Abstract

A simple and compact reflective liquid level sensor based on modes conversion in the thin-core fiber incorporating one tilted fiber Bragg grating (TFBG) is proposed and experimentally demonstrated. A piece of thin-core fiber containing one TFBG ensures the modes conversion between the core mode and cladding modes. The external liquid can induce the cladding modes covert to the radiation modes and lead to the decrement of the collected cladding modes power, then the liquid level can be measured from the collected cladding modes power. The modes conversion in the proposed structure is theoretically analyzed. The experimental results show the high liquid level sensitivity and temperature immunity of the proposed sensor, and its significant advantage is that the measurement range is not limited to the length of the TFBG itself.

© 2014 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. K. O. Hill, G. Meltz, “Fiber Bragg grating technology fundamentals and overview,” J. Lightwave Technol. 15(8), 1263–1276 (1997).
    [CrossRef]
  2. J. Albert, L. Y. Shao, C. Caucheteur, “Tilted fiber Bragg grating sensors,” Laser Photonics Rev. 7(1), 83–108 (2013).
    [CrossRef]
  3. B. Gu, W. Qi, J. Zheng, Y. Zhou, P. P. Shum, F. Luan, “Simple and compact reflective refractometer based on tilted fiber Bragg grating inscribed in thin-core fiber,” Opt. Lett. 39(1), 22–25 (2014).
    [CrossRef] [PubMed]
  4. L. Rindorf, J. B. Jensen, M. Dufva, L. H. Pedersen, P. E. Høiby, O. Bang, “Photonic crystal fiber long-period gratings for biochemical sensing,” Opt. Express 14(18), 8224–8231 (2006).
    [CrossRef] [PubMed]
  5. G. F. Yan, A. P. Zhang, G. Y. Ma, B. H. Wang, B. Kim, J. Im, S. L. He, Y. Chung, “Fiber-optic acetylene gas sensor based on microstructured optical fiber Bragg gratings,” IEEE Photon. Technol. Lett. 23(21), 1588–1590 (2011).
    [CrossRef]
  6. B. Gu, M. J. Yin, A. P. Zhang, J. W. Qian, S. L. He, “Optical fiber relative humidity sensor based on FBG incorporated thin-core fiber modal interferometer,” Opt. Express 19(5), 4140–4146 (2011).
    [CrossRef] [PubMed]
  7. B. F. Yun, N. Chen, Y. P. Cui, “Highly sensitive liquid-level sensor based on etched fiber Bragg grating,” IEEE Photon. Technol. Lett. 19(21), 1747–1749 (2007).
    [CrossRef]
  8. T. Guo, Q. D. Zhao, Q. Y. Dou, H. Zhang, L. F. Xue, G. L. Huang, X. Y. Dong, “Temperature-insensitive fiber Bragg grating liquid-level sensor based on bending cantilever beam,” IEEE Photon. Technol. Lett. 17(11), 2400–2402 (2005).
    [CrossRef]
  9. S. Khaliq, S. W. James, R. P. Tatam, “Fiber-optic liquid-level sensor using a long-period grating,” Opt. Lett. 26(16), 1224–1226 (2001).
    [CrossRef] [PubMed]
  10. H. Y. Fu, X. W. Shu, A. P. Zhang, W. S. Liu, L. Zhang, S. L. He, I. Bennion, “Implementation and characterization of liquid-level sensor based on a long-period fiber grating Mach-Zehnder interferometer,” IEEE Sens. J. 11(11), 2878–2882 (2011).
    [CrossRef]
  11. Q. Jiang, D. B. Hu, M. Yang, “Simultaneous measurement of liquid level and surrounding refractive index using tilted fiber Bragg grating,” Sensor Actuat. A 170(1–2), 62–65 (2011).
    [CrossRef]
  12. A. F. Obaton, G. Laffont, C. Wang, A. Allard, P. Ferdinand, “Tilted fibre Bragg gratings and phase sensitive-optical low coherence interferometry for refractometry and liquid level sensing,” Sensor Actuat. A 189, 451–458 (2013).
    [CrossRef]
  13. C. B. Mou, K. M. Zhou, Z. J. Yan, H. Y. Fu, L. Zhang, “Liquid level sensor based on an excessively tilted fibre grating,” Opt. Commun. 305, 271–275 (2013).
    [CrossRef]
  14. The International Association for the Properties of Water and Steam, “Release on the refractive index of ordinary water substance as a function of wavelength, temperature and pressure,” IAPWS, Erlangen, 1–7 (1997).

