Abstract

A sensitive, nondestructive, and noncontacting method is described for obtaining structural information on the preforms from which optical fibers are produced. The technique allows the determination of the core size and the core eccentricity from direct observation of light traversing the preform normal to its axis. Also observable are the core–cladding interface structure, individual deposition layer structure and variations, imperfections within the core and the cladding, and the presence of an axial refractive-index depression. Results and implications from a variety of multimode and single-mode preforms are presented along with a theoretical analysis of the observations.

© 1979 Optical Society of America

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References

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  1. H. M. Presby, D. Marcuse, Appl. Opt. 13, 2882 (1974).
    [CrossRef] [PubMed]
  2. H. M. Presby, R. D. Standley, J. B. MacChesney, P. B. O’Connor, Bell Syst. Tech. J. 54, 1681 (1975).
  3. P. L. Chu, Electron. Lett. 13, 736 (1977).
    [CrossRef]
  4. H. M. Presby, “Axial Refractive Index Depression In Preforms and Fibers”, to be published in Fiber and Integrated Optics2, No. 2.
  5. H. M. Presby, J. Opt. Soc. Am. 64, 280 (1974).
    [CrossRef]

1977 (1)

P. L. Chu, Electron. Lett. 13, 736 (1977).
[CrossRef]

1975 (1)

H. M. Presby, R. D. Standley, J. B. MacChesney, P. B. O’Connor, Bell Syst. Tech. J. 54, 1681 (1975).

1974 (2)

Chu, P. L.

P. L. Chu, Electron. Lett. 13, 736 (1977).
[CrossRef]

MacChesney, J. B.

H. M. Presby, R. D. Standley, J. B. MacChesney, P. B. O’Connor, Bell Syst. Tech. J. 54, 1681 (1975).

Marcuse, D.

O’Connor, P. B.

H. M. Presby, R. D. Standley, J. B. MacChesney, P. B. O’Connor, Bell Syst. Tech. J. 54, 1681 (1975).

Presby, H. M.

H. M. Presby, R. D. Standley, J. B. MacChesney, P. B. O’Connor, Bell Syst. Tech. J. 54, 1681 (1975).

H. M. Presby, J. Opt. Soc. Am. 64, 280 (1974).
[CrossRef]

H. M. Presby, D. Marcuse, Appl. Opt. 13, 2882 (1974).
[CrossRef] [PubMed]

H. M. Presby, “Axial Refractive Index Depression In Preforms and Fibers”, to be published in Fiber and Integrated Optics2, No. 2.

Standley, R. D.

H. M. Presby, R. D. Standley, J. B. MacChesney, P. B. O’Connor, Bell Syst. Tech. J. 54, 1681 (1975).

Appl. Opt. (1)

Bell Syst. Tech. J. (1)

H. M. Presby, R. D. Standley, J. B. MacChesney, P. B. O’Connor, Bell Syst. Tech. J. 54, 1681 (1975).

Electron. Lett. (1)

P. L. Chu, Electron. Lett. 13, 736 (1977).
[CrossRef]

J. Opt. Soc. Am. (1)

Other (1)

H. M. Presby, “Axial Refractive Index Depression In Preforms and Fibers”, to be published in Fiber and Integrated Optics2, No. 2.

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Figures (14)

Fig. 1
Fig. 1

Experimental arrangement for preform diagnostics.

Fig. 2
Fig. 2

Observation of homogeneous rod with no core. The rod is approximately 1 cm in diameter.

Fig. 3
Fig. 3

Light-intensity-pattern (diagnostigram) from MCVD germanium-doped preform. Approximately a 40-cm length of the preform is observed.

Fig. 4
Fig. 4

Magnified deposition layers. Magnification is obtained by moving the observation screen further from the preform.

Fig. 5
Fig. 5

Diagnostigram from a second MCVD germanium-doped preform containing many more deposition layers than the one previously shown.

Fig. 6
Fig. 6

(a) Diagnostigram; (b) transmitted light photomicrograph; and (c) interferogram of relatively uniform preform. The diameter of the core in the preform tip sample (b) and (c) is approximately 0.55 mm.

Fig. 7
Fig. 7

(a) Diagnostigram; (b) transmitted-light photomnicrograph; and (c) interferogramn of second relatively uniform preform. The diameter of the core in the preform tip sample (b) and (c) is approximately 0.6 mm.

Fig. 8
Fig. 8

(a) Diagnostigram, (b) transmitted-light photomicrograph, and (c) interferogram of a preform with a perturbed index profile at the interface and nonuniform layers. The diameter of the core in the preform tip sample (b) and (c) is approximately 0.6 mm.

Fig. 9
Fig. 9

(a) Diagnostigram; (b) transmitted-light photomicrograph; and (c) interferogram of a preform with a perturbed index profile at the interface and near axis. The diameter of the core in the preform tip sample (b) and (c) is approximately 0.58 mm.

Fig. 10
Fig. 10

Diagnostigram of incompletely collapsed preforms showing the continuous observation of deposition layers.

Fig. 11
Fig. 11

Diagnostigram of single-mode preforms showing eccentric core.

Fig. 12
Fig. 12

Diagnostigrams of (a) single-mode and (b) multimode boron-doped MCVD fabricated preforms.

Fig. 13
Fig. 13

Ray path in preform with concentric layers of slightly different refractive index.

Fig. 14
Fig. 14

Plot of radius of index discontinuity vs ray angle.

Equations (8)

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ψ = 2 [ arcsin ( d b ) - arcsin ( d n b ) ] ,
d = n b sin ( ψ / 2 ) [ ( n 2 + 1 ) - 2 n cos ( ψ / 2 ) ] 1 / 2 .
r = d / n
r = b sin ( ψ / 2 ) [ ( n 2 + 1 ) - 2 n cos ( ψ / 2 ) ] 1 / 2 .
R = [ n ϕ - ( 2 n Δ n ) 1 / 2 n ϕ + ( 2 n Δ n ) 1 / 2 ] 2 .
ϕ = { 2 [ ( Δ n ) / n ] } 1 / 2 ,
Δ n n = [ n cos ( ψ / 2 ) - 1 ] [ n - cos ( ψ / 2 ) ] 2 [ n 2 - 2 n cos ( ψ / 2 ) + 1 ] sin ( ψ / 2 ) Δ ψ
( Δ n ) / n ( Δ ψ ) / ψ

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