Tuning Bragg wavelength by writing gratings on prestrained fibers

Zhang, Qin; Brown, David A.; Reinhart, L.; Morse, Theodore F.; Wang, J.Q.; Xiao, Gang

doi:10.1109/68.311472

Cited by 47 publications

(22 citation statements)

References 7 publications

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“…Going into the saturated regime we show 12 nm tuning with 2.25 % strain using a force of only 0.5 N due to the low Young's modulus of PMMA. This tuning range is about 5 times higher than for silica fibers [15] and can prove useful for future multiplexed sensor applications of POFs.In an earlier experiment, two broadband FBGs were inscribed in a large-core multi-mode mPOF at 1562nm and 1545nm using also a single phase-mask, by thermally annealing the first grating before writing the next [16]. Our method differs from the annealing technique, in that it is much more controllable and works with POFs regardless of their drawing conditions and whether they have been annealed or not.…”

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confidence: 92%

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Tunable Polymer Fiber Bragg Grating (FBG) Inscription: Fabrication of Dual-FBG Temperature Compensated Polymer Optical Fiber Strain Sensors

Yuan

Stefani

Bang

2012

IEEE Photon. Technol. Lett.

108

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We demonstrate stable wavelength tunable inscription of polymer optical fiber Bragg gratings (FBGs). By straining the fiber during FBG inscription, we linearly tune the center wavelength over 7 nm with less than 1% strain. Above 1% strain, the tuning curve saturates and we show a maximum tuning of 12 nm with 2.25% strain. We use this inscription method to fabricate a dual-FBG strain sensor in a poly (methyl methacrylate) single-mode microstructured polymer optical fiber and demonstrate temperature compensated strain sensing around 850 nm.Index Terms-Fiber Bragg grating, polymer optical fiber, strain sensing, temperature compensation. D UE to the low Young's modulus (about 25 times lower than silica) and high elastic limit of over 10% (about 10 times higher than silica), fiber Bragg gratings (FBGs) in polymer optical fibers (POFs) are attractive for fiber-optical strain sensing [1][2]. POFs are also clinically acceptable, flexible and non-brittle, which makes the POF FBG a candidate for in-vivo biomedical applications [3][4][5][6]. FBGs have been reported in both step index POFs [2,7-9] and microstructured POFs (mPOFs) [9][10][11][12][13].To date the majority of POFs and microstructured POFs (mPOFs) are made of poly (methyl methacrylate) (PMMA), which has a high thermo-optic coefficient and strongly absorbs water. PMMA FBG strain sensors therefore have a large cross-sensitivity to humidity and temperature [1,8,13]. The problem of humidity is strongly reduced by using POF FBGs made of the polymer TOPAS [4,5], which has a humidity sensitivity of less than 38.4 pm/%rH @1565nm [13]. This is more than 50 times less than POF FBGs made of PMMA [10,13]. However, both TOPAS and PMMA POF FBGs are still sensitive to temperature with similar sensitivities [1,13]. This is a major problem for POF (and silica) FBG strain sensors in practical applications, in particular in static strain sensing, where temperature variations occur on the same timescale as the variations in strain.A simple solution is to use a second closely spaced and strain free FBG with a different resonance wavelength to Manuscript provide an independent control of the temperature. The difference in resonance frequency between the two FBGs will then still measure the strain, but be independent of temperature, as was demonstrated for silica FBGs [14].In this letter we demonstrate the concept of dual-FBG temperature compensated strain sensing for POF FBGs. To fabricate two (or more) POF FBGs with closely spaced resonance wavelengths we further demonstrate a simple technique for highly controlled tuning of the resonance wavelength of a POF FBG written with the standard phase-mask technique using the same phase-mask. By straining the POF during writing we can linearly tune the wavelength by 7 nm using only 1% strain. Going into the saturated regime we show 12 nm tuning with 2.25 % strain using a force of only 0.5 N due to the low Young's modulus of PMMA. This tuning range is about 5 times higher than for silica fibers [15] and can prove useful for future multiplexe...

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confidence: 92%

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confidence: 92%

Tunable Polymer Fiber Bragg Grating (FBG) Inscription: Fabrication of Dual-FBG Temperature Compensated Polymer Optical Fiber Strain Sensors

Yuan

Stefani

Bang

2012

IEEE Photon. Technol. Lett.

