Abstract

We describe a new type of optical reflectometry which is useful in testing single-mode lightguide systems. This technique uses a scanning Michelson interferometer in conjunction with a broadband illuminating source and cross-correlation detection. High resolution is achieved through the limited coherence of the backscattered radiation. With this approach it is possible to distinguish scattering centers separated by only a few micrometers. In some cases loss may be estimated for components in the transmission path of a test lightguide. The basic principles of this diagnostic technique, along with some performance characteristics, are illustrated for an all-fiber reflectometer. We also discuss several laboratory applications which serve to demonstrate the resolution capabilities of this measurement concept.

© 1987 Optical Society of America

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References

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  1. M. K. Barnoski, M. D. Rourke, S. M. Jensen, R. T. Melville, “Optical Time Domain Reflectometer,” Appl. Opt. 16, 2375 (1977).
    [CrossRef] [PubMed]
  2. S. D. Personick, “Photon Probe—an Optical Time-Domain Reflectometer,” Bell Syst. Tech. J. 56, 355 (1977).
  3. P. Healey, “Review of Long Wavelength Single-Mode Optical Fiber Reflectometry Techniques,” IEEE/OSA J. Lightwave Technol. LT-3, 876 (1985).
    [CrossRef]
  4. “A Short Technical Note on High Resolution Optical Time-Domain Reflectometry,” Opto-Electronics, Inc., Oakville, Ont.L6L 5K9 Canada.
  5. G. Ripamonti, S. Cova, “Centimeter-Resolution Optical Time Domain Reflectometry using Single-Photon Avalanche Diodes,” in Technical Digest, Conference on Lasers and Electro-Optics (Optical Society of America, Washington, DC, 1986), paper THK21.
  6. D. Uttam, B. Culshaw, “Precision Time-Domain Reflectometry in Optical Fiber Systems using a Frequency Modulated Continuous Wave Ranging Technique,” IEEE/OSA J. Light-wave Technol. LT-3, 971 (1985).
    [CrossRef]
  7. N. J. Frigo, A. Dandridge, C. A. Villarruel, “An Optical Space-Domain Reflectometer Based on the Faraday Effect,” IEEE/OSA J. Lightwave Technol. LT-4, 256 (1986).
    [CrossRef]
  8. J. J. Fontaine, J. C. Diels, C. Y. Wang, “Subpicosecond-Time-Domain Reflectometry,” Opt. Lett. 6, 405 (1981).
    [CrossRef] [PubMed]
  9. M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1964), Chap. 10.
  10. B. L. Danielson, “Optical Time-Domain Reflectometer Specifications and Performance Testing,” Appl. Opt. 24, 2313 (1985).
    [CrossRef] [PubMed]
  11. N. Kashima, I. Sankawa, “Reflection Properties of Splices in Graded-Index Optical Fibers,” Appl. Opt. 22, 3820 (1983).
    [CrossRef] [PubMed]
  12. P. Healey, “Fading Rates in Coherent OTDR,” Electron. Lett. 20, 443 (1984).
    [CrossRef]
  13. T. Okoshi, “Polarization-State Control Schemes for Heterodyne or Homodyne Optical Fiber Communications,” IEEE/OSA J. Lightwave Technol. LT-36, 1232 (1985).
    [CrossRef]
  14. M. Monerie, F. Alard, “Birefringence and Polarization Dispersion Measurements in High-Birefringence Single-Mode Fibers,” Electron. Lett. 23, 198 (1987).
    [CrossRef]
  15. S. Nemoto, T. Makimoto, “Analysis of Splice Loss in Single-Mode Fibers Using a Gaussian Field Approximation,” Opt. Quantum Electron. 11, 447 (1979).
    [CrossRef]
  16. A. H. Hartog, A. J. Conduit, D. N. Payne, “Variation of Pulse Delay with Stress and Temperature in Jacketed and Unjacketed Optical Fibers,” Opt. Quantum Electron. 11, 265 (1979).
    [CrossRef]
  17. R. Kist, S. Ramakrishnan, H. Wolfelschneider, “The Fiber Fabry-Perot and its Application as a Fiber-Optic Sensor Element,” Proc. Soc. Photo-Opt. Instrum. Eng. 586, 126 (1985).
  18. R. W. A. Ayre, “Measurement of Longitudinal Strain in Optical Fiber Cables During Installation by Cable Ploughing,” IEEE/OSA J. Lightwave Technol. LT-4, 15 (1986).
    [CrossRef]
  19. F. M. Sears, L. G. Cohen, “Interferometric Measurements of Dispersion-Spectra Variations in a Single-Mode Fiber,” IEEE/OSA J. Lightwave Technol. LT-2, 181 (1984).
    [CrossRef]
  20. W. D. Bomberger, J. J. Burke, “Interferometric Technique for the Determination of Dispersion in a Short Length of Single-Mode Optical Fiber,” in Technical Digest, Symposium on Optical Fiber Measurements, Boulder, CO (1980).
  21. M. J. Saunders, W. B. Gardner, “Precision Interferometric Measurement of Dispersion in Short Single-Mode Fibers,” in Technical Digest, Symposium on Optical Fiber Measurements, Boulder, CO (1984), pp. 123–126.
  22. J. Stone, L. G. Cohen, “Minimum Dispersion Spectra of Single-Mode Fibers Measured with Subpicosecond Resolution by White-Light Crosscorrelation,” Electron. Lett. 18, 716 (1982).
    [CrossRef]
  23. T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical Fiber Sensor Technology,” IEEE J. Quantum Electron. QE-18, 626 (1982).
    [CrossRef]
  24. A. J. Rogers, “Polarization-Optical Time Domain Reflectometry: A Technique for the Measurement of Field Distributions,” Appl. Opt. 20, 1060 (1981).
    [CrossRef] [PubMed]

