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ABSTRACT: We report on the significant effect that intermodal dispersion can have on spatially and spectrally resolved interferometric (S<sup>2</sup>) fiber mode analysis. This dispersion can significantly broaden the measured intermodal group delay and could be misinterpreted as distributed scattering. In our new approach, the spectral interference data is analyzed over multiple wavelength windows staggered across the measurement bandwidth and assembled together to form a spectrogram that reveals the wavelength dependence of the intermodal group delay. Measurements on standard telecom single-mode and large-mode-area fibers are presented. This spectrogram analysis is a more accurate map of mode conversion along the fiber and is essential for evaluating fibers and fiber devices.
Optics Letters 09/2012; 37(18):3906-8. · 3.40 Impact Factor
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J.C. Jasapara,
M.J. Andrejco,
A. DeSantolo, A.D. Yablon,
Z. Vrallyay,
J.W. Nicholson,
J.M. Fini,
D.J. DiGiovanni,
C. Headley,
E. Monberg,
F.V. DiMarcello
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ABSTRACT: Diffraction-limited fundamental mode amplification is demonstrated in Er-doped fibers with mode areas ranging from 900 to 1800 mum<sup>2</sup>. The amplifiers are core-pumped with Raman fiber lasers with both signal and pump selectively launched into the fundamental mode. This scheme results in differential gain for the fundamental mode and stabilizes it against mode mixing caused by perturbations in the core. Gains that are greater than 30 dB are demonstrated from a single stage without significant amplified spontaneous emission. The low nonlinearity of the large mode areas enables amplification to high peak powers without resorting to unconventional microstructured or higher order mode fibers.
IEEE Journal of Selected Topics in Quantum Electronics 02/2009; · 3.78 Impact Factor
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ABSTRACT: Spatially and spectrally resolved imaging of mode content in fibers, or more simply, S<sup>2</sup> imaging, is a new measurement technique for analyzing the mode content of large-mode-area (LMA) fibers. It works by spatially resolving the spectral interference that occurs when light in a few-mode fibers scatters into different modes that then propagate with different group delays. A scanning spatial filter in the form of a single-mode fiber probe coupled to an optical spectrum analyzer is utilized to provide both spatial and spectral resolution, and the data are analyzed via the Fourier transform of the optical spectrum. The wealth of data allows for imaging multiple modes simultaneously propagating in the fiber under test as well as quantifying their relative power levels. In addition, the ability to analyze mode images as a function of modal group delay allows distinguishing between discrete scattering at fiber surfaces and distributed scattering that occurs along the length of the LMA fiber. The all-fiber nature of the setup makes the measurement sufficiently stable to measure phase images of the higher order modes (HOMs). Because the method is interferometrically based, even very weak HOMs can be detected.
IEEE Journal of Selected Topics in Quantum Electronics 02/2009; · 3.78 Impact Factor
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ABSTRACT: Robust fundamental mode propagation and amplification of picosecond pulses at 1.56 microm wavelength is demonstrated in a core-pumped Er fiber with 1170 microm2 effective area. Record peak power exceeding 120 kW, and 67 nJ pulse energy are achieved before the onset of pulse breakup. A small increase in input pulse energy results in a temporal collapse of the pulse center to 58 fs duration, with peak powers approaching 200 kW.
Optics Express 12/2008; 16(23):18869-74. · 3.59 Impact Factor
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ABSTRACT: We characterize higher-order-mode content in large-mode-area fibres using spatially and spectrally resolved mode imaging. The technique is capable of distinguishing between discrete and distributed scattering of modes.
Optical Communication, 2008. ECOC 2008. 34th European Conference on; 10/2008
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J.M. Fini,
P.I. Borel,
M.F. Yan,
S. Ramachandran, A.D. Yablon,
P.W. Wisk,
D. Trevor,
D.J. DiGiovanni,
J. Bjerregaard,
P. Kristensen,
K. Carlson,
P.A. Weimann,
C.J. Martin,
A. McCurdy
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ABSTRACT: Ring-assisted fibers suppress unwanted modes, improving the tradeoff that limits bend loss. Fabricated fibers achieve low bend loss and compatibility with standard fibers required for fiber to the home.
