WO2002005463A1 - Moniteur pmd procede et dispositif permettant de determiner la dispersion modale de polarisation d'un systeme de transmission et en particulier d'une fibre de transmission - Google Patents

Moniteur pmd procede et dispositif permettant de determiner la dispersion modale de polarisation d'un systeme de transmission et en particulier d'une fibre de transmission Download PDF

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Publication number
WO2002005463A1
WO2002005463A1 PCT/EP2001/008006 EP0108006W WO0205463A1 WO 2002005463 A1 WO2002005463 A1 WO 2002005463A1 EP 0108006 W EP0108006 W EP 0108006W WO 0205463 A1 WO0205463 A1 WO 0205463A1
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WO
WIPO (PCT)
Prior art keywords
polarization
arrangement according
signal
laser
pmd
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/EP2001/008006
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German (de)
English (en)
Inventor
Adalbert Bandemer
Egbert Krause
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thorlabs GmbH
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Thorlabs GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE10033819A external-priority patent/DE10033819A1/de
Application filed by Thorlabs GmbH filed Critical Thorlabs GmbH
Priority to AU2001289643A priority Critical patent/AU2001289643A1/en
Publication of WO2002005463A1 publication Critical patent/WO2002005463A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
    • H04B10/2569—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to polarisation mode dispersion [PMD]
    • 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
    • G01M11/336—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 polarization mode dispersion [PMD]

