Abstract

A new technique for measuring the attenuation of light in clad fibers is discussed. The basic approach is to measure the temperature rise produced in the fiber by the absorption of the light. Calculations indicate that the theoretical limit of sensitivity, which should be approachable with a relatively simple experimental configuration, is a loss of about 2.5 × 10−7/cm with 1 mW of light power and a 1-cm long sample. The theoretical sensitivity limit should improve with the square root of the sample length. A variation of the basic approach, which may make it possible to monitor attenuation in fibers as they are being drawn, is also discussed.

© 1974 Optical Society of America

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References

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  1. H.-H. Witte, Appl. Apt. 11, 777 (1972).
    [CrossRef]
  2. D. A. Pinnow, T. C. Rich, Appl. Opt. 12, 984 (1973).
    [CrossRef] [PubMed]
  3. A. R. Tynes, Bell Lab. Rec. 50, 302 (1972); D. B. Keck, P. C. Schultz, F. Zimar, Appl. Phys. Lett. 21, 215 (1972).
    [CrossRef]
  4. D. A. Pinnow, T. C. Rich, Appl. Opt. 13, 1376 (1974).
    [CrossRef] [PubMed]
  5. P. Kaiser, H. W. Astle, J. Opt. Soc. Am. 64, 469 (1974).
    [CrossRef]
  6. We assume that the EM field of the propagating light is well enough confined to the core that the metallization will not affect the transmission. This condition is not completely fulfilled for fiber dimensions now being tested. An accompanying article [R. L. Cohen, K. W. West, P. D. Lazay, J. Simpson, Appl. Opt. 13, 2522 (1974)] discusses simple alternatives to the metallization approach that have been used successfully for loss measurements.
    [CrossRef] [PubMed]
  7. Light loss by absorption will result directly in a rise in fiber temperature; light lost from the core by scattering mechanisms should be very rapidly absorbed by repeated reflection at the cladding-metal interface, where the reflectivity will be only ≈0.7. Thus, all light lost from the propagating core mode will result in heating of the fiber and be measured.
  8. Due to the small diameter and low thermal conductivity of glass fibers, the longitudinal heat conductivity is very small compared to the loss of heat by radiation, even when the sample length is only a few cm. Thus, end effects are negligible.
  9. The emissivity of pure nickel films is low, but can be improved either by overcoating the film with a black material or by chemical processing.
  10. See, e.g., L. B. Kreuzer, J. Appl. Phys. 42, 2934 (1971) and; W. R. Harshbarger, M. B. Robin, Acc. Chem. Res. 6, 329 (1973).
    [CrossRef]
  11. R. L. Cohen, K. W. West, to be published.

1974 (3)

1973 (1)

1972 (2)

H.-H. Witte, Appl. Apt. 11, 777 (1972).
[CrossRef]

A. R. Tynes, Bell Lab. Rec. 50, 302 (1972); D. B. Keck, P. C. Schultz, F. Zimar, Appl. Phys. Lett. 21, 215 (1972).
[CrossRef]

1971 (1)

See, e.g., L. B. Kreuzer, J. Appl. Phys. 42, 2934 (1971) and; W. R. Harshbarger, M. B. Robin, Acc. Chem. Res. 6, 329 (1973).
[CrossRef]

Astle, H. W.

Cohen, R. L.

Kaiser, P.

Kreuzer, L. B.

See, e.g., L. B. Kreuzer, J. Appl. Phys. 42, 2934 (1971) and; W. R. Harshbarger, M. B. Robin, Acc. Chem. Res. 6, 329 (1973).
[CrossRef]

Lazay, P. D.

Pinnow, D. A.

Rich, T. C.

Simpson, J.

Tynes, A. R.

A. R. Tynes, Bell Lab. Rec. 50, 302 (1972); D. B. Keck, P. C. Schultz, F. Zimar, Appl. Phys. Lett. 21, 215 (1972).
[CrossRef]

West, K. W.

Witte, H.-H.

H.-H. Witte, Appl. Apt. 11, 777 (1972).
[CrossRef]

Appl. Apt. (1)

H.-H. Witte, Appl. Apt. 11, 777 (1972).
[CrossRef]

Appl. Opt. (3)

Bell Lab. Rec. (1)

A. R. Tynes, Bell Lab. Rec. 50, 302 (1972); D. B. Keck, P. C. Schultz, F. Zimar, Appl. Phys. Lett. 21, 215 (1972).
[CrossRef]

J. Appl. Phys. (1)

See, e.g., L. B. Kreuzer, J. Appl. Phys. 42, 2934 (1971) and; W. R. Harshbarger, M. B. Robin, Acc. Chem. Res. 6, 329 (1973).
[CrossRef]

J. Opt. Soc. Am. (1)

Other (4)

Light loss by absorption will result directly in a rise in fiber temperature; light lost from the core by scattering mechanisms should be very rapidly absorbed by repeated reflection at the cladding-metal interface, where the reflectivity will be only ≈0.7. Thus, all light lost from the propagating core mode will result in heating of the fiber and be measured.

Due to the small diameter and low thermal conductivity of glass fibers, the longitudinal heat conductivity is very small compared to the loss of heat by radiation, even when the sample length is only a few cm. Thus, end effects are negligible.

The emissivity of pure nickel films is low, but can be improved either by overcoating the film with a black material or by chemical processing.

R. L. Cohen, K. W. West, to be published.

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Figures (3)

Fig. 1
Fig. 1

Cell for testing metallized fiber.

Fig. 2
Fig. 2

Feedback arrangement for bolometer measurements. The dc component of the operational amplifier output supplies the bolometer measuring current through the feedback resistor. This measuring current is determined by the size of the reference voltage, so that the dc voltage drop across the bolometer is equal to the reference voltage. The voltage resulting from bolometer resistance changes then appears as a small ac component superimposed on the much larger dc voltage at the output of the operational amplifier.

Fig. 3
Fig. 3

Measurement of fiber attenuation during drawing.

Equations (4)

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P = A · σ · e ( T 4 T 0 4 ) ,
T = { 1 / [ ( A σ e ) 1 / 4 ] } ( P + T 0 4 e σ A ) 1 / 4 ,
d T / d P = { 1 / [ 4 ( A σ e ) 1 / 4 ] } ( P + T 0 4 e σ A ) 3 / 4 .
S = d T / d P = 1 / ( 4 e σ A T 0 3 )

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