Abstract

Single-mode fibers have been proposed for connecting telescopes to mixing stations in coherent telescope arrays intended for image synthesis. We describe a laser-controlled servosystem that keeps the fiber-optical length differences stable and permits passage of wide-bandwidth astronomical beams from an unlimited number of telescopes. Initial laboratory results are presented.

© 1992 Optical Society of America

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References

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  1. A. Labeyrie, “Interference fringes obtained on Vega with two optical telescopes,” Astrophys. J. 196, L71–75 (1975).
    [Crossref]
  2. A. Labeyrie, “Stellar interferometry methods,” Annual Review of Astronomy and Astrophysics, G. Burbidge, ed. (Annual Reviews, Palo Alto, Calif., 1978), Chap. 16, pp. 77–102.
    [Crossref]
  3. F. Merkle, ed., High-Resolution Imaging by Interferometry (European Southern Observatory. Garching bei München, Germany, 1988). These proceedings contain numerous papers on existing and future long-baseline interferometers.
  4. C. Froehly, “High angular resolution,” in Coherence and Interferometry through Optical Fibers, proceedings of the Conference on the Scientific Importance of High Angular Resolution at IR and Optical Wavelengths (European Southern Observatory, Garching bei München, Germany, 1981), p. 285.
  5. P. Connes, C. Froehly, P. Facq, “A fiber linked version of project Trio,” in Proceedings of the ESA Colloquium, Kilometric Optical Arrays in Space, N. Longdon, O. Melita, eds. (European Space Agency, Nordwijk, The Netherlands, 1984), p.49.
  6. P. Connes, F. Roddier, S. Shaklan, “A fiber-linked ground-based array,” in ESO–NOAO Oracle Workshop, J. W. Goad, ed. (National Optical Astronomy Observatories, Tucson, Ariz., 1987), p. 165.
  7. P. Connes, F. Roddier, S. Shaklan, E. Riback, “Fiber linked telescope arrays on the ground and in space,” in ESA Workshop on Optical Interferometry in Space, N. Longdon, V. David, eds. (European Space Agency; Nordwijk, The Netherlands, 1987), p. 273.
  8. S. Shaklan, F. Roddier, “Single-mode fiber optics in a long-baseline interferometer,” Appl. Opt. 26, 2159–2163 (1987).
    [Crossref] [PubMed]
  9. T. Muscha, J. Kamimura, M. Nakazawa, “Optical phase fluctuations thermally induced in a single-mode optical fiber,” Appl. Opt. 21, 694–698 (1982).
    [Crossref]
  10. G. B. Hocker, “Fiber optic sensing of pressure and temperature,” App. Opt. 18, 1445 (1979).
    [Crossref]
  11. P. Connes, F. Reynaud, “Fiber tests on a radiotelescope,” in Proceedings of the NOAO-ESO Conference on High-Resolution Imaging by Interferometry, F. Merkle, ed. (European Southern Observatory, Garching bei München, Germany, 1988), pp. 1117–1129.

1987 (1)

1982 (1)

1979 (1)

G. B. Hocker, “Fiber optic sensing of pressure and temperature,” App. Opt. 18, 1445 (1979).
[Crossref]

1975 (1)

A. Labeyrie, “Interference fringes obtained on Vega with two optical telescopes,” Astrophys. J. 196, L71–75 (1975).
[Crossref]

Connes, P.

P. Connes, C. Froehly, P. Facq, “A fiber linked version of project Trio,” in Proceedings of the ESA Colloquium, Kilometric Optical Arrays in Space, N. Longdon, O. Melita, eds. (European Space Agency, Nordwijk, The Netherlands, 1984), p.49.

P. Connes, F. Roddier, S. Shaklan, “A fiber-linked ground-based array,” in ESO–NOAO Oracle Workshop, J. W. Goad, ed. (National Optical Astronomy Observatories, Tucson, Ariz., 1987), p. 165.

P. Connes, F. Roddier, S. Shaklan, E. Riback, “Fiber linked telescope arrays on the ground and in space,” in ESA Workshop on Optical Interferometry in Space, N. Longdon, V. David, eds. (European Space Agency; Nordwijk, The Netherlands, 1987), p. 273.

P. Connes, F. Reynaud, “Fiber tests on a radiotelescope,” in Proceedings of the NOAO-ESO Conference on High-Resolution Imaging by Interferometry, F. Merkle, ed. (European Southern Observatory, Garching bei München, Germany, 1988), pp. 1117–1129.

