Gaussian Optical Pulse Research Articles

Optical pulse shaping based on a double-phase-shifted fiber Bragg grating

Based on the transfer matrix method, a detailed theoretical and numerical study on double-phase-shifted fiber Bragg grating (FBG) is investigated. Temporal responses of the double-phase-shifted FBG to optical pulse are analyzed and the influence of the two phase-shifts’ position on the reflected output pulse is evaluated. Results demonstrate that very different temporal pulse waveforms can be achieved by adjusting the length ratio (α=L 2/L 1). Specifically, a transform-limited Gaussian input optical pulse can be shaped into flat-top square pulse (α=1.81) or two identical optical pulse sequences (α=1.93).

Continuous Slow and Fast Light Generation Using a Silicon-on-Insulator Microring Resonator Incorporating a Multimode Interference Coupler

Continuously tunable slow and fast light generation using a silicon-on-insulator microring resonator (MRR) incorporating a multimode interference (MMI) coupler is proposed and experimentally demonstrated. The MMI coupler is optimized for the transverse-magnetic mode. By changing the input polarization state, the self-coupling coefficient and the loss factor of the MRR are changed. The depth and the bandwidth of the MRR are tunable by tuning the self-coupling coefficient and the loss factor; thus, a tunable phase shift can be achieved at the resonance wavelength, which leads to the generation of a tunable slow and fast light. The proposed scheme is experimentally evaluated. A tunable slow light with a maximum time delay of 35 ps and a slow-to-fast light with a continuously tunable range of 102 ps are achieved for a 13.5-GHz Gaussian optical pulse by using a double-MMI coupler MRR and a single-MMI coupler MRR, respectively.

Direct Observation of a Pulse Peak Using a Peak-Removed Gaussian Optical Pulse in a Superluminal Medium

A series of experiments is performed to examine the arrival of a pulse peak, using a Gaussian-shaped temporal wave packet as the input pulse and truncating it at various positions on or before the peak of the packet. When the truncating point is within the negative group delay limit of the fast light medium, a smooth Gaussian peak is observed at the exit port, despite the absence of an input pulse peak. The experimental results explicitly demonstrate that the superluminal propagation of a smooth Gaussian-shaped pulse peak is an analytic continuation over time of the earlier portion of the input pulse envelope. To investigate the physical meaning of the pulse peak further, we also examine the propagation of triangular-shaped pulses, for which the pulse peak can be recognized as a nonanalytical point.

Study of Transmission Characteristics of Optical Pulse in the Dispersive Fiber

Chromatic dispersion and nonlinearity effect are the two important factors affecting the optical pulse which propagates in the optical fiber. The former makes the pulse broaden, the latter mainly broaden pulse spectrum. Therefore, the linear and nonlinear dispersive propagation and control of optical pulses in the fiber has always been an important research topic of concern. In this paper, Starting from the nonlinear Schrodinger equation of the optical pulse and neglecting the chromatic dispersion, under the situation of chirp and chirp-free Gaussian pulse, we analytical analyzed, calculated and simulated the frequency chirp, pulse broadening factor and waveform of the Gaussian optical pulses in dispersion fiber. And numerical studied the waveform evolution of chirp-free super-Gaussian optical pulse with distance, analyzed the influence of optical pulse propagation by dispersion in different shapes and different initial chirp.

A Novel Approach to All-Optical Generation of Ultra-Wideband Signals

The generation of ultra-wideband signals in the optical domain is highly desirable for ultra-wideband-over-fiber systems, which has recently become a topic of interest. In this article, a novel and simple approach to achieve all-optical generation of ultra-wideband signals is proposed, which is based on delaying and superimposing optical Gaussian pulses with opposite polarities. The proposed system is capable of generating both ultra-wideband monocycle and doublet pulses, and the polarity of the generated ultra-wideband monocycle pulses can be fast-switched to implement pulse polarity modulation with the required bit pattern. A model to describe the proposed system is developed, and the generation of ultra-wideband signals is demonstrated with simulations and a proof-of-concept experiment.

