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In this paper, the operation of π-phase shifted distributed feedback Raman fiber (DFB-RF) laser above threshold condition is analyzed theoretically. The nonlinear optical phenomena such as self phase modulation (SPM) and cross phase modulation (XPM) have significant effect on the performance of DFB-RF laser. The numerical results show that the nonlinear effects cause to the saturation of output power and the value of saturated power is dependent on the fiber length. It is found that, the operation wavelength of stokes modes of DFB-RF laser varies in above threshold condition as a result of nonlinear optical properties of the fiber. Simulation is performed by using transfer matrix method to solve three coupled nonlinear wave equations which describe the propagation of pump, forward and backward Stokes waves. The nonlinear SPM and XPM effects are considered in the presented theoretical model.

To meet the growing internet data traffic, transmission capacity of fibers has to be increased. For that Dense Wavelength Division Multiplexing (DWDM) technique has been used nowadays. However, there is a nonlinear distortion which degrades the transmitted signal and hence decreases the overall system performance. The nonlinearities that arise in WDM systems are Cross Phase Modulation (XPM), Stimulated Raman Scattering (SRS) and Four Wave Mixing (FWM). Also it is found that these nonlinearities depend upon input power, dispersion and channel spacing. In this paper two methods have been proposed to eliminate FWM and SRS effect. Firstly, the fiber optic link has been analyzed by increasing the input power. From the analysis it is found that the FWM effect get increased by increasing the input power. But the transmission power should be optimum to transmit the information in long haul fiber optic link. The FWM effect is reduced by placing the Circular Polarizers alternatively in each transmitter before passing through the fiber link. Another method which has been proposed to eliminate SRS is optimum allocation of input power. The unwanted power tilt due to SRS effect is reduced by allocating the transmitted power randomly. The simulation studies are carried out using OPTSIM and OPTISYSTEM software. The simulations have been carried out for multichannel systems with equal spacing. It is found that the optimum power level allocation also improved the system performance.

In this paper, we investigate the modulational instability (MI) in an elliptical birefringent positive-negative index coupler. Also, we derive the general expression for instability gain by taking into account cross-phase modulation (XPM), self-steepening (SS) and intrapulse Raman scattering. The instability gain is attained. Using standard linear stability analysis, particularly, we study different configurations of the birefringence with self-steepening or intrapulse Raman scattering effects on MI for both normal and anomalous group velocity dispersion regimes. We observe that the instability gain exhibits significant changes due to the effects of the cross-phase modulation. Finally, we show that efficient control of the MI can be realized by adjusting the self-steepening and intrapulse Raman scattering term, even in the presence of different configurations of the birefringence.

A new system of coupled Ablowitz-Ladik equations is introduced where cubic nonlinearities from intensities of both waveguide arrays are included. The Hirota bilinear transform is formulated and is used to derive breathers periodic in space or time. One spatially periodic solution is utilized to verify the lowest order conservation laws. Algebraically localized rogue wave modes with pulsating properties are obtained from breathers in the limit of large wave periods. Incorporating additional modes of cubic nonlinearities, namely, cross phase modulations, in two arrays of oscillators on an integer lattice can further enhance the modeling capability in optical physics.

This paper presents a theoretical analysis of a closed formula for nonlinear crosstalk due to self-phase modulation (SPM) and cross phase modulation (XPM) in wavelength division multiplexing (WDM) systems. The influence of channel spacing and attenuation on the system behavior is modeled and investigated. The system under consideration is a standard single-mode fiber (SSMF) with a single-span distributed Raman amplifier (DRA) and is operating at 100 Gbps.

We study the impact of modified saturable nonlinearity on modulational instability (MI) criteria in a coupled birefringent fiber using pulse propagation technique. Based on the standard linear stability method, we enquire nonlinear self/cross phase modulation on MI in a coupled Kundu–Eckhaus (KE) equation in the absence of nonlinear four-wave mixing expression. Using the modified KE equation, we study the role of modified form of saturable nonlinearity on MI in a birefringent KE model with the adjustable self/cross phase modulation coefficients. In the case of KE without nonlinear saturation and four-wave mixing, we observed that the cross phase modulation (XPM) has less induced the instability region on MI in coupled birefringent fiber system as compared to self phase modulation (SPM) case as shown in Ref. Parasuraman (2021). But, in saturable KE model showed different characteristics of MI and growth rate of profile in a coupled birefringent fiber system in the presence of particular emphasis values of the nonlinear terms as depicted in Ref. Mohanraj (2021). This study shows the novel results of MI criterion in a coupled KE birefringent media with the help of modified type of saturable nonlinearity and both SPM/XPM values. From the above-detailed discussion, the modified form of saturable nonlinearity plays an important role for MI generation in a KE birefringent media. However, the modified nonlinear saturation KE model more helps to generate ultrashort pulses and soliton or solitary wave in a coupled nonlinear birefringent fiber with the help of 3D images.

