Zero-dispersion Wavelength Region Research Articles

Ultralow chromatic dispersion measurement of optical fibers with a tunable fiber laser

We describe a novel convenient technique to allow for the accurate measurement of the dispersion coefficients till fourth-order in the zero-dispersion wavelength region of single-mode optical fibers. The proposed method is based on a careful spectral analysis of modulation instability occurring in both normal and anomalous dispersion regime and the associated dispersive waves emitted by soliton fission. It simply requires a high-power tunable continuous-wave fiber laser and an optical spectrum analyzer and is able to retrieve both the sign and magnitude of dispersion coefficients with enhanced precision

Spectral broadening of a partially coherent CW laser beam in single-mode optical fibers

The nonlinear propagation of a partially coherent continuous-wave laser beam in single-mode optical fibers is investigated both theoretically and experimentally, with a special attention to the zero-dispersion wavelength region where modulation instability is expected. Broadband asymmetric spectral broadening is reported experimentally and found in fairly good agreement with a numerical Schrödinger simulation including a phase-diffusion model for the partially coherent beam. This model shows in addition that the underlying spectral broadening mechanism relies not only on modulation instability but also on the generation of high-order soliton-like pulses and dispersive waves. The coherence degradation which results from these ultrafast phenomena is confirmed by autocorrelation measurement.

Broadband and flat parametric amplifiers with a multisection dispersion-tailored nonlinear fiber arrangement

We describe a simple scheme to allow for the achievement of flat gain over ultrabroad bands with a single-pump fiber-optic parametric amplifier operating in the zero-dispersion wavelength region. The proposed method, based on a multisection dispersion-tailored in-line nonlinear fiber arrangement, is demonstrated by both modulational instability theory and numerical simulations of the nonlinear Schrödinger equation. The results show that the design can be adjusted to generate gain bands that exceed either 100 nm with a ripple of less than 0.2 dB and for a pump power of only 500 mW, or even 200 nm when a pump power of 5 W is used. In addition, the robustness of this gain-flattening technique has been numerically checked against random fluctuations of the zero-dispersion wavelength in each of the fiber sections.

Adaptive dispersion slope equalizer using a nonlinearly chirped fiber Bragg grating pair with a novel dispersion detection technique

We realized the first adaptive-dispersion equalizer that equalizes dispersion over a wide wavelength range (6 nm) in the zero-dispersion wavelength region of a dispersion-shifted fiber (DSF). The equalizer is based on a pair of nonlinearly chirped fiber Bragg gratings, which are designed to equalize exactly the dispersion profile of a DSF. The dispersion changes were tracked using a technique that employs opposite dispersion fibers to identify the sign of the dispersion change. Unlike previous approaches, no additional sources or changes in the source wavelength are required. We demonstrate the adaptive equalization of the dispersion changes in an 83-km DSF, induced by temperature changes between -10/spl deg/C and 60/spl deg/C.

22 x 10 Gb/s WDM transmission based on extended method of unequally spaced channel allocation around the zero-dispersion wavelength region

This letter proposes all unequally spaced channel allocation method that increases the number of channels around the zero-dispersion wavelength region. The validity of this method is confirmed by numerical simulation considering the fluctuation of the zero-dispersion wavelength existing along the installed 1.55-/spl mu/m dispersion-shifted fibers (DSF's). A 22/spl times/10 Gb/s transmission experiment over 320 km of DSF using the wavelengths ranging from 1532 to 1562 nm is successfully conducted by employing this method.

Propagation of short pulses with fluctuating peak power in the zero-dispersion wavelength region of single-mode fibers

We address the propagation properties of short, noisy pulses in the spectral vicinity of the zero-dispersion wavelength of single-mode fibers. We present a numerical propagation model that includes amplitude fluctuations by introducing a Gaussian statistical distribution of the peak powers. Experiments that use as a source a figure-eight-shaped fiber laser terminated by various types and lengths of dispersion-shifted fiber confirm the calculated propagation properties. We demonstrate the dependence on mean peak power, on noise, and on fiber length of the spectral and temporal evolutions of the propagating pulses.

Assessment of dispersion varying fibre in WDM systems

The authors report that dispersion varying fibre, in which chromatic dispersion decreases (or increases) along its length, can be used to improve the input power limitation in wavelength division multiplexing systems. The presented fibre has a better signal to noise ratio against four-wave mixing in the zero-dispersion wavelength region than conventional dispersion-shifted fibre.

Design of highly efficient four-wave mixing devices using optical fibers

A design theory of the four-wave mixing (FWM) devices using optical fibers is presented. We find that the signal-to-idler conversion process in the zero-dispersion wavelength region yields the widest conversion bandwidth, and the conversion efficiency can be maximized by choosing the optimum fiber length. The maximum conversion efficiency thus obtained is proportional to the square of the input pump power, but is limited by the stimulated Brillouin scattering (SBS) process in the fiber. We show experimentally the improvement of the conversion efficiency by the SBS suppression and the validation of the proposed theory.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Crosstalk and power penalty due to fiber four-wave mixing in multichannel transmissions

The influence of fiber four-wave mixing on multichannel transmissions is investigated. We present strict and approximate theoretical treatments for evaluating power penalty with intensity-modulated/direct-detection (IM/DD) and FSK/direct detection. A comparison of calculations shows that both methods yield the same result in the small penalty region. Using these treatments, power penalty and allowable fiber input power are derived for various system conditions. It is shown that the power penalty is not uniquely determined by the crosstalk level for CW lights, depending on the demodulation scheme and channel spacing, especially in the zero-dispersion wavelength region. >

Suppression technique for fiber four-wave mixing using optical multi-/demultiplexers and a delay line

A technique is proposed for suppressing four-wave mixing (FWM) in optical fiber lines that have multistage optical amplifiers. The phase relationship of the FWM light components is randomized by combinations of optical multi-/demultiplexers and a delay line, so that the total FWM light power is reduced. A preliminary experiment confirming the suppression mechanism is carried out, and the effect of the new suppression technique in multichannel systems is evaluated. The calculations show that the technique reduces the FWM crosstalk in the zero-dispersion wavelength region. >

Four-wave mixing in an optical fiber in the zero-dispersion wavelength region

Fiber four-wave mixing (FWM) in the zero-dispersion wavelength region is described. The phase-matching characteristics are studied in the wavelength region where the first-order chromatic dispersion is zero. The results show that the phase-matching condition is satisfied and FWM light is efficiently generated at particular combinations of input light wavelengths. It is also shown that the deviation of the zero-dispersion wavelength along the fiber length plays an important role in FWM behavior.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>