Ruifang Ye

All-optical wavelength converter based on self-phase modulation in highly nonlinear photonic crystal fiber

A simple architecture of all-optical wavelength conversion in a highly nonlinear bismuth oxide-based photonic crystal fiber (PCF) is proposed, which consists of an erbium-doped fiber amplifier, a polarization controller, a nonlinear medium PCF, two tunable fiber Fabry-Perot filters and an optical isolator. Self-phase modulation is utilized to induce spectral broadening for all-optical wavelength conversion. The desired dispersion properties can be tailored by the parameters of bismuth oxide-based PCF microstructure. The propagation loss at 1550nm is about 0.8dB/m. The nonlinear coefficient is expected to be 1100W-1km-1 by using bismuth oxide-based glass and reducing the effective core area. The mode-field diameter of PCF is estimated to be 1.98μm and the predicted effective core area is 3.3μm2. The intermediate high numerical aperture fibers between bismuth oxide-based PCF and single-mode fibers are considered to reduce the splicing loss. The obtained results show that the all-optical wavelength converter has a potential of high conversion efficiency, wide conversion bandwidth, ultrafast response time, compact configuration and low insertion loss etc.

Novel scheme to increase the operation speed of a SOA for all-optical wavelength conversion

All-optical wavelength converters (AOWCs) are considered to be important components in future wavelength-division-multiplexed (WDM) networks. Cross gain modulation schemes in semiconductor optical amplifiers (SOA) are promising candidates for an all-optical wavelength conversion application due to the simple implementation and effective conversion. However, the slow gain recovery time of SOA limits the maximum operation speed and causes unwanted pattern effects. This paper provides a novel scheme for wavelength conversion enables ultra-fast conversion speed. On the one hand, we utilize a three-wavelength-device (TWD) to reduce the recovery time of the SOA. On the other hand, we use an optical band pass filter (OBF) which central wavelength is blue shifted with respect to the central wavelength of the probe beam to increase the frequency response. The combination of a reduction of the SOA recovery time and an increase of the frequency response enables conversion speed potentially to achieve 160 Gb/s or even faster.

Recirculating configuration all-optical wavelength conversion by self-phase modulation in a highly nonlinear photonic crystal fiber

A novel architecture of all-optical wavelength conversion in a highly nonlinear bismuth oxide-based photonic crystal fiber (PCF) is demonstrated. Self-phase modulation is utilized to induce spectral broadening for the all-optical wavelength converter. A recirculating configuration is designed to obtain the twice spectral broadening. Therefore, wavelength conversion is achieved. The design and the simulation of PCF are demonstrated. The desired dispersion properties can be tailored by the parameters of bismuth oxide (Bi2O3) PCF microstructure. The propagation loss at 1550nm is about 0.8dB/m. The simulation results of PCF indicate the relationship of the effective index of the fundamental mode, the mode effective area and the holes pitch of PCF. The nonlinear coefficient is expected to be 1100W-1km-1 by using bismuth oxide-based glass and reducing the effective core area. The mode-field diameter of PCF is estimated to be 1.98μm and the predicted small effective core area is 3.3μm2. The design of Bi2O3-based PCF and the intermediate high numerical aperture fibers between Bi2O3-based PCF and single-mode fibers are considered to reduce the splicing loss. The obtained results show that the wavelength converter has a potential of wide conversion bandwidth, high response time, simple configuration and low insertion loss etc.

Cascaded wavelength conversion based on cross-gain modulation and cross-phase modulation in SOAs

All-optical wavelength converters (AOWCs) that utilize nonlinearities in semiconductor optical amplifiers (SOAs) have attracted considerable research interest. AOWCs based on cross gain modulation (XGM) have a large dynamic range of the input optical signal power but a low extinction ratio (ER) and a high chirp, whereas AOWCs based on cross phase modulation (XPM) provide a low chirp and a high ER but suffer from a relative small input power dynamic range. We point out that there seems to be some complementarity between XGM and XPM. Based on this, we propose a novel scheme for cascaded wavelength conversion based on cross gain modulation and cross phase modulation in SOAs thus is expected to have a high ER and a large input power dynamic range simultaneously. The wavelength conversion operation includes two stages, that is, XGM in the first stage followed by the stage of XPM. In the XGM stage, we use a band pass filter to increase the frequency response of the SOA. In the XPM, we use the bidirectional input scheme for MZI to improve the response of XPM and cancel XGM-induced intensity unbalance to get a relative perfect interference.

