Dual-pump Four-wave Mixing Research Articles

Degenerate squeezing in a dual-pumped integrated microresonator: Parasitic processes and their suppression

Using a general Hamiltonian treatment, we theoretically study the generation of degenerate quadrature squeezing in a dual-pumped integrated microring resonator coupled to a waveguide. Considering a dual-pump four-wave mixing configuration in an integrated $\text{Si}_3\text{N}_4$ platform, and following the coupled-mode theory approach, we investigate the effects of parasitic quantum nonlinear optical processes on the generation of squeezed light. Considering five resonance modes in this approach allows us to include the most important four-wave mixing processes involved in such a configuration. We theoretically explore the effects of the pump detunings on different nonlinear processes and show that the effects of some of the parasitic processes are effectively neutralized by symmetrically detuning the two pumps. This yields a significant enhancement in the output squeezing quality without physically changing the structure, but suffers from the trade-off of requiring substantially higher pump power for a fixed target level of squeezing.

Experimentally validated full-vectorial model of wavelength multicasting via four-wave mixing in straight waveguides

We derive full-vectorial nonlinear propagation equations of dual-pumped four-wave mixing in straight waveguides, which are valid in characterizing the one-to-six wavelength multicasting. Special attention is paid to the resulting idler wavelengths and their conversion efficiency, which enables the optimization of the experimental designs, including the incident wavelength and the power of pumps and signal. We validate the model by comparing the numerical simulation to the experimental measurement in a silicon-on-insulator waveguide, for the first time to our best knowledge, and achieve a good agreement. We further derive the general form of the proposed model for the case of using multiple,pumps, which holds a potential to numerically predict the performance of complex wavelength multicasting, and essentially guide the waveguide designs.

Compensation of nonlinearity in a fiber-optic transmission system using frequency-degenerate phase conjugation through counter-propagating dual pump FWM in a semiconductor optical amplifier

We present a scheme of frequency-degenerate mid-span spectral inversion (MSSI) for nonlinearity compensation in fiber-optic transmission systems. The spectral inversion is obtained by using counter-propagating dual pump four-wave mixing in a semiconductor optical amplifier (SOA). Frequency-degeneracy between signal and conjugate is achieved by keeping two pump frequencies symmetrical about the signal frequency. We simulate the performance of MSSI for nonlinearity compensation by scrutinizing the improvement of the Q-factor of a 200 Gbps QPSK signal transmitted over a standard single mode fiber, as a function of launch power for different span lengths and number of spans. We demonstrate a 7.5 dB improvement in the input power dynamic range and an almost 83% increase in the transmission length for optimum MSSI parameters of −2 dBm pump power and 400 mA SOA current.

10 GHz clock time-multiplexed degenerate optical parametric oscillators for a photonic Ising spin network.

A coherent Ising machine based on degenerate optical parametric oscillators (DOPOs) is drawing attention as a way to find a solution to the ground-state search problem of the Ising model. Here we report the generation of time-multiplexed DOPOs at a 10 GHz clock frequency. We successfully generated >50,000 DOPOs using dual-pump four-wave mixing in a highly nonlinear fiber that formed a 1 km cavity, and observed phase bifurcation of the DOPOs, which suggests that the DOPOs can be used as stable artificial spins. In addition, we demonstrated the generation of more than 1 million DOPOs by extending the cavity length to 21 km. We also confirmed that the binary numbers obtained from the DOPO phase-difference measurement passed the NIST random number test, which suggests that we can obtain unbiased artificial spins.

Mitigation of nonlinear effects through frequency shift free mid-span spectral inversion using counter-propagating dual pumped FWM in fiber

We propose and numerically verify a scheme of frequency-shift free mid-span spectral inversion (MSSI) for nonlinearity mitigation in an optical transmission system. Spectral inversion is accomplished by optical phase conjugation, realized by counter-propagating dual pumped four-wave mixing in a highly nonlinear fiber. We examine the performance of MSSI due to critical parameters such as nonlinear fiber length, pump and signal power. We demonstrate the near complete nonlinearity mitigation of 40 Gbps DQPSK modulated data transmitted over 1000 km standard single mode fiber using our method of MSSI. We perform simulation of bit-error rate as a function of optical signal to noise ratio to corroborate the effect of frequency-shift free MSSI.

