WO2002088805A1 - Compensateur de dispersion chromatique - Google Patents

Compensateur de dispersion chromatique Download PDF

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Publication number
WO2002088805A1
WO2002088805A1 PCT/US2002/011622 US0211622W WO02088805A1 WO 2002088805 A1 WO2002088805 A1 WO 2002088805A1 US 0211622 W US0211622 W US 0211622W WO 02088805 A1 WO02088805 A1 WO 02088805A1
Authority
WO
WIPO (PCT)
Prior art keywords
optical
grating
chromatic dispersion
port
dispersion compensator
Prior art date
Application number
PCT/US2002/011622
Other languages
English (en)
Inventor
Daniel M. Boland
Glenn E. Kohnke
Original Assignee
Corning Incorporated
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 US09/942,286 external-priority patent/US6633704B2/en
Application filed by Corning Incorporated filed Critical Corning Incorporated
Publication of WO2002088805A1 publication Critical patent/WO2002088805A1/fr

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29304—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating
    • G02B6/29316—Light guides comprising a diffractive element, e.g. grating in or on the light guide such that diffracted light is confined in the light guide
    • G02B6/29317—Light guides of the optical fibre type
    • G02B6/29319—With a cascade of diffractive elements or of diffraction operations
    • G02B6/2932—With a cascade of diffractive elements or of diffraction operations comprising a directional router, e.g. directional coupler, circulator
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
    • G02B6/29392—Controlling dispersion
    • G02B6/29394—Compensating wavelength dispersion

