Mixing Wavelength Research Articles

A Selectable Multiband Bandpass Microwave Photonic Filter

A multiband bandpass microwave photonic filter (MPF) whose passband number and position can be selected is theoretically analyzed and experimentally demonstrated. The proposed MPF is based on a wide-band optical source (WBOS) and a two-order high-birefringence fiber loop mirror (HB-FLM), which serves as a slicing filter. Two segments of high-birefringence fiber (HBF) with the lengths of 3 m and 6 m are used in the HB-FLM, and three typical spectral periods or their combinations can be independently achieved by simply adjusting the polarization controllers (PCs) in the HB-FLM. Subsequently, the light source is sliced with uniform or mixing wavelength spacing. A coil of single-mode fiber (SMF) is then used to act as a dispersive medium to introduce time delay between taps. Thus, a single or multiband bandpass response is obtained at the output of a high-speed photodetector (PD). In addition, the passband centered at dc frequency is removed due to the use of phase modulation. All of the radio frequency (RF) characteristics of the proposed MPF show good agreement with the theoretical prediction. It has the merits of good flexibility, high spectrum efficiency, and great potential of extension.

Dynamic Control of Phase Matching in Four-Wave Mixing Wavelength Conversion of Amplitude- and Phase- Modulated Signals

We propose and experimentally demonstrate dynamic control of phase-matching in fiber-based four-wave mixing (FWM) for wavelength conversion of communication signals. By introducing self-compensation of optical gain/loss with stimulated Brillouin scattering (SBS) pump and Stokes waves, the FWM phase-matching condition and hence the conversion efficiency (CE) can be flexibly controlled. The phase difference between the interplaying fields is manipulated by modifying the refractive index through SBS without disturbing the initial parameters of the FWM process. The scheme is first applied to wavelength conversion of 10 Gbit/s non-return-to-zero (NRZ) on-off-keying (OOK) signal. Its performance on phase-transparent wavelength conversion is subsequently examined using 10 Gbit/s NRZ differential-phase-shift-keying (DPSK) signal. Eye diagrams, FWM spectra and bit-error rate (BER) performances for the converted signals without SBS, with gain-transparent SBS for maximum CE and for minimum CE are analyzed. In the OOK/DPSK wavelength conversion with gain-transparent SBS, the CE has been reduced by 10.7/11.4 dB at a signal-pump spectral spacing of 1.9/1.94 nm; while it has been enhanced by 8.8/7.4 dB at a signal-pump spectral spacing of 4.1/4.07 nm. The pronounced enhancement of the CE at large signal-pump spectral spacing results in enlargement of the 3-dB FWM conversion bandwidth. Limitations in the extent of bandwidth enlargement and noise performance are discussed. Potential use of the scheme in other applications is also described.

Generation of Multichannel Delayed Pulses by Four-Wave-Mixing-Assisted Stimulated Brillouin Scattering Slow-Light System

We demonstrate a technique to simultaneously generate multiple delayed signals through four-wave mixing (FWM) wavelength multicasting in a single-pump stimulated Brillouin scattering (SBS)-based slow-light system. The signal delay is achieved with an SBS pump while, at the same time, the delay is transferred to six other channels by three FWM pumps employed for wavelength multicasting. The delay performances of all output channels are analyzed. Relationship of the delay between the original signal and the multicast outputs is investigated and verified experimentally.

High‐Optical‐Quality Blends of Anionic Polymethine Salts and Polycarbonate with Enhanced Third‐Order Non‐linearities for Silicon‐Organic Hybrid Devices

A series of anionic polymethine dyes with different aromatic counterions are prepared to improve their compatibility as guests in an amorphous polycarbonate host. When they are used as the cladding material for silicon hybrid slot waveguides, four-wave mixing wavelength conversion and two-photon absorption-based optical-power modulation are observed. Such guest-host materials may be attractive candidates for all-optical signal-processing applications.

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.

Frequency conversion over two-thirds of an octave in silicon nanowaveguides

We demonstrate ultrabroad-bandwidth low-power frequency conversion of continuous-wave light in a dispersion engineered silicon nanowaveguide via four-wave mixing. Our process produces continuously tunable four-wave mixing wavelength conversion over two-thirds of an octave from 1241-nm to 2078-nm wavelength light with a pump wavelength in the telecommunications C-band.

Experimental study of slow light based on four-wave mixing wavelength conversion and dispersion in optical fibers

Slow light based on four-wave mixing (FWM) wavelength conversion and dispersion is experimentally studied. The FWM bandwidth of the highly nonlinear fiber is measured to be 40 nm, which is also the slow light tunable bandwidth. A 34 ns delay of 500 MHz sine signal is achieved in standard single mode fiber, and 198 ns delay of short pulses with 100 ps width is achieved in dispersion compensation fiber (DCF). An advancement of 209 ns for the 100 ps short pulses is also achieved in the DCF. The method to increase the slow light delay is discussed, and large delay up to microseconds is expected when wideband FWM wavelength conversion and large dispersion fibers are used. The expected large delay will help us realize high efficiency fiber delay lines and all-fiber buffers.

