Electron beam direct-write tunable polymeric waveguide grating filter

We report a tunable electron beam direct-write polymeric waveguide Bragg grating filter based on a negative tone epoxy, The waveguide filter, with a 5-mm-long first-order grating, exhibits a transmission peak of -27 dB and a 3-dB bandwidth of /spl sim/0.8 nm, and there is an excellent agreement between experimental data and simulation results. The temperature response of the filter is also characterized. The rate of change of refractive index dn/dT is /spl sim/ -1.8 /spl times/ 10/sup -4///spl deg/1C at 1550-nm wavelength for both transverse electric and transverse magnetic polarizations, and the rate of change of peak wavelength d/spl lambda//dT is /spl sim/ -0.14 nm//spl deg/C. The tuning performance is comparable to other grating devices fabricated using multiple processing steps.     

Detailed numerical analysis of a four-wave mixing in dispersion-shifted fiber based all-optical wavelength converter of 10 Gb/s single sideband optical signal

We analyze the Q factor and the conversion efficiency of all-optical wavelength converter based on four-wave mixing in dispersion-shifted fibers at 10 Gb/s employing single sideband signal. We find that the Q factor of the converted signal is always higher for upper-single sideband signal with upward conversion in wavelength and for lower-single sideband signal with downward conversion. The four-wave mixing efficiency is higher when the pump wavelength is deviated positively relative to the fiber zero-dispersion wavelength. The used of low dispersion slope allows broad bandwidth and broad dynamic range of pump wavelength. From this study we depict the working characteristics of an all-optical wavelength converter for upper and lower single side band signals, providing guidelines to the utilization of these very promising technologies in the implementation of the future high bit rate all-optical networks.     

All-optical generation of microwave and Millimeter wave using a two-frequency Bragg grating-based Brillouin fiber laser

A novel all-optical technique for microwave/millimeter-wave generation using two-frequency fiber Bragg grating (FBG)-based Brillouin fiber laser is presented. The mechanism for the microwave and millimeter-wave generation is theoretically analyzed. An approximately 33-GHz millimeter wave can be achieved through mixing the pump wave with the third Stokes' wave. In the experiment, an 11-GHz microwave signal is attained. The microwave frequency can be tuned by varying temperature of the fiber Fabry-Pe/spl acute/rot cavity of the Brillouin fiber laser. A more than 100-MHz tuning range around a frequency of 11 GHz is experimentally achieved.     

Monolithically integrated 80-gb/s AWG-based all-optical wavelength converter

We present a monolithically integrated all-optical wavelength converter. The converter consists of four semiconductor optical amplifiers for four separate inputs and an arrayed-waveguide grating. Error-free wavelength conversion with reasonable penalties for a 2/sup 7/-1 pseudorandom binary sequence was shown for a single input 80-Gb/s signal. The device exploits cross-gain/phase modulation in a single amplifier and selects with a filter the blue-chirped spectrum of the new wavelength signal in order to speed up the device response. This device has a dimension of 1.7/spl times/3.5 mm/sup 2/ and it can be operated to convert simultaneously four 80-Gb/s wavelength channels.     

A novel all-optical switch: the wavelength recognizing switch

A new class of an all-optical switch-the wavelength recognizing switch is proposed and experimentally demonstrated. The device uses a control signal to sense the wavelength of the input packet and taps a portion of the data packet to the appropriate output port. The device is based on noncollinear four-wave mixing in a broad-area traveling-wave semiconductor optical amplifier. Measured switching efficiency is +8.2 dB with -28.8 dB of crosstalk. The recognition bandwidth is as narrow as 0.03 /spl Aring/ and the 3-dB switching bandwidth is 42 nm.     

