Optical Transmission Line Research Articles

Flexible and wavelength-independent optical transmission for laser pointing stabilization and assembly error compensation.

A flexible light guide was developed for an ITER (International Thermonuclear Experimental Reactor) poloidal polarimeter which is a passive laser beam alignment and stabilization system for free-space propagation of a wide range of wavelengths. The advantages of using a flexible light guide are (1) to compensate the relative movement between the floor of a building and an optical table, (2) to negate assembly error of the optical transmission line, (3) to minimize the time required for assembly of the line and laser position alignment in a radiological environment, and (4) to transmit a wide wavelength range from visible to far-infrared. The authors fabricated a flexible light guide with an inner diameter of 120 mm and with a motion range of 10 cm. Pointing stability of the laser beam passing through the flexible light guide was less than 70 μrad when the support moved ±50 mm. A flexible light guide error of 70 μrad leads to a beam position displacement of 0.98 mm at a beam position steering mirror ITER poloidal polarimeter that is located 14 m from the flexible light guide. The achieved error is stable enough to guide the laser beam to its target in ITER.

COUPLING COEFFICIENTS OF DIFFERENT SPHERICAL DIELECTRIC MICRORESONATORS

Background. Nowadays, further increase of processing and transmission speed of information is associated with the development of hybrid integrated circuits, combining electrical and optical components. One of the important constituent parts of future optical integrated circuits are filters that can be conveniently implemented using so-called disc microresonators with whispering gallery oscillations. Technically, the problem of manufacturing such filters in the infrared and even in the visible wavelength range has been solved, but calculation of parameters and tuning of multilink filters is impossible without further development of the theory of their building. The development of such a theory is based on the electrodynamic modeling of processes that occur in complex systems of coupled microcavities, coupled with transmission line. At present, the study of filters that built on different microresonators hasn’t been carried out. Objective. The aim of the research is to construct the theory of electromagnetic wave scattering of the integral optical transmission lines on systems of coupled diversiform optical microresonators with whispering gallery modes, as well as development of mathematical models of filters constructed using various disk microresonators, and investigation of new structures of coupled microresonators with acceptable scattering characteristics. Methods. To construct a mathematical model of filters, an approximate solution of the Maxwell equations based on perturbation theory is used. The application of perturbation theory made it possible to find a solution to the problem of calculating the S-matrix of the filter in an analytical form. Results. An electrodynamic model for the scattering of optical transmission line waves by a system of coupled diversiform microresonators made of different dielectrics is developed. New structures of microresonators, realizing bandpass and bandstop filters, are investigated and their scattering characteristics are calculated. Conclusions. The theory of scattering of electromagnetic waves by systems of coupled diversiform optical microresonators is expanded. A new definition of the coupling coefficients of different microresonators is given. New filter models are constructed. Keywords: infrared range; integrated optics; optical filter; bandstop filter; bandpass filter; microresonator.

Behavior Monitoring Based on Intensity Matrix Distribution in Output Plane of Single-Mode Fiber Bundle

A smart structure using intensity-based optical fiber sensors has the potential to be a simple and low-cost system. In this paper, a novel fiber-optic smart structure system using a complementary metal–oxide–semiconductor (CMOS) is demonstrated that simultaneously monitors a number of hetero-core optical fiber bending sensors. The proposed system can integrate a number of optical fiber transmission lines. Therefore, the system does not require a number of photodetectors, which is different from conventional techniques. To simultaneously measure optical intensity, we coupled a number of hetero-core optical fiber sensors to a CMOS camera. The optical fiber sensor can detect macrobending to the optical light intensity. The output images comprise luminance spots distribution directly representing the sensor arrangements in the smart structure. A template matching technique based on the sum of absolute differences was introduced to distinguish between the overall behaviors of structures. A recognition experiment for object shapes was performed with a smart pressure sheet in which hetero-core optical fiber sensors are embedded as a simple case. In addition, a real-time human body posture recognition application was implemented using a fiber-optic smart clothing to apply the proposed system. Recognition results show that all images comprising luminance spots distribution were matched with the correct template images, with an error rate of 0% for 15 trials.

