arXiv subjects

Jianping Chen

Publications and source records attributed to Jianping Chen.

At least 19 recordsLinked to original sources

arXiv2024

Narrowband parallel coherent LiDAR with frequency interleaving

The high demand for 3D imaging in intelligent robotics is motivating the advances of coherent LiDARs towards high performances with low complexity/cost. However, the current coherent LiDARs suffer from the tight coupling between the high ranging-imaging performance and the high complexity/cost. Herein, we propose a narrowband parallel coherent LiDAR with frequency-interleaving architecture. The LiDAR architecture utilizes narrowband signals for ranging, and interleaves multi-channel sparse and narrowband signals in frequency domain at the receiving end to significantly reduce the required bandwidth and the number of detection branches, facilitating massive parallelization with low system complexity/cost. In experiments, a ranging precision of 0.49 mm that approaches the shot noise limit, and a power sensitivity of -95 dBm (~9 photons) are achieved. Parallel 3D imaging with an equivalent imaging rate of 10 Mpixel/s and a 2 cm ranging precision is also demonstrated using only two 150 MHz receiving branches. With these desirable properties, this new LiDAR opens an avenue for the LiDAR ecosystem.

physics.optics↗

arXiv2023

Experimental observation of Kerr-Raman solitons in a normal-dispersion FP resonator

Different from the Kerr effect,stimulated Raman scattering (SRS) is a delayed response to molecular vibrations in materials. In microcavities, when driven in an anomalous group velocity dispersion (GVD) regime, SRS typically leads to self-frequency shift of solitons and generation of breather solitons which have been verified both theoretically and experimentally. However, when driven in a normal GVD regime, recent theoretical work predicts that SRS can cause the locking of switching waves (SWs) and thus support bright moving localized structures (LSs), which we term as Kerr-Raman solitons (KRSs). Limited by the design of suitable experimental parameters, experimental observation of the KRSs is not achieved yet. Here, we provide numerical investigation, and to our knowledge, the first experimental observation of these SRS enabled KRSs in a fiber Fabry-Perot (FP) resonator with ultra-low normal GVD. Such Kerr-Raman solitons exhibit localized temporal features with strong oscillations at ~13 THz local frequency on the top of a flat-top pulse. The corresponding spectrum is a low-noise and broadband Kerr comb with typical platicon-like spectrum in the center and two Raman Stokes and anti-Stokes peaks located near 13 THz away from the center. With such SRS enabled broadband Kerr comb, we have achieved a KRS spectrum with a repetition rate of ~3.68 GHz and a -40 dB spectral width of 260 nm. The corresponding comb tooth count is >9000, covering the S+C+L telecommunication bands. Moreover, the formation process of such KRSs is also revealed, and it is found that the GVD plays a key role in its generation. Our work will help to advance the study of the dynamics of optical frequency combs under the influence of SRS, as well as providing a broadband coherent mode-locked optical source for wide applications.

physics.optics↗

arXiv2022

Free-space point-to-multiplepoint optical frequency transfer with lens assisted integrated beam steering

We report on the realization of high-performance silica integrated two-dimensional lens assisted beam-steering (LABS) arrays along with the first-of-their-kind point-to-multiplepoint optical frequency transfer. {The LABS equips with $N$ antennas} and has the capability to produce arbitrary number of output beams with different output angles with the simple control complexity. We demonstrate that the LABS has 16 scanning angles, which can support {the access capability for the maximum of simultaneous 16 user nodes.} The coaxial configuration for transmitting and receiving the light as a monolithic transceiver allows us to reduce the out-of-loop phase noise significantly. Finally, the LABS-based non-blocking point-to-multiplepoint in-door free-space optical frequency transfer links with 24 m and 50 m free-space links are shown. After being compensated for the free-space link up to 50 m, the fractional frequency instability of $4.5\times10^{-17}$ and $7.7\times10^{-20}$ at the averaging time of 1 s and 20,000 s, respectively, can be achieved. The present work proves the potential application of the 2D LABS in free-space optical time-frequency transfer and provides a guidance for developing a chip-scale optical time-frequency transfer system.

