EP1297316A1 - Procede de mesure pour la determination des non-linearites d'une fibre optique - Google Patents

Procede de mesure pour la determination des non-linearites d'une fibre optique

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Publication number
EP1297316A1
EP1297316A1 EP01944955A EP01944955A EP1297316A1 EP 1297316 A1 EP1297316 A1 EP 1297316A1 EP 01944955 A EP01944955 A EP 01944955A EP 01944955 A EP01944955 A EP 01944955A EP 1297316 A1 EP1297316 A1 EP 1297316A1
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EP
European Patent Office
Prior art keywords
optical
signal
pump
power
test signal
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EP01944955A
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German (de)
English (en)
Inventor
Christoph Glingener
Erich Gottwald
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Siemens AG
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Siemens AG
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Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP1297316A1 publication Critical patent/EP1297316A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • G01M11/31—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter and a light receiver being disposed at the same side of a fibre or waveguide end-face, e.g. reflectometers
    • G01M11/319—Reflectometers using stimulated back-scatter, e.g. Raman or fibre amplifiers

Definitions

  • the invention relates to a measuring method for determining the nonlinearities of an optical fiber.
  • nonlinear effects for example self-phase modulation, cross-phase modulation and four-wave mixing, are known, caused by the signal distortions of the optical signal to be transmitted in the optical fiber become.
  • Such nonlinear effects in an optical fiber can be described by the nonlinearity coefficient.
  • the object on which the invention is based is to determine the non-linearities of an optical fiber improve or enable a measurement of the non-linearities of an optical fiber carried out on one side, ie at the beginning or at the end of the optical fiber.
  • the object is achieved by a measuring method according to claim 1 by the features of the characterizing part.
  • the essential aspect of the measuring method according to the invention is to be seen in a first step in which at least one optical test signal is coupled into the optical fiber, the test signal power of which is changed and a first entry threshold of the stimulated Brillouin scattering is determined on the basis of the change in the power of the backscattered optical signal. Furthermore, in a second step, in addition to the optical test signal, at least one modulated optical pump signal with a predetermined pump signal power and a first pump wavelength is coupled into the optical fiber and a second entry threshold of the stimulated Brillouin scatter is determined on the basis of the change in the power of the optical test signal.
  • the non-linearity coefficient of the optical fiber is determined by evaluating at least the first and second entry thresholds, the test and pump signal parameters and the fiber parameters.
  • At least one optical test signal with a test signal power and a test signal wavelength is coupled into the optical fiber in a first step and the power of the backscattered optical signal is measured, as well as a first ratio of the coupled test signal power and the power of the backscattered optical signal. Furthermore, in a second step in addition to the optical test signal having a test signal power and test wavelength, coupling at least one modulated optical pump signal with adjustable pump signal power and a first pump wavelength into the optical fiber and measuring the power of the backscattered optical signal and a second ratio of the coupled test signal power and the power of the backscattered optical signal is determined.
  • the adjustable pump signal power of the modulated optical pump signal is increased or decreased until the second ratio matches the first ratio.
  • the non-linearity coefficient of the optical fiber is then determined by evaluating the test and pump signal parameters as well as the fiber parameters.
  • the variation of the pump signal power of the modulated optical pump signal according to the invention alternatively makes the non-linearity coefficient of the optical by evaluating the existing fiber parameters and test parameters Fiber determinable.
  • test and pump signal parameters evaluated according to the first variant of the measurement method according to the invention provide the test signal wavelength, the predetermined pump signal power, the first pump wavelength and the modulation frequency of the optical pump signal Furthermore, the test signal power, the test signal wavelength, the set pump signal power, the first pump wavelength, the modulation frequency of the optical pump signal are evaluated as the test and pump signal parameters relevant for the second variant of the measuring method according to the invention.
  • 3,705,992 discloses that the entry threshold of the SBS increases in proportion to the ratio of the spectral width ⁇ v s of the optical signal coupled into the optical fiber to the line width ⁇ v B , ie with IS B S - intensity of the injected optical signal at the SBS entry threshold
  • the SBS entry threshold for example for unmodulated optical signals or test signals, is approximately below 10 mW and for binary amplitude-modulated optical signals by a factor of 2 to 3 dB higher.