Temporally uncorrelated photon-pair generation by dual-pump four-wave mixing

Temporally uncorrelated photon-pair generation by dual-pump four-wave mixing

Large-scale Ising spin network based on degenerate optical parametric oscillators

Simulating a network of Ising spins with physical systems is now emerging as a promising approach for solving mathematically intractable problems. Here we report a large-scale network of artificial spins based on degenerate optical parametric oscillators (DOPO), paving the way towards a photonic Ising machine capable of solving difficult combinatorial optimization problems. We generated >10,000 time-division-multiplexed DOPOs using dual-pump four-wave mixing (FWM) in a highly nonlinear fibre (HNLF) placed in a fibre cavity. Using those DOPOs, a one-dimensional (1D) Ising model was simulated by introducing nearest-neighbour optical coupling. We observed the formation of spin domains and found that the domain size diverged near the DOPO threshold, which suggests that the DOPO network can simulate the behavior of low-temperature Ising spins.

Experimental demonstration of optical phase conjugation using counter-propagating dual pumped four-wave mixing in semiconductor optical amplifier

We report optical phase conjugation in C-band by counter-propagating dual pumped non-degenerate four-wave mixing in a semiconductor optical amplifier (SOA). The co-propagating signal and pump waves create a grating inside SOA which diffracts counter-propagating pump and generates the conjugate wave. Since the signal and conjugate waves appear at opposite ends, the conjugate is easily filtered out from the rest of spectrum with minimal spectral shift of the conjugate with respect to the incoming signal. With pump powers of −3.2dBm each and signal input power of −7dBm, conjugate power was of −27.2dBm, giving a conversion efficiency of 1% at 18GHz pump-signal detuning. By modulating the signal by a periodic pattern ‘1000’ at 10Gbps using a non-zero chirp intensity modulator and resolving the temporal profile of the electric field envelope of the conjugate wave, we demonstrate spectral inversion.

Frequency-shift free optical phase conjugation using counter-propagating dual pump four-wave mixing in fiber

We propose and numerically verify a novel scheme of frequency-shift free optical phase conjugation by counter-propagating dual pump four-wave mixing in nonlinear fiber. The two counter-propagating pumps create a Bragg grating inside the fiber, which diffracts the forward propagating signal and generates a backward propagating idler wave whose phase is conjugate of signal phase. The two pump frequencies are placed symmetrically about signal frequency to ensure that idler wave will have same frequency as that of signal wave. Since the signal and idler waves appear at opposite ends, the idler is easily filtered out from the rest of the spectrum. Using nonlinear Schrödinger equation, we derive equations of signal and idler evolution. We obtain expressions for idler phase and show that perfect phase conjugation is achieved at an optimum length of fiber for a given pump power. We study the effect of fiber length and pump power on phase conjugation. Simulation results show the perfect phase conjugation at optimum fiber length under lossless conditions and small phase-offset when fiber loss and self and cross phase modulations are included. The small phase-offset is avoided by choosing fiber length smaller than optimum fiber length. Simulation results exhibit close agreement to theoretical values, which validates our simulations.