physics.ins-det↗

arXiv2022

Multiple-access relay stations for long-haul fiber-optic radio frequency transfer

We report on the realization of a long-haul radio frequency (RF) transfer scheme by using multiple-access relay stations (MARSs). The proposed scheme with independent link noise compensation for each fiber sub-link effectively solves the limitation of compensation bandwidth for long-haul transfer. The MARS can have the capability to share the same modulated optical signal for the front and rear fiber sub-links, simplifying the configuration at the repeater station and enabling the transfer system to have the multiple-access capability. At the same time, we for the first time theoretically model the effect of the MARS position on the fractional frequency instability of the fiber-optic RF transfer, demonstrating that the MARS position has little effect on system's performance when the ratio of the front and rear fiber sub-links is around $1:1$. We experimentally demonstrate a 1 GHz signal transfer by using one MARS connecting 260 and 280 km fiber links with the fractional frequency instabilities of less than $5.9\times10^{-14}$ at 1 s and $8.5\times10^{-17}$ at 10,000 s at the remote site and of $5.6\times10^{-14}$ and $6.6\times10^{-17}$ at the integration times of 1 s and 10,000 s at the MARS. The proposed scalable technique can arbitrarily add the same MARSs in the fiber link, which has great potential in realizing ultra-long-haul RF transfer.

eess.SP↗

arXiv2021

Characterization of the frequency response of channel-interleaved photonic ADCs based on the optical time-division demultiplexer

We characterize the frequency response of channel-interleaved photonic analog-to-digital converters (CI-PADCs) theoretically and experimentally. The CI-PADC is composed of a photonic frontend for photonic sampling and an electronic backend for quantization. The photonic frontend includes a photonic sampling pulse generator for directly high-speed sampling and an optical time-division demultiplexer (OTDM) for channel demultiplexing. It is found that the frequency response of the CI-PADC is influenced by both the photonic sampling pulses and the OTDM, of which the combined impact can be characterized through demultiplexed pulse trains. First, the frequency response can be divided into multiple frequency intervals and the range of the frequency interval equals the repetition rate of demultiplexed pulse trains. Second, the analog bandwidth of the CI-PADC is determined by the optical spectral bandwidth of demultiplexed pulse trains which is broadened in the OTDM. Further, the effect of the OTDM is essential for enlarging the analog bandwidth of the CI-PADC employing the photonic sampling pulses with a limited optical spectral bandwidth.

eess.SP↗

arXiv2021

Erbium-doped lithium niobate thin film waveguide amplifier with 16 dB internal net gain

Erbium-doped lithium niobate on insulator (Er:LNOI) has attracted enormous interest as it provides gain and enables integrated amplifiers and lasers on the lithium niobate on insulator (LNOI) platform. We demonstrate a highly efficient waveguide amplifier on Er:LNOI. The 2.58-cm long amplifier can achieve 27.94 dB signal enhancement, 16.0 dB internal net gain (6.20 dB/cm), -8.84 dBm saturation power, 4.59 dB/mW power conversion efficiency, and 4.49 dB noise figure at 1531.6 nm. Besides, thorough investigation on the pumping wavelength, pumping scheme, output power and noise figure have been performed to provide a comprehensive understanding on this novel waveguide amplifier. This work will benefit the development of a powerful gain platform and can pave the way for a fully integrated photonic system on LNOI platform.

physics.optics↗

arXiv2021

A marine radioisotope gamma-ray spectrum analysis method based on Monte Carlo simulation and MLP neural network

