Abstract

We present the principle of optical frequency modulation via the Doppler effect obtained by rapidly stretching an optical fiber and thus modifying the optical path of the light propagating in the fiber. This procedure creates a pure frequency shift, with no degradation of the spectrum. Moreover, the effect is wavelength independent and can therefore be applied to any type of light source. We show an experimental realization in which a frequency excursion of 100 MHz was obtained with a bobbin vibrating at 180  Hz.

© 1999 Optical Society of America

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References

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  1. B. Culshaw and J. Dakin, eds., Optical Fiber Sensors (Artech House, Norwood, Mass., 1996), Vol. 3.
  2. W. Eikhoff and R. Ulrich, Appl. Phys. Lett. 9, 693 (1991).
  3. L. Rovati, U. Minoni, and F. Docchio, Opt. Lett. 22, 850 (1997).
    [CrossRef] [PubMed]
  4. J. P. von der Weid, R. Passy, G. Mussi, and N. Gisin, J. Lightwave Technol. 15, 1131 (1997).
    [CrossRef]
  5. K. Tsuji, K. Shimizu, T. Horiguchi, and Y. Koyamada, IEEE Photon. Technol. Lett. 7, 804 (1995).
    [CrossRef]
  6. M. Martinelli, M. J. Marrone, and M. A. David, J. Mod. Opt. 39, 451 (1992).
    [CrossRef]
  7. D. E. N. Davies and S. Kingsley, Electron. Lett. 10, 21 (1974).
    [CrossRef]
  8. To understand this, let us denote by T the period of the mechanical vibration:?T=2?/?.?Because of Fourier relations, the uncertainty in the angular frequency measured during this time T is thus given by ??Fourier×T?1.?The time-domain approach of Eq.??(2) is valid only when the frequency shift is much larger than this uncertainty, which in turn requires that A?1.
  9. This quality factor ? depends on the coupling ratios of the couplers and on the polarization properties of the interferometer.

1997 (2)

J. P. von der Weid, R. Passy, G. Mussi, and N. Gisin, J. Lightwave Technol. 15, 1131 (1997).
[CrossRef]

L. Rovati, U. Minoni, and F. Docchio, Opt. Lett. 22, 850 (1997).
[CrossRef] [PubMed]

1995 (1)

K. Tsuji, K. Shimizu, T. Horiguchi, and Y. Koyamada, IEEE Photon. Technol. Lett. 7, 804 (1995).
[CrossRef]

1992 (1)

M. Martinelli, M. J. Marrone, and M. A. David, J. Mod. Opt. 39, 451 (1992).
[CrossRef]

1991 (1)

W. Eikhoff and R. Ulrich, Appl. Phys. Lett. 9, 693 (1991).

1974 (1)

D. E. N. Davies and S. Kingsley, Electron. Lett. 10, 21 (1974).
[CrossRef]

David, M. A.

M. Martinelli, M. J. Marrone, and M. A. David, J. Mod. Opt. 39, 451 (1992).
[CrossRef]

Davies, D. E. N.

D. E. N. Davies and S. Kingsley, Electron. Lett. 10, 21 (1974).
[CrossRef]

Docchio, F.

Eikhoff, W.

W. Eikhoff and R. Ulrich, Appl. Phys. Lett. 9, 693 (1991).

Gisin, N.

J. P. von der Weid, R. Passy, G. Mussi, and N. Gisin, J. Lightwave Technol. 15, 1131 (1997).
[CrossRef]

Horiguchi, T.

K. Tsuji, K. Shimizu, T. Horiguchi, and Y. Koyamada, IEEE Photon. Technol. Lett. 7, 804 (1995).
[CrossRef]

Kingsley, S.

D. E. N. Davies and S. Kingsley, Electron. Lett. 10, 21 (1974).
[CrossRef]

Koyamada, Y.

K. Tsuji, K. Shimizu, T. Horiguchi, and Y. Koyamada, IEEE Photon. Technol. Lett. 7, 804 (1995).
[CrossRef]

Marrone, M. J.

M. Martinelli, M. J. Marrone, and M. A. David, J. Mod. Opt. 39, 451 (1992).
[CrossRef]

Martinelli, M.

M. Martinelli, M. J. Marrone, and M. A. David, J. Mod. Opt. 39, 451 (1992).
[CrossRef]

Minoni, U.

Mussi, G.

