Mixing In Semiconductor Optical Amplifier Research Articles

DBSCAN-Based Clustering for Nonlinearity Induced Penalty Reduction in Wavelength Conversion Systems

We experimentally demonstrate, for the first time, the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm to improve the receiver performance of wavelength converting 40-Gb/s 16-quadrature amplitude modulation (16-QAM) and 30-Gb/s 64-QAM using four-wave mixing in semiconductor optical amplifier (SOA). Two novel modified DBSCAN methods are proposed, in which “un-clustered” received constellation points that are considered to be noisy points are further processed using method-(1) K-means and method-(2) the minimum distance between an unlabeled point and the clustered points. DBSCAN is more effective for distorted signals due to optical nonlinearities at higher than 25 and 30 dB of optical signal-to-noise ratios (OSNR) for 16- and 64-QAM, respectively. We find that DBSCAN can result in improvements in Q-factor by ~ 0.8 dB at optimum power when compared to linear equalization. The soft-clustering ability of DBSCAN method-(2) is particularly useful at high OSNR (30 dB) and high input signal powers in the SOA where excessive nonlinearity causes rotation of the outer-constellation points. Method-(1)’s hard clustering is valuable at lower input signal powers, where the clusters maintain a Gaussian-circular shape.

All-optical logic gate NAND using semiconductor optical amplifiers with simulation

Hybrid encoding technique for the representation of the binary states of information, four-wave mixing in semiconductor optical amplifier (SOA) as frequency generator and cross-polarization rotation effect in semiconductor optical amplifier as a frequency converter are used to design all-optical universal logic gate NAND. The devices can perform ultrafast operation and easily integrable. The simulated results of the proposed logic gate ensure feasibility of the proposals.

Polarization-insensitive phase conjugation using single pump Bragg-scattering four-wave mixing in semiconductor optical amplifiers.

We explain the generation of four wave mixing (FWM) components at the front and back facets of semiconductor optical amplifiers (SOAs) based on the Bragg-scattering from the propagating gratings in the SOAs. We propose a counter-propagating cross-polarized degenerate pumping scheme for the polarization-insensitive conjugate generation, simultaneously in both input and output ports of the SOA for the first time. The corresponding Bragg scattering processes along with the phase matching conditions are described and the detuning performance of the generated conjugate in either port are experimentally validated. Polarization-insensitive phase conjugate generation at both input and output ports of the SOA through Bragg scattering FWM is further demonstrated.

Quantum Dash Passively Mode-Locked Lasers for Coherent Wavelength Conversion System

We demonstrate an all-optical wavelength conversion system based on four-wave mixing in semiconductor optical amplifiers for quadrature phase shift keying (QPSK) and 16-quadrature amplitude modulation (16-QAM) signals using tunable dual-correlated pumps provided by the combination of a quantum dash passively mode-locked laser (QD-PMLL) and a programmable tunable optical filter. We investigate the effects of additional phase noise transfer to the wavelength converted idler due to non-ideal correlation between the comb lines of the QD-PMLL. Our studies of the wavelength conversion of QPSK and 16-QAM signals at 12.5 Gbaud using the proposed scheme find that the bit error rate performance was below the 7% forward error correction (FEC) limit over a range of pump spacing exceeding 300 GHz for QPSK signals, and conversion of 16-QAM signals was limited by the wavelength conversion scheme though was nonetheless below the 20% FEC limit.

Radio-over-fiber system with octuple frequency optical millimeter-wave signal generation using dual-parallel Mach–Zehnder modulator based on four-wave mixing in semiconductor optical amplifier

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 single-mode 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.

Microwave Photonic Harmonic Down-Conversion Based on Cascaded Four-Wave Mixing in a Semiconductor Optical Amplifier

A reconfigurable and wideband photonic method is proposed for microwave photonic harmonic down-conversion based on cascaded four-wave mixing in a semiconductor optical amplifier (SOA). The cascaded four-wave mixing in SOA triggers high-order harmonics generation of local oscillator (LO) in the optical domain, and enables microwave down-conversion in the electrical domain with a low-frequency electrical LO. Compared with the conventional photonic method, ours allows microwave down-conversion operation for wide frequency range RF signal with a low-frequency electrical LO, and at the same time it avoids the requirement of complex phase control and heavy driving for the electrical LO. Moreover, it enables reconfigurable down-conversion with frequency tunability. In the demonstration, the 3~40 GHz RF signals are experimentally down-converted to IF signals below 2 GHz with a low-frequency electrical LO within the range of 5 GHz.