The monitoring of Cs-137 in seawater using scintillation detector relies on the spectrum analysis method to extract the Cs-137 concentration. And when in poor statistic situation, the calculation result of the traditional net peak area (NPA) method has a large uncertainty. We present a machine learning based method to better analyze the gamma-ray spectrum with low Cs-137 concentration. We apply multilayer perceptron (MLP) to analyze the 662 keV full energy peak of Cs-137 in the seawater spectrum. And the MLP can be trained with a few measured background spectrums by combining the simulated Cs-137 signal with measured background spectrums. Thus, it can save the time of preparing and measuring the standard samples for generating the training dataset. To validate the MLP-based method, we use Geant4 and background gamma-ray spectrums measured by a seaborne monitoring device to generate an independent test dataset to test the result by our method and the traditional NPA method. We find that the MLP-based method achieves a root mean squared error of 0.159, 2.3 times lower than that of the traditional net peak area method, indicating the MLP-based method improves the precision of Cs-137 concentration calculation

physics.ins-det↗

arXiv2021

A blind zone-suppressed hybrid beam steering for solid-state Lidar

We demonstrate a blind zone-suppressed and flash-emitting solid-state Lidar based on lens-assisted beam steering (LABS) technology. As a proof-of-concept demonstration, with a design of subwavelength-gap one-dimensional (1D) long-emitter array and multi-wavelength flash beam emitting, the device was measured to have 5%-blind zone suppression, 0.06°/point-deflection step and 4.2 microsecond-scanning speed. In time-of-flight (TOF) ranging experiments, Lidar systems have field of view of 11.3°* 8.1° (normal device) or 0.9°*8.1° (blind-zone suppressed device), far-field number of resolved points of 192 and a detection distance of 10 m. This work demonstrates the possibility that a new integrated beam-steering technology can be implemented in a Lidar without sacrificing other performance.

physics.app-ph↗

arXiv2021

A single-frequency single-resonator laser on erbium-doped lithium niobate on insulator

Erbium-doped lithium niobate on insulator (Er:LNOI) is a promising platform for photonic integrated circuits as it adds gain to the LNOI system and enables on-chip lasers and amplifiers. A challenge for Er:LNOI laser is to increase its output power while maintaining single-frequency and single (-transverse)-mode operation. In this work, we demonstrate that single-frequency and single-mode operation can be achieved even in a single multi-mode Er:LNOI microring by introducing mode-dependent loss and gain competition. In a single microring with a free spectral range of 192 GHz, we have achieved single-mode lasing with an output power of 2.1 microwatt, a side-mode suppression of 35.5 dB, and a linewidth of 1.27 MHz.

physics.optics↗

arXiv2021

Fiber radio frequency transfer using bidirectional frequency division multiplexing dissemination

We report on the realization of a novel fiber-optic radio frequency (RF) transfer scheme with the bidirectional frequency division multiplexing (FDM) dissemination technique. Here, the proper bidirectional frequency map used in the forward and backward directions for suppressing the backscattering noise and ensuring the symmetry of the bidirectional transfer RF signals within one telecommunication channel. We experimentally demonstrated a 0.9 GHz signal transfer over a 120 km optical link with the relative frequency stabilities of 2.2E-14 at 1 s and 4.6E-17 at 20,000 s. The implementation of phase noise compensation at the remote site has the capability to perform RF transfer over a branching fiber network with the proposed technique as needed by large-scale scientific experiments.

physics.ins-det↗

arXiv2021

Single-frequency integrated laser on erbium-doped lithium niobate on insulator

The erbium-doped Lithium niobate on insulator (Er:LNOI) platform has great promise in the application of telecommunication, microwave photonics, and quantum photonics due to its excellent electro-optic, piezo-electric, nonlinear nature as well as the gain characteristics in the telecommunication C-band. Here, we report a single-frequency Er:LNOI integrated laser based on dual-cavity structure. Facilitated by the Vernier effect and gain competition, the single-frequency laser can operate stably at 1531-nm wavelength with a 1484-nm pump laser. The output laser has a power of 0.31 uW, a linewidth of 1.2 MHz, and a side mode suppression ratio (SMSR) of 31 dB. Our work allows the direct integration of this laser source with existing LNOI components and paves the way for a fully integrated LNOI system.

physics.optics↗

arXiv2021

Branching optical frequency transfer with enhanced post automatic phase noise cancellation

