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Abstract: The performance of analog-to-digital converter (ADC) can be greatly enhanced by preprocessing the ultrafast analog signal using the photonic time-stretch technique. In the previous time-stretch ADC, the amplitude modulation is adopted. The amplitude of stretched signal has nonuniformity after the time-stretch preprocessing and the power of stretched signal is very weak, this will influence on recovering distortionless stretched signal, increase the difficult of detector and sampling. In this paper, we propose the photonic time-stretch ADC employing the phase modulation and the optical coherent detection to eliminate the nonuniformity phenomenon on the amplitude and increase power of stretched signal by adjusting the local oscillation (LO) power. The sampling rate of the ADC can reach 1.56TSa/s by using large dispersion photonic crystal fiber (PCF). [Copyright &y& Elsevier]

In this paper, an analytical model to investigate the parametric amplification (PA) and the PA + stimulated Raman scattering (SRS) in silicon waveguides is put forward. When two pump signals are employed, the PA bandwidth of the probe signal is so large that the Raman contribution has to be considered. When Raman contribution fraction f is set to be 0, only the PA occurs to amplify the probe signal, and when f is set to be 0.043, the PA and the SRS amplify the probe signal at the same time. The signal amplifications of both single and dual pump schemes are investigated by using this model. With this model, three main affecting factors, i.e., zero dispersion wavelength (ZDWL), third-order dispersion (TOD), and fourth-order dispersion (FOD), are discussed in detail. [ABSTRACT FROM AUTHOR]

The performances of a dual-pump parametric and Raman amplification process and the wavelength conversion in silicon waveguides are investigated. By setting the Raman contribution fraction f to be 0.043 in our analytical model, the amplification gain of the probe signal can be obtained to be over 10 dB. The pump transfer noise (PTN), the quantum noise (QN), and the total noise figure (TNF) are discussed, and the TNF has a constant value of about 4 dB in the gain bandwidth. An idler signal generated during the parametric amplification (PA) process can be used to realize the wavelength conversion in wavelength division multiplexing (WDM) systems. In addition, the pump signal parameters, the generated free carrier lifetime and effective mode area (EMA) of the waveguide are analysed for the optimization of signal gain and noise characteristics. [ABSTRACT FROM AUTHOR]

An analysis of how to obtain arbitrary channels with equal reflectivity of sinc-sampled fiber Bragg gratings is provided. The conclusion is that the influence of different sinc-shaped sampling functions on the reflectivity of the multiple channels is significant. In order to obtain equal reflectivity of odd-numbered or even-numbered channels, two kinds of sinc-shaped sampling functions are needed. [Copyright &y& Elsevier]

A novel polarization beam splitter (PBS) based on dual-core photonic crystal fiber (DC-PCF) is proposed in this work. The proposed DC-PCF PBS contains two kinds of lattices and three kinds of air holes to form the asymmetrical elliptic dual-core structure. By using the full-vector finite element method, the propagation characteristics of the proposed DC-PCF PBS are investigated. The simulation results show that the bandwidth of the proposed DC-PCF PBS can reach to 340 nm, which covers the S + C + L + U communication bands, the shortest splitting length is 1.97 mm, and the maximum extinction ratio appears near wavelength 1550 nm. Moreover, the insertion loss of the proposed DC-PCF PBS is very low. It is believed that the proposed DC-PCF PBS has important applications in the field of all-optical communication and network. [ABSTRACT FROM AUTHOR]

In this paper, a novel technique to completely eliminate FWM has been introduced. Alternative circular polarizer have been used to change the polarization of incoming pulses into left-hand and right-hand polarizations before multiplexing in UDWDM optical network with centralized light source. System's performance have been calculated on the bases of Q factor, optical signal to noise ratio, received power and bit error rate. All simulation has been performed in OptiSystem. [ABSTRACT FROM AUTHOR]

We numerically investigate the mid-infrared (MIR) supercontinuum (SC) and SC-based optical frequency comb (OFC) generations when the three optical modes (LP01, LP02, and LP12) are considered in a multimode tellurite photonic crystal fiber (MM-TPCF). The geometrical parameters of the MM-TPCF are optimized to support the multimode propagation and obtain the desired dispersion characteristics of the considered three optical modes. When the pump pulse with center wavelength λ = 2.5 μm, width T = 80 fs, and peak power P = 18 kW is coupled into the anomalous dispersion region of the LP01, LP02, and LP12 modes of the MM-TPCF, the –40-dB bandwidth of the generated MIR SCs can be up to 2.56, 1.39, and 1.12 octaves, respectively, along with good coherence. Moreover, the nonlinear dynamics of the generated SCs are analyzed. Finally, the MIR SCs-based OFCs are demonstrated when a train of 50 pulses at 1-GHz repetition rate is used as the pump source and launched into the MM-TPCF. [ABSTRACT FROM AUTHOR]

