Claudio Egalon - Academia.edu (original) (raw)
Papers by Claudio Egalon
Abstract. The behavior of the power efficiency, Peff, of an optical fiber with a thin-film source... more Abstract. The behavior of the power efficiency, Peff, of an optical fiber
with a thin-film source distributed in the core/cladding interlace is analyzed. The expressions derived make use of the exact field solution of a cylindrical fiber, whereas previous work has made use of the weakly guiding approximation. Although more complicated and harder to interpret, the formulas presented allow the analysis of the power injection efficiency of fibers with arbitrary differences in indices of refraction. The results obtained are relevant to the design of more efficient optical fiber fluorosensors. In this work, some results using the weakly guiding approximation were confirmed. However, in contrast to the weakly guidingwork, we have found that Peft does not always increase with the V number.It was found that Peff always increases with the difference in the indices of refraction, flcore cIad, and varies only slightly with the wavelength, X, and the fiber core radius, a. Finally, by varying a and X in such a way as to make their ratio, a/A, constant, it was found that Peff 5 also constant. This indicates that a/l. is a new independent variable.
Optical Engineering, 1994
Experiments were conducted to verify a theoretical model on the injection efficiency of sources i... more Experiments were conducted to verify a theoretical model on the injection efficiency of sources in the cladding of an optical fiber. The theoretical results predicted an increase in the injection efficiency for higher differences in refractive indices between the core and cladding. The experimental apparatus used consisted of a glass rod 50 cm long, coated at one end with a thin film of fluorescent substance. The fluorescent substance was excited with side illumination, perpendicular to the rod axis, using a 476 nm Argon-ion laser. Part of the excited fluorescence was injected into the core and guided to a detector. The signal was measured for several different cladding refractive indices. The cladding consisted of sugar dissolved in water and the refractive index was changed by varying the sugar concentration in the solution. The results indicate that the power injected into the rod, due to evanescent wave injection, increases with the difference in refractive index which is in qualitative agreement with theory.
Optical fibers may have applications including fluorosensors which sense the concentration of an ... more Optical fibers may have applications including fluorosensors which sense the concentration of an analyte. Like communication fibers, these fluorosensors are modeled using a weakly guiding approximation which is only effective when the difference between the respective refractive indices of the fiber core and surrounding cladding are minimal. An optical fiber fluorosensor is provided having a portion of a fiber core which is surrounded by an active cladding which is permeable by the analyte to be sensed and containing substances which emit light waves upon excitation. A remaining portion of the fiber core is surrounded by a guide cladding which guides these light waves to a sensor which detects the intensity of waves, which is a function of the analyte concentration. Contrary to conventional weakly guiding principles, the difference between the respective indices of refraction of the fiber core is surrounded by an active cladding which is thin enough such that its index of refraction is effectively that of the surrounding atmosphere, thereby the atmosphere guides the injective indices of the fiber core and the cladding results in an unexpected increase in the power efficiency of the fiber core.
Optical Engineering, 1992
The exact field solution of a step-index profile fiber was used to determine the injection effici... more The exact field solution of a step-index profile fiber was used to determine the injection efficiency of a thin-film distribution of polarized sources located in the cladding of an optical fiber. Previous results for random source orientation were confirmed. The behavior of the power efficiency, P(eff), of a polarized distribution of sources was found to be similar to the behavior of a fiber with sources with random orientation. However, for sources polarized in either the x or y direction, P(eff) was found to be more efficient.
Optical Engineering, 1997
A reformulation of the asymptotic solution of the coupled-mode equations with a periodic variatio... more A reformulation of the asymptotic solution of the coupled-mode equations with a periodic variation of the refractive index along the propagation length is presented. A first-order correction using the asymptotic solution and Piccard's method are also determined. It is found that the first-order solution compares very well with the numerical solution throughout a wide range of coupling parameters. The key differences between the method presented here and elsewhere reside in the derivation of the asymptotic solution as well as in the careful derivation of the higher order corrections.
A strain sensor uses an optical fiber including a strain sensitive portion and at least one strai... more A strain sensor uses an optical fiber including a strain sensitive portion and at least one strain insensitive portion. The strain sensitive portion is mounted on the surface of a structure at a location where a strain is desired to be measured. The strain insensitive portion(s) may be fused to the strain sensitive portion to transmit light therethrough, so that the resulting pattern may be detected to determine the amount of strain by comparison with a similar fiber not subjected to strain, or with the light pattern produced when the fiber is not under strain.
