Zhaoxi Wu

Tunable wavelength conversion based on cascaded sum and difference frequency generation with double-conversion configuration using M-QPM-LN waveguides

In this paper, we proposed a novel variable operation of a DC-OFS based on double SFG+DFG nonlinearity process with double-pass configuration for the first time. In this scheme, the available nonlinear crystal length is used twice: forward for SFG and backward for DFG in each conversion and this device is called double-pass SFG+DFG wavelength converter as the SF wave propagates twice in the waveguide. We used the novel multiple-quasi-phase-matched LiNbO3 (M-QPM-LN) waveguides having the continuously-phase-modulated domain structure, which can be operated by multiple pump wavelengths with minimum loss of efficiency. The frequency spacing of control signal-a is twice as large as the control signal-b. Conversion bandwidth is the frequency difference of control signal-b and control signal-a. We discussed Double-SFG+DFG-OFS with double-pass configuration theoretically and gave the formula of the input power of input signal, the two controlling light and pump light, which proposed a simple and feasible way to optimize the performance of the device. In this scheme, the advantages of the cascaded SFG+DFG scheme and the DC-OFS scheme are combined to a great extent. We believe this double-pass cascaded SFG+DFG DC-OFS must be better than single-pass cascaded SFG+DFG DC-OFS for constructing future flexible photonic networks.

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.

Double-Conversion Optical Frequency Shifter Using Multiple Quasi-Phase-Matched LiNbO3 Waveguides

In this paper, we proposed a variable operation of a DC-OFS based on double SFG+DFG (Double-SFG+DFG-OFS) nonlinearity process for the first time. We studied the principle and configuration of three DC-OFS in detail both theoretically and experimentally. In order to compare with Double-DFG-OFS and Double-SHG+DFG-OFS, we also used two four-channel-controlling multiple-quasi-phase-matched LiNbO3 wavelength converters and got ten different outputs spreading across a wavelength range of as broad as 35 nm by changing the combination of two controlling wavelengths of the two wavelength converters. And one channel signal was converted to shorter and longer wavelength and the same wavelength by changing the controlling wavelengths. We got higher conversion efficiency compared with the other two DC-OFSs mentioned above. We used novel M-QPM-LN wavelength converters having a continuously-phase- modulated domain structure, which can be operated by multiple pump wavelengths with minimum loss of efficiency. The periods were 14.8μm. The phase of the periodic poling was continuously modulated to satisfy the QPM condition at four different wavelengths. The frequency spacing of control signal-b is twice as large as the control signal-a. The operating temperatures were 102.5 and 100.5 C for the first and the second QPM-LN wavelength converters, respectively.

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.

Research of the Technology Based on Fiber Bragg Grating for Measurement of Temperature Rise of Electrical Appliances

A new method of using fiber Bragg gratings as the sensing elements in the measurement of temperature rises of electrical appliances is proposed in this paper. Comparing with the conventional measurement method with thermocouples, the new method can overcome problems such as electromagnetic interference, hazard of electrical leakage, etc. The characteristics and key components employed in the measuring system are analyzed and discussed. The experimental results show that the temperature rises of electrical appliances under test can be obtained quickly and accurately with the specifically designed sensors made by optical fiber Bragg gratings.

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.