The antiresonance spectral characteristics based on a silica capillary sandwiched between two single-mode fibers are investigated on the aspects of both transmission and reflection. Basic theory of the antiresonance reflecting optical waveguide model is presented and analyzed for this structure. During the fabrication, suitable parameters are adopted in in the manual welding process to keep the cross section of the capillary fiber away from the discharge electrode, which ensures the smoothness between the welding surfaces. Subsequently, three experimental samples are fabricated with the same inner diameter and various lengths of 650 μm, 837 μm, and 1070 μm, respectively. It can be observed that devices with different lengths have the same resonance wavelength in the wavelength range of 1500-1700 nm. However, the transmission depth at the resonance wavelength increases with the increase of the capillary length. We also discuss the relationship between inner diameter and transmission spectra through three samples with inner diameters of 25 μm, 50 μm, and 75 μm. The experimental results show that the free spectral range is 22.9 nm, 29.8 nm, and 44.1 nm, respectively. It also exists antiresonance in the reflection, which shows a novel mechanism for possible sensing applications.
It is demonstrated that the constitution of complex Faraday rotation in presence of intrinsic birefringence. We analyze the relationships between incident azimuth of linearly polarized light and birefringence and the influence of different orders birefringence on the measurement of magneto-optical effect. We proposed a relatively simple technique to accurately measure Faraday rotation of fiber. The order of birefringence in optical fiber and the high sensitivity magnetooptical characteristics can be determined by the measurement system.
This paper focuses on a method to decrease the scattering loss induced by surface roughness through waveguide structure optimization. First, the concept of roughness is discussed briefly, and the diagram of waveguide surface roughness tested by optical profiler is given. Then, this report mainly analyzes the influence on scattering loss coefficient and total loss coefficient induced by surface roughness under different waveguide parameters. The study finds that the scattering loss coefficient and the total loss coefficient increase as roughness increasing. Last, the part produces a method to decrease scattering loss induced by roughness through waveguide structure optimization importantly. It is found that the total scattering loss coefficient can be decreased greatly if waveguide core size is in range from 60 μm to 80 μm or the parameter Δ is smaller than 0.016. When surface roughness is 200 nm, the correlation length is 4 μm, waveguide length is 100 cm, and core width (height, <i>a=b</i>) is from 30 μm to 70 μm, the total scattering loss coefficient can decrease from 3.37×10<sup>-2</sup> dB/cm to 1.65×10<sup>-2</sup> dB/cm.