The present work shows the role of nonlinear saturation effects on modulational instability (MI) in a birefringent media with the help of nonlinear wave propagation technique. Using the Kundu–Eckhaus (KE) equation, we investigate both self phase and cross phase modulation effect on MI in a birefringent media without four wave mixing term. We consider only KE equation model without the existence of four wave mixing expression and the standard linear stability theory is presented to the appropriate model. In the case of modified KE equation, we discuss the role of MI in a birefringent fiber system with the help of conventional type of saturation effect. In the case of KE without four wave mixing, we observed that the SPM plays a vital role on MI in coupled birefringent fiber compared to XPM as shown in Ref. Parasuraman (2021). But, In saturable KE has different MI characteristic as well as growth rate of profile in birefringent model with the help of particular emphasis values of the nonlinear parameters. However, the nonlinear saturation KE model more helps to generate soliton or solitary wave in coupled nonlinear birefringent fiber in the presence of both SPM and XPM.

We study the modulational instability of nonlinear wave propagation in birefringent fiber of the Kundu–Eckhaus equation without four wave mixing term and analysis the effect of self phase modulation and cross phase modulation. The model of Kundu–Eckhaus equation in the absence of four wave mixing term are consider and apply the linear stability analysis to the Kundu–Eckhaus equation. Modulational instability criteria are found from linearized equations for small perturbations. Using modulational instability criteria, the self phase modulation and cross phase modulation effects on optical wave propagation in birefringent fiber are discussed.

In the dense wavelength-division multiplexing (DWDM)-based 5G fronthaul network, cross-phase modulation (XPM) would become more obvious to degrade the signal when the interval between the channels becomes narrower. Meanwhile, theoretically, the relative polarization angle between the adjacent channels tends to be more consistent in the same case, that it appears effective on the suppression of XPM by using the orthogonal polarization method In this paper, the orthogonal polarization method has been analyzed and applied on multi-channel transmission for suppressing the XPM effect at a 5G fronthaul system which is illustrated on both simulation and experimental results. By the simulation in the case of 25 Gbit/s per channel, ∼ 0.6/ ∼ 0.8 dB sensitivity improvement can be achieved in orthogonal-polarization-state after 10 km/15 km transmission, comparing with the same-polarization-state. In the real experiment, ∼ 0.7 dB/ ∼ 0.9 dB sensitivity improvement has been realized under the same condition as the simulation. This is relatively-more effective comparing with the published results in using one single method to suppress XPM in the WDM systems.

We theoretically study the spatial focusing of surface polaritons (SPs) in a negative index metamaterial-atomic gas interface waveguide system, based on cross phase modulation (XPM) in a tripod type double electromagnetically induced transparency (EIT) scheme. In the linear region, we realize the low-loss stable propagation of SPs, and the group velocities of the probe and signal fields are well matched via double EIT. In the nonlinear region, we show that giant enhancement of the XPM can be obtained. Using a narrow optical soliton in free space, we realize spatial focusing of the SPs solitons, including bright, multi bright, and gray solitons. The full width at the half-maximum of the SPs soliton can be compressed to about ten nanometers, thus, even nanofocusing can be obtained. The results obtained her e have certain theoretical significance for nano-scale sensing, spectral enhancement and precision measurement.

Silicon is a nonlinear material and optics based on silicon makes use of these nonlinearities to realize various functionalities required for on-chip communications. This article describes foundations of these nonlinearities in silicon at length. Particularly, self phase modulation and cross phase modulation in the context of integrated on-board and on-chip communications are presented. Important published results and principles of working of these nonlinearities are presented in considerable detail for non-expert readers.

We experimentally demonstrated tunable delays using mutrally modulated cross-gain modulation (MM XGM) in erbium-doped fiber (EDF) with a new co-direction structure. The group velocity of the signal light can be controlled by the saturating light at an arbitrary wavelength in the EDF gain bandwidth. We have observed slow light propagation with a group velocity as low as 146.4 m/s, which means a 88.8 ms delay, and an advancement of 11.2 ms after a 13 m EDF at the same time. This provides a greater enhancement on the delay or advancement compared to the previous experiment. Furthermore, we confirmed the influence on delay or advancement by varying the pump power, the input power of the saturate light. Also, we discussed the influence of recovery time, the modulation depth of the saturating light and the modulation frequency on the modulation gain. This attractive approach could be one of the suitable solutions for real applications.