Two distributed fiber optic sensors for use in the prevention and monitoring of corrosion in airc... more Two distributed fiber optic sensors for use in the prevention and monitoring of corrosion in aircraft are described. These sensors, based on optical fibers that are intrinsically sensitive to either water or changes in pH, will alert maintenance personnel to the presence of water in lap joints and other inaccessible critical areas. Furthermore, the sensors can also locate precisely where the moisture infiltration has occurred. In a typical application, a sensor fiber would be embedded in a lap joint along the bottom panel of an aircraft's body, or on a wing, where water is likely to collect. Changes in the optical transmission through the fiber can be monitored either periodically or continuously to determine the extent of water penetration.
Experiments were conducted to verify a theoretical model on the injection efficiency of sources i... more Experiments were conducted to verify a theoretical model on the injection efficiency of sources in the cladding of an optical fiber. The theoretical results predicted an increase in the injection efficiency for higher differences in refractive indices between the core and cladding. The experimental apparatus used consisted of a glass rod 50 cm long, coated at one end with a thin film of fluorescent substance. The fluorescent substance was excited with side illumination, perpendicular to the rod axis, using a 476 nm Argon-ion laser. Part of the excited fluorescence was injected into the core and guided to a detector. The signal was measured for several different cladding refractive indices. The cladding consisted of sugar dissolved in water and the refractive index was changed by varying the sugar concentration in the solution. The results indicate that the power injected into the rod, due to evanescent wave injection, increases with the difference in refractive index which is in qualitative agreement with theory.
Optical Engineering, 1995
Modeling an evanescent field absorption optical fiber sensor. [Proceedings of SPIE 2508, 368 (199... more Modeling an evanescent field absorption optical fiber sensor. [Proceedings of SPIE 2508, 368 (1995)]. Claudio O. Egalon, Edgar A. Mendoza, Albert N. Khalil, Robert A. Lieberman. Abstract. Using the weakly guiding and exact ...
Optical Engineering, 1995
Using the weakly guiding and exact field solutions of an optical fiber, we wrote a FORTRAN progra... more Using the weakly guiding and exact field solutions of an optical fiber, we wrote a FORTRAN program to determine the fractional power that reaches the end of an optical fiber with an absorptive cladding. We have assumed that each mode of the fiber is equally excited. This corresponds to incoherent source excitation. The results were compared to a previous approximation published by Payne and Hale in 1993. We have found that, at low V-numbers, V equals 20, Payne and Hale's approximation deviate by more than 20% from the weakly guiding solution. At high V-numbers, the approximation deviates by less than 10%. When compared to Payne and Hale's approximation, both the weakly guiding and exact solutions are close to the data points obtained experimentally by Degrandpre and Burgess in 1988. Although closer than Payne and Hale's approximation, our solution still deviates from the Degrandpre and Burgess results. The difference may result from the assumption that all modes were excited equally. Another possibility was the fact that we have neglected leaky modes in our treatment.
Using the weakly guiding and exact field solutions of an optical fiber, we wrote a FORTRAN progra... more Using the weakly guiding and exact field solutions of an optical fiber, we wrote a FORTRAN program to determine the fractional power that reaches the end of an optical fiber with an absorptive cladding. We have assumed that each mode of the fiber is equally excited. This corresponds to incoherent source excitation. The results were compared to a previous approximations published in the literature. We have found that, at low V-numbers, V < 20, Payne and Hale's approximation deviate by more than 20% from the weakly guiding solution. At high V-numbers, the approximation deviated by less than 10%. When compared to Payne and Hale's approximation, both the weakly guiding and exact solutions are closer to the data points obtained experimentally by Degrandpre and Burgess. Although closer than Payne and Hale's approximation, our solution still deviates from Degrandpre and Burgess' results. The difference may be due to the assumption that all modes were excited equally. Another possibility was the fact that we have neglected leaky modes in our treatment.
A strain sensor is constructed from a two mode optical fiber. When the optical fiber is surface m... more A strain sensor is constructed from a two mode optical fiber. When the optical fiber is surface mounted in a straight line and the object to which the optical fiber is mounted is subjected to strain within a predetermined range, the light intensity of any point at the output of the optical fiber will have a linear relationship to strain, provided the intermodal phase difference is less than 0.17 radians.
