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We propose a simulation scheme for cascaded four-wave mixing communication transmission characterization in the mid-infrared band. Simulations are performed using OptiSystem software. Signal light and pump light with wavelengths of 2052 and 2050 nm, respectively, passed through a highly nonlinear fiber, and significant cascade four-wave mixing phenomenon occurred, and the signal loaded on the signal light was successfully transmitted to the idler light generated by the cascade four-wave mixing effect. The performance of the signals carried in each idler light in both fiber and free-space channel was tested by eye diagrams and BER tests. At a pump power of 24 dBm, eight optical carriers were obtained the could meet the communication requirements, realizing a total transmission rate of 80 Gb/s. This is the first time that a simulation analysis of cascaded FWM multicast in the 2 μm band has been reported. The research results can promote the development of optical communication technology in the mid-infrared band and provide a reference for the establishment of high-speed multiplexing systems. [ABSTRACT FROM AUTHOR]

We represent the effect of nonlinear propagation in mode-division multiplexed multimode fiber (MMF) link. The effect of intermodal four-wave mixing (IMFWM) and intramodal FWM for waves with different spatial modes (LP01, LP02, LP11, and LP12) over MMF has been analyzed with the help of an optical spectrum analyzer using VPI Photonics/VPI transmission Maker℣ version 9.7 simulator. It can be concluded that high launch power and low dispersion generated sidebands in the cases of both intermodal and intramodal FWM. These FWM products grow in number with variation in wavelength of probe as well as these products grow toward the central pump frequency of that particular mode. It mathematically represents the multimode nonlinear propagation of different mode groups (containing N spatial modes in each group) in MMF due to Kerr effect. Thus, nonlinear interaction between modes results in interference that degrades the performance of multichannel mode-division multiplexed systems. To achieve full-phase matching and reduce the effect of IMFWM, chromatic dispersion has been increased in each spatial mode throughout the link. [ABSTRACT FROM AUTHOR]

A cost-efficient radio over fiber system based on a 21-tuple frequency binary phase-shift keying (BPSK) millimeter wave using a phase modulator (PM) and semiconductor optical amplifier (SOA) is theoretically proposed and demonstrated. In this scheme, the PM is driven by a radio frequency BPSK downlink signal at an appropriate modulation index to generate the +3rd-order sideband bearing BPSK signal and −4th-order sideband unmodulated generated signal, which is similar to the single sideband signal. New frequencies of sidebands are obtained after four-wave mixing in SOA. At the base station, after filtering, the −11th-order sideband bearing BPSK signal and +10th-order sideband unmodulated signal are abstracted, and then a photodiode is input to generate a 21-tuple frequency BPSK mm-wave signal, whereas the −4th-order sideband is used as the carrier for uplink. Simulation results show that, without precoding, a wideband 21-tuple frequency BPSK mm-wave signal with the frequency varying from 21 to 210 GHz can be obtained. Furthermore, the impact of SOA's current and the laser linewidth on the system performance is also studied. The power penalty for the downlink signal is 2 dB and for the uplink signal is 1.7 dB after 50 km single-mode fiber transmission at a BER of 10 − 9, which shows good system performance. [ABSTRACT FROM AUTHOR]

We propose an all-optical wavelength and format conversion model (CM) for a dynamic data center interconnect node and coherent passive optical network (PON) optical network unit (ONU) in software-defined networking and network function virtualization system based on four-wave mixing in a semiconductor optical amplifier. Five wavelength converted DQPSK signals and two format converted DPSK signals are generated; the performances of the generated signals for two strategies of setting CM in the data center interconnect node and coherent PON ONU, which are over 10 km fiber transmission, have been verified. All of the converted signals are with a power penalty less than 2.2 dB at FEC threshold of 3.8 × 10-3, and the optimum bias current of SOA is 300 mA. [ABSTRACT FROM AUTHOR]

