Seiki Ohara

Experimental comparison of a Kerr nonlinearity figure of merit including the stimulated Brillouin scattering threshold for state-of-the-art nonlinear optical fibers

We introduce a new figure of merit (FOM) including the input pump power limit associated with stimulated Brillouin scattering (SBS) for evaluation of the Kerr nonlinearity efficiency of optical fibers. The new FOM is expressed as gammaL(eff)P(SBS) (gamma is a nonlinearity parameter, L(eff) is effective length, and P(SBS) is the SBS threshold), while the conventional FOM is given by gammaL(eff). Using the new FOM, we perform an efficiency comparison among four types of state-of-the-art nonlinear optical fiber: a Bi2O3-based nonlinear fiber, a silica-based holey fiber, a highly nonlinear dispersion-shifted fiber, and a conventional dispersion-shifted fiber. The Bi2O3-based nonlinear fiber is found to have the best Kerr nonlinearity efficiency owing to the superior nonlinear property of the Bi2O3 glass compared with that of the silica.

1.5 GHz picosecond pulse generation from a monolithic waveguide laser with a graphene-film saturable output coupler

We fabricate a saturable absorber mirror by coating a graphene- film on an output coupler mirror. This is then used to obtain Q-switched mode-locking from a diode-pumped linear cavity channel waveguide laser inscribed in Ytterbium-doped Bismuthate Glass. The laser produces 1.06 ps pulses at ~1039 nm, with a 1.5 GHz repetition rate, 48% slope efficiency and 202 mW average output power. This performance is due to the combination of the graphene saturable absorber and the high quality optical waveguides in the laser glass.

Use of 1-m Bi2O3 nonlinear fiber for 160-Gbit/s optical time-division demultiplexing based on polarization rotation and a wavelength shift induced by cross-phase modulation.

We present, for the first time to our knowledge, experimental results of the use of a 1-m-long Bi2O3-based nonlinear fiber (Bi-NLF) with a nonlinear parameter gamma of approximately 1100 W(-1) km(-l) within an all-fiber-based 160Gbit/s optical time-division multiplexing (OTDM) data demultiplexer. Our demultiplexing switch basically uses the principle of the Kerr shutter, and its switching performance is further enhanced by the additional use of the wavelength blueshift of data pulses, which is induced by cross-phase modulation from the control pulses trailing edge. The OTDM demultiplexer, composed of the 1-m Bi-NLF, readily achieves error-free demultiplexing operation of all 16 channels.

Bismuth-oxide-based nonlinear fiber with a high SBS threshold and its application to four-wave-mixing wavelength conversion using a pure continuous-wave pump

The unique and practical benefits of the use of bismuth-oxide-based nonlinear fiber (Bi-NLF) in implementing a four-wave-mixing (FWM)-based wavelength converter for fiber-optic-communication-system applications are experimentally demonstrated. First, the Kerr-nonlinearity and stimulated-Brillouin-scattering (SBS) characteristics of our fabricated Bi-NLF are experimentally investigated. The Bi-NLF is found to have the superior advantage of a significantly high SBS threshold in addition to its ultrahigh Kerr nonlinearity /spl gamma/ of /spl sim/1100 W/sup -1//spl middot/km/sup -1/, compared to the conventional silica-based highly nonlinear fiber. Next, the authors perform an experiment for the FWM-based wavelength conversion of a non-return-to-zero (NRZ) signal within a 40-cm length of the Bi-NLF fusion spliced to standard silica fibers by using a continuous-wave (CW) high-power pump beam. Error-free tunable wavelength conversion over a 10-nm bandwidth is readily achieved. No SBS-suppression scheme is employed for the pump due to the high SBS threshold, which simplifies the system configuration and improves the quality of the wavelength-converted signal.