Design of a novel high-speed magneto-optic modulator

A novel high-speed magneto-optic (MO) modulator which consists of an integrated wire grid polarizer (WGP), Bi-YIG waveguide with cladding layer and conducting micro-strip line is proposed. With the integrated WGP, this MO modulator is faster, more accurate and more stable because it is not only completely driven by electric signals but also has no mechanically moving parts. Moreover, it is compact-structured and low-cost. Large Faraday rotation is obtained with specific arrangement of the directions of the bias magnetic field and the modulation RF magnetic field. Optical route and optic-electrical detect circuit are also designed and analyzed.

Polarization-Insensitive All-Optical Wavelength Converter Based on Four-Wave Mixing in a Highly Nonlinear Photonic Crystal Fiber Using a Dual-Pump Configuration

A basic scheme of the polarization insensitive four-wave-mixing all-optical wavelength conversion with a copolarization dual-pump configuration in a highly nonlinear photonic crystal fiber (PCF) is demonstrated. With two fiber Bragg Gratings and a Faraday rotator mirror, both the pumps and the signal make a dual pass through a highly nonlinear PCF. The rotation of the signal polarization by the Faraday rotator mirror guarantees that both orthogonal polarization components of the signal will efficiently mix with the two pumps to produce a polarization-insensitive multi-wavelength conversion. The design and simulation of the bismuth oxide-based PCF indicate that the desired dispersion properties can be tailored by the geometrical parameters of PCF microstructure. The propagation loss at 1550nm is about 0.8dB/m. The nonlinear coefficient is expected to be 1100W-1km-1 by using bismuth oxide-based glass and reducing the effective core area. The mode-field diameter of PCF is estimated to be 1.98μm and the predicted effective core area is 3.3μm2. The polarization insensitive four-wave-mixing wavelength converter with copolarization dual-pump configuration shows the small polarization sensitivity, the high conversion efficiency and the simultaneous multi-wavelength conversion.

All-optical wavelength conversion based on cascaded effect of cross-gain modulation and cross-phase modulation in SOAs

All-optical wavelength conversion plays a major role in providing the wavelength flexibility in optical communication networks. All-optical wavelength converters (AOWCs) based on cross-gain modulation (XGM) and cross-phase modulation (XPM) in semiconductor optical amplifiers (SOAs) have attracted considerable research interest. In this paper, we propose a novel scheme for cascaded wavelength conversion based on cross-gain modulation and cross-phase modulation in SOAs. The wavelength conversion operation in the proposed scheme includes two stages, that is, XGM in the first stage followed by the stage of XPM, and thus is expected to have a high ER and a large input power dynamic range simultaneously.

Study on the laser beam transformation and its measurement in laser processing

The shape and energy distribution of laser beam directly define its applications in laser processing. In order to cater for different laser processing requirements, the input beam always needs to be transformed. The transformation between the solid beam and ring beam can be realized by the axicon-based optical devices. A beam transformation optical system, which uses a pair of positive axicon and negative axicon is designed and analyzed. The novelty of the optical system is not only that they can focus the laser beam on a ring pattern or solid beam pattern, but also that they can change the diameter of patter easily by adjusting the separation of the two conical lenses. The optical system is analyzed based on the geometry optical theory. By adjusting the separation of the convergent conical lens and the divergent conical lens, different shapes and the energy distributions are gained. At last, a measurement method of the beam profile is introduced which based on charge coupled device (CCD) The results show that the axicon-based beam transformations raise the effectiveness of laser and have a wide application prospect in laser processing field.

All-optical Wavelength Converter with Recirculating Configuration Based on Self-Phase Modulation in a Highly Nonlinear Photonic Crystal Fiber

A novel scheme is proposed to achieve all-optical SPM-based wavelength conversion in a bismuth oxide-based highly nonlinear photonic crystal fiber. It consists of erbium-doped fiber amplifier, optical circulator, Fiber Fabry-Perot filters, photonic crystal fiber and fiber Bragg grating. Owing to SPM, a recirculating configuration is designed to induce the further spectral broadening and wavelength conversion is achieved with a tunable Fiber Fabry-Perot filter. The simulation results of bismuth oxide-based photonic crystal fiber indicate that the effective index of the fundamental mode increases monotonically with the increase in the hole pitch, or the decrease in the ratio of the hole diameter to the hole pitch. The mode effective area steadily increases with the hole pitch. The nonlinear coefficient, which is beneficial to shorten the fiber length and reduce the required optical power, is expected to be 1100W-1km-1 by using bismuth oxide-based glass with high nonlinear refractive index and reducing the effective core area with holey microstructure. The mode-field diameter of bismuth oxide-based is estimated to be 1.98μm and the predicted small effective core area is 3.3μm2. The propagation loss at 1550nm is about 0.8dB/m. The obtained results show that SPM-based PCF-WC has a potential of wide conversion bandwidth, high response time, simple configuration and low insertion loss etc.