Four-wave Mixing In SOA Research Articles

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.

Four-wave mixing for clock recovery of phase modulated optical OFDM superchannel

We simulate and experimentally demonstrate a novel all-optical clock recovery technique for a BPSK OFDM superchannel. Four-wave mixing in SOAs is used to strip the modulation from the superchannel sub-carriers, two of which are filtered and beat together in a photodiode to recover the clock.

Investigation of Transparency of FWM in SOA to Advanced Modulation Formats Involving Intensity, Phase, and Polarization Multiplexing

We experimentally investigate the real transparency of four-wave mixing (FWM) in semiconductor optical amplifiers to modulation formats involving intensity, phase, and polarization multiplexing. We exploit two different FWM polarization-independent schemes (that make use of two pumps) to wavelength-convert 40 Gb/s single-polarization and 80 Gb/s polarization-multiplexed signals in case of both nonreturn-to-zero <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</i> keying (NRZ-OOK) and NRZ differential phase-shift keying modulation formats. We found that, although FWM conversion is transparent to modulation formats employing phase and intensity, polarization-multiplexed signals pose serious limitations to all-optical processing transparency.

Waveband converters based on four-wave mixing in SOAs

Four wave mixing (FWM) is distinguished from other wavelength conversion techniques by its ability to simultaneously convert a number of input wavelength channels. In this case, optical signal-to-noise ratio (OSNR) is insufficient to describe the performance of the device as many effects are involved. A multiwavelength FWM model is used here to simulate a waveband converter (WBC). The numerical model predicts the waveform of the FWM product. Based on that output, the Q factor of the signal and the power penalty induced to the signal can be calculated to evaluate the performance of such a device. Meanwhile, an analytical model is used for the calculation of the signal power levels and the standard deviation of the fluctuation; hence, it describes the constituent effects-namely, the extinction ratio (ER) degradation, the OSNR degradation, the gain modulation (GM) related crosstalk, and interference. The model's validity is tested against the numerical results. To the best of the authors' knowledge, this is the first time that a numerical model and an analytical model are used to systematically investigate a WBC and to identify the specific effects and derive the design rules. These rules are tested in the experiment. Finally, a tunable WBC (TWBC) based on the dual-pump configuration is described and implemented experimentally

Automatically-Controlled C-Band Wavelength Conversion with Constant Output Power Based on Four-Wave Mixing in SOA's

We demonstrate the C-band wavelength conversion unit having functions of automatic wavelength recognition, power equalization, and elimination of original signal and pumping light for the first time, which is based on four-wave mixing (FWM) in semiconductor optical amplifiers (SOA's). The constructed unit automatically detects signal wavelength, sweeps wavelength of a pumping light, and adjusts center wavelengths of band pass filters arid gain values of erbium-doped fiber amplifiers (EDFA's), in order to convert the wavelength of the signal to the arbitrary wavelength we set, and eliminate the original signal and pumping light after conversion. Amplification of the signal, pumping, and wavelength-converted lights compensates the detuning dependence of conversion efficiency and its asymmetry in the quantum-well (QW) SOA, to keep the power of the wavelength-converted light constant within the whole C-band region. The switching time of wavelength conversion by the unit is about a second, which is dominated by mechanical movement of the tunable filters. Wavelength-converted 2.5 and 10Gb/s NRZ signals show clear eye-openings when the detuning is positive (ω p > ω s ), and a 2-ps pulse train is also successfully wavelength-converted. To overcome the problem of the asymmetric conversion efficiency in the QW-SOA, we adopted quantum-dot (QD) SOA's. Although the 1,5μm QD-SOA still shows its asymmetry, which will be improved by optimization of quantum dot structure, wavelength conversion of a 160Gb/s RZ signal is demonstrated by the QD-SOA's. More improvement of the performance of the wavelength conversion unit should be possible by making switching time faster and installing the optimized QD-SOA's.

Enhanced performance with optimized input power and increased dynamic range for wavelength conversion using four-wave mixing in SOAs

We investigate the converted optical signal-to-noise ratio, intersymbol interference, and bit-error-rate performance of all-optical wavelength converter based on four-wave mixing in semiconductor optical amplifiers as functions of the input pump and signal powers. The minimum power penalty less than 1 dB is achieved by optimizing the input signal and pump power. In addition, two approaches to expand the dynamic range of input signal power have been presented with the resulting dynamic ranges of more than 25 and 12 dB respectively and both show good tolerance to variations in input signal power.

Analysis of frequency chirping and extinction ratio of optical phase conjugate signals by four-wave mixing in SOA's

We present a complete large-signal dynamic model of a wavelength converter or optical phase conjugator based on four-wave mixing in semiconductor optical amplifiers. The modified transfer matrix method (TMM) is used for implementing the large-signal dynamic model. It is possible for this model to involve not only forward traveling waves, but also backward traveling waves. Also, this model includes longitudinal variation of carrier-induced reflective index, /spl alpha/-parameter, gain, carrier density, photon density, reflection, and amplified spontaneous emission noise at each small section. Therefore, we can accurately evaluate frequency chirping, optical pulse pattern, and extinction ratio of the conjugate signal. Th eye-opening penalty has been calculated to investigate the effects of frequency chirping and extinction ratio on transmission performance.

Tunability of polarization-insensitive wavelength converters based on four-wave mixing in semiconductor optical amplifiers

Optically transparent wavelength converters, in which the output is a wavelength-converted replica of the input, may be required to improve performance and ease management in future mixed-mode wavelength division multiplexed networks. Four-wave mixing (FWM) in semiconductor optical amplifiers (SOA's) is an attractive optically transparent wavelength conversion technique because it allows pump tunability. So far, three schemes for polarization-insensitive FWM in SOA's have been demonstrated, using two copolarized pumps, two orthogonal pumps, and polarization diversity. This paper presents a comparison of their output signal-to-noise ratio, and hence their ultimate tunability. A simple analytical model for FWM in SOA's is used to predict that when each scheme has the same inputs and produces the same frequency shift, the polarization-diversity scheme has the highest output signal-to-noise ratio of the three schemes, and hence promises the greatest tunability.