Broadband Wireless Optical Nanolink Composed by Dipole-Loop Nanoantennas

In this paper, a broadband wireless optical nanolink with plasmonic optical nanoantennas is theoretically proposed and analyzed. The nanolink is formed by linear dipole-loop nanoantennas for transmitter and receiver. The analysis is performed using the linear method of moments with equivalent surface impedance, where we apply a voltage source in the transmitting antenna and connect a load in the receiving antenna. The power received in the load is investigated as a function of frequency and distance between transmitter and receiver. In addition, a comparison is made between this wireless nanolink with a bifilar optical transmission line. The results show that the proposed nanolink, with dipole-loop nanoantenna, can increase the operating bandwidth in the range of 179.1–202.5 THz, when compared with conventional nanolink based only on dipole antennas. In addition, wireless nanolinks, based on dipole or dipole-loop antennas, are more suitable than wired nanolink for distances above approximately 22 μm.

Directional Optical Travelling Wave Antenna Based on Surface Plasmon Transmission Line

AbstractHighly‐directional optical travelling wave antennas based on Ag nanowires are created, whose half‐power beamwidth is achieved as small as 20°. The radiation direction can be effectively adjusted over a range of up to 45.6° by changing the feeding surface plasmon modes, and they have an ultra‐broad bandwidth due to their nonresonant characteristic. A theoretical model based on mode coupling theory is constructed that can give a full description of the radiation properties, such as the radiation pattern, beam solid angle, radiation efficiency, and working bandwidth. The optical travelling wave antennas are easy to fabricate, control, and integrate with optical transmission lines; thus, they should have great potential applications in nanophotonic devices.

Babinet-Inverted Optical Nanoantenna Analogue of Electromagnetically Induced Transparency**Supported by the National Key Research and Development Program of China under Grant No 2016YFA0301300, the National Natural Science Foundation of China under Grant Nos 11374041, 11574035 and 11404030, and the State Key Laboratory of Information Photonics and Optical Communications.

A Babinet-inverted optical nanoantenna analogue of electromagnetically induced transparency based on the coupling between two magnetic dipole antennas and a magnetic octupole antenna in a Au film waveguide is demonstrated. Simulation results indicate that a pronounced elimination occurs in the radiating spectrum due to the coupling-induced radiation suppression. A two-oscillator electromagnetically induced transparency model is used to describe the antenna. The coupling coefficient between the magnetic dipole antennas and the magnetic octupole antenna is calculated using the model and is found to decline exponentially with the increase of the distance between them. Such an antenna can be directly integrated with optical waveguides or transmission lines, thus is of fundamental significance for the applications in nano-optics, such as the optical device miniaturizations and photonic circuit integrations.

Chirped solitons in derivative nonlinear Schrödinger equation

The exact chirped solitons are derived from the derivative nonlinear Schrödinger equation (DNLS). The obtained chirps could help for either pulse compression or amplification in optical fiber and nonlinear electrical transmission line. The 22 new obtained chirped solitons and 22 soliton solutions of the DNLS could help in the understanding of the phenomena in which waves are governed by such equation.

Impulse Response Measurement of Few-Mode Fiber Systems by Coherence-Recovered Linear Optical Sampling

This paper presents impulse response measurements of few-mode optical fibers and transmission lines that were obtained by using coherence-recovered linear optical sampling or a two-comb interferometer. When performing a measurement, the probe pulse source and the sampling pulse source may be far from each other, particularly when the fibers are installed in the field, and the fiber length may exceed several tens kilometers. In this paper, by modifying a previously proposed referencing technique, the coherence between two pulse lasers is equivalently maintained by canceling out the phase noise caused both by the light sources and perturbations in the fiber. Hence, the amplitude averaging is used to enhance the signal-to-noise ratio. As a result, we can measure the impulse responses of multimode fibers with a dynamic range of 80 dB and a time resolution of a few picoseconds, over tens nanoseconds of differential mode delay.

Evaluation of Fibre Lifetime in Optical Ground Wire Transmission Lines

Abstract In the research, measurements of polarisation mode dispersion of two OPGWs (optical ground wire transmission lines), in total four fibres, have been carried out, and the expected lifetime of the infrastructure has been assessed on the basis of these measurements. The cables under consideration were installed in 1995 and 2011, respectively. Measurements have shown that polarisation mode dispersion values for cable installed in 1995 are four times higher than that for cable installed in 2011, which could mainly be explained by technological differences in fibre production and lower fibre polarisation mode dispersion requirements in 1995 due to lack of high-speed (over 10 Gbit/s) optical transmission systems. The calculation methodology of non-refusal work and refusal probabilities, using the measured polarisation mode dispersion parameters, is proposed in the paper. Based on reliability calculations, the expected lifetime is then predicted, showing that all measured fibres most likely will be operational within minimum theoretical service life of 25 years accepted by the industry.