2014 (1)

2013 (3)

J. Albert, L. Y. Shao, C. Caucheteur, “Tilted fiber Bragg grating sensors,” Laser Photonics Rev. 7(1), 83–108 (2013).
[CrossRef]

A. F. Obaton, G. Laffont, C. Wang, A. Allard, P. Ferdinand, “Tilted fibre Bragg gratings and phase sensitive-optical low coherence interferometry for refractometry and liquid level sensing,” Sensor Actuat. A 189, 451–458 (2013).
[CrossRef]

C. B. Mou, K. M. Zhou, Z. J. Yan, H. Y. Fu, L. Zhang, “Liquid level sensor based on an excessively tilted fibre grating,” Opt. Commun. 305, 271–275 (2013).
[CrossRef]

2011 (4)

G. F. Yan, A. P. Zhang, G. Y. Ma, B. H. Wang, B. Kim, J. Im, S. L. He, Y. Chung, “Fiber-optic acetylene gas sensor based on microstructured optical fiber Bragg gratings,” IEEE Photon. Technol. Lett. 23(21), 1588–1590 (2011).
[CrossRef]

H. Y. Fu, X. W. Shu, A. P. Zhang, W. S. Liu, L. Zhang, S. L. He, I. Bennion, “Implementation and characterization of liquid-level sensor based on a long-period fiber grating Mach-Zehnder interferometer,” IEEE Sens. J. 11(11), 2878–2882 (2011).
[CrossRef]

Q. Jiang, D. B. Hu, M. Yang, “Simultaneous measurement of liquid level and surrounding refractive index using tilted fiber Bragg grating,” Sensor Actuat. A 170(1–2), 62–65 (2011).
[CrossRef]

B. Gu, M. J. Yin, A. P. Zhang, J. W. Qian, S. L. He, “Optical fiber relative humidity sensor based on FBG incorporated thin-core fiber modal interferometer,” Opt. Express 19(5), 4140–4146 (2011).
[CrossRef] [PubMed]

2007 (1)

B. F. Yun, N. Chen, Y. P. Cui, “Highly sensitive liquid-level sensor based on etched fiber Bragg grating,” IEEE Photon. Technol. Lett. 19(21), 1747–1749 (2007).
[CrossRef]

2006 (1)

2005 (1)

T. Guo, Q. D. Zhao, Q. Y. Dou, H. Zhang, L. F. Xue, G. L. Huang, X. Y. Dong, “Temperature-insensitive fiber Bragg grating liquid-level sensor based on bending cantilever beam,” IEEE Photon. Technol. Lett. 17(11), 2400–2402 (2005).
[CrossRef]

2001 (1)

1997 (1)

K. O. Hill, G. Meltz, “Fiber Bragg grating technology fundamentals and overview,” J. Lightwave Technol. 15(8), 1263–1276 (1997).
[CrossRef]

Albert, J.

J. Albert, L. Y. Shao, C. Caucheteur, “Tilted fiber Bragg grating sensors,” Laser Photonics Rev. 7(1), 83–108 (2013).
[CrossRef]

Allard, A.

A. F. Obaton, G. Laffont, C. Wang, A. Allard, P. Ferdinand, “Tilted fibre Bragg gratings and phase sensitive-optical low coherence interferometry for refractometry and liquid level sensing,” Sensor Actuat. A 189, 451–458 (2013).
[CrossRef]

Bang, O.

Bennion, I.

H. Y. Fu, X. W. Shu, A. P. Zhang, W. S. Liu, L. Zhang, S. L. He, I. Bennion, “Implementation and characterization of liquid-level sensor based on a long-period fiber grating Mach-Zehnder interferometer,” IEEE Sens. J. 11(11), 2878–2882 (2011).
[CrossRef]

Caucheteur, C.

J. Albert, L. Y. Shao, C. Caucheteur, “Tilted fiber Bragg grating sensors,” Laser Photonics Rev. 7(1), 83–108 (2013).
[CrossRef]

Chen, N.

