Maxim Greenberg

Multimode add-drop multiplexing by adiabatic linearly tapered coupling.

Multimode multiplexing can potentially replace WDM for implementing multichannel short reach interconnects. Multiple optical modes can thus be exploited as the channels for transferring optical data, where each mode represents an independent data channel. The basic building block of the system is a Mode Add/Drop which can be implemented based on adiabatic power transfer. We propose a new scheme for realization of such adiabatic mode add drop with a predefined coupling profile, and demonstrate it by employing a linearly decreasing coupling coefficient along the propagation length. Realization using Silicon-On- Insulator (SOI) platform is discussed - which offers the possibility of direct integration of the optoelectronic circuitry with the Si processor.

Irreversible coupling by use of dissipative optics.

The time reversibility of optical propagation impedes the definite performance of many optical devices, such as couplers, polarization converters, etc. We suggest a novel concept in which we use media with loss and gain, thus breaking the time-reversal characteristics, to achieve a unidirectional optical mode interference and coupling, which is a desirable feature for light-wave circuits. Using a matched periodic modulation of both the index of refraction and loss (gain) of the medium, we implement a spatially single sideband perturbation, which breaks the symmetry to allow only a unidirectional energy transfer from mode m to mode n of the optical structure. We elaborate on this phenomenon in coupling between two modes of a multimode optical waveguide.

Unidirectional complex gratings assisted couplers

We present a novel concept which enables the realization of unidirectional and irreversible grating assisted couplers by using gain-loss modulated medium to eliminate the reversibility. Employing a matched periodic modulation of both refractive index and loss (gain) we achieve a unidirectional energy transfer between the modes of the coupler which translates to light transmission from one waveguide to another while disabling the inverse transmission. The importance of self coupling coefficients is explored as well and a feasible implementation, where the real and imaginary perturbations are implemented in different waveguides is presented.

Data Parallelization by Optical MIMO Transmission Over Multimode Fiber With Intermodal Coupling

Data parallelization by means of optical multiple-input multiple-output (MIMO) transmission over dispersive multimode fiber (MMF), with a high degree of modal coupling but not accounting for intermodal dispersion, is investigated by developing an analytical model for direct detection of MMF MIMO frequency-flat transmission with mutually incoherent sources. The MIMO channel performance is derived in terms of a new formulation of a channel matrix for modal group powers accounting, for the first time, for modal coupling. For fixed aggregate signaling rate and power budget, for uncoded bit streams, increasing the number of output detectors improves the bit error ratio (BER)-similarly to wireless MIMO. However, contrary to wireless MIMO, increasing the number of input ports actually yields a BER penalty, which is traceable to the quadratic nature of photodetection. We finally establish the feasibility of enhancing the aggregate bit rate using multiple inputs in the case that the individual single-input-single-output channels are band limited, e.g., given optical data sources each at 2 Gb/s, it is possible to attain a 12-Gb/s signaling rate over several hundreds of meters of MMF at 10-10 BER, by utilizing six such inputs into the MIMO system, while incurring just a small average power penalty of approximately 2 dB/channel. The current model assumes strong intermodal coupling and neglects ISI influence over distances of up to hundreds of meters at gigabit rates, providing a first step in the optical MIMO analysis. On the other hand, similar scenario is practically met for shorter distances (up to 100 m) for the novel types of plastic optical fibers.

Multimode Fiber as Random Code Generator— Application to Massively Parallel MIMO Transmission

We propose a novel multiple-input multiple-output (MIMO) scheme over multimode fiber, acting as a distributed random code generator fed by spatial codes, using silicon photonics in the transmitter and maximum-likelihood (ML) electronic detection in the receiver, providing an alternative to coarse wavelength division multiplexing (CWDM) for implementation of ultrahigh speed parallel transmission over short-range optical interconnects. The optical MIMO system utilizes mutually coherent transmission and conventional direct detection with one-bit quantization, facilitating cost-effective application to 100 Gb/s links over < 50 m.

Data Parallelization by Optical MIMO Transmission Over Multi-mode Fiber with Inter-modal Coupling

System performance is derived for multiple-inputs-multiple-outputs signaling over MMF accounting for inter-modal coupling; the aggregate bitrate is increased by utilizing multiple inputs on a single physical channel. Alternatively, bit-error-rate is improved by using multiple outputs

Performance of High-Bitrate Multiple-Output Links Over Multimode Fiber With Intermodal Dispersion

We investigate novel transmission schemes over multimode fiber with multiple output detectors, providing more efficient utilization of the available spatial-temporal degrees of freedom of the system by combining coherent phase shift keying transmission with direct detection. We evaluate the statistics of the electrical charge generated by each detector, and its dependence on factors such as detector type, dimension and offset position. In the frequency-selective case, we reveal that temporal degrees of freedom resulting from nonoverlapping time pulses modify the decision variable statistics. We apply the ensuing model to propose a novel phase-modulated single input multiple output (SIMO) multimode fiber transmission system employing multiple detectors and multiple input multiple output (MIMO) space-time postdetection signal processing in order to mitigate the ISI stemming from intermodal dispersion.

Efficient hierarchical list decoder for massive optical MIMO transmission.

We propose a novel MIMO scheme over multimode fiber, acting as a distributed random code generator fed by spatial codes, using silicon photonics in the transmitter and efficient list-based hierarchical submaximum-likelihood electronic detection in the receiver, providing an alternative to CWDM for implementation of ultra-high speed parallel transmission over short-range optical interconnects.

Efficient hierarchical list decoder for 100 Gigabit Ethernet optical MIMO Transmission

We propose a novel MIMO scheme over MMF, acting as a distributed random-code generator fed by spatial codes, using silicon photonics in the transmitter and efficient list-based hierarchical sub-optimal electronic detection in the receiver.

Massively parallel transmission over multimode fiber applied to 100 Gigabit Ethernet with random-coding

We propose a novel MIMO multimode fiber technique realizing for the first time random coding motivated by Shanons noisy channel theorem, using silicon photonics in the transmitter and maximum likelihood electronic detection in the receiver.