Compact, flexible and versatile photonic differentiator using silicon Mach-Zehnder interferometers

We propose and experimentally demonstrate the flexibility and versatility of photonic differentiators using a silicon-based Mach-Zehnder Interferometer (MZI) structure. Two differentiation schemes are investigated. In the first scheme, we demonstrate high-order photonic field differentiators using on-chip cascaded MZIs, including first-, second-, and third-order differentiators. For single Gaussian optical pulse injection, the average deviations of all differentiators are less than 6.5%. In the second scheme, we demonstrate multifunctional differentiators, including intensity differentiator and field differentiator, using an on-chip single MZI structure. These different differentiator forms rely on the relative shift between the probe wavelength and the MZI resonant notch. Our schemes show the advantages of compact footprint, flexible functions and versatile differentiation forms. For example, high order field differentiators can be used to generate complex temporal waveforms, such as high order Hermite-Gaussian waveforms. And intensity differentiators are useful for ultra-wideband pulse generation.

High-order photonic differentiator employing on-chip cascaded microring resonators

We propose and experimentally demonstrate a high-order photonic differentiator using on-chip complementary metal oxide semiconductor-compatible cascaded microring resonators, including first-, second-, and third-order differentiators. All the microring resonator units have a radius of 150 μm and a free spectral range of 80 GHz. The microring resonator can implement the first-order derivative of the optical field near its critical coupling region. Hence higher-order differentiation can be obtained by cascading more microring units on a single chip. For the periodical Gaussian optical pulse injection, the average deviations of all differentiators are less than 6.2%. The differentiation of pseudo-random bit sequence signals at 5 Gbit/s is also demonstrated. Our scheme is a compact and low-power-consumption solution since the cascaded microring units are fabricated with compact size on the silicon-on-insulator substrate.

Simple solutions for photonic power-efficient ultra-wideband system assisted by electrical bandpass filter

We propose and experimentally demonstrate two simple solutions for power-efficient ultra-wideband (UWB) radio frequency (RF) system assisted by an electrical bandpass filter (EBPF). In the first solution, any optical Gaussian pulse with enough bandwidth is transmitted over optical fiber link, and then converted to a power-efficient UWB pulse by an EBPF with a passband of 3.1–10.6 GHz. The transmission and modulation of UWB signal is processed in optical domain, whereas the generation of UWB is processed in electrical domain. Both UWB modulations of on-off keying (OOK) and binary phase shift keying (BPSK) are experimentally demonstrated. In the second solution, the EBPF is used to convert any electrical waveform to a power-efficient UWB pulse. Then the electrical UWB pulse is converted to an optical UWB pulse with a Mach-Zehnder modulator (MZM), and then distributed over long haul fiber link. These two solutions embody the advantages of both low-loss longhaul transmission of optical fiber and mature electrical circuits. And the millimeter-wave UWB signal is also demonstrated.

Role of supercurrents on vortices formation in polariton condensates

Observation of quantized vortices in non-equilibrium polariton condensates has been reported either by spontaneous formation and pinning in the presence of disorder or by imprinting them onto the signal or idler of an optical parametric oscillator (OPO). Here, we report a detailed analysis of the creation and annihilation of polariton vortex-antivortex pairs in the signal state of a polariton OPO by means of a short optical Gaussian pulse at a certain finite pump wave-vector. A time-resolved, interferometric analysis of the emission allows us to extract the phase of the perturbed condensate and to reveal the dynamics of the supercurrents created by the pulsed probe. This flow is responsible for the appearance of the topological defects when counter-propagating to the underlying currents of the OPO signal.