1987 (1)

M. Monerie, F. Alard, “Birefringence and Polarization Dispersion Measurements in High-Birefringence Single-Mode Fibers,” Electron. Lett. 23, 198 (1987).
[CrossRef]

1986 (2)

R. W. A. Ayre, “Measurement of Longitudinal Strain in Optical Fiber Cables During Installation by Cable Ploughing,” IEEE/OSA J. Lightwave Technol. LT-4, 15 (1986).
[CrossRef]

N. J. Frigo, A. Dandridge, C. A. Villarruel, “An Optical Space-Domain Reflectometer Based on the Faraday Effect,” IEEE/OSA J. Lightwave Technol. LT-4, 256 (1986).
[CrossRef]

1985 (5)

B. L. Danielson, “Optical Time-Domain Reflectometer Specifications and Performance Testing,” Appl. Opt. 24, 2313 (1985).
[CrossRef] [PubMed]

P. Healey, “Review of Long Wavelength Single-Mode Optical Fiber Reflectometry Techniques,” IEEE/OSA J. Lightwave Technol. LT-3, 876 (1985).
[CrossRef]

D. Uttam, B. Culshaw, “Precision Time-Domain Reflectometry in Optical Fiber Systems using a Frequency Modulated Continuous Wave Ranging Technique,” IEEE/OSA J. Light-wave Technol. LT-3, 971 (1985).
[CrossRef]

T. Okoshi, “Polarization-State Control Schemes for Heterodyne or Homodyne Optical Fiber Communications,” IEEE/OSA J. Lightwave Technol. LT-36, 1232 (1985).
[CrossRef]

R. Kist, S. Ramakrishnan, H. Wolfelschneider, “The Fiber Fabry-Perot and its Application as a Fiber-Optic Sensor Element,” Proc. Soc. Photo-Opt. Instrum. Eng. 586, 126 (1985).

1984 (2)

P. Healey, “Fading Rates in Coherent OTDR,” Electron. Lett. 20, 443 (1984).
[CrossRef]

F. M. Sears, L. G. Cohen, “Interferometric Measurements of Dispersion-Spectra Variations in a Single-Mode Fiber,” IEEE/OSA J. Lightwave Technol. LT-2, 181 (1984).
[CrossRef]

1983 (1)

1982 (2)

J. Stone, L. G. Cohen, “Minimum Dispersion Spectra of Single-Mode Fibers Measured with Subpicosecond Resolution by White-Light Crosscorrelation,” Electron. Lett. 18, 716 (1982).
[CrossRef]

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical Fiber Sensor Technology,” IEEE J. Quantum Electron. QE-18, 626 (1982).
[CrossRef]

1981 (2)

1979 (2)

S. Nemoto, T. Makimoto, “Analysis of Splice Loss in Single-Mode Fibers Using a Gaussian Field Approximation,” Opt. Quantum Electron. 11, 447 (1979).
[CrossRef]

A. H. Hartog, A. J. Conduit, D. N. Payne, “Variation of Pulse Delay with Stress and Temperature in Jacketed and Unjacketed Optical Fibers,” Opt. Quantum Electron. 11, 265 (1979).
[CrossRef]

1977 (2)

M. K. Barnoski, M. D. Rourke, S. M. Jensen, R. T. Melville, “Optical Time Domain Reflectometer,” Appl. Opt. 16, 2375 (1977).
[CrossRef] [PubMed]

S. D. Personick, “Photon Probe—an Optical Time-Domain Reflectometer,” Bell Syst. Tech. J. 56, 355 (1977).

Alard, F.

