Zero-dispersion Wavelength Of Fiber Research Articles

Spectral compression of femtosecond pulses in photonic crystal fibers

We demonstrate efficient spectral compression of femtosecond pulses near the zero-dispersion wavelength in nonlinear photonic crystal fibers (PCFs). The highest measured compression factor is 21, in which case the spectral brightness increases by a factor of 5. We numerically model the pulse propagation and find good agreement with the experiment. We argue that the fibers studied allow for spectral narrowing of more than 2 orders of magnitude. With dispersion-shifted PCFs, efficient spectral compression can take place across the visible and near-infrared part of the spectrum.

Widely tunable optical parametric generation in a photonic crystal fiber

We report on the observation of widely tunable optical parametric generation in a photonic crystal fiber. The frequency shift of the generated sidebands that arise from modulational instability is strongly dependent on the detuning of the pump from the fiber's zero-dispersion wavelength. We are able to demonstrate experimentally more than 450 nm of sideband tunability as we tune the pump wavelength over 10 nm. Excellent agreement has been found between the experimentally measured and theoretically predicted shifts.

Measurement of co- and cross-polarized Raman spectra in silica fiber for small detunings

We report measurement of co- and cross-polarized Raman gain spectra at the zero-dispersion wavelength of standard dispersion-shifted fiber for detunings down to 0.17 THz (5.7cm-1) on both Stokes and anti-Stokes sides by using a photon-counting technique. This technique separates the Raman scattering from the four-photon scattering. In addition, the use of a pulsed pump eliminates Brillouin scattering and the use of a Sagnac loop rejects the pump photons that spectrally spread into the detection band due to self-phase-modulation.

Temperature control of the gain spectrum of fiber optical parametric amplifiers

The gain spectrum of a fiber optical parametric amplifier (OPA) can be controlled by imposing a temperature distribution along the fiber, which modulates the local fiber zero-dispersion wavelength lambda0, and hence the parametric gain coefficient. We present simulations and experimental verification for various binary temperature distributions. The method should be applicable to fibers with realistic longitudinal variations of lambda0.

Wide-Band Tuning of the Gain Spectra of One-Pump Fiber Optical Parametric Amplifiers

By suitably choosing the fiber properties, and by tuning the pump wavelength near the fiber zero-dispersion wavelength, one can in principle generate a wide variety of one-pump fiber optical parametric amplifier gain spectra. These can range from a very wide single region to two symmetric narrow gain regions far away from the pump. We have experimentally verified these predictions. With a highly nonlinear fiber, we have inferred the existence of gain over a single 400-nm region and measured a maximum on-off gain of 65 dB. With a common dispersion-shifted fiber, we have obtained tunable gain regions less than 1 nm wide, up to 200 nm from the pump; we have also shifted these by several nanometers by lowering the fiber temperature to 0/spl deg/C.

Design of Fiber-Optical Parametric Amplifiers by Genetic Algorithm

Genetic algorithm is adopted to give an automatic design scheme for fiber-based optical parametric amplifiers (FOPAs). Main steps of the optimization process and discussion about this algorithm are presented. The results show that present FOPA has more than 300-nm flat bandwidth with a central wavelength of 1500 nm and a gain ripple of less than 0.3 dB. Meanwhile, fluctuation in zero-dispersion wavelength of fibers is taken into consideration and its influence is briefly analyzed.

Birefringence-induced splitting of the zero-dispersion wavelength in nonlinear photonic crystal fibers.

We investigate how the strongly wavelength-dependent birefringence in nonlinear photonic crystal fibers leads to a splitting in the zero-dispersion wavelength for the two polarizations. We translate the requirements for the maximum splitting of the zero-dispersion wavelength to requirements for transverse structural uniformity by adopting a simple effective-index approach in which the birefringence is calculated in a step-index fiber with an elliptical core. We find that to reduce the splitting to less than 1 nm the birefringence should be less than 2 x 10(-5), resulting in a transverse uniformity requirement of 1-3%, depending on the index step from the core to the cladding.

Optical amplification in bismuth-doped silica glass

We demonstrated an amplification phenomenon in a bismuth-doped silica glass at 1.3 μm with 0.8-μm excitation. This luminescent material is a promising candidate for use as the core-fiber material of an optical amplifier at the natural zero-dispersion wavelength (1.3 μm) of silica glass fiber.

Simultaneous measurements of non-linear coefficient, zero-dispersion wavelength and chromatic dispersion in dispersion-shifted fibers by four-wave mixing

We report on a new simple technique for the simultaneous measurement of non-linear coefficient, zero-dispersion wavelength, and chromatic dispersion in dispersion-shifted fibers based on partially degenerated four-wave mixing. Both zero-dispersion wavelength and chromatic dispersion of the dispersion-shifted fibers can be measured with high accuracy. The experiment results of two dispersion-shifted fibers will be presented and the technique for obtaining accurate chromatic dispersion and zero-dispersion wavelength will also be discussed.

Zero-dispersion wavelength determination in optical fibers using cross-phase modulation

A simple method for determining the zero-dispersion wavelength in optical fibers is proposed. It is based on cross-phase modulation between a tunable continuous-wave signal and copropagating intense pump pulses in an optical fiber. By positioning the pump wavelength in the normal group-velocity dispersion (GVD) regime, the polarity of the generated pulses at the signal wavelength reverses when the signal wavelength is tuned through the zero-dispersion point from the GVD side. The method was experimentally demonstrated for a /spl sim/1 km dispersion-shifted fiber and a measurement accuracy of /spl sim/0.4 nm was obtained. Simulation results also show good agreement with experimental ones.