Generation Of Quantum Codes Using Up And Down Link Optical Solition

In this study, a system of continuous variable quantum code via a wavelength router is presented. The optical Kerr type nonlinearity in the nonlinear microring resonator (NMRR) induces the chaotic behavior. In this proposed system chaotic signals are generated by an optical soliton or Gaussian pulse within a NMRR system. Large bandwidth signals of optical soliton are generated by the input pulse propagating within the MRRs, which is allowed to form the continuous wavelength or frequency with large tunable channel capacity. Therefore, distinguished up and down links of wavelength or frequency pulses can be generated by using localized spatial soliton via a quantum router and networks. These selected up and down links pulses are more suitable to generate high secured quantum codes because of the greater free spectral range (FSR). The continuous quantum codes can be generated by using the polarization control unit and beam splitter, incorporating into the MRRs. In this work, frequency band of 10.7 MHz and 16 MHz and wavelengths of 206.9 nm, 1.448 μm, 2.169 μm and 2.489 μm can be obtained for QKD by using input optical soliton and Gaussian beam. Key words: Nonlinear microring resonator (NMRR); up and down links optical soliton, quantum codes

Optical time-domain differentiation based on intensive differential group delay

An optical time-domain differentiation scheme is proposed and demonstrated based on the intensive differential group delay in a high birefringence fibre waveguide. Results show that the differentiation waveforms agree well with the mathematically calculated derivatives. Both error and efficiency will increase when the birefringence fibre becomes longer, and the error rises up more quickly while the efficiency approaches to a maximum of ∼0.25. By using a 1-m birefringence fibre a lower error of ∼0.26% is obtained with an efficiency of 1% for the first-order differentiation of 10-ps Gaussian optical pulses, and the high-order optical differentiation up to 4th order is achieved with an error less than 3%. Due to its compact structure being easy to integrate and cascade into photonic circuits, our scheme has great potential for ultrafast signal processing.

All-optical UWB signal generation and multicasting using a nonlinear optical loop mirror

An all-optical scheme for ultra-wideband (UWB) signal generation (positive and negative monocycle and doublet pulses) and multicasting using a nonlinear optical loop mirror (NOLM) is proposed and demonstrated. Five UWB signals (1 monocycle and 4 doublet pulses) are generated simultaneously from a single Gaussian optical pulse. The fractional bandwidths of the monocycle pulses are approximately 100% while those of the doublet pulses range from 100% to 133%. The UWB signals are then modulated using a 2(15)-1 pseudorandom bit sequence (PRBS) and error-free performance for each multicast channel is obtained.

Continuously Tunable Photonic Fractional Temporal Differentiator Based on a Tilted Fiber Bragg Grating

A tunable temporal photonic fractional differentiator implemented based on a tilted fiber Bragg grating is proposed and demonstrated. The phase response at a cladding mode resonant wavelength is strongly polarization-dependent and the fractional order of the photonic differentiator can be continuously tuned by changing the polarization state of the input light wave. A proof-of-concept experiment is carried out. The fractional differentiation of an optical Gaussian pulse with a bandwidth of 40 GHz is demonstrated, in which the fractional order is continuously tuned from 0.81 to 1.42.

Capacity Enhancement in Communication System via NNRR

We present the effect of the FSR on capacity of communication system. A new novel system of soliton generation using a 1.30μm optical Gaussian pulse in a nonlinear nano-ring resonator (NNRR) system forms the soliton pulse train. The soliton pulse wavelength with center wavelength at 1.30μm is generated after a powerful Gaussian soliton pulse is input into the NNRR system, we propose a system that can be used to solve many problems in communication systems. The results show that we how do receive the free spectrum range (FSR) by NNRR. This is obtained via the add/drop filter, which can be used to increase the channel capacity in the communication network. In this paper the best FSR is 0.052nm. This result allows the channel capacity expanding due to the abundance of propagation spacing from the soliton collision.

UWB Impulse Radio Transmitter Using an Electrooptic Phase Modulator Together With a Delay Interferometer

A simple ultra-wideband (UWB) impulse radio transmitter is experimentally demonstrated using an electrooptic phase modulator (PM) and a delay interferometer (DI). By applying an electrical nonreturn-to-zero (NRZ) baseband signal to the PM, a pair of optical Gaussian pulses with opposite polarities is generated at the two output ports of the DI. By properly setting the delay between these two polarity-reversed optical Gaussian pulses using an optical delay line (ODL) component, an optical UWB monocycle pulse is generated. Pulse amplitude modulation of the UWB monocycle pulse can also be achieved by driving the PM with an NRZ baseband signal at a flexible bit rate. Experimental results verify that the proposed scheme can be used to simultaneously generate and amplitude modulate the UWB monocycle pulse. Furthermore, both the shape and polarity of the generated UWB monocycle pulse can be easily controlled by appropriately adjusting the delay of the ODL. Pulse polarity modulation of the generated UWB monocycle can also be realized by electrically switching the bias voltage of the DI.

