Search results for "Modula"
showing 10 items of 1481 documents
Observation of modulational instability induced by velocity-matched cross-phase modulation in a normally dispersive bimodal fiber
2008
We demonstrate experimentally the existence of cross-phase-modulation-induced modulational instability in the absence of group-velocity mismatch between the interacting nonlinear dispersive waves. The experiment is performed by means of a normally dispersive isotropic bimodal fiber. The group-velocity mismatch between the fundamental and the first-order modes that constitute the two interacting waves is controlled by wavelength tuning. A strong power dependence of the modulational instability spectra is observed near the condition of group-velocity matching.
Critical behavior with dramatic enhancement of modulational instability gain in fiber systems with periodic variation dispersion
2008
International audience; We analyze modulational instability (MI) of light waves in fiber systems with periodically varying dispersion. The dispersion fluctuation generates special waves, called nonconventional MI sidebands, which are shown to be highly sensitive to two fundamental system parameters. The first one is the average dispersion of the system. Surprisingly, the second parameter turns out to be the mean value of the dispersion coefficients of the two types of fibers of the system, which is then called “central dispersion.” These two parameters are used to control and optimize the MI process. In particular, we establish the existence of a critical region of the central dispersion at…
40 GHz pulse source based on cross-phase modulation-induced focusing in normally dispersive optical fibers.
2016
We theoretically and experimentally investigate the design of a high-repetition rate source delivering well-separated optical pulses due to the nonlinear compression of a dual-frequency beat signal within a cavity-less normally dispersive fiber-based setup. This system is well described by a set of two coupled nonlinear Schrodinger equations for which the traditional normally dispersive defocusing regime is turned in a focusing temporal lens through a degenerated cross-phase modulation process (XPM). More precisely, the temporal compression of the initial beating is performed by the combined effects of normal dispersion and XPM-induced nonlinear phase shift provided by an intense beat signa…
Stable coupled conjugate solitary waves in optical fibers.
1998
Four-wave mixing of an intense continuous-wave pump beam with an ultrashort soliton signal in an optical fiber is theoretically analyzed. A novel class of stable two-color coupled solitary waves is found. These vector parametric solitons represent the optimal frequency conversion of an ultrashort pulse. © 1998 Optical Society of America.
Analytical design of densely dispersion-managed optical fiber transmission systems with Gaussian and raised cosine return-to-zero Ansätze
2004
We propose an easy and efficient way to analytically design densely dispersion-managed fiber systems for ultrafast optical communications. This analytical design is based on the exact solution of the variational equations derived from the nonlinear Schrodinger equation by use of either a Gaussian or a raised-cosine (RC) Ansatz. For the input pulses of dispersion-managed optical fiber transmission systems we consider a RC profile and show that RC return-to-zero pulses are as effective as Gaussian pulses in high-speed (160-Gbits/s) long-distance transmissions.
Higher-order modulation instability in fiber optics
2012
We report on analytical, numerical and experimental studies of higher-order modulation instability in fiber optics. This new form of instability arises from the nonlinear superposition of elementary instabilities and manifests as complex, yet deterministic temporal pulse break-up dynamics. We use the Darboux transformation to analytically describe the process and compare with experiments. In particular, we show how suitably low frequency modulation on a continuous wave field allows for the excitation of higher-order modulation instability through cascaded four-wave mixing.
Dynamic path length changes in all-fiber mirrors: Transmission modulation
1995
Abstract In this paper, we present a technique to modulate the transmission of an all-fiber mirror. This technique is based on the phase modulation of the light in the fiber loop, combined with the time delay between the clockwise and anticlockwise propagating beams. Using Jones calculus, a theoretical analysis has been carried out to describe the effects of static polarization changes and a dynamic phase modulation. An experimental all-fiber optical mirror has been constructed, and using a 1–MHz piezoelectric disc as the phase modulator, we demonstrate that it is possible to achieve either a 1–MHz or 2–MHz transmission modulation by adjusting the polarization state.
In-fiber all-optical fractional differentiator
2009
We demonstrate that an asymmetrical pi phase-shifted fiber Bragg grating operated in reflection can provide the required spectral response for implementing an all-optical fractional differentiator. There are different (but equivalent) ways to design it, e.g., by using different gratings lengths and keeping the same index modulation depth at both sides of the pi phase shift, or vice versa. Analytical expressions were found relating the fractional differentiator order with the grating parameters. The device shows a good accuracy calculating the fractional time derivatives of the complex field of an arbitrary input optical waveform. The introduced concept is supported by numerical simulations.
Optimization of wavelength division multiplexing in N×160Gbit/s terrestrial transmission systems
2005
Abstract We analyze, from an engineering viewpoint, the prospects of an exploitable upgrade of terrestrial fiber systems based on standard monomode fiber and dispersion compensating units, for future N × 160 Gbit/s transmission systems. We show that dispersion swing, average dispersion and input pulse power are the key parameters that govern the system performances. We show that whenever the dispersion swing is arranged in a symmetrical setup and the compensation ratio is optimized accordingly, one may obtain a significant improvement of the transmission performances.
Observation of Modulational Instability induced by a dynamical Bragg grating in an optical fiber
2001
We present a detailed experimental study on Bragg Modulational Instability in a highly birefringent fiber. The originality of our scheme is that the index modulation is obtained through cross phase modulation with a beating wave.