A coherence-free and reconfigurable filter based on semiconductor optical amplifier (SOA) is proposed and experimentally demonstrated. A high coherent RF-modulated light source is converted to an incoherent light source by employing the cross-gain modulation of amplified spontaneous emission (ASE) of the SOA. The inversely modulated ASE is sliced by an optical wavelength demultiplexer to realize a stable transversal microwave filter. Reconfigurability of the filter can be achieved by controlling the number and apodization of the taps. The filters with two, three and four taps are experimentally demonstrated.
A new cascaded microwave photonic filter consisting of two or more infinite impulse response (IIR) filters based on
active loops. is presented. Owing to wavelength conversion, the interference between the modulated optical signals of
different taps from different active loops can be avoided and the stable transmission characteristic of the cascaded filter
can then be achieved. The cascaded filter can increase the free spectral range (FSR) and the Q value significently by
designing the FSR differences of the IIR filters. The cascaded filter with two IIR filters is demonstrated, and the
measured results of a high Q of 3338 and rejection ratio of about 40 dB are obtained. The tunability can also be realized.
We demonstrated experimentally 40 Gbit/s all-optical format conversions between return-to-zero (RZ) and nonreturn-to-
zero (NRZ) using a fiber delay interferometer (FDI) and a single semiconductor optical amplifier (SOA). Firstly, 40 Gbit/s data format conversion from RZ to NRZ is realized using a FDI with temperature control and an optical bandpass filter (BPF). Then, 40 Gbit/s data format conversion from NRZ to RZ is implemented, using four-wave mixing (FWM)
effect of SOA, by injecting synchronously NRZ signal and clock pulses into a single SOA. Presented method has some distinct advantages including multi-channel parallel processing, easy integration, convenient tuning, good stability, and
so on, which has potential to be used in future optical networks that could combine wavelength division multiplexing
(WDM) and optical time domain multiplexing (OTDM) transmission techniques.
A novel design of 2-to-4 photonic digital decoder has been proposed and experimentally demonstrated successfully at 40
Gbit/s. The scheme is implemented by employing differential phase shift keying (DPSK) signals, bit-inverse properties
of delay interferometers (DIs), as well as cross gain modulation (XGM) of semiconductor optical amplifiers (SOAs).
Correct logic results with high extinction ratios, clear and wide open eyes have been obtained simultaneously, without
using any additional input beams. Furthermore, the great potential for hybrid or monolithic integration of delay
interferometers and semiconductor optical amplifiers may make the scheme promising candidates for the future ultrafast
photonic signal processing applications.
We propose and experimentally demonstrate a novel all-optical microwave filter with high quality factor (Q). It is based
on a recirculating delay line (RDL) loop in which a semiconductor optical amplifier (SOA) is followed by a tunable
narrow-band optical filter and a 1x2 10:90 optical coupler. Converted signal used as a negative tap is generated through
wavelength conversion employing the cross-gain modulation (XGM) of the amplified spontaneous emission (ASE)
spectrum of the SOA. The converted signal can circulate in the RDL loop so that the proposed filter realizes a high Q
factor response after photo-detection. The 1x2 10:90 coupler is employed to extract 10% optical power from the loop as
output. A frequency response with a high Q factor of 543, a rejection ratio of 40 dB is experimentally demonstrated.
A tunable and switchable single-longitudinal-mode (SLM) dual-wavelength fiber laser incorporating a reconfigurable
dual-pass Mach-Zehnder interferometer (MZI) filter and its application in microwave generation was proposed and
demonstrated. By incorporating a dual-pass MZI into an erbium-doped fiber ring cavity, tunable and switchable SLM
dual-wavelength operation can be conveniently realized.
An all-optical UWB pulses generation and modulation scheme based on a semiconductor optical amplifier and a DWDM
is proposed and demonstrated, which has potential applications in multiuser UWB-Over-Fiber communications systems.
Using proposed scheme, pulse amplitude modulation (PAM), pulse polarity modulation (PPM) and pulse shape
modulation (PSM) can be conveniently realized.
