Abstract

We have designed and measured a passive device based on plastic optical fibers (POF’s) that one can use to determine the indices of refraction of liquids. A complementary software has also been designed to simulate the behavior of the device. We report on the theoretical model developed for the device, its implementation in a simulation software program, and the results of the simulation. A comparison of the experimental and calculated results is also shown and discussed.

© 2000 Optical Society of America

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References

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  1. T. Kaino, “Polymer optical fibers,” in Polymers for Lightwave and Integrated Optics: Technology and Applications, L. A. Hornak, ed. (Marcel Dekker, New York, 1992), pp. 1–38.
  2. Y. Koike, T. Ishigure, E. Nihei, “High-bandwidth graded index polymer optical fiber,” J. Lightwave Technol. 13, 1475–1489 (1995); T. Ishigure, E. Nihei, Y. Koike, C. E. Forbes, L. LaNieve, R. Straff, H. A. Deckers, “Large core, high-bandwidth polymer optical fiber for near infrared use,” IEEE Photon. Technol. Lett. 7, 403–405, (1995); E. Nihei, T. Ishigure, N. Tanio, Y. Koike, “Present prospect of graded index plastic optical fiber in telecommunication,” IEICE Trans. Electron. E-80-c, 117–122 (1997).
  3. C. Koeppen, R. F. Shi, W. D. Chen, A. F. Garito, “Properties of plastic optical fibers,” J. Opt. Soc. Am. B 15, 727–739 (1998).
    [CrossRef]
  4. T. F. Stehlin, Y. Liu, “Polymer optical fiber sensors,” in Proceedings of the First International Conference on Plastic Optical Fibers and Applications—POF’92 (Information Gatekeepers, Inc., Boston, Mass., 1992), pp. 124–127.
  5. N. Ioannides, D. Kalymnios, I. W. Rogers, “Experimental and theoretical investigations of a POF based displacement sensor,” in Proceedings of the Second International Conference on Plastic Optical Fibers and Applications—POF’93 (European Institute for Communications and Networks, Geneva, 1993), pp. 162–165.
  6. K. Asada, H. Yuuki, “Fiber optic temperature sensor,” in Proceedings of the Third International Conference on Plastic Optical Fibers and Applications—POF’94 (European Institute for Communications and Networks, Geneva, 1994), pp. 49–51.
  7. J. D. Weiss, “The pressure approach to fiber liquid-level sensors,” in Proceedings of the Fourth International Conference on Plastic Optical Fibers and Applications—POF’95 (European Institute for Communications and Networks, Geneva, 1995), pp. 167–170.
  8. S. Hadjiloucas, D. A. Keating, M. J. Usher, “Plastic optical fiber sensor for plant water relations,” in Proceedings of the Fifth International Conference on Plastic Optical Fibers and Applications—POF’96 (French Club Fibres Optiques Plastiques, Paris, 1996), pp. 228–237.
  9. S. Yamakawa, “Plastic optical fiber chemical sensor with pencil-shaped distal tip fluorescence probe,” in Proceedings of the Sixth International Conference on Plastic Optical Fibers and Applications—POF’97 (Office of Naval Research, Asian Office and POF Consortium, Tokyo, Japan, 1997), pp. 109–110.
  10. M. Morisawa, S. Muto, G. Vishno, “POF sensor for detecting oxygen in air and in water,” in Proceedings of the Seventh International Conference on Plastic Optical Fibers and Applications—POF’98 (International Committee of POF-ICPOF, Germany, 1998), pp. 243–244.
  11. B. D. Gupta, C. D. Singh, “Fiber-optic evanescent field absorption sensor: a theoretical evaluation,” Fiber Integr. Opt. 13, 433–443 (1994).
    [CrossRef]
  12. A. L. Harmer, “Optical fiber refractometer using attenuation of cladding modes,” in Proceedings of Optical Fiber Sensors 1 (Institution of Electronics Engineers, London, 1983), pp. 104–108.
  13. J. J. Bayle, J. Mateo, “Plastic optical fiber sensor of refractive index, based on evanescent field,” in Proceedings of the Fifth International Conference on Plastic Optical Fibers and Applications—POF’96 (French Club Fibres Optiques Plastiques, Paris, 1996), pp. 220–227.
  14. J. Arrue, J. Zubia, G. Fuster, D. Kalymnios, “Light power behavior when bending POFs,” IEE Proc. Optoelectron. 145, 1–6, (1998); G. Garitaonaindía, J. Zubia, U. Irusta, J. Arrue, “Passive device based on POF to determine the index of refraction in liquids,” in Proceedings of the Seventh International Conference on Plastic Optical Fibers and Applications—POF’98 (International Committee of POF-ICPOF, Germany, 1998), pp. 178–184.
  15. A. Aguirre, U. Irusta, J. Zubia, J. Arrue, “Fabrication of low loss POF contact couplers,” in Proceedings of the Sixth International Conference on Plastic Optical Fibers and Applications—POF’97 (Office of Naval Research, Asian Office and POF Consortium, Tokyo, Japan, 1997), pp. 132–133; J. Zubia, U. Irusta, J. Arrue, A. Aguirre, “Design and characterization of a POF active coupler,” IEEE Photon. Technol. Lett. 10, 1578–1580 (1998).
  16. A. Ghatak, E. Sharma, J. Kompella, “Exact paths in bent waveguides,” Appl. Opt. 27, 3180–3184 (1988); J. Arrúe, J. Zubia, “Analysis of the decrease in attenuation achieved by properly bending plastic optical fibers,” IEE Proc. Optoelectron. 143, 135–138 (1996).
    [CrossRef] [PubMed]
  17. A. W. Snyder, J. Love, Optical Waveguide Theory (Chapman & Hall, London, 1996).