Optical Engineering, 1992
The analytical treatment of power efficiency (P(eff) is undertaken for the case of a positively g... more The analytical treatment of power efficiency (P(eff) is undertaken for the case of a positively guiding optical fiber with a thin-film source distributed in the core-cladding interface. The approach adopts the exact solution of the cylindrical optical fiber with an infinite cladding to account for differences between the indices of refraction of the core and the cladding. The excitation of low-loss leaky modes by the cladding is ignored, and only the injection by the evanescent field is considered. The formulas permit the analysis of the power-injection efficiency of fibers with arbitrary differences in indices of refraction. P(eff) does not always increase with V number, but rather varies slightly with wavelength and fiber-core radius and varies significantly with the difference in the indices of refraction. The theoretical results of the work are of interest for designing an atomic-O chemical sensor based on evanescent-wave coupling.
Optical Engineering, 1992
The behavior of the power efficiency of an optical fiber with bulk distribution of sources in its... more The behavior of the power efficiency of an optical fiber with bulk distribution of sources in its cladding is analyzed. Marcuse&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s (1988) results for weakly guiding cylindrical fibers with fluorescent sources uniformly distributed in the cladding are confirmed for the bulk distribution case. It is found that power efficiency increases with wavelength and with difference in refractive indices. A new independent variable for the bulk distribution is found, and it is shown that the power efficiency does not always increase with the V number.
Optical Engineering, 1992
Axial strain can be determined by monitoring the modal pattern variation of an optical fiber. The... more Axial strain can be determined by monitoring the modal pattern variation of an optical fiber. The results of a numerical model developed to calculate the modal pattern variation at the end of a weakly guiding optical fiber under axial strain is presented. Whenever an optical fiber is under stress, the optical path length, the index of refraction, and the propagation constants of each fiber mode change. In consequence, the modal phase term for the fields and the fiber output pattern are also modified. For multimode fibers, very complicated patterns result. The predicted patterns are presented, and an expression for the phase variation with strain is derived.
Optical Engineering, 1994
A numerical model was developed to calculate the modal phase shift of a circular step index profi... more A numerical model was developed to calculate the modal phase shift of a circular step index profile weakly guiding optical fiber under axial strain. Whenever an optical fiber is under stress, the optical path length, the index of refraction, and the propagation constants of each mode change. In consequence, the phase of each mode is also modified. A relationship for the modal phase shift is presented. This relation is applied to both single-mode and two-mode fibers to determine the sensitivity characteristics of strained fibers. It was found that the phase shift is strongly dependent on the core refractive index nco. It was also found that it is possible to design fibers that are insensitive to axial strain. Practical applications of strain- insensitive fibers are discussed.
Optical Engineering, 1992
The exact field solution of a step-index profile fiber is used to determine the excitation effici... more The exact field solution of a step-index profile fiber is used to determine the excitation efficiency of a distribution of sources in the core of an optical fiber. Previous results of a thin-film cladding source distribution to its core source counterpart are used for comparison. The behavior of power efficiency with the fiber parameters is examined and found to be
Journal of The Optical Society of America B-optical Physics, 1995
Experiments were conducted to quantify the amount of light injected from a thin film of fluoresce... more Experiments were conducted to quantify the amount of light injected from a thin film of fluorescent sources confined at the core and cladding interface of an optical fiber, also referred to as a fluorosensor. Conditions necessary for high injection of fluorescent light, previously predicted by a theoretical model, have now been experimentally verified. The results show that, for side excitation, light injection from the thin-film source into guided modes increases with the fiber diameter and the difference between the core and the cladding refractive indices, n core 2 n clad .
Optical Engineering, 1993
Axial strain on an optical fiber can be determined by monitoring the phase shift of a variety of ... more Axial strain on an optical fiber can be determined by monitoring the phase shift of a variety of optical fiber sensors. The exact analytical solutions for optical fields that propagate in a circular core optical fiber are used here to determine the phase shifts that occur for TE and TM modes due to axial strain. Whenever an optical fiber is stressed, the optical path length, the index of refraction, and the propagation constant of each fiber mode change. In consequence, the modal phase term (Beta) z of the fields is shifted by an amount (Delta) (phi) . In certain case, it is desirable to control the phase sensitivity to make fibers that are either more or less sensitive to strain. We show that it can be accomplished by choosing appropriate fiber parameters.