Four‐wave mixing wavelength conversion for a novel return‐to‐zero FSK signal at 43 Gb/s

AbstractTransparent wavelength conversion based on four‐wave mixing(FWM) in a SOA and in a HNDSF is experimentally demonstrated for a 43Gb/s return‐to‐zero frequency shift keying(FSK) signal. When a return‐to‐zero FSK signal propagates through the SOA or HNDSF, the wavelength will be converted and the waveform will be reshaped due to the FWM effect. Our experiments show that the performance of the converted signal is enhanced due to the reshaping characteristics, which indicates the potential of FWM as bit rate transparent wavelength conversion mechanism in future high‐speed systems. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2856–2858, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24800

Field-Trial Evaluation of Cross-Layer Effect Caused by All-Optical Wavelength Converters on IP Network Applications

Future Internet infrastructure will require the utilization of new all-optical devices able to enhance the use of fiber capacity. Nevertheless, before deploying such devices, it is necessary to test them under conditions similar to the ones of commercial networks and to evaluate their impact on real-world applications. In this work we investigate the performance of a tunable fiber four-wave mixing all-optical wavelength converter (AOWC) on a video-streaming carried through a field-trial network. This analysis is performed by measuring the packet-error rate (PER) degradation caused by the AOWC for different wavelength separations between the input and output optical carriers. To the best of our knowledge, this is the first time that such a cross-layer effect is systematically evaluated for an AOWC. A dynamic polarization controller was successfully used to prevent the FWM efficiency variations that were caused by the changes in the state-of-polarization of the video signal. Our results show that the AOWC introduced a maximum power penalty of 2.5 dB for wavelength separations of up to 12 nm. We also find that such a penalty is related to the optical signal-to-noise ratio degradation induced by the converter.

Pump-Suppressed Nondegenerate Four-Wave Mixing in a Highly Nonlinear Photonic Crystal Fiber Sagnac Loop

We propose a configuration for suppressing pumps in a broad-and flat-band tunable nondegenerate four-wave mixing (FWM) wavelength converter. The signal and pumps are coupled into a highly nonlinear photonic crystal fiber symmetrical Sagnac loop. After the FWM wavelength conversion in the loop, the idler is separated from the pumps without a filter. In our experiment, a flat wavelength conversion bandwidth of 36 nm, conversion efficiency of -11 dB, pump-to-signal suppression ratio of 48 dB, and idler-to-pump suppression ratio of 15 dB are achieved.

Field-trial evaluation of the Q-factor penalty introduced by fiber four-wave mixing wavelength converters

The performance of tunable all-optical wavelength converters based on four-wave mixing in optical fibers is experimentally tested in a field-trial network. Two converters were built with two different fibers. The first one was made with a small variation in the zero-dispersion wavelength (ZDW) dispersion shifted fiber and the second one with a highly nonlinear fiber that presents great ZDW variations. In order to compare the tuning ranges obtained in both cases we present an experimental spectral analysis. Numerical simulations that consider the influence of both the dispersion slope and the long-scale ZDW variations of the fiber complement the experiments. The tuning bandwidth was larger in the highly nonlinear fiber case. For a set of different optical signal-to-noise ratios, the measurements of the Q-factor of the signal and those of the converted wave are our main results. These results show that the penalty imposed by the converters is different for each converted wavelength. The maximum penalty obtained for the Q-factor was ∼6 dB, but it was ⩽3 dB for most cases. In all experiments we used a technique based on a dynamic polarization controller in order to avoid power fluctuations in the converted wave caused by polarization induced variations in the signal.

Tunable Optical Delay Using Four-Wave Mixing in a 35-cm Highly Nonlinear Bismuth-Oxide Fiber and Group Velocity Dispersion

In this paper, an optically controlled tunable delay scheme has been proposed using four-wave mixing (FWM) wavelength conversion in a 35-cm highly nonlinear bismuth-oxide fiber (Bi-NLF) together with group velocity dispersion (GVD) in a chirped fiber Bragg grating (CFBG). The Bi-NLF offers a very large nonlinearity and gives rise to significant FWM over a short fiber segment. With the use of a CFBG, a delay range over 185 ps has been experimentally demonstrated. To investigate the performance of the tunable delay, we have applied the scheme for variable delays of 10-Gb/s amplitude-shift keying (ASK) and differential phase-shift keying (DPSK) data signals. The bit error rate (BER) measurements show a power penalty of less than 3.5 dB for both amplitude- and phase-modulated data formats. To further increase the delay time, the CFBG has been replaced by a dispersion compensated fiber (DCF) that provides a wider bandwidth of operation. A variable delay up to 840 ps has been obtained using dual-pump FWM that offers a conversion bandwidth of about 40 nm. The large conversion range helps to minimize GVD-induced pulse distortion as a shorter DCF can be used for a given delay. The Bi-NLF provides an enhanced stimulated Brillouin scattering (SBS) threshold, a reduced latency, and an increased compactness of the approach for practical applications.

