Huangping Yan

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.

Spatial Filtering Effect of Tip Clearance Using Capacitance Displacement Sensor

According to structural characteristics and measurement needs of tip clearance of turbine engine and other rotating blade device, a leaves lattice model with vector characteristics is established. Based on measurement principle of the capacitive displacement sensor, the tip clearance measurement model is established. The spatial filtering effect and the impact of the tip clearance measurement results caused by blade thickness, sensing zone size, blade rotation speed and signal sampling rate is analyzed. The research results show that there is a minimum requirement about sensing zone size, blade rotation speed and signal sampling rate under the condition of certain blade thickness. The conclusion provides an important theoretical basis for the design of the tip clearance measurement system.

Study of Temperature Decoupling Fiber Acceleration Sensor Based on the Dual-FP Structure

There is seriously temperature coupling affection in the traditional fiber acceleration sensor, which affects the measurement accuracy. In order to improve anti-interference ability of the sensor, the structural characteristics of the dual-FP cavity is adapted to realize temperature decoupling. Based on the double-beam interference theory, the optimal film thickness requirements, and the output spectrum change of FP cavity caused by the vibration and temperature change is analyzed. Acceleration sensor with structure of the dual-FP cavity and three-bridge is designed. The structure of sensor is analyzed by ANSYS software, such as the thickness of the bridges and the mass size of sensor, and cavity length change caused by equivalent force. Based on the analysis, it can be concluded that the corresponding bridge thickness is 100μm and mass diameter is 0.5mm for the sensor with external diameter of 2 mm and inner diameter of 1.6mm. The resonant frequency of the system is 6.6kHz, and measuring range is 0 ~ 10g.

Fabrication of a monolithic optical receiver for 850nm fiber transmission

A new design of monolithic optical receiver at 850nm for fiber transmission is discussed in this paper. A Spatially Modulated (SM) photodetector and a pre-amplifier are integrated in the optical receiver chip. Some critical parameters of SM photodetector, such as responsivity in different regions, are calculated, and its structure is optimized to get the typical size. And then a novel Spice model of SM photodetector is accomplished in SPECTRE environment based on the numerical calculations above. The simulation results show that the bandwidth and responsivity can reach to 400MHz and 62mA/W at 850nm wavelength. The monolithic optical receiver, including SM photodetector and pre-amplifier with cutoff frequency 780MHz, was successfully fabricated in 0.5μm standard CMOS technology. The transmission rate is 100Mbps by replacing the commercial 100Mbps optical transceiver product. It is expected to be more than 100Mbps if 1000Mbps transceivers are used in test. The experiment and simulation results indicate that the monolithic optical receiver can be applied to 10M/100Mbps fiber transmission.

Realization of a 10M/100Mbps CMOS monolithic optical receiver

A monolithic optical receiver fabricated in standard 0.5μm CMOS process is presented. The fingered doublephotodetector with structure of P+/N-well and N-well/P-substrate is designed. Some critical characteristics of doublephotodetector are analyzed in detail. At 2.5V reverse voltage, the maximum dark current is 10 pA. The intrinsic cut-off frequency is above 100MHz. The measured and simulated responsivity is 0.04A/W and 0.03A/W at 850nm wavelength, respectively. In the testing of double-photodetector, the minimum and maximum of rise time is 2.67ns and 7.11ns while the minimum and maximum of fall time is 2.67ns and 31.78ns. A Spice model of DPD is established for the compatibledesign of OEIC. In simulation of pre-amplifier circuit, the pass-band gain is approximate 18.8 KΩ. The lower cut-off frequency is 7KHz while the upper cut-off frequency is 700MHz. The simulated eye diagram of OEIC at 100Mbps is featured of clear trace, wide eye-opening and small zero-crossing distortion. The small signal bandwidth of OEIC is about 54MHz. The eye diagram at 50Mbps and 250Mbps has some distortion due to direct current malajustment. In the point-to-point optical interconnection, the transmission bit rate of 72Mbps is achieved. The monolithic optical receiver can be applied in 10M/100Mbps optical data transmission.

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.