1998 (2)

C. Koeppen, R. F. Shi, W. D. Chen, A. F. Garito, “Properties of plastic optical fibers,” J. Opt. Soc. Am. B 15, 727–739 (1998).
[CrossRef]

J. Arrue, J. Zubia, G. Fuster, D. Kalymnios, “Light power behavior when bending POFs,” IEE Proc. Optoelectron. 145, 1–6, (1998); G. Garitaonaindía, J. Zubia, U. Irusta, J. Arrue, “Passive device based on POF to determine the index of refraction in liquids,” in Proceedings of the Seventh International Conference on Plastic Optical Fibers and Applications—POF’98 (International Committee of POF-ICPOF, Germany, 1998), pp. 178–184.

1995 (1)

Y. Koike, T. Ishigure, E. Nihei, “High-bandwidth graded index polymer optical fiber,” J. Lightwave Technol. 13, 1475–1489 (1995); T. Ishigure, E. Nihei, Y. Koike, C. E. Forbes, L. LaNieve, R. Straff, H. A. Deckers, “Large core, high-bandwidth polymer optical fiber for near infrared use,” IEEE Photon. Technol. Lett. 7, 403–405, (1995); E. Nihei, T. Ishigure, N. Tanio, Y. Koike, “Present prospect of graded index plastic optical fiber in telecommunication,” IEICE Trans. Electron. E-80-c, 117–122 (1997).

1994 (1)

B. D. Gupta, C. D. Singh, “Fiber-optic evanescent field absorption sensor: a theoretical evaluation,” Fiber Integr. Opt. 13, 433–443 (1994).
[CrossRef]

1988 (1)

Aguirre, A.

A. Aguirre, U. Irusta, J. Zubia, J. Arrue, “Fabrication of low loss POF contact couplers,” in Proceedings of the Sixth International Conference on Plastic Optical Fibers and Applications—POF’97 (Office of Naval Research, Asian Office and POF Consortium, Tokyo, Japan, 1997), pp. 132–133; J. Zubia, U. Irusta, J. Arrue, A. Aguirre, “Design and characterization of a POF active coupler,” IEEE Photon. Technol. Lett. 10, 1578–1580 (1998).