B. F. Yun, N. Chen, Y. P. Cui, “Highly sensitive liquid-level sensor based on etched fiber Bragg grating,” IEEE Photon. Technol. Lett. 19(21), 1747–1749 (2007).
[CrossRef]

Chung, Y.

G. F. Yan, A. P. Zhang, G. Y. Ma, B. H. Wang, B. Kim, J. Im, S. L. He, Y. Chung, “Fiber-optic acetylene gas sensor based on microstructured optical fiber Bragg gratings,” IEEE Photon. Technol. Lett. 23(21), 1588–1590 (2011).
[CrossRef]

Cui, Y. P.

B. F. Yun, N. Chen, Y. P. Cui, “Highly sensitive liquid-level sensor based on etched fiber Bragg grating,” IEEE Photon. Technol. Lett. 19(21), 1747–1749 (2007).
[CrossRef]

Dong, X. Y.

T. Guo, Q. D. Zhao, Q. Y. Dou, H. Zhang, L. F. Xue, G. L. Huang, X. Y. Dong, “Temperature-insensitive fiber Bragg grating liquid-level sensor based on bending cantilever beam,” IEEE Photon. Technol. Lett. 17(11), 2400–2402 (2005).
[CrossRef]

Dou, Q. Y.

T. Guo, Q. D. Zhao, Q. Y. Dou, H. Zhang, L. F. Xue, G. L. Huang, X. Y. Dong, “Temperature-insensitive fiber Bragg grating liquid-level sensor based on bending cantilever beam,” IEEE Photon. Technol. Lett. 17(11), 2400–2402 (2005).
[CrossRef]

Dufva, M.

Ferdinand, P.

A. F. Obaton, G. Laffont, C. Wang, A. Allard, P. Ferdinand, “Tilted fibre Bragg gratings and phase sensitive-optical low coherence interferometry for refractometry and liquid level sensing,” Sensor Actuat. A 189, 451–458 (2013).
[CrossRef]

Fu, H. Y.

C. B. Mou, K. M. Zhou, Z. J. Yan, H. Y. Fu, L. Zhang, “Liquid level sensor based on an excessively tilted fibre grating,” Opt. Commun. 305, 271–275 (2013).
[CrossRef]

H. Y. Fu, X. W. Shu, A. P. Zhang, W. S. Liu, L. Zhang, S. L. He, I. Bennion, “Implementation and characterization of liquid-level sensor based on a long-period fiber grating Mach-Zehnder interferometer,” IEEE Sens. J. 11(11), 2878–2882 (2011).
[CrossRef]

Gu, B.

Guo, T.

T. Guo, Q. D. Zhao, Q. Y. Dou, H. Zhang, L. F. Xue, G. L. Huang, X. Y. Dong, “Temperature-insensitive fiber Bragg grating liquid-level sensor based on bending cantilever beam,” IEEE Photon. Technol. Lett. 17(11), 2400–2402 (2005).
[CrossRef]

He, S. L.

H. Y. Fu, X. W. Shu, A. P. Zhang, W. S. Liu, L. Zhang, S. L. He, I. Bennion, “Implementation and characterization of liquid-level sensor based on a long-period fiber grating Mach-Zehnder interferometer,” IEEE Sens. J. 11(11), 2878–2882 (2011).
[CrossRef]

G. F. Yan, A. P. Zhang, G. Y. Ma, B. H. Wang, B. Kim, J. Im, S. L. He, Y. Chung, “Fiber-optic acetylene gas sensor based on microstructured optical fiber Bragg gratings,” IEEE Photon. Technol. Lett. 23(21), 1588–1590 (2011).
[CrossRef]

B. Gu, M. J. Yin, A. P. Zhang, J. W. Qian, S. L. He, “Optical fiber relative humidity sensor based on FBG incorporated thin-core fiber modal interferometer,” Opt. Express 19(5), 4140–4146 (2011).
[CrossRef] [PubMed]

Hill, K. O.

K. O. Hill, G. Meltz, “Fiber Bragg grating technology fundamentals and overview,” J. Lightwave Technol. 15(8), 1263–1276 (1997).
[CrossRef]

Høiby, P. E.

Hu, D. B.