Simultaneous multi-channel CMW-band and MMW-band UWB monocycle pulse generation using FWM effect in a highly nonlinear photonic crystal fiber

We propose and experimentally demonstrate a scheme to simultaneously realize multi-channel centimeter wave (CMW) band and millimeter wave (MMW) band ultra-wideband (UWB) monocycle pulse generation using four wave mixing (FWM) effect in a highly nonlinear photonic crystal fiber (HNL-PCF). Two lightwaves carrying polarity-reversed optical Gaussian pulses with appropriate time delay and another lightwave carrying a 20 GHz clock signal are launched into the HNL-PCF together. By filtering out the FWM idlers, two CMW-band UWB monocycle signals and two MMW-band UWB monocycle signals at 20 GHz are obtained simultaneously. Experimental measurements of the generated UWB monocycle pulses at individual wavelength, which comply with the FCC regulations, verify the feasibility and flexibility of proposed scheme for use in practical UWB communication systems.

Phase mismatching slope optimization for magneto-optic pulse compression

The collinear diffraction effects of linearly chirped Gaussian optical pulses with continuous magneto-static surface waves (MSSWs) excited in magneto-optic (MO) film waveguides under a horizontal bias magnetic field are theoretically studied. MO pulse coupling equations and the analytic solution are presented. It is shown that optical pulse compression based on MO Bragg diffraction is dependent on phase mismatching slope, which can be greatly increased by using different mode-number of incident and diffracted guided optical waves (GOWs) and appropriately choosing normalized thickness of MO film (ratio of the film thickness to the light wavelength). In TE 0 → TM 8 diffraction full-width-at-half-maximum (FWHM) ratio of the diffracted and incident optical pulses comes up to 38%.

Generation of microwave and millimeter-wave based on polarization scrambler and polarization maintaining fiber

A new method is proposed to generate microwave and millimeter-wave by using polarization scrambler and polarization maintaining fiber (PMF), which is based on the coupling and the interaction between the two polarizations of the initial non-chirp Gaussian optical pulse in PMF. The expressions of the microwave and millimeter-wave are derived by couplemode theory. Moreover, the feasibility is analyzed simulatedly. At last, 0−120 GHz microwave and millimeter-wave can be produced by adjusting system parameter or input pulse duration. The project is of great simplicity, stability and high export efficiency.

Signal Analysis by New Mother Wavelets

Based on the general formula for finding qualified mother wavelets [Opt. Lett. 31 (2006) 407] we make wavelet transforms computed with the newly found mother wavelets (characteristic of the power 2n) for some optical Gaussian pulses, which exhibit the ability to measure frequency of the pulse more precisely and clearly. We also work with complex mother wavelets composed of new real mother wavelets, which offer the ability of obtaining phase information of the pulse as well as amplitude information. The analogy between the behavior of Hermite–Gauss beams and that of new wavelet transforms is noticed.

Compression of Linearly Chirped Gaussian Optical Pulses Induced by Microwave Magneto-Static Waves

According to the coupled-mode theory of magneto-optic (MO) effects as a perturbation, the coupling equations for optical pulses with microwave magneto-static waves (MSWs) in MO film waveguides are presented, which can be used to analyze MSW-based optical pulse signal processing. For the case of a continuous MSW, the analytic expression for the complex amplitudes of diffracted and undiffracted optical pulses is obtained in frequency domain and then the compression characteristics of linearly chirped Gaussian optical pulses are studied in detail. The peak intensity of diffracted optical pulses is approximately proportional to the matching diffraction efficiency. With the increase of chirp parameters, the diffracted pulse waveforms go through two stages: single peak compression and multi-peak expansion.