Amir Rashidinejad

Photonic Radio-Frequency Arbitrary Waveform Generation With Maximal Time-Bandwidth Product Capability

We present an innovative photonic strategy to generate arbitrary microwave and millimeter-wave signals with maximal time-bandwidth product capability and broadly tunable center frequency. The proposed approach incorporates high-resolution pulse shaping, optical interferometry, and the concept of frequency-to-time mapping in order to enable independent control over the temporal amplitude, temporal phase, and center frequency of the generated waveforms. Numerical simulation and experimental results validate that the time-bandwidth product of these pulses is equal to the upper bound set by the number of independent pulse shaper control elements, extending to more than twice that of conventional frequency-to-time mapping techniques. We thus demonstrate a record photonic arbitrary waveform generation time-bandwidth product of ~589. Also, a length 15 Costas sequence realization is implemented to further portray the potentials of this technique. Detailed analysis of the repeatability and stability of these waveforms as well as higher order dispersion compensation is provided.

Recent Advances in Programmable Photonic-Assisted Ultrabroadband Radio-Frequency Arbitrary Waveform Generation

This paper reviews recent advances in photonic-assisted radio-frequency arbitrary waveform generation (RF-AWG), with emphasis on programmable ultrabroadband microwave and millimeter-wave waveforms. The key enabling components in these techniques are programmable optical pulse shaping, frequency-to-time mapping via dispersive propagation, and high-speed photodetection. The main advantages and challenges of several different photonic RF-AWG schemes are discussed. We further review some proof-of-concept demonstrations of ultrabroadband RF-AWG applications, including high-resolution ranging and ultrabroadband non-line-of-sight channel compensation. Finally, we present recent progress toward RF-AWG with increased time aperture and time-bandwidth product.

Ultrabroadband radio-frequency arbitrary waveform generation with high-speed phase and amplitude modulation capability.

We introduce a novel photonic-assisted ultrabroadband radio-frequency arbitrary waveform generation setup capable of high-speed phase and amplitude modulation of the individual arbitrary waveforms. The waveform generator is based on an optical interferometer, within which a high-resolution optical pulse shaper and integrated optic phase and intensity modulators are placed, followed by frequency-to-time mapping. The phase and amplitude of each ultrabroadband waveform within the generated sequence can be continuously tuned by adjusting the driving voltages applied to the phase and intensity modulator pair, hence overcoming the slow update speed of conventional spatial light modulator-based pulse shapers. Moreover, this data modulation is completely independent from and does not interfere with RF waveform design. Programmable ultrabroadband RF sequences, spanning more than 4.7 octaves from 2 to 52 GHz, are modulated with real-time data in up to 16 level, M-ary phase-shift keying and quadrature amplitude modulation formats.

Low-Loss Ultrawideband Programmable RF Photonic Phase Filter for Spread Spectrum Pulse Compression

We demonstrate a low-loss, ultrawideband (UWB), programmable radio frequency photonic phase filter utilizing a broadband optical frequency comb, interferometric pulse shaping configuration, and a balanced photodetector for spread spectrum pulse compression. We present UWB linear frequency-chirped pulse compression with bandwidths exceeding 7 GHz. The filter insertion loss for these experiments can be as low as 0.5 dB. In addition, the bandwidth and chirp rate of the phase filter are programmable. To further illustrate the programmability of the proposed filter, we report pulse compression experiments for UWB Costas sequences with bandwidth over 6 GHz. Finally, we perform a spread-spectrum jamming-resistant pulse compression experiment with the chirp filter, where a processing gain of ~ 17.3 dB, proportional to the time-bandwidth product of the filter, enables the recovery of a transmitted UWB signal in the presence of jamming.

Photonic Generation and Wireless Transmission of W-band Arbitrary Waveforms with High Time-Bandwidth Products

We report photonic radio-frequency arbitrary waveform generation in the W-band, enabled through optical pulse shaping and a near-ballistic uni-traveling-carrier photodiode. Example waveforms spanning 75-110GHz with long time apertures are generated and measured after wireless propagation.

Selected advances in photonic ultrabroadband radio-frequency arbitrary waveform generation

Selected research at Purdue University on photonic generation of ultrabroadband radio-frequency arbitrary waveforms is discussed; with an emphasis on increasing the attainable time-bandwidth product, both in terms of bandwidth and time aperture. Experimental results of such waveforms are presented and also applied for measurement and control of wireless propagation in highly dispersive indoor environments.

Achieving the upper bound time-bandwidth product for radio-frequency arbitrary waveform generation

In this paper we present an innovative photonic strategy to generate arbitrary microwave and millimeter-wave electrical pulses with the maximum possible time-bandwidth product and broadly tunable center frequency. The proposed approach incorporates fine-resolution pulse shaping, optical interferometry and the concept of frequency-to-time mapping in order to enable independent control over the temporal amplitude, temporal phase and center frequency of the generated radio-frequency waveforms. Also, the time-bandwidth product of these pulses extends to more than twice that of conventional frequency-to-time mapping techniques. Basic theoretical analysis is carried out and validated by numerical simulations as well as experiments. A length 15 Costas frequency-hopping sequence realization is implemented to further portray the potentials of this technique.

Virtual Optical Buffers: A Novel Interpretation of OCDMA in Packet Switch Networks

Among all proposed structures for optical networks, the optical packet switching (OPS) scheme, due to its practical implementation of IPs in an optical configuration and the consequent advantages, is a prizeworthy candidate for being employed in metropolitan area network and local area network communication levels. One of the few problems frequently met using the OPS structure in the fiber-optics realm is the lack of optical buffers, thus deteriorating the systems flexibility and quality of service. For example, optical label switching networks that have been developed recently based on the generalized multiprotocol label switching protocol, profoundly suffer from this setback which is considered as a great hurdle in their evolution. In this paper, we first introduce the input and output buffer switching models while deducing their blocking probability formulations. Then, by utilizing codes in the OPS structure, we closely examine the potential of code and/or wavelength switching in packet switching networks and also determine their blocking probability. Due to close similarities between different scenarios, we present the prospect of virtual optical buffers using codes, which have close performance to input and output buffers in sight of block probability. The most significant distinction in using virtual buffers is the fact that due to their substantial nature, they happen to exhibit some error probability. However, on account of the advantageous features of codes, the simulated and formulated error probability for both coherent and noncoherent optical code division multiple access (OCDMA), such as Spectrally phase encoded OCDMA and optical orthogonal codes, using virtual buffers, tends to be negligible. Two main code and wavelength switching schemes are also brought to attention in this work, the intelligent and random methods. These scenarios demonstrate an even greater behavioral performance to that of the mere code switching scenario, leading into a more reliable adaptation of virtual buffers. In addition, simulations results happen to provide clear verifications to our analytical approach.

Photonically-enabled phase shift keying of 50 GHz bandwidth radio-frequency arbitrary waveforms

We experimentally realize phase shift keying of ultrabroadband radio-frequency arbitrary waveforms. BPSK, QPSK and 16-PSK modulation are demonstrated for 50-GHz-bandwidth spread spectrum RF waveforms.

Low-loss RF photonic pulse compression filter based on an optical frequency comb

We demonstrate an RF photonic pulse compression filter using a broadband optical frequency comb and balanced detection. This scheme provides a large RF bandwidth of >7GHz, low loss of <;1dB, and programmability. A jamming experiment is conducted to highlight the advantages of the filter.