Current development trends concerning miniaturizing of electronics and photonics systems are aiming at assembly and 3D co-integration of a broad range of technologies including MEMS, microfluidics, wafer level optics, multilayered structures with through-silicon vias connection, and silicon photonics. Modern integration processes impose severe requirements on the design and functionality of research and assembly setups and their parts. In this work we demonstrate a simple, reliable, and cost-effective reconfigurable vacuum sample holder that ensures fast reconfiguration for electronic and photonic integration using laser assisted bonding (LAB) processes. The design is compatible with IR through-silicon microscopy with top and bottom irradiation/illumination architectures, which makes this concept instrumental for a large variety of research, assembly, lithography, and wafer bonding setups.

Current development trends concerning miniaturizing of electronics and photonics systems are aiming at assembly and 3-D co-integration of a broad range of technologies including MEMS, microfluidics, wafer level optics, and silicon photonics. To this end, on-chip integration using silicon-photonics platform offers a wide range of possibilities addressing passive optics functionality, active optoelectronic devices, and compatibility with CMOS fabrication. On the other hand, the hybrid technology enabling volume manufacturing of such system-on-chip components, it is still in an early development stage. Here, a new type of machine vision system enabling precision stacking and bonding processes of III–V components on silicon photonics chips is introduced. In particular, we focus on the ability to see through substrates with high resolution, which is crucial for the alignment of the markers used for assembly of integrated components on silicon wafer. The system is based on the use of a black silicon enhanced CMOS sensor with extended wavelength response beyond transparency cutoff wavelength for silicon substrate. We study the use of the camera system as a microscope with bottom coaxial infrared (IR) illumination scheme and demonstrate the ability of through-silicon vision for one- and two-layered silicon photonic integrated circuit (PIC) samples. The ability of observing objects with dimensions down to $2 \mu \text{m}$ is confirmed. This resolution is close to diffraction limit and corresponds to the dimensions of optical waveguide structures on the PICs surface. In addition, we demonstrate the implementation of a 2-D Fourier transform-based autofocusing technique for through-silicon IR microscopy. These building blocks offer a solution for advanced photonic integration processes and other through-silicon vision-related applications, which is instrumental for a large variety of assembly, lithography, and wafer bonding setups.

ООО «Т8», Москва, Россия СРАВНИТЕЛЬНЫЙ АНАЛИЗ МЕТОДОВ ИЗМЕРЕНИЯ СПЕКТРАЛЬНЫХ ШИРИН ВОЛОКОННЫХ ЛАЗЕРОВ С РАСПРЕДЕЛЕННОЙ ОБРАТНОЙ СВЯЗЬЮПредставлены результаты по отработке методики и измерению спектральных характеристик волоконных лазеров с распределенной обратной связью (РОС-лазеров), у которых длины резонаторов отличались на порядок -5,3 и 60 мм.Резонаторы на основе волоконных брэгговских решёток с фазовым сдвигом в структуре были изготовлены разными методами.Для записи 5,3-мм резонатора в фосфоросиликатном высоколегированном Er 3+ волоконном световоде использовался метод фемтосекундной поточечной записи, для записи 60-мм резонатора в волоконном световоде Nufern PS-ESF-3/125 использовался голографический метод записи и УФ-лазерное излучение.Спектральная ширина РОС-лазера в конфигурации с длиной резонатора 5,3 мм и выходной мощностью 400 мкВт варьировалась от 0,1 до 3,2 кГц, в зависимости от времени измерения (~10 мкс -1 с).Спектральная ширина РОС-лазера в конфигурации с длиной резонатора 60 мм и выходной мощностью 600 мкВт на соответствующих временных интервалах составляла от 0,01 до 5 кГц.

Fiber-optic interferometric sensor arrays are very attractive for many applications. One of the common used interrogation approaches for fiber-optic sensor arrays is the path matched differential interferometry (PMDI). It allows to interrogate a large number of multiplexed fiber-optic sensors by using an auxiliary compensation interferometer (CIF). This approach with using the phase modulator allows to implement the phase-generated carrier demodulation for multiplexed fiber-optic sensors. However, this approach has the significant disadvantage, which is that environmental vibroacoustic impacts on the CIF produce undesirable phase signals from the sensor array. It leads to increasing the noise floor level of the measuring system. In this paper the development methodology and results of the experimental investigation of the passive vibroacoustic isolation system for the CIF in the PMDI-based fiber-optic interferometric sensor are presented. The proposed isolation system is implemented by using acoustic absorbing layers and the special mechanical suspension system for the CIF mounted in the single rack unit. It is shown that the proposed approach for the CIF isolation allows to reduce its sensitivity to vibroacoustic impacts by up to 30 dB in the frequency range up to 500 Hz. It is also demonstrated that potting of the CIF fiber-optic components reduces its isolation efficiency by an average value of 8.3 dB in the considered frequency range, that is not applicable for interferometric sensors. The presented methodology and obtained results might be used in PMDI-based fiber-optic interferometric sensors to improve their performance characteristics.