The feasibility of implementing an All-Optical (AO) XOR gate for 320 Gb/s data pulses using Quantum Dot (QD) based Reflective Semiconductor Optical Amplifiers (RSOAs) in a Folded Mach–Zehnder Interferometer (FMZI) is investigated using detailed numerical models. Detailed performance comparisons are made between the conventional QD-SOA based MZI XOR and the specific scheme. The influence of various parameters such as SOA length, input optical powers, rear-facet reflectivity, and bias current on the XOR gates output quality are investigated. The results indicate that the gain recovery time in the QD-RSOA can be reduced to approximately 50% of its value in the QD-SOA, which can help avoid restoring sophisticated gain recovery acceleration techniques. It is shown that at low input powers and high bit rates the MZI XOR fails to perform the logic operation, while the FMZI XOR can deliver a good performance at data rates as high as 320 Gb/s with reducing the power consumption of the structure. The simulations demonstrate an about 5 dB (1 dB) improvement on the XOR output extinction ratio (amplitude modulation) for 320 Gb/s input bit sequence. The combination of the ultrafast gain dynamics of QD materials with the inherent advantages of RSOA devices and using the former in the latter inside the high-performance FMZI can be utilized to realize power-efficient ultrafast signal processing and switching functions while being cascadable and scalable for constructing more complex AO circuits.

Polarization-Switched QPSK (PS-QPSK) can offer a higher tolerance to fiber nonlinearities than Polarization Multiplexed QPSK (PM-QPSK), albeit with 25% loss of spectral efficiency. While improved performance has been shown experimentally, a thorough study of inter-channel nonlinearities in these systems has not been performed. Here we numerically study two separate manifestations of cross phase modulation (XPM) generated by these two formats; XPM-induced phase noise (XPM-PN) and XPM-induced polarization crosstalk (XPM-PC). We find that in both dispersion-compensated (DC) and dispersion uncompensated (DUC) systems, greater XPM-PN is generated by PS-QPSK interferers, whereas greater XPM-PC is generated by PM-QPSK interferers. While the combined effect of these distortions provides similar penalties in either system, this finding may help inform the design of efficient nonlinear equalizers.

The two coupled counterpropagating nonlinear magnetoinductive wave modes are analyzed theoretically in split ring resonator chain with Kerr nonlinear interaction. Starting from a general nonlinear lattice equation based on a quasi-discreteness approach we derive two coupled nonlinear Schrodinger equations governing the evolution of the slowly varying envelopes of these modes. It is shown that this system supports backward- and forward-propagating vector solitons of the bright–bright and dark–dark type through a cross-phase modulation.

Based on the extended coupled nonlinear Schrodinger equations in an optical fiber with quintic nonlinearity (QN), the approximate analytical frequency chirps and the critical distances for the cross-phase modulation induced optical wave breaking (OWB) are discussed for the initial Gaussian optical pulses. Evolutions of the frequency chirps, shapes and spectra of pulses are numerically calculated in the normal dispersion regime. It is shown that, the approximate analytical frequency chirps accords well with the numerical ones at the initial evolution stages of the pulses. And the calculated approximate critical OWB distances accord well with the numerical ones only for the traditional OWB. In addition, for the positive QN and the negative one but with small absolute values, the traditional OWB can be observed. While for the negative QN with large absolute values, non-traditional OWB may occur. Namely, soliton pulse trains may develop during the pulse propagation.

We propose a general model to entirely describe XPM effects induced by 16QAM channels in hybrid QPSK/16QAM wavelength division multiplexed (WDM) systems. A power spectral density (PSD) formula is presented to predict the statistical properties of XPM effects at the end of dispersion management (DM) fiber links. We derive the analytical expression of phase error variance for optimizing block length of QPSK channel coherent receiver with decision-aided (DA) maximum-likelihood (ML) phase estimation (PE). With our theoretical analysis, the optimum block length can be employed to improve the performance of coherent receiver. Bit error rate (BER) performance in QPSK channel is evaluated and compared through both theoretical derivation and Monte Carlo simulation. The results show that by using the DA-ML with optimum block length, bit signal-to-noise ratio (SNR) improvement over DA-ML with fixed block length of 10, 20 and 40 at BER of 10 −3 is 0.18 dB, 0.46 dB and 0.65 dB, respectively, when in-line residual dispersion is 0 ps/nm.

We propose a cross-phase modulation (XPM) mitigation method in wavelength division multiplexing (WDM) systems, which is enabled by the split nonlinearity compensation (NLC) and the modified decision directed recursive least square (DD-RLS) based nonlinear phase noise (NLPN) tracking algorithm. In the proposed method, the split NLC reduces the interaction between the dispersion and the XPM and makes the impact of the XPM on the signal more tend to the NLPN. Combined with the proposed modified DD-RLS algorithm, which can effectively track the fast-changing NLPN, the XPM effect in WDM systems can be mitigated. The proposed method is demonstrated by a WDM transmission simulation with 11 channels. The simulation results show that the proposed modified DD-RLS algorithm has better NLPN tracking ability and noise tolerance than the normal DD-RLS algorithm, and together with the split NLC, 0.8 dB Q2-factor improvement can be seen in the 1000-km transmission.

