Telecom Components Research Articles

Agile manipulation of the time-frequency distribution of high-speed electromagnetic waves

Controlling the temporal evolution of an electromagnetic (EM) wave’s frequency components, the so-called time-frequency (TF) distribution, in a versatile and real-time fashion remains very challenging, especially at the high speeds (> GHz regime) required in contemporary communication, imaging, and sensing applications. We propose a general framework for manipulating the TF properties of high-speed EM waves. Specifically, the TF distribution is continuously mapped along the time domain through phase-only processing, enabling its user-defined manipulation via widely-available temporal modulation techniques. The time-mapping operations can then be inverted to reconstruct the TF-processed signal. Using off-the-shelf telecommunication components, we demonstrate arbitrary control of the TF distribution of EM waves over a full bandwidth approaching 100 GHz with nanosecond-scale programmability and MHz-level frequency resolution. We further demonstrate applications for mitigating rapidly changing frequency interference terms and the direct synthesis of fast waveforms with customized TF distributions. The reported method represents a significant advancement in TF processing of EM waves and it fulfills the stringent requirements for many modern and emerging applications.

Strategic cooperation of high tech companies of China and Russia

The sanctions imposed on the Russian economics in 2022 by a number of countries created an external shock for many industries in Russia with the strongest impact on the enterprises of high tech industries. At the same time, there is an emerging potential for cooperation between Russian and Chinese manufacturers which is forming new strategies of development of Russian high tech enterprises. In order to evaluate the prospects and trends of development of Chinese high tech industry in this context, the authors applied methods of economic analysis including the correlation analysis. Factors, determining potential of cooperation between Russia and China in this sphere, were systematized on the basis of the methodology of strategizing by Professor Vladimir L. Kvint.It has been stated that Chinese manufacturers are able to replace either partially or completely European and American suppliers in a number of high tech industries: innovative components and equipment for engineering, semiconductors and chips, telecommunications equipment and components. It has been discovered that the number of registered patents and the number of researchers involved in RD in China have a significant correlation with the growth of export of high tech products of China. Further growth will be able to ensure the expansion of technology and knowledge exports from China to Russia.Thus, it can be stated for sure that there are perspective industries and fields of Russia-China cooperation in high tech industry. The sphere of cooperation which can become the basis for the strategy of development of Russian high tech manufacturers is scientific and patent cooperation with Chinese organizations. The authors have also discovered limitations in this cooperation: there is a threat of imposing international sanctions on Chinese manufacturers; Chinese enterprises are working at a high level of workload in the context of the global economic recovery after the coronavirus pandemic; decrease of competitiveness of Russian high tech industry has a negative impact on the expected benefits from the cooperation between the countries. These strategic threats can be overcome with the help of a well-grounded foreign economic strategy developed by Russian and Chinese authorities.

Continuous entanglement distribution from an AlGaAs-on-insulator microcomb for quantum communications

Using an aluminum gallium arsenide microring resonator, we demonstrate a bright quantum optical microcomb with >300 nm (>40 THz) bandwidth and more than 20 sets of time–energy entangled modes, enabling spectral demultiplexing with simple, off-the-shelf commercial telecom components. We report high-rate continuous entanglement distribution for two sets of entangled-photon pair frequency modes exhibiting up to 20 GHz/mW2 pair generation rate. As an illustrative example of entanglement distribution, we perform a continuous-wave time-bin quantum key distribution protocol with 8 kbps sifted key rates while maintaining less than 10% error rate and sufficient two-photon visibility to ensure security of the channel. When the >20 frequency modes are multiplexed, we estimate >100 kbps entanglement-based key rates or the creation of a multi-user quantum communications network. The entire system requires less than 110 µW of on-chip optical power, demonstrating an efficient source of entangled frequency modes for quantum communications. As a proof of principle, a quantum key is distributed across 12 km of deployed fiber on the University of California Santa Barbara (UCSB) campus and used to encrypt a 21 kB image with <9% error.