We have proposed a scheme of radio-over-fiber (RoF) system employing a dual-parallel Mach-Zehnder modulator (DP-MZM) based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). In this scheme, the pump and the signal are generated by properly adjusting the direct current bias, modulation index of the DP-MZM, and the phase difference between the sub-MZMs. Because of the pump and the signal deriving from the same optical wave, the polarization states of the two lightwaves are copolarized. The single-pump FWM is polarization insensitive. After FWM and optical filtering, the optical millimeter-wave with octuple frequency is generated. About 40-GHz RoF system with a 2.5-Gbit/s signal is implemented by numerical simulation; the result shows that it has a good performance after the signal is transmitted over 40-km singlemode fiber. Then, the effects of the SOA's injection current and the carrier-to-sideband ratio on the system performance are discussed by simulation, and the optimum value for the system is obtained. [ABSTRACT FROM AUTHOR]

A scheme is proposed to realize the all-optical phase regeneration of four-channel quadrature phase shift keying (QPSK) signal based on phase-sensitive amplification. By utilizing conjugate pump and common pump in a highly nonlinear optical fiber, degenerate four-wave mixing process is observed, and QPSK signals are regenerated. The number of waves is reduced to decrease the cross talk caused by undesired nonlinear interaction during the coherent superposition process. In addition, to avoid the effect of overlapping frequency, frequency spans between pumps and signals are set to be nonintegral multiples. Optical signal-to-noise ratio improvement is validated by bit error rate measurements. Compared with single-channel regeneration, multichannel regeneration brings 0.4-dB OSNR penalty when the value of BER is 10-3, which shows the cross talk in regeneration process is negligible. [ABSTRACT FROM AUTHOR]

Midinfrared (MIR) wavelength conversion based on degenerate four-wave mixing is theoretically investigated in hydrogenated amorphous silicon (a-Si:H) waveguides. The broadband phase mismatch is achieved in the normal group-velocity dispersion regime. The conversion bandwidth is extended to 900 nm, and conversion efficiency of up to −14 dB with a pump power of 70 mW in a 2-mm long a-Si:H rib waveguides is obtained. This low-power on-chip wavelength converter will have potential for application in a wide range of MIR nonlinear optic devices. [ABSTRACT FROM AUTHOR]

We propose a flexible and reconfigurable wavelength-division multiplexing (WDM) multicast scheme supporting downstream emergency multicast communication for WDM optical access network (WDM-OAN) via a multicast module (MM) based on four-wave mixing (FWM) in a semiconductor optical amplifier. It serves as an emergency measure to dispose of the burst, large bandwidth, and real-time multicast service with fast service provisioning and high resource efficiency. It also plays the role of physical backup in cases of big data migration or network disaster caused by invalid lasers or modulator failures. It provides convenient and reliable multicast service and emergency protection for WDM-OAN without modifying WDM-OAN structure. The strategies of an MM setting at the optical line terminal and remote node are discussed to apply this scheme to passive optical networks and active optical networks, respectively. Utilizing the proposed scheme, we demonstrate a proof-of-concept experiment in which one-to-six/eight 10-Gbps nonreturn-to-zero-differential phase-shift keying WDM multicasts in both strategies are successfully transmitted over single-mode fiber of 20.2 km. One-to-many reconfigurable WDM multicasts dealing with higher data rate and other modulation formats of multicast service are possible through the proposed scheme. It can be applied to different WDM access technologies, e.g., time-wavelength- division multiplexing-OAN and coherent WDM-OAN, and upgraded smoothly. [ABSTRACT FROM AUTHOR]

A hybrid suboptimum channel separation (S-CS) scheme is presented. The distinct feature of the scheme is that it selectively minimizes the four-wave mixing (FWM) effect on the worst-affected channels and enhances the performance and spectral bandwidth efficiency in a controlled way. The scheme is helpful in the precise adjustment of tradeoff between immunity from FWM and spectral bandwidth requirement. The simulative comparison of the S-CS with optimum unequal channel separation (OUCS) and equal channel separation (ECS) schemes is performed to show its effectiveness. A dense wavelength division multiplexed system having a total capacity of 1.64 Tb/s in C band is implemented using the presented scheme. A maximum of 82 channels spaced at minimum CS of 50 GHz operating at a data rate of 20 Gb/s for each of the channels is realized using a S-CS (n = 12) hybrid scheme. The simulations are performed in the presence of all the linear and nonlinear impairments and noises. A maximum of 480- and 300-km distances using SSMF and ITUT.G655 fibers, respectively, is realized using dispersion-compensating fibers for 82 channels. The ECS and hybrid OUCS can be realized to cover the same distances but with 73 and 79 channels, respectively, due to the realization problem and bandwidth inefficiency. [ABSTRACT FROM AUTHOR]