Definitions

  • the present invention relates generally to chromatic dispersion compensation, and particularly to polarization mode dispersion compensation for chirped fiber gratings.
  • D( ⁇ c ) is the dispersion (second order); and D'( ⁇ c ) is the dispersion slope (third order) or S.
  • One approach to dispersion compensation in optical communication systems is to intersperse sections of dispersion compensating optical waveguide fiber between segments of transmission of optical fiber. Some factors that influence the performance and design of dispersion compensation modules include; changing traffic patterns, variations in the optical power of the optical signals, temperature fluctuations along the length of the optical fiber waveguides, installation effects on the cable, modulation format, channel spacing and irregularities with the optical waveguide fiber. Because the magnitude of dispersion in optical communication systems may change, dispersion compensation using dispersion compensating fiber will not be optimal for every channel and a tunable dispersion compensation is required.
  • Dispersion may be compensated for dynamically during the operation of the optical communication system in order to minimize time-dependent effects such as, for example, the variation in the dispersion characteristics of optical waveguide fibers resulting from fluctuations in temperature.
  • One proposed approach for dispersion compensation uses fiber Bragg gratings as tunable dispersion compensators for a single channel.
  • a single non-linearly chirped fiber Bragg grating is strained to vary the dispersion within . the band of wavelengths of interest.
  • Another proposed configuration uses temperature to shift the wavelength of the entire dispersion curve.
  • This approach to dispersion compensation introduces some amount of dispersion slope across the passband.
  • the thermally tuned configuration dynamically alters the amount of chirp along the length of the grating.
  • the thermally tuned configurations proposed thus far require complex tuning mechanisms to control the dispersion compensation as well as requiring a second tuning mechanism to maintain a constant grating center wavelength. Thus there is a need for a less complex, tunable dispersion compensator for optical communication systems.
  • Polarization mode dispersion is the maximum difference of group delay as a function of polarization for an optical component.
  • polarization mode dispersion is a deterministic quantity and is the difference in group delay between the two principal states of polarization.
  • group delay is a linear function of wavelength and the polarization mode dispersion is simply related to the birefringence of the fiber in the grating region by:
  • Equation (2) may also be written as: where -
  • PMD is the polarization mode dispersion
  • CD is the chromatic dispersion
  • An is the effective group index difference
  • A is the grating period.
  • the magnitude of polarization mode dispersion in linearly chirped fiber Bragg gratings reportedly ranges between about 0.25 picoseconds and about 8 picoseconds.
  • Polarization mode dispersion compensation requirements for optical communication systems may be less than 1 picosecond.
  • Figure 1 shows one proposed approach to polarization mode dispersion compensation for a single linearly chirped fiber Bragg grating.
  • the approach uses a 3- port optical circulator 10.
  • An optical circulator is a non-reciprocating device that transports an optical signal from one port to the next port, only one direction (i.e. 1 to 2, or 2 to 3). They are used to separate forward and backward propagating signals.
  • An optical signal is received by the first port 12 of the optical circulator 10.
  • the optical circulator 10 directs the optical signal received by the first port 12 to the optical circulator's 10 second port 14.
  • the optical signal propagates toward a fiber Bragg grating 16.
  • the fiber Bragg grating 16 reflects at least a portion of the optical signal back into the second port 14.
  • the optical circulator 10 directs the reflected optical signal to the third port 18 of the optical circulator 10.
  • the optical signal exits the third port 18 of the optical circulator 10 and is directed through a ⁇ /2 waveplate 20 before entering a polarization maintaining fiber 22.
  • the polarization maintaining fiber 22 is connected to a transmission optical waveguide fiber 24.
  • the ⁇ /2 waveplate 20 in combination with the polarization maintaining fiber 22 compensate for the polarization mode dispersion in the single grating 16.
  • Figure 2 shows another proposed approach to polarization mode dispersion compensation for a single linearly chirped fiber Bragg grating.
  • This approach also uses a three port optical circulator 10.
  • An optical signal is received by the first port 12 of the optical circulator 10.
  • the optical circulator 10 directs the optical signal received by the first port 12 to the optical circulator's 10 second port 14.
  • One end of a polarization maintaining fiber 22 is optically coupled to the second port 14.
  • the other end of the polarization maintaining fiber 22 is optically coupled to a fiber Bragg grating 16.
  • the optical signal propagates through the polarization maintaining fiber 22 before at least a portion of the optical signal is reflected by the fiber Bragg grating 16.
  • the reflected optical signal propagates back through the polarization maintaining fiber 22 and is introduced into the second port 14 of the optical circulator 10.
  • the optical circulator 10 directs the reflected optical signal out of the third port 18.
  • the third port 18 is optically coupled to an optical waveguide fiber 24.
  • Pulse broadening induced by polarization mode dispersion is important in chirped
  • the chromatic dispersion compensator includes a first optical circulator.
  • the first optical circulator has a first optical port; a second optical port; and a third optical port.
  • the chromatic dispersion compensator further includes a first grating coupled to the second optical port.
  • a polarization controller is coupled to the third optical port.
  • the chromatic dispersion compensator further includes a second optical circulator.
  • the second optical circulator has a fourth optical port coupled to the polarization controller; a fifth optical port; and a sixth optical port.
  • the chromatic dispersion compensator also includes a second grating coupled to the fifth optical port.
  • Figure 1 is a schematic diagram of a prior art chromatic dispersion compensating device
  • Figure 2 is a schematic diagram of a prior art chromatic dispersion compensating device
  • Figure 3 is a schematic diagram of a chromatic dispersion compensator.
  • the chromatic dispersion compensator 26 of the present invention includes a first optical circulator 28 and a second optical circulator 30.
  • the first optical circulator 28 includes three ports 32, 34, 36.
  • the second optical circulator 30 also includes three ports 38, 40, 42.
  • Three port optical circulators are available commercially, such as, for example the 3-port optical circulators sold by New Focus, Inc. of San Jose, California.
  • the first port 32 of the first optical circulator 28 is optically coupled to an optical waveguide 44.
  • the optical waveguide 44 may be an optical waveguide fiber or a lightwave optical circuit.
  • the first port 32 receives an optical signal from the optical waveguide 44.
  • the optical signal is made up of light having multiple wavelengths.
  • the first optical circulator 28 directs the optical signal to its second port 34.
  • the second port 34 of the optical circulator 28 is coupled to a first grating 46, such as, for example, a nonlinearly chirped fiber Bragg grating. At least a portion of the optical signal is reflected back into the second port 34 by the grating 46.
  • the first optical circulator 28 directs the reflected optical signal from the second port 34 to the third port 36.
  • the third port 36 of the first optical circulator 28 is optically coupled to the first port 38 of the second optical circulator 30. This optical coupling may be accomplished using an optical waveguide 48.
  • a polarization controller 50 is disposed to act on an optical signal traveling from the third port 36 of the first optical circulator 28 to the first port 38 of the second optical circulator 30.
  • the polarization controller 50 acts on the optical signal in such a manner so as to make the principle states of polarization of the first and second gratings 46, 42 appear orthogonal to one anther. In this way the polarization mode dispersion of the second grating 52 cancels out the polarization mode dispersion of the first grating 46.
  • the polarization controller 50 may be, for example, an in-line polarization controller available from FiberPro of South Korea, or a miniature polarization controller available from Taliescent of Arlington, Arizona.
  • the waveguide 48 coupling the third port 36 of the first optical circulator 28 to the first port 38 of the second optical circulator 30 is made up of two optical waveguide fibers.
  • the two optical waveguide fibers are typically the optical fiber pigtails of the first and second optical circulators 28, 30.
  • the polarization state of the optical signal is modified by, aligning the pigtails and rotating them about their respective optical axes relative to one another until the principle states of polarization of the first and second gratings 46, 52 appear orthogonal to one another to the optical signal.
  • the polarization controler In an alternative embodiment of the present invention, the polarization controler
  • the chromatic dispersion compensator 26 of the present invention may also compensate the polarization mode dispersion of the optical signal received by the first port 32 of the first optical circulator 28.
  • a second grating 52 such as, for example, a nonlinearly chirped fiber Bragg grating is optically coupled to the second port 40 of the second optical circulator 30.
  • the second grating 52 is substantially identical to the first grating 46.
  • the second grating 52 is coupled to the second port 40 such that the orientation of the second grating 52 is reversed with respect to the second port 40 from the orientation of the first grating 46 with respect to the second port 34 of the first optical circulator 28. That is to say, as seen by an optical signal, the variation in Bragg wavelength as a function of length along the grating of the second grating 52 is substantially inverse to the variation in Bragg wavelength as a function of length along the grating of the first grating 46.
  • the second grating 52 reflects the optical signal previously reflected by the first grating 46. This second reflection completes the chromatic dispersion compensation of the reflected optical signal.
  • the chromatic dispersion compensated optical signal re-enters the second circulator 30 through the second port 40.
  • the reflected optical signal is directed to the third port 42 from which it exits the second optical circulator 30.
  • the third port 42 of the second optical circulator 30 is optically coupled to an optical waveguide 54.
  • the chromatic dispersion compensated optical signal propagates along the optical waveguide 54 to its destination.
  • the first and second gratings 46, 52 may be tunable gratings, such as, for example thermally tunable, non-linearly chirped fiber Bragg gratings.
  • the first and second gratings 46, 52 may have either linear or nonlinear dispersion compensation slopes.
  • the gratings 46, 52 have an operational optical bandwidth of about 2 nanometers of which only about 0.5 nanometers is used. By only using a portion of the potential operational bandwidth of the gratings 46, 52 the center wavelength of the gratings 46, 52 may be adjusted to precisely match that of the optical signal that the chromatic dispersion compensator 26 is modifying.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Communication System (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Abstract