Arrue, J.

J. Arrue, J. Zubia, G. Fuster, D. Kalymnios, “Light power behavior when bending POFs,” IEE Proc. Optoelectron. 145, 1–6, (1998); G. Garitaonaindía, J. Zubia, U. Irusta, J. Arrue, “Passive device based on POF to determine the index of refraction in liquids,” in Proceedings of the Seventh International Conference on Plastic Optical Fibers and Applications—POF’98 (International Committee of POF-ICPOF, Germany, 1998), pp. 178–184.

A. Aguirre, U. Irusta, J. Zubia, J. Arrue, “Fabrication of low loss POF contact couplers,” in Proceedings of the Sixth International Conference on Plastic Optical Fibers and Applications—POF’97 (Office of Naval Research, Asian Office and POF Consortium, Tokyo, Japan, 1997), pp. 132–133; J. Zubia, U. Irusta, J. Arrue, A. Aguirre, “Design and characterization of a POF active coupler,” IEEE Photon. Technol. Lett. 10, 1578–1580 (1998).

Asada, K.

K. Asada, H. Yuuki, “Fiber optic temperature sensor,” in Proceedings of the Third International Conference on Plastic Optical Fibers and Applications—POF’94 (European Institute for Communications and Networks, Geneva, 1994), pp. 49–51.

Bayle, J. J.

J. J. Bayle, J. Mateo, “Plastic optical fiber sensor of refractive index, based on evanescent field,” in Proceedings of the Fifth International Conference on Plastic Optical Fibers and Applications—POF’96 (French Club Fibres Optiques Plastiques, Paris, 1996), pp. 220–227.

Chen, W. D.

Fuster, G.

J. Arrue, J. Zubia, G. Fuster, D. Kalymnios, “Light power behavior when bending POFs,” IEE Proc. Optoelectron. 145, 1–6, (1998); G. Garitaonaindía, J. Zubia, U. Irusta, J. Arrue, “Passive device based on POF to determine the index of refraction in liquids,” in Proceedings of the Seventh International Conference on Plastic Optical Fibers and Applications—POF’98 (International Committee of POF-ICPOF, Germany, 1998), pp. 178–184.

Garito, A. F.

Ghatak, A.

Gupta, B. D.

B. D. Gupta, C. D. Singh, “Fiber-optic evanescent field absorption sensor: a theoretical evaluation,” Fiber Integr. Opt. 13, 433–443 (1994).
[CrossRef]

Hadjiloucas, S.

S. Hadjiloucas, D. A. Keating, M. J. Usher, “Plastic optical fiber sensor for plant water relations,” in Proceedings of the Fifth International Conference on Plastic Optical Fibers and Applications—POF’96 (French Club Fibres Optiques Plastiques, Paris, 1996), pp. 228–237.

Harmer, A. L.

A. L. Harmer, “Optical fiber refractometer using attenuation of cladding modes,” in Proceedings of Optical Fiber Sensors 1 (Institution of Electronics Engineers, London, 1983), pp. 104–108.

Ioannides, N.

N. Ioannides, D. Kalymnios, I. W. Rogers, “Experimental and theoretical investigations of a POF based displacement sensor,” in Proceedings of the Second International Conference on Plastic Optical Fibers and Applications—POF’93 (European Institute for Communications and Networks, Geneva, 1993), pp. 162–165.

Irusta, U.

A. Aguirre, U. Irusta, J. Zubia, J. Arrue, “Fabrication of low loss POF contact couplers,” in Proceedings of the Sixth International Conference on Plastic Optical Fibers and Applications—POF’97 (Office of Naval Research, Asian Office and POF Consortium, Tokyo, Japan, 1997), pp. 132–133; J. Zubia, U. Irusta, J. Arrue, A. Aguirre, “Design and characterization of a POF active coupler,” IEEE Photon. Technol. Lett. 10, 1578–1580 (1998).