Compared with optical network-on-chip (ONoC) with single wavelength, ONoC adopting wavelength division multiplexing (WDM) technology possesses a very prominent advantage—higher bandwidth. Therefore, WDM-based ONoC has been considered one of the most promising ways to relieve the rapidly increasing traffic load in communication systems. A WDM-based router, as the core equipment of WDM-based ONoC, is influenced by crosstalk noise, especially the nonlinear crosstalk noise generated by the four-wave mixing effect. Thus, to explore the performance of the N-port nonblocking optical router using WDM, we propose a universal analytic model to analyze the transmission loss, crosstalk noise, optical signal-to-noise ratio (OSNR), and bit error ratio (BER). The research results show that crosstalk noise varies along with signals at different wavelengths in the same channel. For signals with the same wavelength, the noises generated in the different transmission paths are obviously different from each other. For research of transmission loss, OSNR, and BER, similar results can be obtained. Based on the eye diagrams, we can learn that crosstalk noise will cause signal distortion to a certain extent. With this model, capability of this kind of multiport optical router using WDM can be understood conveniently. [ABSTRACT FROM AUTHOR]

This work investigates the advantages of nonlinear optics of a cascaded intensity modulator (IM) and phase modulator (PM) to generate an initial optical frequency comb. The results show that when the direct current bias to amplitude ratio, α = 0.1, and the IM and PM have the same modulation index and are equal 10, seed comb is achieved; it is generated by the modulation of two continuous wave lasers. Hence, based on these parameters, an intense four-wave mixing is created through 9 m of photonic crystal fiber. Moreover, a broadband spectrum was achieved, spaced by a 30-GHz microwave frequency. [ABSTRACT FROM AUTHOR]

A microwave photonic filter (MPF) based on four-wave mixing (FWM) is proposed and experimentally demonstrated. Two single-frequency laser beams produce the four-wave-mixing effect in a highly nonlinear fiber and generate a multiwavelength optical signal output. The multiwavelength optical signal is used to generate the multitaps of the MPF. The wavelength spacing of the multiwavelength optical source is equal to the frequency difference of the two input laser beams. By changing the frequency difference of the two input laser beams, wavelength spacing of the multiwavelength optical source output can be continuously tuned in the range of 0.36 to 1.6 nm. Thus the center frequency of the filter can be continuously tuned within the range of 6.914 to 30.729 GHz. [ABSTRACT FROM AUTHOR]

Semianalytic models are developed to deterministically calculate the variances of degenerate and nondegenerate four-wave mixing (FWM) noises for dispersion-managed dense wavelength division multiplexing (DWDM) systems with 8-Ary modulations [i.e., 8-level amplitude- and differential phase-shift keying (8APSK) and constant-amplitude optical differential 8-level phase-shift keying (D8PSK)]. The semianalytic models include various important propagation effects for exact numerical results. A 5.28-Tb/s (40-Gs/s/ch) 100-GHz-spaced 33-channel DWDM system with a dispersion map is then numerically analyzed by using the newly derived semianalytic models. It is numerically validated that FWM impacts coming from 8APSK pump channels are more severe than those coming from D8PSK ones, where pump channels denote the channels whose energies are transferred to a probe channel through the FWM process. The numerical results show that although FWM tolerance of a central channel with 8APSK is worse than that with D8PSK, a central channel with 8APSK is still superior to that with D8PSK when some linear noises and FWM noise are simultaneously taken into account for our given system conditions, which is mainly attributed to a relatively larger minimum Euclidean distance for the 8APSK constellation than the D8PSK one. [ABSTRACT FROM AUTHOR]