Characterization of Quantum Frequency Processors

Frequency-bin qubits possess unique synergies with wavelength-multiplexed lightwave communications, suggesting valuable opportunities for quantum networking with the existing fiber-optic infrastructure. Although the coherent manipulation of frequency-bin states requires highly controllable multi-spectral-mode interference, the quantum frequency processor (QFP) provides a scalable path for gate synthesis leveraging standard telecom components. Here we summarize the state of the art in experimental QFP characterization. Distinguishing between physically motivated “open box” approaches that treat the QFP as a multiport interferometer, and “black box” approaches that view the QFP as a general quantum operation, we highlight the assumptions and results of multiple techniques, including quantum process tomography of a tunable beamsplitter—to our knowledge the first full process tomography of any frequency-bin operation. Our findings should inform future characterization efforts as the QFP increasingly moves beyond proof-of-principle tabletop demonstrations toward integrated devices and deployed quantum networking experiments.

Phase encoded quantum key distribution up to 380 km in standard telecom grade fiber enabled by baseline error optimization

Phase encoding in quantum key distribution (QKD) enables long-distance information-theoretic secure communication in optical fibers. We present a novel theoretical model characterizing errors from various sources in practical phase encoding-based QKD systems, namely the laser linewidth, detector dark counts, and channel dispersion. This model provides optimized optical pulse parameters and less distortion in pulses, which eliminates system imperfections and leads to a reduced quantum bit error rate (QBER) for practical QKD scenario. This analysis is applicable to various fiber-based phase and time encoding protocols. In particular, we implement this to a differential phase shift (DPS) QKD scheme operating at a 2.5 GHz clock, which produces a secure key rate of 193 bits/s at a fiber length of 265 km and an unprecedented QBER < 1% up to 225 km length with standard telecom components. We show that by adjusting the quantum efficiency and dark count rates of detectors, proposed system can establish secure keys up to 380 km distance using standard telecom grade fiber with a QBER of 1.48%. Moreover, the system is compatible with existing optical fiber networks and capable of establishing a secure key exchange between two cities 432 km apart using ultra-low-loss (ULL) specialty fiber.

Suppression of Fading Noise in Satellite-Mediated Continuous-Variable Quantum Key Distribution via Clusterization

The satellite-mediated continuous-variable quantum key distribution (CV-QKD) protocol, which relies on off-the-shelf telecommunication components, has the potential for a global quantum communication network with all-day operation. However, the transmittance fluctuation of satellite-mediated links leads to the arriving quantum state showing non-Gaussian property, introducing extra fading noise in security analysis and limiting the secret key rate of the protocol. Here, we consider the clusterization method for data post-processing to suppress the fading noise in both downlink and uplink scenarios, where the measurement data are divided into several clusters, and we perform security analysis separately. In particular, we set the optimal upper and lower bounds of each cluster in terms of the probability distribution of transmittance (PDT), while finding an optimal cluster number for the trade-off between fading noise and the composable finite-size effect. Numerical analysis shows that the proposed method can improve the composable finite-size rate when the fading noise is large enough, even with only two clusters. Moreover, a high-speed CV-QKD system with a higher frequency of signal preparation and detection can extend the proposed method to work in the case of lower fading noise.

Brillouin laser spectrometer based on spectral compression

We introduce a spectrometer design that uses Brillouin lasing to perform broadband spectral compression. This approach enables the entire C-band (optical frequencies covering 4 THz, or 25 nm) to be compressed into a 230 MHz wide RF spectrum—allowing a 4 THz wide optical spectrum to be monitored continuously using a standard analog-to-digital converter. This technique is based on the linear dependence of the Brillouin frequency shift on optical wavelength. To use this dependence for spectral analysis, we couple the input optical spectrum into a fiber ring cavity where it acts as an optical pump, exciting a frequency-shifted Brillouin lasing spectrum. The Brillouin lasing spectrum is then referenced to a copy of the original optical spectrum using heterodyne detection, converting the Brillouin frequency shift associated with each lasing mode to the RF domain. The narrow linewidth of the lasing modes enables a precise measurement of individual lines with an uncertainty of 28 MHz (0.2 pm) across a 4 THz band at an update rate of 200 Hz. This simple approach, constructed using standard fiber-coupled telecom components, provides an efficient method for high-resolution, broadband spectral analysis.

