Yen-Sian Lee

Curvature and Temperature Measurement Based on a Few-Mode PCF Formed M-Z-I and an Embedded FBG

We have experimentally demonstrated an optical fiber Mach-Zehnder interferometer (MZI) structure formed by a few-mode photonic crystal fiber (PCF) for curvature measurement and inscribed a fiber Bragg grating (FBG) in the PCF for the purpose of simultaneously measuring temperature. The structure consists of a PCF sandwiched between two multi-mode fibers (MMFs). Bending experimental results show that the proposed sensor has a sensitivity of −1.03 nm/m−1 at a curvature range from 10 m−1 to 22.4 m−1, and the curvature sensitivity of the embedded FBG was −0.003 nm/m−1. Temperature response experimental results showed that the MZI’s wavelength, λa, has a sensitivity of 60.3 pm/°C, and the FBG’s Bragg wavelength, λb, has sensitivity of 9.2 pm/°C in the temperature range of 8 to 100 °C. As such, it can be used for simultaneous measurement of curvature and temperature over ranges of 10 m−1 to 22.4 m−1 and 8 °C to 100 °C, respectively. The results show that the embedded FBG can be a good indicator to compensate the varying ambient temperature during a curvature measurement.

CO 2 Laser Applications in Optical Fiber Components Fabrication and Treatment: A Review

CO2 laser has been widely used in material processing, manufacturing, and medical and military applications since its invention in 1964. Typically for optical fiber components fabrication and treatment, CO2 laser has been reported intensively in stress and birefringence modification, long period grating fabrication, thermal regeneration, optical device fabrication, surface polishing, photosensitivity enhancement, and so on. The reason behind this is due to the advantages of high absorption, fast thermal response, low contamination, dynamic control, and focused heating area owned by the CO2 laser treatment technique. In this paper, a wide variety of CO2 laser applications in optical fiber components fabrication and treatment are reviewed in terms of procedure and principle. The advantages of using CO2 laser and the supremacy of the optical fiber components fabricated or treated by CO2 laser are discussed as well.

LP 01 –LP 11 Cross-Mode Interference in a Chirped Grating Inscribed in Two-Mode Fiber

We have demonstrated LP01-LP11 cross-mode interference in a single chirped grating (CG) inscribed in a two-mode fiber (TMF). With the aid of a binary phase plate, LP01 mode and LP11 mode can be selectively excited in the CG. By offsetting the position of the phase plate from the center of the input beam, we can simultaneously excite both the spatial modes at different LP01:LP11 intensity ratios in the TMF. The excited modes lead to the formation of different interference patterns in the output spectra. The measured output spectra are found to be in good agreement with the simulation based on a coupled mode theory.

Axial stress profiling for few-mode fiber Bragg grating based on resonant wavelength shifts during etching process

We proposed an analytical model to describe the relationship between the axial stress profile of a few-mode fiber Bragg grating with the variations in the resonant wavelengths during a chemical etching process. As a mechanism of preserving state of equilibrium, the etched fiber is experiencing a varying axial strain—contractive or expansive depending on the total axial stress over the remaining cross-sectional area of the fiber. It is found that the induced strain on the etched fiber is the main constituent to the blueshifts and redshifts in the resonant wavelengths during the etching process. The proposed model has been experimentally verified and the estimated axial stress profiles are in good agreement with the measurement by the polariscopic technique.

LP 11 –LP 01 Mode Conversion Based on an Angled-Facet Two-Mode Fiber

We propose and experimentally demonstrate LP11–LP01 mode conversion based on an angled-facet two-mode fiber (AFTMF). It is a simple device based on a standard two-mode fiber with an output facet angle of 43°. At a specific orientation, an incident LP11 beam on the angled-facet can be transformed into a transmitted beam with single-lobe mode profile. The single-lobe beam coupled into a target few-mode fiber (FMF) has successfully excited LP01 mode in the target FMF. The feasibility of the AFTMF to operate as a mode converter is demonstrated. The proposed device is a simple and low-cost mode conversion tool for the space division multiplexing system.