Compact, highly efficient ytterbium doped bismuthate glass waveguide laser

Laser slope efficiencies close to the quantum defect limit and in excess of 78% have been obtained from an ultrafast laser inscribed buried channel waveguide fabricated in a ytterbium-doped bismuthate glass. The simultaneous achievement of low propagation losses and preservation of the fluorescence properties of ytterbium ions is the basis of the outstanding laser performance.

Four-wave-mixing-based wavelength conversion of 40-Gb/s nonreturn-to-zero signal using 40-cm bismuth oxide nonlinear optical fiber

We experimentally demonstrate a compact and tunable four-wave-mixing-based wavelength converter using a Bi/sub 2/O/sub 3/-based nonlinear fiber (Bi-NLF). An only 40-cm-long Bi-NLF is used as a nonlinear optical medium for wavelength conversion of a 40-Gb/s nonreturn-to-zero (NRZ) signal with no additional stimulated Brillouin scattering (SBS) suppression scheme. The Bi-NLF used in this experiment has an extremely high SBS threshold owing to both its short length and relatively low Brillouin gain. The 40-cm Bi-NLF is fusion-spliced to standard single-mode fibers and its nonlinearity is measured to be /spl sim/1100 W/sup -1//spl middot/km/sup -1/. Error-free wavelength conversion over a 10-nm bandwidth at a 40-Gb/s NRZ data rate is readily achieved with a pure continuous-wave pump.

Four-wave mixing based widely tunable wavelength conversion using 1-m dispersion-shifted bismuth-oxide photonic crystal fiber

We demonstrate widely tunable wavelength conversion based on four-wave mixing using a dispersion-shifted bismuth-oxide photonic crystal fiber (Bi-PCF). A 1-meter-long Bi-PCF is used as the nonlinear medium for wavelength conversion of a 10 Gb/s non-return-to-zero (NRZ) signal. A 3- dB working range of the converted signal over 35 nm is obtained with around 1-dB power penalty in the bit-error-rate measurements.

All-fiber 80-Gbit/s wavelength converter using 1-m-long Bismuth Oxide-based nonlinear optical fiber with a nonlinearity γ of 1100 W -1 km -1

We experimentally demonstrate the use of our fabricated 1-m-long Bi2O3 optical fiber (Bi-NLF) with an ultra-high nonlinearity of ~1100 W-1km-1 for wavelength conversion of OTDM signals. With successfully performed fusion splicing of the Bi-NLF to conventional silica fibers an all-fiber wavelength converter is readily implemented by use of a conventional Kerr shutter configuration. Owing to the extremely short fiber length, no additional scheme was employed for suppression of signal polarization fluctuation induced by local birefringence fluctuation, which is usually observed in a long-fiber Kerr shutter. The wavelength converter, composed of the 1-m Bi-NLF readily achieves error-free wavelength conversion of an 80-Gbit/s input signal.

All fiber-based 160-Gbit/s add/drop multiplexer incorporating a 1-m-long Bismuth Oxide-based ultra-high nonlinearity fiber.

We experimentally demonstrate an all fiber-based, compact add/drop multiplexer (ADM) of a 160 Gbit/s optical time division multiplexed signal using only 1-m length of our fabricated Bi2O3-based step index type optical fiber with an ultra-high nonlinearity of ~1100 W-1.km-1 The ADM is based on the cross phase modulation-induced nonlinear polarization rotation principle and simultaneous add/drop operation was easily achieved by use of a polarization beam splitter after the Bi2O3-based nonlinear fiber. Error-free add/drop operation is readily achieved at multiplexed data rates of both 80 Gbit/s and 160 Gbit/s.

Space-selectively crystallized fiber with second-order optical nonlinearity for variable optical attenuation

We have fabricated BaO-TiO2-GeO2-SiO2-based glass fibers with the oriented space-selectively crystallized structure by laser irradiation and also demonstrated variable optical attenuation induced by electro-optical birefringence change based on second-order optical nonlinearity. The transmittance of a polarized signal is controlled by an electric field applied to the fiber, and the electro-optic fiber devices are operated with extremely low nanowatt electric power dissipation.