Ishigure, T.

Y. Koike, T. Ishigure, E. Nihei, “High-bandwidth graded index polymer optical fiber,” J. Lightwave Technol. 13, 1475–1489 (1995); T. Ishigure, E. Nihei, Y. Koike, C. E. Forbes, L. LaNieve, R. Straff, H. A. Deckers, “Large core, high-bandwidth polymer optical fiber for near infrared use,” IEEE Photon. Technol. Lett. 7, 403–405, (1995); E. Nihei, T. Ishigure, N. Tanio, Y. Koike, “Present prospect of graded index plastic optical fiber in telecommunication,” IEICE Trans. Electron. E-80-c, 117–122 (1997).

Kaino, T.

T. Kaino, “Polymer optical fibers,” in Polymers for Lightwave and Integrated Optics: Technology and Applications, L. A. Hornak, ed. (Marcel Dekker, New York, 1992), pp. 1–38.

Kalymnios, D.

J. Arrue, J. Zubia, G. Fuster, D. Kalymnios, “Light power behavior when bending POFs,” IEE Proc. Optoelectron. 145, 1–6, (1998); G. Garitaonaindía, J. Zubia, U. Irusta, J. Arrue, “Passive device based on POF to determine the index of refraction in liquids,” in Proceedings of the Seventh International Conference on Plastic Optical Fibers and Applications—POF’98 (International Committee of POF-ICPOF, Germany, 1998), pp. 178–184.

N. Ioannides, D. Kalymnios, I. W. Rogers, “Experimental and theoretical investigations of a POF based displacement sensor,” in Proceedings of the Second International Conference on Plastic Optical Fibers and Applications—POF’93 (European Institute for Communications and Networks, Geneva, 1993), pp. 162–165.

Keating, D. A.

S. Hadjiloucas, D. A. Keating, M. J. Usher, “Plastic optical fiber sensor for plant water relations,” in Proceedings of the Fifth International Conference on Plastic Optical Fibers and Applications—POF’96 (French Club Fibres Optiques Plastiques, Paris, 1996), pp. 228–237.

Koeppen, C.

Koike, Y.

Y. Koike, T. Ishigure, E. Nihei, “High-bandwidth graded index polymer optical fiber,” J. Lightwave Technol. 13, 1475–1489 (1995); T. Ishigure, E. Nihei, Y. Koike, C. E. Forbes, L. LaNieve, R. Straff, H. A. Deckers, “Large core, high-bandwidth polymer optical fiber for near infrared use,” IEEE Photon. Technol. Lett. 7, 403–405, (1995); E. Nihei, T. Ishigure, N. Tanio, Y. Koike, “Present prospect of graded index plastic optical fiber in telecommunication,” IEICE Trans. Electron. E-80-c, 117–122 (1997).

Kompella, J.

Liu, Y.

T. F. Stehlin, Y. Liu, “Polymer optical fiber sensors,” in Proceedings of the First International Conference on Plastic Optical Fibers and Applications—POF’92 (Information Gatekeepers, Inc., Boston, Mass., 1992), pp. 124–127.

Love, J.

A. W. Snyder, J. Love, Optical Waveguide Theory (Chapman & Hall, London, 1996).

Mateo, J.

J. J. Bayle, J. Mateo, “Plastic optical fiber sensor of refractive index, based on evanescent field,” in Proceedings of the Fifth International Conference on Plastic Optical Fibers and Applications—POF’96 (French Club Fibres Optiques Plastiques, Paris, 1996), pp. 220–227.

Morisawa, M.

M. Morisawa, S. Muto, G. Vishno, “POF sensor for detecting oxygen in air and in water,” in Proceedings of the Seventh International Conference on Plastic Optical Fibers and Applications—POF’98 (International Committee of POF-ICPOF, Germany, 1998), pp. 243–244.