A scheme is proposed for tunable all-optical format conversion from BPSK to OOK signal without active phase locking under the highly nonlinear loop structure. The 20 Gbit/s BPSK is mapped to two-level amplitude signal by delay interferometer (DI). One carrier branch generated locally remodulates the amplitude information to phase based on cross-phase modulation (XPM) effect in the highly nonlinear fiber (HNLF). The other carrier propagates as a pump under symmetrical loop ensuring the stability of phase relationship. After interference and vector shifting in coupler, the wavelength-tunable OOK is obtained. Benefiting from the signal remodulation mechanism and symmetric loop setup, separate carrier extraction and additional phase-locking are not required. The feasibility of the scheme is demonstrated by constellation diagram, eye diagram and pattern transformation diagram in numerical simulations. At the BER of 10 − 3 , the converted OOK has ∼ 0.7 dB and ∼ 1.9 dB optical signal-to-noise ratio (OSNR) improvement, respectively, compared to back-to-back (B2B) OOK under different quality of input signals. It is shown that the scheme optimizes the signal quality while converting signal formats. For low-quality BPSK with OSNR of 15 dB, the system indicates better noise tolerance. Furthermore, the scheme has potential scalability to bidirectional format conversion between BPSK and OOK.

We proposed a novel all-optical XOR logic accompanied with OOK/PSK format conversion by using cascaded semiconductor optical amplifier (SOA) configuration. Within each SOA, the cross phase modulation and nonlinear polarization rotation processes are properly controlled by OOK signals. The eye diagrams and obtained spectra witnessed the effectiveness of operation. A multicast function is also explored in the process of XOR function, and error-free operation (BER − 9 ) with less than 2.5 dB power penalty is obtained.

In this paper, we focus on the forming microwave induced phase grating (MIPG) in a crystal of molecular magnets. Firstly, we calculate the energy split of molecular magnet in the present of dc magnetic filed, and the results show that the frequencies dependence of the dc magnetic field are in the microwave frequency range. Secondly, the molecular magnet is subject two strong control magnetic fields (standing wave field and pump magnetic field). When a weak probe magnetic field with the frequency in the microwave range enters the crystal, the two control magnetic fields will modify the transmission and reflection properties of weak magnetic field. The system achieves high transmissivity and a big phase excursion for the weak probe magnetic field and form a microwave phase grating. Under proper parameters condition, the first-order diffraction efficiency of the microwave phase grating reaches 31 % , which is close to an ideal sinusoidal phase grating. And the diffraction efficiency of the grating can be adjusted efficiently by tuning the control field intensity, interaction length L and the single photon detuning. Thirdly, we also discuss the effect of Dopper effect on the microwave phase grating.

We propose a novel Mach–Zehnder interferometer (MZI) regenerator structure based on cross-phase modulation (XPM) effect between orthogonally polarized light. By adjusting the optical phase shifter on one arm of the MZI, the alignment of the optimal working points of the optical regenerator with the respective level powers of the degraded optical pulse-amplitude-modulated (PAM) signal can be achieved. The input-to-output power transfer function (PTF) capable of the regenerative Fourier transform, along with the optimal working points, is derived through theoretical analysis and the simulated PTFs are consistent with the theoretical results. Our research shows that the regenerative ability (RA) of the PAM regenerator increases with the input optical signal-to-noise ratio (OSNR), and the signal gain is inversely proportional to the level interval power of the input signal. The regeneration scheme proposed in the paper can theoretically be applied to the reshaping of an infinite number of regenerative levels, with a good consistency in the regeneration performance for each level. The phase preserving and bit-error rate (BER) properties of the regenerator are taken into account as well.

In this paper, we theoretically investigate all-optical logic gates based on wavelength conversion in a nonlinear directional coupler. The switching of a weak continuous-wave (cw) light is controlled by two pump lights, as a result, the information on the pump light transfers to the cw light by controlling different combinations of the two pump lights. Firstly we study the switching characteristic of the device and select in a way to provide the best average values of Xratio. Finally we realize logic operations C = A ⊕ B and D = A ⊕ B ¯ . The Xratio is higher than that of the ordinary methods and the all-optical logic gates based on wavelength conversion exhibit high switching contrast and have a better switching characteristic.

Pilot-tone (PT) aided phase noise compensation algorithm is very simple and effective, especially for flexible optical networks, because the phase noise coming from both Tx/Rx lasers and nonlinear cross phase modulation (XPM) during transmission can be adaptively compensated without high computational cost nonlinear operations, or the information of the neighboring channels and the optical link configuration. But to achieve the best performance the two key parameters, i.e. the pilot to signal power ratio and pilot bandpass filter bandwidth need to be optimized. In this paper it is demonstrated that constellation information can be used to adjust the two parameters adaptively to achieve the minimum BER in both homogenous and hybrid single carrier transmission systems with different LPN, XPM and amplified spontaneous emission (ASE) noise distortions.