Q. Jiang, D. B. Hu, M. Yang, “Simultaneous measurement of liquid level and surrounding refractive index using tilted fiber Bragg grating,” Sensor Actuat. A 170(1–2), 62–65 (2011).
[CrossRef]

Huang, G. L.

T. Guo, Q. D. Zhao, Q. Y. Dou, H. Zhang, L. F. Xue, G. L. Huang, X. Y. Dong, “Temperature-insensitive fiber Bragg grating liquid-level sensor based on bending cantilever beam,” IEEE Photon. Technol. Lett. 17(11), 2400–2402 (2005).
[CrossRef]

Im, J.

G. F. Yan, A. P. Zhang, G. Y. Ma, B. H. Wang, B. Kim, J. Im, S. L. He, Y. Chung, “Fiber-optic acetylene gas sensor based on microstructured optical fiber Bragg gratings,” IEEE Photon. Technol. Lett. 23(21), 1588–1590 (2011).
[CrossRef]

James, S. W.

Jensen, J. B.

Jiang, Q.

Q. Jiang, D. B. Hu, M. Yang, “Simultaneous measurement of liquid level and surrounding refractive index using tilted fiber Bragg grating,” Sensor Actuat. A 170(1–2), 62–65 (2011).
[CrossRef]

Khaliq, S.

Kim, B.

G. F. Yan, A. P. Zhang, G. Y. Ma, B. H. Wang, B. Kim, J. Im, S. L. He, Y. Chung, “Fiber-optic acetylene gas sensor based on microstructured optical fiber Bragg gratings,” IEEE Photon. Technol. Lett. 23(21), 1588–1590 (2011).
[CrossRef]

Laffont, G.

A. F. Obaton, G. Laffont, C. Wang, A. Allard, P. Ferdinand, “Tilted fibre Bragg gratings and phase sensitive-optical low coherence interferometry for refractometry and liquid level sensing,” Sensor Actuat. A 189, 451–458 (2013).
[CrossRef]

Liu, W. S.

H. Y. Fu, X. W. Shu, A. P. Zhang, W. S. Liu, L. Zhang, S. L. He, I. Bennion, “Implementation and characterization of liquid-level sensor based on a long-period fiber grating Mach-Zehnder interferometer,” IEEE Sens. J. 11(11), 2878–2882 (2011).
[CrossRef]

Luan, F.

Ma, G. Y.

G. F. Yan, A. P. Zhang, G. Y. Ma, B. H. Wang, B. Kim, J. Im, S. L. He, Y. Chung, “Fiber-optic acetylene gas sensor based on microstructured optical fiber Bragg gratings,” IEEE Photon. Technol. Lett. 23(21), 1588–1590 (2011).
[CrossRef]

Meltz, G.

K. O. Hill, G. Meltz, “Fiber Bragg grating technology fundamentals and overview,” J. Lightwave Technol. 15(8), 1263–1276 (1997).
[CrossRef]

Mou, C. B.

C. B. Mou, K. M. Zhou, Z. J. Yan, H. Y. Fu, L. Zhang, “Liquid level sensor based on an excessively tilted fibre grating,” Opt. Commun. 305, 271–275 (2013).
[CrossRef]

Obaton, A. F.

A. F. Obaton, G. Laffont, C. Wang, A. Allard, P. Ferdinand, “Tilted fibre Bragg gratings and phase sensitive-optical low coherence interferometry for refractometry and liquid level sensing,” Sensor Actuat. A 189, 451–458 (2013).
[CrossRef]

Pedersen, L. H.

Qi, W.

Qian, J. W.

Rindorf, L.

Shao, L. Y.

J. Albert, L. Y. Shao, C. Caucheteur, “Tilted fiber Bragg grating sensors,” Laser Photonics Rev. 7(1), 83–108 (2013).
[CrossRef]

Shu, X. W.

H. Y. Fu, X. W. Shu, A. P. Zhang, W. S. Liu, L. Zhang, S. L. He, I. Bennion, “Implementation and characterization of liquid-level sensor based on a long-period fiber grating Mach-Zehnder interferometer,” IEEE Sens. J. 11(11), 2878–2882 (2011).
[CrossRef]

Shum, P. P.

Tatam, R. P.

Wang, B. H.