ALL OPTICAL FREQUENCY ENCODED COMBINATIONAL LOGIC DEVICES UTILIZING POLARIZATION INDEPENDENT FOUR-WAVE MIXING IN SEMICONDUCTOR OPTICAL AMPLIFIERS

Semiconductor optical amplifier (SOA) is among one of the most promising candidate for all optical computation and communication technology implementation. An all optical multiplexer and demultiplexer utilizing SOA-based dual pump four-wave mixing is proposed and explained. A multiplexer and demultiplexer are very important device for both optical computation and communication system and find variety of applications. In this communication, a multiplexer and a demultiplexer are proposed using frequency encoded format. Two very simple but interesting applications of demultiplexer one as decoder of two-bit frequency encoded numbers and another as comparator of frequency encoded single-bit numbers are presented for the first time in this communication. The devices proposed here can show ultra fast speed of operation and compact with advantages of using frequency-encoding technique for representing states of information.

Single SOA based ultrafast all-optical wavelength conversion for PolSK signal

A novel ultrafast tunable all-optical wavelength conversion for polarization-shift-keying (PolSK) signal based on dual-pump four-wave mixing (FWM), including parallel dual-pump FWM and orthogonal dual-pump FWM, in a single semiconductor optical amplifier (SOA) is proposed. A comprehensive broad-band dynamic model of the all-optical wavelength converter based on parallel dual-pump FWM and orthogonal dual-pump FWM in SOA is developed, for the first time to our knowledge. By numerical simulation, the proposed all-optical wavelength conversion is realized at 40 Gbit/s. The effects of the powers of input waves and wavelength detuning on the conversion efficiency of the wavelength converter are theoretically investigated in detail. The results indicate that, due to using the PolSK modulation format, this scheme is free of pattern effect. In addition, a wide tuning range can be obtained. The proposed all-optical wavelength conversion for PolSK signal is robust and potential for applications in future optical networks in terms of simple implementation and high speed operation.

All-optical format conversion from non-return-to-zero to return-to-zero based on dual-pump four-wave mixing in photonic crystal fiber

A novel all-optical format conversion scheme based on dual-pump four-wave-mixing (DP-FWM) in dispersion-flattened highly nonlinear photonic crystal fiber (DF-HNL-PCF) is proposed and experimentally demonstrated. The original non-return-to-zero (NRZ) format is converted into double return-to-zero (RZ) format by injecting NRZ signal and double synchronized clock signals into the DF-HNL-PCF. The DP-FWM effect generates two sideband components, which carry the same data information as the original NRZ signal with RZ format. The wavelength tunability and dynamic range of format converter are investigated. The optimum extinct ratio and Q factor of converted signals are 15 dB and 5.4, respectively. The advantages of this scheme are that the each wavelength of double channel multicasting signals is dependent and flexible. Moreover, the system is transparent to bit rate as well as modulation format, and achieves all-optical wavelength conversion and wavelength multicasting.

Wide-Range Wavelength Conversion of 40-Gb/s NRZ-DPSK Signals Using a 1.3-$\mu$m Quantum-Dot Semiconductor Optical Amplifier

Wide-range wavelength conversion using dual-pump four-wave mixing in a 1.3-μm quantum-dot semiconductor optical amplifier is reported. Nonreturn-to-zero differential phase-shift keying signals of 40 Gb/s were converted over a tunable wavelength range of 45 nm, maintaining the signal fidelity and allowing error-free operation.

Parametric Amplification and Wavelength Conversion of Single- and Dual-Polarization DQPSK Signals

We demonstrate system experiments for polarization-independent parametric amplification and wavelength conversion of single-channel differential quadrature phase-shift keying (DQPSK) signals up to 112 Gbit/s. Dual-pump four-wave mixing in a highly nonlinear fiber is utilized to achieve up to 20 dB ON-OFF gain and conversion efficiency. The investigations are done in a polarization-dependent (straight) as well as in a polarization-independent (loop) configuration using single- and dual-polarization DQPSK. Particular attention is paid to the resulting optical signal-to-noise ratio penalties after the amplification. We ascribe this to pump-induced nonlinear phase noise. It is shown that this type of excess noise is increased for the loop configuration in comparison with the straight configuration due to Rayleigh backscattering and that it depends on the input polarization of the signal. Still, the penalty can be made negligible using high-quality pump sources.