MODELING OF THE OPTICAL FILTERS ON DIFFERENT WGM DISK MICRORESONATORS

Background. At the present time, further increase in the speed of processing and transmission of information is associated with the development of hybrid integrated circuits, combining electrical and optical components. One of the important constituent parts of future optical integrated circuits are filters that can be conveniently implemented using so-called disc microresonators with whispering gallery oscillations. Technically, the problem of manufacturing such filters in the infrared and even in the visible wavelength range has been solved, but calculation of parameters and tuning of multilink filters is impossible without further development of the theory of their building. The development of such a theory is based on the electrodynamic modeling of processes that occur in complex systems of coupled microcavities, coupled also with transmission line. At present, the study of filters built on different microresonators has not been carried out. Objective. The aim of the research is to construct the theory of scattering of electromagnetic waves of the integral optical transmission lines on systems of coupled different optical microresonators with whispering gallery modes. Development of mathematical models of filters constructed using various disk microresonators. Investigation of new structures of coupled microresonators with acceptable scattering characteristics. Methods. To construct a mathematical model of filters, an approximate solution of the Maxwell equations based on perturbation theory is used. The application of perturbation theory made it possible to find a solution to the problem of calculating the S-matrix of the filter in an analytical form. Results. An electrodynamic model for the scattering of optical transmission line waves by a system of different shapes coupled microresonators and made of different dielectrics is developed. New structures of microresonators, realizing bandpass and bandstop filters, are investigated and their scattering characteristics are calculated. Conclusions. The theory of scattering of electromagnetic waves by systems of various coupled optical microresonators is expanded. A new definition of the coupling coefficients of different microresonators is given. New models of filters are constructed.

Broadband Dipole-Loop Combined Nanoantenna Fed by Two-Wire Optical Transmission Line

This paper presents a broadband nanoantenna fed by a two-wire optical transmission line (OTL). The antenna is defined by a combination of a dipole and a loop, where only the dipole element is connected to the OTL. The analysis is fulfilled by the linear method of moments with equivalent surface impedance to model the conductors. Firstly, the nanoantenna alone is investigated, where the input impedance, current distribution, reflection coefficient, fractional bandwidth, radiation efficiency, and radiation pattern are analyzed. Then, the input impedance matching of this antenna with the OTL is considered. In this case the current, near field distribution, radiation pattern, and reflection coefficient are calculated for different geometrical parameters. The results show that the loop inserted in the circuit can increase the bandwidth up to 42% and decreases the reflection coefficient in the OTL to −25 dB.

Energy-Efficient Routing and Bandwidth Allocation in OFDM-Based Optical Networks

This paper introduces a novel routing and bandwidth allocation strategy for orthogonal frequency-division multiplexing (OFDM)-based elastic optical networks, aiming to optimize the network operational expenditures in terms of energy consumption. Based on the previously reported analytical bit error rate model for an OFDM-based optical transmission line, an optimization problem is formulated to allocate a set of lightpaths according to realistic network topologies, where the routing path, modulation level, bandwidth, and optical transceiver power of each lightpath are jointly determined for achieving minimum power consumption. To reduce computational complexity, a suboptimal iterative flipping method for solving the above NP-complete optimization problem is proposed, which achieves better performance than a simulated annealing scheme while consuming considerably fewer search iterations.

An additional channel for FM signal transmission in standard fiber-optic AM communication lines

A paradigm has been developed according to which an additional FM signal transfer channel is formed in a standard optical fiber transmission line without violating the main AM channel operation. Using the proposed approach, an RS-232 interface signal has been experimentally transferred via a standard intraobject 100-Mbit Ethernet line based on an SMF-28 single-mode optical fiber.

