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A novel method of integrating a total internal reflection (TIR) mirror into an optical waveguide embedded in a printed circuit board (PCB) was demonstrated for application in chip-to-chip optical interconnects. Plastic optical fiber (POF) was placed into channels that were mechanically machined into FR-4 composite plates. The TIR mirror was created by a second mechanical machining. The mirror loss was measured to be approximately −1.6 dBper reflection. The use of POF resulted in attenuation losses in the waveguide over an order of magnitude lower than what is obtainable with typical planar waveguides that are integrated into PCBs. Monte Carlo ray tracing was used to determine the theoretical efficiency of the system as well as cross talk between channels due to optical device alignment tolerances. [ABSTRACT FROM AUTHOR]

In recent decades, optical fiber has proven useful for many sensor applications. Specifically, fiber Bragg grating (FBG) sensors have shown great utility for integrity management and environmental sensing of composite structures. One major drawback of FBG sensors, however, is the lack of a robust, nonpigtail technique for coupling to the embedded FBG sensor. In this paper, a novel method of free-space passive coupling of light into FBG sensors is described. An angled 45-degmirror integrated directly into the fiber was used as an input coupling technique. We investigated the application of this approach to both single- and multimode glass fibers containing FBGs. For multimode FBGs, we studied the grating’s uniformity across the fiber diameter and its effect on normal free-space coupling. In single-mode investigations, a novel method of coupling to the sensor via splicing a multimode fiber to a single-mode FBG (SMFBG) was developed. Finally, free-space coupling to an embedded SMFBG was employed to measure the tensile strain. Excellent agreement was found between the FBG and conventional electrical resistance strain gauges. We conclude that this coupling method might eliminate the need for pigtailing by providing a more robust coupling method for FBG sensors. [ABSTRACT FROM AUTHOR]

A novel method for passive coupling of light to optical communication links embedded in composite structures has been explored. The use of 45-deg-angled mirrors integrated directly in poly-(methylmethacrylate) fibers as an input node coupling technique was characterized under conditions of varying refractive index. Mirrors were integrated into the fiber through polishing of the endface to a 45-deg angle and then thermal evaporation of Ag metal. To explore angular tolerances and sensitivity to alignment errors, the efficiency of the node was characterized as a function of source position and angle of incidence. Coupling loss as low as −0.39 dB was measured for normal incidence while the input node was immersed in a fluid with refractive index of 1.33. Ray tracing simulations were used to model the coupling of light to fabricated input nodes and showed good agreement with experiments. [ABSTRACT FROM AUTHOR]