Dispersive Optical Fiber Research Articles

Perturbed solution and analyses for single photon transmission equation in optical fiber

As is well known, quantum optics has developed significantly in recent years and advanced several hot research topics, such as quantum communications, quantum sensing, quantum calculations, etc. Among these researches, it is important to understand the quantum information transmitting in optical fiber. For realizing longer transmission distance and better transmission quality, great effort has devoted to the researches of encoding and decoding at the transmitter and the receiver end. However, less attention was paid to the fading of signal in the transmission channel. In this work, we mainly focus on the transmission model of optical quantum transmission and the influences of loss, dispersion and nonlinear effect on fiber transmission of optical quantum information are also discussed.Quantum information transmission can be influenced by loss, dispersion and nonlinear effect in optical fiber, leading to transmission state evolution and energy transfer. Based on the transmission equation of single mode fiber and quantum theory of electromagnetic field, the fundamental mode field of single mode fiber is quantized. A quantum transmission equation is deduced from the classical optical transmission equation through quantizing the amplitude of electromagnetic field. Compared with classic wave theory, the photon transmission equation quantizing the slowly-varying amplitude in the coupled nonlinear Schrdinger equation is obtained. In the classic wave equation, light is interpreted as energy which propagates as waves. The photon transmission equation is obtained by quantizing the slowly-varying amplitude of light, that is, the particle nature of light. The energy propagates through alternative interaction between creation and annihilation operator on photons. The transmission equations show that photons will interact with the transmission medium during propagation and be influenced by dispersion, nonlinear effect, loss, etc. By giving a trail solution and introducing a perturbation term, the transmission equation is solved for the complicated case where the dispersion, loss and nonlinear effect are all involved. A dispersion equation that should be satisfied for nontrivial solution is then obtained. From this dispersion equation, the relation between photon power and perturbation frequency is calculated and analyzed. The change of photon power in generalized field with perturbation frequency is discussed, and the influences of fiber dispersion and nonlinearity on the solution are analyzed.Some conclusions are obtained by perturbed solution and analyses of single photon transmission equation in optical fiber. It is found that photon power decreases with the increase of perturbation frequency and reaches its maximum value for zero perturbation frequency. At the same time, the optical power is affected by the dispersion of the optical fiber. Photon power decreases with the GVD coefficient far from the zero dispersion point. It is also found that photon power decreases with the increase of nonlinear coefficient. This work may contribute to the research of the properties of quantum fiber transmission system.

OBI reduction and optical power budget enhancement in OFDM-PON system using spreading code in electrical domain

Orthogonal frequency division multiplexing based passive optical network (OFDM-PON) gives better performance in high speed optical access networks because of its greater resistance to optical fiber dispersion and high bandwidth efficiency. Optical beating interference (OBI) is one of the main source of impairment which occurs in upstream direction. This paper proposes to use CDM/OFDM based PON architecture to reduce OBI in upstream and also improves optical power budget. In the analysis, no optical dispersion compensation has been used and all system related impairments have been considered for amplitude modulation/direct detection (AM/DD) optical communication system. Results depict that with BER value of 10−3, there is 8.1dB gain in signal-to-noise ratio (SNR) and 5dB, 9.5dB improvement in optical power budget in downstream and upstream respectively. There is also 4.5dB reduction in OBI in upstream direction with CDM/OFDM-PON system as compared to OFDM-PON system.

Overcoming the limitation of phase retrieval using Gerchberg-Saxton-like algorithm in optical fiber time-stretch systems.