We experimentally demonstrate all-optical clock recovery (CR) from the nonreturn-to-zero (NRZ) data without any
preprocess measure. Multi-quantum-well (MQW) Fabry-Pérot semiconductor optical amplifier (FP-SOA) plays the dual
role of the data format converter and the clock recovery device. To achieve amplitude equalization of the recovered clock
pulses, a self-nonlinear polarization switching (SNPS) including the FP-SOA itself, two polarization controllers (PCs)
and a polarization beam splitter (PBS) is employed. Using the presented scheme, stable and low jitter 35.80 GHz optical
clock pulses were directly extracted out from input NRZ data. This scheme has some distinct advantages such as being
transparent to data format, free preprocess, free pre-amplification, convenient tuning, good tolerance to long "0s" data,
and good tolerance to wavelength drifting of input data.
We present a multiwavelength mode-locked fiber ring laser incorporating a semiconductor optical amplifier (SOA) and a
Fabry-Perot semiconductor optical amplifier (FP-SOA). SOA is mode-locked by an injected external optical signal, act
as loss modulator, and FP-SOA serves as a tunable comb filter. Our laser source can generate 19 synchronized
wavelength channels with the extinction ratio of about 21 dB, each mode-locked at 10 GHz, and modelocked pulse width
is about 40 ps. Oscillation wavelengths band and wavelength spacing can be tuned by adjusting bias current and a
tunable optical delay line (ODL) or a temperature controller, respectively. Polarization insensitive devices ensure that the
output power is rather stable.
Nanoimprint lithography (NIL) is a candidate of alternative, low cost of ownership lithography solution for
deep nano-meter device manufacturing12. For the NIL template pattern making, we have been developing the processes
with 100keV SB EB writer and 50keV VSB EB writer to achieve the fine resolution of near 20nm1-7. However,
inspection of nanoimprint template posed a big challenge to inspection system due to the small geometry, 1x comparing
to 4x of Optical mask and EUV mask. Previous studies of nanoimprint template inspection were performed indirectly on
a stamped wafer and/or on a round quartz wafer13. Electron beam inspection (EBI) systems have been widely used in
semiconductor fabs in nanometer technology nodes. Most commonly EBI applications are electrical defects, or voltage
contrast (VC) defects detection and monitoring8-11.
In this study, we used a mask EBI system developed by Hermes Microvision, Inc. (HMI) to directly inspect a
NIL template with line/space and hole patterns half pitched from 22nm to 90nm and with program defects sized from
4nm to 92nm. Capability of inspection with 10nm pixel size has been demonstrated and capability of capturing program
defects sized 12nm and smaller has been shown. This study proved the feasibility of EBI as inspection solution of
nanoimprint template for 22nmHP and beyond.
We demonstrate a multiwavelength semiconductor optical amplifier (SOA) fiber ring laser with a dual- pass Mach-
Zehnder interferometer (MZI) filter. Two SOAs provide enough gain and wider gain spectrum for more wavelength
lasing. The dual-pass MZI with a high extinction ratio (ER) serves as comb filter. 82 wavelengths within a power
deviation of 5 dB with the signal-to-noise ratio of 30 dB oscillate simultaneously.
We present a multiwavelength mode-locked fiber ring laser incorporating two semiconductor optical amplifiers (SOAs)
and a segment of dispersion-compensating fiber (DCF). One SOA is mode-locked by an injected external optical signal
and act as loss modulator and assistant gain medium. The other SOA is not modulated by injected signal and only severs
as gain medium. Two SOAs synchronously provide enough cavity gain for high repetition rate multiwavelength
oscillation. A segment of commercial DCF is employed to introduce intracavity dispersion and functions as a self-tuned
comb filter. Our laser source can generate 16 synchronized wavelength channels, each mode-locked at 10 GHz. 16
wavelengths from 1581.96 to 1597.52 nm is with a power deviation of about 4 dB and the mode-locked pulse average
width is 39 ps. Oscillation wavelengths can be smoothly tuned to appointed wavelengths and the output power is rather
stable.