Definitions

  • the invention relates to a method and an arrangement for determining the polarization mode dispersion (PMD) of a transmission system and in particular of a (D-WDM) transmission fiber.
  • PMD polarization mode dispersion
  • the polarization mode dispersion comprises all polarization-dependent propagation time effects in which the signal propagation can be completely described by the propagation behavior of two mutually independent and mutually orthogonal polarization modes. Since the birefringence by external influences, such as temperature and mechanical impact - for example, by wind pressure on overhead lines - is constantly changing, and also length depends on the waves ⁇ , is constantly changing, both the position of the "principial states of polarization" (PSP) and the runtime difference between the PSP's. This is also known as polarization mode dispersion.
  • PMD measuring devices which operate either according to the interferometric method or according to the Jones matrix method. These known PMD measuring devices require between a few tens of seconds and a few minutes per measurement, are very voluminous and also work with components to be moved during the measurement. They are therefore not suitable for PMD compensation devices that are located on transmission links.
  • the invention has for its object to provide a method and an arrangement for determining the polarization mode dispersions of a transmission system and in particular a transmission fiber, which allows a conclusion on the changes in the PMD in a short measurement time, so that they, for example, in a PMD compensation - Station device can be used as a PMD monitor.
  • the invention is based on the basic idea of relating the optical data signal to be analyzed with the radiation in an optoelectronic heterodyne receiver superimpose its wavelength tunable optical element and in particular a laser. According to the invention, the polarization state of the signal to be analyzed can thus be measured as a function of the wavelength.
  • the spectrum of a digital, optical data signal has a defined spectral width, which depends on the bit rate. The higher the bit rate, the wider the associated spectrum.
  • the different propagation speeds of the different spectral components in different polarization states within the optical fiber of the transmission link cause signal distortions after a sufficient transmission length, which make it impossible to restore the digital information or at least negatively influence the signal quality.
  • this spectrum is measured with spectral resolution.
  • the useful amplitude of the electrical superimposition signal depends on the two signal powers, but also directly on the polarization directions of the incoming signal and the local overlay laser.
  • SOP state of polarization
  • These can be, for example, the horizontal and vertical polarization with the vectors (Si, S 2 , S 3 ):
  • the spectral distribution of the total signal power is determined using these two orthogonal polarization states.
  • the power of each mixed product is proportional to the product of the input power and the local laser power and a factor k that describes the agreement of the two polarizations.
  • the polarization agreement factor a ( ⁇ SOP) is from the .relative distance of the SOP to the. Poincare ball dependent:
  • ⁇ SOP The amplitude factor a
  • the polarization direction of the filtered spectral component is thus determined at each wavelength of the input spectrum.
  • the PMD now shows its effects in that the radiation from the data source is split into two power components, which correspond to the Principal States of Polarization (PSP n ) at the input of the transmission link.
  • a relative time delay - called a differential group delay (DGD) - occurs between the two, usually differently sized, power components.
  • the two power components reach the PMD monitor with polarization directions that correspond to the PSP out : .
  • the data signal does not suffer any distortion from PMD if the DGD is 0, or the polarization of the input radiation is identical to a PSP in the transmission route is. In both cases, the output polarization remains constant at the end of the transmission path, even if the wavelength varies slightly:
  • the measurement data S) P E ( ⁇ ) are available for the relevant wavelength range from the previous calculations. This data is sufficient to determine the PMD using the Poincare (Arc-Angle) method. The difference quotient is calculated at every point on the curve
  • the arrangement according to the invention has the advantage that the changes in the PMD e.g. of fiber sections to be detected.
  • the proposed arrangement and the proposed method also enable the wavelength-dependent Stokes parameters to be calculated.
  • the use of the fast and optionally tunable local laser and the use of fast-reacting polarization control elements make it possible to set up a PMD monitor that e.g. can work with different resolutions in selectable sub-areas within the entire wavelength range.
  • it is a solution of small size and a solution without moving components, so that real-time PMD monitoring systems can be implemented with a particularly long life.
  • Fig. 4 shows a fourth embodiment of the invention
  • Fig. 5 shows the quantities P E g es ( ⁇ ) and SOP E ( ⁇ ) as a function of
  • FIG. 6 schematically shows the structure of the polarization controller within the PMD monitor
  • FIG. 1 shows the schematic structure of a first exemplary embodiment of an arrangement for determining the polarization mode dispersion (PMD) of a transmission fiber 1, ie a PMD monitor.
  • the signal of the transmis- sions wholesale 1 which may in particular be a transmission fiber in a D-WDM system, is applied to the one input port of an optical coupler (5), which is a 3dB coupler in this embodiment.
  • the light of a local, tunable laser (2) is applied to the other input connection of the coupler (5) in the manner described below, which advantageously has a laser that can be tuned in wavelength, such as an electronically tunable distributed Bragg reflector laser ( DBR laser) or an electronically tunable distributed feedback laser (DFB laser).
  • DBR laser electronically tunable distributed Bragg reflector laser
  • DFB laser electronically tunable distributed feedback laser
  • the laser (2) is tuned by an evaluation and control unit (3) so that the wavelength range of the tuning sweeps over the spectrum of the signal of the fiber (1) to be analyzed.
  • the polarization of the local laser (2-) is adjusted to the four different polarization states necessary to determine the PMD using a polarization controller (4).
  • the optical coupler (5) sums the signal of the fiber (1) to be analyzed with the radiation from the local laser (2).
  • the summed signal is applied to an optoelectronic receiver (6) made in the first guiding For 'example of a photodiode.
  • the electrical output signal of the receiver (6) corresponds to the optical beat signal.
  • An RF filter and evaluation unit (7) limits the bandwidth of the beat signal and filters out unwanted baseband signals.
  • the output signal of the unit (7) is to the evaluation and Control unit (3) created. This analyzes the course of the measured variable at the different polarizations and wavelengths of the local laser (2).
