fibers are measured at different wavelengths.
  • FIG. 8 is a diagram comparing the conventional phase shift method with the present invention
  • FIG. 10 is a diagram illustrating the principle of the system according to the embodiment.
  • FIG. 10 is a diagram illustrating application to the system.
  • (A) illustrates in-service monitoring of GVD of a transmission link
  • (b) illustrates feed pack control.
  • FIG. 11 (c) shows adaptive dispersion compensation using the bridge forward control
  • FIG. 11 is a diagram showing the spectrum of the measured feedback signal voltage V
  • FIG. 11 is a diagram showing the spectrum of the measured feedback signal voltage V
  • Fig. 13 shows the optical frequency modulation waveform, the phase of the intensity modulation component of the output light from the fiber under measurement, and the VCO output waveform.
  • Fig. 14 shows the modulation waveform used in the experiment, and
  • Fig. 15 shows the dispersion measurement including code recovery.
  • the horizontal axis shows the dispersion value obtained by the phase shift method.
  • the vertical axis is the indicated value by this measurement method, and the optical signal-to-noise ratio is 10, 15
  • Figure 16 shows the dispersion measurement when the modulation waveform was a square wave (in the case of Fig. 13 (c)), and Fig. 17 shows the proposed higher order Polarization dispersion Fig.
  • FIG. 18 is a diagram of the measurement system (polarization dependence of chromatic dispersion).
  • Fig. 18 measures the maximum and minimum values of dispersion when the measurement wavelength is fixed, and determines the higher-order polarization dispersion ( This is a diagram for explaining how to obtain the polarization dependence of chromatic dispersion).
  • the polarization state on the horizontal axis is actually represented by two parameters, and
  • Fig. 19 shows the polarization dependence of chromatic dispersion by the phase shift method.
  • FIG. 4 is a diagram showing a case where the property is measured.
  • FIG. 1 is a conceptual diagram of a measurement system according to the present invention.
  • the measurement system consists of a tunable CW light source (continuous wave light source), a first frequency ( ⁇ ) signal source, a light intensity modulator, a second frequency ( ⁇ signal source, a measurement target, a photodetector, A PLL detector.
  • a CW light source that can change the optical frequency is prepared as a light source, and the optical frequency is modulated at the frequency f [Hz].
  • the instantaneous angular frequency is expressed as follows. However, ⁇ . Is the center frequency of the CW light source, ⁇ is the width of the frequency change, and t is the time.
  • the intensity of the optical frequency modulated light is modulated at another frequency f, [H z].
  • the light intensity P i is expressed as follows. However, f '>> f. However, ⁇ . Is the average optical power.
  • Fig. 2 (a) shows a schematic representation of the time variation of the frequency and intensity of the light input to the measurement target.
  • the upper diagram in Fig. 2 (a) shows the change in the optical frequency of the light frequency-modulated at the frequency f.
  • the lower diagram in FIG. 2 (a) shows the change in the light intensity of the light intensity-modulated at the frequency ⁇ ′.
  • the light whose optical frequency and intensity are modulated in this way is referred to as optical frequency modulation / intensity modulated light.
  • this optical frequency modulation / intensity modulation light is injected into an optical element to be measured. like this As a result, the phase of the intensity modulation component changes in accordance with the dispersion of the optical element, and the group velocity dispersion is determined from that.
  • FIG. 3 is a schematic diagram of the group velocity dispersion measurement according to the present invention, in which the horizontal axis represents wavelength and the vertical axis represents group velocity dispersion.
  • the wavelength of the light source which is the measurement wavelength
  • L1 the optical frequency of the light source is swept in a sinusoidal shape within a range of several GHz around the wavelength 1 (frequency f1). Is obtained.
  • ⁇ 2 the optical frequency near that wavelength
  • the light frequency of the light source is swept in a sinusoidal manner, but the waveform is not limited as long as the frequency can be changed continuously.
