Alranzo Boh Ruffin

Al/Ge co-doped large mode area fiber with high SBS threshold

We propose a novel approach of making large effective area laser fiber with higher threshold for the stimulated Brillouin scattering (SBS) using Al/Ge co-doping in the fiber core. The increased SBS threshold is achieved by reducing the acoustic-optic overlap integral while keeping the optical refractive index profile with a step structure. The manipulation of the overlap integral is done by adjusting the relative doping level between Al(2)O(3) and GeO(2) in the core. The mechanism is validated by detailed examples of numerical modeling. An Yb-doped double clad fiber with the core co-doped with Al(2)O(3) and GeO(2) was fabricated by the OVD process. Measured acoustic velocity profile using a scanning acoustic microscope verified that the acoustic velocity in the fiber core changes with the design. An amplifier utilizing the fiber demonstrated that the proposed fiber yielded 6 dB higher SBS threshold than a fiber without using the co-doping scheme.

Fiber designs for reducing stimulated Brillouin scattering

This paper discusses stimulated Brillouin scattering (SBS) in optical fibers. Theoretical approach for analyzing the SBS in fiber is described. Different fiber design methods for reducing the SBS effect are presented

Optical Fibers With Tailored Acoustic Speed Profiles for Suppressing Stimulated Brillouin Scattering in High-Power, Single-Frequency Sources

In this paper, we discuss the design of optical fibers with tailored acoustic speed profiles to suppress stimulated Brillouin scattering in high-power, single-frequency sources. We demonstrate the ability of these fibers to achieve single-mode output powers of greater than 500 W and discuss the potential to achieve powers beyond 1 kW.

High power, narrow linewidth fiber lasers

Single transverse mode fiber lasers have recently achieved output powers at the kilowatt level. These breakthroughs can be attributed to the maturation of high power diode pump technology at 980 nm and the use of large mode area (LMA) fibers. In the continous wave (cw) operation regime, LMA fibers, through their reduction of device length and increase of the effective area, have been effective in the reduction of deleterious nonlinear optical effects such as stimulated Raman scattering (SRS). The use of LMA fiber has been less effective in the suppression of stimulated Brillouin scattering (SBS), for which the threshold can be several orders of magnitude lower than for SRS. In this work we use refractive index profiles and index modifying dopant distributions for the mitigation of SBS. Our theoretical and modeling efforts led to an experimentally demonstrated increase in SBS threshold of 2.5 dB for single mode fiber and 6 dB for LMA amplifier fiber. We discuss the use of this SBS-suppressive fiber in the demonstration of a high-power, narrow linewidth fiber amplifier.

High performance Yb-doped double-clad optical fibers for high-power, narrow-linewidth fiber laser applications

This paper outlines recent work at Corning Incorporated on fiber composition design and fabrication of a SBS-managed, large-mode-area (LMA), Yb-doped double-clad fiber for high-power, narrow-linewidth fiber laser applications. Through a detailed theoretical analysis for the SBS threshold in optical fibers, an Aluminum/Germanium (Al/Ge) counter-graded fiber-core composition profile has been proposed and demonstrated for reducing the SBS effect, via the reduced-overlap between optical and acoustic modes in the fiber design. Such Al/Ge counter-graded-composition-profile design overcomes the limitation in a multilayer fiber-core approach, in terms of the low-loss fiber fabrication. The new compositionally SBS-managed, LMA Yb-doped double-clad laser fiber fabricated through the new design, has shown more than ~7 dB improvement in SBS threshold over the conventional LMA fiber design. The new fiber offers exceptionally low passive-loss characteristics, and has been demonstrated with uncompromised high laser efficiency for high-power, narrow-linewidth fiber laser applications.

Engineered refractive index profiles for high power fiber lasers

We demonstrate engineered refractive index profiles for the mitigation of nonlinear optical impairments such as stimulated Raman scattering and stimulated Brillouin scattering. These fibers offer performance improvements over conventionally used large mode area fibers.

Balancing filter distortion and crosstalk impairments in optical networks

The design of optical communication networks with network switching elements operating in the optical domain requires careful system analysis and potentially stringent component requirements. We consider here network elements such as transparent optical cross-connects that demultiplex WDM signals, optically switch individual channels, and then multiplex the wavelengths together again before transmission into the next span. Network element optical impairments that can degrade signal quality are in-band (same wavelength) crosstalk, out-of-band crosstalk, and signal distortion from filter concatenation effects. These impairments can limit the transmission distance of a signal before regeneration is required. We examine the trade-offs between crosstalk and filter distortion in the context of the optical filters used in the optical multiplexers and demultiplexers in the network elements. We demonstrate the balance that must be struck between these impairment types in the design of the filters and network system. We study a 10 Gb/s network with 50 GHz channel spacing, examining both NRZ and RZ modulation formats. In both cases, we find optimal filter bandwidths that minimize the total signal degradation measured in terms of Q penalty. The total penalty suffered by RZ signals is higher than that of NRZ signals and must be considered when estimating system reach.