In this paper, an all-optical switch based on asymmetric T-shaped single nanoslit coated with Kerr nonlinear dielectric has been proposed and simulated by the finite difference time domain (FDTD) numerical method. The switching performance of the device, is attained by self-phase modulation (SPM) and cross-phase modulation (XPM). The required power for nonlinear XPM effect is only 2% of that of SPM. The other distinguished features of this switch, is its extinction ratio of higher than 6 dB and very fast femtosecond response time. All these characteristics provide the contexts for the use of this structure in the photonic integrated circuit (PIC) as a bidirectional ON/OFF switch.

One of the main problems in liquid crystal spatial light modulators (LC-SLM) is the prediction of their optical modulation behavior for different wavelengths; this coupled phase/amplitude modulation can be hard to measure for specific wavelengths and setups, yet it is required to be included in the study of a number of SLM's applications. This work proposes a simulation model to predict the phase/amplitude modulation for different twisted nematic liquid crystal displays (TN-LCD) optical setups, this model incorporates the effects of wavelength in addition to other parameters which already have been studied before like twist angle as internal parameter and polarizers angles, we verified the accuracy of our model compared to results of previously published work.

The novel designs of all-optical logic gates using cross-gain modulation and cross phase modulation in semiconductor optical amplifiers, have been suggested and demonstrated successfully at 10 Gb/s. Mach–Zehnder configuration with two 3 dB couplers is used to introduce phase modulation on the saturated inverted output of SOA. No additional input beam such as clock signal or continuous light wave is used as in several other designs. In the designs, one data act as a pump and another act as a probe signal. Therefore, while passing through SOA, one data acting as a pump, saturates another data which is a probe signal. Different arrangements of input part of SOA–MZI, create three gates such as AND, XOR and OR. Gates are analyzed according to the extinction ratio, wavelength spectrum, frequency chirping and bit error rate. Very high extinction ratio is found i.e. 54.5, 36.32 and 37.5 at 1550.5 nm for AND, XOR and OR gates respectively. The wavelength spectrum, of all the three gates, lies within 1554.8 nm to 1555.2 nm which is near the central wavelength of probe pulse at 1550 nm. Negative frequency chirp are found for all the three gates with bit error rate 7.1×10 −30 , 1×10 −31 and 2.1×10 −12 for AND, XOR and OR respectively.

Based on the dispersive Drude model in negative index materials (NIMs), nonlinear coupled Schodinger equations are derived for two copropagating optical waves with cubic-quintic nonlinearity and modulation instabilities induced by cross-phase modulation (XMI) are studied by using standard linear stability analysis and the Drude electromagnetic model. It is shown that the quintic nonlinearity strengthens the XMI with broader XMI spectra and higher peak gain. It is found that the XMI gain is obviously larger in the region with anomalous group velocity dispersion (GVD) than that in the region with normal GVD. It is also shown that the serious XMI occurs when two optical waves propagate simultaneously in the positive refractive index region or in different refractive index regions. The work provides a theoretical basis for the extinction or utilization of XMI in the propagation of high power and high speed signals in NIMs.

A four level inverted Y-type quantum well semiconductor is proposed based on phase-sensitive Kerr nonlinearity with a closed-loop configuration. It is found that as the Rabi-frequency of coupling field increases, the maximal Kerr nonlinearity intensifies and at the same time the probe linear and nonlinear absorption decreases at Telecom wavelength λ = 1550 nm . The impact of an incoherent pumping field as well as the relative phase of the applied fields on nonlinear optical properties of the QW medium is then discussed. The temporal behavior of the Kerr nonlinearity and the required switching time for switching the nonlinear dispersion are also discussed. The results may be useful for understanding the switching feature of EIT-based slow light Kerr nonlinearity enhancement systems and have potential application in optical information processing and transmission.

In this paper the authors have demonstrated the feasibility and the realization of a wavelength tunable filter with an electro-optic modulation effect realized on diffused Ti:LiNbO3 waveguide. The two reflectors of the cavity consist in two Bragg׳s mirrors of identical period Λ = 1.81 μ m and whose total number N=140. Both mirrors have been engraved using the Focused Ion Beam technique up to the depths l 1 = l 2 = 2.7 μ m separated by a distance of l c = 500 μ m . We obtained thanks to electro-optic modulation effect a tunable shift whose value is 0.67 nm in a free spectral range FSR=1.59 nm for a voltage variation up to 60 V. This designed and realized probe will find many DWDM (Dense Wavelength Division Multiplexing) applications.

