The fiber grating external cavity laser (FGECL) module packaged with fiber bragg grating and FP laser diode is investigated. The optical spectrum of FGECL is single longitudinal mode. In order to get stable single longitudinal mode, the FP laser diode coated with an AR-coating (reflectivity is 0.5%). To achieve higher coupling efficiency between laser diode and fiber, the hyperbolic-end lensed fiber is used. A coupling efficiency of up to 86% has been demonstrated. The alignment and fix between laser diode and fiber are accomplished by laser welding technology. The results of FGECL module show that the output power and side-mode suppression ratio (SMSR) are more than 2mW and 44dB, respectively. Comparing to the non-AR coated FGECL, the result of SMSR is 5 dB improved. Dynamic tests of the FGECL module operate at 2.5Gbps, including the eye diagram, bit error rates, impedance matching of laser diode, signal current, and the limit of the dispersion in the optical communication system has been measured. The FGECL module can meet the ITU-T G.957 standard.

The fiber-optics communication device with a plastic optical fiber (POF) has become a technology of increasing interests. The attenuation of commercial available POF has been improved to tens of decibels per kilometer. Due to its flexibility and high alignment efficiency, it has been widely used in many areas. In this study, different end shapes of POF have been proposed to increase the coupling efficiency of a POF from a surface emitting LED. Both the experiments and a ray tracing simulation are performed to investigate the coupling scheme. Experimental results also illustrate the feasibility of using ray tracing model in POF end shapes design. The effect of ball fiber lens on coupling efficiency is studied first. Lens material is EPO-TEK 353ND two parts epoxy. The result indicates that the ball fiber lens can improve the coupling efficiency significantly. A more impact end shape modified from the ball fiber lens is proposed in this study, i.e. a thin tip-rounded fiber lens. Numerical and experimental results show the tip can work as good as a ball fiber lens does. A reflection-styled end shape has also been proposed in this thesis, i.e. a taper-ended POF. In this design, the taper edge serves as a reflector to bend the rays incident on it by total internal reflection. The maximum efficiency achieves a great improvement from the previous design. Further study on the various fiber types with different sizes and numerical apertures have also been studied by the ray tracing model.

Cavity ring-down spectroscopy has been used over the last twenty years as a highly sensitive absorption spectroscopic technique to measure light attenuation in gases, liquids, and solid samples. An optical cavity is used as a multi-pass cell, and the decay time of the light intensity in the cavity is measured, thereby rendering the techniques insensitive to light intensity fluctuations. Optical waveguides are used to build the optical cavities presented in this work. The geometries of such waveguides permit the use of very small liquid sample volumes while retaining the advantages of cavity ring-down spectroscopy. In this thesis cavity ring-down measurements are conducted, both, in the time domain and by measuring phase-shifts of sinusoidally modulated light, and the two methods are theoretically connected using a simple mathematical model, which is then experimentally confirmed. A new laser driver, that is compatible with high powered diode lasers, has to be designed to be able to switch from time domain to frequency domain measurements. A sample path length enhancement within the optical cavity is explored with the use of liquid core waveguides. The setup was optimised with respect to the matrix liquid, the geometrical matching of waveguide geometries, and the shape of liquid core waveguide ends. Additionally, a new technique of producing concave lenses at fibre ends has been developed and the output of a general fibre lens is simulated. Finally, liquid core waveguides are incorporated into a fibre-loop ring-down spectroscopy setup to measure the attenuation of two model dyes in a sample volume of <1 µL. The setup is characterized by measuring concentrations of Allura Red AC and Congo Red from 1 µM to a limit of detection of 5 nM. The performance of the setup is compared to other absorption techniques measuring liquid samples. / Thesis (Ph.D, Chemistry) -- Queen's University, 2013-04-23 14:08:16.33