We present a technique for coherence transfer of laser light through a branching fiber link, where the optical phase noise induced by environmental perturbations via the fiber link is passively compensated by remote users without the requirements of any active servo components. At each remote site, an acousto-optic modulator (AOM) is simultaneously taken as a frequency distinguisher for distinguishing its unique frequency from other sites' and as an optical actuator for compensating the phase noise coming from the optical fiber. With this configuration, we incorporate a long outside loop path consisting of a fiber-pigtailed AOM into the loop, enabling the significant reduction of the outside loop phase noise in the passive way. To further address the residual out-of-loop phase noise coming from the interferometer and the two-way optical frequency comparison setup, we design a low-noise active temperature stabilization system. Measurements with a back-to-back system show that the stability in our stabilization system is $2\times10^{-16}$ at 1 s, reaching $2\times10^{-20}$ after 10,000 s. Adopting these techniques, we demonstrate transfer of a laser light through a branching fiber network with 50 km and 145 km two fiber links. After being compensated for the 145 km fiber link, the relative frequency instability is $3.4\times10^{-15}$ at the 1 s averaging time and scales down to $3.7\times10^{-19}$ at the 10,000 s averaging time. This proposed technique is suitable for the simultaneous transfer of an optical signal to a number of independent users within a local area.

physics.ins-det↗

arXiv2021

Passive Optical Phase Stabilization on a Ring Fiber Network

Optical frequency transfer provides the means for high-fidelity frequency transfer across thousands of kilometers. A critical step in the further developing optical frequency transfer is its capability to transfer a high spectral purity feature from ultrastable lasers or optical clocks to any remote locations and, at the same time, its adaptability to incorporate the optical frequency transfer technique into any existing communication networks with different topologies. Here we for the first time report a technique that delivers optical-frequency signals to multiple independent remote hubs along a ring optical-fiber network with passive phase stabilization. The technique automatically corrects optical-fiber length fluctuations of arbitrary hubs along the loop by mixing and shifting optical signals. Without the help of an active phase tracker and a compensator, it could significantly mitigate some technical problems such as the limited compensation speed and phase recovery time, the phase jitter contamination caused by the servo bump in conventional phase noise cancellation. Moreover, by transmitting optical signals along both directions using the same optical source, it can improve the signal-to-noise ratio at each hub. This technique maintains the same delay-limited phase noise correction capability as in conventional techniques and, furthermore, improves the phase jitter by a factor of 3, opening a way to a broad distribution of an ultrastable frequency reference with high spectral purity and enabling a wide range of applications beyond metrology over a ring fiber network with the naturally impressive reliability and scalability.

physics.ins-det↗

arXiv2021

All-passive multiple-place optical phase noise cancellation

We report on the realization of delivering coherent optical frequency to multiple places based on passive phase noise cancellation over a bus topology fiber network. This technique mitigates any active servo controller on the main fiber link and at arbitrary access places as opposed to the conventional technique, in which an active phase compensation circuit has to be adopted to stabilize the main fiber link. Although the residual fiber phase noise power spectral density (PSD) in the proposed technique turns out to be a factor of 7 higher than that of in the conventional multiple-access technique when the access place is close to the end of the fiber link, it could largely suppress the phase noise introduced by the servo bumps, improve the response speed and phase recovery time, and minimize hardware overhead in systems with many stations and connections without the need of the active servo circuits including phase discriminators and active compensators. The proposed technique could considerably simplify future efforts to make precise optical frequency signals available to many users, as required by some large-scale science experiments.

physics.ins-det↗

arXiv2020

Comparison of phase change process in Si-GST hybrid integrated waveguide and MMI devices