Optical Communication, 2008. ECOC 2008. 34th European Conference on; 10/2008
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J W Nicholson, A D Yablon,
M F Yan,
P Wisk,
R Bise,
D J Trevor,
J Alonzo,
T Stockert,
J Fleming,
E Monberg,
F Dimarcello,
J Fini
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ABSTRACT: Femtosecond fiber lasers together with nonlinear fibers are compact, reliable, all-fiber supercontinuum sources. Maintaining an all-fiber configuration, however, necessitates pulse compression in an optical fiber, which can lead to nonlinearities for subhundred femtosecond, nanojoule pulses. In this work we show that using large-mode-area fibers for pulse compression mitigates the nonlinearity, resulting in compressed pulses with significantly reduced satellite pulses. Consequently, supercontinua generated with these pulses are shown to have as much as a 10 dB increase in coherence fringe contrast. By using a hybrid highly nonlinear fiber-photonic crystal fiber, the continuum can be extended to visible wavelengths while still maintaining high coherence.
Optics Letters 10/2008; 33(18):2038-40. · 3.40 Impact Factor
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J.M. Fini,
P.I. Borel,
M.F. Yan,
S. Ramachandran, A.D. Yablon,
P.W. Wisk,
D. Trevor,
D.J. DiGiovanni,
J. Bjerregaard,
P. Kristensen,
K. Carlson,
P.A. Weimann,
C.J. Martin,
A. McCurdy
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ABSTRACT: Solid fibers with greatly reduced bend loss are presented. Ring-assisted fibers provide enhanced cutoff, allowing .01dB / turn cable losses around a 9.5 mm mandrel while meeting cutoff and MFD standards and avoiding potential problems with holes.
Opto-Electronics and Communications Conference, 2008 and the 2008 Australian Conference on Optical Fibre Technology. OECC/ACOFT 2008. Joint conference of the; 08/2008
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ABSTRACT: A new measurement technique, capable of quantifying the number and type of modes propagating in large-mode-area fibers is both proposed and demonstrated. The measurement is based on both spatially and spectrally resolving the image of the output of the fiber under test. The measurement provides high quality images of the modes that can be used to identify the mode order, while at the same time returning the power levels of the higher-order modes relative to the fundamental mode. Alternatively the data can be used to provide statistics on the level of beam pointing instability and mode shape changes due to random uncontrolled fluctuations of the phases between the coherent modes propagating in the fiber. An added advantage of the measurement is that is requires no prior detailed knowledge of the fiber properties in order to identify the modes and quantify their relative power levels. Because of the coherent nature of the measurement, it is far more sensitive to changes in beam properties due to the mode content in the beam than is the more traditional M(2) measurement for characterizing beam quality. We refer to the measurement as Spatially and Spectrally resolved imaging of mode content in fibers, or more simply as S(2) imaging.
Optics Express 06/2008; 16(10):7233-43. · 3.59 Impact Factor
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ABSTRACT: Picosecond pulses at 1.56 micro mm wavelength are directly amplified with a diffraction limited beam quality in a core-pumped Er fiber with an 875 micro m(2) effective area. The interplay between nonlinear spectral broadening and anomalous fiber dispersion compresses the input pulse duration during amplification so that 42 nJ energy pulses with approximately 65 kW peak power are achieved without pulse break-up.
Optics Express 01/2008; 15(26):17494-501. · 3.59 Impact Factor
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ABSTRACT: A four-stage all-fiber single-frequency single-mode continuous-wave (cw) master- oscillator power-amplifier (MOPA) at 1083 nm is presented. Small mode area (SMA) and large mode area (LMA) amplifier stages are mode matched with a fiber mode converter (MC) and the signal and pumps are combined with tapered fiber bundles (TFBs). The final power stage uses a LMA Yb doped SBS-suppressing fiber. A single-frequency output power of 194 W is demonstrated with optical net and slope efficiencies of 68% and 80%, respectively.
Lasers and Electro-Optics Society, 2007. LEOS 2007. The 20th Annual Meeting of the IEEE; 11/2007
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ABSTRACT: We present what we believe to be the first direct measurements of enhanced nonlinearities in large-mode-area fibers due to bend induced reductions in effective area. Both Raman scattering and self-phase modulation are observed to increase in tightly coiled fibers. The measured increase in nonlinearity compares well with predictions from simulations of the modal effective area.
