Tatsuo Nagashima

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.

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.

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.

Highly nonlinear bismuth-oxide fiber for supercontinuum generation and femtosecond pulse compression

Highly nonlinear normally dispersive bismuth-oxide fiber shows promise for applications such as supercontinuum generation and femtosecond pulse compression in the telecommunications-wavelength range. To generate a wideband and flat supercontinuum spectrum, the balance between fiber nonlinearity and normal group velocity dispersion (GVD) is important. Highly nonlinear bismuth-oxide fiber exhibits a large nonlinearity due to the small effective area and nonlinear index of the host glass material. The fiber also has a relatively flat dispersion profile over a large wavelength range. Utilizing these features, we generate a smooth unstructured supercontinuum between 1200 and 1800 nm. This supercontinuum is passed through a grating pair, and pulses, originally of 150-fs length, are compressed to 25 fs.

Output performance investigation of self-phase-modulation-based 2R regenerator using bismuth oxide nonlinear fiber

We investigate the feasibility of the use of 1-m length of our fabricated bismuth oxide-based nonlinear fiber (Bi-NLF) for the implementation of a Mamyshev-type 2R regenerator that is based on self-phase-modulation-induced spectral broadening followed by spectral filtering, and evaluate the regeneration performance in both experimental and theoretical ways from a perspective of system application. Owing to the excellent dispersion and chi(3) nonlinearity characteristics of our 1-m-long Bi-NLF, a nonlinear S-shape power transfer curve is readily obtained. A Q-factor improvement of a noisy 10-Gb/s return-to-zero signal by 1.2 dB is achieved by use of the regenerator

Clock recovery and demultiplexing of high-speed OTDM signal through combined use of bismuth oxide nonlinear fiber and erbium-doped bismuth oxide fiber

We explore the ultimate potential offered by state-of-the-art Bismuth oxide-based optical fiber technology in a high-speed optical phase-locked loop-based clock recovery subsystem for an optical time-division multiplexed (OTDM) signal, in which the use of optical fiber-based devices has been considered to be inappropriate due to its tight requirement of short optical loop length. Here, we experimentally demonstrate the implementation of a compact all-fiber-based OTDM receiver incorporating both clock recovery and demultiplexing functions by use of short lengths of Bismuth oxide-based nonlinear fiber and erbium-doped Bismuth oxide fiber. Successful clock recovery and subsequent error-free demultiplexing are readily achieved at a data rate of 80 Gb/s. The clock recovery subsystem is also shown to be operable at 160 Gb/s.