Polarization-maintained propagation of a 2200 μm effective-area higher-order-mode in a bent optical fiber.

We report on the excitation and polarization preserved propagation of a very large effective-area (A ∼ 2240 μm) higher-order-mode in an optical fiber. A laser signal operating in the 1 μm wavelength region is transported in a Bessel-like LP mode over a 10 m long section of the polarization-maintaining higher-order-mode fiber. We observe that the light propagates through the fiber with >10 dB polarization-extinction-ratio as the fiber is coiled into circular loops of 40 cm diameter.

Reconversion of higher-order-mode (HOM) output from cladding-pumped hybrid Yb:HOM fiber amplifier.

We demonstrate operation of a cladding-pumped hybrid ytterbium-doped HOM fiber amplifier and reconversion of the HOM output to Gaussian-like beam by using an axicon based reconversion system. The amplifier was constructed by concatenating single-mode and HOM ytterbium-doped double clad fibers, and was excited by a common multimode pump source. A continuous wave (cw) input signal of 97mW was amplified to 100W at the amplifier output, which yielded a gain of more than 30dB.

Polarization-maintaining, large-effective-area, higher-order-mode fiber.

Higher-order-mode (HOM) fibers guiding light in large-effective-area (A) Bessel-like modes have recently generated great interest for high-power laser applications. A polarization-maintaining (PM) version of HOM fibers can afford the added possibility of coherent beam combination, improved material processing, and polarization multiplexing of high-power fiber lasers. We report a PM-HOM fiber for guiding Bessel-like modes with A ranging from 1200-2800  μm.

Seven-core erbium-doped double-clad fiber amplifier pumped simultaneously by side-coupled multimode fiber.

We demonstrate a seven-core erbium-doped fiber amplifier in which all the cores were pumped simultaneously by a side-coupled tapered multimode fiber. The amplifier has multicore (MC) MC inputs and MC outputs, which can be readily spliced to MC transmission fiber for amplifying space division multiplexed signals. Gain over 25 dB was obtained in each of the cores over a 40-nm bandwidth covering the C-band.

Single-frequency Brillouin distributed feedback fiber laser.

We demonstrate a single-frequency Brillouin distributed feedback laser (DFB). The DFB laser cavity was a 12.4 cm long fiber Bragg grating with a π-phase shift offset from the grating center.

Crosstalk in multicore fibers with randomness: gradual drift vs. short-length variations.

Random perturbations play an important role in the crosstalk of multicore fibers, and can be captured by statistical coupled-mode calculations. In this approach, phase matching contributes a multiplicative factor to the average crosstalk, depending on the perturbation statistics and any intentional heterogeneity of neighboring cores. The impact of perturbations is shown to be qualitatively different depending on whether they are gradually varying, or have short-length (centimeter-scale) variations.

Raman fiber distributed feedback lasers.

We demonstrate fiber distributed feedback (DFB) lasers using Raman gain in two germanosilicate fibers. Our DFB cavities were 124 mm uniform fiber Bragg gratings with a π phase shift offset from the grating center. Our pump was at 1480 nm and the DFB lasers operated on a single longitudinal mode near 1584 nm.

Real time monitoring of a fiber fuse using an optical time-domain reflectometer.

We propose and experimentally demonstrate monitoring of a fiber fuse in real time using an optical time domain reflectometer (OTDR). When a fuse starts, a weak reflection of light occurs from the leading edge of the fuse where plasma and voids are being formed in the core. In this work, we examined the possibility of monitoring a fiber fuse from a remote location using an OTDR.

Measurements of spectral broadening and Doppler shift of backreflections from a fiber fuse using heterodyne detection.

We report broadening in spectrum as light is backreflected from a propagating fiber fuse. The formation of micrometer-size voids results in periodic changes in Fresnel reflection occurring in the leading part of the fuse. High-resolution measurement of the optical spectrum via heterodyne detection revealed an upshift (Doppler shift) in the optical frequency and discrete frequency components that are characteristic of amplitude modulation due to periodic void formation.

Backreflected radiation due to a propagating fiber fuse.