  • the evaluation and control unit (3) generates an actuating signal (8) which is proportional to the PMD distortion of the input signal (1) to be analyzed and which is suitable for controlling a PMD compensator unit.
  • the evaluation and control unit (3) controls the laser (2) and the polarization controller (4) described in more detail below.
  • the advantage of such an arrangement with an electronically tunable semiconductor laser (2) is that, firstly, the tuning to the different frequencies can be done very quickly and secondly with a selectable tuning steepness, and areas of increased information services can thus be treated with increased resolution. In the sense of a smart monitor, this is desirable.
  • Fig. 2 shows a second embodiment of the invention that differs from the first embodiment of FIG. 1 in that the receiver (6), which has only one photodiode, is replaced by an optoelectronic balance receiver (9) in which the baseband components of the optical signals are largely be suppressed.
  • This exemplary embodiment is distinguished by a higher dynamic range than in the arrangement according to FIG. 1.
  • the remaining units or elements correspond to the i. V. m. Fig. 1 explained units or elements, so that there is no renewed presentation.
  • Fig. 3 shows a third embodiment of the invention that differs from the second embodiment in that the provision of the necessary different polarization states for the optoelectronic superimposition is obtained in that the polarization controller (4) is not arranged in the branch of the local laser (2) but in the branch of the ' input signal (1).
  • Fig. 4 shows a fourth embodiment of the invention, in which the switching of the polarization states is avoided by using a polarization diversity receiver (12) instead of the receivers (6) or (9), the beam splitter (10, 11) with polarization filter properties are connected upstream.
  • a polarization diversity receiver (12) instead of the receivers (6) or (9)
  • the beam splitter (10, 11) with polarization filter properties are connected upstream.
  • FIG. 5a schematically shows the spectrum P Eges ( ⁇ ) as a function of the wavelength ⁇ of the input signal.
  • SOP E ( ⁇ ) is constant over the wavelength range in the case of a lack of PMD or in the case of a fully compensated PMD.
  • the polarization splitter has fiber squeezers with piezo elements.
  • the light from the local laser (2) can be brought into any desired output polarization by means of two piezo fiber squeezers (13) and (14) which are rotated relative to one another by 45 °.
  • a fiber coupler (15) provides the main part of the total power at the output (19) and branches off a small part for the polarization control.
  • Another piezo fiber squeezer (16) is modulated by a signal generator (17).
  • the polarizer (18) is mounted rotated by 45 ° with respect to the piezo fiber squeezer (16).
  • the light modulated in its polarization direction obtains an amplitude modulation through the polarizer (18), which is analyzed by the optical receiver (19).
  • the measurement signal which reflects the modulation amplitude, is applied to an evaluation and control unit (20).
  • the two piezo fiber squeezers (13) and (14) " are controlled so that the modulation amplitude at the receiver (19) becomes 0. This is the case when the polarization at the piezo fiber squeezer (16) is exactly horizontal or vertical (eigenmodes of the birefringent fiber element) at the outlet (21) of the arrangement, due to the intrinsic birefringence of connections tion fibers and couplers (15) two changed polarizations, but their orthogonality to one another are unchanged.
  • the evaluation and control unit (20) drives the 4 control voltages for the piezo fiber squeezer (13) and (14) one after the other and thus generates the four required polarizations for the Determination of the Stokes parameters using the described method.
  • Figures 7 and 8 show embodiments for the i. V. m. Fig. 4 explained fourth embodiment.
  • Fig. 7 shows a first embodiment in which balance receivers are used.
  • the signal of the transmission fiber 1 acts on a first beam splitter (beam splitter BS) 51; the beam of the tunable laser 2 acts on a second beam splitter 52.
  • a further beam splitter 53 which is preceded by an element 55 in the branch of the laser 2, which is a ⁇ / 4 plate.
  • photodiodes 91, 92, 93 and 94 are arranged, of which two photodiodes are connected as balance receivers.
  • the photodiodes 91 and 92 are preceded by platelets 56 and 57 which polarize at 45 °.
  • the balance receiver formed by the photodiodes 91 and 92 thus receives the signal polarized at + 45 °, while the balance receiver formed by the photodiodes 93 and 94 receives the circular (clockwise) polarized signal.
  • An element 54 is arranged in the other branch of the two beam splitters 51 and 52, which is described in more detail below:
  • Element 54 is a cube that has a first input port area that is acted upon by the other branch of beam splitter 51 and a second input port area that is acted upon by the other branch of beam splitter 52.
  • One diagonal plane of the cube is designed as a polarization beam splitter PBS, while the other diagonal plane is a simple beam splitter BS.
  • the polarization beam splitter is arranged adjacent to the input connection areas.
  • Photodiodes 95 to 98 are arranged adjacent to the four regions of the cube, through which the through the light entering the first and the second input connection area emerges again.
  • the balance receiver formed by the photodiodes 95 and 96 receives the vertically polarized light, while the balance receiver formed by the photodiodes 97 and 98 receives the horizontally polarized light.
  • This arrangement makes it possible to dispense with polarization-changing elements when using balance receivers.
  • the cube 54 has the same optical properties as four mutually aligned cubes, two of which are polarization beam splitters and two “simple” beam splitters.
  • the cube 54 can in particular be constructed from four 90 ° prisms which are coated on the surfaces on which they are joined in such a way that the corresponding surfaces act as beam splitter surfaces or as polarization beam trailer surfaces.
  • FIG. 8 shows a simplification of the i. V. m. Fig. 7 embodiment described, in which simple photodiodes 91, 93, 95 and 97 are used instead of balance receivers. Otherwise, the elements correspond essentially to the i. V. m. Fig. 7 described elements.
  • FIG. 9 shows an example of the use of the PMD monitor as a central component of a PMD compensator in an optical transmission system for high data rates.
  • the signal from the transmission laser (23) modulated by the data source (22) arrives via the transmission link (24) to the location at which the Stokes parameters are determined. In this example, this should be without restriction of the general training at the place of reception.
  • a PMD compensation unit (25) arranged there in front of the demodulator will compensate the PMD of the transmission fiber (24) when controlled by the control unit (29). This is done before the signal reaches the demodulator
  • the PMD monitor is designed in accordance with one of the exemplary embodiments described above.
  • the output signal of the PMD monitor (28) controls the PMD compensator via the control unit (29).

