Highly nondegenerate four-wave mixing among subpicosecond opticalpulses in a semiconductor optical amplifier

We have demonstrated, for the first time, the highly nondegenerate four-wave mixing (FWM) among subpicosecond optical pulses in a 1.3-μm multiple-quantum-well (MQW) semiconductor optical amplifier (SOA). We could directly measure the FWM signal in the output spectrum by current pulse pumping of the device. We achieved a high conversion efficiency of over 10% at a frequency conversion range of less than 1 THz. The limitation of conversion efficiency due to the gain saturation of the SOA was effectively overcome by using the short optical pulses     

Folded-path self-pumped wavelength converter based on four-wave mixing in a semiconductor optical amplifier

A four-wave mixing wavelength converter with no external pump laser and very low input signal power requirements is characterized. The wavelength conversion occurs inside a high-reflection/antireflection coated semiconductor optical amplifier pigtailed with a fiber Bragg grating. The pump signal is provided by the lasing mode at the Bragg wavelength. A 1-mW optical signal modulated at 2.5 Gb/s is converted over 9 mm with error rates below 10/sup -9/.     

Ultrahigh-speed reconfigurable logic gates based on four-wave mixing in a semiconductor optical amplifier

We have demonstrated simple reconfigurable all-optical logic operations based on four-wave mixing in semiconductor optical amplifier and encoding information in the polarization of the input signals. Experimental implementation of six logic functions (including XOR, XNOR, AND, NOR, etc.) operating at 10 Gb/s were realized by simply adjusting two polarization controllers in the setup.     

Experimental investigation on slow light via four-wave mixing in semiconductor optical amplifier

Optical buffer is a key component in all optical information processing systems.Slow light at room temperature via four-wave mixing (FWM) in semiconductor optical amplifier (SOA) is experimentally investigated.Time delay of 0.40ns is achieved for a sinusoidal modulation signal at 0.1 GHz, corresponding to a delay bandwidth product (DBP) of 0.04.Factors that affect the experimental results are discussed.It is found out that the variable optical delay via FWM in SOA can be controlled either electrically by changing the SOA bias or optically by varying the pump power or pump-probe detuning.     

All-optical wavelength shifting of microwave subcarriers by using four-wave mixing in a semiconductor optical amplifier

We demonstrate all-optical wavelength shifting over 9 nm for two microwave subcarriers by using four-wave mixing in a semiconductor optical amplifier. In our experiment, the RF spectrum is relatively unaffected by wavelength shifting and the resultant system power penalty is /spl sim/0.5 dB. Such a transparent wavelength shifter may be a critical component in WDM networks supporting both subcarrier multiplexed (SCM) and high speed digital transmission.     

Cascaded wavelength conversion by four-wave mixing in a strained semiconductor optical amplifier at 10 Gb/s

We demonstrate for the first time cascaded wavelength conversion by four-wave mixing in a semiconductor optical amplifier. Bit-error-rate performance of <10/sup -9/ at 10 Gb/s is achieved for two conversions of up to 9 nm down and up in wavelength. For two wavelength conversions of 5 nm down and up, a power penalty of 1.3 dB is measured. A system of two wavelength converters spanning 40 km of single-mode fiber is also demonstrated.     

Polarization-insensitive wavelength conversion up to 10 Gb/s basedon four-wave mixing in a semiconductor optical amplifier

Polarization-insensitive wavelength conversion at 2.5 and 10 Gb/s using four-wave mixing in a bulk semiconductor optical amplifier is reported. At 10 Gb/s, a conversion range from 6.4-nm wavelength downshift to 4.8-nm upshift has been demonstrated. The conversion efficiency and signal-to-noise ratio versus conversion range are also characterized     

Effect of birefringence in a bulk semiconductor optical amplifieron four-wave mixing

We present experimental results on birefringence effects in an InGaAsP bulk semiconductor optical amplifier (SOA). Although the gain of the device is polarization insensitive, we observed a strong variation of the four-wave mixing (FWM) efficiency if the parallel input polarization of pump and signal wave was changed with respect to the device structure. This variation, which is attributed to birefringence in the SOA, can be as high as 10 dB for frequency detunings of about 6 THz. Thus, it might strongly affect the various applications of FWM for optical signal processing and parameter extraction. In addition, we performed polarization resolved measurements of the amplified spontaneous emission demonstrating different group velocity indices for TE and TM polarized light     

Contradirectional four-wave mixing in 1.51 mu m near-travelling-wave semiconductor laser amplifier

Experiments on contradirectional nondegenerate four-wave mixing (NDFWM) in a 1.51 mu m nonresonant near-travelling-wave semiconductor laser amplifier are presented. Experimental results are in qualitative agreement with a theoretical model assuming the NDFWM process is mainly due to carrier pulsation at the beat frequency of copropagating waves in the amplifier.<>     

Polarization-independent wavelength conversion at 2.5 Gb/s by dual-pump four-wave mixing in a strained semiconductor optical amplifier

We give a general expression for the polarization dependence of the four-wave mixing (FWM) efficiency in the dual-pump configuration. This expression, along with some general properties of the FWM susceptibility tensor, is used to propose a simple scheme to generate a nearly (1.5-dB variation) polarization independent FWM converted signal. The viability of this scheme is verified in a wavelength conversion experiment at 2.5 Gb/s.     

