Fiber Four-wave Mixing Research Articles

Reduction of fiber four-wave mixing generated from modulated lights by inserting dispersive elements

Reduction of fiber four-wave mixing generated from modulated lights by inserting dispersive elements

A Refractive Index Sensor Based on Four-Wave Mixing in D-Shaped Tellurite Photonic Crystal Fiber

In this study, we design a refractive index (RI) sensor using a novel cadmium telluride photonic crystal fiber (TPCF). Based on four-wave mixing (FWM), the changes in RI can be accurately detected, and RI sensing in the mid-infrared region (MIR) can be achieved by detecting wavelength shifts in the Stokes and anti-Stokes spectra caused by the changes in RI of the liquid to be measured. When the pump wavelength of FWM lies in the normal and abnormal dispersion regions of the TPCF, the RI response of the idler frequency wave and the signal wave are analyzed by numerical simulation methods. The simulation results show that the RI sensitivity of the sensor can be as high as 7692 nm/RIU with a linearity is up to 99.9% at the pump wavelength of 3380 nm. To our knowledge, the RI sensing sensitivity of the MIR is presented for the first time in this study by using FWM in the non-silicon PCF.

Improving the Resistance of AO-OFDM Signal to Fiber Four-Wave Mixing Effect Based on Insertion Guard Interval

In this paper, a method to suppress the impact of the nonlinear effects on an all optical orthogonal frequency division multiplexing (AO-OFDM) system is proposed. By inserting a guard interval (GI), the duty cycle of the optical signal in each symbol period of each subcarrier is decreased, thus generating a ‘zeroed’ temporal. By giving different time delays to the sub-carriers, these ‘zeroed’ temporals and optical signals of the adjacent sub-carriers are interleaved, which reduces the coincidence of the optical signals between the sub-carriers and eliminates the products of the four-wave mixing (FWM) effect to suppress the influence of the nonlinear effect on the system. The simulation results show that for an AO-OFDM system with 32 subcarriers, inserting GI and introducing different delays for each subcarrier can improve the transmission distance by 30 km or enhance the spectral efficiency by 16.7%, considering the 7% hard decision forward error correction (HD-FEC) threshold. Moreover, even when the number of subcarriers is up to 256 and the power of each subcarrier is as high as 0 dBm, our proposed signal optimization scheme can still guarantee that the BER can satisfy the 7% HD-FEC threshold.

Mid-infrared difference-frequency generation directly pumped by a fiber four-wave mixing source.

We demonstrate a new, to the best of our knowledge, method of generating mid-infrared pulses by difference frequency mixing the Stokes pulse generated by four-wave mixing in a photonic crystal fiber with the remaining pump pulse. The Stokes pulses generated by four-wave mixing are inherently overlapped temporally and spatially with the pump pulse at the output of the fiber. Focusing this output into a nonlinear crystal phase matched for difference frequency generation between the pump and Stokes pulses results in a simple method of generating mid-infrared pulses. With a pump source at 1.064 µm, and a photonic crystal fiber engineered to generate Stokes pulses at approximately 1.65 µm, we generate 160 mW of mid-infrared light at approximately 3 µm through difference frequency generation.

Effects of Self-Phase and Cross-Phase Modulations at Four-Wave Mixing in Optical Fibers

Effects of Self-Phase and Cross-Phase Modulations at Four-Wave Mixing in Optical Fibers

Mid-Infrared Stimulated Raman Scattering and Four-Wave Mixing in a Tellurite Microstructed Optical Fiber

In this work, a tellurite microstructed optical fiber (TMOF) was designed and fabricated by 78TeO₂-5ZnO-12LiCO₃-5Bi₂O₃ (TZLB) glass, which provided an opportunity for investigating the stimulated Raman scattering (SRS) and four wave mixing (FWM). Using a nanosecond laser operated at 1545 nm as a pump signal, mid-infrared cascaded SRS was observed. At 60 mW, the continuous-wave (CW) signal gain was as high as 10.46 dB. During the FWM process, with the CW signal wavelengths changing from 1547 nm to 1560 nm, a maximum conversion efficiency (CE) of −27.05 dB was obtained. The SRS and FWM in the TMOF were numerically simulated, and the obtained results agreed well with the experiment. To the best of our knowledge, it was the first time to demonstrate simultaneously SRS and FWM in a TMOF. The proposed TMOF of extremely high nonlinearity can be exploited for the development of multifunctional multiplexing devices of Raman amplifiers and wavelength converters, and is expected to meet the increasing requirements of high-performance all-optical devices.

