Large Chromatic Dispersion Research Articles

Measurements of the nonlinear coefficient of standard, SMF, DSF, and DCF fibers using a self-aligned interferometer and a Faraday mirror

Using a method based on the detection of the Kerr phase shift by a self-aligned interferometer, we present measurements of the nonlinear coefficient n/sub 2//A/sub eff/ for standard single-mode fiber (SMF), dispersion-shifted fibers, and dispersion compensating fibers. The presence of a Faraday mirror in the interferometer makes the setup very robust, and different test fibers can be measured without any further readjustments. Interlaboratory comparisons show that the values found with our method are in good agreement with the other ones. Further, analysis of a SMF fiber with large chromatic dispersion shows a good reproducibility of the n/sub 2//A/sub eff/ measurements as a function of fiber length.

Polarization and Color Separator Using Binary Phase Grating with Subwavelength Period

A data projector using three liquid crystal display panels has a complex optical system. The illuminating optics separate the beam from a light source into three primary colors and separate those into opposite polarizations using multi-layer films and prisms. A reflection grating with the period of subwavelength has high diffraction efficiency for p polarized light and high regularly reflectance for s polarized light. The diffraction angle of a grating largely depends on the wavelength, because a diffractive optical element (DOE) has large chromatic dispersion. The grating with the period of subwavelength can separate the unpolarized light into polarization components effectively using its polarization dependency and can separate white light into color components using its chromatic dispersion simultaneously. The grating makes the optical system simpler and smaller than those with conventional devices. In this paper the efficiency of polarization separation for the grating is calculated by a rigorous analytical method. Next, the condition for color separation is calculated by Snell#x0027;s law, and an optical system using a grating that performs polarization and color separation is proposed. Experimental results of the DOE fabricated are well matched with those of this simulation.

10 Gbit/s alternate polarisation soliton transmission over 300 km step-index fibre link with no in-line control

A straight-line in-field transmission was performed over a 300 km step-index fibre link installed between Roma and Pomezia using a 10 Gbit/s stream of 1550 nm alternate-polarisation solitons. Standard SDH 10 Gbit/s line terminals were used at the transmitter and receiver sides. Error-free transmission was obtained with optical amplifiers placed every 50 km and with no in-line soliton control. It is important to underline that in this case the large chromatic dispersion was compensated for by fibre non-linearity without resorting to chromatic dispersion compensators.

Reduction of dispersion impairment of soliton systemsthrough chirp control at amplifier location

Through the use of dispersive elements to control the pulse chirp, it is shown that solitons can average even large chromatic dispersion fluctuations without creating much continuum. It is shown through numerical simulations that 40 Gbit/s can be transmitted with 100 km amplifier spacings over 1600 km without sorting fibres.

Role of pump-induced dispersion on femtosecond soliton amplification in erbium-doped fibers: erratum

The limitation to the amplification of femtosecond pulses by erbium-doped fibers owing to the soliton self-frequency shift may be overcome by using a dispersion-shifted fiber. We show that this result holds irrespective of the relatively large residual frequency-dependent chromatic dispersion that is associated with the pumping of the doping ions. Nevertheless, resonant dispersion may lead to temporal broadening and distortion of the amplified pulse.

Role of pump-induced dispersion on femtosecond soliton amplification in erbium-doped fibers

The limitation to the amplification of femtosecond pulses by erbium-doped fibers owing to the soliton self-frequency shift may be overcome by using a dispersion-shifted fiber. We show that this result holds irrespective of the relatively large residual frequency-dependent chromatic dispersion that is associated with the pumping of the doping ions. Nevertheless, resonant dispersion may lead to temporal broadening and distortion of the amplified pulse.

Amplifiers involving two-photon energy-extraction schemes

Amplifiers based on two-photon decay channels of inverted metastable species are examined from a rate-equation and practical-feasibility viewpoint. Approximate analytical solutions, within the rate-equation approximation, predict that resonant parametric generation coupled with anti-Stokes-stimulated Raman scattering (ASRS) is a strong competitor to straight two-photon emission. Expressions for initial growth rates indicate that large linear chromatic dispersion, proper linear absorptions, and resonant enhancements can initially favor two-photon emission, but that ASRS will ultimately dominate in most practical situations if inversion depletion does not occur early. For an amplifier based on degenerate two-photon processes, this situation has led to the proposal of running the system as an odd-harmonic generator, first extracting energy via two-photon emission followed by greater-than-100% conversion to the third, fifth, seventh, etc., harmonics. This type of amplifier response has important potential applications for laser-induced thermonuclear fusion as well as for the production of coherent vacuum-uv soft-x-ray systems. An examination of practical constraints provides further analytical relationships between various physical properties of prospective metastable species. Combining these results, several two-photon schemes are pointed out. Based on current technology, atomic iodine, which is inverted to the $^{2}P_{\frac{1}{2}}$ state, appears to be the best medium for experiments, but other materials, such as atomic oxygen, show greater promise if absolute population inversions of high-density material are created at high efficiency.