The properties of backreflected light due to voids in a fiber fuse were studied using optical coherence-domain reflectometry of a damaged fiber and real-time monitoring of the electrical (RF) and optical frequency spectrum. Light reflected backward at the interface of a propagating fiber fuse acquired low-frequency broadband amplitude modulation, which can be detected remotely at the source end, using an RF spectrum analyzer. For the light backreflected during propagation of a fuse, we derived an analytical expression that well explained the spectral features observed experimentally in the RF spectrum.

DPSK multicast using multiple-pump FWM in Bismuths highly nonlinear fiber with high multicast efficiency.

In this paper, we discuss the multicast efficiency issue in the optical layer multicast. A 1-to-8 phase-preserved different phase-shifted keying (DPSK) wavelength multicast is experimentally demonstrated using four-wave mixing (FWM) in a piece of Bismuth highly nonlinear fiber (Bi- HNLF). DPSK signal is successfully delivered from one wavelength to up to eight different wavelengths using only three pumps.

High-speed all-optical modulation using an InGaAs/AlAsSb quantum well waveguide.

All-optical cross-phase modulation through the intersubband transition in an InGaAs/AlAsSb coupled quantum well was examined by using a sinusoidal intensity-modulated pump. For probe waves in the wavelength range of 1330-1620 nm and a pump modulation at a repetition rate of 76 GHz, cross-phase modulation (XPM) occurred with an efficiency eta, of 0.653-0.

Gain-assisted superluminal propagation in tellurite glass fiber based on stimulated Brillouin scattering.

We demonstrate superluminal propagation of optical pulses with amplification in optical fibers based on stimulated Brillouin scattering. A triple gain peak configuration is used for the generation of narrowband anomalous dispersion in 2 m tellurite glass fiber, where the group index change as much as -1.19 is achieved with 6.

Stimulated Brillouin scattering in single-mode tellurite glass fiber.

Stimulated Brillouin scattering properties in a single-mode tellurite glass fiber were studied using a cw laser with an operating wavelength of 1.54 mum. The Brillouin frequency shift v(B) and the gain linewidth Deltav(B) were 7.

Highly efficient Brillouin slow and fast light using As(2)Se(3) chalcogenide fiber.

We demonstrate the generation of slow and fast light based on stimulated Brillouin scattering in As(2)Se(3) chalcogenide fiber with the best efficiency ever reported. The Brillouin gain of 43 dB is achieved with only 60-mW pump power in a 5-m single-mode chalcogenide fiber, which leads to the optical time delay of 37 ns with a 50-ns Gaussian pulse.

Brillouin amplification and lasing in a single-mode As2Se3 chalcogenide fiber.

Brillouin amplification and lasing are demonstrated in a single-mode As2Se3 chalcogenide fiber. A Brillouin gain of 42 dB was measured in a 4.9 m long fiber for a pump power of 68 mW at a 1.

Single-frequency Brillouin lasing using single-mode As(2)Se(3) chalcogenide fiber.

Brillouin lasing in a single-longitudinal mode at 1.55 mum is demonstrated using As2Se3 single-mode fiber for the first time. The As(2)Se(3) fiber provides sufficient Brillouin gain for the Stokes wave to initiate single frequency oscillation in a 2-m long fiber Fabry-Perot cavity with a nonresonant pump power of 56 mW.

Observation of strong stimulated Brillouin scattering in single-mode As2Se3 chalcogenide fiber.

Strong stimulated Brillouin scattering in single-mode As2Se3 chalcogenide fiber is observed using a cw laser at 1.55 microm wavelength region. Brillouin threshold for a 5-m-long fiber is as small as 85 mW.

Ultrafast pulse retiming by cross-phase modulation in an anomalous-dispersion polarization-maintaining fiber.

Retiming of signal pulses by orthogonally polarized control pulses copropagating in an anomalous-dispersion low-birefringence polarization-maintaining fiber is demonstrated. Through walk-off-free cross-phase modulation in a 500 m long fiber, optical pulses at a 10 GHz rate are retimed by as much as +/- 2 ps.

Widely tunable femtosecond soliton pulse generation at a 10-GHz repetition rate by use of the soliton self-frequency shift in photonic crystal fiber.

We demonstrate a soliton self-frequency shift of approximately 120 nm in a fiber with 1.56-microm pulses generated at a 10-GHz repetition rate by an actively mode-locked laser. A highly nonlinear photonic crystal fiber with a length of only 12.