M. Monerie, F. Alard, “Birefringence and Polarization Dispersion Measurements in High-Birefringence Single-Mode Fibers,” Electron. Lett. 23, 198 (1987).
[CrossRef]

Ayre, R. W. A.

R. W. A. Ayre, “Measurement of Longitudinal Strain in Optical Fiber Cables During Installation by Cable Ploughing,” IEEE/OSA J. Lightwave Technol. LT-4, 15 (1986).
[CrossRef]

Barnoski, M. K.

Bomberger, W. D.

W. D. Bomberger, J. J. Burke, “Interferometric Technique for the Determination of Dispersion in a Short Length of Single-Mode Optical Fiber,” in Technical Digest, Symposium on Optical Fiber Measurements, Boulder, CO (1980).

Born, M.

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1964), Chap. 10.

Bucaro, J. A.

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical Fiber Sensor Technology,” IEEE J. Quantum Electron. QE-18, 626 (1982).
[CrossRef]

Burke, J. J.

W. D. Bomberger, J. J. Burke, “Interferometric Technique for the Determination of Dispersion in a Short Length of Single-Mode Optical Fiber,” in Technical Digest, Symposium on Optical Fiber Measurements, Boulder, CO (1980).

Cohen, L. G.

F. M. Sears, L. G. Cohen, “Interferometric Measurements of Dispersion-Spectra Variations in a Single-Mode Fiber,” IEEE/OSA J. Lightwave Technol. LT-2, 181 (1984).
[CrossRef]

J. Stone, L. G. Cohen, “Minimum Dispersion Spectra of Single-Mode Fibers Measured with Subpicosecond Resolution by White-Light Crosscorrelation,” Electron. Lett. 18, 716 (1982).
[CrossRef]

Cole, J. H.

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical Fiber Sensor Technology,” IEEE J. Quantum Electron. QE-18, 626 (1982).
[CrossRef]

Conduit, A. J.

A. H. Hartog, A. J. Conduit, D. N. Payne, “Variation of Pulse Delay with Stress and Temperature in Jacketed and Unjacketed Optical Fibers,” Opt. Quantum Electron. 11, 265 (1979).
[CrossRef]

Cova, S.

G. Ripamonti, S. Cova, “Centimeter-Resolution Optical Time Domain Reflectometry using Single-Photon Avalanche Diodes,” in Technical Digest, Conference on Lasers and Electro-Optics (Optical Society of America, Washington, DC, 1986), paper THK21.

Culshaw, B.

D. Uttam, B. Culshaw, “Precision Time-Domain Reflectometry in Optical Fiber Systems using a Frequency Modulated Continuous Wave Ranging Technique,” IEEE/OSA J. Light-wave Technol. LT-3, 971 (1985).
[CrossRef]

Dandridge, A.

N. J. Frigo, A. Dandridge, C. A. Villarruel, “An Optical Space-Domain Reflectometer Based on the Faraday Effect,” IEEE/OSA J. Lightwave Technol. LT-4, 256 (1986).
[CrossRef]

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical Fiber Sensor Technology,” IEEE J. Quantum Electron. QE-18, 626 (1982).
[CrossRef]

Danielson, B. L.

Diels, J. C.

Fontaine, J. J.

Frigo, N. J.

N. J. Frigo, A. Dandridge, C. A. Villarruel, “An Optical Space-Domain Reflectometer Based on the Faraday Effect,” IEEE/OSA J. Lightwave Technol. LT-4, 256 (1986).
[CrossRef]

Gardner, W. B.

M. J. Saunders, W. B. Gardner, “Precision Interferometric Measurement of Dispersion in Short Single-Mode Fibers,” in Technical Digest, Symposium on Optical Fiber Measurements, Boulder, CO (1984), pp. 123–126.

Giallorenzi, T. G.