  • the increase in the case of the binary amplitude-modulated optical signal can be attributed to the distribution of the optical signal power between modulation sidebands and carrier signals, especially since the power of the data signal is distributed over a broad spectral band, in particular at data rates in the Gbit / s range.
  • the SBS leads to signal distortion due to overmodulation, see in particular H.Kawakani, "Overmodulation of Intensity modulated Signals due to stimulated Brillouin scattering", Electronic Letters, Vol. 30, No. 18, pages 1507 to 1508, since essentially the carrier of the amplitude-modulated optical signal, in which the spectral energy density with chip-free modulation is identical to the laser light source, experiences a strong additional attenuation.
  • the SBS entry threshold can be increased considerably by significantly reducing the integrated energy spectral density of the optical signal over a frequency band of width ⁇ v B.
  • the carrier signal power measured with a resolution ⁇ v B , should therefore be reduced to values well below the SBS threshold power. Such a reduction can be achieved by frequency or phase modulation.
  • the SBS effects in the optical fiber essentially take place with a standard single-mode fiber within the first 20 km (effective length L eff ).
  • the optical signal takes the time to pass through the effective length L eff :
  • the optical input power per frequency interval ⁇ v B averaged over a time interval should be much smaller than the transit time ⁇ below the SBS threshold power.
  • the required relationship between the modulation stroke and the modulation frequency for different forms of modulation can be derived from this requirement.
  • Such an amplitude modulation in the optical fiber can be caused, for example, by the non-linear effect of cross-phase modulation (XPM) by an additional coupling in of strongly amplitude-modulated pump signals in addition to the optical signals.
  • the phase modulation along the optical fiber caused by the cross-phase modulation (XPM) shows an RC low-pass behavior.
  • the cut-off frequency ⁇ g of the "low-pass behavior" decreases linearly with increasing channel spacing due to the dispersion-related slip of the WDM transmission channels.
  • the height of the modulation frequency must therefore be chosen to be as low as possible, although this should in no case be below the line width ⁇ v B.
  • J SB S ( ⁇ ) Isas (z) ⁇ exp (g 5 ⁇ I s ⁇ L ejf -a ⁇ z) (Al)
  • the optical signal is increasingly phase-modulated due to the XPM with increasing distance.
  • the phase modulation for example with a phase shift of 1,435 rad, distributes the spectral power of the carrier signal over several frequencies, ie, for example, evenly over the carrier wave and the two first sidebands. If the modulation frequency is greater than the SBS line width ⁇ v B , only about 1/3 of the spectral energy density is available for the formation of the SBS, for example, ie the SBS entry threshold increases by a factor of 3 from the location at which such phase shift is achieved by the XPM.
  • the local SBS entry threshold can thus be calculated as a function of the properties of the injected modulated pump signal and the optical fiber and the injected optical signal, and the resulting SBS entry threshold dependent on the optical pump signal can be determined for the entire fiber.
  • the calculation of the SBS entry threshold in the presence of the optical pump signal is carried out by splitting the fiber into small sections in combination with Eq. (A-l) realized.
  • ISBS (Z / 2) I SBS (z) * exp (g B * I s * exp (- ⁇ * z / 2) * l / ⁇ * (1-exp (- ⁇ * z / 2)) - ⁇ z / 2) (A-3)
  • ISBS (0) I SBS (z / 2) * exp (g B * I s * 1 / ⁇ * (l-exp (- ⁇ * z / 2)) - ⁇ z / 2) (A-
  • Is B s (z / 2) I S Bs (z) * exp [g B * Is * l / ⁇ * (l-exp (- ⁇ * z / 2)) * exp (- ⁇ * z / 2) * o 2 (m (z / 2)) - ⁇ z / 2] (A-7)
  • Equation (A-7) inserted in equation (A-4) provides the intensity of the backscattered optical signal I SBS , taking the XPM into account.
  • I SBS (0) I SBS (z) * exp [g B * I s * l / ⁇ * (l-exp (- ⁇ * z / n)) * (A-9) nl
  • the effective length L eff is, according to equations (A-10) and (A-8), dependent on the non-linearity coefficient ⁇ of the optical fiber and the optical power of the amplitude-modulated optical pump signal I P.