J. P. von der Weid, R. Passy, G. Mussi, and N. Gisin, J. Lightwave Technol. 15, 1131 (1997).
[CrossRef]

Passy, R.

J. P. von der Weid, R. Passy, G. Mussi, and N. Gisin, J. Lightwave Technol. 15, 1131 (1997).
[CrossRef]

Rovati, L.

Shimizu, K.

K. Tsuji, K. Shimizu, T. Horiguchi, and Y. Koyamada, IEEE Photon. Technol. Lett. 7, 804 (1995).
[CrossRef]

Tsuji, K.

K. Tsuji, K. Shimizu, T. Horiguchi, and Y. Koyamada, IEEE Photon. Technol. Lett. 7, 804 (1995).
[CrossRef]

Ulrich, R.

W. Eikhoff and R. Ulrich, Appl. Phys. Lett. 9, 693 (1991).

von der Weid, J. P.

J. P. von der Weid, R. Passy, G. Mussi, and N. Gisin, J. Lightwave Technol. 15, 1131 (1997).
[CrossRef]

Appl. Phys. Lett. (1)

W. Eikhoff and R. Ulrich, Appl. Phys. Lett. 9, 693 (1991).

Electron. Lett. (1)

D. E. N. Davies and S. Kingsley, Electron. Lett. 10, 21 (1974).
[CrossRef]

IEEE Photon. Technol. Lett. (1)

K. Tsuji, K. Shimizu, T. Horiguchi, and Y. Koyamada, IEEE Photon. Technol. Lett. 7, 804 (1995).
[CrossRef]

J. Lightwave Technol. (1)

J. P. von der Weid, R. Passy, G. Mussi, and N. Gisin, J. Lightwave Technol. 15, 1131 (1997).
[CrossRef]

J. Mod. Opt. (1)

M. Martinelli, M. J. Marrone, and M. A. David, J. Mod. Opt. 39, 451 (1992).
[CrossRef]

Opt. Lett. (1)

Other (3)

To understand this, let us denote by T the period of the mechanical vibration:?T=2?/?.?Because of Fourier relations, the uncertainty in the angular frequency measured during this time T is thus given by ??Fourier×T?1.?The time-domain approach of Eq.??(2) is valid only when the frequency shift is much larger than this uncertainty, which in turn requires that A?1.

This quality factor ? depends on the coupling ratios of the couplers and on the polarization properties of the interferometer.

B. Culshaw and J. Dakin, eds., Optical Fiber Sensors (Artech House, Norwood, Mass., 1996), Vol. 3.

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Figures (4)

Fig. 1
Fig. 1

Principle of the Doppler-generated frequency shift. The source is made from a 1550-nm laser. Light is transmitted through a polarization beam splitter (PBS) and propagates along the stretched fiber. Because of the properties of the Faraday mirror,6 all the returning light is reflected at the PBS, toward the output fiber. The stretched fiber is suddenly released, which generates a time-dependent optical path length and a Doppler shift of the optical frequency. This frequency shift is measured by the detection system, made from an unbalanced Mach–Zehnder interferometer. PC is a personal computer.

Fig. 2
Fig. 2

Interferogram for a stretched fiber. Solid curve, the intensity at the detector (the average is normalized to 1) for the setup of Fig.  1. The stretched fiber is released at t=0; after 3.5 s it is completely slack, and the frequency remains constant for a while. The large noise after 4  s is caused by the crumbling of the fiber. Dashed curve, the theoretical fit [Eq.  (3)]. The only free parameter is the initial phase of the interferometer.

Fig. 3
Fig. 3

Interferogram for the vibrating bobbin. The bobbin oscillates at 180  Hz, with an amplitude of 0.36  mm, which corresponds to an elongation of the fiber of 0.14–0.86%. Solid curve, the normalized intensity at the detector once the dc component has been removed. The detection system is similar to the one in Fig.  1. The three points A–C represent the maximum velocity points and correspond to the extrema of the optical frequency.

Fig. 4
Fig. 4

Doppler-generated frequency shift for the bobbin. Filled circles, optical frequency shifts, as inferred from Fig.  3. They correspond to the intersection of the curve of Fig.  3 with the I=0 axis. They are all one-half fringe apart, corresponding to 5.12  MHz. Solid curve, a sinusoidal fit.

Equations (3)

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loptt=nl+ΔloptcosΩt,
νt=ν01-1cdloptdt=ν0+ΔloptλΩsinΩt,
It=1+αcos2πνtΔν,

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