열광학 가변 융착 광섬유 커플러
Thermo-optically tunable fused fiber coupler
조규정, 문남일, 강지훈, 김인수, 김광택*
*
호남대학교 광전자공학과 [email protected]
Fused fiber couplers are key devices in optical communication and optical sensor systems, and can perform many important functions, such as optical power dividing and evanescent wave sensing1],[2].
In this study, a thermo-optically fused fiber coupler with a wide tuning range was developed. In order to tune the characteristics of the fused coupler, the taped region of the fused coupler was coated with a polymer with a good thermo-optic effect. The key hypothesis was that the transmission characteristics of the coupler can interact strongly with the polymer external medium through an evanescent wave interaction. The proposed tunable coupler was equipped with a micro coil heater and tuned by the electric current applied in the heater as shown in Fig. 1
The maximum transmission wavelengths of the throughput and crossed-coupled ports were adjusted to 1550 nm and 1310 nm, respectively. The measured diameter of the waist of the coupler was approximately 30 mm. The coupler was packaged into a quartz rod with a U shape cross section view.
Finally, a thermo-optic tunable coupler incorporating a coil heater made from Ni-Cr wire was fabricated. A polymer(ZPU-145, Comoptics), whose room temperature refractive index at 1550nm and thermo-optic coefficient were1.45 and -1.8
×
10-4/oC, respectively, was selected in the experiment. The diameter of the Ni-Cr wire and inner diameter of the coil were 110 mm and 2.0 mm, respectively. The electric resistance was set to 50 . An electric current was applied to the coil heater. Fig. 2 shows the spectral response in accordance with the applied electric power. As expected, the minimum transmission wavelength shifted to a shorter wavelength region with increasing supplied electric power due to thermo-optic effect in the polymer. When 605 mW was supplied to the heater, the coupling wavelength was close to the 1550nm for cross coupled port. Reference[1]T. Bricheno, V. Baker “ All-fiber polarization splitter/combiner” Electronic letters, Vol. 21, No. 6, pp. 251-252, 1985.
[2] T. Tazawa, T. Kanie, M. Katayama, “Fiber-optic coupler based refractive index sensor and its application to biosensing” Appl. Phys. Lett. vol.91, 113901-113903, 2007.
ACKNOWLEDGEMENT
This research was also partially supported by the program for the Training of Graduate Students in Regional Innovation and the program for Regional Strategic Industries which was conducted by the Ministry of Commerce Industry and Energy, Korea.
Fig. 1. structure of tunable fused fiber coupler
Fig. 2 tuning of transmission spectrum in accordance with applied electric power
