Walter Belardi

2R-regenerative all-optical switch based on a highly nonlinear holey fiber

We report the fabrication of a highly nonlinear holey fiber made from pure silica with an effective area of just ~2.8mu;m(2) at 1550 nm. We believe this to be the smallest effective area yet measured for a holey fiber at 1550 nm. We also report the operation of a 2R regenerative optical switch based on just 3.3 m of the fiber that is shown to have 30 times the nonlinear figure of merit of previous devices based on dispersion-shifted fiber.

Four-wave mixing based 10-Gb/s tunable wavelength conversion using a holey fiber with a high SBS threshold

We demonstrate a four-wave-mixing based wavelength converter using a 15-m highly nonlinear holey fiber (HF) with a high stimulated Brillouin scattering (SBS) threshold. Error-free efficient wavelength conversion of 10-Gb/s nonreturn-to-zero signal over a /spl sim/10-nm bandwidth is reliably achieved. Our 15-m HF has a nonlinearity coefficient /spl gamma//spl sim/70(/spl plusmn/10) W/sup -1//spl middot/km/sup -1/ and an SBS threshold of more than 130 mW. The high SBS threshold is achieved by applying structural variation to the HF along its length during the fabrication process. No modulational-instability-induced intensity noise on the converted signals is observed due to the normal dispersion of the HF.

Raman effects in a highly nonlinear holey fiber: amplification and modulation

We experimentally demonstrate that a short length of highly nonlinear holey fiber (HF) can be used for strong L(+) -band (1610-1640-nm) Raman amplification and ultrafast signal modulation. We use a pure silica HF with an effective area of just 2.85mum(2) at 1550 nm, which yields an effective nonlinearity ~15 times higher than in conventional silica dispersion-shifted fiber. Using a 75-m length of this fiber, we obtained internal Raman gains of more than 42 dB and a noise figure of ~6 dB under a forward single-pump scheme, and the Raman gain coefficient was experimentally estimated to be 7.6 chi 10(-14)m/W . Also, an 11-dB signal extinction ratio in a Raman-induced all-optical modulation experiment was achieved with the same fiber.

Soliton transmission and supercontinuum generation in holey fiber, using a diode pumped Ytterbium fiber source

We report linear dispersion compensation, soliton pulse formation, soliton compression, and ultra-broad supercontinuum generation in a holey fiber with anomalous dispersion at wavelengths above 800nm. The holey fiber was seeded with ultrashort pulses from a diode pumped, Ytterbium (Yb)-doped fiber source operating at 1.06 microm. The results highlight the compatibility of the rapidly developing holey fiber technology with short pulse Yb-doped fiber lasers for wide application.

A holey fiber-based nonlinear thresholding device for optical CDMA receiver performance enhancement

We demonstrate the use of an optical thresholder based on a short length of holey fiber to achieve enhanced code recognition quality in a 255-chip 320-Gchip/s superstructured fiber Bragg grating-based optical code-division multiple access code:decode system. The nonlinear thresholder is based on bandpass filtering of spectrally broadened components generated by self-phase modulation and assisted by the Raman effect in an 8.7 m length of highly nonlinear holey fiber. Error free penalty free system performance is obtained with complete recovery of the original input pulse shape.

Hollow antiresonant fibers with low bending loss

We first use numerical simulations to show that bending losses of hollow antiresonant fibers are a strong function of their geometrical structure. We then demonstrate this by fabricating a hollow antiresonant fiber which presents a bending loss as low as 0.25 dB/turn at a wavelength of 3.35 μm and a bend radius of 2.5 cm. This fiber has a relatively low attenuation (<200 dB/km) over 600 nm mid-infrared spectral range.

A tunable WDM wavelength converter based on cross-phase modulation effects in normal dispersion holey fiber

We demonstrate a tunable wavelength-division-multiplexing wavelength converter based on cross-phase modulation in just 5.8 m of highly nonlinear normal dispersion holey fiber (HF) and incorporating a precise compression-tuned apodized fiber-grating filter. We achieve both error-free and penalty-free 10-Gb/s wavelength conversion over a /spl sim/15-nm bandwidth. The short device length and correspondingly reduced pulse walkoff effect ensures a constant wavelength-converted signal pulsewidth across the full tuning range. The use of HF with normal dispersion eliminates the coherence-degradation related intensity noise previously observed in experiments employing anomalously dispersive HF.

Hollow antiresonant fibers with reduced attenuation

An improved design for hollow antiresonant fibers (HAFs) is presented. It consists of adding extra antiresonant glass elements within the air cladding region of an antiresonant hollow-core fiber. We use numerical simulations to compare fiber structures with and without the additional cladding elements in the near- and mid-IR regimes. We show that realizable fiber structures can provide greatly improved performance in terms of leakage and bending losses compared to previously reported antiresonant fibers. At mid-IR wavelengths, the adoption of this novel fiber design will lead to HAFs with reduced bending losses. In the near-IR, this design could lead to the fabrication of HAFs with very low attenuation.

Investigation of Brillouin effects in small-core holey optical fiber: lasing and scattering

We demonstrate for what is believed to be the first time a Brillouin laser based on a holey fiber (HF). Using a simple Fabry-Perot resonator scheme containing a 73.5-m-long highly nonlinear HF with an effective area of 2.85 microm(2) , we obtain a threshold of 125 mW and a slope efficiency of ~70% . Stimulated and spontaneous Brillouin scattering effects are investigated in the HF, and we show that the high lasing threshold is due mainly to reduction of the effective gain coefficient caused by structural nonuniformity along the fiber length.

Form-induced birefringence in elliptical hollow photonic crystal fiber with large mode area

We propose a novel type of photonic crystal fiber (PCF), including an elliptical hole in its solid core. We prove the feasibility of such a fiber and investigate both experimentally and theoretically the dependence of its group birefringence on the geometric hole parameters. We show, for the first time, that form-induced birefringence can be achieved in single mode PCFs with large mode area and suggest it as a possible route for the development of polarization maintaining PCF-based LMA fiber devices.