Muto, S.

M. Morisawa, S. Muto, G. Vishno, “POF sensor for detecting oxygen in air and in water,” in Proceedings of the Seventh International Conference on Plastic Optical Fibers and Applications—POF’98 (International Committee of POF-ICPOF, Germany, 1998), pp. 243–244.

Nihei, E.

Y. Koike, T. Ishigure, E. Nihei, “High-bandwidth graded index polymer optical fiber,” J. Lightwave Technol. 13, 1475–1489 (1995); T. Ishigure, E. Nihei, Y. Koike, C. E. Forbes, L. LaNieve, R. Straff, H. A. Deckers, “Large core, high-bandwidth polymer optical fiber for near infrared use,” IEEE Photon. Technol. Lett. 7, 403–405, (1995); E. Nihei, T. Ishigure, N. Tanio, Y. Koike, “Present prospect of graded index plastic optical fiber in telecommunication,” IEICE Trans. Electron. E-80-c, 117–122 (1997).

Rogers, I. W.

N. Ioannides, D. Kalymnios, I. W. Rogers, “Experimental and theoretical investigations of a POF based displacement sensor,” in Proceedings of the Second International Conference on Plastic Optical Fibers and Applications—POF’93 (European Institute for Communications and Networks, Geneva, 1993), pp. 162–165.

Sharma, E.

Shi, R. F.

Singh, C. D.

B. D. Gupta, C. D. Singh, “Fiber-optic evanescent field absorption sensor: a theoretical evaluation,” Fiber Integr. Opt. 13, 433–443 (1994).
[CrossRef]

Snyder, A. W.

A. W. Snyder, J. Love, Optical Waveguide Theory (Chapman & Hall, London, 1996).

Stehlin, T. F.

T. F. Stehlin, Y. Liu, “Polymer optical fiber sensors,” in Proceedings of the First International Conference on Plastic Optical Fibers and Applications—POF’92 (Information Gatekeepers, Inc., Boston, Mass., 1992), pp. 124–127.

Usher, M. J.

S. Hadjiloucas, D. A. Keating, M. J. Usher, “Plastic optical fiber sensor for plant water relations,” in Proceedings of the Fifth International Conference on Plastic Optical Fibers and Applications—POF’96 (French Club Fibres Optiques Plastiques, Paris, 1996), pp. 228–237.

Vishno, G.

M. Morisawa, S. Muto, G. Vishno, “POF sensor for detecting oxygen in air and in water,” in Proceedings of the Seventh International Conference on Plastic Optical Fibers and Applications—POF’98 (International Committee of POF-ICPOF, Germany, 1998), pp. 243–244.

Weiss, J. D.

J. D. Weiss, “The pressure approach to fiber liquid-level sensors,” in Proceedings of the Fourth International Conference on Plastic Optical Fibers and Applications—POF’95 (European Institute for Communications and Networks, Geneva, 1995), pp. 167–170.

Yamakawa, S.

S. Yamakawa, “Plastic optical fiber chemical sensor with pencil-shaped distal tip fluorescence probe,” in Proceedings of the Sixth International Conference on Plastic Optical Fibers and Applications—POF’97 (Office of Naval Research, Asian Office and POF Consortium, Tokyo, Japan, 1997), pp. 109–110.

Yuuki, H.

K. Asada, H. Yuuki, “Fiber optic temperature sensor,” in Proceedings of the Third International Conference on Plastic Optical Fibers and Applications—POF’94 (European Institute for Communications and Networks, Geneva, 1994), pp. 49–51.

Zubia, J.

J. Arrue, J. Zubia, G. Fuster, D. Kalymnios, “Light power behavior when bending POFs,” IEE Proc. Optoelectron. 145, 1–6, (1998); G. Garitaonaindía, J. Zubia, U. Irusta, J. Arrue, “Passive device based on POF to determine the index of refraction in liquids,” in Proceedings of the Seventh International Conference on Plastic Optical Fibers and Applications—POF’98 (International Committee of POF-ICPOF, Germany, 1998), pp. 178–184.

