O Oded Raz

Nanophotonic Devices for Optical Interconnect

We review recent progress in nanophotonic devices for compact optical interconnect networks. We focus on microdisk-laser-based transmitters and discuss improved design and advanced functionality including all-optical wavelength conversion and flip-flops. Next we discuss the fabrication uniformity of the passive routing circuits and their thermal tuning. Finally, we discuss the performance of a wavelength selective detector.

Silicon Photonic Integrated Mode Multiplexer and Demultiplexer

A novel passive integrated optical circuit for mode-multiplexing and demultiplexing six channels, LP01 and LP11 modes in a few-moded fiber, is designed and tested. A push-pull solution is proposed and demonstrated to excite the LP11 modes with a high extinction ratio. The circuit can outperform present bulk-optics solutions through its compactness and stability, and it has the potential advantages of high coupling efficiency and excellent mode crosstalk suppression.

Implementation of photonic true time delay using high-order-mode dispersion compensating fibers

We demonstrate the advantageous use of highly dispersive (>450 ps/nm/spl middot/km), high-order-mode (HOM) fiber modules for true time delay applications. Along with their low insertion loss, very low phase ripple (root mean square <0.3/spl deg/ over 0-20 GHz), and high immunity to nonlinear effects, the high dispersion values facilitate the construction of devices with relatively short fibers, resulting in improved tolerance of the radio frequency delay to thermal changes. The implications of multiple path interference effects in HOM modules are also studied and shown to be very small.

160-Gb/s All-Optical Packet Switching Over a 110-km Field Installed Optical Fiber Link

Demonstration of all-optical packet switching at 160 Gb/s over a total of 110-km field installed optical fiber link is reported. The packet switch architecture is based solely on photonic circuits: an optical filter as label processor, an all-optical flip-flop as memory element and an ultrafast wavelength converter as router. Both flip-flop and wavelength converter uses semiconductor optical amplifiers which allows for photonic integration. The switch operates at low power levels and shows potential scalability. Error-free operation is shown without forward error correction technology.

Submicrosecond Scan-Angle Switching Photonic Beamformer With Flat RF Response in the C and X Bands

A wideband (>10 GHz) beamformer, based on a photonic true-time-delay, with submicrosecond scan-angle switching is reported. The smooth microwave transmission (ripples <0.5 dB and <3deg) and superb uniformity among the elements (<0.1 dB and <0.5deg) are then used for the processing of 1 GHz-wide linear frequency modulation (LFM) signals in both the C and X bands with excellent performance. This performance is also maintained under dynamic operation, where a fast tunable laser is employed to provide <300 ns wavelength-controlled angle scanning. Based on these characteristics, an optimized architecture, where a photonic beamformer feeds a series of classical subarrays, can offer high performance in both the time and spatial domains for large, wideband phased-array antennas, with wide scan angles.

320 Gbit/s wavelength conversion using four-wave mixing in quantum-dot semiconductor optical amplifiers

In this study, we demonstrate error-free all-optical wavelength conversion of ultrahigh-speed intensity modulated signals by means of four-wave mixing in a quantum-dot semiconductor optical amplifier. Error-free performance at a bit rate of 320 Gbit/s is measured for the extracted 40 Gbit/s tributaries with a 3.4 dB average power penalty to the original signal.

Scalable Optical Packet Switches for Multiple Data Formats and Data Rates Packets

We demonstrate an optical packet switch (OPS) subsystem employing in-band labeling to allow for transparent routing of packets with multiple data formats and data bit rates. Packets employing in-band labels can be processed without the need to reconfigure the label processor and the switch when changing data format and bit-rate. The label processor is based on asynchronous optical signal processing in combination with a simple electronic combinatory network. This makes the label processor capable to process a large number of labels with low latency time (<3 ns) without complicated and power-hungry high-speed packet clock recovery and serializer/deserializer circuits. Experimental results show error-free operation of 1 × 64 OPS subsystem for 160-Gb/s return-to-zero on-off keying and 120-Gb/s nonreturn-to-zero differential phase-shift keying multiwavelength packets.

Analysis of a true time delay photonic beamformer for transmission of a linear frequency-modulated waveform

A generalized conversion matrix (GCM) and numerical analysis are used to study the distortions suffered by a linear frequency-modulated radio frequency (RF) pulse while propagating through photonic links to be used in wideband phased arrays. The analysis shows the effects of dispersion of all orders, coherent crosstalk and nonlinearity of the optical components on the RF pulse, and the high performance needed to achieve acceptable RF performance of the temporal (impulse) response. The effects of the electrical-to-optical (E/O) and optical-to-electrical (O/E) conversions are also considered. Using the GCM, the optical amplitude and phase fluctuations are converted into their RF counterparts, thereby reducing the optical problem into the well-understood RF domain. A photonic wavelength-controlled true delay device is experimentally shown to achieve good RF performance over a 4-GHz bandwidth, with predicted sidelobe levels below 30 dB.

Wavelength-controlled photonic true time delay for wide-band applications

A radio frequency subcarrier modulated wavelength-controlled dense wavelength-division-multiplexing-based photonic true time delay module, with very low phase (/spl plusmn/4/spl deg/) and magnitude (/spl plusmn/0.5 dB) ripples over a bandwidth of several gigahertz, is demonstrated to achieve wide-band linear frequency modulation transmission (600 MHz) with -37-dB sidelobe suppression and signal-to-noise exceeding 80 dB/MHz.

Wideband Antenna Patterns and Impulse Response of Broadband RF Phased Arrays With RF and Photonic Beamforming

The general expression for a monochromatic antenna pattern is extended to a two dimensional function with dependence on both space and time. Expressions for the wideband antenna pattern in space and the impulse response in time are developed. The effects of random errors in the spatial domain and errors common to all elements with fluctuations in the frequency domain are analyzed. Examples are given, including RF beamformers and elements in finite arrays, but with an emphasis on a photonic beamformer, which shows improved performance relative to its RF counterparts in both the spatial and time domains