Wavelength conversion for polarization multiplexing signal using four-wave mixing in semiconductor optical amplifier with reduced polarization crosstalk

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 pol-muxed 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.

Efficient and Accurate Modeling of Multiwavelength Propagation in SOAs: A Generalized Coupled-Mode Approach

We present a model for multi-wavelength mixing in semiconductor optical amplifiers (SOAs) based on coupled-mode equations. The proposed model applies to all kinds of SOA structures, takes into account the longitudinal dependence of carrier density caused by saturation, it accommodates an arbitrary functional dependencies of the material gain and carrier recombination rate on the local value of carrier density, and is computationally more efficient by orders of magnitude as compared with the standard full model based on space-time equations. We apply the coupled-mode equations model to a recently demonstrated phase-sensitive amplifier based on an integrated SOA and prove its results to be consistent with the experimental data. The accuracy of the proposed model is certified by means of a meticulous comparison with the results obtained by integrating the space-time equations.

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.

Phase‐encoded all‐optical reconfigurable integrated multilogic unit using phase information processing of four‐wave mixing in semiconductor optical amplifier

Non-linear properties of semiconductor optical amplifier are found very useful in optical switching and logic operation. Again, phase encoding system is established as an efficient method for implementing the ultrafast computing and communication with high spectral efficiency. Resulting phase of the intraband ultrafast four-wave mixing sidebands in semiconductor optical amplifier has been utilised in processing the phase information encoded over the input pump and probe waves and which generally followed the logic operation XOR or its complement XNOR. However, in this study, the authors first time propose a new scheme of implementing an all-optical integrated multilogic unit with phase-encoded data using only four-wave mixing in semiconductor optical amplifier, which can perform all the logic operations AND, OR, XOR and their complements after minor reconfiguration in the unit. This integrated scheme can exploit the parallelism of optics to achieve a superfast speed of operation.

Multi-Format Wavelength Conversion Using Quantum Dash Mode-Locked Laser Pumps

We investigate and compare the performance of wavelength conversion for two different non-return-to-zero (NRZ) modulation formats at 40 Gb/s: on off keying (OOK) and differential phase-shift keying (DPSK). To achieve wide wavelength coverage and integrability, we use a dual pump scheme exploiting four-wave mixing in semiconductor optical amplifiers. For phase stability, we use a quantum-dash mode-locked laser (QD-MLL) as a multi-wavelength source for the dual pumps, with tunability provided by the output filter. The significant sidelobes of the DPSK spectrum (relative to OOK) require the balancing of the pump proximity to the original signal (facilitating high conversion efficiency) with the signal degradation from the pump spectrum overlapping the converted DPSK signal. We achieve a conversion efficiency near –3.6 dB for OOK and –5.4 dB for DPSK across a 12 nm tuning range with low input powers (1 dBm). We measure bit error rate (BER) and obtain error free transmission (BER < 10−9) with a power penalty less than 2 dB for OOK and 3 dB for DPSK.

All-optical encryption/decryption for nonreturn-to-zero differential phase-shift keying signals using four-wave mixing in semiconductor optical amplifier

By experiment we demonstrate an all-optical encryption/decryption scheme for nonreturn-to-zero dif- ferential 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 nonde- generate four-wave mixing (FWM) in a semiconductor optical amplifier (SOA), which allows high data rate oper- ation 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.

All- optical phase encoded 4-to-1 phase multiplexer using four wave mixing in semiconductor optical amplifier

Optics has already showed its potency over its electronic complements in case of superfast computing and communication systems. Semiconductor optical amplifier, (SOA) with its several nonlinear properties, plays a very crucial role in the development of high-speed all-optical processor. Multiplexer and demultiplexer are the extremely important element of the processor which takes part in utilizing different actions like encoding, decoding, routing, and the different process of data conversion and generation, etc. In this paper, the authors have proposed a scheme of phase encoded all-optical phase multiplexer using four wave mixing (FWM) property of semiconductor optical amplifier. Thus, the improved tolerance against fiber-nonlinearity and higher receiver sensitivity of phase encoding method with the fast occurring processes like FWM in SOA offers higher speed in this proposed scheme of multiplexing.

