Yu Chong-Xiu

Six-bit all-optical quantization using photonic crystal fiber with soliton self-frequency shift and pre-chirp spectral compression techniques

In this paper, we propose an optical quantization scheme for all-optical analog-to-digital conversion that facilitates photonics integration. A segment of 10-m photonic crystal fiber with a high nonlinear coefficient of 62.8 W−1/km is utilized to realize large scale soliton self-frequency shift relevant to the power of the sampled optical signal. Furthermore, a 100-m dispersion-increasing fiber is used as the spectral compression module for further resolution enhancement. Simulation results show that 317-nm maximum wavelength shift is realized with 1550-nm initial wavelength and 6-bit quantization resolution is obtained with a subsequent spectral compression process.

Broadband Convergence of 40 GHz-ROF and 10-Gb/s WDM-PON Systems in the Duplex Access Network

A broadly converged 40G-ROF and 10-Gb/s WDM-PON multi-service access system is proposed and experimentally demonstrated. This scheme consists of an integrated system of 40G-ROF and 10-Gb/s WDM-PON simultaneously transmitting independent 2.5-Gb/s wireless and 10-Gb/s wire signal. At the base station, it employs a remodulation scheme, which is achieved by remodulating the upstream OOK signal on the DPSK downstream signal, to reduce the cost of the base station. The transmission experiment is carried out over a 25-km-long single mode fiber (SMF-28). The results show that the sensitivities of downstream PON and ROF signal are ?14.5 dBm and ?21.5 dBm, respectively, and the sensitivity of upstream signal is ?25.3 dBm.

155 Mb/s-10 Gb/s combined FSK-IM/optical label-packet modulation signals 100 km transmission over standard single mode fiber using mid-span spectral inversion by four-wave mixing in an SOA

This paper introduces the mid-span spectral inversion by four-wave mixing in a commercially available semiconductor optical amplifier (SOA) with a length of about 1.5 mm to optical label switching network based on combined frequency shift keying (FSK)-intensiy modulation (IM)/optical label-packet modulation to overcome the dispersion limitation of fiber. The 155 Mb/s–10 Gb/s combined FSK/IM signal is experimentally transmitted over a 100 km standard single mode fiber. 10−10 and 10−9 BER (bit error ratio), or even better, is achieved for the FSK label and IM packet, respectively. The –19 dB power conversion efficiency is obtained for –1 nm wavelength detuning.

Highly sensitive digital optical sensor with large measurement range based on the dual-microring resonator with waveguide-coupled feedback

We propose a novel high-performance digital optical sensor based on the Mach—Zehnder interferential effect and the dual-microring resonators with the waveguide-coupled feedback. The simulation results show that the sensitivity of the sensor can be orders of magnitude higher than that of a conventional sensor, and high quality factor is not critical in it. Moreover, by optimizing the length of the feedback waveguide to be equal to the perimeter of the ring, the measurement range of the proposed sensor is twice as much as that of the conventional sensor in the weak coupling case.

Code synchronization based on lumped time-delay compensation scheme with a linearly chirped fiber Bragg grating in all-optical analog-to-digital conversion

We propose a novel lumped time-delay compensation scheme for all-optical analog-to-digital conversion based on soliton self-frequency shift and optical interconnection techniques. A linearly chirped fiber Bragg grating is optimally designed and used to compensate for the entire time-delays of the quantized pulses precisely. Simulation results show that the compensated coding pulses are well synchronized with a time difference less than 3.3 ps, which can support a maximum sampling rate of 151.52 GSa/s. The proposed scheme can efficiently reduce the structure complexity and cost of all-optical analog-to-digital conversion compared to the previous schemes with multiple optical time-delay lines.

Performance Investigation of All-Optical NRZ-to-Manchester Format Conversion with SOA-MZI Based XOR Logic Gate

All-optical format conversion between non-return-to-zero (NRZ) and the Manchester code is implemented by using an optical exclusive-OR (XOR) logic gate based on a semiconductor optical amplifier Mach-Zehnder Interferometer (SOA-MZI). There is 10 Gbit/s all-optical NRZ-to-Manchester conversion implemented in our simulation system and BER performance of the format conversion is investigated. Transmission performances of the converted Manchester coded signal are discussed in terms of transmission length and received optical power.

Design of Microstructured Optical Fibres with Elliptical Air Holes for Properties: Single-Polarization Single-Mode and Nearly Zero Ultra-Flattened Dispersion

By using the complex finite element method (FEM) under perfectly matched layer (PML) boundary conditions, dispersion properties of microstructured optical fibres (MOFs) with elliptical air holes are analysed by changing the pitch and sizes of air holes belonging to the inner three rings. Meanwhile, the confinement loss of the fundamental mode is engineered to achieve the single-polarization single-mode transmission. Based on this analysis, a novel design of MOFs for properties of the single-polarization single-mode and the nearly zero ultra-flattened dispersion between 1 ps km−1 nm−1 in the wavelength range of 1.2–1.6 μm is presented for the first time.

Temperature-Insensitive Chemical Sensor with Twin Bragg Gratings in an Optical Fibre

To reduce temperature sensitivity of the fibre Bragg grating (FBG) chemical sensor, a simple method is proposed by measuring the peak wavelength difference between an etched FBG and an un-etched one in an optical fibre. Thermal characteristics and chemical sensitivity of the sensor are experimentally investigated. The experimental results indicate that the etched FBG and the rest one have almost the same thermal response, and concentration changes of the surrounding chemical solutions can be detected by measuring the peak wavelength difference between them. The sensor has been used to measure the concentrations of propylene glycol solutions and sugar solutions, and it could detect 0.7% and 0.45% concentration changes for them with an optical spectrum analyser in resolution of 10 pm.

Improvement of Amplitude-Shift-Keying Signal Quality by Employing an Effective Spectrum Equalization Method in a Combined FSK/ASK Modulation Scheme

A simple, economical and applicable spectrum equalization method is implemented by employing a reshaping filter in the combined frequency-shift-keying/amplitude-shift-keying modulation scheme to improve the quality of amplitude-shift-keying optical signal. The 3-dB improvement for eye diagram height is experimentally demonstrated.

Influence of channel power and pumping configuration on the gain profile of distributed Raman fibre amplifier

The influence of channel power and pumping configuration on the gain profile of a distributed Raman fibre amplifier has been experimentally measured. The experimental results show that the influence is significant and should be considered during the gain flatness optimization of the distributed Raman fibre amplifier.