Blue-shifted dispersive waves (DWs) are efficiently generated from the red-shifted solitons by coupling the 120 fs pulses into the fundamental mode of the multi-knots of a photonic crystal fiber cladding. When the femtosecond pulses at the wavelength of 825nm and the average power of 300mW are coupled into knots 1-3, the conversion efficiency nDW of 32% and bandwidth BDW of 50nm are obtained. The ultrashort pulses generated by the DWs can be tunable over the whole visible wavelength by adjusting the wavelengths of the pump pulses coupled into different knots. It can be believed that this widely wavelength-tunable ultrashort visible pulse source has important applications in ultrafast photonics and resonant Raman scattering. [ABSTRACT FROM AUTHOR]

Abstract: Based on the optical architecture that uses optical pulse shaping to generate 24GHz-band arbitrary impulse radio ultra-wideband (IR-UWB) signals, an optimization method is proposed to increase the spectral efficiency of the generated signals. Simulated annealing algorithm is used as the optimization method and the spectrum efficiency is utilized as the optimization condition. Numerical analysis shows that power-efficient FCC-Compliant IR-UWB signals are achieved for the given structure. Moreover, the relationship between the spectrum efficiency and the length of pulse trains and the robustness of the optical pulse shaper are analyzed. [Copyright &y& Elsevier]

Efficient Cherenkov radiation (CR) is experimentally generated by a soliton self-frequency shift (SSFS) in a knot of hollow-core photonic crystal fiber (HC-PCF). When the angle of the half-wave plate is rotated from 0° to 45°, the Raman soliton shifts from 2227 to 2300 nm, the output power of the CR increases 8.15 times, and the maximum output power ratio of the CR at 556 nm to the residual pump is estimated to be 20:1. The width of the output optical spectrum at visible wavelengths broadens from 25 to 45 nm, and the conversion efficiency of the CR can be above 28%. Moreover, the influences of the pump polarization and wavelength on the CR are studied, and the corresponding nonlinear processes are discussed. [ABSTRACT FROM AUTHOR]

Highly efficient Cherenkov radiation (CR) is generated by the soliton self-frequency shift (SSFS) in the irregular point of a hollow-core photonic crystal fiber (HC-PCF) in our laboratory. The impacts of pump power and wavelength on the CR are investigated, and the corresponding nonlinear processes are discussed. When the average power of the 120 fs pump pulse increases from 500 mW to 700 mW, the Raman soliton shifts from 2210 nm to 2360 nm, the output power of the CR increases by 2.3 times, the maximum output power ratio of the CR at 539 nm to that of the residual pump is calculated to be 24.32:1, the width of the output optical spectrum at the visible wavelength broadens from 35 nm to 62 nm, and the conversion efficiency ɳ of the CR in the experiment can be above 32%. [ABSTRACT FROM AUTHOR]

Using a photonic crystal fiber with a zero dispersion wavelength of the fundamental mode at 780 nm designed and fabricated in our lab, the ultraviolet and mid-infrared continua are generated by cross-phase modulation between red-shift solitons and blue-shift dispersive waves. The dependences of continuum on the pump power and wavelength are investigated. With the pump working at 820 nm, when the pump power increases from 300 to 500 mW, the bandwidths of ultraviolet and mid-infrared continua change from 80 to 140 nm and 100 to 200 nm, respectively. The wavelength of ultraviolet continuum is below 246 nm, and the wavelength of mid-infrared continuum exceeds 2500 nm. Moreover, the influences of pump power on wavelength and conversion efficiency of different parts of continua are also demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, we optimize a proposed all-optical quantization scheme based on soliton self-frequency shift (SSFS) and pre-chirp spectral compression techniques. A 10m-long high-nonlinear photonic crystal fiber (PCF) is used as an SSFS medium relevant to the power of the sampled optical pulses. Furthermore, a 10m-long dispersion flattened hybrid cladding hexagonal-octagonal PCF (6/8-PCF) is utilized as a spectral compression medium to further enhance the resolution. Simulation results show that 6-bit quantization resolution is still obtained when a 100m-long dispersion-increasing fiber (DIF) is replaced by a 6/8-PCF in spectral compression module. [ABSTRACT FROM AUTHOR]

We propose a novel lumped time-delay compensation scheme for all-optical analog-to-digital conversion based on soliton self-frequency shift and optical interconnection techniques. A linearly chirped fiber Bragg grating is optimally designed and used to compensate for the entire time-delays of the quantized pulses precisely. Simulation results show that the compensated coding pulses are well synchronized with a time difference less than 3.3 ps, which can support a maximum sampling rate of 151.52 GSa/s. The proposed scheme can efficiently reduce the structure complexity and cost of all-optical analog-to-digital conversion compared to the previous schemes with multiple optical time-delay lines. [ABSTRACT FROM AUTHOR]