Abstract. The behavior of the power efficiency, Peff, of an optical fiber with a thin-film source... more Abstract. The behavior of the power efficiency, Peff, of an optical fiber
with a thin-film source distributed in the core/cladding interlace is analyzed. The expressions derived make use of the exact field solution of a cylindrical fiber, whereas previous work has made use of the weakly guiding approximation. Although more complicated and harder to interpret, the formulas presented allow the analysis of the power injection efficiency of fibers with arbitrary differences in indices of refraction. The results obtained are relevant to the design of more efficient optical fiber fluorosensors. In this work, some results using the weakly guiding approximation were confirmed. However, in contrast to the weakly guidingwork, we have found that Peft does not always increase with the V number.It was found that Peff always increases with the difference in the indices of refraction, flcore cIad, and varies only slightly with the wavelength, X, and the fiber core radius, a. Finally, by varying a and X in such a way as to make their ratio, a/A, constant, it was found that Peff 5 also constant. This indicates that a/l. is a new independent variable.
Optical Engineering, 1994
Experiments were conducted to verify a theoretical model on the injection efficiency of sources i... more Experiments were conducted to verify a theoretical model on the injection efficiency of sources in the cladding of an optical fiber. The theoretical results predicted an increase in the injection efficiency for higher differences in refractive indices between the core and cladding. The experimental apparatus used consisted of a glass rod 50 cm long, coated at one end with a thin film of fluorescent substance. The fluorescent substance was excited with side illumination, perpendicular to the rod axis, using a 476 nm Argon-ion laser. Part of the excited fluorescence was injected into the core and guided to a detector. The signal was measured for several different cladding refractive indices. The cladding consisted of sugar dissolved in water and the refractive index was changed by varying the sugar concentration in the solution. The results indicate that the power injected into the rod, due to evanescent wave injection, increases with the difference in refractive index which is in qualitative agreement with theory.
Optical fibers may have applications including fluorosensors which sense the concentration of an ... more Optical fibers may have applications including fluorosensors which sense the concentration of an analyte. Like communication fibers, these fluorosensors are modeled using a weakly guiding approximation which is only effective when the difference between the respective refractive indices of the fiber core and surrounding cladding are minimal. An optical fiber fluorosensor is provided having a portion of a fiber core which is surrounded by an active cladding which is permeable by the analyte to be sensed and containing substances which emit light waves upon excitation. A remaining portion of the fiber core is surrounded by a guide cladding which guides these light waves to a sensor which detects the intensity of waves, which is a function of the analyte concentration. Contrary to conventional weakly guiding principles, the difference between the respective indices of refraction of the fiber core is surrounded by an active cladding which is thin enough such that its index of refraction is effectively that of the surrounding atmosphere, thereby the atmosphere guides the injective indices of the fiber core and the cladding results in an unexpected increase in the power efficiency of the fiber core.
Optical Engineering, 1992
The exact field solution of a step-index profile fiber was used to determine the injection effici... more The exact field solution of a step-index profile fiber was used to determine the injection efficiency of a thin-film distribution of polarized sources located in the cladding of an optical fiber. Previous results for random source orientation were confirmed. The behavior of the power efficiency, P(eff), of a polarized distribution of sources was found to be similar to the behavior of a fiber with sources with random orientation. However, for sources polarized in either the x or y direction, P(eff) was found to be more efficient.
Optical Engineering, 1997
A reformulation of the asymptotic solution of the coupled-mode equations with a periodic variatio... more A reformulation of the asymptotic solution of the coupled-mode equations with a periodic variation of the refractive index along the propagation length is presented. A first-order correction using the asymptotic solution and Piccard's method are also determined. It is found that the first-order solution compares very well with the numerical solution throughout a wide range of coupling parameters. The key differences between the method presented here and elsewhere reside in the derivation of the asymptotic solution as well as in the careful derivation of the higher order corrections.
A strain sensor uses an optical fiber including a strain sensitive portion and at least one strai... more A strain sensor uses an optical fiber including a strain sensitive portion and at least one strain insensitive portion. The strain sensitive portion is mounted on the surface of a structure at a location where a strain is desired to be measured. The strain insensitive portion(s) may be fused to the strain sensitive portion to transmit light therethrough, so that the resulting pattern may be detected to determine the amount of strain by comparison with a similar fiber not subjected to strain, or with the light pattern produced when the fiber is not under strain.
