All-optical high-speed temporal random pattern generation based on photonic time stretch

We propose a novel all-optical temporal random pattern generation scheme based on photonic time stretch involving cascaded Mach-Zehnder interferometers (MZIs) with different chirped spectral response. The overall spectral response represents a broadband random spectral pattern. Temporal random patterns can then be generated thanks to photonic time stretch which mirrors spectrum encoding to temporal waveform. Tuning of the generated temporal patterns is achieved using a rapidly tunable optical delay module in one of the MZIs

Data Compressed Photonic Time-Stretch Optical Coherence Tomography

Photonic time stretch enables real-time optical coherence tomography, but at the cost of extreme requirement for high-speed signal acquisition and massive data set. This work reports a data compressed real-time Fourier-domain optical coherence tomography based on photonics-assisted compressive sensing. Compression ratio of 66% is achieved

Compressive Sensing Detection of RF Signals by All-Optically Generated Binary Random Patterns

High-speed random bit sequences are crucially important in temporal compressive sensing applications. In this work, we propose a new all-optical binary random patterns generation method for compressive sensing, completely eliminating the use of high-speed electronic circuits. This approach uses photonic time stretched optical pulses as the optical carrier. Spectrum slicing using a tunable ring resonator produces a train of uniformly spaced optical pulses (bits) due to spectrum-to-time mapping in photonic time stretch. Two cascaded dispersive devices with particularly designed nonlinear dispersion profiles are employed to introduce random time delays among optical pulses, leading to a quasi-random binary sequence. The random sampling pulse sequence can be updated by changing the free-spectral range of the ring resonator. The proposed method is verified by numerical simulations. The photonic generated random pulse sequences are used in compressive sensing detection of high-frequency RF signals. In a proof-of-concept demonstration, one-tone and multi-tone microwave signals are successfully reconstructed from four-time compressed measurement data

Adaptive non-uniform photonic time stretch for blind RF signal detection with compressed time-bandwidth product

Photonic time stretch significantly extends the effective bandwidth of existing analog-to-digital convertors by slowing down the input high-speed RF signals. Non-uniform photonic time stretch further enables time bandwidth product reduction in RF signal detection by selectively stretching high-frequency features more. However, it requires the prior knowledge of spectral-temporal distribution of the input RF signal and has to reconfigure the time stretch filter for different RF input signals. Here we propose for the first time an adaptive non-uniform photonic time stretch method based on microwave photonics pre-stretching that achieves blind detection of high-speed RF signals with reduced time bandwidth product. Non-uniform photonic time stretch using both quadratic and cubic group delay response has been demonstrated and time bandwidth product compression ratios of 72% and 56% have been achieved respectively

Photonic compressive sensing enabled data efficient time stretch optical coherence tomography

Photonic time stretch (PTS) has enabled real time spectral domain optical coherence tomography (OCT). However, this method generates a torrent of massive data at GHz stream rate, which requires capturing as per Nyquist principle. If the OCT interferogram signal is sparse in Fourier domain, which is always true for samples with limited number of layers, it can be captured at lower (sub-Nyquist) acquisition rate as per compressive sensing method. In this work we report a data compressed PTS-OCT system based on photonic compressive sensing with 66% compression with low acquisition rate of 50MHz and measurement speed of 1.51MHz per depth profile. A new method has also been proposed to improve the system with all-optical random pattern generation, which completely avoids electronic bottleneck in traditional binary pseudorandom binary sequence (PRBS) generators

In-Fibre Diffraction Grating for Beam Steering Indoor Optical Wireless Communication

In-fibre diffraction based on 45° tilted fibre grating enables high-efficiency wavelength-controlled laser beam steering for indoor optical wireless communication with unique features of low-loss and seamless integration with existing fibre-to-home networks. In addition, ultrafast user localization (50 million scans per second) based on real-time wavelength monitoring is demonstrated

Optical Phase Shifting Fourier Transform Scanning for Bandwidth-Efficient Blind RF Spectrum Sensing

Avoiding high-speed electronics, optical time-stretch Fourier transform scanning for RF spectrum sensing is presented. Broadband RF frequency scanning is achieved by using a phase shifting Mach-Zehnder interferometer. GHz RF signals have been detected with only 50 MS/s sampling rate

Real-Time User Localisation in Beam Steered NIR Optical Wireless Communications

Near infrared (NIR) optical wireless communication provides a promising solution for point-to-point indoor high speed wireless data link. To cover a large area and several multiple users, wavelength-encoded laser beam steering has been demonstrated in previous research work. One remaining challenge in beam steered optical wireless system is real-time user localization. In this paper, ultrafast complete user localization at update rate of 10 MHz based on instantaneous optical wavelength detection and chirped pulse correlation has been demonstrated. Both angular position and absolute distance of each user have been accurately detected

High throughput photonic time stretch optical coherence tomography with data compression

Photonic time stretch enables real time high throughput optical coherence tomography (OCT), but with massive data volume being a real challenge. In this paper, data compression in high throughput optical time stretch OCT has been explored and experimentally demonstrated. This is made possible by exploiting spectral sparsity of encoded optical pulse spectrum using compressive sensing (CS) approach. Both randomization and integration have been implemented in the optical domain avoiding an electronic bottleneck. A data compression ratio of 66% has been achieved in high throughput OCT measurements with 1.51 MHz axial scan rate using greatly reduced data sampling rate of 50 MS/s. Potential to improve compression ratio has been exploited. In addition, using a dual pulse integration method, capability of improving frequency measurement resolution in the proposed system has been demonstrated. A number of optimization algorithms for the reconstruction of the frequency-domain OCT signals have been compared in terms of reconstruction accuracy and efficiency. Our results show that the L1 Magic implementation of the primal-dual interior point method offers the best compromise between accuracy and reconstruction time of the time-stretch OCT signal tested

High throughput photonic time stretch optical coherence tomography with data compression

Photonic time stretch enables real time high throughput optical coherence tomography (OCT), but with massive data volume being a real challenge. In this paper, data compression in high throughput optical time stretch OCT has been explored and experimentally demonstrated. This is made possible by exploiting spectral sparsity of encoded optical pulse spectrum using compressive sensing (CS) approach. Both randomization and integration have been implemented in the optical domain avoiding an electronic bottleneck. A data compression ratio of 66% has been achieved in high throughput OCT measurements with 1.51 MHz axial scan rate using greatly reduced data sampling rate of 50 MS/s. Potential to improve compression ratio has been exploited. In addition, using a dual pulse integration method, capability of improving frequency measurement resolution in the proposed system has been demonstrated. A number of optimization algorithms for the reconstruction of the frequency-domain OCT signals have been compared in terms of reconstruction accuracy and efficiency. Our results show that the L1 Magic implementation of the primal-dual interior point method offers the best compromise between accuracy and reconstruction time of the time-stretch OCT signal tested