Palliation of Four-Wave Mixing in Optical Fibers Using Improved DSP Receiver

A long haul optical communication system (LHOCS) is one of the key resources to fulfill the higher capacity requirements in future communication networks. To launch LHOCS, the system mainly faces high order nonlinear effects. The four-wave mixing (FWM) is one of the major nonlinear effects, which limits the transmission distance. Therefore, in this paper, an advanced duo-binary (DB) modulation scheme-based system is evaluated by employing an improved digital signal processing (IDSP) approach at the receiver side to suppress the FWM effect. In addition, an analytical analysis is also performed for the proposed system. To observe the difference between the IDSP and conventional digital signal processing (DSP), the various performance metrics such as bit error rate (BER), Q-factor, and optical signal-to-noise ratio (OSNR) parameters are evaluated. Variable channel spacing along with polarization mode dispersion (PMD) are analyzed at several ranges of input powers and fiber lengths. The analytical and simulation-based calculations exhibit the effectiveness of the proposed model and hence, FWM effect are compensated to achieve 500 km optical fiber propagation range with a BER below 10−6.

Characterization of Four-Wave Mixing in Specialty Silica Fibers at 2 μm Using Continuous-Wave Pumps

We report the characterization of continuous-wave four-wave mixing (FWM) in SM1950 and SMF-28 silica fibers in the 2 μm wavelength band. Maximum conversion efficiencies of -21 dB and -25 dB are achived for SM1950 and SMF-28 fibers, respectively. In order to explore multichannel wavelength conversion at 2 μm, we characterize the wavelength conversion of a three-tone signal, which is generated by intensity modulation of a laser using a 10 GHz radio frequency (RF) signal. For all the three channels, we achieve a conversion efficiency of -25 dB using a 21.8 dBm pump. Recent demonstrations of efficient splicing of hollow-core fibers, which have been proposed for optical communications at 2 μm, with silica-based fibers paves the way for all-optical processing of multi-channel signals such as orthogonal frequency-division multiplexing (OFDM).

基于光子晶体光纤四波混频效应的甲烷传感测量

基于光子晶体光纤四波混频效应的甲烷传感测量

Generation Efficiency of Fiber Four-Wave Mixing for Phase-Shift Keying Signal Light

Generation Efficiency of Fiber Four-Wave Mixing for Phase-Shift Keying Signal Light

Photon-Pair Sources Based on Intermodal Four-Wave Mixing in Few-Mode Fibers

Four-wave mixing in optical fibers has been proven to have many applications within processing of classical optical signals. In addition, recent developments in multimode fibers have made it possible to achieve the necessary phase-matching for efficient four-wave mixing over a very wide bandwidth. Thus, the combination of multimode fiber optics and four-wave mixing is very attractive for various applications. This is especially the case for applications in quantum communication, for example in photon-pair generation. This is the subject of this work, where we discuss the impact of fluctuations in core radius on the quality of the heralded single-photon states and demonstrate experimental results of intermodal spontaneous four-wave mixing for photon-pair generation.

Cascaded Raman and Intermodal Four-Wave Mixing in Conventional Non-Zero Dispersion-Shifted Fiber for Versatile Ultra-Broadband Continuum Generation

We demonstrate an efficient ultra-broadband supercontinuum generation in telecom-grade optical fiber by pumping Q-switched subnanosecond laser pulses (0.77 ns) at 1064 nm in the normal dispersion region of the fiber. The fiber supports several spatial modes at this pump wavelength. Multiple sidebands with six Raman stokes spanning over more than 1100 nm (starting well below 600 nm and extending beyond 1700 nm) are generated using very low input pump power (average 57 mW). Theoretical analysis shows that cascaded Raman and cascaded intermodal four-wave mixing processes can account for the generation of multiple sidebands. We also demonstrate that the modal composition of the input pump profile can provide an extra degree of freedom in tailoring the multiple Raman peaks in the output spectrum.