  • Le (k * z / n, ⁇ , D, ⁇ , fmod) describes the variation of the modulation index ⁇ m (kz / n) ⁇ inter alia as a function of the modulation frequency and the wavelength distance between the optical pump signal and the test signal.
  • the wavelength difference between pump and test signal ⁇ and the modulation frequency fmod and the SBS entry threshold P SB ⁇ can be determined from equation (A-II) and equation (A-12).
  • the displacement of the SBS entry threshold P SBS is determined by the change in the spectrum of the coupled-in optical test signal, which is caused by the cross-phase modulation (XPM) resulting from the sinusoidally amplitude-modulated optical pump signal in the optical fiber, to determine the non-linearity coefficient ⁇ and the dispersion D. Equation (A-12) is used.
  • the Brillouin Gain constant g B and the effective area A eff are optical fiber constants, which are naturally available for the optical fiber to be measured or can be determined without considerable technical effort.
  • the effective length L eff (z, ⁇ , I P , D, ⁇ , fmod) can be influenced by the test conditions and, according to formula (A-II), depends on the length of the fiber z, the fiber attenuation ⁇ , from the wavelength difference between the optical pump and test signal ⁇ and the modulation frequency fmod of the amplitude-modulated optical pump signal.
  • Nonlinearity coefficient ⁇ of an optical fiber can with a wavelength difference between the optical pump and test signal ⁇ , for example less than 1 n and a modulation frequency fmod of the amplitude-modulated optical pump signal less than 200 MHz, the influence of dispersion in
  • a first and a second measurement of the backscattered optical power can be carried out, with only the optical test signal with a predetermined power and wavelength being coupled into the optical fiber in the first measurement, and in addition to the optical test signal with the second measurement modulated optical pump signal for generating cross-phase modulation (XPM) is coupled into the optical fiber.
  • the coupled power of the optical test signal is increased until there is a predetermined ratio of the coupled power of the optical test signal and the backscattered power.
  • the powers of the optical test signal and the optical pump signal set together with the test and pump signal parameters and the fiber parameters in the measurement method for the first and second measurement are in turn evaluated according to equations (A-II) and (A-12), the dispersion D is negligible.
  • the wavelength difference between the optical pump and test signal ⁇ is chosen, for example, to be greater than 10 nm, ie the effective length L eff depends on the fiber dispersion D. and the wavelength difference between the optical pump and test signal ⁇ .
  • a third SBS entry threshold P SBS3 which runs differently to the second SBS entry threshold P SBS2 due to the modified pump signal parameters, is determined or with the aid of a third measurement which, in addition to the optical test signal, the modified modulated optical pump signal for generating the Cross-phase modulation (XPM) is injected into the optical fiber, the injected power of the optical test signal is increased until there is a predetermined ratio of the injected power of the optical test signal and the backscattered power.
  • XPM Cross-phase modulation
  • FIG. 1 shows an example of a measuring arrangement for realizing the measuring method according to the invention
  • FIG. 2 shows a shift of the SBS entry thresholds according to the invention
  • FIG. 3 in a further calculated diagram the measurement method according to the invention for determining the non-linearity constants and dispersion constants.
  • FIG. 1 shows a measuring arrangement MAO for implementing the measuring method according to the invention for determining the non-linearities of an optical fiber OF with the aid of a block diagram, an optical standard single-mode fiber OF being selected as the test object in FIG. 1 as an example.
  • the measuring arrangement MAO shown in FIG. 1 has a test signal unit TSU, a pump signal unit PSU, an optical coupler OK, a controllable switching unit S, a circulator Z, a filter unit FU, a measuring transducer MW and a control and evaluation unit CU.
  • the test signal unit TSU has a control input ri and a signal output e which is connected to the circulator Z via the optical coupler OK and via the first optical connecting line VL1.
  • the optical coupler OK is in turn connected to the output e of the controllable switching unit S via a second optical connecting line VL2.
  • the circulator Z is additionally connected via a third optical connecting line VL3 to the test object - the optical fiber OF - and 1975
  • a first feed line ZL1 is connected to the input fi of the filter unit FU, the output fe of which is connected to the input i of the transducer MW via a second feed line ZL2.