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical Fiber Sensor Technology,” IEEE J. Quantum Electron. QE-18, 626 (1982).
[CrossRef]

Hartog, A. H.

A. H. Hartog, A. J. Conduit, D. N. Payne, “Variation of Pulse Delay with Stress and Temperature in Jacketed and Unjacketed Optical Fibers,” Opt. Quantum Electron. 11, 265 (1979).
[CrossRef]

Healey, P.

P. Healey, “Review of Long Wavelength Single-Mode Optical Fiber Reflectometry Techniques,” IEEE/OSA J. Lightwave Technol. LT-3, 876 (1985).
[CrossRef]

P. Healey, “Fading Rates in Coherent OTDR,” Electron. Lett. 20, 443 (1984).
[CrossRef]

Jensen, S. M.

Kashima, N.

Kist, R.

R. Kist, S. Ramakrishnan, H. Wolfelschneider, “The Fiber Fabry-Perot and its Application as a Fiber-Optic Sensor Element,” Proc. Soc. Photo-Opt. Instrum. Eng. 586, 126 (1985).

Makimoto, T.

S. Nemoto, T. Makimoto, “Analysis of Splice Loss in Single-Mode Fibers Using a Gaussian Field Approximation,” Opt. Quantum Electron. 11, 447 (1979).
[CrossRef]

Melville, R. T.

Monerie, M.

M. Monerie, F. Alard, “Birefringence and Polarization Dispersion Measurements in High-Birefringence Single-Mode Fibers,” Electron. Lett. 23, 198 (1987).
[CrossRef]

Nemoto, S.

S. Nemoto, T. Makimoto, “Analysis of Splice Loss in Single-Mode Fibers Using a Gaussian Field Approximation,” Opt. Quantum Electron. 11, 447 (1979).
[CrossRef]

Okoshi, T.

T. Okoshi, “Polarization-State Control Schemes for Heterodyne or Homodyne Optical Fiber Communications,” IEEE/OSA J. Lightwave Technol. LT-36, 1232 (1985).
[CrossRef]

Payne, D. N.

A. H. Hartog, A. J. Conduit, D. N. Payne, “Variation of Pulse Delay with Stress and Temperature in Jacketed and Unjacketed Optical Fibers,” Opt. Quantum Electron. 11, 265 (1979).
[CrossRef]

Personick, S. D.

S. D. Personick, “Photon Probe—an Optical Time-Domain Reflectometer,” Bell Syst. Tech. J. 56, 355 (1977).

Priest, R. G.

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical Fiber Sensor Technology,” IEEE J. Quantum Electron. QE-18, 626 (1982).
[CrossRef]

Ramakrishnan, S.

R. Kist, S. Ramakrishnan, H. Wolfelschneider, “The Fiber Fabry-Perot and its Application as a Fiber-Optic Sensor Element,” Proc. Soc. Photo-Opt. Instrum. Eng. 586, 126 (1985).

Rashleigh, S. C.

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical Fiber Sensor Technology,” IEEE J. Quantum Electron. QE-18, 626 (1982).
[CrossRef]

Ripamonti, G.

G. Ripamonti, S. Cova, “Centimeter-Resolution Optical Time Domain Reflectometry using Single-Photon Avalanche Diodes,” in Technical Digest, Conference on Lasers and Electro-Optics (Optical Society of America, Washington, DC, 1986), paper THK21.

Rogers, A. J.

Rourke, M. D.

Sankawa, I.

Saunders, M. J.

M. J. Saunders, W. B. Gardner, “Precision Interferometric Measurement of Dispersion in Short Single-Mode Fibers,” in Technical Digest, Symposium on Optical Fiber Measurements, Boulder, CO (1984), pp. 123–126.

Sears, F. M.

F. M. Sears, L. G. Cohen, “Interferometric Measurements of Dispersion-Spectra Variations in a Single-Mode Fiber,” IEEE/OSA J. Lightwave Technol. LT-2, 181 (1984).
[CrossRef]

Sigel, G. H.

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical Fiber Sensor Technology,” IEEE J. Quantum Electron. QE-18, 626 (1982).
[CrossRef]

Stone, J.

J. Stone, L. G. Cohen, “Minimum Dispersion Spectra of Single-Mode Fibers Measured with Subpicosecond Resolution by White-Light Crosscorrelation,” Electron. Lett. 18, 716 (1982).
[CrossRef]

Uttam, D.

