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In-line fiber optic interferometric sensors in single-mode fibers.

Zhu T, Wu D, Liu M, Duan DW - Sensors (Basel) (2012)

Bottom Line: Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers.It's known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost.Also, some recently reported specific technologies for fabricating such fiber optic interferometers are presented.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Optoelectronic Technology & Systems (Ministry of Education), Chongqing University, Chongqing 400044, China. zhutao@cqu.edu.cn

ABSTRACT
In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It's known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost. In this paper, we review two kinds of typical in-line fiber optic interferometers formed in single-mode fibers fabricated with different post-processing techniques. Also, some recently reported specific technologies for fabricating such fiber optic interferometers are presented.

No MeSH data available.


Related in: MedlinePlus

Configuration of various types of in-line MZIs; the methods of using (a) core-offset structure; (b) air-hole formed by femtosecond laser; (c) peanut-shape structure; (d) open air cavity formed by femtosecond laser; (e) open air cavity formed by large lateral offset splicing.
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f9-sensors-12-10430: Configuration of various types of in-line MZIs; the methods of using (a) core-offset structure; (b) air-hole formed by femtosecond laser; (c) peanut-shape structure; (d) open air cavity formed by femtosecond laser; (e) open air cavity formed by large lateral offset splicing.

Mentions: As previously stated, the in-line MZI requires the splitter and combiner to split the input optical signal into two different optical paths (the solid core and the cladding) and subsequently recombine them together. The other typical techniques for fabricating the splitter/combiner in SMF include misaligned spliced joint [70–72], peanut-shape structure [69] and laser irradiations [81–84]. As shown in Figure 9(a), the in-line MZI could be achieved by splicing two sections of SMF with 7 μm offset. The relative offset direction between the two misaligned spliced joint will affect the interferometer performance greatly. Since it is difficult to fabricate two identical offset structures, practical applications of the MZI based on 7μm core offset are limited by the low extinction ratio [70]. In reference [84], Jiang et al. proposed an in-line MZI based on concatenating two micro-cavities separated by 20 mm, as shown in Figure 9(b). A femtosecond laser was used to fabricate a micro-hole on the center of a fiber end. Then a micro-air-cavity was formed by splicing the micro-hole fiber end with a normal fiber end. Note that the diameter of the micro-cavity is slightly smaller than the fiber core diameter (the diameter and the depth of the hole are ∼7 μm and ∼2.5 μm, respectively), the hole with small depth will excite low-order cladding modes and make the insertion loss lower. Since the low-order cladding modes are insensitive to external RIs, the RI sensitivity of the MZI reported in reference [84] is low, while the temperature sensitivity is very high (∼109 pm/°C) in the range of 500–1,200 °C, as shown in Figure 10.


In-line fiber optic interferometric sensors in single-mode fibers.

Zhu T, Wu D, Liu M, Duan DW - Sensors (Basel) (2012)

Configuration of various types of in-line MZIs; the methods of using (a) core-offset structure; (b) air-hole formed by femtosecond laser; (c) peanut-shape structure; (d) open air cavity formed by femtosecond laser; (e) open air cavity formed by large lateral offset splicing.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472836&req=5

f9-sensors-12-10430: Configuration of various types of in-line MZIs; the methods of using (a) core-offset structure; (b) air-hole formed by femtosecond laser; (c) peanut-shape structure; (d) open air cavity formed by femtosecond laser; (e) open air cavity formed by large lateral offset splicing.
Mentions: As previously stated, the in-line MZI requires the splitter and combiner to split the input optical signal into two different optical paths (the solid core and the cladding) and subsequently recombine them together. The other typical techniques for fabricating the splitter/combiner in SMF include misaligned spliced joint [70–72], peanut-shape structure [69] and laser irradiations [81–84]. As shown in Figure 9(a), the in-line MZI could be achieved by splicing two sections of SMF with 7 μm offset. The relative offset direction between the two misaligned spliced joint will affect the interferometer performance greatly. Since it is difficult to fabricate two identical offset structures, practical applications of the MZI based on 7μm core offset are limited by the low extinction ratio [70]. In reference [84], Jiang et al. proposed an in-line MZI based on concatenating two micro-cavities separated by 20 mm, as shown in Figure 9(b). A femtosecond laser was used to fabricate a micro-hole on the center of a fiber end. Then a micro-air-cavity was formed by splicing the micro-hole fiber end with a normal fiber end. Note that the diameter of the micro-cavity is slightly smaller than the fiber core diameter (the diameter and the depth of the hole are ∼7 μm and ∼2.5 μm, respectively), the hole with small depth will excite low-order cladding modes and make the insertion loss lower. Since the low-order cladding modes are insensitive to external RIs, the RI sensitivity of the MZI reported in reference [84] is low, while the temperature sensitivity is very high (∼109 pm/°C) in the range of 500–1,200 °C, as shown in Figure 10.

Bottom Line: Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers.It's known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost.Also, some recently reported specific technologies for fabricating such fiber optic interferometers are presented.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Optoelectronic Technology & Systems (Ministry of Education), Chongqing University, Chongqing 400044, China. zhutao@cqu.edu.cn

ABSTRACT
In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It's known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost. In this paper, we review two kinds of typical in-line fiber optic interferometers formed in single-mode fibers fabricated with different post-processing techniques. Also, some recently reported specific technologies for fabricating such fiber optic interferometers are presented.

No MeSH data available.


Related in: MedlinePlus