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  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Dispersion Chemistry (AREA)
  • Optics & Photonics (AREA)
  • Analytical Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Optical Communication System (AREA)

Abstract

Procédé et dispositif permettant de déterminer la dispersion modale de polarisation d'un système de transmission et en particulier d'une fibre de transmission. La présente invention se caractérise en ce que dans un récepteur hétérodyne opto-électronique, le faisceau d'un élément optique ajustable pour ce qui est de sa longueur d'onde, en particulier d'un laser, est superposé à un signal de données optique à analyser. Selon la présente invention, l'état de polarisation du signal à analyser peut être mesuré en tant que fonction de la longueur d'onde.
PCT/EP2001/008006 2000-07-12 2001-07-11 Moniteur pmd procede et dispositif permettant de determiner la dispersion modale de polarisation d'un systeme de transmission et en particulier d'une fibre de transmission Ceased WO2002005463A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2001289643A AU2001289643A1 (en) 2000-07-12 2001-07-11 Pdm monitor method and device for determining the polarisation mode dispersion of a transmission system, especially a transmission fibre

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10033819A DE10033819A1 (de) 2000-03-04 2000-07-12 PMD-Monitor-Verfahren und Anordnung zur Ermittlung der Polarisations-Moden-Dispersion eines Transmissionssystems und insbesondere einer Transmissionsfaser
DE10033819.4 2000-07-12

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WO2002005463A1 true WO2002005463A1 (fr) 2002-01-17

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PCT/EP2001/008006 Ceased WO2002005463A1 (fr) 2000-07-12 2001-07-11 Moniteur pmd procede et dispositif permettant de determiner la dispersion modale de polarisation d'un systeme de transmission et en particulier d'une fibre de transmission

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102253498A (zh) * 2010-05-18 2011-11-23 昂纳信息技术（深圳）有限公司 一种减小偏振模偏振的色散补偿器

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0260745A1 (fr) * 1986-09-17 1988-03-23 Koninklijke Philips Electronics N.V. Dispositif de détection optique hétérodyne d'un signal optique et système de transmission optique muni d'un tel dispositif
US5896211A (en) * 1990-09-14 1999-04-20 Fujitsu Limited Optical communication system
EP0964237A1 (fr) * 1997-11-28 1999-12-15 Fujitsu Limited Procede de mesure de la dispersion en mode de polarisation, dispositif de commande de compensation de dispersion et procede de commande de compensation de dispersion
WO2000077956A1 (fr) * 1999-06-10 2000-12-21 Fiberspace, Inc. Procede et appareil d'utilisation de techniques de melange d'hyperfrequences/rf pour selectionner une bande donnee d'une transmission optique

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0260745A1 (fr) * 1986-09-17 1988-03-23 Koninklijke Philips Electronics N.V. Dispositif de détection optique hétérodyne d'un signal optique et système de transmission optique muni d'un tel dispositif
US5896211A (en) * 1990-09-14 1999-04-20 Fujitsu Limited Optical communication system
EP0964237A1 (fr) * 1997-11-28 1999-12-15 Fujitsu Limited Procede de mesure de la dispersion en mode de polarisation, dispositif de commande de compensation de dispersion et procede de commande de compensation de dispersion
WO2000077956A1 (fr) * 1999-06-10 2000-12-21 Fiberspace, Inc. Procede et appareil d'utilisation de techniques de melange d'hyperfrequences/rf pour selectionner une bande donnee d'une transmission optique

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102253498A (zh) * 2010-05-18 2011-11-23 昂纳信息技术（深圳）有限公司 一种减小偏振模偏振的色散补偿器

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