Complete phase-strain model for structurally embedded interferometric optical fiber sensors

James S. Sirkis; Henry W. Haslach Jr.

doi:10.1117/12.24846

1 December 1990 Complete phase-strain model for structurally embedded interferometric optical fiber sensors

James S. Sirkis, Henry W. Haslach Jr.

Proceedings Volume 1370, Fiber Optic Smart Structures and Skins III; (1990) https://doi.org/10.1117/12.24846
Event: SPIE Microelectronic Interconnect and Integrated Processing Symposium, 1990, San Jose, United States

Abstract

The relation between a three-dimensional state of strain and the optical phase retardation in a single mode optical fiber is formalized. Neumann's strain optic relations are combined with weakly guiding fiber theory to develop an integral which relates the optical phase shift in a structurally embedded interferometric optical fiber strain sensor to the induced three dimensional strain field. The phase-strain integral is general in that it governs the phase shift in an arbitrarily configured optical fiber sensor experiencing a spatially varying three-dimensional strain field. It is shown that under the correct assumptions Butter and Hocker's [1] equation can be recovered. The phase-strain model is then used to predict the phase shift produced in a straight fiber sensor embedded in a uniaxial tension specimen when the fiber is aligned parallel and perpendicular to the direction of load. The solutions are used to assess the influence of the waveguide dispersion on the total optical phase shift. This process leads to a previously undisclosed waveguide dispersion term which contributes on the same order to the total strain induced phase retardation as does Butter and Hocker's [111 original term. Still, however, waveguide dispersion effects are found to be negligibly small, even in three dimensional loading. Finally, it is shown that in certain cases, the Butter and Hocker's [1] equation and the complete phase-strain model developed herein can give very similar results when both are applied to embedded sensors. This anomaly can lead to the false conclusion that Butter and Hocker's results are equally valid for arbitrary embedded sensors.

Citation Download Citation

James S. Sirkis and Henry W. Haslach Jr. "Complete phase-strain model for structurally embedded interferometric optical fiber sensors", Proc. SPIE 1370, Fiber Optic Smart Structures and Skins III, (1 December 1990); https://doi.org/10.1117/12.24846

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