  • optical fiber will be described as an example of an object to be measured.
  • the optical fiber is merely one preferable example, and the present invention does not particularly select an object to be measured.
  • phase modulation component ⁇ (t) is composed of several frequency components whose fundamental harmonic is the modulation frequency ⁇ of the optical frequency modulation.
  • the frequency components are as follows.
  • the DC component, f component, and 2 f component are quantities proportional to group delay, group velocity dispersion, and third-order dispersion, respectively. Therefore, the group velocity dispersion can be measured by measuring the frequency ⁇ component.
  • the group delay, third-order variance, fourth-order variance, and (11 + 1) -order variance can be measured by measuring the DC component, the 2f component, the 3f component, and the nf component.
  • the means for measuring the f component can be appropriately selected from known spectrum detection methods, and preferred examples of the detection means include a method using synchronous detection and a method using a spectrum analyzer. When lock-in detection is used, as shown in Fig. 4, the code of the dispersion can be reproduced.
  • To measure the DC component all the common demodulation and detection methods can be used as long as phase detection can be performed, and other network analyzers can also be used.
  • phase-group delay time As a function of wavelength (omega) is a normal phase method
  • the method according to the present invention does not require information on the DC component of the phase modulation component, but needs to measure the absolute amount of the phase modulation component. For this reason, a detection method using a phase locked loop (PLL) is effective. .
  • PLL phase locked loop
  • the part after the photodetector in FIG. 1 is a normal phase lock loop circuit. If the frequency modulation sensitivity of the voltage controlled oscillator (VCO) is a [H z / V], the following relationship exists between the feedback signal voltage V input to the VCO when the phase is locked and the phase modulation component. Holds.
  • VCO voltage controlled oscillator
  • the feedback signal voltage V is not affected by the conversion efficiency and feedback gain of the photodetector. Therefore, the group velocity dispersion ⁇ 2 L can be measured by measuring the feedback signal voltage V.
  • the principle of verification was performed by actually configuring the measurement system shown in Fig. 1.
  • a dispersion-shifted fiber having a zero-dispersion wavelength of 15.53.5 nm and a length of 10 km was used.
  • the output light from the object to be measured is converted into an electric signal by a photodetector and sent to a 2 GHz PLL circuit.
  • the phase modulation component was detected by input.
  • the magnitude (absolute value) of the feedback signal voltage was measured by a digital spectrum analyzer without synchronous detection in order to measure the dynamic range.
  • Figure 5 shows the spectrum of the feedback signal voltage measured at a wavelength of 1500 nm.
  • the frequency resolution of the digital spectrum analyzer is 1.25 Hz.
  • the magnitude of the 320 Hz component corresponds to the group velocity variance, and in FIG. Wherein the group velocity dispersion amount / 3 2 calculated using the (9) is 44.
  • the noise level at 320 Hz is 110 dBBV, and a dynamic range of about 30 dB is obtained.
  • the frequency resolution is limited by the amplitude ⁇ of the optical frequency modulation, but it becomes less than 0.1 nm when converted to wavelength.
  • the dispersion measurement accuracy is about 1 ps Znm, but it can be seen that the accuracy is very high considering the frequency resolution. (Similar frequency resolution and accuracy are achieved using the phase shift method.) If this is attempted, it is necessary to measure a group delay time of 10 fs or less.) Even in this experimental system, if the observation time is extended by using synchronous detection, it is possible to further improve by 10 dB or more, and an accuracy of about 0.1 ps / nm can be realized without difficulty. Further, by optimizing the PLL circuit and the modulation frequencies f, f ′, etc., the accuracy limit is considered to be less than 0.01 ps Znm.
  • the effect of drift due to disturbances is seen in the low frequency range below 10 Hz, but the effect is on the order of 1 1, and does not affect the measurement of group velocity dispersion. In other words, the effect of drift due to disturbance is separated on the frequency axis.