We investigate the fundamental limitation of the full-field retrieval of optical pulses based on a time-equivalent Gerchberg-Saxton (GS)-like algorithm, in which the Fourier transformation of the temporal signal is performed by the group velocity dispersion (GVD) of optical fibers. The insufficient knowledge of the input pulse intensity fundamentally limited by the bandwidth of the photodetector influences the accuracy of the retrieved phase using the algorithm. To this end, we propose a modified GS algorithm, which involves multi-step intensity-only measurements, to mitigate this limitation. By studying the influence of spectral phase and amplitude modulations on the retrieval error, we show that the modified GS algorithm demonstrates a significant improvement in phase retrieval accuracy. More importantly, we anticipate the present study will provide valuable insight in understanding how the spectral variation generally influences the recovery accuracy in time-stretch-based GS algorithm, and thus identify its potential applications, particularly for those requiring ultrafast measurements.

Dual-pump frequency comb generation in normally dispersive optical fibers

We show that tunable frequency combs can be generated by launching two continuous-wave pumps at slightly different wavelengths into a normally dispersive optical fiber. The dual-pump configuration allows the tuning of comb spacing into the terahertz regime. Different pump powers and frequency separations are explored numerically to determine the effect of the input parameters on frequency comb generation. The relative power of the two pumps is found to be a critical factor through its crucial effect on optical wave breaking. The pump powers and fiber length are shown to have a significant effect on the comb width as well. Unlike in the case of supercontinuum generation, Raman scattering is found to have a negligible or even a slightly detrimental effect. Our findings also help bridge the gap between work done on the propagation of a single pulse and the evolution of dual-pump signals in normally dispersive highly nonlinear fibers.

Modified Nonlinear Decision Feedback Equalizer for Long-Haul Fiber-Optic Communications

In a long-haul optical fiber communication system, fiber attenuation, dispersion, and nonlinearity combined with nondeterministic noise from optical amplifiers used for periodic regeneration cause adverse effects on system performance. Several optical and electrical signal processing techniques have been proposed, and implemented to extract the transmitted data; some provide better performance than others, but at a cost of higher computational complexity. We present a modified nonlinear decision feedback equalizer designed for use in a legacy optical communication system with periodic dispersion compensation. The effects of noise and nonlinearity on the equalizer coefficients are investigated, and a suboptimal convergence algorithm to reduce such effects is proposed and verified. Our equalizer provides performance comparable to that obtained using digital backpropagation, while being computationally simpler, compensating linear and nonlinear physical impairment effects effectively even at high power levels where fiber nonlinearity is significant. Performance prediction of the designed DFE is also discussed, using a numerical method, with and without error propagation.

Prediction of modal dispersion in nonlinear single mode optical fiber using simple Chebyshev technique

We have predicted the normalized group delay and modal dispersion in Kerr nonlinear single mode fibers using a recently proposed simple and efficient Chebyshev method in presence of optical nonlinearity. It is seen that the proposed technique estimates the dispersion parameters accurately since results obtained by our method agree excellently with those from rigorous techniques over a large range of normalized frequency. Although we’ve considered step index fiber as a typical example, our analysis is also applicable to graded index fibers as well.

Ultrafast Nonlinear Fiber Optics: Single-Pulse Supercontinua and Specialty-Shape Pulses

