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Reducing Modal And Reflection-Enhanced Intensity Noise in Multimode Waveguide Data Links

IP.com Disclosure Number: IPCOM000100221D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 1 page(s) / 40K

Publishing Venue

IBM

Related People

Bates, R: AUTHOR

Abstract

Disclosed are the bounds whereby modal [1] and reflection-enhanced intensity noise [2] in multimode waveguide data links may be reduced, by using a laser diode in the transmitter that is self-pulsating [3] and by having an appropriate amount of modal dispersion in the initial portion of the waveguide.

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Reducing Modal And Reflection-Enhanced Intensity Noise in Multimode Waveguide Data Links

       Disclosed are the bounds whereby modal [1] and
reflection-enhanced intensity noise [2] in multimode waveguide data
links may be reduced, by using a laser diode in the transmitter that
is self-pulsating [3] and by having an appropriate amount of modal
dispersion in the initial portion of the waveguide.

      To minimize the distance over which there is sensitivity to
modal noise and reflections, maximize:

                            (Image Omitted)

    Wf/f - the laser's optical frequency sweep during self-pulsation
-

      chirp
    Wv/v - the waveguide's differential mode velocity - dispersion
Note that, in addition, there are limits on the permissible
intermodal dispersion to avoid significant signal distortion,
operating at a bit rate B.

      Thus, operating at an optical wavelength g, the "useful" range
of waveguide lengths, Z, is:
                          g v_  f_ < Z < c  v_
                            Wv  Wf ~   ~ B  Wv

      A generalized embodiment of this approach requires the
self-pulsating laser to be followed by a linear dispersive medium and
then the regular guide, which may itself be dispersive; between the
two guides may be interposed some mode matching guide, should the
dispersive one support more than the regular, so as not to dissipate
energy.

 ...