CO2 laser processing facilitates contamination free, rapid, precise and reproducible fabrication of devices for high power fibre laser applications. We present recent progress in fibre end-face preparation and cladding surface modification techniques. We demonstrate a fine feature CO2 laser process that yields topography significantly smaller than that achieved with typical mechanical cleaving processes. We also investigate the side processing of optical fibres for the fabrication of all-glass cladding light strippers and demonstrate extremely efficient cladding mode removal. We apply both techniques to fibres with complex designs containing multiple layers of doped and un-doped silica as well as shaped and circularly symmetric structures. Finally, we discuss the challenges and approaches to working with various fibre and glass-types.
We experimentally studied the coherent beam combining characteristics of fiber laser arrays in all-fiber passive
configurations using polarization maintaining fibers. In addition, we simulated the coherent performance by including
fiber nonlinearity. The beam combining performance is affected by both optical feedback and the laser cavity length
difference. In addition, Kramers-Kronig and n2 induced nonlinearity plays an important role for the coherent phase
locking. We describe the scalability of the coherent array to high power via scaling of laser power and fiber count. We
show coherently combined output powers of 27.4 Watts and 12.2 Watts at 1083 nm in 2-laser and 4-laser arrays.
Fused fiber components are the key building blocks that enable reliable and efficient operation of high power fiber
lasers. In this paper, we review fabrication techniques for the manufacture of such devices, including mode-field
adaptors, fiber tapers, fused couplers, and fused combiners. We present the basic equations governing both the optical
performance and fabrication requirements for these devices, and demonstrate how these apply to some common fiber
laser applications. We then describe and discuss component fabrication techniques and available hardware.
We review fundamental waveguide optics at a fiber joint between dissimilar specialty fibers and its diffusion
characteristics when the joint experiences thermal treatment. We then describe optical coupling techniques including
thermal diffusion and fiber tapering in order to achieve minimum transmission loss through the fiber joint. We discuss
the optical coupling property change due to diffusion and the effect of fiber taper ratio and taper length with application
The performance and integrity of optical fiber based devices and systems are often critically dependent on the optical
coupling between interconnected fibers. In this paper, we discuss the optical characteristics of the interconnected joint
when two dissimilar fibers are fusion-spliced together, and compare different approaches to estimate the optical coupling
loss. We treat the total optical splice loss as a combination of the mode-field (MF) mismatch loss and the transition
taper loss. We describe the spectral characteristics of mode-field mismatch loss and the taper loss between an erbium-doped
fiber (EDF) and SMF28 fiber both experimentally and analytically. In addition, we outline some advanced
techniques for fusion-splicing of large mode area (LMA) fibers and microstructured fibers. Finally, we compare two
types of splicers using arc-discharge fusion and filament fusion technologies, and describe an automated splicing system
with some examples.
Measurement of optical power loss in a fiber splice presents several challenges for manufacturers of optical modules. Requirements include measurement sensitivity of <0.05 ±0.005 dB for ultra low loss fusion splices between similar single mode fibers, and acceptable repeatability and reproducibility (R&R). These issues and several important gaps in the current loss measurement standards are addressed in a new draft standard, recently submitted to the Telecommunications Industry Association (TIA). The new standard describes measurement methods appropriate for various applications, including splices made with similar and dissimilar fiber types, and attenuating fiber at the test wavelength. This paper discusses the loss measurement results and gage R&R comparisons for the different methods included in the new standard, the practical aspects of making measurements and the question of directionality for dissimilar fiber splices. The experimental work was undertaken by the iNEMI (International Electronics Manufacturing Initiative) Fiber Optic Splice Improvement Project. The new loss measurement standard is a collaboration between iNEMI and the TIA.