G. F. Yan, A. P. Zhang, G. Y. Ma, B. H. Wang, B. Kim, J. Im, S. L. He, Y. Chung, “Fiber-optic acetylene gas sensor based on microstructured optical fiber Bragg gratings,” IEEE Photon. Technol. Lett. 23(21), 1588–1590 (2011).
[CrossRef]

Wang, C.

A. F. Obaton, G. Laffont, C. Wang, A. Allard, P. Ferdinand, “Tilted fibre Bragg gratings and phase sensitive-optical low coherence interferometry for refractometry and liquid level sensing,” Sensor Actuat. A 189, 451–458 (2013).
[CrossRef]

Xue, L. F.

T. Guo, Q. D. Zhao, Q. Y. Dou, H. Zhang, L. F. Xue, G. L. Huang, X. Y. Dong, “Temperature-insensitive fiber Bragg grating liquid-level sensor based on bending cantilever beam,” IEEE Photon. Technol. Lett. 17(11), 2400–2402 (2005).
[CrossRef]

Yan, G. F.

G. F. Yan, A. P. Zhang, G. Y. Ma, B. H. Wang, B. Kim, J. Im, S. L. He, Y. Chung, “Fiber-optic acetylene gas sensor based on microstructured optical fiber Bragg gratings,” IEEE Photon. Technol. Lett. 23(21), 1588–1590 (2011).
[CrossRef]

Yan, Z. J.

C. B. Mou, K. M. Zhou, Z. J. Yan, H. Y. Fu, L. Zhang, “Liquid level sensor based on an excessively tilted fibre grating,” Opt. Commun. 305, 271–275 (2013).
[CrossRef]

Yang, M.

Q. Jiang, D. B. Hu, M. Yang, “Simultaneous measurement of liquid level and surrounding refractive index using tilted fiber Bragg grating,” Sensor Actuat. A 170(1–2), 62–65 (2011).
[CrossRef]

Yin, M. J.

Yun, B. F.

B. F. Yun, N. Chen, Y. P. Cui, “Highly sensitive liquid-level sensor based on etched fiber Bragg grating,” IEEE Photon. Technol. Lett. 19(21), 1747–1749 (2007).
[CrossRef]

Zhang, A. P.

B. Gu, M. J. Yin, A. P. Zhang, J. W. Qian, S. L. He, “Optical fiber relative humidity sensor based on FBG incorporated thin-core fiber modal interferometer,” Opt. Express 19(5), 4140–4146 (2011).
[CrossRef] [PubMed]

G. F. Yan, A. P. Zhang, G. Y. Ma, B. H. Wang, B. Kim, J. Im, S. L. He, Y. Chung, “Fiber-optic acetylene gas sensor based on microstructured optical fiber Bragg gratings,” IEEE Photon. Technol. Lett. 23(21), 1588–1590 (2011).
[CrossRef]

H. Y. Fu, X. W. Shu, A. P. Zhang, W. S. Liu, L. Zhang, S. L. He, I. Bennion, “Implementation and characterization of liquid-level sensor based on a long-period fiber grating Mach-Zehnder interferometer,” IEEE Sens. J. 11(11), 2878–2882 (2011).
[CrossRef]

Zhang, H.

T. Guo, Q. D. Zhao, Q. Y. Dou, H. Zhang, L. F. Xue, G. L. Huang, X. Y. Dong, “Temperature-insensitive fiber Bragg grating liquid-level sensor based on bending cantilever beam,” IEEE Photon. Technol. Lett. 17(11), 2400–2402 (2005).
[CrossRef]

Zhang, L.

C. B. Mou, K. M. Zhou, Z. J. Yan, H. Y. Fu, L. Zhang, “Liquid level sensor based on an excessively tilted fibre grating,” Opt. Commun. 305, 271–275 (2013).
[CrossRef]

H. Y. Fu, X. W. Shu, A. P. Zhang, W. S. Liu, L. Zhang, S. L. He, I. Bennion, “Implementation and characterization of liquid-level sensor based on a long-period fiber grating Mach-Zehnder interferometer,” IEEE Sens. J. 11(11), 2878–2882 (2011).
[CrossRef]

Zhao, Q. D.

T. Guo, Q. D. Zhao, Q. Y. Dou, H. Zhang, L. F. Xue, G. L. Huang, X. Y. Dong, “Temperature-insensitive fiber Bragg grating liquid-level sensor based on bending cantilever beam,” IEEE Photon. Technol. Lett. 17(11), 2400–2402 (2005).
[CrossRef]

Zheng, J.

