[show abstract][hide abstract] ABSTRACT: An ultrawide-bandwidth, superluminescent light-emitting diode (SLED) utilizing multiple layers of dots of tuned height is reported. Due to thermal effect, the superluminescent phenomenon is observed only under pulse-mode operation. The device exhibits a 3 dB bandwidth of 190 nm with central wavelength of 1020 nm under continuous-wave (cw) conditions. The maximum corresponding output power achieved in this device under cw and pulsed operation conditions are 0.54 mW and 17 mW, respectively.
[show abstract][hide abstract] ABSTRACT: Ultra-wide bandwidth superluminescent diodes (SLDs) using multiple layers of InAs-GaAs quantum dots (QDs) with engineered height are realised. A tilted and tapered active region is used to reduce the effective reflectivity from the facets. A 3 dB emission bandwidth up to 140 nm centred at 1100 nm is achieved at a continuous-wave drive-current of 600 mA. It is shown that varying the height of the dots from one layer of dots to another within the active region considerably broadens the emission spectrum of the QD-SLDs compared to those made of similar layers of inhomogeneous QDs.
[show abstract][hide abstract] ABSTRACT: We demonstrated an ultra-broadband wavelength converter based on co-polarized dual-pumping four-wave mixing technique in a dispersion-flattened photonic crystal fiber. Over 380-nm wavelength conversion range from 1260 nm to 1640 nm has been achieved. By sweeping the wavelengths of the second pump laser, we have obtained the relationship between the wavelength conversion efficiency and the converted data signals, which are consistant with our theoretical analysis. The OSNR of the converted data signals are up to 30 dB.
[show abstract][hide abstract] ABSTRACT: We have designed, fabricated and characterized self-assembled InAs/InGaAsP QD-waveguide devices around 1.55 mum. In order to obtain optimal performance, we have investigated several QD-based semiconductor optical amplifiers (SOAs) / lasers with different core geometry and doped profiles. To make the fair comparison between QD-SOA and QW-SOA, InAs/InGaAsP QW-SOAs with the same structure and the doped profiles have been designed and characterized. The experimental results indicate the QD-SOA is much better than QW-SOA in term of optical spectral bandwidth, temperature sensitivity and output power stability. The 3-dB and 10-dB bandwidths of the amplified spontaneous emission (ASE) spectra of the QD-SOA are 150 nm and 300 nm around 1520 nm. By using CW pump and probe signals we have demonstrated a non-degenerated four-wave mixing (ND-FWM) process and the experimental results indicate that the asymmetry of the FWM conversion efficiencies is eliminated by using the QD-SOA. To make use of the inhomogeneous broadening which is one of the specific properties of QD waveguide devices, we have designed and investigated the QD-based multi-wavelength semiconductor laser. A stable multi-wavelength laser output with a 93-channel multi-wavelength laser with maximum channel intensity non-uniformity of 3-dB were demonstrated on the basis of a single InAs/InGaAsP QD F-P cavity chip. All channels were ultra-stable because of the inhomogeneous gain broadening due to statistically distributed sizes and geometries of self-assembled QDs.
[show abstract][hide abstract] ABSTRACT: A 93-channel multiwavelength laser with maximum channel intensity non-uniformity of 3.0 dB over a wavelength range from 1638 to 1646 nm was demonstrated on the basis of a single 4500 mum-long InAs/InGaAsP quantum dot Fabry-Perot cavity chip. All channels were stable because of inhomogeneous gain broadening due to statistically distributed sizes and geometries of self-assembled quantum dots
[show abstract][hide abstract] ABSTRACT: Birefringence measurement of planar silica-on-silicon waveguides with high resolution is proposed and demonstrated using a ring resonator. For the presented waveguide sample, the measured birefringence at 1550 nm was (4.115±0.094)×10<sup>-6</sup> at 25.000±0.001°C. The minimum low-level birefringence resolution of 6.266×10<sup>-7</sup> was experimentally realised.
[show abstract][hide abstract] ABSTRACT: By using a co-polarized pumping technique in a polarization-insensitive semiconductor optical amplifier, we have demonstrated a multi-channel polarization-insensitive wavelength converter with uniform conversion efficiency across the whole gain profile range of the semiconductor optical amplifier.
[show abstract][hide abstract] ABSTRACT: By using two orthogonally-polarized pump beams, an ultrabroad tunable wavelength converter is demonstrated with uniform efficiency and equalized signal-to-noise ratio (SNR) through four-wave mixing (FWM) in an 1500-nm semiconductor optical amplifier (SOA). This device allows the conversion of the input data signal to lower or higher frequencies with nearly-constant conversion efficiency and SNR over a 10.66 THz tuning range. This result is a significant improvement of both the conversion efficiency and the SNR as compared with the conventional FWM-based wavelength converters. We have also investigated the effect of parameters of both input power and wavelength of pump P2 on conversion efficiency and SNR of the wavelength-converted signals.
[show abstract][hide abstract] ABSTRACT: Multifiber Bragg grating (FBG) sensor arrays are being used in the health monitoring of aerospace structures and civil engineering works, as well as the environment monitoring. However, the field interrogations of multi FBG sensors are still a big challenge due to the lack of portable, robust, high performance multi sensor interrogation devices. We have found that by thermally scanning an arrayed waveguide gratings (AWG) based demultiplexer, a device deployed in the telecommunication networks, multi FBG sensors can be precisely monitored simultaneously. The measurement resolution of this technique can be better than one picometer (equivalent to 0.1degC for temperature sensing) and the measurement time can be as short as milliseconds. Owning to the small size and ruggedness of AWG, it is potentially feasible to fabricate an all solid (no moving parts), palm size, robust and high-resolution interrogator for multi FBG sensor applications
[show abstract][hide abstract] ABSTRACT: A multi-wavelength laser comb with the total output power of over 30 dBm is obtained from an ytterbium / erbium (Yb/Er) co-doped double-cladding fiber ring laser by incorporating a section of multimode Yb/Er optical fiber into an otherwise single-mode fiber ring cavity to form a spatial mode beating filter.
[show abstract][hide abstract] ABSTRACT: We have developed a widely tunable, narrow-linewidth, simultaneous triple-wavelength oscillation erbium-doped fiber ring laser (EDFRL), which can produce double-wavelength oscillations with the same polarization output, as well as another widely tunable wavelength oscillation with orthogonal polarization from 1522.2 nm to 1595.9 nm. By using this EDFRL along with a method of measuring polarization-mode dispersion (PMD) in optical fibers based on a broad-band orthogonal-pump four-wave mixing in a semiconductor optical amplifier (SOA), we have measured the PMD values of optical fibers, which are in good agreement with values measured by means of commercial PMD testing equipment. We have also proposed several novel devices for in-field PMD measurement and monitoring on dense wavelength-division multiplexed (DWDM) traffic-carrying links, which will significantly reduce the cost and time of the PMD testing in the running DWMD networking systems.
[show abstract][hide abstract] ABSTRACT: We describe the design and development of a novel tunable fiber laser and its application to polarization-mode dispersion measurements of optical fibers using broad-band orthogonal-pump four-wave mixing in a semiconductor optical amplifier.