  • the output e of the measuring transducer MW is connected via an electrical supply line EZL to the control and evaluation unit CU, which via a control line SL with control input si of the controllable switching unit S, via a first control line RL1 with the control input ri of the test signal unit TSU and via a second Control line RL2 is connected to the control input ri of the pump signal unit PSU.
  • the pump signal unit PSU further has a first and second output el, e2, which are connected to the first and second input il, i2 of the controllable switching unit S.
  • a circulator Z for example an optical coupler OK can be used - not shown in FIG. 1.
  • a first power controller RL1, a second power controller LR2, a switching controller SR, a memory unit MEM, an evaluation unit AE and a control unit MC — for example implemented in a microprocessor — are provided in the control and evaluation unit CU.
  • the memory unit MEM, the first and second power controllers RL1, RL2, the switching controller SR and the evaluation unit AE are connected to the control unit MC, the first and second power controllers LR1, LR2 being additionally connected to the evaluation unit AE.
  • the first power controller LR1 via the first control line RL1 with the test signal unit TSU, the second power controller LR2 via the second control line RL2 with the pump signal unit PSU, and the switching controller SR via the switching line SL with the controllable switching unit S and the evaluation unit AE via the electrical supply line EZL connected to the measuring transducer MW.
  • the measurement method according to the invention is implemented, for example, on the basis of a measurement routine MR and an evaluation routine BWR in the control unit MC, which include the test signal unit TSU, the pump signal unit PSU and the control unit. 1975
  • an optical test signal ots with a predetermined first wavelength ⁇ l and a predetermined power P s is generated in the test signal unit TSU, wherein the optical test signal ots can additionally be amplitude-modulated, for example, with a first modulation frequency vl.
  • the optical test signal ots is thus modulated or unmodulated into the test object, that is, into the optical fiber OF.
  • the optical test signal ots is transmitted to the circulator Z, for example via the optical coupler OK and via the first distributor line VL1, and is coupled into the optical fiber OF by the circulator Z via the third distributor line VL3.
  • the optical test signal ots is coupled into the optical fiber OF, ie none of the optical pump signals ops generated in the pump signal unit PSU is switched through to the optical coupler OK by the controllable switching unit S.
  • the third, unassigned input 13 of the controllable switching module S is switched through to the output e by the controllable switching unit S with the aid of a control command ss generated in the control controller SR.
  • the nonlinear effect of the "stimulated Brillouin scattering (SBS)", ie the stimulated Brillouin scattering, is formed.
  • This narrow-band, non-linear effect of the SBS causes part of the optical test signal ots to be backscattered or reflected in the opposite direction to the coupling direction.
  • This backscattered optical signal ros is fed via the circulator Z and via the first feed line ZL1 to the filter input fi of the filter unit FU.
  • the backscattered optical signal ros is filtered and the filtered backscattered signal largely emitted at filter output fe.
  • the filtered backscattered signal is then largely transmitted via the second feed line ZL2 to the input i of the measuring transducer MW, for example an opto-electrical transducer, and converted into an electrical signal using the measuring transducer MW.
  • the electrical signal is fed to the control and evaluation unit CU or the evaluation unit AE via the electrical feed line EZL, in which the power P ros of the electrical signal es and thus of the backscattered optical signal ros is determined or evaluated.
  • the power P ros of the backscattered optical signal ros is determined by the evaluation unit AE controlled by the control unit MC and the determined backscattered signal power P ros is compared with the power P s of the optical test signal ots stored in the memory unit MEM using the evaluation routine BWR.
  • the first power controller LR1 controlled by the measurement and evaluation routine MR, BWR, is used
  • a first control signal rsl for increasing or possibly reducing the power P s of the optical test signal ots is formed.
  • the power P s of the optical test signal ots is increased, for example, until a first entry threshold SBSi of the stimulated Brillouin scatter is reached, ie the power P ros of the backscattered signal ros corresponds, for example, to 1/10 of the power P s of the coupled test signal ots.
  • the power or first SBS entry threshold P S1 of the optical test signal ots is stored in the memory unit MEM in accordance with the measurement routine MR.
  • At least one modulated optical one Pump signal ops is coupled into the optical fiber OF with a predetermined first pump signal power P P1 and a first wavelength ⁇ l.
