Lucia Marazzi

Evidence of Raman-induced polarization pulling

The interest towards passive control of the light polarization through nonlinear effects has been stimulated by recent works: in particular a polarization pulling effect has been obtained by means of stimulated Brillouin scattering. Here we investigate the condition for obtaining polarization pulling by exploiting the stimulated Raman scattering, which is most suitable for optical communications thanks to its large gain bandwidth. The role of the polarization-dependent Raman amplification and of the random fiber birefringence is clarified by theoretical considerations and numerical simulations starting from the vector theory of the Raman effect in optical fiber. Experiments carried out with a 1571-nm signal and high-power 1486-nm pump evidence the Raman-induced polarization pulling.

Experimental demonstration of nonlinearity and dispersion compensation in an embedded link by optical phase conjugation

We report in this letter, the experimental demonstration of simultaneous dispersion and nonlinearity compensation in an embedded link characterized by strongly asymmetrical power profiles. This result is obtained by using a highly efficient optical phase conjugator based on a periodically poled lithium-niobate waveguide, combined with two small dispersion-compensating elements properly inserted in the link.

Polarization in Retracing Circuits for WDM-PON

Reflective semiconductor optical amplifier (RSOA)-based network-embedded self-tuning solutions for colorless optical network unit in wavelength-division-multiplexed passive optical network architecture suffer the device polarization-dependent gain (PDG). The Faraday-mirror-based topology proposed in the literature for low PDG RSOA is not suitable for high PDG RSOA. A polarization retracing circuit is proposed and discussed to comply with the high PDG RSOA. The polarization evolution is theoretically and experimentally analyzed in the presence of a high PDG RSOA comparing three cases: standard topology with standard mirror, the retracing circuit proposed in the literature with a Faraday rotator mirror (FRM), and the proposed retracing circuit, which includes both an FRM and a Faraday rotator.

Reflective-SOA Fiber Cavity Laser as Directly Modulated WDM-PON Colorless Transmitter

Reflective semiconductor optical amplifier (RSOA) fiber cavity lasers are attractive colorless, self-seeded, self-tuning, and directly modulatable sources for passive optical networks (PONs). They comprise of an RSOA in the optical network unit as the active element, a distribution fiber as the laser cavity, a waveguide grating router, and a common reflective mirror with the latter two positioned at the remote node. In this paper, we introduce a model and perform simulations to elucidate the recently discovered successful operation of this new PON source. The results are in agreement with experiments; the formation of a narrow laser spectrum with a relatively constant output power is seen despite a relatively broad passband window of the waveguide grating router. We further study mode competition and mode partition noise. It is shown that proper chromatic dispersion management can overcome mode partition noise limitations. The quality of the RSOA fiber cavity laser does not degrade when being directly modulated and as a result these highly multimode lasers offer an economic way to transport Gbit/s upstream data over kilometers of fiber in a wavelength division multiplexing-PON.

Measurement of PMD tolerance in 40-Gb/s polarization-multiplexed RZ-DQPSK

We experimentally investigate the first-order polarization-mode dispersion (PMD) tolerance of two polarization-multiplexed (POLMUX) RZ-DQPSK signals at overall 40 Gb/s. The polarization demultiplexing is enabled by an automatic endless polarization stabilizer. Time-interleaving the two orthogonally polarized RZ-DQPSK signals minimizes the crosstalk due to the non-ideal polarization stabilization, while it represents the worstcase for the PMD-induced crosstalk. Bit-error rate measurements are performed both in back-to-back and after 25-km standard single-mode fiber. The PMD tolerance is evaluated as a function of the instantaneous differential group delay, introduced by a first-order PMD emulator. 40-Gb/s POLMUX RZ-DQPSK is more sensitive to PMD than single-polarization 20-Gb/s DQPSK, while it is more PMD-tolerant than 40-Gb/s NRZ-OOK. Besides, its chromatic dispersion robustness is similar to the single-polarization 20-Gb/s DQPSK. The combination of POLMUX and DQPSK is therefore very promising in view of transmission systems at high bit-rate.

10-Gb/s Operation of a Colorless Self-Seeded Transmitter Over More Than 70 km of SSMF

Operation of a network-embedded colorless self-tuning transmitter for wavelength division multiplexing (WDM) networks is experimentally demonstrated at 10-Gb/s data rate. Colorless operation is achieved by self-seeding an O-band reflective semiconductor optical amplifier (RSOA) with the feedback signal reflected at the remote node WDM multiplexer filter. In particular, the transmitter exploits a 2-Faraday rotators configuration to ensure polarization insensitive operation and allowing for the exploitation of high gain O-band RSOAs, which present a very high polarization dependent gain. Two different multiplexers and various lengths of drop fibers constituted the network-embedded transmitters. Transmission up to 72 km of standard single mode fiber has been demonstrated at 10 Gb/s, confirming the absence of chromatic dispersion penalties as expected from the choice of the O-band operation.

Stable 100-Gb/s POLMUX-DQPSK Transmission With Automatic Polarization Stabilization

The reliability of 100-Gb/s polarization-multiplexed return-to-zero differential quadrature phase-shift keying transmission is demonstrated exploiting direct detection and automatic polarization stabilization. We experimentally verified a 2-dB chromatic dispersion tolerance of 100 ps/nm. Long-term stability has also been assessed by sampling the bit-error rate every 3 min over a continuous period of 8 h. Measurements are performed both in back-to-back and after 8.8 km uncompensated standard single-mode fiber, in the presence of a polarization scrambler.

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.

Influence of pump parameters on two-pump optical parametric amplification

An analysis of two-pump optical parametric amplifiers is proposed in order to evidence strategies to project and develop flat two-pump fiber parametric amplifiers (2P-OPAs). Amplifier gain profile is evaluated through a model that takes into account the four-wave mixing process with pump depletion. Disturbing influence of degenerate three-wave mixing processes is separately addressed. Through the analysis, important 2P-OPA project guidelines are obtained. Theoretical forecasts are confirmed by experimental measurements on different 2P-OPAs, realized by changing power and spectral allocations of the two pumps, obtained by Raman amplification.