In this paper an adaptive multiple distortions compensation method based on amplitude modulated pilot tones (AM-PTs) is proposed for flexible single carrier optical coherent transmission systems. At the transmitter a pair of AM-PTs are generated from the optical carrier and inserted at the double sidebands of the optical signal. At the receiver the field of the AM-PT is recovered with the main signal and fully utilized for the estimation of both linear and ultra-fast nonlinear distortions including chromatic dispersion (CD), laser phase noise (LPN), local oscillator frequency offset (LFO) and cross phase modulation (XPM), thus avoiding the spectral efficiency and complexity cost due to the insertion of different pilots for the estimation of different distortions. The four distortions can be estimate from a simple analytical procedure or directly from the AM-PT fields. Thus the distortion estimation and XPM compensation process can be greatly simplified compared to the non-pilot-aided compensation algorithms. Furthermore the distortion estimation accuracy is not compromised and in inhomogeneous networks the XPM estimation accuracy is even better compared to the previous pilot-aided methods. Numerical simulations are then used to demonstrate the effectiveness and efficiency of this method.

With the development of the ultra-high speed and large capacity, the channel crosstalk cause by nonlinear effects become more apparent. This paper research the crosstalk produced by refractive index fluctuation nonlinear effects, establish the corresponding mathematical models and physical monitoring models. The experiment simulation results show when the input power is less than 50 mW, the channel crosstalk caused by the nonlinear effects is low and can be ignored; when input power greater than 50 mW, the channel crosstalk caused by the nonlinear effects is more high and affect transmission quality; and with the further increase in power, the channel crosstalk caused by SPM and XPM gradual increase, when the input power is greater than 300 mW, the crosstalk caused by SPM and XPM morn than by FWM.

The magnitude of the third order optical susceptibility exhibited by porous silicon monolayers was measured by a non-degenerated vectorial two-wave interaction. Optical irradiations at 488 nm and 532 nm wavelengths were employed to carry out the nonlinear optical experiments. Compared to bulk silicon material, a noticeable enhancement in the third order nonlinear optical response was identified. Photoluminescence and photoconductive properties were evaluated for the two studied wavelengths. The photoluminescent logic gate function AND was experimentally demonstrated using as a control a reflective optical Kerr gate configuration. A perceptible contribution for the third order optical nonlinearities seems to be related to the optical Kerr effect originated by excited states population. A two-level model was considered in order to describe the observed optical behavior.

A novel solid configuration is proposed to achieve a giant Kerr nonlinearity with reduced absorption under conditions of slow light levels. It is shown that an enhanced Kerr nonlinearity accompanied with negligible absorption can be obtained just through the proper tuning of intensity of coherent driving field at C-band telecommunication wavelength which is practical for communication applications. Moreover, the impact of incoherent pump field as well as frequency detuning of coherent field on manipulating the linear and nonlinear optical properties of the yttrium–aluminum-garnet (YAG) crystal medium is discussed. The presented results may be of interest to researchers in the field of all-optical signal processing and solid-state quantum information science.

In this paper we propose an operation of an all-optical logical gate based on an asymmetric nonlinear directional coupler operating with the cross-phase modulation. Two-input OR and XOR gates and a new logical operation based on an asymmetric nonlinear directional coupler, which can be applied to transmission and processing of signals in all-optical systems, are examined. Initially, we evaluate the effect of the pump power on switching. We import a pulse into the nonlinear directional coupler, meanwhile adding a pump light via wavelength division multiplex in order to take advantage of Kerr effect and produce the cross-phase modulation. In this situation, we analyze two possible situations for the two-input logical gate, and draw a switching characteristic curve via Matlab. Finally, we define the truth table and it is clear that OR and XOR logic gates and a new logical operation can be realized by changing the pump power. Next the investigation also indicates that to change the input pulse's phase switching can be realized. In the same way, we define the truth table and it can be observed that different logic gates are realized.

We investigate self and cross-Kerr nonlinearity in a four level quantized graphene atomic medium. The absorption, dispersion, transmission and subluminal/superluminal behaviors of a probe light field are studied. An amplification of the probe light field is observed in the absorption spectrum. The normal and anomalous slope of dispersion is also investigated at the positive/negative absorption region. It is shown that Kerr nonlinearity invert and enhance the subluminal/superluminal behaviors of the pulse and self-Kerr effect is found to be more subluminal/superluminal as compared to cross-Kerr effect. The results show significant applications in information storage, self and cross phase modulation and lasing without inversion.

We demonstrate dark-hollow beam (DHB) generation based on cross-phase modulation (XPM) in the hot Rb cell. It is found that a Gaussian beam (probe beam) can be converted into a DHB when the Rb cell is illuminated by a relatively intense counter-propagating Gaussian beam (pump beam). The size of the DHB can be adjusted by the pump power and sample temperature. In addition, a Bessel beam is obtained by focusing the DHB, which exhibits superior non-diffraction and self-healing abilities. The merits of tunable in size, simple setup, and low cost would make this method of significance in a variety of applications.