  • an optical pump signal ops with a first wavelength ⁇ l and additionally the optical pump signal ops with a first modulation frequency vl are amplitude-modulated in the optical pump signal unit PSU, wherein the amplitude modulation can be designed, for example, as a sine, a rectangular or a sawtooth-shaped amplitude modulation.
  • the modulated optical pump signal ops is emitted at the first output el of the pump signal unit PSU to the first input il of the controllable switching unit S.
  • a control signal ss for switching the first input il of the controllable switching unit S to the output e is generated by the measuring routine MR executed in the control unit MC in the switching regulator SR and transmitted to the controllable switching unit S via the control line SL , Following the connection of the optical pump signal ops from the first input il to the output e of the controllable switching unit S, the optical pump signal ops is passed to the optical coupler OK via the second distribution line VL2.
  • the optical pump signal ops is coupled into the first distribution line VL1 and transmitted to the circulator Z in addition to the optical test signal ots.
  • the circulator Z couples the optical test signal ots and the optical pump signal ops into the optical fiber OF via the third optical distribution line VL3.
  • the additional coupling in of the modulated optical pump signal ops generates the nonlinear effect of the cross-phase modulation (XPM) in the optical fiber OF and thus causes phase modulation of the optical test signal ots, which widens the frequency spectrum of the optical test signal ots.
  • the broadening of the frequency spectrum of the optical test signal ots initially reduces the The power of the backscattered optical signal ros ab, ie the part of the coupled-in optical test signal ots, which is backscattered or reflected opposite to the coupling direction due to the narrow-band nonlinear effect of the SBS, thus decreases.
  • the backscattered optical signal ros is in turn passed via the circulator Z and via the first feed line ZL1 to the filter input fi of the filter unit FU.
  • the backscattered optical signal ros is filtered in the filter unit FU and the filtered backscattered signal is largely emitted at the filter output fe.
  • the filtered backscattered signal is then largely transmitted to the input i of the measuring transducer MW via the second feed line ZL2 and converted into an electrical signal using the measuring transducer MW.
  • the electrical signal is fed to the control and evaluation unit CU or the evaluation unit AE via the electrical feed line EZL, in which the power P ros of the electrical signal es and thus of the backscattered optical signal ros is determined or evaluated.
  • the power unit P ros of the backscattered optical signal ros is determined by the evaluation unit AE controlled by the control unit MC, and the determined backscattered signal power P ros is determined with the power P s of the optical power stored in the memory unit MEM using the evaluation routine BWR Test signal ots compared.
  • the first power controller LR1 controlled by the measurement and evaluation routine MR, BWR of the control unit MC, the first control signal rsl for increasing the power P s of the optical test signal ots is formed.
  • the power P s of the optical test signal ots is increased until a second entry threshold SBS 2 of the stimulated Brillouin scatter, which is higher than the first entry threshold SBSi, is reached, ie the power P ros of the backscattered signal ros in turn corresponds to 1/10 of the power P, for example s of the coupled test signal ots.
  • the value of when the second income Step threshold SBS 2 of the stimulated Brillouin scatter currently output second critical power P s2 or second SBS entry threshold P SBS2 of the optical test signal ots is stored in the memory unit MEM in accordance with the measurement routine MR. Furthermore, the currently set first optical pump signal power P P is stored in the memory unit MEM.
  • FIG. 2 shows an example of the first SBS entry threshold SBSi and the shifted or increased second SBS entry threshold SBS 2 in a diagram.
  • the diagram has a horizontal axis (abscissa) and a vertical axis (ordinate), the power P s of the injected optical test signal ots being plotted along the horizontal axis and the power P ros of the backscattered optical signal ros being plotted in dBm along the vertical axis is.
  • the optical test signal ots was coupled into the optical fiber OF in accordance with the first step of the measurement method according to the invention, the test signal power P s was increasingly increased and the change or increase in the power P ros of the backscattered optical signal ros was recorded , On the basis of the diagram shown in FIG. 2, the occurrence of the non-linear effect of the SBS becomes clear, which, for example in the case shown, is at a test signal power P s of approximately 0.002 watts.
  • SBS entry threshold SBS X results in a band of test signal power P s of approximately 2 dBm and then flattens out again, so that the profile of power P ros of the backscattered optical signal ros over the test signal power P s assumes almost the same slope as immediately before the first SBS entry threshold SBS X.