Needs of science and technology for compact laser sources with specially shaped pulse waveforms or ultra-broad spectrum can be satisfied on the fiber-optic platform. Here we address transformation of ultrashort optical pulses in a variety of optical fibers aiming synthesis of specially shaped pulses and single-pulse flat-top supercontinuum. Results are discussed in the context of possible applications and experimental implementations. Full Text: PDF References J. M. Dudley, G. Genty, and S. Coen, "Supercontinuum generation in photonic crystal fiber", Rev. Mod. Phys. 78(4), 1135?1184 (2006). CrossRef A. M. Heidt, A. Hartung, G. W. Bosman, P. Krok, E. G. Rohwer, H. Schwoerer, and H. Bartelt, "Coherent octave spanning near-infrared and visible supercontinuum generation in all-normal dispersion photonic crystal fibers", Opt. Express, 19(4), pp. 3775?3787, (2011). CrossRef A. M. Heidt, J. Rothhardt, A. Hartung, H. Bartelt, E. G. Rohwer, J. Limpert, and A. Tünnermann, "High quality sub-two cycle pulses from compression of supercontinuum generated in all-normal dispersion photonic crystal fiber", Opt. Express 19, 13873-13879 (2011). CrossRef A. Hartung, A. M. Heidt, and H. Bartelt, "Design of all-normal dispersion microstructured optical fibers for pulse-preserving supercontinuum generation", Opt. Express 19, 7742-7749 (2011). CrossRef S. Boscolo and C. Finot, "Nonlinear Pulse Shaping in Fibres for Pulse Generation and Optical Processing", International Journal of Optics 2012, 159057 (2012) CrossRef J. M. Dudley, C. Finot, D. J. Richardson, G. Millot, "Self-similarity in ultrafast nonlinear optics", Nature Physics 3, pp. 597-603, (2007). CrossRef C. Finot, J.M. Dudley, B. Kibler, D.J. Richardson, G. Millot, "Optical Parabolic Pulse Generation and Applications", IEEE J. Quantum Electron. 45, pp. 1482-1489 (2009). CrossRef C. Finot, S. Pitois, and G. Millot, "Regenerative 40 Gbit/s wavelength converter based on similariton generation", Opt. Lett. 30, 1776?1778 (2005). CrossRef Parmigiani, P. Petropoulos, M. Ibsen, and D. J. Richardson, "Pulse retiming based on XPM using parabolic pulses formed in a fiber Bragg grating", IEEE Photon. Technol. Lett. 18, 829?831 (2006). CrossRef S. Boscolo, S. K. Turitsyn, and K. J. Blow, "Time domain all-optical signal processing at a RZ optical receiver", Opt. Express 13, 6217?6227 (2005). CrossRef T. T. Ng, F. Parmigiani, M. Ibsen, Z. Zhang, P. Petropoulos, and D. J. Richardson, "Compensation of Linear Distortions by Using XPM With Parabolic Pulses as a Time Lens", IEEE Photon. Technol. Lett. 20, 1097?1099 (2008). CrossRef S. O. Iakushev, O. V. Shulika, and I.A. Sukhoivanov, "Passive nonlinear reshaping towards parabolic pulses in the steady-state regime in optical fibers", Opt. Commun. 285, 4493?4499, (2012). CrossRef I. A. Sukhoivanov, S. O. Iakushev, O. V. Sulika, A. Díez, M. Andrés, "Femtosecond parabolic pulse shaping in normally dispersive optical fibers", Opt. Express, 21, pp. 17769-17785, (2013). CrossRef S. O. Iakushev, O. V. Shulika, I. A. Sukhoivanov, V. I. Fesenko, M. V. Andres, and H. Sayinc, "Formation of ultrashort triangular pulses in optical fibers", Opt. Express, 22(23), pp. 29119- 29134 CrossRef

Broadband infrared continuum generation in dispersion shifted tapered fiber

Experimental and theoretical studies of supercontinuum generation in the telecom spectral window are reported for fibers with shifted decreasing anomalous dispersion. Numerical analysis highlights the high average power of the emitted dispersive waves and the good spectral flatness achieved within the control spectral band for the supercontinuum generated in optical fiber tapers. Reduction of the third-order dispersion in optical fiber tapers is shown to cause spectral broadening, which is extended by hundreds of nanometers in comparison with the supercontinuum generated in uniform fibers, even when subpicosecond pulses of moderate powers are used.

Dark three-sister rogue waves in normally dispersive optical fibers with random birefringence.

We investigate dark rogue wave dynamics in normally dispersive birefringent optical fibers, based on the exact rational solutions of the coupled nonlinear Schrödinger equations. Analytical solutions are derived up to the second order via a nonrecursive Darboux transformation method. Vector dark "three-sister" rogue waves as well as their existence conditions are demonstrated. The robustness against small perturbations is numerically confirmed in spite of the onset of modulational instability, offering the possibility to observe such extreme events in normal optical fibers with random birefringence, or in other Manakov-type vector nonlinear media.