Facq, P.

P. Connes, C. Froehly, P. Facq, “A fiber linked version of project Trio,” in Proceedings of the ESA Colloquium, Kilometric Optical Arrays in Space, N. Longdon, O. Melita, eds. (European Space Agency, Nordwijk, The Netherlands, 1984), p.49.

Froehly, C.

C. Froehly, “High angular resolution,” in Coherence and Interferometry through Optical Fibers, proceedings of the Conference on the Scientific Importance of High Angular Resolution at IR and Optical Wavelengths (European Southern Observatory, Garching bei München, Germany, 1981), p. 285.

P. Connes, C. Froehly, P. Facq, “A fiber linked version of project Trio,” in Proceedings of the ESA Colloquium, Kilometric Optical Arrays in Space, N. Longdon, O. Melita, eds. (European Space Agency, Nordwijk, The Netherlands, 1984), p.49.

Hocker, G. B.

G. B. Hocker, “Fiber optic sensing of pressure and temperature,” App. Opt. 18, 1445 (1979).
[Crossref]

Kamimura, J.

Labeyrie, A.

A. Labeyrie, “Interference fringes obtained on Vega with two optical telescopes,” Astrophys. J. 196, L71–75 (1975).
[Crossref]

A. Labeyrie, “Stellar interferometry methods,” Annual Review of Astronomy and Astrophysics, G. Burbidge, ed. (Annual Reviews, Palo Alto, Calif., 1978), Chap. 16, pp. 77–102.
[Crossref]

Muscha, T.

Nakazawa, M.

Reynaud, F.

P. Connes, F. Reynaud, “Fiber tests on a radiotelescope,” in Proceedings of the NOAO-ESO Conference on High-Resolution Imaging by Interferometry, F. Merkle, ed. (European Southern Observatory, Garching bei München, Germany, 1988), pp. 1117–1129.

Riback, E.

P. Connes, F. Roddier, S. Shaklan, E. Riback, “Fiber linked telescope arrays on the ground and in space,” in ESA Workshop on Optical Interferometry in Space, N. Longdon, V. David, eds. (European Space Agency; Nordwijk, The Netherlands, 1987), p. 273.

Roddier, F.

S. Shaklan, F. Roddier, “Single-mode fiber optics in a long-baseline interferometer,” Appl. Opt. 26, 2159–2163 (1987).
[Crossref] [PubMed]

P. Connes, F. Roddier, S. Shaklan, E. Riback, “Fiber linked telescope arrays on the ground and in space,” in ESA Workshop on Optical Interferometry in Space, N. Longdon, V. David, eds. (European Space Agency; Nordwijk, The Netherlands, 1987), p. 273.

P. Connes, F. Roddier, S. Shaklan, “A fiber-linked ground-based array,” in ESO–NOAO Oracle Workshop, J. W. Goad, ed. (National Optical Astronomy Observatories, Tucson, Ariz., 1987), p. 165.

Shaklan, S.

S. Shaklan, F. Roddier, “Single-mode fiber optics in a long-baseline interferometer,” Appl. Opt. 26, 2159–2163 (1987).
[Crossref] [PubMed]

P. Connes, F. Roddier, S. Shaklan, E. Riback, “Fiber linked telescope arrays on the ground and in space,” in ESA Workshop on Optical Interferometry in Space, N. Longdon, V. David, eds. (European Space Agency; Nordwijk, The Netherlands, 1987), p. 273.

P. Connes, F. Roddier, S. Shaklan, “A fiber-linked ground-based array,” in ESO–NOAO Oracle Workshop, J. W. Goad, ed. (National Optical Astronomy Observatories, Tucson, Ariz., 1987), p. 165.

App. Opt. (1)

G. B. Hocker, “Fiber optic sensing of pressure and temperature,” App. Opt. 18, 1445 (1979).
[Crossref]

Appl. Opt. (2)

Astrophys. J. (1)

A. Labeyrie, “Interference fringes obtained on Vega with two optical telescopes,” Astrophys. J. 196, L71–75 (1975).
[Crossref]

Other (7)

A. Labeyrie, “Stellar interferometry methods,” Annual Review of Astronomy and Astrophysics, G. Burbidge, ed. (Annual Reviews, Palo Alto, Calif., 1978), Chap. 16, pp. 77–102.
[Crossref]

F. Merkle, ed., High-Resolution Imaging by Interferometry (European Southern Observatory. Garching bei München, Germany, 1988). These proceedings contain numerous papers on existing and future long-baseline interferometers.