  • FIG. 6 is a graph plotting the magnitude of the 320 component with the wavelength changed.
  • the zero-dispersion wavelength of this optical fiber is around 1553.5 nm. Since the measurement method according to the present invention has a wide dynamic range, a very clear zero-dispersion wavelength can be seen. In addition, accuracy is maintained near zero dispersion.
  • the code can be reproduced if the phase modulation component is detected by mouth-in.
  • Figure 7 shows various fibers This is the result of measuring the wavelength dependence. It can be seen that a very high dynamic range has been obtained.
  • FIG. 8 (A) is a diagram showing the phase shift method.
  • the measured wavelength is sequentially changed, and the group velocity dispersion is obtained from the phase difference of the intensity modulation component when the wavelength is changed.
  • a reference is required to accurately measure the phase difference. If the phase at the wavelength L 1 (strictly speaking, the difference from the reference phase) is 0 1 and the phase at the wavelength 2 is 0 2,
  • Fig. 8 (B) shows this method.
  • the feature is that the measurement wavelength is swept continuously, and the phase change becomes continuous. Therefore, phase tracking can be performed using the PLL.
  • this method even if a phase change of 2 ⁇ or more occurs due to a change in the measurement wavelength, an output voltage proportional to the phase change can be obtained as long as the PL tracks the phase. Therefore, there is essentially no phase uncertainty of 2 ⁇ in this method.
  • it is not necessary to adopt a complicated configuration that can cope with the phase uncertainty of 2 ⁇ , and there is no need to lower the modulation frequency, so that a wide dynamic range can be obtained without lowering the measurement accuracy.
  • no reference phase is required. Therefore, dispersion measurement is possible only with the output.
  • the second embodiment relates to a system and a method for measuring a variance value using a normal digital data signal.
  • Figure 9 shows the principle of the system.
  • Measurement system includes a tunable laser light source (LD), a first frequency (f F) signal source, and the light intensity modulator, a second frequency (B) signal source, a measuring object, a photodetector, a clock It has an extraction unit and a PLL detection unit.
  • LD tunable laser light source
  • f F first frequency
  • B second frequency
  • the transmitter side performs the optical frequency modulated at a frequency f F, modulated with digital data signal of a frequency B to be sent thereafter.
  • the receiving side extracts the clock signal of a frequency B from the modulation signal, detecting a phase modulation component of the frequency I F superimposed on a clock signal using a PLL circuit. Since the clock component of the transmission signal has the same role as the sine wave intensity modulation component of the first embodiment, the group velocity dispersion can be obtained from the phase modulation component of the click component.
  • the relationship between the detected voltage V and the group velocity variance is expressed by replacing f 'with B in Eq. (9).
  • the optical transmission system perform optical frequency modulation to the optical transmitter (TX) adds a frequency signal source frequency f F, the optical frequency from the optical transmitter (TX)
  • the group velocity dispersion value of each of the transmission lines A and B can be obtained by transmitting the modulated light and adding a PLL exemplified as a suitable detection means to the optical receiver (RX).
  • adaptive dispersion equalization by feed-pack control can be performed with high precision in combination with variable dispersion (Fig. 10 (b)).
  • adaptive variance equalization by feedforward control is also possible (Fig. 10 (c)).
  • the CW light that has been optically frequency-modulated at a frequency of 400 Hz is modulated by a pseudorandom code with a bit rate of 9.953 Git / s and a length of 2 31 — 1 generated from a pulse pattern generator.
  • the amplitude 2 ⁇ of the optical frequency modulation is 2 GHz.
  • the transmission line is a 25 km long dispersion-shifted fiber.
  • 9.95 3 GHz from the signal It removed the clock component detected the phase modulation Ingredient in PLL circuit after conversion to 5 0 OMH Z.
  • V CO frequency modulation sensitivity was 0. 5 k H z / V.