Two distributed fiber optic sensors for use in the prevention and monitoring of corrosion in airc... more Two distributed fiber optic sensors for use in the prevention and monitoring of corrosion in aircraft are described. These sensors, based on optical fibers that are intrinsically sensitive to either water or changes in pH, will alert maintenance personnel to the presence of water in lap joints and other inaccessible critical areas. Furthermore, the sensors can also locate precisely where the moisture infiltration has occurred. In a typical application, a sensor fiber would be embedded in a lap joint along the bottom panel of an aircraft's body, or on a wing, where water is likely to collect. Changes in the optical transmission through the fiber can be monitored either periodically or continuously to determine the extent of water penetration.
Experiments were conducted to verify a theoretical model on the injection efficiency of sources i... more Experiments were conducted to verify a theoretical model on the injection efficiency of sources in the cladding of an optical fiber. The theoretical results predicted an increase in the injection efficiency for higher differences in refractive indices between the core and cladding. The experimental apparatus used consisted of a glass rod 50 cm long, coated at one end with a thin film of fluorescent substance. The fluorescent substance was excited with side illumination, perpendicular to the rod axis, using a 476 nm Argon-ion laser. Part of the excited fluorescence was injected into the core and guided to a detector. The signal was measured for several different cladding refractive indices. The cladding consisted of sugar dissolved in water and the refractive index was changed by varying the sugar concentration in the solution. The results indicate that the power injected into the rod, due to evanescent wave injection, increases with the difference in refractive index which is in qualitative agreement with theory.
Optical Engineering, 1995
Modeling an evanescent field absorption optical fiber sensor. [Proceedings of SPIE 2508, 368 (199... more Modeling an evanescent field absorption optical fiber sensor. [Proceedings of SPIE 2508, 368 (1995)]. Claudio O. Egalon, Edgar A. Mendoza, Albert N. Khalil, Robert A. Lieberman. Abstract. Using the weakly guiding and exact ...
Optical Engineering, 1995
Using the weakly guiding and exact field solutions of an optical fiber, we wrote a FORTRAN progra... more Using the weakly guiding and exact field solutions of an optical fiber, we wrote a FORTRAN program to determine the fractional power that reaches the end of an optical fiber with an absorptive cladding. We have assumed that each mode of the fiber is equally excited. This corresponds to incoherent source excitation. The results were compared to a previous approximation published by Payne and Hale in 1993. We have found that, at low V-numbers, V equals 20, Payne and Hale's approximation deviate by more than 20% from the weakly guiding solution. At high V-numbers, the approximation deviates by less than 10%. When compared to Payne and Hale's approximation, both the weakly guiding and exact solutions are close to the data points obtained experimentally by Degrandpre and Burgess in 1988. Although closer than Payne and Hale's approximation, our solution still deviates from the Degrandpre and Burgess results. The difference may result from the assumption that all modes were excited equally. Another possibility was the fact that we have neglected leaky modes in our treatment.
Using the weakly guiding and exact field solutions of an optical fiber, we wrote a FORTRAN progra... more Using the weakly guiding and exact field solutions of an optical fiber, we wrote a FORTRAN program to determine the fractional power that reaches the end of an optical fiber with an absorptive cladding. We have assumed that each mode of the fiber is equally excited. This corresponds to incoherent source excitation. The results were compared to a previous approximations published in the literature. We have found that, at low V-numbers, V < 20, Payne and Hale's approximation deviate by more than 20% from the weakly guiding solution. At high V-numbers, the approximation deviated by less than 10%. When compared to Payne and Hale's approximation, both the weakly guiding and exact solutions are closer to the data points obtained experimentally by Degrandpre and Burgess. Although closer than Payne and Hale's approximation, our solution still deviates from Degrandpre and Burgess' results. The difference may be due to the assumption that all modes were excited equally. Another possibility was the fact that we have neglected leaky modes in our treatment.
A strain sensor is constructed from a two mode optical fiber. When the optical fiber is surface m... more A strain sensor is constructed from a two mode optical fiber. When the optical fiber is surface mounted in a straight line and the object to which the optical fiber is mounted is subjected to strain within a predetermined range, the light intensity of any point at the output of the optical fiber will have a linear relationship to strain, provided the intermodal phase difference is less than 0.17 radians.
