H.Y. Liu

Strain and temperature sensor using a combination of polymer and silica fibre Bragg gratings

We show that a sensor scheme consisting of a combination of a polymer fibre Bragg grating and a silica fibre Bragg grating gives large discrimination against temperature and strain. It provides large sensitivity and dynamic range for sensing temperature and strain changes simultaneously and independently.

Thermal tuning of polymer optical fiber Bragg gratings

Bragg gratings in polymethyl methacrylate (PMMA)-based polymer fibers were created and were tuned thermally. It is found that the tuning range is more than 18 nm over a temperature variation of 50/spl deg/C. More importantly, no hysteresis effect was observed as the gratings were heated up and cooled down.

Observation of type I and type II gratings behavior in polymer optical fiber

We report the first observation of type I and type II fiber grating behaviors in making polymer optical fiber Bragg gratings. Our observation reveals that there are two distinctive stages in the fabrication of polymer optical fiber Bragg gratings. Notably the two stages of grating formation correspond to low and high-index modulation gratings, which match well with those in silica fiber grating fabrication. Thus we refer them as type I and type II polymer fiber gratings, following the same nomenclatures for different types of silica fiber gratings. In addition, the characteristics and formation mechanism for type I and type II polymer fiber gratings are also examined.

Polymer fiber Bragg gratings with 28-dB transmission rejection

Polymer fiber Bragg gratings (FBGs) with 28-dB transmission rejection and a line width less than 0.5 nm has been achieved for the first time. This result is achieved based on the systematic investigation of growth dynamics of polymer FBGs. We have observed that the growth of polymer FBGs bears some similarities to that of silica FBGs. This work links the mechanism of polymer fiber gratings formation to silica fiber grating and helps to gain better understanding of polymer fiber grating formation process.

Novel growth behaviors of fiber Bragg gratings in polymer optical fiber under UV irradiation with low power

Some novel behaviors in fiber Bragg gratings (FBGs) growth have been observed when the polymer optical fiber are exposed to low-power level of ultraviolet (UV) irradiation. For the first time, we observed the growing and erasing of polymer FBGs under UV exposure, and regrowing after the UV exposure is off. The growth behaviors are quite different in contrast with the previously reported Type I and Type II polymer optical FBGs behaviors. This discloses that polymer FBG growth is a writing-power-dependent process.

Thermal stability of gratings in PMMA and CYTOP polymer fibers

We show in this paper that the Bragg gratings created in perfluorinated CYTOP polymer optical fiber can be tuned thermally over nearly 10 nm when the temperature changes by 60 °C. Furthermore, the thermal stability of these gratings is tested and compared with that of PMMA fiber gratings. Our experimental results demonstrate that the CYTOP polymer fiber grating is more stable than both silica glass fiber grating and the PMMA polymer fiber grating.

Strain sensing characterization of polymer optical fibre Bragg gratings

Static tensile strain is applied to polymer optical fibre Bragg gratings for the strain sensing characterization. Experimental results indicate that the strain coefficient of polymer fibre Bragg gratings is larger than that of silica fibre Bragg gratings. It is also demonstrated the large strain sensing range with good reproducibility, reversibility and repeatability is achieved. As a result, the study shows the great potential of polymer fibre Bragg gratings in the fibre strain sensing applications.

Polymer fiber Bragg gratings tunable dispersion compensation

We propose a new scheme for tunable dispersion with a large tuning range and a fixed center wavelength using linearly chirped polymer fiber Bragg gratings. Simple tension and uniform heating are employed as the control process.

Highly reflective polymer fiber Bragg grating and its growth dynamics

Summary form only given. A polymer fiber Bragg grating with reflectivity higher than 99.8% is fabricated by interferometric side exposure of the fiber core to a UV pulse at 325 nm. The linewidth is less than 0.5 nm. Experimental results also show that the behavior of polymer fiber Bragg grating growth versus UV pulse energy is similar to that of silica fiber Bragg gratings. There is also a threshold of pulse energy, above which the induced index modulation increases dramatically. Below the threshold point, the index modulation grows linearly. So for the region when /spl utri/n increases linearly, it is just comparable to type I gratings in silica fiber. When the POF Bragg grating is over-exposed, the transmission rejection level stays the same, while the loss to the lower wavelength increases and the linewidth becomes larger. This is just comparable to type II gratings of silica fiber. Another outstanding feature is that the Bragg wavelength shifts to the blue part of the spectrum in the course of the grating inscription, which indicates that the induced refractive index modulation by POF Bragg grating is negative.