A multifunctional combinational logic module capable of performing several signal manipulation tasks all-optically, such as half-addition/subtraction, single-bit comparison, and 2-to-4 decoding simultaneously is proposed. Several logic functions (A + B, A:B, A:B, A:B, A ⊕ B, and A☉B) between two input signals A and B are implemented by harnessing a number of nonlinear effects, such as cross-phase modulation (XPM), cross-gain modulation (XGM), and four-wave mixing (FWM) inside only two highly nonlinear fibers (HNLF) arranged in a parallel structure. The NOR gate (A + B) is realized by the means of XPM effect in the first HNLF, whereas, A :B, A:B, and A:B logics have relied on utilization of XGM and FWM processes, respectively, in parametric medium made up of the second HNLF of parallel arrangement. The remaining A ⊕ B and A☉B logics required for successful implementation of the proposed simultaneous scheme are attained by temporally combining previously achieved ( A:B and A:B) and (A:B and A + B) logics. Quality-factor ≥7.4 and extinction ratio ≥12.30 dB have been achieved at repetition rates of 100 Gbps for all logic functions (A + B, A:B, A:B, A:B, A ⊕ B, and A☉B), suggesting successful simultaneous implementation. [ABSTRACT FROM AUTHOR]

We investigated wavelength conversion for polarization multiplexing signal based on four-wave mixing in a semiconductor optical amplifier. We found that the converted signals endured crosstalk among the polmuxed channels. We also proposed and demonstrated a wavelength conversion scheme with polarization diversity technique. By utilizing the technique, the converted polarization multiplexing signal can be received without crosstalk. In addition, the performance of the proposed system is numerically analyzed with respect to the bit error rate of the converted signal, different frequency spacing between signal and pump and modulated data rate. The simulation results show that the proposed scheme may be a promising method to realize transparent wavelength conversion for polarization multiplexing signals. [ABSTRACT FROM AUTHOR]

We propose to use a semiconductor optical amplifier as the nonlinear medium to realize data exchange of two differential quadrature phase-shift keying (DQPSK) signals based on the nondegenerate four-wave mixing (FWM) process. This scheme exploits the parametric depletion effect of the FWM process, when proper pump power and wavelength result in almost negligible noise of the original signal for the converted signal after data exchange. Optical data exchange of two DQPSK signals at 10 Gbps is achieved with a power penalty of less than 4 dB at the bit-error rate of 10-9. [ABSTRACT FROM AUTHOR]

Due to the merits of small size and low power consumption, microdisk lasers have been widely investigated as a potential light source for photonic integrated circuits. We investigate the dynamic and mode characteristics for a directional-emission microdisk laser subject to optical injection. At the free-running state, single-mode operation at 1540.16 nm with side-mode suppression ratio of 35 dB is realized for an 8-µm-radius microdisk laser connected with a 2-µm-width output waveguide at 7 mA. Under the injection locking state with the injection optical power of 2 mW, the 3-dB bandwidth of the small signal modulation response is enhanced from 3.4 to 13.7 GHz for the microdisk laser biased at 7 mA. Furthermore, the nonlinear states including four-wave mixing, period-one, and period-two oscillations are also observed and discussed for the microdisk laser subject to the optical injection with different wavelength detuning and optical power. [ABSTRACT FROM AUTHOR]

The transmission rates of the next generation intelligent optical networks are high, and the use of dense wavelength division multiplexing and a reconfigurable optical add-drop multiplexer makes the traditional optical signal-to-noise ratio (OSNR) monitoring techniques unsuitable. Hence, we investigated the OSNR monitoring method based on the nonlinear effect of four-wave mixing (FWM), which applies to the next generation intelligent optical networks. Due to FWM in a highly nonlinear fiber, a converted wave is generated and its power is dependent on the OSNR of the input signal. Two scenarios are studied, single-pump and orthogonal-polarized dual-pump. Under the condition of the given fiber length and the appropriate pump power, the monitoring ranges of OSNR could be extended to 23 and 30 dB for single-pump and orthogonal-polarized dual-pump, respectively. [ABSTRACT FROM AUTHOR]

By experiment we demonstrate an all-optical encryption/decryption scheme for nonreturn-to-zero differential phase-shift keying (NRZ-DPSK) signals at 10 Gbit/s using all-optical exclusive-OR (XOR) logic. The key bit stream is performed by a pseudorandom bit stream. The all-optical XOR logic is achieved by nondegenerate four-wave mixing (FWM) in a semiconductor optical amplifier (SOA), which allows high data rate operation and asymmetric optical powers of the two input bit streams. The gain dynamics and pattern effect associated with the SOA carrier lifetime are alleviated due to the constant envelope of the NRZ-DPSK signals. [ABSTRACT FROM AUTHOR]