  • test signal ots an optical pump signal ops is coupled into the optical fiber OF, as a result of which the cross-phase modulation XPM occurring in the optical fiber OF shifts the SBS entry threshold to the right, ie the non-linear effect of the SBS occurs at a higher coupled test signal power P s on.
  • an optical pump signal ops was coupled into the optical fiber OF, which was amplitude-modulated with a modulation frequency of 20 MHz and had a pump signal power of 0.2 watts.
  • the wavelength difference ⁇ between the optical test signal ots and the optical pump signal ops was approx. 10 nm.
  • the shift in the SBS entry thresholds that can be seen from the diagram is approx. 2 dBm, together with the known test and pump signal parameters and the known fiber parameters for determining the Nonlinearity coefficient ⁇ evaluated.
  • a shift of the SBS entry threshold by 1 to 3 dB is required.
  • the diagram shows a first, second and third first, second and third measurement curve MK1, MK2, MK3 determined from the known measurement parameters determined according to the invention.
  • the diagram has a horizontal axis (abscissa) and a vertical axis (ordinate), the product of the polarization-dependent constant ⁇ , the non-linearity constant ⁇ and the pump power Ppi / Pp 2 ⁇ * Y being coupled in along the horizontal axis * P P is plotted on a logarithmic scale and along the vertical axis the product of the dispersion constant D, the wavelength difference ⁇ and the modulation frequency fmod D * ⁇ * fmod.
  • the measurement curves MK1, MK2, MK3 shown result for a 100 km long optical fiber OF with an attenuation constant of 0.2 dB, the product ⁇ * ⁇ * P P on the abscissa having a value range for the pump power P P of approx. 0.1 to 2 watts and the product D * ⁇ * fmod plotted on the ordinate comprises a range of values for the wavelength spacing ⁇ around 10 nm at a modulation frequency of 0 to 1 GHz.
  • the first measurement curve MK1 stands for an increase in the first SBS entry threshold SBSi by 1 dB
  • the pump signal power P P coupled into the optical fiber for this purpose accordingly increased from 0.1 watts to 0.2 watts.
  • a first, second, third and fourth measurement point MP1 to MP4 along the second and third measurement curve MK2, MK3 are marked in FIG. 3, which are selected for the determination of the non-linearity constant ⁇ and the dispersion constant D using an iterative evaluation method, for example.
  • the determination of at least two measurement values is sufficient.
  • the second measurement curve MK2 shown in FIG. 3, in particular the first measurement point MP1 is used, for example, to explain the determination of the nonlinearity constant ⁇ with the aid of the evaluation routine BWR.
  • the first measurement point MP1 denotes the intersection of the second measurement curve MK2 with the abscissa in FIG. 3, which thus takes into account the negligible dispersion constant D and the small wavelength difference ⁇ for the case under consideration.
  • a negligible ordinate value and a logarithmic abscissa value (10 * log10) of -40.9 1 / m / W can thus be read from the diagram in FIG. 3 as coordinates of the first measuring point MP1.
  • the first pump signal power P ⁇ stored in the memory unit MEM is 20 dBm, which corresponds to a first pump signal power P P ⁇ of 100 mW.
  • ⁇ l
  • the dispersion properties, ie the dispersion constant D, of the optical fiber OF are determined in such a way that in a third step, in addition to the optical test signal ots, the amplitude-modulated optical pump signal ops with the first pump signal power P P ⁇ and a second Pump wavelength ⁇ 2 is coupled into the optical fiber OF and again a third shifted entry threshold SBS 3 of the stimulated Brillouin scattering is determined by changing the power of the backscattered optical signal ros by increasing the first pump signal power P P ⁇ until the power P ros of the backscattered signal ros in turn corresponds, for example, to 1/10 of the power P s of the injected test signal ots.
  • the first pump power P PX must be increased by 3 dB in order to again obtain the second SBS entry threshold SBS 2 .
  • the first and third measurement curves MK1, MK3 are used for the determination with the aid of the evaluation routine BWR.