Improved Dynamic Characteristics on Four-Wave Mixing Wavelength Conversion in Light-Holding SOAs

We investigate theoretically and experimentally the dynamic characteristics of the wavelength conversion that is based on four-wave mixing (FWM) in a light-holding semiconductor optical amplifier (LHSOA). Two FWM conversion techniques, including the single-pump (SP) and two orthogonal-polarized pumps (OPP) schemes, are investigated using a sophisticated time-domain simulation model. The simulation indicates that the holding light gives an improved eye opening and signal-to-noise ratio for both the SP and OPP schemes. The chirp response for both schemes are also presented. The performance improvement are verified from dynamic measurements such as eye diagram and bit-error-rate (BER) tests. Clearer eye openings and reduced power penalties are obtained with the injection of a holding light. By comparing to the experimental results, we also prove that our numerical modeling can predict the device performance and can be used for optimizing the wavelength conversion process.

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.

The role of periodic interferometer errors in the calibration ofcapacitance displacement sensors for nanometrology applications

Although the role of the periodic errors of optical heterodyneinterferometers in displacement measurements is fairly well understood, theirinfluence on the calibration of other types of displacement sensor does notseem to be studied as extensively. We have performed a careful analysis of therole of these errors on the calibration of a capacitance displacement sensor,which is integrated into a linear piezoelectric transducer for nanometrologyapplications over displacement ranges in the sub-micrometre range.Assuming a linear dependence of the output voltage of the capacitancedisplacement sensor on the displacement it was found analytically thatperiodic interferometer errors lead to a decaying oscillation of the sensorsensitivity as the displacement range used in the calibration increases. Foruse of a double path interferometer with a polarization mixing amplitude of0.5 nm and a polarization mixing wavelength of 79 nm, deviations of sensorsensitivity of 0.3% for a range of 0.2 µm and 0.029% for a range of1 µm were estimated. The pronounced oscillations of the sensor'ssensitivity over very small displacement ranges as predicted by thetheoretical description were verified experimentally.

Widely tunable polarization-independent all-optical wavelength converter using a semiconductor optical amplifier

We report a polarization-independent widely tunable four-wave mixing wavelength converter using polarization diversity and broad-band orthogonal pumps in a single semiconductor optical amplifier. The conversion efficiency is nearly constant (less than 3-dB variation) over a 36-nm range with less than 0.34 dB polarization sensitivity. The power penalty at 10/sup -9/ bit error rate for a 10-Gb/s signal is less than 0.9 dB.

Filter-free four-wave mixing wavelength conversionin semiconductor optical amplifiers

Completely filter-free four-wave mixing wavelength conversion is demonstrated, for the first time, in a broad-area semiconductor optical amplifier. The use of a non-collinear four-wave mixing configuration provided 27 dB suppression of the straight-through converter beam relative to the output converted signal without using narrow-band optical filters. A 19.2 dB pump beam isolation was also obtained.

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/.

Nondegenerate four-wave mixing wavelength conversion in low-loss passive InGaAsP-InP quantum-well waveguides

Results on wavelength shifters based on four-wave mixing that operate in the 1.5-/spl mu/m regime are reported. These devices utilize the near-bandedge resonant enhancement in the third-order nonlinearity in passive InGaAsP-InP quantum-well waveguides. Over the erbium-doped fiber-amplifier gain band approximately -20 dB conversion efficiency was obtained with /spl ap/18-dBm CW pump power. The conversion efficiency was nearly constant for wavelength shifts up to /spl ap/26 nm (3.3 THz), limited by the phase-matching bandwidth of the 8.5-mm-long device.

FOUR-WAVE MIXING IN SEMICONDUCTOR TRAVELING-WAVE AMPLIFIERS FOR WAVELENGTH CONVERSION IN ALL-OPTICAL NETWORKS

Intraband modulation in semiconductor gain media has recently been shown to provide a wideband nonlinearity which is five orders of magnitude larger than the Kerr non-linearity in silica fiber. We discuss recent work on the application of this nonlinearity to the wavelength conversion function in all optical networks; specifically, carrier wavelength spectral translation by four-wave mixing. In addition to reviewing the current performance of these devices including conversion efficiency, signal-to-noise and a simple system demonstration, we will describe the underlying physics of the ultra-fast four-wave mixing mechanism and its application to TeraHertz spectroscopy of intraband scattering. An overview of wavelength conversion in the context of all-optical networks is provided and competing techniques to four-wave mixing wavelength conversion are also discussed.