Free Lasers and the Effects of Fiber Optic CouplingAdam Manganiello, Colin Gregory, Scott Johnson

Mentor: Dr. Deveney

Department of Physics, Bridgewater State University // Bridgewater MA, 02324

Abstract: In the study of Fiber Optics, one has many options to choose from in terms of what Fiber Optics application they are too study. Our group is employed across varying fields and through collaboration we decided to investigate the properties of a free laser as it emerges from a fiber optic launch cable. The act of launching the free laser into a fiber optic coupler proved to be an incredibly daunting task. The goal of coupling the laser took us three weeks to achieve; in this time we took turns adjusting the alignment screws in a raster like fashion until coupling was achieved. We maximized the power output and collimated the beam. At this point we are attempting to obtain a Gaussian beam profile and are investigating the potential to use out laser system for communications.

Fiber Optics: Fiber optics are put to use everywhere from color change Christmas trees to high speed communication. The essential properties of how a beam propagates through a now fiber optic cable where first observed with light shining into a barrel of water and propagating through a stream of water emerging from the base of the container. It wasn’t until the 1970’s when Corning Glass Works patented high-silica glass fibers that we would see efficient communications past one kilometer. Today most industrial networks employ a fiber optic communications backbone due to its reliability and high speed capabilities.

Findings: In our trials we have found that ~60 percent of the power of a 5mw laser is lost due to fiber optic coupling. Although the loss percentage is quite high, one is still left with a usable, collimated laser output. In figure one, although not entirely precise, one may view a traditional Gaussian Beam profile. At the center point of the beam (1 Degree on the rotational stage) one may observe a power output of .87mW.

Future Trials: In the coming months we look forward to obtaining a proper Gaussian Beam profile with a much higher degree of precision. If time permits we would also like to program an interface and microcontroller in order to modulate the power of our laser so that we may be able to send and receive a viable communications signal. Due to the difficulty of coupling the free laser into the fiber optic launch cable, we are behind schedule in terms of achieving our communications goal.

Acknowledgements:

Dr. Deveney and the Adrian Tinsley Program

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Gaussian Profile Data

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Figure 1: Figure one is a graphical interpretation of the data that we obtained by rotating our collimated, optically coupled, laser output through two degrees of rotation on a rotational stage.