We have proposed a scheme for double-beam optical bistability in a tunnel-coupled asymmetric double quantum-well driven by two optical fields circulating inside two independently unidirectional ring cavities. In contrast to the single-cavity case where single-photon saturated absorption and self Kerr-nonlinearity are dominant, the two-photon absorption and cross phase modulation can be enhanced via tunneling induced interference and have an important influence to the formation of bistability. The bistable behavior can be controlled effectively via the system parameters such as the input and detuning of control field, the detuning of the probe field, Fano interference strength and cooperation parameter. Furthermore, the proposed scheme has the ability to manipulate the outputs of two optical cavities simultaneously. Due to the flexible design of semiconductor quantum well, our scheme is more practical than atomic system, therefore it can be utilized to achieve dual all-optical switching which has application in optical communication and computing.

The purpose of this work is to investigate the influence of the self-phase modulation and cross-phase modulation on the parametric interaction between pump signal and idler at few coherent lengths. The coherent length of four-photon mixing process can be quite long, up to 500 m to 1 km, if the spectral separation between the signal waves is relatively small. The problem with generation of new frequencies on distances less than one coherent length in parametric four-photon processes, without including the Raman scatter was solved only in approximation for a fixed electric field or fixed intensity of the pump wave. The overall task which includes the change in intensity and the phase of the pump wave has not been studied in detail in the literature up to now. The main purpose of the present work is to solve the more general problem: the mutual action of all χ(3) nonlinear processes on the parametric four-photon mixing.

In general, in excited-state absorption (ESA) based all-optical light modulator, maximum signal intensity modulation is achieved at the wavelength corresponding to maximum excited to ground state absorption cross-section ratio. However, theoretical analysis of photonic spectral modulation of broadband signal beam based on ESA in bacteriorhodopsin (BR) provides counterintuitive interesting results in the signal wavelength region 460–700 nm. It is shown that the signal modulation is enhanced significantly at some particular wavelength values (optimum signal wavelength). Optimum signal wavelength in the region 450–700 nm, varies with modulating intensity, and does not correspond to the peak absorption wavelength of the longer lived intermediate states. Present analysis is very useful in designing ESA based power efficient photonic devices.

The intensity-dependent four-wave mixing (FWM) efficiency is derived by the nonlinear Schrodinger equations including the self phase modulation and cross phase modulation between the two Fabry–Perot modes of a pump and a single-wavelength signal. The maximum FWM for mixing the pump with signal in non-zero dispersion shifted fiber is explained as the minimum phase mismatch for FWM due to equal group delay for the pump and signal. It was also found that the experimental measurements for the generated FWM power are limited by the stimulated Brillouin scattering (SBS) threshold. Under the SBS threshold, the experimental results are still coincided well with the theoretical calculations of the FWM generated power ratio to have the difference of 0.12 dB for the input signal power of 12 mW.

Tunable band-pass filter based on metal–insulator–metal (MIM) plasmonic circular ring resonators filled with Kerr nonlinear material is designed and numerically investigated by finite-difference time-domain (FDTD) simulations. Indium tin oxide (ITO) thin film with χ (3) =2×10 −10 esu is chosen to fill in the circular ring resonator. The designed filter has one stopband within the spectra range of 800 nm to 1100 nm and the bandwidth of a resonance is 32 nm. It is found that the transmitted-peak can be tuned by changing the intensity of incident light. Due to the Kerr nonlinear effect, the resonant wavelength of the cavity exhibits a red-shift with the increasing of the incident intensity. Narrow band filtering function at desired wavelength can be realized through tuning of peak resonance wavelength by changing the intensities of incident light. The designed plasmonic filter can find important potential applications in highly integrated optical circuits.

Midlink optical phase conjugation (M-OPC) based on four wave mixing (FWM) in semiconductor optical amplifier (SOA) can be used to compensate for the fiber nonlinearity effect in CO-OFDM systems. Simulation of 40 Gb/s CO-OFDM systems without optical dispersion compensation is presented. For a single-channel system, even greater benefits are obtained and the nonlinear limits are significantly decreased: the maximum Q can be increased by 3 dB for all transmission distances greater than 2400 km, the nonlinear threshold (NLT) (for Q > 10 dB) is increased by >4 dB. Due to cross phase modulation (XPM) from neighbouring WDM channels, the maximum Q and NLT are increased by about 1.1 dB and 1 dB for 50-GHz-spacing WDM systems separately. These results show that M-OPC can mitigate the fiber nonlinearity impairment for both single-channel and WDM systems.