In the past decades, silicon photonic integrated circuits (PICs) have been considered as a promising approach to solve the bandwidth bottleneck in optical communications and interconnections. Despite significant advances, large-scale PICs still face a series of technical challenges, such as footprint, power consumption, and routing state storage, resulting from the active tuning methods used to control the optical waves. These challenges can be partially addressed by combining chalcogenide phase change materials (PCMs) such as Ge2Sb2Te5 (GST) with silicon photonics, especially applicable in switching applications due to the nonvolatile nature of the GST. Although GST phase transitions between amorphous and crystalline states actuated by optical and electrical pulses heating have been experimentally demonstrated, there is no direct comparison between them. We carried out simulations and experiments to systematically investigate the difference in the phase change process induced by optical and electrical pulses for two types of Si-GST hybrid waveguides. For the phase transition induced by optical pulses, the device has a clear advantage in terms of power consumption and operation speed. For the phase transition induced by electrical pulses, the device is suitable for large-scale integration because it does not require complex light routing. It helps us better understand the phase change process and push forward the further development of Si-GST hybrid integration platform, bringing in new potential applications.

physics.optics↗

arXiv2020

A silicon integrated microwave photonic beamformer

Optical beamforming networks (OBFNs) based on optical true time delay lines (OTTDLs) are well-known as the promising candidate to solve the bandwidth limitation of traditional electronic phased array antennas (PAAs) due to beam squinting. Here we report the first monolithic 1x8 microwave photonic beamformer based on switchable OTTDLs on the silicon-on-insulator platform. The chip consists of a modulator, an eight-channel OBFN, and 8 photodetectors, which includes hundreds of active and passive components in total. It has a wide operating bandwidth from 8 to 18 GHz, which is almost two orders larger than that of electronic PAAs. The beam can be steered to 31 distinguishable angles in the range of -75.51° to 75.64° based on the beam pattern calculation with the measured RF response. The response time for beam steering is 56 μs. These results represent a significant step towards the realization of integrated microwave photonic beamformers that can satisfy compact size and low power consumption requirements for the future radar and wireless communication systems.

physics.optics↗

arXiv2020

Optimizing Deep Learning Recommender Systems' Training On CPU Cluster Architectures

During the last two years, the goal of many researchers has been to squeeze the last bit of performance out of HPC system for AI tasks. Often this discussion is held in the context of how fast ResNet50 can be trained. Unfortunately, ResNet50 is no longer a representative workload in 2020. Thus, we focus on Recommender Systems which account for most of the AI cycles in cloud computing centers. More specifically, we focus on Facebook's DLRM benchmark. By enabling it to run on latest CPU hardware and software tailored for HPC, we are able to achieve more than two-orders of magnitude improvement in performance (110x) on a single socket compared to the reference CPU implementation, and high scaling efficiency up to 64 sockets, while fitting ultra-large datasets. This paper discusses the optimization techniques for the various operators in DLRM and which component of the systems are stressed by these different operators. The presented techniques are applicable to a broader set of DL workloads that pose the same scaling challenges/characteristics as DLRM.

cs.DC↗

arXiv2020

Fundamental Limitations of Rayleigh Backscattering Noise on Fiber-Based Multiple-Access Optical Frequency Transfer

While it has been shown that backscattering induced phase noise can be suppressed by adopting acoustic-optic-modulators (AOMs) at the local and remote sites to break the frequency symmetry in both directions. However, this issue can not be avoided for conventional fiber-optic multiple-access coherent optical phase dissemination in which the interference of the signal light with the Rayleigh backscattered light will probably destroy the coherence of the stabilized optical signal. We suppress the backscattering effect by locally breaking the frequency symmetry at the extraction point by inserting an additional AOM. Here, we theoretically analyze and experimentally demonstrate an add-drop one more AOM approach for suppressing the Rayleigh backscattering within the fiber link. Near-complete suppression of backscattering noise is experimentally confirmed through the measurement the elimination of a common interference term of the signal light and the Rayleigh backscattered light. The results demonstrate that the Rayleigh backscattering light has a limited effect compared to the residual delay-limited fiber phase noise on the system's performance. Our results also provide new evidence that it is possible to largely suppress Rayleigh and other backscattering noise within a long optical fiber link, where the accumulated phase noise could be large, by using frequency symmetry breaking at each access node to achieve robust multiple-access coherent optical phase propagation in spite of scatters or defects.

physics.ins-det↗