**4. Applications of POF grating devices**

*Application of Optical Fiber in Engineering*

uniform phase mask under strain performance [54]. The spectral reflected power of a 10 mm bandwidth with a chirp of ~0.26 nm/mm under 1.6% strain, and the strain and temperature sensitivity obtained with 0.71 ± 0.02 pm/με and 56.7 pm/°C. Then, Chirped POFBGs have been also obtained by hot water-assisted gradient thermal annealing, where one grating device with around 1.1 nm/mm chirp performance was obtained as **Figure 6** shown [55]. The simplicity of this method is one of the main advantages since no special phase mask or additional etching is needed, and enables easy control of the chirp characteristics and the central wavelength.

Finally, regarding LPG in POF, the extensive literatures with different methods and mechanisms appeared in the last years. Recently, the researcher in Spain [56]

*The spectrum and the bandwidth varies of the chirped POF FBG fabrication with strong gradient annealing.*

**34**

**Figure 6.**

**Figure 5.**

*The end face and the reflected spectrum of three types mPOF.*

POF FBG already goes to industry measurement such as used for water content detection in aviation fuel as shown in the **Figure 7**, the water content in Jet-A1 was measured by using POF FBG sensing technology which calibrated with both coulometric titration and environmental chamber. The results indicate a better performance compare with coulometric titration [58].

POF FBG can be also used to monitor the strain of human arteries with pulse wave signals. A variety of different vital signs including blood pressure can be derived from the signals, which show a higher signal to noise than silica FBG [59], the experimental measurement as **Figure 8** shown.

POF FBG can be used as health equipment for dynamic monitoring of gait. Five FBGs inscribed in CYTOP POF was embedded in a cork insole, as shown in **Figure 9**. The advantages of POF such as higher flexibility and robustness enabled monitoring patients with higher body mass, compared the results obtained with similar systems based on silica fiber, a mean sensitivity of ~8.14 PM/kPa was obtained, which is much higher compared with FBGs in silica optical fiber [60].

Consider the special POF grating applications, due to polymer special characteristics, strain sensing is the most attractive and reliable applications. There is a lot of literature reported POF FBG for strain sensing [61–63]. However, strain sensing under variable humidity and temperature conditions is always an issue for POF sensing technology go to real applications. The researchers in Spain demonstrated

**Figure 7.** *Schematic of the bench test rig [58].*

#### **Figure 8.**

*Experimental measurement of blood pressure uses silica FBG and POF FBG [59].*

#### **Figure 9.**

*Experimental measurement of blood pressure uses silica FBG and POF FBG. (a) Foot plantar area designation ans sensing point. (b) Polymer optical fiber Bragg grating embedded cork insole [60].*

one method use the effective bandwidth of the tunable chirped POFBG, which is highly dependent on the strain and remains practically constant with temperature and humidity changes, can be implemented combine with wavelength measurement, for strain sensors under temperature and humidity variable environments, the spectrum varies under strain condition as **Figure 10** shown [64].

Due to the polymer characteristics, POF grating devices are attracting attention for biomedical applications. An essential feature of these systems is the possibility to detect temperature spatial distributions, which also name as thermal maps. A linearly chirped POF FBG reported as a semi-distributed temperature sensor for monitor the temperature profile along the grating length as **Figure 11** shown [65]. The grating device has been placed close to the radiofrequency applicator, which have one tip inserted in situ of the target. The reflection spectrum of the chirped

**37**

applications.

**Figure 11.**

*Schematic of thermal ablation experiment [65].*

**Figure 10.**

*strain; (c) Bandwidth vs strain [64].*

**Figure 12**.

*Fabrication and Application of Polymer Optical Fiber Grating Devices*

POF FBG was detected by LUNA OBR 4600 and the temperature gradient was estimated use the Gaussian model method. The results indicate that chirped POF FBG can provide significant improvement in thermal detecting for biomedical

*Chirped POF FBG spectrum varies with strain. (a) Spectral reflected power vs strain; (b) Wavelength shift vs* 

Also, a high spatial resolution distributed strain sensing approach based on Chirped POF FBG was reported by researchers in China [66], through spatial wavelength encoded characteristic of Chirped POF FBG, a fully distributed high resolution strain measurement can be achieved by optical frequency domain reflectometry method, which is a promising approach for short-range fully distributed sensing systems, schematic of the experiment setup shown in

*DOI: http://dx.doi.org/10.5772/intechopen.94351*

*Fabrication and Application of Polymer Optical Fiber Grating Devices DOI: http://dx.doi.org/10.5772/intechopen.94351*

#### **Figure 10.**

*Application of Optical Fiber in Engineering*

one method use the effective bandwidth of the tunable chirped POFBG, which is highly dependent on the strain and remains practically constant with temperature and humidity changes, can be implemented combine with wavelength measurement, for strain sensors under temperature and humidity variable environments,

*Experimental measurement of blood pressure uses silica FBG and POF FBG. (a) Foot plantar area designation* 

Due to the polymer characteristics, POF grating devices are attracting attention for biomedical applications. An essential feature of these systems is the possibility to detect temperature spatial distributions, which also name as thermal maps. A linearly chirped POF FBG reported as a semi-distributed temperature sensor for monitor the temperature profile along the grating length as **Figure 11** shown [65]. The grating device has been placed close to the radiofrequency applicator, which have one tip inserted in situ of the target. The reflection spectrum of the chirped

the spectrum varies under strain condition as **Figure 10** shown [64].

*ans sensing point. (b) Polymer optical fiber Bragg grating embedded cork insole [60].*

*Experimental measurement of blood pressure uses silica FBG and POF FBG [59].*

**36**

**Figure 9.**

**Figure 8.**

*Chirped POF FBG spectrum varies with strain. (a) Spectral reflected power vs strain; (b) Wavelength shift vs strain; (c) Bandwidth vs strain [64].*

#### **Figure 11.**

*Schematic of thermal ablation experiment [65].*

POF FBG was detected by LUNA OBR 4600 and the temperature gradient was estimated use the Gaussian model method. The results indicate that chirped POF FBG can provide significant improvement in thermal detecting for biomedical applications.

Also, a high spatial resolution distributed strain sensing approach based on Chirped POF FBG was reported by researchers in China [66], through spatial wavelength encoded characteristic of Chirped POF FBG, a fully distributed high resolution strain measurement can be achieved by optical frequency domain reflectometry method, which is a promising approach for short-range fully distributed sensing systems, schematic of the experiment setup shown in **Figure 12**.

**Figure 12.** *Schematic of the experiment setup for fully distributed strain measurement [66].*