Compact real-time RF spectrum analyzer with 16 GHz instantaneous bandwidth based on photonic frequency-shifting loops

Spectral analysis of broadband RF signals in real time is of primary importance for numerous applications. So far, the instantaneous bandwidth of real-time spectrum analyzers based on conventional digital techniques is limited to a few GHz. This limitation is set by the clock jitter of the analog-to-digital converters, and by the processing capabilities in real time of digital electronics. On the contrary, analog architectures based on microwave photonics are not constrained by such limitations, and offer potentially a very high instantaneous bandwidth. However, they generally suffer from inherent limitations, such as large footprint and high complexity. Here, we propose a much simpler architecture of RF spectrum analyzer based on frequency-shifting loops. It utilizes only compact commercial telecom components, a single CW laser, and slow electronic resources (10 MSa/s). The probability of intercept is 100%, the instantaneous bandwidth reaches 16 GHz, and the spectral and temporal resolutions are respectively equal to 160 MHz and 50 µs. Our system is expected to open new avenues in embedded applications of microwave photonics.

Continuous-mode quantum key distribution with digital signal processing

Continuous-variable quantum key distribution (CVQKD) offers the specific advantage of sharing keys remotely by the use of standard telecom components, thereby promoting cost-effective and high-performance metropolitan applications. Nevertheless, the introduction of high-rate spectrum broadening has pushed CVQKD from a single-mode to a continuous-mode region, resulting in the adoption of modern digital signal processing (DSP) technologies to recover quadrature information from continuous-mode quantum states. However, the security proof of DSP involving multi-point processing is a missing step. Here, we propose a generalized method of analyzing continuous-mode state processing by linear DSP via temporal modes theory. The construction of temporal modes is key in reducing the security proof to single-mode scenarios. The proposed practicality oriented security analysis method paves the way for building classical compatible digital CVQKD.

Programmable frequency-bin quantum states in a nano-engineered silicon device

Photonic qubits should be controllable on-chip and noise-tolerant when transmitted over optical networks for practical applications. Furthermore, qubit sources should be programmable and have high brightness to be useful for quantum algorithms and grant resilience to losses. However, widespread encoding schemes only combine at most two of these properties. Here, we overcome this hurdle by demonstrating a programmable silicon nano-photonic chip generating frequency-bin entangled photons, an encoding scheme compatible with long-range transmission over optical links. The emitted quantum states can be manipulated using existing telecommunication components, including active devices that can be integrated in silicon photonics. As a demonstration, we show our chip can be programmed to generate the four computational basis states, and the four maximally-entangled Bell states, of a two-qubits system. Our device combines all the key properties of on-chip state reconfigurability and dense integration, while ensuring high brightness, fidelity, and purity.

Phase-sensitive distributed Rayleigh fiber sensing enabling the real-time monitoring of the refractive index with a sub-cm resolution by all-optical coherent pulse compression.

We have developed a novel architecture enabling distributed acoustic sensing in a commercial single-mode fiber with a sub-cm spatial resolution and an interrogation rate of 20 kHz. More precisely, we report the capability of real-time and space-resolved monitoring of the distributed phase and of the refractive index variations along the sensing fiber. The system reported here is optimal in many aspects. While the use of broadband light waveforms enables a sub-cm spatial resolution, the waveforms are quasi CW, delaying the occurrence of non-linear effects. Coherent detection ensures direct access to the distributed phase and to the local variations of the refractive index. Moreover, an all-optical pulse compression feature enables to lower the detection bandwidth down to 10 MSa/s. Based on a bi-directional frequency shifting loop, the architecture makes use of a single CW laser, commercial telecom components, and low frequency electronics. It is expected to open new avenues in distributed acoustic sensing applications, where high spatial resolution and high interrogation rates are required.

CONVECTIVE HEAT TRANSFER OF HEAT SINKS WITH PARTIALLY CUT PLATE FINS AND TURNING OF THEIR CUT SECTIONS

Plate-fin heat sinks are widely used for cooling radio electronic, power electronic, and telecommunication components. The current trends in the development of radio and microelectronic systems dictate the need to dissipate large heat fluxes. The present article uses the methods of numerical simulation, verified by experimental data, to study convective heat transfer of different-type heat sinks with partially cut plate fins. The heat sink with partially cut plate fins served as the basis of study. Three types of heat sinks with extended surfaces were also considered. First, we analyzed the fin cut section turned at an angle of 30&amp;deg; and then - the fin cut section with diverging or converging shape. Comparing the thermal and hydraulic performance of such heat sinks showed that the thermal and hydraulic performance of heat sinks with a fin cut section with diverging shape at a turning angle of 30&amp;deg; is by 10&amp;#37; higher than that of heat sinks with partially cut plate fins. As the velocity distribution in the wake shows, the use of heat sinks with partially cut plate fins and turning of their cut sections for cooling real microelectronic devices needs to correctly design an installation, in which the device is located.