All-optical TDM data demultiplexing at 80 Gb/s with significant timing jitter tolerance using a fiber Bragg grating based rectangular pulse switching technology

We demonstrate the use of fiber Bragg grating based pulse-shaping technology to provide timing jitter tolerant data demultiplexing in an 80 Gb/s all-optical time division multiplexing (OTDM) system. Error-free demultiplexing operation is achieved with /spl sim/6 ps timing jitter tolerance using superstructured fiber Bragg grating based 1.7 ps soliton to 10 ps rectangular pulse conversion at the switching pulse input to a nonlinear optical loop mirror (NOLM) demultiplexer comprising highly nonlinear dispersion shifted fiber (HNLF). A 2-dB power-penalty improvement is obtained compared to demultiplexing without the pulse-shaping grating.     

Theoretical demonstration for signal gain in multiple four-wave mixing processes based on cubic susceptibility medium

An insight into the signal gain in multiple four-wave mixing (MFWM) processes based on a cubic susceptibility medium is theoretically proposed and demonstrated. A dual-pumped fiber optical parametric amplification (FOPA) model is developed with the exact expressions for the signal gain and its 3-dB bandwidth successfully yielded. With these analytical expressions, we show that when pump-1 and pump-2 wavelengths tuned at 1549 and 1551.02nm, the 3-dB bandwidth of the signal gain can be achieved at about 2253.4nm theoretically by properly setting the pumped powers. Numerical simulations show that there is a small pinnacle emerging in the signal gain spectrum owing to the degenerate OPA process occurring. The proposed OPA model can find potential applications in all-optical wavelength conversion, optical amplifier, and all-optical sampling.     

Tunable All-Optical Wavelength Conversion of 160-Gb/s RZ Optical Signals by Cascaded SFG-DFG Generation in PPLN Waveguide

We report, for the first time, tunable all-optical wavelength conversion of 160-Gb/s return-to-zero (RZ) optical signals based on cascaded sum- and difference-frequency generation in a periodically poled LiNbO₃ waveguide. The distorted signals due to limited phase-matching bandwidth during conversion were compensated by spectral reshaping. We achieved error-free tunable wavelength conversion with a bit-error rate of less than 10^-9 for 160-Gb/s RZ signals in a 23-nm tuning range over the C-band     

Integration of a multimode interference coupler with a corrugated sidewall Bragg grating in planar polymer waveguides

We demonstrate the integration of a 3-dB multimode interference coupler with a corrugated sidewall Bragg grating in planar polymer waveguides by direct electron beam writing. Both transmission and reflection spectra of the Bragg grating are measured through this integrated device directly. We use the thermooptic effect to tune the integrated waveguide grating, achieving a tuning range of 6.2 nm and a bandwidth variation of 0.3 nm within a temperature change of 62/spl deg/C.     

Theoretical study of all-optical NRZ to RZ format conversion with tunable pulse width based on XPM in a silicon waveguide

An all-optical format conversion from non-return-to-zero(NRZ) to return-to-zero(RZ) is presented based on cross-phase modulation(XPM) in a silicon waveguide with a detuned optical bandpass filter(OBPF).The simulation results show that the tunable bandwidth of the OBPF leads to RZ signals with tunable pulse width.The conversion efficiency(CE) and the pattern effect of the RZ signal are attributed to the parameters of the pump pulse and the OBPF.The converted RZ signal exhibits lower timing jitter than the NRZ signal.     

基于PPLN波导的全光译码器的设计与研究

随着互联网的发展,网络数据流量极速增长,全光网(AON)概念的提出有利于解决可用带宽受限、信号传输速率较低等问题。其中,全光逻辑信号处理为AON的重要组成部分。根据周期性极化铌酸锂(PPLN)波导的二阶非线性效应原理,将产生的输出信号连续送入不同的PPLN波导进行叠加处理,设计出全光2线-4线译码器的波导级联结构,通过数值计算仿真得到了波形图和眼图,分析了全光2线-4线译码器输出信号的半高全宽(FWHM)、峰值功率、延迟时间和消光比。仿真结果表明:采用PPLN波导级联的方式实现了2线-4线译码器在光域中的逻辑功能,同时保证了光信号的传输质量,为PPLN波导的全光信号处理提供了新的器件类型。     

Wavelength Conversion of High-Speed Phase and Intensity Modulated Signals Using a Highly Nonlinear Chalcogenide Glass Chip