Phase recovery by using optical fiber dispersion and pulse pre-stretching

In this work, the applicability of a recently proposed phase recovery technique is extended, by using temporal pulse pre-stretching. As a proof of concept, the light pulses emitted by a two-stage laser system consisting of a sub-picosecond passively mode-locked fiber laser followed by an erbium-doped fiber amplifier were experimentally analyzed. These results were successfully compared with two indirect phase recovery techniques, both based on the Gerchberg–Saxton recursive algorithm and with the intensity autocorrelation when sub-picosecond light pulses were analyzed.

Optical Fiber Dispersion Compensation Based on Optic System

In the optical fiber communication system of high-speed and large capacity, the dispersion is one of the main technical indicators. The dispersion causes the light pulse broadening, so it leads to the distortion of signal transmission and BER (bit error rate). The main research is the single-mode optical fiber dispersion compensation. The design and performance of system structure on the dispersion compensation fiber communication system is accomplished by using of the optic system optical fiber communication system simulation. Through the analysis of system structure and the research of the performance of the key components of the system, the output signal waveform is simulated and the influence of the output signal waveform by the system structure and key components performance of the receiving end is compared. The design can reduce the system dispersion.

A new experimental approach to second-order polarization mode dispersion analysis for optical communications systems

This article analyzes the polarization mode dispersion (PMD) in optical fibers and presents a new approach for its measurement. This approach permits the combined analysis of the first-order PMD and the second-order polarization mode dispersion (SOPMD) in optical systems for different values of temperature. The relation between SOPMD and the differential group delay (DGD) in a single-mode fiber is discussed. The analysis is based on time/wavelength and temperature variations changing/impacting PMD and DGD measured values. We present long-term statistical characteristics of SOPMD acquired by a PMD emulator constructed with some pieces of high birefringence fiber, and the correlation between the SOPMD, depolarization (Depol) and polarization-dependent chromatic dispersion (PCD) was investigated. A new interpretation of SOPMD is presented to analyze the problem of the temperature spectral stability. The actual techniques for SOPMD determination, consequently Depol and PCD, use the variation with time and/or wavelength. In some studies, the results obtained for SOPMD are correlated to first-order PMD. We demonstrate experimentally that the temperature is an important factor for the correlation between SOPMD and PMD and cannot be neglected in the optimization of high-speed optical communications links.

Gain sideband splitting in dispersion oscillating fibers

We analyze the modulation instability spectrum in a varying dispersion optical fiber as a function of the dispersion oscillation amplitude. For large dispersion oscillations, we predict a novel sideband splitting into different sub-sidebands. The emergence of the new sidebands is observed whenever the classical perturbation analysis for parametric resonances predicts vanishing sideband amplitudes. The numerical results are in good quantitative agreement with Floquet or Bloch stability analysis of four-wave mixing in the periodic dispersion fiber. We have also shown that linear gain or loss may have a dramatic influence in reshaping the new sidebands.

Fiber chromatic dispersion measurement with improved measurement range based on chirped intensity modulation

A novel method for accurately measuring chromatic dispersion of optical fibers is proposed based on the use of chirped intensity-modulated signals. Unlike the conventional method, the proposed method utilizes the configurable transfer function of optical fibers caused by the residual chirp of intensity modulation, which not only eliminates the chirp error but also improves the measurement range through adjusting the chirp parameter of the intensity modulator. Our method is applicable for measuring both the magnitude and sign of chromatic dispersion of optical fibers or other dispersive devices at different operating wavelengths by using a vector network analyzer.

Stable fiber-optic time transfer by active radio frequency phase locking.