This paper describes numerical and analytical analyses relating to the use of nonlinear four-wave mixing in a semiconductor optical amplifier medium for anticipated wavelength conversion at ultrahigh data rates of 320 and 640 Gb/s. The proposed system guidelines and design show that a maximum wavelength shift of 30 nm can be achieved at 640 Gb/s, while still maintaining an acceptable bit error rate. In addition, the impact of the pump-probe ratio and semiconductor optical amplifier bias current are investigated and the results are reported. [ABSTRACT FROM AUTHOR]

Making use of the four-wave mixing, a realization of all-optical 1 x 6 broadcast technology based on aluminum-doped highly nonlinear fiber (AL-HNLF) is performed. In the system, a set of experiments at channel intervals of 50, 100, and 200 GHz are conducted, and clear eye diagrams as well as low error performance are obtained with an input optical signal of a continuous wave and a 10-Gb/s return-to-zero on-off keying signal, which mostly benefits from the AL-HNLF used in this system. In detail, resulting from the high stimulated Brillouin scattering threshold of AL-HNLF, more power can be launched into the fiber. Additionally, similar performances of different channel spaces demonstrate the adjustability for this technology. With these distinguishing features, this technology might satisfy the basic expectation of utility. [ABSTRACT FROM AUTHOR]

We investigate a four-wave-mixing process in an interaction scheme in Rb vapor placed inside a low-finesse ring cavity. We observe strong amplification and generation of a probe signal, circulating in the cavity, in the presence of two strong optical pump fields. We study the variations in probe field gain and dispersion as functions of experimental parameters with an eye on the potential application of such a system for enhanced rotation measurements. Density-matrix calculations are performed to model the system and are shown to provide good qualitative agreement with the experiment. [ABSTRACT FROM AUTHOR]

This work describes efficient and polarization insensitive, all-incoherent four-wave mixing wavelength conversion achieved within a short length of highly nonlinear fiber medium, created by using both spectrally sliced pump and probe channels from a single-amplified spontaneous emission source coupled to two narrow-band Fiber Bragg grating (FBG) filters. This simple and cost-effective scheme is capable of generating a down-converted probe channel across a 17.2-nm wavelength span, while still maintaining a high conversion efficiency of around -22 dB and an optical-signal-to-noise ratio of ~21 dB. The effects of pump power, FBG detuning, and polarization are also reported. [ABSTRACT FROM AUTHOR]

We describe a semi-analytic model used to deterministically and exactly calculate the variance of degenerate and nondegenerate four-wave mixing (FWM) noises for 128 x 10 Gb/s return-to-zero frequency-shift-keying dispersion-managed dense-wavelength-division-multiplexing system. The analytic model includes various important light-propagating effects such as walk-off between channels, oscillation of pulse width with transmission distance, and stochastic variation of birefringence strength and orientation along fiber. The achievable maximum Q-factor and allowed maximum input powers for different dispersion management schemes and transmission distances are shown including overall FWM noises from different channel combinations, signal-amplified spontaneous emission (ASE) beat noise, and others. Achievable maximum transmission distances for such systems are studied. The upper limit of local dispersion of the dispersion map is discussed. In the case of allowed maximum input powers for the system, the variances of overall FWM noise are observed to be about half of those of signal-ASE beat noise when averaged for different transmission distances. It is found that for high-local dispersion, when transmission distance is long enough, effect of non-degenerate FWM noise, compared with degenerate FWM noise, can be ignored. [ABSTRACT FROM AUTHOR]

We configure the input pump pulse energy of semiconductor optical amplifiers (SOAs) to maximize the four-wave mixing (FWM) conversion efficiency. We simulate the propagation of optical waves in the SOA using the nonlinear propagation equation, taking into account the gain spectrum dynamics, gain saturation, which depends on carrier depletion, carrier heating, spectral hole-burning, group velocity dispersion, self-phase modulation, and two photon absorption. Our simulation results confirm that corresponding to each input probe pulse, there is an input pump pulse with optimum energy that maximizes the FWM conversion efficiency in the SOA. We introduce a pattern for tuning the input pump pulse energy of SOA, which leads to saving the energy in practical applications. We show that the FWM conversion efficiency will decrease when the input pump pulse energy increases from its optimum point. Moreover, for further input pump pulse energies, the width of the generated FWM pulse increases, and its energy will remain constant. [ABSTRACT FROM AUTHOR]