Optical radio-photonic channel for transmission of a coherent narrowband analog signal

The channel of an optical transmission line of coherent narrowband analog signal consisting of a continuous-wave laser, an electro-optic modulator, and a vector phase rotator based on electrically controlled fiber-optical 1 × 2 splitter and fixed delay lines is analyzed. The scheme is constructed from commercially available components used in digital optical communication systems. The applicability of components for analog and small-signal circuits is determined. Variation of radio signal phase in the range from 0° to 170° for radio signal frequencies between 1 and 2 GHz is demonstrated experimentally. It is shown that phase variation is a linear function of frequency in this range.

LiNbO<sub>3</sub> 광도파로 제작에 관한 연구

In this paper, waveguide analysis was interpreted as an optical waveguide using the feedback perturbation method simple and easy to apply compared to the analysis method, while the other almost identical to the numerical calculation method. In addition, efficient coupling with an optical transmission line of optical fiber and the waveguide form the thin film of different functional elements is required in order to achieve the full optical communication system. However, problems arise, such as the light field (field) and the decrease of the access efficiency due to inconsistency in the distribution characteristics of the connection surface by the difference in size of the cross section thereof when connecting the optical fiber and the waveguide directly to the combination of a thin film. Therefore propose a new type of connector structure to increase the efficiency of the connection when connecting the optical fiber waveguide and the thin film was analyzed by applying a coupled mode theory, the binding efficiency of the modified contactor. And by diffusing Ti on the substrate and a wide range of applications in the manufacture of integrated optical material made of a current low-loss Ti: optical waveguide and making the Y-branch waveguide, and the properties were confirmed.

A Low Time-Dispersion Refractive Optical Transmission Line for Streak Camera Measurements

A Low Time-Dispersion Refractive Optical Transmission Line for Streak Camera Measurements

The design of a correlation electron cyclotron emission system on J-TEXT.

To study the anomalous transport, a correlation electron cyclotron emission (CECE) was planned to be developed on J-TEXT for electron temperature fluctuation measurement. The spectral decorrelation method was employed for the CECE system. It was developed based on the previous 16-channel electron cyclotron emission system. They shared the optical transmission line and mixer. The CECE part consists of 4 channels. Two fixed frequency narrow band filters were used for two channels and two yttrium iron garnet (YIG) filters for the other two channels. To meet the measuring requirement, some tests have been taken for the YIG filters. The results show good performance of the filters. Gaussian optics is used to produce a good poloidal resolution. Wavenumbers resolved by the CECE diagnostic are k(θ) ≤ 1.5 rad/cm and k(r) ≤ 12 rad/cm. Some preliminary experiment results are also presented in this paper.

Scattering of the optical pulses on multiple micro-resonator band-stop filters

Pulses’ envelopes scattered on several Microresonator band-stop filters were examined in the optical transmission line. The most widespread optical pulses have been studied. The possibilities of pulses' time manipulation with various carrier frequencies are showed. New approaches to the indistinguishable pulses' separation have been proposed by means of transformation in to observable ones distinguished by amplitudes or time. A compression possibility has been shown for the chirped pulses. Reference 8, figures 8.

Radiation and absorption properties of gold nanodipoles in transmitting mode

ABSTRACTThis article presents an analysis of radiation and absorption properties of cylindrical gold nanodipoles in the transmitting mode. The conventional antenna theory and the linear method of moments are used for theoretical analysis of these antennas in the near‐infrared and lower optical frequencies (100−500 THz). Frequency dependence of radiation and absorption parameters such as input impedance, efficiency, radiation, and loss resistance is calculated for different dipole's lengths and radii. The presented results can be useful to design efficient nanodipoles and to perform the input impedance matching of these antennas with plasmonic optical transmission lines. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1–6, 2015

Recovering the propagation delay of an optical pulse.

Causality and special relativity pose an upper limit to the amount of advance that an optical pulse can acquire during a superluminal propagation. Such a limit can be circumvented if the pulse, before entering the superluminal medium, is retarded by letting it propagate under normal dispersion. We present an experimental evidence of this fact by showing that a laser pulse propagating in an atomic vapor, quasi resonant with an inverted transition and in conditions of anomalous dispersion, moves faster if it is previously retarded in a cell containing the same medium with no population inversion. Optical transmission lines often need an amplification stage to overcome the signal attenuation and the unavoidable delay respect to propagation at c; in this paper we tailor such stage to provide also an optical controlled recover of such delay. We believe that our results can open exciting prospects for real-life optical data processing and communication.