Polarization properties of four-wave mixing in strained semiconductor optical amplifiers

We present a theoretical and experimental study of the polarization properties of the four-wave mixing susceptibility of highly-strained multiquantum-well optical amplifiers and show how the intensity and polarization of the four-wave mixing signal depend on the polarization of the input waves. We demonstrate the validity of our model by generating a wavelength-converted signal having a polarization orthogonal to that of the pump wave at the output of the amplifier. In addition, we discuss the possibility of making the conversion efficiency independent of the input signal polarization by proper selection of the pump polarization.     

Analysis of basic four-wave mixing characteristics in asemiconductor optical amplifier by the finite-difference beampropagation method

We have numerically analyzed nondegenerate four-wave mixing (FWM) among short optical pulses in a semiconductor optical amplifier (SOA) by the finite-difference beam propagation method (FD-BPM). We used the nonlinear propagation equation taking into account gain spectrum dynamic gain saturation which depends on carrier depression, carrier heating, and spectral hole-burning, group velocity dispersion, self-phase modulation, and two-photon absorption. To analyze FWM in an SOA, the evolution in time and spectral domain of two input optical pulses with different frequencies during propagation was calculated. From this simulation, it has become clear that the method me used here is a very useful technique for simulating FWM characteristics in SOA's. We also found that the wavelength dependence of the gain is crucial if the detuning is larger than 1 THz     

Wavelength conversion up to 18 nm at 10 Gb/s by four-wave mixing in a semiconductor optical amplifier

We characterize the conversion bandwidth of a four-wave mixing semiconductor optical amplifier wavelength converter. Conversion of 10-Gb/s signals with bit-error-rate (BER) performance of <10/sup -9/ is demonstrated for wavelength down-shifts of up to 18 nm and upshifts of up to 10 nm.     

Bidirectional four-wave mixing in semiconductor optical amplifiers:theory and experiment

Bidirectional four wave mixing (FWM) is investigated in a bulk semiconductor optical amplifier (SOA) for dispersion compensation and for the clear/drop functionality in optical time division multiplexed (OTDM) systems. Good performance for bidirectional midspan spectral inversion (MSSI) is theoretically predicted for bit rates of 10, 20, and 40 Gb/s and is shown to be in agreement with measurements performed at 10 and 20 Gb/s. Measurements of the clear/drop functionality using the bidirectional technique show excellent performance for a 4×10 Gb/s signal and is again in good agreement with simulations. The clear/drop functionality is also simulated for 4×20 Gb/s and 4×40 Gb/s signals     

Widely tunable four-wave mixing in semiconductor optical amplifierswith constant conversion efficiency

The conversion efficiency and output signal-to-noise ratio (SNR) of single-pump four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) is strongly dependent on frequency shift. We examine a scheme for FWM in SOAs that uses two orthogonally polarized pumps. We compare experimentally and theoretically the conversion efficiency and SNR of the orthogonal-pump scheme with single-pump FWM. The orthogonal-pump scheme has nearly constant conversion efficiency and SNR over the 4.5-THz range of frequency shifts measured. Experimental and theoretical results for the conversion efficiency and SNR of the orthogonal-pump scheme agree to within 3.5 dB     

160-Gb/s optical sampling by gain-transparent four-wave mixing in asemiconductor optical amplifier

We report on a broad-band all-optical switch that exhibits high linearity (>30 dB), high switching contrast (>25 dB), and large data wavelength tunability (100 nm). The switching principle is based on four-wave mixing. Two control pulse trains are placed in the gain wavelength region of a 1300-nm semiconductor-optical amplifier. The data signal, however, is at 1550 nm in the transparent wavelength region where four-wave mixing sidebands are generated due to index modulations. The switch is used to sample a 160-Gb/s data signal with a temporal resolution of approximately 1.7 ps     

半导体光放大器啁啾特性分析

改进了分析行波半导体光放大器啁啾特性的理论模型,其中考虑了有限的端面反射率和自发辐射。理论研究表明,这些因素的引入将减小光放大器附加到放大光脉冲上的非线性频率啁啾。     

Theory of four-wave mixing wavelength conversion in quantum dot semiconductor optical amplifiers

Detailed theoretical analysis of four-wave mixing (FWM) wavelength conversion in quantum dot semiconductor optical amplifier (QD-SOA) is presented. The model takes into account the effect of the multidiscrete QD energy levels and the wetting layer. Good agreement between calculated and experimental data is obtained. Because of the discreteness of the energy levels, QD-SOAs demonstrate high FWM conversion efficiencies at high detuning frequency. Our calculations show that carrier escape from the ground state significantly affects the performance of the amplifier.     

Low-noise and very high-efficiency four-wave mixing in 1.5-mm-long semiconductor optical amplifiers

Very high four-wave mixing (FWM) efficiency and signal-to-background ratio (SBR) are obtained in a 1.5-mm-long bulk semiconductor optical amplifier. The FWM efficiency is measured to be 5 dB at 1-THz pump-signal detuning, which is the highest value reported to date. With a pump power of -1.4 dBm, the SBR is in excess of 20 dB in a bandwidth of 12.5 GHz, for a pump-signal detuning range as large as 2 THz and the efficiency is under the same conditions larger than -1 dB for a pump-signal detuning range as large as 1 THz. These results make FWM an attractive method for practical wavelength conversion. Some low-detuning measurements show a maximum efficiency around 8 GHz.     

A novel method for polarization insensitive four-wave mixing in semiconductor optical amplifiers

A new method for obtaining polarization insensitive four-wave mixing with phase inversion in a semiconductor optical amplifier is proposed. The method uses the simplest configuration with co-propagating pump and signal waves. The possibility of polarization insensitive four-wave mixing is shown for a tensile quantum well. Polarization insensitivity can be obtained by the right detuning of the pump wavelength from the gain peak.