Mario Martinelli

Coherent-to-incoherent light conversion for optical correlators

The authors present a novel coherent-to amplified spontaneous emission (ASE) converter based on SOAs cross-gain modulation (XGM) in a counterpropagating configuration. Experimental characterizations of the ASE converter with bit-error rate (BER) measurements at 2.5 and 5 Gb/s are shown. The device capabilities are exploited in a delay lines optical recognizer at 2.5 Gb/s. Recognition is based on a coherent-to-incoherent light conversion followed by a fiber array correlation filter. Experimental evidence here reported shows performance improvement in comparison with a scheme which adopts a standard telecom source.

Double Rayleigh scattering noise in lumped and distributed Raman amplifiers

An improved analytical expression of the multiple path interference (MPI) induced by double Rayleigh scattered signal in fiber Raman amplifiers (FRAs), valid both for lumped and distributed FRAs, is derived with a small signal model. The expression is validated both by comparison with an exact solution and by MPI measurements on four different lumped and distributed Raman amplifiers.

Raman-generated pump impact on optical parametric amplification

Continuous-wave (CW) Raman-generated pump impact on a fiber optical parametric amplifier (OPA) is analyzed. Different noise contributions associated to the pump are experimentally and theoretically evaluated. Gain and noise figure of the amplifier are presented and commented for different OPA configurations. By tightly filtering the CW Raman-generated pump an OPA noise figure approaching the 3 dB limit is achieved.

SOA based all-optical threshold

Summary form only given.The aim of this communication is to present an all-optical threshold device based on cross-gain modulation (XGM) in SOAs. The simple scheme we are proposing employs two semiconductor optical amplifiers (SOA) optical inverters in a feedback configuration, leading to an all-optical circuit which operates both as threshold and comparator. Analysis of the device operation and further experimentations are presented and discussed.

Two-stage Sagnac demultiplexer

Cascading a semiconductor optical amplifier (SOA)-based Sagnac interferometer with a second Sagnac stage allows significant improvement in the overall demultiplexer performance. A theoretical analysis and simulations show that the exploitation of a two-stage architecture results in a demultiplexing window sharpness and time compression. Eye-diagram and Q-factor experimental characterization at 2.5 Gb/s of the demultiplexer is presented, showing a 25% compression in time of the two-stage switching window and a 4.7 Q-factor improvement.

Differential Kerr-induced XPM in dispersion shifted fiber for wavelength conversion

Summary form only given. Kerr induced Cross Phase Modulation (XPM) in optical fiber is one of the effects able to provide wavelength conversion at very high bit-rate. The extensive use of this effect has been prevented by the low value of the nonlinear refractive index of standard optical fiber. Large amounts of fiber are necessary to obtain suitable phase modulation, and thus classical Kerr-based interferometric converters are extremely sensitive to acoustical and thermal noise. The aim of this work is to present a wavelength conversion experiment which exploits Kerr-induced birefringence in a standard Dispersion Shifted fiber in a Kerr shutter configuration. The IM drive beam at /spl lambda//sub drive/ amplified and linearly polarized, is fed into the nonlinear path-a Dispersion Shifted fiber coil-together with the CW probe at /spl lambda//sub probe/. This Kerr shutter wavelength converter takes advantage of the low Group Velocity Dispersion of the used nonlinear fiber (DS) in the third low loss window.

Telecommunication fiber OPA analysis, project, and characterization

Extremely high is nowadays researchers interest towards amplification techniques alternative to Erbium Doped Fiber Amplifiers (EDFA); driving force is the exploitation of new and larger fiber optic communication bandwidths. While EDFA gain relies on population inversion in an active material and thus amplification bandwidth is directly related to the doping ion energy levels, well known effects such as Raman and third order nonlinear susceptibility in optical fiber allow amplification not subject to this constraint. In optical parametric amplification, in particular, bandwidth shape and spectral collocation are determined by the choice of pump wavelength and power. Thus almost every spectral region can be reached provided that proper pump is available. We present a detailed analysis of optical parametric amplification in standard communication fiber, discussing different operation regime according to pump wavelength placement with respect to fiber zero dispersion wavelength. In particular attention is paid to the optical parametric amplifier gain bandwidth and saturation. We evidence that a key OPA project parameter is the relative phase between interacting waves, i.e., pump, signal and idler. This parameter not only allows comprehension of gain dynamics in the amplifier, but also can be controlled by engineering the nonlinear medium to improve OPA performances. Experimental verifications are also presented to validate the proposed analysis.

Analysis of a SOA-based all-optical reshaper

We present the analysis of reshaping capabilities of an all- optical threshold circuit. The device is based on SOAs XGM with two amplifiers in a feedback configuration. Simulations and experimentations of the threshold behavior are proposed and commented.

Amplified recirculating circuits for pseudo-continuous wave generation

An analysis of amplified recirculating structures for producing a pseudo-continuous wave, PCW, signal is presented. Experimentations with amplification provided by EDFA and SOA are shown. Both the hold-on function and the switch-off function are analyzed. The comparison between structures with different amplifiers shows better duration performances for EDFAs, but faster all-optical operation capabilities for SOAs.