Optics Letters 10/2007; 32(17):2562-4. · 3.40 Impact Factor
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ABSTRACT: Amplification in a single-clad, large-mode-area erbium fiber as an alternative to double-clad Er-Yb amplifiers is presented. Both signal and pump are coupled through a mode-matched splice into the fundamental mode, which ensures preferential gain in the fundamental mode while minimizing the amplified spontaneous emission (ASE). The 875 microm(2) effective area of the Er fiber enables amplification of 6 ps pulses at 1.55 microm wavelength by approximately 33 dB in a single stage to >25 kW peak power with low nonlinear pulse distortion and a diffraction-limited output beam with M(2)<1.1.
Optics Letters 08/2007; 32(16):2429-31. · 3.40 Impact Factor
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ABSTRACT: Fourier domain optical coherence tomography (FDOCT) is applied to measure the cross-section of optical fibres. For standard fibres the measurement of clad diameter with nanometre scale sensitivity, fibre tension, and coating dimensions and concentricity is demonstrated. An understanding of the complicated FDOCT patterns observed for microstructured fibres from which the hole diameter and pitch can be measured non-invasively, was developed. The technique therefore provides a platform for all measurements required when drawing standard and microstructured optical fibres
IEE Proceedings - Optoelectronics 11/2006; · 0.71 Impact Factor
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ABSTRACT: Suppression of stimulated Raman scattering (SRS) is demonstrated in a cladding-pumped fiber amplifier. The Yb-doped amplifier fiber design incorporates a high-index ring that resonantly couples SRS wavelengths out of the gain material, thus filtering the gain. Modeling shows that fiber asymmetry plays an important role in the filtering spectrum.
Optics Letters 10/2006; 31(17):2550-2. · 3.40 Impact Factor
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ABSTRACT: A significant improvement in the efficiency of high power large-mode area fiber amplifiers is demonstrated by improving the overlap of the doped region with the fundamental mode of the fiber
Optical Fiber Communication Conference, 2006 and the 2006 National Fiber Optic Engineers Conference. OFC 2006; 04/2006
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ABSTRACT: An Yb-doped amplifier fiber with distributed gain filtering along its length was fabricated. Measured amplified spontaneous emission confirms gain suppression at wavelengths relevant to important laser noise components. Pump efficiency improvement was observed.
Optical Fiber Communication Conference, 2006 and the 2006 National Fiber Optic Engineers Conference. OFC 2006; 04/2006
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ABSTRACT: Index-matched coupling between core and cladding modes has been designed for an optical fiber by incorporating high-index rings into the cladding. Measurements show resonant coupling at index-matched wavelengths enabling distributed filtering over specific wavelength regions.
Optical Communication, 2005. ECOC 2005. 31st European Conference on; 10/2005
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ABSTRACT: We demonstrate that UV exposure of highly nonlinear, germano-silicate fibers can significantly broaden the infrared supercontinuum generated by femtosecond pulses in these fibers. Both simulations and measurements of the fiber chromatic dispersion show that UV-induced refractive index changes increase the waveguide dispersion by up to 5 ps/(nm-km) at 1570 nm and shift the dispersion zero by over 100 nm. We examine fibers with a range of UV exposure levels and show that the short wavelength edge of the supercontinuum can be continuously changed by more than 100 nm. We also show that the long wavelength edge is extended beyond that of the unexposed fiber. The resulting continuum spans from 0.85 to 2.6 μm. Cutback measurements show that the supercontinuum in the exposed fiber is generated in as little as 1 cm of fiber. A nonlinear Schrödinger equation (NLSE) model of the supercontinuum generation in the nonlinear fiber shows that the short wavelength behavior of the continuum is primarily controlled by changes in the fiber dispersion caused by the UV-induced change in refractive index of the fiber core.
Journal of Lightwave Technology 02/2005; 23(1):13- 18. · 2.78 Impact Factor
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ABSTRACT: Gradient-index fiber lenses are used to fabricate high-strength (>100 kpsi) low-loss fusion splices between two microstructured optical fibers (as low as 0.40 dB) or between a microstructured fiber and a conventional optical fiber (as low as 0.44 dB). This approach overcomes the deleterious effects of heat-induced air-hole collapse, which has until now been an important limitation when fusion splicing microstructured optical fibers.
IEEE Photonics Technology Letters 02/2005; · 2.19 Impact Factor