Raman effect brings the inevitable limitation of gain flatness in the fiber-optical parametric amplifier even if the phase-matched condition is well satisfied. Phase-matched gain is modulated by the real part of Raman susceptibility especially when it is on the anti-Stokes side. The real part mainly determines the gain profile and limits the flat-gain bandwidth to be less than 180 nm. An asymmetric modulated gain spectrum appears due to the assistance of the imaginary part on the Stokes side. Simulation results also show that the single- and dualpump configurations have different gain amplitude modulation factors induced by Raman. [ABSTRACT FROM AUTHOR]

We present a new method to generate broadband cascaded four-wave mixing (FWM) products in the silicon-on-insulator (SOI) waveguide. A simulation model of the nonlinear Schrödinger equation is used to describe the cascaded FWM in the SOI waveguide, which consists of launching two strong pump waves near the zero-dispersion wavelength of the very short (just a few millimeters) SOI waveguide. The numerical results based on the split step Fourier method have demonstrated that the output cascaded FWM products represent bandwidth of more than 1000 nm (range from C-band to IR-band). We also analyze the remarkable influences of parameters of the waveguide length, the pump power, and the dispersion slope on the cascaded FWM products in the SOI waveguide. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a long-reach wavelength division multiplexed-passive optical networks (WDM-PON) based on reflective semiconductor optical amplifiers (RSOAs) with easy maintenance of the optical source. Unlike previous studies the proposed WDM-PON uses two RSOAs: one for wavelength-selected light generation to provide a constant seed light to the second RSOA, the other for active external modulation. This method is free from intensity-fluctuated power penalties inherent to directly modulated single-RSOA sources, making long-reach transmission possible. Also, the wavelength of the modulated signal can easily be changed for the same RSOA by replacing the external feedback reflector, such as a fiber Bragg grating, or via thermal tuning. The seed light has a high-side-mode suppression ratio (SMSR) of 45 dB, and the bit error rate (BER) curve reveals that the upstream 1.25-Gb/s nonreturn-to-zero (NRZ) signal with a pseudo-random binary sequence (PRBS) of length of 215 - 1 has power penalties of 0.22 and 0.69 dB at BERs of 10-9 after 55-km and 110-km transmission due to fiber dispersion, respectively. [ABSTRACT FROM AUTHOR]

We investigate a transparent wavelength conversion based on four-wave-mixing (FWM) in semiconductor optical amplifier. We verify the effectiveness of the proposed scheme by analyzing the spectra and bit error rate. Then, we set up a 10-Gb / s single-user and 4 × 10 Gb / s multiuser transmission by Optisystem and discuss their performance. The simulation results show that the FWM effect between the two waves achieves a 2.4-nm wavelength conversion. At BER = 10 − 3 level, for single-user transmission the sensitivities of downstream (DS) and upstream (US) reach −23.6 and −23.4 dBm, and for multiuser transmission the sensitivities of DS and US reach −23.9 and −23.8 dBm, respectively. [ABSTRACT FROM AUTHOR]

All-optical non-inverted half-subtracter, half-adder, comparator, and decoder are pointed out based on a single semiconductor optical amplifier. We have replaced the continuous wave probe light with the clock pulse sequences light, which guarantees the non-inverted code output. All-optical AND, NOR, XNOR, XOR, A • B¯ , and A¯ • B logic gates are realized by four-wave mixing and cross-gain modulation of SOA, which are used to drive half-subtracter, half-adder, comparator, and decoder with 10 Gb / s return-to-zero code. Extinction ratio (ER) and optical signal-to-noise ratio (OSNR) are improved by a depolarizer. Compared with no depolarizer, for A = B output of comparator, it corresponds to XNOR; ER and OSNR are improved by about 1 dB. For d0 output of decoder, it corresponds to NOR; ER and OSNR are improved to 1.1 dB compared with the original value. However, for borrow of half-subtracter, greater than and less than of comparator, d1 and d2 of decoder, it corresponds to A • B¯ and A¯ • B; ER and OSNR show only slight deterioration about 0.4 dB. For carry of half-adder and d3 of the decoder, it corresponds to AND; OSNR has hardly changed and ER has improved by about 2 dB. It has potential applications in more complex optical computing and optical signal processing systems. [ABSTRACT FROM AUTHOR]