In this Letter we demonstrate a fiber link capable of stable time signal transfer utilizing our active long-distance radio frequency (RF) stabilization technology. Taking advantage of the chromatic dispersion in optical fiber, our scheme compensates dynamically the link delay variation by tuning the optical carrier wavelength to phase lock a round-trip RF reference. Since the time signal and the RF reference are carried by the same optical carrier, a highly stable time transfer is achieved at the same time. Experimentally, we demonstrate a stability of the time signal transfer over 50-km fiber with a time deviation of 40 ps at 1-s average and 2.3 ps at 1000-s average. The performance of the RF reference delivery is also tested, with an Allan deviation of 2×10(-15) at 1000-s average. According to our proposal, a simultaneous stable time and frequency transfer is expected.

Strong group-velocity dispersion compensation with phase-engineered sheet metamaterials

Resonant metamaterials usually exhibit substantial dispersion, which is considered a shortcoming for many applications. Here we take advantage of the ability to tailor the dispersive response of a metamaterial introducing a new method of group-velocity dispersion compensation in telecommunication systems. The method consists of stacking a number of highly dispersive sheet metamaterials and is capable of compensating the dispersion of optical fibers with either negative or positive group-velocity dispersion coefficients. We demonstrate that the phase-engineered metamaterial can provide strong group-velocity dispersion management without being adversely affected by large transmission loss, while at the same time offering high customizability and small footprint.

Temperature effects in optical fiber dispersion compensation modules

Differential group delay measurements of a fiber-based dispersion compensation module under different controlled temperature variations experience long birefringence relaxation times (>10 h) in response to temperature changes. These are interpreted here qualitatively with a stress strain behavioral model based on silica's viscoelastic property.

Turbo Equalization Techniques Toward Robust PDM 16-QAM Optical Fiber Transmission

In this paper, we show numerically and experimentally that turbo equalization (TE) is an efficient technique to mitigate performance degradations stemming from optical fiber propagation effects in both optical fiber dispersion managed and unmanaged coherent detection links. The effectiveness of the proposed solution can be appreciated in both linear and nonlinear regimes for either scenario. We report on a system employing a polarization division multiplexing (PDM) 16-quadrature amplitude modulation (QAM) format for which we accomplish an increment in tolerance to link input power of up to 3 dB that represents a substantial improvement margin. The best bit error rate (BER) performances will therefore be guaranteed in a larger window, 6 dB, of link input power thanks to the implemented TE scheme. Moreover, our proposed approach is also proven to effectively mitigate interchannel impairments from surrounding amplitude shift-keying interfering channels in a dispersion managed link achieving also in this case an increment in power tolerance of 3 dB. Furthermore, in terms of BER performances, our proposed TE approach guarantees a gain of about a half order of magnitude at the best operational point. As TE can be included in the current coherent detection transceiver technologies and complement other equalization techniques, it has prospects for application in next-generation high-capacity and long-reach optical transmission links.

Phase recovery by using optical fiber dispersion

We propose a simple and fast procedure to retrieve the phase profile of arbitrary light pulses. It combines a first experimental stage, followed by a one-step numerical stage. To this end, it is necessary to perform a Fresnel transform, which is obtained just by propagating the light pulses through an optical fiber. We experimentally test this proposal recovering the phase profile in the light pulses provided by a passively mode-locked laser. The proposal is then compared with a temporal variation of the Gerchberg-Saxton recursive algorithm, which is specially modified for this purpose.

Turbo Equalization for Digital Coherent Receivers

High order modulation formats allow to reach higher spectral efficiency and data rate. However, their practical implementation is limited by their reduced tolerance to noise and to the optical signal power that can be launched into the fiber without generating excessive nonlinear signal distortions. In this paper, it is demonstrated that Turbo Equalization routines can be used to mitigate performance degradations stemming from optical fiber propagation effects both in optical fiber dispersion managed and unmanaged coherent detection links. The effectiveness of this solution is analyzed both numerically and experimentally for different transmission systems.