Cross-phase Modulation Effect Research Articles

Weak-light ultraslow vector solitons via electromagnetically induced transparency

We propose a scheme to generate temporal vector optical solitons in a lifetime broadened five-state atomic medium via electromagnetically induced transparency. We show that this scheme, which is fundamentally different from the passive one by using optical fibers, is capable of achieving distortion-free vector optical solitons with ultraslow propagating velocity under very weak drive conditions. We demonstrate both analytically and numerically that it is easy to realize Manakov temporal vector solitons by actively manipulating the dispersion and self- and cross-phase modulation effects of the system.

A detailed analysis of cross-phase modulation effects on OOK and dpsk optical WDM transmission systems in the presence of GVD, SPM, and ASE noise

A performance analysis is carried out to evaluate the effect of cross-phase modulation (XPM) on a dispersion-managed 20 Gb/s optical wavelength-division multiplexing (WDM) transmission system using either the on-off keying (OOK) or the different-phase-shifting keying (DPSK) modulation, in the presence of the group-velocity dispersion (GVD), self-phase modulation (SPM), and amplified spontaneous emission (ASE). It is found that to achieve a bit error rate (BER) of 10−9 at a distance of 160 km, a 1.0 dB XPM power penalty is incurred for input channel power of 3 dBm in the OOK transmission and 7 dBm in the DPSK transmission. The power penalty increases with input channel powers and is inversely proportional and exhibits oscillations with respect to the channel separation. The oscillation is evenly spaced for the DPSK but not for the OOK and suggests the presence of optimum separation values. The XPM penalty decreases when a high dispersion fiber is used and increases linearly with increasing dispersion slope. Small residual dispersion can reduce the penalty of nonlinear effects.

All-Optical NRZ-OOK to BPSK Format Conversion in an SOA-Based Nonlinear Polarization Switch

All-optical format conversion from nonreturn-to-zero on-off keying to binary phase-shift keying is demonstrated in a semiconductor optical amplifier-based nonlinear polarization switch. This conversion is realized by cross-phase modulation effect for phase encoding and nonlinear polarization rotation effect for amplitude equalization. In the experiment, error-free operation at 10 Gb/s is achieved with a receiver sensitivity penalty of 1.3 dB after single-ended detection.

Optical Microwave Signal Generation Using a Fiber Loop

The use of a fiber loop mirror for the generation of dispersion tolerant double-sideband with suppressed carrier signals is presented. An asymmetric phase difference within the loop is in charge of filtering out the desired harmonic components at the output. This phase difference is generated by different methods, such as a phase modulator or cross-phase modulation effects in semiconductor optical amplifiers. The loop offers high efficiency and stability within a bandwidth of more than 130 nm. This scheme is suitable for remote signal generation in wavelength-division multiplexing systems.

Polarization Properties of Optical Spectral Components Generated by XPM Effect

We present in this contribution a theoretical description of the polarization properties of optical spectra generated by a cross-phase modulation effect. Experimental corroboration is given by using a measurement technique for polarimetric spectral analysis of given narrow optical spectra, based on a high-resolution optical spectrum measurement technique combined with proper polarization analysis projection. Reported polarization properties indicate the potential use of a polarization filtering for carrier suppression. Such feature leads, for example, to all-optical modulation frequency doubling techniques, as also experimentally demonstrated

Temporal Dynamics of the Alpha Factor in Semiconductor Optical Amplifiers

The temporal evolution of the alpha-factor during pump-probe experiments in semiconductor optical amplifiers (SOAs) is not constant but varies strongly with time. It even takes on negative values for short periods of time. As a consequence, cross-phase modulation (XPM) effects usually lag behind cross-gain modulation effects by several picoseconds. This delay has important consequences for ultrafast operation of all-optical devices based on SOAs. It actually means that not every scheme will be suited for ultrafast operation. In order to properly model the XPM and phase variations within an SOA during a pump-probe experiment, a new parameterization for the alpha-factor is introduced. Inclusion of this model leads to an excellent agreement with the recent 160-Gb/s experiments for both phase and amplitude evolutions of the respective signals with time

A DESIGNED MODEL ABOUT AMPLIFICATION AND COMPRESSION OF PICOSECOND PULSE USING CASCADED SOA AND NOLM DEVICE

A novel technique for the amplification and the compression of an optical pulse is proposed. Based on cascaded a semiconductor optical amplifier (SOA) and a nonlinear optical loop mirror (NOLM), the chirping effect induced by the SOA and the cross phase modulation effect between the signal pulse and control pulse can be utilized to shape the pulse. The picosecond pulse amplification and compression are demonstrated in this paper. A good theoretical model is designed with optimal parameters. Results show that the output signal pulse with high peak power, narrow pulse width, and low pedestal can be obtained using the designed model, which is suited for furture 640 Gbps optical communications. 128 Wu, Tian, and Bao