We present a numerical analysis of the average intercore crosstalk (IC-XT) of wavelength-division multiplexed (WDM) optical channels in a homogeneous two-core fiber system. This analysis is performed considering cores with zero-dispersion wavelengths at 1550 nm. In the analysis, we consider 11 WDM channels spaced 100 GHz apart transmitted in three different schemes, one centered at 1510 nm with negative dispersion D = − 3.5 ps / nm · km, one centered at 1550 nm with D = 0, and one centered at 1590 nm with D = + 3.5 ps / nm · km. This selection allows for the observation of how the IC-XT of WDM channels is modified using positive, zero, and negative dispersion parameters. To analyze more realistic scenarios of IC-XT in multicore fibers, we considered random bending and twisting perturbations along the fiber. In addition, we considered fiber nonlinearities such as four-wave mixing (FWM) among WDM channels. The results show that FWM produces a power transfer among the transmitted WDM channels that depends on the dispersion parameter D at core 1, and this effect is transferred to the average crosstalk of the WDM channels at core 2. Therefore, the average IC-XT of WDM channels can be modified in a controlled way by selecting an adequate dispersion parameter D in combination with FWM nonlinearity. These results provide valuable information for understanding the wavelength dependence of the average IC-XT of homogeneous multichannel MCF systems working around a zero-dispersion wavelength. [ABSTRACT FROM AUTHOR]

We report an approach for generating an evenly spaced, flat, and spectrally broad optical frequency comb (OFC) by the exploitation of gain modulation experienced by a fourth-ordered periodic Gaussian pulse train. The spectrally flat OFC generator is realized by propagating the periodic optical pulse through high gain SOA. The spectrum flatness limits up to 10 dB for 102 frequency lines, which is improved by exploiting four-wave mixing in 1-m long highly nonlinear fiber. We report a 30-GHz frequency line spaced, 3.06-THz spectrally broad OFC with 2.6-dB maximum power deviation. [ABSTRACT FROM AUTHOR]

A simple method has been proposed to use four-wave mixing to design and simulate the all-optical AND logic gate in a photonic crystal semiconductor optical amplifier (PC-SOA) that is integrated with an ideal optical bandpass filter. The preferred logical function could be carried out in the proposed scheme with no use of a continuous-wave signal. Nonlinearities including carrier depletion, carrier heating, and spectral hole burning have been considered in the presented simulations. Furthermore, for improvement of the AND logic gate performance, the impacts of the pattern effect of the signals propagating in the PC-SOA medium, the input signal bit rate effects, and gain recovery have been extensively investigated. The findings demonstrated that the optimal output signal featuring 3-fJ energy and 2-mA injection current could be achieved at a bit rate of 50 Gbps. [ABSTRACT FROM AUTHOR]

We investigate fiber optical parametric amplification (FOPA) in a structure of an As2S3 core and TeO2 cladding photonic crystal fiber (PCF). Various amplification features such as wavelength area, parametric gain value, and bandwidth are investigated. In order to design the FOPA system with optimal features, effects of different structural parameters variation on optical features of the PCF and parametric gain subsequently are also investigated numerically based on the finite-difference time domain numerical method. Using 15 cm of this fiber and a continuous wave pump laser of 1.1 W, we attain a gain spectrum of 350 nm with a maximum value of 37 dB around 1550 and 1310 nm, which are favored wavelengths in optical telecommunication systems. In fact, our structure ends in a wideband amplifier in an absolutely compact size, which is optimized exactly for optical telecommunication applications. [ABSTRACT FROM AUTHOR]

