S. Faralli

Impact of double Rayleigh scattering noise in distributed higher order Raman pumping schemes

We analyze the equivalent optical noise figure (NF) performances and double Rayleigh-scattering-induced noise characteristics of distributed Raman amplifiers based on higher order pumping schemes. We confirm that higher order counterpumping configurations improve the amplifier equivalent NF but also increase multipath interference noise, inducing system penalties at high ON-OFF Raman gain. A Q-factor analysis allows a quantitative evaluation of the real benefits provided by higher order pumping schemes.

A 100-Gb/s noncoherent silicon receiver for PDM-DBPSK/DQPSK signals

An integrated noncoherent silicon receiver for demodulation of 100-Gb/s polarization-division multiplexed differential quadrature phase-shift keying and polarization-division multiplexed differential binary phase-shift keying signals is demonstrated. The receiver consists of a 2D surface grating coupler, four Mach-Zehnder delay interferometers and four germanium balanced photodetectors.

High-Performance Raman-Based Distributed Fiber-Optic Sensing Under a Loop Scheme Using Anti-Stokes Light Only

A distributed fiber-optic temperature sensor technique inherently allowing for system calibration, compensating time-dependent variations of the fiber losses as well as local external perturbations, is proposed using a loop-scheme together with Raman anti-Stokes-only measurement. A temperature resolution enhancement with respect to a standard loop configuration is shown by experiments, providing a robust and reliable high-performance sensing technique for long sensing ranges.

Bidirectional higher order cascaded Raman amplification benefits for 10-Gb/s WDM unrepeated transmission systems

Benefits provided by higher order bidirectional Raman pumping schemes in 10-Gb/s unrepeated wavelength-division-multiplexing transmission systems are experimentally quantified in terms of BER performances at 10 Gb/s. By keeping under control double-Rayleigh-scattering-noise-induced transmission penalties, which can degrade system performance at very high ON-OFF Raman gain, as well as nonlinear propagation effects such as Brillouin scattering, self- and cross-phase modulations, four-wave-mixing, and Raman-induced crosstalks, we show a total unrepeated system reach enhancement up to 3.5 dB with respect to first-order bidirectional pumping. As confirmed by theory, the maximum reach enhancement is mainly limited by pump-to-signal relative intensity noise transfer induced by higher order copumping.

Impact of Loss Variations on Double-Ended Distributed Temperature Sensors Based on Raman Anti-Stokes Signal Only

We present a theoretical and experimental analysis of the sensing capabilities of Raman-based distributed temperature optical fiber sensor (RDTS) systems using only the anti-Stokes (AS) component in loop configuration. In particular, the effects of time- and wavelength-dependent losses on the sensor performance are thoroughly investigated under different experimental conditions. As expected from the developed theory, experimental results demonstrate that using the loop AS-light only approach in RDTS systems can correct the impact of local and wavelength-dependent losses on the final temperature measurements, with the simple use of an internal calibration fiber spool at a known temperature value. Signal-to-noise ratio and temperature resolution analyses of the AS-only RDTS point out an improved temperature resolution in comparison to standard RDTS systems in loop configuration.

A Cost-Effective Distributed Acoustic Sensor Using a Commercial Off-the-Shelf DFB Laser and Direct Detection Phase-OTDR

We propose and experimentally demonstrate the use of cyclic pulse coding for enhanced performance in distributed acoustic sensing based on a phase-sensitive optical time-domain reflectometry (φ-OTDR) using direct detection. First, we present a theoretical analysis showing that to make cyclic pulse coding effective in φ-OTDR, the laser linewidth and stability must be optimized to simultaneously guarantee intrapulse coherence and interpulse incoherence. We then confirm that commercial off-the-shelf distributed feedback (DFB) lasers can satisfy these conditions, providing coding gain consistent with theoretical predictions. By externally modulating such lasers with cyclic pulse coding, we demonstrate a distributed acoustic sensor capable of measuring vibrations of up to 500 Hz over 5 km of standard single-mode fiber with 5-m spatial resolution with ~9-dB signal-to-noise ratio (SNR) improvement compared with the single-pulse equivalent. We also show that the proposed solution offers sensing performances that are comparable to similar sensors employing highly coherent and stabilized external cavity lasers and a single-pulse φ-OTDR.

BER evaluation of a low-crosstalk silicon integrated multi-microring network-on-chip

The operation of an integrated silicon-photonics multi-microring network-on-chip (NoC) is experimentally demonstrated in terms of transmission spectra and bit error rates at 10 Gb/s. The integrated NoC consists of 8 thermally tuned microrings coupled to a central ring. The switching functionalities are tested with concurrent transmissions at both the same and different wavelengths. Experimental results validate the analytical model based on the transfer matrix method. BER measurements show performance up to 10(-9) at 10 Gb/s with limited crosstalk and penalty (below 0.5 dB) induced by an interfering transmission.

An InP Monolithically Integrated Unicast and Multicast Wavelength Converter

We experimentally demonstrate a novel Indium Phosphide monolithically integrated optical circuit for all-optical wavelength conversion. The circuit exploits two cascaded cross gain modulation (XGM) interactions in semiconductor optical amplifiers. In a first XGM stage, the input signal and a continuous wave light at the desired output wavelength generate a wavelength converted yet not ideal copy of the input signal, whereas, in the second XGM stage, the quality of the wavelength converted signal is significantly improved because of the cross gain compression effect. We report 10 Gb/s wavelength conversion performance for both the unicast (single output wavelength) and the multicast (multiple output wavelengths) conversion. Experimental results confirm the effectiveness of the present photonic integrated circuit in both cases, showing only a moderate bit error rate power penalty.

High-Speed Silicon Electro-Optic Microring Modulator for Optical Interconnects

A silicon microring modulator for ON-OFF keying intensity modulation is presented and experimentally characterized. Modulation operation is based on carrier depletion effect in a p-n junction. The resonance wavelength shift is measured for bias voltages in the range between 0 and -7 V and modulation is demonstrated by employing electrical signals with data rates of 25 and 30 Gb/s and peak-to-peak voltage of 3.75 V. Performance in terms of bit error rate as a function of the optical signal-to-noise ratio for point-to-point transmission over 10 km of single mode fiber at both the data rates is experimentally evaluated, manifesting to be suitable for short- and medium-reach optical interconnects applications.

A wavelength-preserving photonic integrated regenerator for NRZ and RZ signals

This paper presents a novel Indium Phosphide based photonic integrated circuit (PIC) for all-optical regeneration of both nonreturn-to-zero (NRZ) and return-to-zero (RZ) on-off-keying (OOK) signals. The PIC exploits cross gain compression in two semiconductor optical amplifiers to simultaneously obtain a wavelength-preserved and reshaped copy, and a wavelength-converted yet inverted copy of the input signal. Regeneration of 10 Gb/s signals on multiple wavelengths is demonstrated, showing a Q-factor improvement from 1.5 to 4 for NRZ-OOK signals and from 2.3 to 3.6 for RZ-OOK signals, and a BER improvement up to 1.5 decades.