Crosstalk in wdm systems
1 / 11

Crosstalk in WDM Systems - PowerPoint PPT Presentation

  • Uploaded on

Crosstalk in WDM Systems. Paul G. Eitner ECEE-641 6 March 2003. Wavelength Division Multiplexing. Several wavelengths on single fiber Handles multiples of single wavelength data rate All wavelengths share single optical amplifier at given point along fiber Enables wavelength routing

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about ' Crosstalk in WDM Systems' - slone

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Crosstalk in wdm systems

Crosstalk in WDM Systems

Paul G. Eitner


6 March 2003

Wavelength division multiplexing
Wavelength Division Multiplexing

  • Several wavelengths on single fiber

    • Handles multiples of single wavelength data rate

    • All wavelengths share single optical amplifier at given point along fiber

    • Enables wavelength routing

  • WDM network components

    • Combiners

    • Splitters

    • Filters

    • Switches



Wdm crosstalk
WDM Crosstalk Union

  • Crosstalk if not removed results in unwanted signal at detector for channel l1

    • Induced by one or more of the other wavelengths

    • Or, mixing of channels with same wavelength due to leaks in network components (may include multipath)


Examples Union

  • Sources in fiber

    • Four-wave mixing

    • Cross-phase modulation

    • Stimulated Raman scattering (constrains power)

    • Stimulated Brilluoin scattering (constrains l-spacing)

  • Device effects

    • Imperfect channel separation at splitting nodes

    • Imperfect filtering

  • Fiber effects are non-linear often in response to total power as opposed to power at single wavelength

    • Constrains power along entire fiber length


Crosstalk in wdm switch
Crosstalk in WDM Switch Union

R1, G1, B1

R2, G2, B2

R3, G3, B3

R1, G2+DG1, B3

  • Imperfect separation of R1 and G1 at input demux

  • means G1 mixes with G2 on output

  • Can’t be removed by spectral filter if lG1 = lG2


Four wave mixing
Four-Wave Mixing Union

  • Four-wave mixing: spurious signal at a nearby frequency, generated in response to refractive index nonlinearity

    • nFWM = n1 + n2 - n3

    • nFWM = 2n1 – n2 (degenerate case)

  • Reduces power in desired channel and introduces crosstalk at other frequencies

  • Most efficient when n1iszero-dispersion wavelength in fiber

  • Mitigation options include

    • Unequal wavelength spacing

    • Wider wavelength spacing

    • Trade off dispersion using non-zero dispersion-shifted fiber


Fwm mitigation with nzdsf reference 3

FWM Union


FWM Mitigation with NZDSF(Reference 3)

  • 8 channels at 10 Gbps transmitted through 360 km of NZDS single-mode fiber

  • Channels separated by 200 GHz (~1.6 nm)

  • Fiber dispersion approx –3.5 ps/km-nm is large enough to minimize FWM but small enough to support 10 Gbps over long distances


Summary Union

  • Crosstalk causes fundamental limitations on transmit power and distance-bandwidth product on WDM networks

    • Can be present in a single fiber link

    • Also arises due to imperfections in network components

  • Fiber and optical components can be optimized to minimize effects

  • FWM mitigated by non-zero dispersion-shifted fiber

    • Fiber for use in DWDM systems may not be optimized by minimizing dispersion and attenuation alone


References Union

  • G. P. Agrawal, Fiber-Optic Communication Systems, 2nd Edition, Wiley-Interscience, 1997.

  • ITU-T Recommendations G.694.1 and G.694.2, June 2002.

  • M. Yadlowsky, E. DeLiso, and V. da Silva, “Optical Fibers and Amplifiers for WDM Systems”, Proc. IEEE 85(11), 1997.

  • M. J. O’Mahony, “Optical Multiplexing in Fiber Networks: Progress in WDM and OTDM”, IEEE Communications Magazine, December 1995.


Questions Union

  • What wavelength spacing does a DWDM frequency spacing of 50 GHz translate to at 1.55 microns?

  • Name three methods of reducing four-wave mixing

  • Name two network components (besides fiber) that can cause (or allow) crosstalk

  • Name two advantages of WDM

  • Sketch how crosstalk can occur in a WDM switch