Zhou, K. M.

C. B. Mou, K. M. Zhou, Z. J. Yan, H. Y. Fu, L. Zhang, “Liquid level sensor based on an excessively tilted fibre grating,” Opt. Commun. 305, 271–275 (2013).
[CrossRef]

Zhou, Y.

IEEE Photon. Technol. Lett. (3)

G. F. Yan, A. P. Zhang, G. Y. Ma, B. H. Wang, B. Kim, J. Im, S. L. He, Y. Chung, “Fiber-optic acetylene gas sensor based on microstructured optical fiber Bragg gratings,” IEEE Photon. Technol. Lett. 23(21), 1588–1590 (2011).
[CrossRef]

B. F. Yun, N. Chen, Y. P. Cui, “Highly sensitive liquid-level sensor based on etched fiber Bragg grating,” IEEE Photon. Technol. Lett. 19(21), 1747–1749 (2007).
[CrossRef]

T. Guo, Q. D. Zhao, Q. Y. Dou, H. Zhang, L. F. Xue, G. L. Huang, X. Y. Dong, “Temperature-insensitive fiber Bragg grating liquid-level sensor based on bending cantilever beam,” IEEE Photon. Technol. Lett. 17(11), 2400–2402 (2005).
[CrossRef]

IEEE Sens. J. (1)

H. Y. Fu, X. W. Shu, A. P. Zhang, W. S. Liu, L. Zhang, S. L. He, I. Bennion, “Implementation and characterization of liquid-level sensor based on a long-period fiber grating Mach-Zehnder interferometer,” IEEE Sens. J. 11(11), 2878–2882 (2011).
[CrossRef]

J. Lightwave Technol. (1)

K. O. Hill, G. Meltz, “Fiber Bragg grating technology fundamentals and overview,” J. Lightwave Technol. 15(8), 1263–1276 (1997).
[CrossRef]

Laser Photonics Rev. (1)

J. Albert, L. Y. Shao, C. Caucheteur, “Tilted fiber Bragg grating sensors,” Laser Photonics Rev. 7(1), 83–108 (2013).
[CrossRef]

Opt. Commun. (1)

C. B. Mou, K. M. Zhou, Z. J. Yan, H. Y. Fu, L. Zhang, “Liquid level sensor based on an excessively tilted fibre grating,” Opt. Commun. 305, 271–275 (2013).
[CrossRef]

Opt. Express (2)

Opt. Lett. (2)

Sensor Actuat. A (2)

Q. Jiang, D. B. Hu, M. Yang, “Simultaneous measurement of liquid level and surrounding refractive index using tilted fiber Bragg grating,” Sensor Actuat. A 170(1–2), 62–65 (2011).
[CrossRef]

A. F. Obaton, G. Laffont, C. Wang, A. Allard, P. Ferdinand, “Tilted fibre Bragg gratings and phase sensitive-optical low coherence interferometry for refractometry and liquid level sensing,” Sensor Actuat. A 189, 451–458 (2013).
[CrossRef]

Other (1)

The International Association for the Properties of Water and Steam, “Release on the refractive index of ordinary water substance as a function of wavelength, temperature and pressure,” IAPWS, Erlangen, 1–7 (1997).

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (5)

Fig. 1
Fig. 1

Schematic configuration of the liquid level sensing setup (a) and the reflective liquid level sensor (b), and the microscope image of the splicing region between two different fibers (c).

Fig. 2
Fig. 2

Amplitude distribution of the light propagating along the SMF and UHNA when the surrounding media is air (a) and the different UHNA section is immersed into the RI solution. (b) Z = 6000 to 7000 μm, (c) Z = 4000 to 7000 μm, (d) Z = 2000 to 7000 μm.

Fig. 3
Fig. 3

Reflection spectrum of the proposed reflective liquid level sensor.

Fig. 4
Fig. 4

Response of the reflective liquid level sensor versus the external RI (a) and temperature (b). Insets show the measured reflection spectra.

Fig. 5
Fig. 5

Response of the reflective sensor versus liquid level. Inset shows the measured reflection spectra.

Metrics