Theoretical investigation of orthogonal dual-pump four-wave mixing in semiconductor optical amplifier

A comprehensive broad-band model of orthogonal dual-pump four-wave mixing (FWM) in semiconductor optical amplifier (SOA) is presented in the case of the polarization state of the input signal being arbitrary. By performing numerical simulation and taking the all-optical wavelength conversion based on orthogonal dual-pump FWM in an SOA for example, the effects of the input light powers, frequency detuning and polarization state of the input signal on the orthogonal dual-pump FWM and the performances of wavelength conversion are theoretically investigated.

One-to-six WDM multicasting of DPSK signals based on dual-pump four-wave mixing in a silicon waveguide

We present WDM multicasting based on dual-pump four-wave mixing in a 3-mm long dispersion engineered silicon waveguide. One-to-six phase-preserving WDM multicasting of 10-Gb/s differential phase-shift-keying (DPSK) data is experimentally demonstrated with bit-error rate measurements. All the six multicast signals show error-free performance with power penalty less than 3.8 dB.

Polarization insensitive wavelength conversion based on dual-pump four-wave mixing for polarization multiplexing signal in SOA

We have theoretically investigated polarization insensitive all-optical wavelength conversion for polarization multiplexing signal based on dual-pump four-wave mixing (FWM) in a SOA. The simulation result shows that the polarization insensitive converted signal can be separated into two lightwaves without crosstalk when one of the two orthogonal data lightwaves is parallel with one pump and the SOA should be polarization insensitive. Several conditions which affect the conversion efficiency for polarization multiplexing signal are also discussed.

Evolution of first-order sidebands from multiple FWM processes in HiBi optical fibers

The generation of two idler waves inside a high birefringent (HiBi) optical fiber through three four-wave mixing (FWM) processes is studied theoretically. The coupled-equations for the field amplitudes are derived and analytically solved, in the co-polarized and orthogonal polarization schemes. The obtained solutions take into account the delayed Raman response of the medium. The polarization sensitivity of the generation of the idler waves is analyzed. Results show that the stimulated Raman scattering does not change the efficiency of the idler wave generation in the co-polarized scheme, whereas in the orthogonal polarization scheme that nonlinear process decreases the efficiency of the four-wave mixing processes. Results also show that this set of multiple four-wave mixing processes is physically quite different from the typical single or dual pump four-wave mixing configurations. Findings show that the power transfer from the pumps to the idler fields can lead to a monotonous growth, or a periodic evolution of the sidebands along the fiber. Results show that the process efficiency varies greatly with the angle between the two pump polarizations.

Widely Tunable Polarization-Insensitive Nondegenerate Four-Wave Mixing Wavelength Conversion for DPSK Signal

We demonstrate all-optical wavelength conversion for return-to-zero differential phase-shift keying (RZ-DPSK) signal by dual-pump four-wave mixing in a highly nonlinear photonic crystal fiber. By exploiting the residual birefringence in the fiber, the polarization of the first pump can be adjusted to achieve polarization-insensitive operation. The wavelength of the second pump is free to tune to broaden the conversion bandwidth. Open eyes of the converted signals are obtained for polarization-scrambled 10-Gb/s RZ-DPSK signal over a down-conversion bandwidth of 27 nm. Bit-error measurement shows a maximum power penalty of 4.5 dB at the error-free detection level.

Measurement of the Carrier Recovery Time in Semiconductor Optical Amplifier Based on Dual-Pump Four-Wave Mixing Technology

A scheme of measuring the carrier recovery time in semiconductor optical amplifiers (SOAs) based on dual pump Four-wave mixing technology is presented. The carrier recovery times under 120 mA, 180 mA 240 mA and 300 mA injected currents are measured to be 111 ps, 81 ps, 71 ps and 53 ps, respectively. The carrier recovery time of the spacing between the two pumps is also investigated. The experimental results show that the conversion efficiency keeps constant when the spacing of the two pumps varies within a small range.