We demonstrate a fiber ring laser with a dispersion compensation fiber (DCF) and a delayed
interferometer (DI), which is able to switch eleven wavelengths one by one. In ring cavity,
DCF supplies different effective cavity lengths for different wavelengths, DI generates a
wavelength comb corresponding to the ITU grid, a flat-gain erbium-doped fiber amplifier
(EDFA) provides uniform gain for each lasting wavelength, and a semiconductor optical
amplifier (SOA) not only acts as active modulator, but also alleviates homogeneous
broadening effect of EDFA. Stable pulse trains with a pulsewidth about 40 ps at 10 GHz have
been obtained by injecting external optical control signals into the laser. Wavelength switching
process among eleven wavelengths is achieved by merely tuning an intracavity optical delay
line.
All-optical clock recovery (CR) from 20-Gbit/s nonreturn-to-zero differential phase-shift-keying (NRZ-DPSK) signal is
demonstrated experimentally by using Polarization-Maintaining Fiber Loop Mirror Filter and semiconductor optical
amplifier (SOA) fiber ring laser. Only by adjusting polarization controller (PC), NRZ-DPSK signal were conveniently
and fast converted to pseudo return-to-zero (PRZ) signal via PMF-LMF. Then the PRZ signal is injected into the SOA
fiber laser for CR. The recovered clock signals with the extinction ratio of 10 dB and the root-mean-square timing jitter
of 850 fs is achieved under 231-1 pseudorandom binary sequence NRZ-DPSK signals measurement.
A hybrid actively and passively mode-locking semiconductor optical amplifier fiber ring laser based on nonlinear
polarization rotation was presented, where intensity modulator not only acted as modulator but also polarizer. Under the
hybrid mode-locking mechanism, output pulse is with some new characters. So, a theoretical model that describes the
SOA fiber ring laser was developed and system parameters effects on mode-locking pulse are discussed.
The dynamic single-mode and modulation performance of λ/4 phase-shifted distributed feedback laser
diode with chirped grating (QWS-CG-DFB) are analyzed theoretically. The numerical simulation
shows that, In contrast to purely QWS-DFB laser, the enhanced dynamic single-mode suppression ratio
(SMSR) can be reached by QWS-CG-DFB laser; Under the smaller biasing current, the modulation
band-width in presence of chirped grating is narrower, this difference shrinks for larger biasing current;
For large signal modulation, the chirped grating is helpful to increase the output extinction ratio, but
worsens the frequency chirping.
In this paper, based on self-reproduction theory, harmonic mode-locked (HML) and rational harmonic mode-locked (RHML) fiber ring lasers consisting of two semiconductor optical amplifiers (SOAs) was numerically researched, respectively. Harmonic mode locking makes a target of obtaining ultra-short pulse, but, in rational harmonic mode locking, it urgently needs to be solved that pulse amplitude becomes uneven with the increase of the order of rational harmonic, which results in the different work conditions of both. After obtaining the optimal work condition, the system parameters effects on the characteristic of HML pulse and the quality of pulse-amplitude equalization in rational harmonic mode locking have been investigated, respectively.
A novel scheme for all-optical frequency multiplication/recovery based on the semiconductor optical amplifier (SOA) ring cavity is proposed and investigated numerically. The results show, for a 2.5GHz driving pulse train, it can be generated 5-25GHz repetition rate pulse trains with low clock amplitude jitter (CAJ), polarization independence and high peak power. Furthermore, the extraction of the clock signal from a pseudorandom bit sequence (PRBS) signal can be realized based on the proposed scheme.
This paper proposes a fast and robust algorithm for classification and recognition of ships based on the Principal Component Analysis (PCA) method. The three-dimensional ship models are achieved by modeling software of MultiGen, and then they are projected by Vega simulating software for two-dimensional ship silhouettes. The PCA method as against the Back-Propagation (BP) neural network method for simulated ship recognition using training and testing experiments, we can see that there is a sharp contrast between them. Some recognition results from simulated data are presented, the correct recognition rate of PCA method improved rapidly for each of the five ship types than that of neural network method, the number of times a ship type is recognized as one of the other ships is reduced greatly.
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