K. K. Chow

Polarization-insensitive widely tunable wavelength converter based on four-wave mixing in a dispersion-flattened nonlinear photonic Crystal fiber

Polarization-insensitive widely tunable wavelength conversion has been demonstrated using four-wave mixing in a 64-m-long dispersion-flattened nonlinear photonic crystal fiber. A 3-dB conversion range over 40 nm (1535-1575 nm) is obtained with a flat conversion efficiency of -16 dB and a polarization sensitivity of less than 0.3 dB. The measured power penalty is less than 1 dB for a 10-Gb/s converted nonreturn-to-zero signal at 10/sup -9/ bit-error rate.

Ultrahigh Sensitivity Refractive Index Sensor Based on Optical Microfiber

We demonstrate a nonadiabatic microfiber sensor with a taper diameter of few micrometers. The modal interference caused by the abrupt taper results in a sinusoidal spectral response. The wavelength shift arising because of the changes in the external refractive index is found to be significant, achieving a maximum sensitivity of 18681.82 nm/RIU. The measured results show good agreement with the theoretical predictions. The high sensitivity and the simplicity offer the sensor the potential for many real applications.

Four-wave mixing in a single-walled carbon-nanotube-deposited D-shaped fiber and its application in tunable wavelength conversion.

We report the first experimental observation of four-wave mixing (FWM) in single-walled carbon nanotubes (SWCNTs) deposited on a Dshaped fiber. FWM-based tunable wavelength conversion of a 10 Gb/s nonreturn-to-zero signal is demonstrated using a 5-centimeter-long CNT-deposited D-shaped fiber. A power penalty of 4 dB power is obtained in the 10 Gb/s biterror- rate measurements.

Spectral filtering from a cross-phase modulated signal for RZ to NRZ format and wavelength conversion.

All-optical return-to-zero (RZ) to non-return-to-zero (NRZ) format conversion has been demonstrated using cross-phase modulation in a dispersion-shifted fiber, which can in principle work with different signal bit rates and does not require any external pulse duplicator. The output wavelength-converted signal is obtained from filtering of the broadened optical spectrum. A power penalty of 2 dB is obtained at 10-9 bit-error-rate level in a 10 Gb/s conversion experiment.

Widely tunable wavelength converter using a double-ring fiber laser with a semiconductor optical amplifier

Widely tunable wavelength conversion has been demonstrated using broad-band orthogonal-pump four-wave mixing in a semiconductor optical amplifier placed at the intersection of two fiber ring lasers. The all-optical wavelength converter operates without using any external pump source. A 3-dB conversion-range over 40 nm is obtained. The measured power penalty is 1.5 dB for a 2.5-Gb/s converted signal at 10/sup -9/ bit error rate.

A widely tunable wavelength converter based on nonlinear polarization rotation in a carbon-nanotube-deposited D-shaped fiber.

We demonstrate widely tunable wavelength conversion based on cross-phase modulation induced nonlinear polarization rotation in a carbon nanotubes (CNTs) deposited D-shaped fiber. A 5-centimeter-long CNT-deposited D-shaped fiber is used as the nonlinear medium for wavelength conversion of a 10 Gb/s non-return-to-zero signal. Wavelength tunable converted signal over 40 nm is obtained with around 2.5-dB power penalty in the bit-error-rate measurements.

All-optical signal regeneration with wavelength multicasting at 6×10 Gb/s using a single electroabsorption modulator

All-optical signal regeneration with wavelength multicasting has been demonstrated using cross-absorption modulation in a single electroabsorption modulator for the first time. We show that the input signal wavelength can be simultaneously converted to 6 different wavelengths at 10 Gb/s with signal regeneration. The output extinction ratio, the linewidth, and the pulse shape show a significant improvement. A negative power penalty of 2 dB is obtained at 10-9 bit-error-rate level.

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.

Operation-Switchable Bidirectional Pulsed Fiber Laser Incorporating Carbon-Nanotube-Based Saturable Absorber

We present an operation-switchable bidirectional ring-cavity pulsed fiber laser incorporating a carbon-nanotube-based saturable absorber and a polarization-dependent four-port circulator. By manipulating the intra-cavity polarization state of light, two sets of mode-locked pulses in terms of fundamental repetition rate and pulse width can be achieved separately from the same laser cavity. In clockwise direction, the laser generates mode-locked output pulse train with a pulse width of 600 fs and a fundamental repetition rate of 12.68 MHz. While in counter-clockwise direction, the laser generates mode-locked pulses with a pulse width of 480 fs and a fundamental repetition rate of 16.46 MHz. Furthermore, the same laser cavity can produce bidirectional Q-switched output pulse trains with synchronized repetition rate. Such synchronized repetition rate is linearly proportional to pump power. The results show a multi-functional pulsed fiber laser with selectable output pulse trains.

Widely tunable wavelength conversion with extinction ratio enhancement using PCF-based NOLM

A widely tunable wavelength conversion scheme has been demonstrated using a 64-m-long dispersion-flattened high-nonlinearity photonic crystal fiber in a nonlinear optical loop mirror. Wavelength conversion range of over 60 nm with a 10-Gb/s return-to-zero signal was obtained with the output extinction ratio (ER) maintained above 13 dB. The proposed scheme can also improve the output ER and remove the bit-error-rate floor if a degraded signal is used.