L'invention porte sur un compensateur de dispersion chromatique. Ce compensateur (26) comprend un premier circulateur optique à trois ports (28), un premier réseau (46) relié au second port optique du premier circulateur optique à trois ports (28). Un contrôleur de polarisation (50) est relié au troisième port optique du premier circulateur optique à trois ports. Le compensateur de dispersion chromatique (26) comporte également un second circulateur optique à trois ports (30), le contrôleur de polarisation (50) étant couplé au premier port optique du second circulateur optique à trois ports et un second réseau (52) étant couplé au second port optique du second circulateur optique à trois ports (30).
PCT/US2002/011622 2001-04-30 2002-04-10 Compensateur de dispersion chromatique WO2002088805A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US20743901P 2001-04-30 2001-04-30
US60/207,439 2001-04-30
US09/942,286 US6633704B2 (en) 2001-04-30 2001-08-29 Chromatic dispersion compensator
US09/942,286 2001-08-29

Publications (1)

Publication Number Publication Date
WO2002088805A1 true WO2002088805A1 (fr) 2002-11-07

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2002/011622 WO2002088805A1 (fr) 2001-04-30 2002-04-10 Compensateur de dispersion chromatique

Country Status (1)

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WO (1) WO2002088805A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5920413A (en) * 1996-04-05 1999-07-06 Kokusai Denshin Denwa Kabushiki-Kaisha Method and device for optical add/drop multiplexing using high speed polarization scrambler
US6388785B2 (en) * 2000-02-08 2002-05-14 University Of Southern California Optical compensation for dispersion-induced power fading in optical transmission of double-sideband signals
US6400869B2 (en) * 1999-12-03 2002-06-04 University Of Southern California Tunable compensation for polarization-mode dispersion using a birefringent nonlinearly-chirped bragg grating in a dual-pass configuration

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5920413A (en) * 1996-04-05 1999-07-06 Kokusai Denshin Denwa Kabushiki-Kaisha Method and device for optical add/drop multiplexing using high speed polarization scrambler
US6400869B2 (en) * 1999-12-03 2002-06-04 University Of Southern California Tunable compensation for polarization-mode dispersion using a birefringent nonlinearly-chirped bragg grating in a dual-pass configuration
US6388785B2 (en) * 2000-02-08 2002-05-14 University Of Southern California Optical compensation for dispersion-induced power fading in optical transmission of double-sideband signals

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