Fused fiber components are critical building blocks for power scaling and reliable operation of fiber laser systems. We
review different fiber fusion methods for fabricating fused fiber components, and show some examples of splicing of dissimilar fibers, fiber combiners, and fiber caps with high power handling capability, which enable power scaling of
We report >100 W output power by coherently combining two, three, and four high power lasers in all-fiber and all-passive configurations using Yb fiber laser cavities operating at a wavelength of 1080 nm with polarization maintaining fibers and 2×2 fused fiber couplers. We present the power and number scaling characteristics of the laser arrays and compare their beam combining efficiencies in different array configurations. We experimentally show beam combining efficiency degradation with increase of laser power and number of lasers. In addition, we discuss the effect of fiber nonlinearity on beam combining efficiency.
We review the technologies of fiber fusion and fused device fabrication for fiber sensing applications. Fiber
interconnection and fused fiber components are integral parts in optical fiber sensing modules and systems. Dissimilar
fibers need to be fused together with low loss and high strength to ensure long-term performance stability. Fused fiber
components, such as fused couplers and polarization-maintaining (PM) components, are important for both coherent
and incoherent detection. In addition, the latest advances in nano/micro-fiber device and multi-port signal combiners
pose new challenges to the fiber fusion and fused component technologies. We describe fundamental optics, discuss
fabrication techniques for these devices, and present some application examples.
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 n<sub>2</sub> 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.
Erbium doped fiber amplifiers have been widely deployed for signal amplification in optical transmission systems. High performance amplifiers require erbium doped fiber with high power conversion efficiency and consistent flat gain spectrum. In addition, all impairments associated with EDF must be under good control. This paper reviews the current status and recent progress on erbium doped fibers, illustrates C and L-band spectral characteristics resulting from different doping compositions, presents some approaches for efficient high power amplifiers, and discusses some EDF nonlinear effects with examples.
A novel erbium doped fiber (EDF) designed for high power WDM applications is presented. The fiber design and performance versus numerical aperture and cutoff wavelength are described based on an advanced EDFA model. The optical and spectral characteristics of the high power fiber are shown. Experimental measurement results of this fiber and comparison with typical commercially available EDFs are given. Performance results show that the new EDF is ideal for high power EDFA applications. It features high power conversion efficiency at high pump power, especially with 980nm pumping, extremely flat gain shape, very low splice loss to typical pigtail fibers, and negligible macro-bending loss.
Characteristics of gain spectral variation of EDFs and its dependence on aluminum doping level and fiber mode design
are quantitatively studied. Based on experimental data and manufactured fibers with different aluminum levels, the
correlation between aluminum concentration and both absorption spectrum and gain flatness is revealed. Gain spectral
variation for over a million meters of EDFs manufactured in last several years is presented. The result shows that peak-to-
peak spectral shape variation for all these fibers are within 0.8% in a 36nm C-band window.
The spatial frequency response, height sensitivity and system noise of a scanning common-path interferometer have been studied. The impulse response function and the frequency transfer function of the system are obtained analytically using Fresnel diffraction integral. Experimental results are also given. The results show that the system covers a broad spatial frequency range from 2 X 10<SUP>-5</SUP>/micrometer to 3/micrometer. The height sensitivity of the system is better than 0.01 angstrom. System stationary noise less than 0.1 angstrom RMS is achievable without additional noise reduction post-process. Measurement of an ultra-smooth silicon substrate with a sub-angstrom roughness is successfully demonstrated. Measurement of a smooth glass substrate is also shown.
By combining the carrier method and electronic speckle shearography, the electronic speckle carrier shearography is realized with a PC-based image processing system. The carrier method is introduced for the unambiguous determination of the deformation fringe order and sign, as well as, for the fringe compensation. The object displacement is automatically generated with A sequence of image processing algorithm. This technique can be applied to both out-plane deformation and the deformation gradient measurement. Its successful application to the rigidity evaluation of the valve of the diesel engine is also presented.
A new whole—field isochromatic fringe compensation technique is presented. In the method, the isochromatic fringe pattern is modulated by the carrier using a carrier generator, and the shifting technique of the moire method and the optical filtering technique are applied. Its applications in diesel engine crankshaft and dynamic thermal analysis are introduced.
SC1020: Splicing of Specialty Fibers and Glass Processing of Fused Components for Fiber Laser and Medical Probe Applications
This course provides attendees with the fundamentals of specialty fiber fusion splicing and fiber glass processing technologies with a focus on high power fiber laser and medical fiber probe applications. It provides an introduction on specialty fibers, reviews the fiber processing approach, and compares different techniques, especially on different fiber fusion processes along with different fusion hardware. It describes fiber waveguide and coupling optics associated with these processes and discusses practical fusion splicing methods for specialty fibers in order to achieve optimal optical coupling between dissimilar fibers. In addition, it illustrates fiber glass processing and fabrication techniques for producing fused fiber components, such as adiabatic taper, mode-field adaptor (MFA), fiber combiners and couplers, and other related fused fiber devices. The course also describes several practical application examples on fiber lasers and monolithic fiber-based probes for OCT medical imaging.