We use a self-correlation technique to extract the inter-channel nonlinear effects i.e. cross phase modulation (XPM) induced phase noise and XPM-induced polarization scattering for analyzing the characteristics of XPM in coherent optical orthogonal frequency division multiplexing (CO-OFDM) wavelength-division-multiplexed (WDM) transmission systems under different dispersion compensation (DC) ratios and different walk-off values. Through the analysis, we can clearly see how the DC ratio acts on the XPM by applying this technique. After transmitting 1500 km standard single-mode fiber (SSMF), 12.3 dB phase noise is induced when the DC ratio is changed from 0% to 105%. While the walk-off is varied from 1.6 ps/km to 12.8 ps/km, almost 10.6 dB phase noise is eliminated. Additionally, the phase noise is verified as the dominant distortion in dual-polarization OFDM systems while the XPM-induced polarization crosstalk is proved to be the decisive distortion in dual-polarization QPSK coherent experiment.

Wavelength conversion employing semiconductor optical amplifiers (SOAs) is currently one of the most attractive and promising wavelength conversion techniques for future all-optical systems. This paper investigates the comparative performances of the three most popular SOA wavelength conversion techniques; cross-gain modulation (XGM), cross-phase modulation (XPM) and four-wave mixing (FWM). The FWM wavelength converter is analyzed for two types of source; a CW and a novel spectrum-sliced source. All performances are analyzed in terms of shifted wavelength conversion efficiency, Q-factors and converted signal powers. The converters are modeled and simulated using OptSim software. It was found that XGM yields the highest conversion efficiency of 17 dB, followed by XPM having 9 dB. The FWM wavelength converter had the lowest conversion efficiency, around −0.7 dB and −5.0 dB for CW and spectrum-sliced sources respectively.

In this paper 10 Gbps WDM systems at 16, 32 and 64 channels have been investigated with EDFA, RAMAN and SOA amplifiers individually and the performance has been compared on the basis of transmission distance and dispersion with and without nonlinearities. It is demonstrated that when the dispersion is 2 ps/nm/km and the number of channels are less, then SOA provides better results because as we increase the number of channels, the gain saturation problem arises due to cross gain modulation, the cross phase modulation and four wave mixing. When dispersion is increased from 2 to 10 ps/nm/km, EDFA provides better results than SOA in the term of BER and output power, but it shows non uniform gain spectrum. We also observed that RAMAN amplifier provides better results for L band amplification and gain flatting issue because it can substantially reduce the impact of fiber nonlinearity.

Cross-phase modulation (XPM) and self-phase modulation (SPM) induced nonlinear crosstalk has been studied analytically for coherent DPSK and OOK signal in NRZ- and RZ-modulation format for WDM system employing distributed Raman amplifier. The study shows that 40 Gb/s RZ-DPSK signal with 33.3% duty cycle experiences minimum XPM and SPM induced crosstalk. The results also reveal that minimum crosstalk was induced in backward pumped DRA among the three pumping schemes i.e. forward, backward and bi-directional. Results assume importance for minimizing deleterious XPM and SPM effects in optical communication system.

It is proposed and demonstrated a design of 2-to-1 photonic data selector based on the cross-phase modulation in a highly nonlinear fiber. By using bidirectional configuration, this scheme has potentially advantages of cost effective and simple structure. The correct output logic function is obtained at 40 Gbit/s without using any additional input light beams. In addition, the output signals have a single spectrum component by reasonable selecting input signals wavelength, which is important for transmission and scalability. The dependences of performances on signal wavelength, pump power, the temporal relative position of pulses, as well as the OSNR and chirp of input signals are calculated and discussed respectively, showing impressive operation performance. This scheme could be a promising candidate for future ultrafast all-optical signal processing applications.

In this paper 10 Gbps WDM systems at 16, 32 and 64 channels have been investigated with EDFA, RAMAN and SOA amplifiers individually and the performance has been compared on the basis of transmission distance and dispersion with and without nonlinearities. It is demonstrated that when the dispersion is 2 ps/nm/km and the number of channels are less, then SOA provide better results because as we increases the number of channels, the gain saturation problem arises due to cross gain modulation, the cross phase modulation and four wave mixing. When dispersion is increased from 2 to 10 ps/nm/km, EDFA provides better results than SOA in the term of BER and output power, but it shows non-uniform gain spectrum. We also observed that RAMAN amplifier provides better results for L band amplification and gain flatting issue because it can substantially reduce the impact of fiber nonlinearity.

In this paper, the XPM-induced crosstalk has been evaluated with higher order dispersion in SCM–WDM optical transmission link at different modulation frequencies, transmission lengths and optical powers. It has been observed that there is exponent increase in XPM-induced crosstalk with the increase in modulation frequencies, transmission lengths and optical powers, respectively. The impact of 3OD, 4OD and 5OD is small as compared to 2OD but still contributes when the combined terms are considered. The combined effect of second, third, fourth and fifth-order dispersion parameters, the induced crosstalk introduced by XPM little increase.