  • a first measured pump signal power P P ⁇ of 20 dBm and in the calculation of the third measurement curve MK3, a third measured pump signal power P P of 26 dBm was evaluated, which increases the pump power P P by 6 dB to compensate for the Increasing the wavelength difference ⁇ corresponds, that is, in order to achieve the second SBS entry threshold SBS 2 , a first pump signal power P Pi is required, for example, in the case of a first optical pump signal opsl with a first pump wavelength ⁇ l and when using a second optical pump signal ops2 with an increased second pump wavelength ⁇ 2 a second pump signal power P P2 increased by 6 dB is required.
  • the third measurement curve MK3 thus obtained which is shifted to the right in the diagram compared to the first measurement curve MK1, is evaluated starting at the second measurement point MP2 to determine the dispersion constant D with the aid of an iterative evaluation method.
  • the data record representing the third measurement curve MK3 and stored in the memory unit MEM is evaluated with the aid of the evaluation routine BWR in such a way that the intersection point between the abscissa and the third measurement curve MK3, the second measurement point MP2 is selected and starting from the abscissa value of the second Measuring point MP2, the abscissa value of the fourth measuring point is determined from the data set by the abscissa value of the second measuring point MP2 being shifted to the right or decreased by the amount of the increase in the pump signal power P P , in the exemplary embodiment under consideration by 6 dB. Based on this, the associated ordinate value of the fourth measuring point MP4 is determined.
  • the first measurement point MPl or starting point of the iterative evaluation method was not precise enough and is improved as follows.
  • the previously determined ordinate value of the fourth measuring point MP4 is divided by the difference between the first and second product, the factor 10, and thus a new improved ordinate value for the first measuring point MPl is determined.
  • the associated new, improved abscissa value of the first measuring point MP1 is determined on the basis of the database and stored in the memory unit MEM for further processing.
  • the new improved abscissa value of the second measurement point MP2 is again shifted or decreased by the amount of the increase in the pump signal power P P , in the exemplary embodiment under consideration by 6 dB, in a second run of the iterative evaluation method.
  • an improved ordinate value of the resulting new fourth measuring point MP4 is determined. In most cases, this evaluation method converges after a few iterations, so that the ordinate value obtained for the fourth measuring point MP4 can be used to determine the dispersion constants in accordance with the following equation:
  • the measuring arrangement according to the invention is in no way limited to a transmission-side implementation, but can be used for bige optical transmission media can also be used at the receiving end.

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Abstract

L'invention concerne un procédé de mesure qui permet de réaliser d'un côté, c'est-à-dire, au début ou à la fin d'une fibre optique (OF), la mesure des non-linéarités de cette fibre optique. A cet effet, un signal test optique (ots) dont la puissance (Ps) est modifiée est injecté dans la fibre optique (OF), un premier seuil d'entrée (SBS1) de la dispersion de Brillouin stimulée étant déterminé sur la base de la modification de la puissance (Pros) du signal optique rétrodiffusé (ros). En outre, dans une seconde étape, en plus du signal test optique (os), au moins un signal de pompage optique (ops) modulé est injecté dans la fibre optique (OF), un second seuil d'entrée (SBS2) de la dispersion de Brillouin stimulée est déterminé sur la base de la modification de la puissance (Ps) du signal test optique (ots), et, par évaluation au moins du premier et du second seuil d'entrée (SBS1, SBS2), des paramètres du signal test et du signal de pompage et des paramètres de la fibre, le coefficient de non-linéarité ( gamma ) de la fibre optique (OF) est déterminé.
EP01944955A 2000-06-07 2001-05-22 Procede de mesure pour la determination des non-linearites d'une fibre optique Withdrawn EP1297316A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10028144 2000-06-07
DE10028144A DE10028144C1 (de) 2000-06-07 2000-06-07 Messverfahren zur Bestimmung der Nichtlinearitäten einer optischen Faser
PCT/DE2001/001975 WO2001094905A1 (fr) 2000-06-07 2001-05-22 Procede de mesure pour la determination des non-linearites d'une fibre optique

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EP1297316A1 true EP1297316A1 (fr) 2003-04-02

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EP (1) EP1297316A1 (fr)
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WO (1) WO2001094905A1 (fr)

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See references of WO0194905A1 *

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US6819412B2 (en) 2004-11-16
WO2001094905A1 (fr) 2001-12-13
US20030128946A1 (en) 2003-07-10
DE10028144C1 (de) 2001-11-29

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