  • Fig. 11 shows the spectrum of the feedback signal voltage V to VCO when the signal wavelength is 1550 nm. 4 0 0 size of components of the H z is an 3 1. .6 d BV (peak value 3. 7 2 X 1 0 one 2 V), the dispersion value to be determined from the equation (9) is as follows is there.
  • the cut-off frequency of the loop filter of the PLL circuit used is 2 kHz, and it has a flat noise characteristic within the feedback band of PLL. This noise level roughly corresponds to the dispersion amount of lps / nm / km, and was generated by the clock extraction circuit. Since the noise level of the PLL circuit alone is about 20 dB lower than this, the resolution of 0.1 ps ZnmZkni can be achieved with improvement.
  • FIG. 12 shows the dispersion value obtained when the wavelength of the transmission signal is changed. In this measurement system, only the absolute value of the feedback signal voltage is measured, so only the absolute value of the variance is required.
  • dispersion measurement using optical frequency modulation and intensity modulation light and dispersion in-service monitoring using signal light modulated with digital data are described.Dispersion measurement is performed using only the output signal from the fiber. It was shown that the value was obtained and that the variance value could be measured with high accuracy.
  • (a) shows a case where frequency modulation is performed with a sine wave.
  • the leftmost is the optical frequency modulation waveform, with the dispersion value on the normal side (ops / mn / km) on the left, and the variance value on the abnormal side, O Ops / nm / km) on the right.
  • the phase modulation component ⁇ of the intensity modulation component is proportional to the modulation waveform, and the output from VC0 after demodulation by the PLL is the time derivative of the phase modulation component ⁇ .
  • the phase of the output signal from VC0 differs by 180 degrees depending on the sign of the variance, it cannot be determined whether the output signal is normal or abnormal because there is no reference phase with the output signal alone. Therefore, it was necessary to perform lock-in detection based on the modulation waveform on the transmitting side (Fig. 4).
  • Figs. 13 (b) and 13 (c) an asymmetric triangular wave is considered as shown in the figure, but any waveform that changes its shape when the sign is reversed is applicable.
  • the phase modulation component ⁇ of the intensity modulation component is proportional to the modulation waveform, but since the sign of the variance reverses the sign, the waveform differs depending on whether the measurement target is normal dispersion or abnormal dispersion. Therefore, it is possible to determine whether the variance is positive or negative from the waveform.
  • the dispersion value can be obtained by measuring the amplitude, and the magnitude of the modulation frequency component may be measured from the spectrum.
  • the output voltage from VC0 is a time derivative of ⁇ , which results in a square wave pulse as shown in the figure, and its duty ratio (the ratio of the high level when considered as a binary pulse) is positive or negative. Different. Therefore, from VC0 By measuring the duty ratio of the output signal, the sign can be easily determined. Even if the modulation waveform is other than an asymmetric triangular wave, it can be applied if the waveform is vertically asymmetric.
  • (c) shows the case where a square wave with a duty ratio of 50% or less is used as the modulation waveform.
  • the output pulse train of VC0 and the like becomes an impulse train, and it is possible to determine whether the variance is positive or negative based on the difference between the arrival times of the positive and negative impulses.
  • the modulation waveform is an asymmetric triangular wave as shown in Fig. 14, with a repetition frequency of 10kHz and a duty ratio of 75%.
  • the optical frequency modulated light is modulated by a digital random signal with a bit rate of 9.953 Gbit / s and injected into the fiber to be measured.
  • the receiving side reproduces the 9.953 GHz clock signal and injects it into the PLL circuit.
  • Figure 15 shows the measurement results.
  • the horizontal axis shows the dispersion value of the fiber measured by the phase shift method
  • the vertical axis shows the measuring instrument reading (measurement voltage) measured by this method.
  • Positive and negative are correctly discriminated, and it is clear that the variance value and the indicated value of the measuring instrument are in a proportional relationship.
  • the effect of optical noise is a concern because the code is reproduced using the waveform. Showed little change and was very resistant to optical noise.
