Fabrizio Gambini

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.

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.

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.

Design and Implementation of an Integrated Reconfigurable Silicon Photonics Switch Matrix in IRIS Project

This paper aims to present the design and the achieved results on a CMOS electronic and photonic integrated device for low cost, low power, transparent, mass-manufacturable optical switching. An unprecedented number of integrated photonic components (more than 1000), each individually electronically controlled, allows for the realization of a transponder aggregator device which interconnects up to eight transponders to a four direction colorless-directionless-contentionless ROADM. Each direction supports 12 200-GHz spaced wavelengths, which can be independently added or dropped from the network. An electronic ASIC, 3-D integrated on top of the photonic chip, controls the switch fabrics to allow a complete and microsecond fast reconfigurability.

Ring Versus Bus: A Theoretical and Experimental Comparison of Photonic Integrated NoC

Silicon photonics enables the fabrication of photonic integrated circuits with high bandwidth density, making it suitable for computercom applications. In multicore computing systems, the communications between cores and memory can be supported by optical networks-on-chip (NoC) realized with photonic integrated circuits (PIC). While different optical NoC topologies have been proposed in the past, only few NoC were fabricated and tested. This paper aims at comparing the performance of two PIC NoC with a bus and a ring topology. First, a framework is presented for passing from the theoretical analysis of silicon photonics basic building blocks like waveguides and microrings, to the PIC design and to the NoC performance derivation, using the scattering matrix method. Based on this framework, the two NoC topologies are simulated, designed, fabricated in silicon photonics, and experimentally characterized for comparison. Spectral performance validates the theoretical model with minor deviations due to the fabrication inaccuracies and limitations. Bit error rate performance at 10 Gb/s demonstrates the capability of simultaneous transmissions in both topologies with limited or negligible crosstalk. Moreover, ring NoC is shown to slightly outperform the bus NoC thanks to the filtering properties of the central microring.

Bidirectional Transmission in an Optical Network on Chip With Bus and Ring Topologies

In photonic integrated networks on chip (NoCs), microrings are commonly used for adding or dropping a single optical signal to be switched in the NoC. This paper demonstrates the feasibility of adding or dropping two optical signals at the same wavelength in the same microring of NoCs with bus and ring topology. More specifically, the same microring can be used to support simultaneous bidirectional transmissions of two signals to be coupled in the NoC topology, leading to two different configurations, called shared source-microring and shared destination-microring. Spectral characterization shows good agreement between simulations and measurements taken on silicon-based integrated NoC. Bit-error-rate (BER) measurements indicate that the shared sourcemicroring configuration performs better, achieving a penalty as low as 1.5 dB for a BER of 10-9 at 10 Gb/s in the bus NoC. A higher penalty in the ring NoC for both configurations is due to higher crosstalk in the interconnecting ring.

Demonstration of a photonic integrated network-on-chip with multi microrings

A multi-microring network-on-chip for datacom applications is demonstrated on a silicon-on-insulator platform. Measurements on the photonic integrated circuit are in good agreement with simulations, achieving a 3dB-bandwidth of 39 GHz and a worst-case crosstalk of -12dB.

Ring versus bus: A BER comparison of photonic integrated networks-on-chip

Silicon-photonics bus and ring networks-on-chip are evaluated in terms of transfer function and bit error rates at 10Gb/s, demonstrating that the ring architecture can be effectively used with physical layer performance similar to the bus.

A Compact Silicon Coherent Receiver Without Waveguide Crossing

A monolithically integrated silicon coherent receiver based on a novel scheme with a crossing-free 900 hybrid optical coupler and two balanced germanium photodetectors is reported. The integrated receiver is compact (footprint is 0.8 × 1.0 mm2), and it is demonstrated by working with single-polarization 56-Gb/s quadrature phase-shift keying (QPSK) and 80-Gb/s 16-quadrature amplitude modulation (16-QAM) signals. In particular, QPSK transmission that is back-to-back at 28 Gbaud shows a bit-error rate (BER) below 10-4 for an optical signal-to-noise ratio (OSNR) lower than 17 dB, whereas 16QAM at 20 Gbaud shows a BER not better than 3*10-2 because of the nonideal behavior of the device. Reasons for the performance limitations are discussed.

Orbital Angular Momentum Generation with Ultra-Compact Bragg-Assisted Silicon Microrings

A silicon microring resonator with an embedded Bragg grating for orbital angular momentum (OAM) generation is designed and experimentally demonstrated. The device consists of a 3.9 μm-radius ring resonator with cylindrical silica holes along the central path and exploits the radially polarized component of the propagating electric field in the resonators strip waveguide, enabling both the bandwidth broadening and the emission efficiency improvement, while reducing the footprint. The experimental results show that the device achieves a 3dB bandwidth of 134 GHz and an efficiency up to 6.5 %. The interference patterns are measured for different OAM orders in which the number of spirals are clearly visible proving that the device can support different topological charges. Results are in good agreement with simulations.