We report the transmission of signal light and the noise accumulation in the fiber Raman amplifier (FRA) under four-wavelength time-division multiplexing (TDM) pumping. A quality factor that is used to describe the performance of the Raman fiber amplifier system in quantitative analysis is proposed. The results indicate that the power variation of signal light has a certain periodicity that is related to the period of pumping with the TDM pumping. The shorter the pumping period is, the weaker the signal fluctuation is. Through the analysis of noise, it is found that amplified spontaneous emission is the main source of the noise of FRA with TDM-pumping. By comparing the TDM pump scheme with the continuous multiwavelength pump scheme, it is found that the gain of the TDM pump scheme is higher than that of the continuous multiwavelength pump scheme. [ABSTRACT FROM AUTHOR]

A broadband fiber-optic parametric amplifier (FOPA) based on near-zero dispersion profile with single zero dispersion wavelength (ZDW) by selective liquid infiltration technique is numerically investigated. Here, the gain and bandwidth for an FOPA incorporating "dual pumping" scheme are thoroughly investigated by varying the fiber length, operating wavelength (central wavelength), and pump power. The structure is engineered in such a way that the dispersion profile is having near-zero dispersion value (negative β2) for a wide wavelength range and small positive β4 around the pump wavelength; thereby, the phase mismatch term remains within the favorable value for a wide wavelength leading to wider FOPA sources. The structure also supports reasonable high nonlinearity and low propagation loss. Our numerical investigation results in an FOPA with optimized bandwidth of around 180 nm close to communication wavelength. Finally, a detailed comparative study of the single pump scheme and dual pump scheme for FOPA/amplifier gain and spectrum bandwidth has been performed for identical fiber parameters. It has been observed that dual pump scheme provides smoother/flatter spectrum (lesser gain fluctuation) around the center of the optimized profile with slightly lesser bandwidth compared to single pump operation. Additionally, it was observed that the dual pump FOPA supports higher pump power thereby enabling higher FOPA unaltered peak gain (3 dB) throughout the bandwidth (the peak and dip of the gain spectrum difference remaining within 3 dB) than that of single pump scheme. [ABSTRACT FROM AUTHOR]

We demonstrate a method for all-optical multi-wavelength regeneration based on four-wave mixing. Three wavelength division multiplexed signals, each having a data rate of 10 Gbps and a fixed wavelength spacing of 1 nm, are modulated with a sinusoidal signal of 25 GHz. The resultant sidebands of the modulated signal are filtered at a variable wavelength spacing and combined with a pump signal. The combined signal is passed through a highly non-linear fiber to generate multiple carriers at different wavelengths through four-wave mixing. Filtering the data modulated carriers obtained at the output of the highly non-linear fiber results in signals having lesser noise contribution. Two different optical signal-to-noise ratios (OSNRs) of 16.5 and 19 dB at the input of the regenerator are considered to evaluate the system performance. In both cases, a significant improvement in the bit error rate (BER) of the signals is observed. Simulation results show an average improvement of 2.537 and 1.335 dB in received optical power at BER of 10 − 9 in case of 16.5 and 19 dB OSNRs, respectively. [ABSTRACT FROM AUTHOR]

A scheme for detecting the phase of an incoming optical signal is systematically optimized and demonstrated experimentally. It makes use of four-wave mixing in a highly nonlinear fiber but differs from a phase-sensitive amplifier by its focus on phase detection, rather than on phase-dependent noise reduction. This experimental setup combines the signal with its phase-conjugated idler at the same frequency, before sending the combination to a photodetector. Experimental results show that the ratio of maximum and minimum currents can exceed 1000 even at a relatively low pump power of 10 mW. The proposed scheme may be useful for detecting the signal phase in coherent communication systems without the need of heterodyne detection. [ABSTRACT FROM AUTHOR]

With the application of wavelength division multiplexing, four-wave mixing (FWM) has an obvious influence on transmission systems. The effects of different channel intervals and numbers of channels on FWM performance in next generation Ethernet passive optical networks are discussed experimentally. When the incident signals near the zero-dispersion wavelength with a 200-GHz channel interval are transmitted over a 25-km fiber, new frequencies are generated, and more than 5-dB sensitivity loss is obtained. With the increase of channel spacing, the performance of FWM decreases significantly. The FWM crosstalk can even be ignored when the channel spacing is set at 800 GHz. In addition, the performance of FWM significantly increases when the number of channels is changed from 3 to 4, at which the power depletion is more severe. [ABSTRACT FROM AUTHOR]