108

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“…Going into the saturated regime we show 12 nm tuning with 2.25% strain using a force of only 0.5 N due to the low Young's modulus [10]. This tuning range is about 5 times higher than for silica fibers [21] and can prove useful for future multiplexed sensor applications of POFs. Let us briefly summarize the results of [10]:…”

Section: Temperature Compensationmentioning

confidence: 83%

Temperature compensated, humidity insensitive, high-T<sub>g</sub> TOPAS FBGs for accelerometers and microphones

et al. 2012

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In this paper we present our latest work on Fiber Bragg Gratings (FBGs) in microstructured polymer optical fibers (mPOFs) and their application as strain sensing transducers in devices, such as accelerometers and microphones. We demonstrate how the cross-sensitivity of the FBG to temperature is eliminated by using dual-FBG technology and how mPOFs fabricated from different grades of TOPAS with glass transition temperatures around 135 o C potentially allow high-temperature humidity insensitive operation. The results bring the mPOF FBG closer to being a viable technology for commercial applications requiring high sensitivity due to the low Young's Modulus of polymer.

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“…It is noteworthy that the standard error between the experiment and the calculation is Ͻ1.0 nm, which can be tuned by prestrain. 2 Figure 4͑b͒ shows the reflected spectrum of fiber Bragg gratings at the Bragg wavelength of 1547.19 nm. …”

Section: Changing the Inscribed Bragg Wavelength With The Wedge-adjusmentioning

confidence: 99%

“…For changing the inscribed Bragg wavelength more than 2 nm, the noncontact technique of phase mask was developed, and allows changes of the inscribed Bragg wavelength. [2][3][4] We present a wedge-adjusted Talbot interferometer for changing the inscribed Bragg wavelength of gratings by shifting the wedge. Figure 1 shows the schematic diagram and illustration of the wedge-adjusted Talbot interferometer, which consisted of two plane-parallel mirrors and a phase mask with its surface aligned perpendicular to the mirrors and adjustor, etc.…”

Section: Introductionmentioning

confidence: 99%

Study of wedge-adjusted Talbot interferometer for writing fiber gratings with variable inscribed Bragg wavelengths

Zhang

2003

Opt. Eng

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A wedge-adjusted Talbot interferometer is presented to change the inscribed Bragg wavelength of fiber Bragg gratings. In this system, the grating is written by UV interference stripes of 193 nm derived from two combined mirrors, where a phase mask is used as a beamsplitter of Ϯ1 order of diffraction light. It is noteworthy that the adjustor transforms the shift of wedge into the rotation of the two mirrors, and alters the mutual angle of two interfering beams in writing fiber Bragg gratings.

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Tuning Bragg wavelength by writing gratings on prestrained fibers

Cited by 47 publications

References 7 publications

Tunable Polymer Fiber Bragg Grating (FBG) Inscription: Fabrication of Dual-FBG Temperature Compensated Polymer Optical Fiber Strain Sensors

Tunable Polymer Fiber Bragg Grating (FBG) Inscription: Fabrication of Dual-FBG Temperature Compensated Polymer Optical Fiber Strain Sensors

Temperature compensated, humidity insensitive, high-T<sub>g</sub> TOPAS FBGs for accelerometers and microphones

Study of wedge-adjusted Talbot interferometer for writing fiber gratings with variable inscribed Bragg wavelengths

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Tuning Bragg wavelength by writing gratings on prestrained fibers

Cited by 47 publications

References 7 publications

Tunable Polymer Fiber Bragg Grating (FBG) Inscription: Fabrication of Dual-FBG Temperature Compensated Polymer Optical Fiber Strain Sensors

Tunable Polymer Fiber Bragg Grating (FBG) Inscription: Fabrication of Dual-FBG Temperature Compensated Polymer Optical Fiber Strain Sensors

Temperature compensated, humidity insensitive, high-T&lt;sub&gt;g&lt;/sub&gt; TOPAS FBGs for accelerometers and microphones

Study of wedge-adjusted Talbot interferometer for writing fiber gratings with variable inscribed Bragg wavelengths

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Temperature compensated, humidity insensitive, high-T<sub>g</sub> TOPAS FBGs for accelerometers and microphones