We simulated the evolution of self-similar parabolic pulses (similaritons) in a normally dispersive
fiber amplifier. The rate of development of a Gaussian pulse into the asymptotic parabolic regime
has been studied. The model has been applied to an optical transmission system with a fiber
amplifier. By calculating the Q-factor, we numerically determined the signal to noise performance of
the pulse train along fiber length. For the parameters we used, a 6m long fiber amplifier with 20 dB
gain is capable of amplifying 200Gb/s initial chirp-free Gaussian pulses of duration 0.4ps with no
distortion and additional noise. The trade-off between pulse width and amplifier length has been
studied.
KEYWORDS: Logic devices, Signal to noise ratio, Electronic support measures, Semiconductor optical amplifiers, Logic, Global system for mobile communications, Hole burning spectroscopy, Mach-Zehnder interferometers, Beam controllers, Picosecond phenomena
A scheme to realize fiber-based all-optical Boolean logic functions including XOR, AND, OR and NOT
based on a semiconductor optical amplifier with a closely stacked Stranski-Krastanow InAs/GaAs quantum
dot layers is proposed. Rate equations is given to describe the population dynamics of the carrier in the
device, as well as the nonlinear dynamics including carrier heating and spectral hole-burning. The model is
used to simulated the cross gain and cross phase modulation in the device that are related to the logic
processes. Results show with QD excited state serving as a carrier reservoir, this type of QD device is
suitable for high speed operations with ultra fast carrier and phase relaxation. All optical logic operation
can be carried out at up to 250 Gb/s.
A scheme for high speed clock and data recovery using an electroabsorption modulated laser and a
semiconductor optical amplifiers arranged in an optical-electrical-optical (OEO) loop has been
demonstrated. By injecting the 80Gb/s optical data into the OEO ring, the 10GHz clock tone is traced
and amplified in the loop. A 10GHz electrical clock and, a 10 GHz optical clock are recovered
simultaneously.
We present model calculations of gain at 1550 nm for Er-Yb double clad amplifiers as a function of pump power, pump
wavelength, signal input power, and fiber length. The absorption coefficient of Yb varies ( by a factor of ~ 5) with the
pump wavelength in the range of 910 to 990 nm. However, semiconductor lasers may be available only at certain
wavelengths. Thus it is important to calculate optical gain and amplified output power as a function of pump wavelength.
The calculation shows that significant optical gain and amplified output power can be obtained even if the pump laser
wavelength is not at the peak absorption wavelength. The gain decreases with increasing input signal. We show that a
high power Er-Yb co-doped double-clad fiber amplifier also exhibits high gain for Yb transition near 1060 nm. This is
not unexpected since the input pump causes population inversion in Yb. More than 100 W of amplified power can be
obtained using 24m long fiber with 300 W of total pump power by using side-pumping method. Side pumping increases
the efficiency over end pumping for high output power.
An all-optical logic NOR gate operating at 40 Gb/s has been demonstrated using an SOA-based Mach-Zehnder interferometer (MZI). An optical loop mirror is used as a delayed interferometer to reshape the return-to-zero (RZ) NOR sequence from the MZI output port. The performance of the NOR operation is numerically analyzed by solving the rate equation of an SOA. An increase in signal output power enhances the Q factor and extinction ratio. Faster SOAs such as quantum-dot SOAs can achieve higher Q value. The demonstrated technique has potential for optical logic operation at ultrahigh speed
80Gb/s All-optical Boolean function XNOR has been demonstrated using a dual four wave mixing scheme in two identical highly nonlinear fibers. A numerical model based on nonlinear Schrodinger equation (NLS) in fiber has been employed to simulate the wave mixing process. The NLS equations have been solved using the split-step Fourier method. From the numerical model, system transmission rate is predicted to be as high as 250Gb/s.
All optical XOR, AND, OR, and, NOR functionality has been demonstrated experimentally using
semiconductor optical amplifier (SOA) based devices at 40 Gb/s, 80 Gb/s. The performance of
the optical logic operations has been analyzed by solving the rate equation of the SOA
numerically. The high-speed operation is limited by the gain and phase recovery times in the
SOA. In order to solve these limitations, a differential scheme for XOR operation has been
experimentally investigated. This scheme is potentially capable of XOR operation to > 100 Gb/s.
All-optical XOR operation has been demonstrated using a semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) and delayed interferometer (DI) at 80 Gb/s. The DI is based on a polarization maintaining loop mirror (PML). The results show using the PML-DI to perform differential scheme can improve the pulse quality of the XOR result.
In this paper, detailed analyses of the conversion efficiency in high-speed clock recovery based on Mach-Zehnder (MZ) modulator has been carried out. The theoretical results show the conversion efficiency changes with RF driving power and the mixing order. For high order clock recovery, the cascaded MZ modulator provides higher conversion efficiency. A study of clock recovery at 160 Gb/s using the cascaded MZ modulator has been carried out. The experimental results agree with the results of the analysis.
The performances of all-optical logic gates AND, OR, XOR, NOT based on quantum dot semiconductor optical amplifier (QD SOA) devices have been simulated. The saturation power, optical gain and optical
phase response of a QD SOA has been analyzed numerically using a rate equation model of quantum dots embedded in a wetting layer. The calculated response is used to model the performance of the logic gates. Impacts of injection current and the input signal power on system quality factor have been studied. For the parameters used in this paper, all-optical logic gates using QD-SOA is capable of operating at speeds of ~ 250Gb/s.
In this work, an optical short pulse generator is designed consisting of a pulse compressor and cascaded notch filter type repetition rate doublers. The performance characteristics such as pulse width and peak power as a function of design parameters are studied. The pulse compressor is optimized based on the simulation results. The 6ps wide pulses at 20 GHz repetition rate directly generated from mode-locked fiber laser (MLL) are compressed to 1.25ps wide pulses. Using a set of polarization maintaining fiber (PMF) loop mirrors the repetition rate is quadrupled and stable 1.45 ps wide pulse train at 80GHz is achieved.
In this work, we demonstrate clock recovery from a patterned 160Gb/s optical-time-division-multiplexed (OTDM) return-to-zero (RZ) data stream. A cascaded LiNbO3 Mach-Zehnder modulator is employed as an efficient optical-electrical mixer. A phase-locked-loop (PLL) is used to lock the cross-correlation component between the optical signal and a local oscillating signal. As a result, clock signal at 10GHz is extracted from the 160Gb/s optical TDM signal. The measured root-mean-square (RMS) timing jitter of the 10GHz clock signal is ~ 130fs.
All optical XOR, AND, and, OR functionality has been demonstrated experimentally using semiconductor optical amplifier (SOA) based devices at 40 Gb/s, 80 Gb/s. The performance of the optical logic operations has been analyzed by solving the rate equation of the SOA numerically. The high-speed operation is limited by the gain and phase recovery times in the SOA. In order to solve these limitations, a differential scheme for XOR operation has been experimentally investigated. This scheme is potentially capable of XOR operation to > 100 Gb/s.
In this paper, we demonstrate clock recovery from a patterned 160Gb/s optical-time-division-multiplexed (OTDM) return-to-zero (RZ) data stream. A cascaded LiNbO3 Mach-Zehnder modulator is employed as an efficient optical-electrical mixer. A phase-locked-loop (PLL) is used to lock the cross-correlation component between the optical signal and a local oscillating signal. As a result, clock signal at 10GHz is extracted from the 160Gb/s optical TDM signal. The measured root-mean-square (RMS) timing jitter of the 10GHz clock signal is ~ 130fs.
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