Amos Agmon

Coherent Transmission Direct Detection MIMO Over Short-Range Optical Interconnects and Passive Optical Networks

Building on a recently introduced quadratic multiple-input multiple-output (Q-MIMO) channel model making use of quadratic forms instead of linear channel matrices, we explore diverse signaling formats over the Q-MIMO channel in the frequency flat regime, highlighting the unique characteristics of optical multimode fiber (MMF) systems versus their wireless counterparts. In particular, we treat multiple-input single-output multimode fiber systems, comparing them with single-input single-output MMF systems and obtaining insight into the possibility of efficiently coupling the output of an MMF into a single-mode fiber. We further treat vector amplitude modulation over MMF MIMO and study the receiver zero-forcing (ZF) technique for MMF MIMO transmission, deriving its performance and comparing with a recently introduced ZF beamforming technique based on preceding at the transmitter, which is shown to be superior to receiver ZF.

OFDM/WDM PON with laserless, colorless 1 Gb/s ONUs based on Si-PIC and slow IC

We introduce a next-generation long-reach access optical network (35 dB loss budget +2 dB margin) delivering up to 40G/40G per passive 1:256 optical distribution network, supporting symmetrical 1 Gb/s rates per home user or up to 40 Gb/s for business users (e.g., enterprises, antenna sites). The proposed system is based on a novel spectrally efficient orthogonal frequency division multiplexing/wavelength division multiplexing OFDM/WDM architecture symmetrically using 16-QAM OFDM polarization diversity in both the downstream and upstream in order to serve low-cost energy-efficient symmetric 1 Gb/s optical network units (ONUs), which are self-coherent, laserless, colorless, and tunable-filter-free. Each ONU comprises a standard semiconductor optical amplifier (SOA), a silicon-based photonic integrated circuit (PIC), and mixed-signal electronic integrated circuits (ICs) performing the signal processing at a relatively slow rate as compared with the overall passive optical network (PON) throughput: digital to analog converters (DACs) and analog to digital converters (ADCs) at 417 MS/s for the home user ONUs.

Broadcast MIMO over multimode optical interconnects by modal beamforming

We introduce broadcast MIMO communication systems over multimode optical fibers or waveguides. Based on BeamForming (BF) at the transmitter, decoupled virtual subchannels are provided to multiple uncoordinated conventional direct detection receivers. This optical technique, extending Zero-Forcing BF wireless MIMO techniques to quadratic detection, is applicable to photonic interconnects, e.g. short-reach point-to-(multi)point transmission over MMF, up to rates of 100 Gb/s for distances up to 100 m.

Doubling direct-detection data rate by polarization multiplexing of 16-QAM without active polarization control

We introduce and simulate a technique enabling to utilize the polarization dimension in direct-detection optical transmission, supporting polarization multiplexing (POL-MUX) over direct-detection (DD) methods previously demonstrated for a single polarization such as direct-detection OFDM. POL-MUX is currently precluded in self-coherent DD with remotely transmitted pilot, as signal x pilot components may randomly fade out. We propose POL-MUX transmission of advanced modulation formats, such as 16-QAM and higher, by means of a novel low-complexity photonic integrated optical front-end and adaptive 3x2 MIMO DSP. The principle of operation is as follows: an additional X x Y cross-polarizations signal is generated, providing three projections onto an over-complete frame of three dependent vectors. This enables to resiliently reconstruct the received state of polarization even when the remotely transmitted pilot fades along one of the received polarization axes.

Direct Detection and Coherent Optical Time-Domain Reflectometry With Golay Complementary Codes

We extend the Golay coded Optical Time Domain Reflectometry OTDR technique for the first time from direct-detection to coherent OTDR, investigating the unique issues arising in the coherent setting regarding signal processing operations and efficient real-time implementation of the DSP in practical coherent OTDR receivers and the resulting OTDR performance. We also derive detailed signal flow block diagrams for direct-detection and coherent OTDRs and use an intuitive analogy between spatial speckle and temporal coherent fading noise to guide the selection of OTDR system parameters. We present extensive simulations of the OTDR signal and noise flow accounting for all major effects including the optical source coherence and the backscatter random fading.

Ultra-Dense, Single-Wavelength DFT-Spread OFDMA PON With Laserless 1.2 Gb/s ONU Ready for Silicon Photonics Integration

We introduce an ultra-dense network architecture designed for silicon photonics at the optical network unit (ONU). This network relies on only 3.333 GSa/s and 417 MSa/s converters at the OLT and ONU, respectively, and offers up to 12 Gbit/s of symmetric traffic in a single 12.5-GHz optical channel. Multiple access and lowest processing speeds at the ONU are enabled by choosing 10 DFT-spread OFDM subbands. We demonstrate this FDMA network architecture in a proof-of-principle experiment with up to eight 300-MBd 16QAM subbands offering a bidirectional data rate of 9.6 Gb/s. Real-time signal processing is realized for downstream transmission. Finally, we shortly address future improvements of this network architecture by employing integrated silicon photonics and analog signal processing to enable fine FDM for next-generation access networks.

Polarization Beamforming PON Doubling Bidirectional Throughput

A low-complexity polarization multiplexed Passive Optical Network (PON) architecture based on Multiple Input Multiple Output (MIMO) polarization beamforming is experimentally demonstrated, achieving twice the throughput for both downstream and upstream transmissions. In addition, a novel dynamic power allocation scheme further improves the loss budget by up to ~1.8 dB in the downstream direction.

Ultra-dense, single-wavelength DFT-spread OFDM PON with laserless 1 Gb/s ONU at only 300 MBd per spectral group

We demonstrate an FDMA network with up to eight 300 MBd 16QAM subcarriers offering bidirectional 9.6 Gbit/s within a single 12.5 GHz channel. OLT and ONU operate at only 3.2 GSa/s and 400 MSa/s, respectively. Real-time signal processing is realized for downstream transmission.

Flexible real-time transmitter at 10 Gbit/s for SCFDMA PONs focusing on low-cost ONUs

We demonstrate, to the best of our knowledge, the first real-time single-carrier frequency division multiple access transmitter designed to be used in photonic communication networks. It is capable of providing 10 Gbit/s net bitrate at 3.125 GHz slot bandwidth, providing data to nine quasi-Nyquist spectral groups. The transmitter is designed with respect to logic efficiency and a fine user grid allowing the operation of narrow bandwidth, low-cost optical network units. Moreover, it offers runtime flexibility, an efficient 96-point discrete Fourier transform and a multiplier-free differential phase encoder. The article concludes with a presentation of the transmitters hardware setup and an evaluation of its performance in the case of direct electrical AWG-ONU Rx interconnection and the optical back-to-back case.