A. Aguirre, U. Irusta, J. Zubia, J. Arrue, “Fabrication of low loss POF contact couplers,” in Proceedings of the Sixth International Conference on Plastic Optical Fibers and Applications—POF’97 (Office of Naval Research, Asian Office and POF Consortium, Tokyo, Japan, 1997), pp. 132–133; J. Zubia, U. Irusta, J. Arrue, A. Aguirre, “Design and characterization of a POF active coupler,” IEEE Photon. Technol. Lett. 10, 1578–1580 (1998).

Appl. Opt. (1)

Fiber Integr. Opt. (1)

B. D. Gupta, C. D. Singh, “Fiber-optic evanescent field absorption sensor: a theoretical evaluation,” Fiber Integr. Opt. 13, 433–443 (1994).
[CrossRef]

IEE Proc. Optoelectron. (1)

J. Arrue, J. Zubia, G. Fuster, D. Kalymnios, “Light power behavior when bending POFs,” IEE Proc. Optoelectron. 145, 1–6, (1998); G. Garitaonaindía, J. Zubia, U. Irusta, J. Arrue, “Passive device based on POF to determine the index of refraction in liquids,” in Proceedings of the Seventh International Conference on Plastic Optical Fibers and Applications—POF’98 (International Committee of POF-ICPOF, Germany, 1998), pp. 178–184.

J. Lightwave Technol. (1)

Y. Koike, T. Ishigure, E. Nihei, “High-bandwidth graded index polymer optical fiber,” J. Lightwave Technol. 13, 1475–1489 (1995); T. Ishigure, E. Nihei, Y. Koike, C. E. Forbes, L. LaNieve, R. Straff, H. A. Deckers, “Large core, high-bandwidth polymer optical fiber for near infrared use,” IEEE Photon. Technol. Lett. 7, 403–405, (1995); E. Nihei, T. Ishigure, N. Tanio, Y. Koike, “Present prospect of graded index plastic optical fiber in telecommunication,” IEICE Trans. Electron. E-80-c, 117–122 (1997).

J. Opt. Soc. Am. B (1)

Other (12)

T. F. Stehlin, Y. Liu, “Polymer optical fiber sensors,” in Proceedings of the First International Conference on Plastic Optical Fibers and Applications—POF’92 (Information Gatekeepers, Inc., Boston, Mass., 1992), pp. 124–127.

N. Ioannides, D. Kalymnios, I. W. Rogers, “Experimental and theoretical investigations of a POF based displacement sensor,” in Proceedings of the Second International Conference on Plastic Optical Fibers and Applications—POF’93 (European Institute for Communications and Networks, Geneva, 1993), pp. 162–165.

K. Asada, H. Yuuki, “Fiber optic temperature sensor,” in Proceedings of the Third International Conference on Plastic Optical Fibers and Applications—POF’94 (European Institute for Communications and Networks, Geneva, 1994), pp. 49–51.

J. D. Weiss, “The pressure approach to fiber liquid-level sensors,” in Proceedings of the Fourth International Conference on Plastic Optical Fibers and Applications—POF’95 (European Institute for Communications and Networks, Geneva, 1995), pp. 167–170.

S. Hadjiloucas, D. A. Keating, M. J. Usher, “Plastic optical fiber sensor for plant water relations,” in Proceedings of the Fifth International Conference on Plastic Optical Fibers and Applications—POF’96 (French Club Fibres Optiques Plastiques, Paris, 1996), pp. 228–237.

S. Yamakawa, “Plastic optical fiber chemical sensor with pencil-shaped distal tip fluorescence probe,” in Proceedings of the Sixth International Conference on Plastic Optical Fibers and Applications—POF’97 (Office of Naval Research, Asian Office and POF Consortium, Tokyo, Japan, 1997), pp. 109–110.