Nonlinear controller for the laser fiber using PID controller

We show that a software architecture based on machine learning and adaptive control advances makes self-tuning optics possible. Commercially available optical telecom components may be combined with servo controllers to develop a training and execution software module that can self-tune the laser cavity even when it is switched off. Mechanical and/or environmental disturbances may aid in frequency comb stabilization. An exhaustive search of state space is used in the algorithm training stage to find the optimum performance areas for one or more objectively interesting functions. The technique of implementation stage starts by identifying the variable space using a sparse sensing approach, then settles on a near-optimal solution and maintains it using the extremum seeking control protocol.

Nonlinear controller for the laser fiber using PID controller

We show that a software architecture based on machine learning and adaptive control advances makes self-tuningoptics possible. Commercially available optical telecom components may be combined with servo controllers todevelop a training and execution software module that can self-tune the laser cavity even when it is switchedoff. Mechanical and/or environmental disturbances may aid in frequency comb stabilization. An exhaustive searchof state space is used in the algorithm training stage to find the optimum performance areas for one or moreobjectively interesting functions. The technique of implementation stage starts by identifying the variable spaceusing a sparse sensing approach, then settles on a near-optimal solution and maintains it using the extremumseeking control protocol.

Enhanced Anti-Freezing Heating Cable Standard for Fire Prevention

Among the fire reports caused by seasonal devices registered with the Korea Fire Information Center in 2021, fires caused by heating cables accounted for the largest portion with 350 cases. As a result of analyzing the heating cable fires from 2015 to 2021, we have classified the heating cable fires into four types according to the method of winding the heating wire. First, we hypothesized that the temperature is high when the density is high due to the overlap of the hot wires or when there is a thermal insulating material. We predicted that the temperature would rise through a random game and established a reproducibility test plan. In order to check how heat generation changes depending on the winding method of antifreeze heating cables, we selected 10 manufacturers and checked the temperature characteristics according to the test conditions (Paragraph 11, Paragraph 19.101) of the Technical Regulations for Electrical and Telecommunication Products and Components of Korea (K 10013), tested the four methods mentioned in this thesis and compared and analyzed the results. The experiment results indicate that the temperature of the heater part in antifreeze heating cables was mostly higher than the conditions required by the existing standards in cases 1 to 4. In particular, in the case of No. 5 manufacturer’s sample, the temperature of the heating cable of Case 1 was measured to be the highest at 119.0 °C. In addition, as a result of applying the data engineering reproducibility test results in the framework of the random game λ proposed in this thesis, we have derived the same results as the predicted hypothesis. Case 1 refers to the case where a fire occurs due to the heating cable being wrapped around the water pipe and insulation or taped outside; It is one of the methods that users actually use a lot in the field. Based on experiment, we have concluded that the fire risk is high under the Case 1 condition. Thus, the test conditions in the existing K 10013 Standard need to be strengthened according to the Case 1 condition.

Calibration of laser distance meter using Opto-Electronic oscillator

Laser-based Electronic Distance Meters (EDMs) are used extensively to measure inner/outer dimensions in constructions and large volumes. Therefore, it needs to be calibrated regularly to assure its proper function. In this paper, a distance measurement system based on Opto-Electronic Oscillator (OEO) is used for EDM calibration. The calibration is performed in three steps; the first step is to construct a reference OEO system using off-the-shelf optical telecommunication components. Then, the OEO system is used to calibrate an indoor baseline consisting of eleven distances ranging from 2.4 to 58 m. Finally, the calibrated baseline is used to calibrate the EDM.