Intermodal Four-Wave Mixing and Parametric Amplification in Kilometer-Long Multimode Fibers

We theoretically and numerically investigate intermodal four-wave-mixing in km-long fibers, where random birefringence fluctuations are present along the fiber length. We identify several distinct regimes that depend on the relative magnitude between the length scale of the random fluctuations and the beat-lengths of the interacting quasi-degenerate modes. In addition, we analyze the impact of polarization mode-dispersion and we demonstrate that random variations of the core radius, which are typically encountered during the drawing stage of the fiber, can represent the major source of bandwidth impairment. These results set a boundary on the limits of validity of the classical Manakov model and may be useful for the design of multimode parametric amplifiers and wavelength converters, as well as for the analysis of nonlinear impairments in long-haul spatial division multiplexed transmission.

Photon statistics of pulse-pumped four-wave mixing in fiber with weak signal injection**Project supported by the National Natural Science Foundation of China (Grant No. 11527808), the State Key Development Program for Basic Research of China (Grant No. 2014CB340103), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120032110055), the Natural Science Foundation of Tianjin, China

We study the photon statistics of pulse-pumped four-wave mixing in fibers with weak coherent signal injection by measuring the intensity correlation functions of individual signal and idler fields. The experimental results show that the intensity correlation function of individual signal (idler) field decreases with the intensity of signal injection. After applying narrow band filter in signal (idler) band, the value of decreases from 1.9 ± 0.02 (1.9 ± 0.02) to 1.03 ± 0.02 (1.05 ± 0.02) when the intensity of signal injection varies from 0 to 120 photons/pulse. The results indicate that the photon statistics changes from Bose–Einstein distribution to Poisson distribution. We calculate the intensity correlation functions by using the multi-mode theory of four-wave mixing in fibers. The theoretical curves well fit the experimental results. Our investigation will be useful for mitigating the crosstalk between quantum and classical channels in a dense wavelength division multiplexing network.

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.

一种三角形微结构光纤四波混频的研究

一种三角形微结构光纤四波混频的研究

Schmidt decompositions of parametric processes I: Basic theory and simple examples

Parametric devices based on four-wave mixing in fibers perform many signal-processing functions required by optical communication systems. In these devices, strong pumps drive weak signal and idler sidebands, which can have one or two polarization components, and one or many frequency components. The evolution of these components (modes) is governed by a system of coupled-mode equations. Schmidt decompositions of the associated transfer matrices determine the natural input and output mode vectors of such systems, and facilitate the optimization of device performance. In this paper, the basic properties of Schmidt decompositions are derived from first principles and are illustrated by two simple examples (one- and two-mode parametric amplification). In a forthcoming paper, several nontrivial examples relevant to current research (including four-mode parametric amplification) will be discussed.

Fiber four-wave mixing source for coherent anti-Stokes Raman scattering microscopy

We present a fiber-format picosecond light source for coherent anti-Stokes Raman scattering microscopy. Pulses from a Yb-doped fiber amplifier are frequency converted by four-wave mixing (FWM) in normal-dispersion photonic crystal fiber to produce a synchronized two-color picosecond pulse train. We show that seeding the FWM process overcomes the deleterious effects of group-velocity mismatch and allows efficient conversion into narrow frequency bands. The source generates more than 160 mW of nearly transform-limited pulses tunable from 775 to 815 nm. High-quality coherent Raman images of animal tissues and cells acquired with this source are presented.

Interference in a Quantum Channel Due to Classical Four-Wave Mixing in Optical Fibers

The second-order coherence function for idler photons generated through stimulated four-wave mixing (FWM) is theoretically derived, considering both spontaneous and stimulated Raman contributions. Two distinct cases and two different power regimes are analyzed. First, we consider that the idler wave is fully generated inside the fiber. In a second scenario, we admit that at the fiber input there exist a quantum channel and idler photons will be created at that frequency through the combined processes of FWM and Raman scattering. Results show that for the first case, in a low power regime, the idler photons follow a thermal statistics. In a moderate power regime, the statistics of the generated idler wave presents a Poissonian distribution. Results also show that in the second case, in a low power regime, the statistics of the input quantum channel goes from a Poissonian statistics at the fiber input to a thermal statistics at the fiber output. Findings show that in a moderate power regime, the quantum channel maintains its Poissonian distribution through fiber propagation.

Simultaneous frequency conversion, regeneration and reshaping of optical signals

Nondegenerate four-wave mixing in fibers enables the tunable and low-noise frequency conversion of optical signals. This paper shows that four-wave mixing driven by pulsed pumps can also regenerate and reshape optical signal pulses arbitrarily.