We report all-optical wavelength conversion of high-speed differential phase-shift keyed (DPSK) and on–off keyed (OOK) signals using the nonlinear Kerr-effect in an optical chip. This was enabled by four-wave mixing (FWM) of the signal with a continuous-wave (CW) pump laser in a 7-cm-long dispersion-shifted planar rib waveguide in highly nonlinear $hbox{As}_{2} hbox{S} _{3}$ glass. Both conversion of 40-Gb/s DPSK and 160-Gb/s OOK signals by 33 and 15 nm, respectively, are shown. These are first demonstrations of signal processing by CW-pumped FWM in a chalcogenide waveguide, highlighting its capability to perform phase-preserving operations at high bit rates in chip-scale devices.      

Polarization-independent all-optical switching in a nonlinearGaInAsP-InP highmesa waveguide with a vertically etched Bragg reflector

We have theoretically designed and experimentally demonstrated polarization-independent all-optical switching in a nonlinear GaInAsP-InP highmesa distributed feedback (DFB) waveguide. The device, which is composed of a highmesa waveguide stripe and a vertically etched Bragg reflector, can be simply fabricated using one-step electron beam lithography and a reactive ion etching process. The device is suitable for integration with other photonic devices such as semiconductor optical amplifiers and wavelength converters. The structural birefringence of the device has a dependence on the waveguide parameters such as the refractive index and thickness of core and cladding. The structural birefringence was successfully eliminated by adjusting the width of the highmesa waveguide. The nonlinear vertical-groove DFB highmesa waveguide is attractive for a polarization-independent all-optical switch from the viewpoint of a large grating coupling coefficient, as compared with a grating-loaded DFB highmesa waveguide. The polarization dependence of the grating coupling coefficient has also been investigated experimentally. It is possible to obtain the polarization-independent grating coupling coefficient by adjusting the grating depth in the vertical-groove DFB highmesa waveguide, together with structural zero-birefringence of the device. Polarization-independent all-optical thresholding and bistable switching operations have been successfully demonstrated in the nonlinear vertical-groove DFB highmesa waveguide     

All-optical 2R regeneration based on a compact self-seeded fabry-Pe/spl acute/rot laser diode with an embedded fiber Bragg grating

A cost-effective method, based on the injection-locking technique of a compact self-seeded Fabry-Pe/spl acute/rot laser diode with a 10-mm-long embedded fiber Bragg grating cavity, is proposed and experimentally compared with the two-mode injection-locked scheme for all-optical 2R regeneration at 10 Gb/s. Placing the presented all-optical 2R regenerator after a 50-km fiber significantly improves the transmission performance of a signal over 50- and 100-km fiber links. The power penalties at BER=10/sup -9/ are similar to those of the two-mode injection-locked scheme.     

Matrix analysis of 2-D microresonator lattice optical filters

We present a transfer matrix analysis of a two-dimensional (2-D) filter to study its frequency response functions. The (M/spl times/N) array consists of N independent columns of microring resonators side-coupled to two channel bus waveguides, with equal spacing between columns and each column consisting of M coupled resonators. We show that such a general 2-D lattice network of lossless and symmetric resonators can approximate an ideal bandpass filter characterized by a flat-top box-like amplitude response without out-of-band sidelobes, and a linear phase response. The bandwidth is determined by the coupling factor between resonators. The 2-D periodic structure exhibits nonoverlapping photonic bandgaps arising from the complementary transmission properties of the row and column arrays. The row array behaves as a distributed feedback grating giving rise to narrow bandgaps corresponding to the flat reflection passbands of the filter with out-of-band sidelobes. The column array, on the other hand, acts as a high-order coupled-cavities filter with broad bandgaps that overlap with the sidelobe regions, thereby effectively suppressing the sidelobes. The phase response is linear except near the band edges, where enhanced group delay limits the usable bandwidth of the filter to about 80%. The minimum size of the array required is about 3/spl times/10, but is ultimately limited by waveguide loss.     