M. Morisawa, S. Muto, G. Vishno, “POF sensor for detecting oxygen in air and in water,” in Proceedings of the Seventh International Conference on Plastic Optical Fibers and Applications—POF’98 (International Committee of POF-ICPOF, Germany, 1998), pp. 243–244.

A. Aguirre, U. Irusta, J. Zubia, J. Arrue, “Fabrication of low loss POF contact couplers,” in Proceedings of the Sixth International Conference on Plastic Optical Fibers and Applications—POF’97 (Office of Naval Research, Asian Office and POF Consortium, Tokyo, Japan, 1997), pp. 132–133; J. Zubia, U. Irusta, J. Arrue, A. Aguirre, “Design and characterization of a POF active coupler,” IEEE Photon. Technol. Lett. 10, 1578–1580 (1998).

A. L. Harmer, “Optical fiber refractometer using attenuation of cladding modes,” in Proceedings of Optical Fiber Sensors 1 (Institution of Electronics Engineers, London, 1983), pp. 104–108.

J. J. Bayle, J. Mateo, “Plastic optical fiber sensor of refractive index, based on evanescent field,” in Proceedings of the Fifth International Conference on Plastic Optical Fibers and Applications—POF’96 (French Club Fibres Optiques Plastiques, Paris, 1996), pp. 220–227.

A. W. Snyder, J. Love, Optical Waveguide Theory (Chapman & Hall, London, 1996).

T. Kaino, “Polymer optical fibers,” in Polymers for Lightwave and Integrated Optics: Technology and Applications, L. A. Hornak, ed. (Marcel Dekker, New York, 1992), pp. 1–38.

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Figures (7)

Fig. 1
Fig. 1

(a) Structure of the device. (b) Parameters that characterize the behavior of the device.

Fig. 2
Fig. 2

Transverse view of the POF at the active area, showing the distribution of light foci at the entrance.

Fig. 3
Fig. 3

Relative output power P out/P in of the device for three input power distributions, uniform, Lambertian, and random, for an unbent Eska Extra POF and the following parameters: L = 3 cm, a = 0.49 mm, d = 0, ρ = ∞, and δ = ∞.

Fig. 4
Fig. 4

(a) Relative output power P out/P in as a function of the fiber numerical aperture for L = 3 cm, a = 0.49 mm, d = 0, ρ = ∞, and δ = ∞. The results correspond to a Lambertian input power distribution. The numerical apertures of the fibers were Eska F-type, 0.75; Eska Extra, 0.47; and Eska P-type, 0.90. (b) Sensitivity of the device dP rel/dn as a function of the fiber’s numerical aperture for the same parameters; P rel = P out/P in.

Fig. 5
Fig. 5

Results of the simulation. (a) Relative output power as a function of the liquid’s refractive index and of the depth of the liquid for L = 3 cm, a = 0.49 mm, d = 0, and ρ = ∞. (b) Relative output power as a function of the liquid’s refractive index and of the length of the active area for a = 0.49 mm, d = 0, ρ = ∞, and δ = ∞. The results correspond to a Lambertian input power distribution and a PMMA POF with n co = 1.492 and n cl = 1.417.

Fig. 6
Fig. 6

Comparison of experimental (squares) and simulated (circles) results for a Lambertian input power distribution and for a PMMA POF with n co = 1.492 and n cl = 1.417: (a) for L = 3 cm, a = 0.49 mm, d = 0, δ = 0.35, and ρ = ∞; (b) for L = 0.7 cm, a = 0.49 mm, d = 0, δ = 0.35, and ρ = ∞. The size of a square represents the error in the measurement.

Fig. 7
Fig. 7

Relative output power P out/P in as a function of the liquid’s refractive index and of the liquid’s depth for L = 3 cm, a = 0.49 mm, d = 0, and ρ = ∞ and for shallow liquids. The simulation conditions are the same as those for Fig. 5.

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