D. Uttam, B. Culshaw, “Precision Time-Domain Reflectometry in Optical Fiber Systems using a Frequency Modulated Continuous Wave Ranging Technique,” IEEE/OSA J. Light-wave Technol. LT-3, 971 (1985).
[CrossRef]

Villarruel, C. A.

N. J. Frigo, A. Dandridge, C. A. Villarruel, “An Optical Space-Domain Reflectometer Based on the Faraday Effect,” IEEE/OSA J. Lightwave Technol. LT-4, 256 (1986).
[CrossRef]

Wang, C. Y.

Wolf, E.

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1964), Chap. 10.

Wolfelschneider, H.

R. Kist, S. Ramakrishnan, H. Wolfelschneider, “The Fiber Fabry-Perot and its Application as a Fiber-Optic Sensor Element,” Proc. Soc. Photo-Opt. Instrum. Eng. 586, 126 (1985).

Appl. Opt. (4)

Bell Syst. Tech. J. (1)

S. D. Personick, “Photon Probe—an Optical Time-Domain Reflectometer,” Bell Syst. Tech. J. 56, 355 (1977).

Electron. Lett. (3)

P. Healey, “Fading Rates in Coherent OTDR,” Electron. Lett. 20, 443 (1984).
[CrossRef]

M. Monerie, F. Alard, “Birefringence and Polarization Dispersion Measurements in High-Birefringence Single-Mode Fibers,” Electron. Lett. 23, 198 (1987).
[CrossRef]

J. Stone, L. G. Cohen, “Minimum Dispersion Spectra of Single-Mode Fibers Measured with Subpicosecond Resolution by White-Light Crosscorrelation,” Electron. Lett. 18, 716 (1982).
[CrossRef]

IEEE J. Quantum Electron. (1)

T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel, J. H. Cole, S. C. Rashleigh, R. G. Priest, “Optical Fiber Sensor Technology,” IEEE J. Quantum Electron. QE-18, 626 (1982).
[CrossRef]

IEEE/OSA J. Light-wave Technol. (1)

D. Uttam, B. Culshaw, “Precision Time-Domain Reflectometry in Optical Fiber Systems using a Frequency Modulated Continuous Wave Ranging Technique,” IEEE/OSA J. Light-wave Technol. LT-3, 971 (1985).
[CrossRef]

IEEE/OSA J. Lightwave Technol. (5)

N. J. Frigo, A. Dandridge, C. A. Villarruel, “An Optical Space-Domain Reflectometer Based on the Faraday Effect,” IEEE/OSA J. Lightwave Technol. LT-4, 256 (1986).
[CrossRef]

P. Healey, “Review of Long Wavelength Single-Mode Optical Fiber Reflectometry Techniques,” IEEE/OSA J. Lightwave Technol. LT-3, 876 (1985).
[CrossRef]

T. Okoshi, “Polarization-State Control Schemes for Heterodyne or Homodyne Optical Fiber Communications,” IEEE/OSA J. Lightwave Technol. LT-36, 1232 (1985).
[CrossRef]

R. W. A. Ayre, “Measurement of Longitudinal Strain in Optical Fiber Cables During Installation by Cable Ploughing,” IEEE/OSA J. Lightwave Technol. LT-4, 15 (1986).
[CrossRef]

F. M. Sears, L. G. Cohen, “Interferometric Measurements of Dispersion-Spectra Variations in a Single-Mode Fiber,” IEEE/OSA J. Lightwave Technol. LT-2, 181 (1984).
[CrossRef]

Opt. Lett. (1)

Opt. Quantum Electron. (2)

S. Nemoto, T. Makimoto, “Analysis of Splice Loss in Single-Mode Fibers Using a Gaussian Field Approximation,” Opt. Quantum Electron. 11, 447 (1979).
[CrossRef]

A. H. Hartog, A. J. Conduit, D. N. Payne, “Variation of Pulse Delay with Stress and Temperature in Jacketed and Unjacketed Optical Fibers,” Opt. Quantum Electron. 11, 265 (1979).
[CrossRef]

Proc. Soc. Photo-Opt. Instrum. Eng. (1)

R. Kist, S. Ramakrishnan, H. Wolfelschneider, “The Fiber Fabry-Perot and its Application as a Fiber-Optic Sensor Element,” Proc. Soc. Photo-Opt. Instrum. Eng. 586, 126 (1985).