  • the measurement was also performed with a square wave as shown in Fig. 13 (c). The results are shown in FIG. Also in this case, code reproduction and dispersion value measurement can be performed without any problem.
  • FIG 17 shows the configuration diagram.
  • the measurement system consists of a CW light source, a first frequency (f) signal source, an optical intensity modulator, a second frequency (f signal source, a polarization controller, a measurement object, a photodetector, and a PLL detector.
  • a polarization controller is substantially the same as the measurement system shown in Fig. 1 except that the polarization controller has a polarization controller. Controlled via AZD conversion and control computer
  • a polarization controller is an element that controls the polarization state of an optical signal propagating through an optical waveguide such as an optical fiber.
  • polarization scrambler fiber squeezer-type polarization control element (fiber pressurizer)
  • rotating fiber examples include a coil, a rotating phase plate, and a Faraday rotator.
  • a polarization controller is attached to the entrance of the measurement pair, and dispersion measurement is performed by changing the polarization state of the injection signal light by the polarization controller. Record the value. The difference between the maximum value and the minimum value indicates the polarization dependence of the group velocity dispersion.
  • the measurement procedure when using the phase shift method is described with reference to FIG.
  • dispersion is obtained by sweeping the wavelength of the light source around the measurement wavelength and performing numerical processing (differentiation by wavelength). Therefore, in order to measure the polarization dependence, the input light is fixed to a certain polarization state, then the wavelength is swept and the dispersion is measured. The maximum and minimum variances are found by repeating the above procedure and measuring while changing the input polarization state. As mentioned above, the disadvantage is that it takes time because the wavelength sweep must be repeated, and there is no guarantee that the maximum and minimum values will be found in a finite number of procedures if the polarization state in the fiber changes during measurement. is there. Industrial applicability
  • the present invention is used for measuring chromatic dispersion in the field of optical communication. Further, the present invention is used for in-service monitoring of chromatic dispersion, adaptive dispersion equalization, and higher-order polarization dispersion measurement.

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  • Chemical & Material Sciences (AREA)
  • Optics & Photonics (AREA)
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  • General Physics & Mathematics (AREA)
  • Dispersion Chemistry (AREA)
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Abstract

L'invention concerne un procédé de mesure de dispersion de longueur d'onde destiné à mesurer directement la dispersion de vitesse de groupe d'un élément optique, par exemple une fibre optique. On mesure la dispersion de vitesse de groupe en utilisant un rayonnement lumineux soumis simultanément à une modulation de fréquence optique et à une modulation d'intensité et en utilisant le fait qu'un composant modulé de fréquence optique apparaît sous forme d'une variation de phase du composant modulé en intensité. La dispersion peut donc être mesurée avec une grande précision sans effet de dérive du temps de retard de groupe provoqué par une variation de l'environnement extérieur. La précision et le domaine dynamique ne se détériorent pas même au voisinage d'une dispersion nulle. Puisqu'il est possible de rendre asymétrique la forme d'onde d'un signal modulé en fréquence, on peut reproduire le code d'une valeur de dispersion de longueur d'onde. La dispersion de longueur d'onde peut être soumise à un contrôle en service en utilisant un signal de données numérique en tant que signal modulé en intensité.
PCT/JP2001/010185 2000-11-22 2001-11-21 Procede et equipement de mesure de dispersion de longueur d'onde WO2002046715A1 (fr)

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AU2002224067A AU2002224067A1 (en) 2000-11-22 2001-11-21 Method and equipment for measuring wavelength dispersion
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007504728A (ja) * 2003-09-04 2007-03-01 ドイッチェ テレコム アーゲー 光伝送システムのｐｍｄ誘導性の障害確率の決定のための処理法およびデバイス
JP2019105531A (ja) * 2017-12-12 2019-06-27 日本電信電話株式会社 光ファイバ群遅延時間測定方法および測定装置

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