Abstract

When polarized light is incident upon a long multimode fiber, the emerging light is randomly distributed among the spatial and polarization modes. We present experimental and theoretical results demonstrating that recovery of the spatial and polarization modes of the incident light takes place only when a phase conjugator at the fiber output preserves polarization on reflection.

© 1987 Optical Society of America

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References

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  1. I. McMichael, M. Khoshnevisan, in Digest of the Conference on Lasers and Electro-Optics (Optical Society of America, Washington, D.C., 1985), paper THN1, p. 220.
  2. I. McMichael, M. Khoshnevisan, P. Yeh, Opt. Lett. 11, 525 (1986).
    [CrossRef] [PubMed]
  3. P. Yeh, Opt. Commun. 51, 195 (1984).
    [CrossRef]
  4. K. Kyuma, A. Yariv, S. Kwong, Appl. Phys. Lett. 49, 617 (1986).
    [CrossRef]
  5. A. Yariv, Y. Tomita, K. Kyuma, Opt. Lett. 11, 809 (1986).
    [CrossRef] [PubMed]
  6. P. D. Drummond, A. T. Friberg, J. Appl. Phys. 54, 5618 (1983).
    [CrossRef]

1986 (3)

1984 (1)

P. Yeh, Opt. Commun. 51, 195 (1984).
[CrossRef]

1983 (1)

P. D. Drummond, A. T. Friberg, J. Appl. Phys. 54, 5618 (1983).
[CrossRef]

Drummond, P. D.

P. D. Drummond, A. T. Friberg, J. Appl. Phys. 54, 5618 (1983).
[CrossRef]

Friberg, A. T.

P. D. Drummond, A. T. Friberg, J. Appl. Phys. 54, 5618 (1983).
[CrossRef]

Khoshnevisan, M.

I. McMichael, M. Khoshnevisan, P. Yeh, Opt. Lett. 11, 525 (1986).
[CrossRef] [PubMed]

I. McMichael, M. Khoshnevisan, in Digest of the Conference on Lasers and Electro-Optics (Optical Society of America, Washington, D.C., 1985), paper THN1, p. 220.

Kwong, S.

K. Kyuma, A. Yariv, S. Kwong, Appl. Phys. Lett. 49, 617 (1986).
[CrossRef]

Kyuma, K.

K. Kyuma, A. Yariv, S. Kwong, Appl. Phys. Lett. 49, 617 (1986).
[CrossRef]

A. Yariv, Y. Tomita, K. Kyuma, Opt. Lett. 11, 809 (1986).
[CrossRef] [PubMed]

McMichael, I.

I. McMichael, M. Khoshnevisan, P. Yeh, Opt. Lett. 11, 525 (1986).
[CrossRef] [PubMed]

I. McMichael, M. Khoshnevisan, in Digest of the Conference on Lasers and Electro-Optics (Optical Society of America, Washington, D.C., 1985), paper THN1, p. 220.

Tomita, Y.

Yariv, A.

A. Yariv, Y. Tomita, K. Kyuma, Opt. Lett. 11, 809 (1986).
[CrossRef] [PubMed]

K. Kyuma, A. Yariv, S. Kwong, Appl. Phys. Lett. 49, 617 (1986).
[CrossRef]

Yeh, P.

Appl. Phys. Lett. (1)

K. Kyuma, A. Yariv, S. Kwong, Appl. Phys. Lett. 49, 617 (1986).
[CrossRef]

J. Appl. Phys. (1)

P. D. Drummond, A. T. Friberg, J. Appl. Phys. 54, 5618 (1983).
[CrossRef]

Opt. Commun. (1)

P. Yeh, Opt. Commun. 51, 195 (1984).
[CrossRef]

Opt. Lett. (2)

Other (1)

I. McMichael, M. Khoshnevisan, in Digest of the Conference on Lasers and Electro-Optics (Optical Society of America, Washington, D.C., 1985), paper THN1, p. 220.

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Figures (3)

Fig. 1
Fig. 1

Illustration of what happens when light propagates in a multimode fiber (MMF) and only one polarization component is conjugated at its output. The top section shows a sketch of the optics, and (a)–(c) show the evolution of the polarization of the light as it propagates. The field E I = x ˆ enters the MMF at z = 0. (a) Because of modal scrambling, the output field EII is equally distributed among the x and y polarizations and the change in polarization is represented by rotation of EI to EII. (b) The x component of EII passes through the polarizer and reflects from the phase-conjugate mirror PCM to produce E III = E II x * x ˆ. This field has a phase-conjugate component, ½EII*, and an orthogonal component, ½EII* . (c) When the conjugate component propagates back to z = 0 it generates ½EI* by time reversal (depicted as rotation of ½EII* to ½EI*), and the orthogonal component generates ½EI* , where EI* is orthogonal to EI*. Because of modal scrambling, EI* is distributed equally among the x and y polarizations. Note that only one fourth of the energy is recovered in the reconstruction of the input field. The other one fourth is randomly distributed among the spatial and polarization modes. One half of the energy is lost at the polarizer.

Fig. 2
Fig. 2

Experimental setup. Light emerging from the multimode fiber MMF is reflected from the PPPC formed by the optical elements PBS, M1–M4, λ/2, and the BaTiO3 crystal. The effect of conjugating only one polarization component can be observed by blocking one of the outputs from the polarizing beam splitter PBS. After propagating back through the fiber, the light is sampled by beam splitter BS, analyzed by the polarizer P, and measured by detector D or photographed.

Fig. 3
Fig. 3

Photographs of the returning light as seen at the position of detector D in Fig. 2. ∥ corresponds to the polarization of the light incident upon the fiber. The first set of photos was taken with the phase-conjugate mirror blocked, the second set of photos with the PPPC at the fiber end, and the third set of photos with the NPPPC (one of the outputs from the polarizing beam splitter in Fig. 2 is blocked). For the PPPC all the light returns as the phase conjugate (bright spot in the photo of ∥ polarization). However, for the NPPPC only one half of the returning light is the phase conjugate; the other half is randomly distributed among the spatial and polarization modes.

Tables (1)

Tables Icon

Table 1 Measured and Predicted Power Ratios for Phase-Conjugation with Multimode Fibersa

Equations (8)

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E n ( x , y ) exp ( i β n z ) , n = 1 , 2 , , N ,
E I = n A n E n ,
E II = ( E II x , E IIy ) ,
| E II x | 2 d x d y = | E II y | 2 d x d y .
E III = ( E II x * , 0 ) .
E III = a E II * + b E II * ,
E III = 1 / 2 E II * + 1 / 2 E II * .
E IV = 1 / 2 E I * + 1 / 2 E I * .

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