A large number of power delivery applications for optical fibers require beams with very specific output intensity profiles; in particular applications that require a focused high intensity beam typically image the near field (NF) intensity distribution at the exit surface of an optical fiber. In this work we discuss optical fiber designs that shape the output beam profile to more closely correspond to what is required in many real world industrial applications. Specifically we present results demonstrating the ability to transform Gaussian beams to shapes required for industrial applications and how that relates to system parameters such as beam product parameter (BPP) values. We report on the how different waveguide structures perform in the NF and show results on how to achieve flat-top with circular outputs.
We present results on the amplifier performance and characteristics of Yb-doped Single Mode fiber amplifiers spanning a broad range of wavelengths from 1028 nm to 1100 nm. Both PM and non-PM amplifiers are discussed, with emphasis on the use of polarization controllers in intrinsically non-PM amplifiers to obtain high Polarization Extinction Ratios (PER). In general, outside the 1064nm region, there has been relatively little discussion or work towards developing high power fiber amplifiers for operation at either 1030 nm or 1100 nm with narrow line-width and high brightness, primarily due to amplifier design and architecture issues related to strong re-absorption and amplified spontaneous emission. Here we address key fiber and amplifier design characteristics aimed at mitigating these issues while highlighting performance attributes and challenges for operation near either end of the above defined spectral range.
We demonstrate a highly manufacturable, low-cost, compatible Single-Polarization Fiber (PZF), which offers
the widest polarization bandwidth ever reported in commercial fibers, combined with superior polarization
extinction ratio and performance consistency. The principle of the design is discussed in this paper and the full
spectral attenuation results shown. We demonstrate the exceptional performance of the fiber for different fiber
lengths and layouts. Experimental results show that the Single-Polarization fiber of this study exhibits a
Polarization Extinction Ratio (PER) greater than 40dB, and a polarizing bandwidth wider than 200nm,
measured on fiber lengths as short as four meters. In addition, PZF is designed with a circular mode field, which
makes it low-loss and highly compatible with standard single mode fiber systems and devices.
We report on a new class of novel optical fiber structures, designed for use in harsh environments typical of Oil and Gas Applications. Specifically, we focus on fiber designs that alleviate the effects of hydrogen ingression and its associated darkening of optical fibers in harsh environments. We demonstrate theoretically, how a carbon coated optical fiber structure consisting of an array of randomly or systematically placed voids running along the length of the fiber, can lead to significantly reduced hydrogen ingression effects. The array of voids can be of arbitrarily varying shapes and sizes, along the length of the fiber. We derive an equation describing the increase in the fiber lifetime as a function of the average cross-sectional fraction of voids in the fiber. Fiber darkening effects are predicted to decrease by factors of as much as x10, for moderately low fraction of voids in the fiber cross-section. Theoretical predictions are confirmed experimentally by performing ingression tests in a hydrogen test chamber with on-line monitoring capability, simulating down-hole temperatures and pressures. Additional geometric factors, such as fiber diameter, that may also be optimized to further improve the hydrogen ingression resistance of fibers are discussed; in this vein a new larger form-factor fiber, different from the standard 125um fiber is proposed. Finally, the lifetime predictions greater than 5-10 years obtained for such void-filled optical fibers in typical down-hole conditions make them extremely attractive candidates for use in Oil and Gas applications such as well monitoring and logging.
Optical fibers with improved hermeticity, strength and chemical resistance are presented. Specifically, we provide data demonstrating the resistance of carbon coated optical fibers to hydrogen (high partial pressures and temperatures) and acidic environments. As well we provide data and analysis indicating that carbon coated fibers with increased n-values provide long lifetimes under stressed conditions.