Wavelength conversions in quasi-phase matched LiNbO/sub 3/ waveguide based on double-pass cascaded /spl chi//sup (2)/ SFG+DFG interactions

Based on the cascaded nonlinear interactions (/spl chi//sup (2)/:/spl chi//sup (2)/) of sum- and difference-frequency generation (SFG+DFG), a novel all-optical wavelength conversion scheme is proposed for the first time in periodically poled LiNbO/sub 3/ (PPLN) waveguide, in which a double-pass configuration is introduced. The performance of this scheme is thus different from the previous single-pass SFG+DFG scheme. The concept of the "balance condition" is presented to optimize the power and frequencies of the two pump sources. Under this condition, the energy is transferred irreversibly from the pump waves to the SF wave during the forward propagation. The equations describing the SFG can be solved analytically under this condition. Subsequently, the DFG equations are solved under the assumption that the SF wave would be constant during the backward propagation. Theoretical expressions are derived and are found to be consistent with numerical calculations. Compared with the conventional converter based on the cascaded /spl chi//sup (2)/:/spl chi//sup (2)/ interactions of second-harmonic generation and difference frequency generation SHG+DFG, the same conversion efficiency can be achieved in our scheme by employing two pump sources with lower power, or conversely higher conversion efficiency can be reached using two pump sources similar to that used in SFG+DFG scheme. The profile of the conversion efficiency can be further improved by adjusting the wavelengths of the two pump sources. In addition, compared with the single-pass SFG+DFG scheme, the main advantage of this new scheme rests on the fact that the conversion efficiency can be enhanced significantly. The advantages of the double-pass SHG+DFG scheme and the single-pass SFG+DFG scheme are combined in this new design to a great extent.     

Pulse retiming based on XPM using parabolic pulses formed in a fiber Bragg grating

We experimentally demonstrate a novel all-optical all-fiberized pulse retiming scheme incorporating parabolic pulses generated in a linear fashion through pulse shaping in a superstructured fiber Bragg grating. The scheme relies on chirping the signal to be retimed using cross-phase modulation with the broader parabolic clock pulses, and subsequently retiming it through linear propagation in a dispersive medium. We demonstrate the cancellation of up to 4-ps root-mean-square timing jitter for /spl sim/2-ps data.     

Maximum Efficiency of a Two Arm Waveguide Junction (Correspondence)

It is well-known that the efficiency of a two-arm waveguide junction (2-port) depends upon the reflection coefficient /spl Gamma//sub L/ of the load with which one of the arms is terminated. The efficiency is known to vary between the limits 0 and /spl eta//sub m/ (maximum efficiency) as /spl Gamma//sub L/ assumes all possible values within the unit circle. However, there seems to be no published analysis from which one can determine the particular /spl Gamma//sub L/ giving maximum efficiency if the characteristics of the waveguide junction are known.     

Low-voltage high-speed travelling wave InGaAsP-InP phase modulator

A high-speed low-drive-voltage travelling wave electrodes InGaAsP-InP phase modulator operated at 1.55 /spl mu/m is demonstrated. The modulator is fabricated using a multiple quantum-well optical waveguide with an on chip integrated termination resistor. A small signal bandwidth of 35 GHz and a V/spl pi/ of 1.8 V has been demonstrated.     

Multi-wavelength conversion at 10 Gb/s and 40 GHz based on nonlinear effects in HNLF

We present experimental results and numerical simulations of multiple-wavelength conversion of 10 Gb/s non-return-to-zero (NRZ) signals based on 2-pumps four-wave mixing and of 40Gb/s return-to-zero (RZ) signals through supercontinuum (SC) generation in a highly nonlinear fiber (HNLF). Two pumps with a 100 GHz separation located in the region of anomalous dispersion of the HNLF were combined to form a beat signal The 10 Gb/s NRZ signal anchored on ITU grid was converted with gain into 6 new signals and 6 idlers with 100 GHz separation. High quality sc with bandwidth exceeding 50 nm was generated when the HNLF was pumped with 25 dBm average power. Sliced sc can be used as a source for all-optical multicasting.