Optical Engineering, 1992
The analytical treatment of power efficiency (P(eff) is undertaken for the case of a positively g... more The analytical treatment of power efficiency (P(eff) is undertaken for the case of a positively guiding optical fiber with a thin-film source distributed in the core-cladding interface. The approach adopts the exact solution of the cylindrical optical fiber with an infinite cladding to account for differences between the indices of refraction of the core and the cladding. The excitation of low-loss leaky modes by the cladding is ignored, and only the injection by the evanescent field is considered. The formulas permit the analysis of the power-injection efficiency of fibers with arbitrary differences in indices of refraction. P(eff) does not always increase with V number, but rather varies slightly with wavelength and fiber-core radius and varies significantly with the difference in the indices of refraction. The theoretical results of the work are of interest for designing an atomic-O chemical sensor based on evanescent-wave coupling.
Optical Engineering, 1992
The behavior of the power efficiency of an optical fiber with bulk distribution of sources in its... more The behavior of the power efficiency of an optical fiber with bulk distribution of sources in its cladding is analyzed. Marcuse&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s (1988) results for weakly guiding cylindrical fibers with fluorescent sources uniformly distributed in the cladding are confirmed for the bulk distribution case. It is found that power efficiency increases with wavelength and with difference in refractive indices. A new independent variable for the bulk distribution is found, and it is shown that the power efficiency does not always increase with the V number.
Optical Engineering, 1992
Axial strain can be determined by monitoring the modal pattern variation of an optical fiber. The... more Axial strain can be determined by monitoring the modal pattern variation of an optical fiber. The results of a numerical model developed to calculate the modal pattern variation at the end of a weakly guiding optical fiber under axial strain is presented. Whenever an optical fiber is under stress, the optical path length, the index of refraction, and the propagation constants of each fiber mode change. In consequence, the modal phase term for the fields and the fiber output pattern are also modified. For multimode fibers, very complicated patterns result. The predicted patterns are presented, and an expression for the phase variation with strain is derived.
Optical Engineering, 1994
A numerical model was developed to calculate the modal phase shift of a circular step index profi... more A numerical model was developed to calculate the modal phase shift of a circular step index profile weakly guiding optical fiber under axial strain. Whenever an optical fiber is under stress, the optical path length, the index of refraction, and the propagation constants of each mode change. In consequence, the phase of each mode is also modified. A relationship for the modal phase shift is presented. This relation is applied to both single-mode and two-mode fibers to determine the sensitivity characteristics of strained fibers. It was found that the phase shift is strongly dependent on the core refractive index nco. It was also found that it is possible to design fibers that are insensitive to axial strain. Practical applications of strain- insensitive fibers are discussed.
Optical Engineering, 1992
The exact field solution of a step-index profile fiber is used to determine the excitation effici... more The exact field solution of a step-index profile fiber is used to determine the excitation efficiency of a distribution of sources in the core of an optical fiber. Previous results of a thin-film cladding source distribution to its core source counterpart are used for comparison. The behavior of power efficiency with the fiber parameters is examined and found to be
Journal of The Optical Society of America B-optical Physics, 1995
Experiments were conducted to quantify the amount of light injected from a thin film of fluoresce... more Experiments were conducted to quantify the amount of light injected from a thin film of fluorescent sources confined at the core and cladding interface of an optical fiber, also referred to as a fluorosensor. Conditions necessary for high injection of fluorescent light, previously predicted by a theoretical model, have now been experimentally verified. The results show that, for side excitation, light injection from the thin-film source into guided modes increases with the fiber diameter and the difference between the core and the cladding refractive indices, n core 2 n clad .
Optical Engineering, 1993
Axial strain on an optical fiber can be determined by monitoring the phase shift of a variety of ... more Axial strain on an optical fiber can be determined by monitoring the phase shift of a variety of optical fiber sensors. The exact analytical solutions for optical fields that propagate in a circular core optical fiber are used here to determine the phase shifts that occur for TE and TM modes due to axial strain. Whenever an optical fiber is stressed, the optical path length, the index of refraction, and the propagation constant of each fiber mode change. In consequence, the modal phase term (Beta) z of the fields is shifted by an amount (Delta) (phi) . In certain case, it is desirable to control the phase sensitivity to make fibers that are either more or less sensitive to strain. We show that it can be accomplished by choosing appropriate fiber parameters.