C. Froehly, “High angular resolution,” in Coherence and Interferometry through Optical Fibers, proceedings of the Conference on the Scientific Importance of High Angular Resolution at IR and Optical Wavelengths (European Southern Observatory, Garching bei München, Germany, 1981), p. 285.

P. Connes, C. Froehly, P. Facq, “A fiber linked version of project Trio,” in Proceedings of the ESA Colloquium, Kilometric Optical Arrays in Space, N. Longdon, O. Melita, eds. (European Space Agency, Nordwijk, The Netherlands, 1984), p.49.

P. Connes, F. Roddier, S. Shaklan, “A fiber-linked ground-based array,” in ESO–NOAO Oracle Workshop, J. W. Goad, ed. (National Optical Astronomy Observatories, Tucson, Ariz., 1987), p. 165.

P. Connes, F. Roddier, S. Shaklan, E. Riback, “Fiber linked telescope arrays on the ground and in space,” in ESA Workshop on Optical Interferometry in Space, N. Longdon, V. David, eds. (European Space Agency; Nordwijk, The Netherlands, 1987), p. 273.

P. Connes, F. Reynaud, “Fiber tests on a radiotelescope,” in Proceedings of the NOAO-ESO Conference on High-Resolution Imaging by Interferometry, F. Merkle, ed. (European Southern Observatory, Garching bei München, Germany, 1988), pp. 1117–1129.

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Figures (10)

Fig. 1
Fig. 1

Fiber-linked array mounted on a radio telescope. The N small telescopes at the left provide the same angular resolution as the single mirror on the right. However, the number of available photons is much smaller.

Fig. 2
Fig. 2

Interferometer overall diagram. The telescopes will be located on separate mounts. The laser and the master fiber are on the laboratory table; the astronomical-fringe mixing system may be added later.

Fig. 3
Fig. 3

Optical system at the slave-fiber astronomical input. The astronomical beam from the telescope (λ > 580 nm) is split in two parts by dichroic mirror D12; one goes to the fiber, another to the autoguider detector. The laser beam (λ < 580 nm) is twice reflected and returned to the fiber.

Fig. 4
Fig. 4

Servosystem block diagram for one arm: PH, uncooled Si photodiode; A, low-noise optical amplifier; SD, synchronous demodulator; OSC, 30–50-kHz oscillator; HT, ±150-V amplifier; PID, proportional integrator–derivator filter. The test input was used to feed a perturbing square wave and produce the photograph in Fig. 9.

Fig. 5
Fig. 5

Overall view of the laboratory table: la, laser; iso, Faraday isolator; mf, master fiber; bs’s, beam splitters; f1, f2, slave-fiber outputs.

Fig. 6
Fig. 6

Overall view of the two slave-fiber astronomical inputs (located side by side on a separate table): d21, d22, dichroic mirrors; f1, f2 fiber inputs; pzt22, one mirror-carrying piezoelectric transducer.

Fig. 7
Fig. 7

Phase shift versus frequency in a two-fiber interferometer. Air-path difference contributes φ1 and fiber-length difference contributes φ2.

Fig. 8
Fig. 8

High-pressure Xe-lamp spectrum as seen at the output of the Mach–Zehnder interferometer. The dotted curves are the fringes averaged out by fast scanning. The solid curves are the actual channeled spectra. (a) X axis, first observation from roughly cut fibers. The central fringe base width is ~ 50 nm, indicating an ~ 2-mm-length difference. (b) Same X axis after polishing. The central fringe base width is enlarged to 200 nm. (c) Y axis with the same interferometer adjustment as (b). The central fringe has moved out. (d) Same Y axis after a 20-fringe shift has been introduced; the central fringe has been recovered.

Fig. 9
Fig. 9

Fringe stabilization as seen by a pen recorder with a 0.5-s response time. With the servo off, fringes are scanned simply by letting the fiber temperatures drift.

Fig. 10
Fig. 10

Servo response excited by a perturbing step function.

Equations (4)

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Δ φ 1 = 2 π Δ L 1 L b .
V 1 = cos ( Δ φ 1 2 ) = cos ( π Δ L 1 L b ) .
Δ φ 3 = ( 2 β ω 2 ) ( ω - ω 0 ) 2 2 Δ L 3 ,
Δ L 3 = 2 π ( Δ ω ) 2 ( 2 β / ω 2 ) ,

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