Low-Loss Calibration-Free 2 × 2 Mach-Zehnder Switches With Varied-Width Multimode-Interference Couplers

Large-scale photonic switches are essential components for telecommunications and interconnects, incorporating many cascaded 2 × 2 optical switches. To keep the excess loss of the entire switch low, it is crucial to develop ultralow-loss 2 × 2 optical switches by introducing new coupler designs. In this paper, a low-loss calibration-free 2 × 2 Mach-Zehnder switch (MZS) designed with varied-width multimode-interference (MMI) couplers is proposed and fabricated. In this design, the MMI coupler has a varied-width MMI region and two multimode output waveguides. The MMI coupler optimized by the particle swarm optimization (PSO) algorithm has an ultralow excess loss < 0.053 dB and a suppressed higher-order mode excitation < −26 dB across the C-band (1530–1565 nm). Such a varied-width MMI coupler with two multimode output waveguides can be used compatibly for the MZS with widened phase shifters, so that the random phase imbalance between the two MZS arms can be suppressed effectively, which thus is promising for calibration-free operation. For the present MZS fabricated with standard 180-nm silicon photonic foundry processes, the excess loss is ∼0.5 dB across the C-band and the extinction ratio is ∼25 dB without calibration.

Digital synchronization for continuous-variable quantum key distribution

Continuous variable quantum key distribution (CV-QKD) is a promising emerging technology for the distribution of secure keys for symmetric encryption. It can be readily implemented using commercial off-the-shelf optical telecommunications components. A key requirement of the CV-QKD receiver is the ability to measure the quantum states at the correct time instance and rate using the correct orthogonal observables, referred to as synchronization. We propose a digital synchronization procedure for a modern CV-QKD system with locally generated local oscillator for coherent reception. Our proposed method is modulation format independent allowing it to be used in a variety of CV-QKD systems. We experimentally investigate its performance with a Gaussian modulated CV-QKD system operating over a 10–20 km span of standard single mode fibre. Since the procedure does not require hardware modifications it paves the way for cost-effective QKD solutions that can adapt rapidly to changing environmental conditions.

Nonlinear Surface Polaritons near the Interface between a Magneto-Optical Substance and a Nonlinear Metamaterial with a Permittivity Close to Zero

Relevance. Considerable attention of researchers is drawn to nonlinear surface optical waves, as they are promising for application in optical information processing systems, ultra-sensitive sensors, and modern telecommunications components. Purpose. To obtain an exact solution of the Maxwell equation system for TM-polarised nonlinear surface polaritons propagating along the interface between an optically linear magnetic medium and an optically nonlinear medium with saturated nonlinearity. Methods. Analysis of the properties of nonlinear surface polaritons (NSP) and mathematical modelling of the dependence of the permittivity of a nonlinear medium on the intensity are used. Results. TM-polarised nanoparticles propagating along the interface of a magneto-optical medium and a nonlinear optical metamaterial with a permittivity close to zero (ENZ-metamaterial) are studied. For NSP in such a structure, an exact solution of the Maxwell equation system is obtained, considering the saturation effect of optical nonlinearity. On this basis, the dependences of constant propagation on the total energy flux of NSP and energy fluxes in contact media in the structure were investigated: magneto-optical ENZ-metamaterial with negative permittivity/nonlinear self-focusing ENZ-metamaterial. Conclusions. The NSP energy flow is positive in a nonlinear medium and negative in a linear one. As the saturation level decreases, the NSP energy fluxes in the contacting media increase modulo, if the value of the NSP propagation constant (NSPPC) is fixed. The lowest NSPPC value for guiding nonlinearity is obtained when the total energy flow of the NSP becomes zero. As the saturation level decreases, the NSP propagation variable (NSPPV) increases. At a fixed NSPPC, with a decrease in the magnetic permeability, the energy fluxes of NSP in the contacting media increase. When the magnetic permeability decreases to zero and the NSP energy flux is positive, the NSPPV change range narrows

Continuous-variable quantum key distribution over a 15 km multi-core fiber

The secure transfer of information is critical to the ever-increasing demands of the digital world. Continuous-variable quantum key distribution (CV-QKD) is a promising technology that can provide high secret key rates over metropolitan areas, using conventional telecom components. In this study, we demonstrate the utilization of CV-QKD over a 15 km multi-core fiber (MCF), in which we take advantage of one core to remotely frequency lock Bob's local oscillator with Alice's transmitter. We also demonstrate the capacity of the MCF to boost the secret key rate by parallelizing CV-QKD across multiple cores. Our results indicate that MCFs are promising for the metropolitan deployment of QKD systems.