Cross-phase modulation-induced spectral and temporal effects on co-propagating femtosecond pulses in silicon photonic wires

By performing time-resolved experiments and power-dependent measurements using femtosecond pulses inside submicron cross-section Si photonic-wire waveguides, we demonstrate strong cross-phase modulation (XPM) effects. We find that XPM in Si wires can be significant even for low peak pump powers, i.e., ~15 mW for pi phase shift. Our experimental data closely match numerical simulations using a rigorous coupled-wave theoretical treatment. Our results suggest that XPM is a potentially useful approach for all-optical control of photonic devices in Si wires.

Experimental study of SBS mitigation and transmission improvement from cross-phase modulation in 10.7 Gb/s unrepeatered systems

We experimentally study the effects of cross-phase modulation and stimulated Brillouin scattering limitations in long unrepeatered transmission systems at 10.7 Gb/s. We find significant SBS suppression in wavelength-division multiplexed systems and investigate system performance for different numbers of channels and channel spacing. We find greater than 4 orders of magnitude improvement in bit error rate (BER) with a WDM system in comparison to single channel transmission due to SBS impairment mitigation. Unrepeatered transmission over 323 km with a simple system configuration using low-attenuation fiber, NRZ modulation, and only EDFA amplification is demonstrated with more than 5 dB system margin over the forward error correction (FEC) threshold.

Generation of multicolor vector Kerr solitons by cross-phase modulation, four-wave mixing, and stimulated Raman scattering

We numerically and experimentally show the existence of multicolor vector spatial solitons in a Kerr planar waveguide through the combined effects of cross-phase modulation, four-wave mixing, and stimulated Raman scattering. Mutual spatial guiding of the Raman-Stokes, anti-Stokes, and pump waves is achieved in the high-conversion regime mainly by cross-phase modulation and phase-matched four-wave mixing induced by a power imbalance between Stokes and anti-Stokes components, leading to the generation of a clear-cut sech-shape three-frequency spatial soliton.

Self-phase modulation of radiation in fibreoptic communication lines

Optical nonlinear effects of self-phase and cross-phase modulation and stimulated Brillouin scattering (SBS) determining the data transmission quality in fibreoptic communication lines are studied. The Stokes radiation power upon SBS is calculated taking into account the nonlinear broadening of the optical signal spectrum caused by self-phase modulation. The mechanism of signal distortion caused by the joint action of self-phase modulation and chromatic dispersion is considered. The main theoretical results are verified experimentally.

A model to characterize the effect of cross phase modulation on polarization in an optical fiber transmission system

This paper presents a model that described the process of inter-influence between cross phase modulation (XPM) and polarization effects such as polarization mode dispersion (PMD) and polarization dependant loss (PDL) in an optical fiber communication system. Previous papers have discussed PMD–PDL and PMD–XPM effects in separate models, but in this work we developed a model that is capable of characterizing and evaluating PMD, PDL and XPM simultaneously. From the model, we found that PMD and PDL can be affected by XPM. The presence of XPM changed the vector directions of PMD and PDL in Stokes space.

Analysis of interchannel crosstalk in a dispersion-managed analog transmission link

A technique for computing the effect of cross-phase modulation (XPM) on two copropagating analog channels in an optical fiber link is presented. In this approach, the interaction between the two channels is linearized by keeping the self-phase modulation (SPM) and XPM interactions in the strong optical carrier components only at lowest order and then at the next order, deriving the effect on the modulation components of both channels when the optical carrier is strong relative to the other components of the channel. In contrast to some previously suggested approaches, it is not assumed that the pump is undistorted, and therefore, this method accurately describes distortions due to SPM, XPM, and dispersion management in both channels. This method is easily applied to systems with multiple spans employing dispersion management with loss and gain. The expressions for the received radio frequency power and crosstalk between the two channels when direct detection is used are then provided. Using this approach, new expressions for the amplitude modulation and phase modulation modes of the two channels are derived, and the way they exchange energy when SPM, XPM, and dispersion are all considered is explained. This method yields excellent agreement between theory and experimental data.

Formation and propagation of coupled ultraslow optical soliton pairs in a cold three-state double-Λsystem

We investigate the simultaneous formation and propagation of coupled ultraslow optical soliton pairs in a cold, lifetime-broadened three-state double-Lambda atomic system. Starting from the equations of motion of atomic response and two-mode probe-control electromagnetic fields, we derive coupled nonlinear Schrödinger equations that govern the nonlinear evolution of the envelopes of the probe fields in this four-wave mixing scheme by means of the standard method of multiple scales. We demonstrate that for weak probe fields and with suitable operation conditions, a pair of coupled optical solitons moving with remarkably slow propagating velocity can be established in such a highly resonant atomic medium. The key elements to such a shape preserving, well matched yet interacting soliton pair is the balance between dispersion effect and self- and cross-phase modulation effects of the system.