High-power femtosecond-pulse reshaping near the zero-dispersion wavelength of an optical fiber

Nonlinear propagation of high-power femtosecond pulses close to the zero-dispersion wavelength of a singlemode optical fiber is studied experimentally and numerically. The roles of four-photon mixing, stimulated Raman scattering, and self-steepening in this process are represented through different extensions of the nonlinear Schrödinger equation.

Simple method for measuring dispersion and nonlinear coefficient near the zero dispersion wavelength of optical fibers

We propose a fast and accurate method for measuring the fiber zero-dispersion wavelength, the dispersion slope and the nonlinear coefficient, which are the relevant parameters needed to evaluate the impact of fiber nonlinearity on transmission systems. The method is based on modulation instability sideband generation and uses a single continuous-wave tunable laser and a spectrum analyzer. For the dispersion parameters, our results are in very good agreement with those obtained from commercial instruments.

Tunable fiber-optic parametric oscillator

We report operation of a tunable optical parametric oscillator that employs a nonlinear-fiber Sagnac interferometer as a parametric amplifier. The amplifier, which consists primarily of dispersion-shifted fiber that has zero dispersion at 1538 nm, is synchronously pumped with 7.7-ps pulses at 1539 nm. The wide bandwidth of the parametric gain permits tuning of the output signal pulses over a 40-nm range centered on the pump wavelength. The Sagnac interferometer decouples the pump wave from the oscillator cavity while a bandpass filter in the cavity transmits only the signal wave, thereby creating a singly resonant parametric oscillator that is phase insensitive. Whereas we demonstrate tuning over almost the entire bandwidth of Er-doped-fiber amplifiers, one could construct a similar device that operates near the 1310-nm zero-dispersion wavelength of standard telecommunication fiber.

Intensity-dependent phase-matching effects on four-wave mixing in optical fibers

A new phase-matching factor is derived for four-wave mixing (FWM) that includes the effects of self-phase and cross-phase modulation in optical fibers. Theoretical results predict that the wavelength of peak FWM efficiency shifts away from the fiber zero-dispersion wavelength and indicate that the conventional phase-matching factor may induce significant errors in FWM calculations. Experiments are presented to verify the new phase-matching factor and the related theoretical results. The measured results agree well with those predicted by the new phase-matching factor.

High-nonlinearity fiber optical parametric amplifier with periodic dispersion compensation

Theory shows that the maximum gain and bandwidth of one-pump fiber optical parametric amplifiers made from high-nonlinearity fiber, operated with a pump wavelength /spl lambda//sub p/ far from the fiber zero-dispersion wavelength /spl lambda//sub 0/ can greatly be improved by periodic dispersion compensation. We have performed experiments and obtained good agreement with theory: for /spl lambda//sub p/=1542 and /spl lambda//sub 0/=1591 nm, we have increased the bandwidth from 7 to 28 nm, and the maximum gain from 15 to 20 dB, by splicing three pieces of standard fiber at regular intervals in a 40-m long nonlinear fiber.

Scale of WDM transport network using different types of fibers

This paper describes a statistical calculation method for transmission limits taking into consideration dispersion-shifted fiber (DSF) zero-dispersion wavelength deviation for wavelength division multiplexing (WDM) systems employing unequal channel spacing. For example, the upper limit of fiber input power achieving a bit error rate (BER) less than 10/sup -12/ shows a 3 dB improvement when the standard deviation is increased from 1 to 8 nm when the transmission distance with a 80 km repeater spacing is 640 km. Furthermore, the network scales employing 1.55 /spl mu/m DSF, nondispersion-shifted fiber (N-DSF) and conventional single-mode fiber (SMF) are shown. Finally, a method for estimating the transmission limit for a receiver with different sensitivity, different node architecture, and different bit rates is described.

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.

Stability of bound states near the zero-dispersion wavelength in optical fibers

The propagation of weakly nonlinear pulses near the zero-dispersion wavelength (ZDW) in optical fibers is governed by a modified nonlinear Schr\"odinger (NLS) equation with a third-order-derivative dispersive term. This equation is known to admit steady, multihump bound states that would require less peak power to launch than an ordinary NLS soliton pulse of comparable duration and with carrier wavelength in the anomalous dispersion regime. Here, the stability of the two-hump bound state for which third-order dispersion is most significant is examined. Linear stability analysis indicates the presence of a mild instability with ${O(10}^{\ensuremath{-}2})$ growth rate. Numerical solutions of the modified NLS equation, however, reveal that, under certain conditions, nonlinearity has a stabilizing effect, permitting two-hump pulses to propagate for long distances without collapsing. Depending on the type of perturbation, a perturbed bound state evolves to a neighboring state with carrier frequency shifted either towards or away from the ZDW. The evolution of more general pulse profiles near the ZDW is also considered and the effect of fiber loss is discussed.

Dispersive wave generation in a Cr 4+:Forsterite femtosecond soliton-like laser

The operating characteristics of a self-mode-locked Cr 4+:forsterite soliton-like laser are reported. It is shown that a dispersive wave is generated synchronously with the pulse and that the spectral position of this wave relative to the emitted pulse is in qualitative and quantitative accordance with the predictions of the theory of nonlinear pulse propagation in the neighborhood of the zero-dispersion wavelength in fibers and with measurements such as second-harmonic generation spectrum, interferometric autocorrelation, in situ measurements of group-velocity dispersion (GVD) and third-order dispersion (TOD).

Accurate Measurements of the Zero-Dispersion Wavelength in Optical Fibers.

We have developed a frequency-domain phase shift system for measuring the zero-dispersion wavelength and the dispersion slope of single-mode optical fibers. A differential phase shift method and nonlinear four-wave mixing technique were also investigated. The frequency-domain phase shift method is used to produce Standard Reference Materials that have their zero-dispersion wavelengths characterized with an expanded uncertainty (k = 2) of ± 0.060 nm.