QPSK wavelength multicasting based on four-wave mixing in semiconductor optical amplifier

We experimentally demonstrate one-to-five quadrature phase-shift keying (QPSK) wavelength multicasting based on four-wave mixing in bulk semiconductor optical amplifier. The input 25 Gb/s nonreturn-to-zero QPSK signal is successfully multicast to five new wavelengths with all information preserved. All the multicast channels are with a power penalty less than 1.1 dB at a bit error rate (BER) of 10-3. A characterization of the conversion efficiency in terms of pump and signal powers using the BER as figure of merit is also presented, the results indicate that the pump and signal powers should be optimized to eliminate the introduced deleterious nonlinear components.

Analysis of format conversion from optical 16QAM to QPSK based on cascaded four-wave mixing in semiconductor optical amplifier

A scheme of format conversion from optical 16-ary quadrature amplitude modulation (16QAM) to quadrature phase shift keying (QPSK) signal based on cascaded four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) is proposed. Theoretical analysis and simulations of the format conversion scheme are conducted to validate the feasibility of the proposal. In this proposal, the phase conjugated of 16QAM signal is generated after the first FWM process in an SOA, and then the QPSK signal is converted due to the second non-degenerate FWM (ND-FWM) process in another SOA. The performance and the optimal design of the 10Gbit/s format conversion system under various key parameters of SOAs are evaluated and discussed. Simulation results present useful to enable interconnection between backbone network and access network.

Analytical Model of Four-Wave Mixing in Semiconductor Optical Amplifier

The four-wave mixing process in pump-probe configuration requires the solutions of propagation equations of the three pulses: pump, probe and conjugate simultaneously. Since the pump power is much larger than the other pulses, this makes the differential equation of pump not coupled with the other equations, hence it can be solved alone. In this paper, we consider that the differential equation of pump is linear by assuming that the amplifier is divided into small sections to be the power change through each section is too small. Solving the resulting pump equation requires calculating the integrated gain, where the integrated gain is calculated after each section numerically by an iterative equation that was derived. Simultaneously, the solution of the probe and conjugate equations were also calculated after each section, where a simple recursive formula was found. Finally, the conversion efficiency will be calculated, where the present analysis agrees very well with the numerical solution.

Gigahertz to terahertz tunable all-optical single-side-band microwave generation via semiconductor optical amplifier gain engineering

We propose and demonstrate a technique to generate low-noise broadly tunable single-side-band microwaves using cascaded semiconductor optical amplifiers (SOAs) using no RF bias. The proposed technique uses no RF components and is based on polarization-state controlled gain-induced four-wave mixing in SOAs. Microwave generation from 40 to 875 GHz with a line-width ~22 KHz is experimentally demonstrated.

Novel anti-jamming technique for OCDMA network through FWM in SOA based wavelength converter

In this paper, we propose a novel anti-jamming technique for optical code division multiple access (OCDMA) network through four wave mixing (FWM) in semiconductor optical amplifier (SOA) based wavelength converter. OCDMA signal can be easily jammed with high power jamming signal. It is shown that wavelength conversion through four wave mixing in SOA has improved capability of jamming resistance. It is observed that jammer has no effect on OCDMA network even at high jamming powers by using the proposed technique.

All optical single module phase encoded half-adder and halfsubtractor exploiting four wave mixing in semiconductor optical amplifier

The development of all optical super fast arithmetic logic unit (ALU) is one of the most important requirement for construction of super fast all optical processor. All optical half-adder and half-subtractor have performed most of the essential functions of the arithmetic logic unit. Here in this paper the author has proposed a scheme of single module for phase encoded simultaneous operation of half-addition and half- subtraction for the same input bits using four wave mixing (FWM) in semiconductor optical amplifier (SOA). This type of single module for simultaneous operations using phase encoding based on the difference of phase with the reference signal one through FWM in SOA will gives fast response to accomplish the demand of super fast all optical processing. Keywords - ALU, FWM, SOA, half-adder and half-subtractor.

Bidirectional Radio Frequency Up-Converted Orthogonal Frequency-Division Multiple Access Passive Optical Network With Novel Source-Free Optical Network Units Using Four-Wave Mixing in Semiconductor Optical Amplifier

We propose and demonstrate a bidirectional radio-frequency (RF) up-converted orthogonal frequency-division multiple access passive optical network (OFDMA-PON) system. Novel source-free optical network units (ONUs) are configured in the proposed OFDMA-PON system, which can support simultaneous and interference-free upstream transmission from multiple ONUs over a single wavelength in a single-fiber topology. The four-wave mixing effect in a semiconductor optical amplifier is utilized in the optical line terminal to enable its configuration. Experimental results successfully verify the feasibility of our proposed system.