Cross-phase modulation in long-haul systems with chirped fiber Bragg gratings-based dispersion compensators

The cross-phase modulation (XPM) effect in fiber links with dispersion compensated by chirped fiber Bragg gratings (CFBGs) is analyzed here for the first time. A continuous-wave (CW) signal, referred to as a probe, is used to investigate the impact of XPM on communication systems. The result shows that the XPM in systems using CFBGs as dispersion compensators is greatly suppressed, compared with that of systems using dispersion compensated fiber (DCF). The difference of the dispersion management between the system using DCF and that using CFBGs is demonstrated, too.

Fast analytical assessment of the signal quality in transparent optical networks

Constraint-based routing (CBR) requires a fast and accurate assessment of the different physical degradation effects in optical communications systems. This paper deals with fast analytical approximation formulas describing the induced system penalty due to the dominant nonlinear effects in 10-Gb/s nonreturn to zero (NRZ) transmission systems. This paper concentrates on the multichannel effects of cross-phase modulation (XPM) and four-wave mixing (FWM).

Crosstalk of Signals in Pump Probe Structure with Self-phase Modulation and Cross-phase Modulation

The transmission of optical signals under the effects of cross-phase modulation (XPM) and self-phase modulation (SPM) together in pump-probe wave structure is investigated in intensity modulation-direct detection wavelength division multiplexing (IM-DD WDM) systems. A simple expression for frequency domain IM of probe channel is derived. The analytical method to determine the temporal shape of probe wave when arbitrary wave is inputted in pump channel is confirmed. The impact of channel separation and transmission rate to XPM is assessed. We find that the SPM in pump channel increase temporal intensity modulation index reflected XPM to a certain extent. The analytical result agrees well with numerical simulation.

MULTIPLE-SCALE ANALYSIS OF PLANE WAVE REFRACTION AT A DIELECTRIC SLAB WITH KERR-TYPE NONLINEARITY

Multiple-scale analysis is employed for the analysis of plane wave refraction at a nonlinear slab. It will be demonstrated that the perturbation method will lead to a nonuniformly valid approximation to the solution of the nonlinear wave equation. To construct a uniformly valid approximation, we will exploit multiple- scale analysis. Using this method, we will derive the zeroth- order approximation to the solution of the nonlinear wave equation analytically. This approximate solution clearly shows the effects of self-phase modulation (SPM) and cross-phase modulation (XPM) on plane wave refraction at the nonlinear slab. In fact, the obtained zeroth-order approximation is very accurate and there is not any need for derivation of higher-order approximations. As will be shown, the proposed method can be generalized to the rigorous study of nonlinear wave propagation in one-dimensional photonic band-gap structures.

All-optical chromatic dispersion monitoring of a 40-Gb/s RZ signal by measuring the XPM-generated optical tone power in a highly nonlinear fiber

We experimentally demonstrate an all-optical chromatic dispersion (CD) monitoring technique potential for ultrahigh-speed systems. A monochromatic continuous wave probe is coupled with the tapped-off data signal into a highly nonlinear fiber. An optical tone that is sensitive to CD is generated near the probe wavelength due to the cross-phase modulation effect and is used for CD monitoring. The monitoring window is /spl plusmn/42 ps/nm for 40-Gb/s return-to-zero systems. This monitoring technique is simple and needs no modification at the transmitter.

Interaction of solitary pulses in single mode optical fibres

We attempt to classify interaction of nonlinear optical pulses that propagate in form of solitary waves in single made optical fibres. Two solitary waves launched, by way of incidence, into an optical fibre from a single pulse if the pulses are in-phase as understood from results of inverse scattering transform method applied to the cubic nonlinear Schrodinger equations, (CNLSE\'s). The single CNLSE is then understood to describe evolution of coupled pulses identified with one optical wavelength. More general physical implications abound such that coupled nonlinear Schrodinger equations, (NLSE\'s), have to be used to describe dynamics of the coupled pulses as in the effects of cross-phase modulation, (XPM) and phenomenon of birefringence. Our governing NLSE\'s have the quintic terms. Using a finite-difference method that combines forward-and central-difference approximation schemes, we give results of numerical simulations of coupled in-phase pulses in single pulse system of the NLSE\'s. Simulations are also given for the XPM in presence of walk-off from analytical results. Keywords : Nonlinear Schrodinger equations, solitons, optical pulses, fibre optics. Global Journal of Pure and Applied Sciences Vol. 11(4) 2005: 567-573