Other (5)

M. Born, E. Wolf, Principles of Optics (Pergamon, New York, 1964), Chap. 10.

“A Short Technical Note on High Resolution Optical Time-Domain Reflectometry,” Opto-Electronics, Inc., Oakville, Ont.L6L 5K9 Canada.

G. Ripamonti, S. Cova, “Centimeter-Resolution Optical Time Domain Reflectometry using Single-Photon Avalanche Diodes,” in Technical Digest, Conference on Lasers and Electro-Optics (Optical Society of America, Washington, DC, 1986), paper THK21.

W. D. Bomberger, J. J. Burke, “Interferometric Technique for the Determination of Dispersion in a Short Length of Single-Mode Optical Fiber,” in Technical Digest, Symposium on Optical Fiber Measurements, Boulder, CO (1980).

M. J. Saunders, W. B. Gardner, “Precision Interferometric Measurement of Dispersion in Short Single-Mode Fibers,” in Technical Digest, Symposium on Optical Fiber Measurements, Boulder, CO (1984), pp. 123–126.

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Figures (7)

Fig. 1
Fig. 1

Schematic diagram of a conventional pulse-echo optical time-domain reflectometer. The coupler and light transmitting elements can be made with optical fibers.

Fig. 2
Fig. 2

Schematic diagram of the Michelson reflectometer with cross-correlation detection is depicted in (a). The location of fiber splices is indicated by X. The coupler splitting ratio is k. Interference patterns are observed from the isolated reflection R when the mirror M is scanned by the PZT. The interferogram occurs only when the difference in propagation delays between the test and reference paths is less than the coherence time of the optical source. Discrimination between different events in the test waveguide is, therefore, accomplished by the light coherence. In (b) an expanded segment of the test waveguide is shown. In some cases it is possible to estimate the loss A between the two reflections R1 and R2 (see text).

Fig. 3
Fig. 3

Experimental interferograms generated by the Fresnel reflections at the gap between two single-mode optical fibers. In (a) the fibers are in contact, although there is still some air gap between them due to end-wedge effects. In (b) the gap is increased to ~13 μm. In (c) the separation is 970 μm. The reflected power from the receiving fiber is considerably attenuated due to diffraction effects. The scale here is multiplied by a factor of 50 relative to (a) and (b).

Fig. 4
Fig. 4

Simulated interferograms for the configuration of Fig. 3. The optical path difference, twice the gap spacing, is expressed in terms of wavelengths. These signatures show that structure can be observed due to gap spacings of <1 μm. For a zero spacing no power should be reflected. For integral multiples of λ, the signals from the two reflecting surfaces partially cancel, and at a spacing of λ/2 they reinforce each other. The responses in (a) and (d), while superficially similar, exhibit subtle shape differences.

Fig. 5
Fig. 5

Extension of a stressed fiber can be measured by observing the shift in the location of the interferogram. This was done by attaching a concentric weight W to the fiber. From this measurement we can obtain the stress-induced change in pulse propagation time.

Fig. 6
Fig. 6

Amount of material removed by polishing a fiber endface can also be estimated from the interferogram shift. The fiber is held in a jig to assure that the axis is perpendicular to the polishing surface. In (a) an as-cleaved fiber has been polished slightly on 5-μm abrasive paper. In (d) the fiber has been further finished on 1-μm abrasive paper. The quality of the endface is also indicated by the magnitude of the reflected power.

Fig. 7
Fig. 7

Group index of refraction for a short length of single-mode fiber can be obtained from the ratio of the physical length Lair to the distance between appropriate reflections on the interferogram Lopt.

Equations (13)

Equations on this page are rendered with MathJax. Learn more.

P d ( τ ) = P 0 K ( 1 - K ) [ 1 + A i 2 R i + 2 A i R i γ 12 ( τ ) cos θ ]
θ = 2 π f τ + ξ .
Δ τ = 4 ln 2 π Δ f FWHM .
V ( τ ) = P max - P min P max + P min .
V i ( τ ) = 2 A i R i 1 + A i 2 R i γ 12 ( τ ) .
Δ x = v 2 Δ f
- 10 log A = 5 log [ ( 1 - R 1 ) 2 R 2 R 1 ] + 10 ( S 1 S 2 ) ( dB ) .
x gap = m λ / 2 ,
loss = 10 log [ 4 / ( G 2 + 4 ) ] ( dB ) ,
G = λ x 2 π n r 2 .
d T d σ = 1 c ( N d L d σ + L d N d σ )
Δ x = m λ / 2 N ,
N = L air / L opt ,

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