The results of theoretical calculations and experimental studies of the characteristics of an acoustic test signal when using an acoustic enclosure of the “open-shield” type are presented. The enrichment of the test acoustic signal spectrum due to the use of the developed enclosure was up to +30 dB in the frequency range of up to 500 Hz and from +4 to +20 dB in the frequency range of 1500–5000 Hz in comparison with the loudspeaker without an enclosure. The effect of room characteristics on the acoustic signal at the measurement point was studied and a method for compensation of this influence was proposed. As a result of applying it, the nonuniformity of the amplitude–frequency response of the acoustic signal at the measurement point decreased from 7 to 1.5 dB and the slopes of its spectral characteristic were eliminated.

This article is devoted to the study of the influence of acoustic environmental impacts on the operation of fiber-optic interferometers and measuring systems that are based on them. A method for reducing this influence by using an acoustically conditioned sound-proofing case for operation in the presence of external impacts in a frequency range of 20 to 20 000 Hz is considered. A mathematical model and the results of its research are presented; the calculated dependence of the degree of reducing the acoustic sensitivity of a fiber-optic interferometer on the degree of acoustic sealing of its case is obtained. An experimental setup and a technique for experimental evaluation of the degree of acoustic sealing when studying the cases of devices were developed.

The dependence of the noise density in a signal of a fiber-optic towed streamer in a frequency band of 10 Hz–1 kHz on the towing speed in a range of 1 to 5 knots, on the coefficient of relative elongation of its elastic section, its type, and on the type of attachment of the elastic section to the towed body have been studied. In addition, the dependence of the tensile load on the studied streamer on the towing speed is obtained. The experimental data obtained during field tests on the streamer noise level and their analysis are presented. The reduction of the towing noise level when using an elastic section occurred by a factor of up to 3 in a frequency range of 180 to 600 Hz depending on the type of elastic section when attaching it to a strength member of the towed body, and up to 2 in the entire studied frequency range.

A path matched differential interferometry (PMDI) is one of the most common architectures for fiber-optic sensor arrays. It allows to interrogate many fiber-optic sensors time-multiplexed at a single fiber by using an auxiliary compensation interferometer (CIF). The CIF is typically based on an unbalanced Michelson or Mach-Zehnder interferometer. Therefore, it may be affected by different acoustic and vibration environmental noises. Any vibroacoustic impacts on the CIF might produce undesirable noises in the sensor signals and the noise performance of the measuring system will degrade. An environmental noise cancellation technique for the CIF in fiber-optic PMDI-based sensor arrays is presented in this paper. The proposed approach is based on the separate interrogation of the CIF by the additional fiber laser together with using polarization-division multiplexing. The noise cancellation is performing by the subtraction of the independent CIF's signal from measured signals from the sensors array. In this paper, the main parameters of the noise cancellation system, which are critical for its performance, are discussed in detail. The experimental efficiency estimation of the proposed technique was performed in situ under open water conditions. It was shown, that for the measured signal with the standard deviation of 0.059 rad and the environmental impact on the CIF with the standard deviation of 0.61 rad the noise cancellation efficiency was -24.9 dB. The proposed technique might be easily integrated to large-scale PMDI-based fiber-optic sensors arrays and it's compatible with PMDI-based Fiber Bragg Grating arrays in combination with the wavelength division multiplexing.

The results of an experimental test of the effectiveness of a method for compensating the influence of background noise on the operation of a fiber-optic compensative interferometer incorporated in a towable hydroacoustic cable assembly are presented herein. The principle of compensation is the detection of a separate phase signal induced by the noise on the interferometer's arms and its subsequent subtraction from the interferometer's output phase signal. An additional reference sensor that is isolated from external influence is introduced in the measuring system design to achieve the compensation. The effectiveness of noise canceling upon implementation of the suggested method is −14.73dB. This result can significantly reduce the noise level of measuring systems based on fiber-optic phase sensors and interferometers under real operating conditions.

The influence of environmental acoustic vibrations on cavities of fiber lasers may significantly decrease their parameters. It is shown that protective coatings for desensitization of fiber laser cavities with efficiency up to -95 dB compared to the level of acoustic sensitivity of optical fiber with standard acrylate coating can be produced by application of composite multi-layer structures of different-type materials.

Theoretical calculations and an experimental study of the degree of decrease in the acoustic sensitivity of an optical fiber in the frequency range of 20–20 000 Hz inside the cables of special design were carried out. A substantial decrease in acoustic sensitivity has been achieved, that is, more than –29 dB with respect to the standard single-mode SMF-28 fiber in a polymer shell. This result can significantly increase the threshold sensitivity of measuring systems based on fiber optic interferometers.

Fiber optic components, such as fiber optic interferometers, fiber sensors and fiber lasers have high level of sensitivity to environmental acoustic and vibration noise due to elasto-optical effect and fiber elongation under pressure. For most applications this effect is undesirable and it should be reduced for proper operation of fiber optic system. The proposed method for reducing the fiber components environmental noise sensitivity level is based on the implementation of two-layer protective construction. The experimental test confirmed its effectiveness of undesirable impact suppression at the level from -3.2 to -19 dB relatively to the acoustic sensitivity level of bare optical fiber sample. The effectiveness appeared to be directly proportional to the acoustic pressure level. This fact allows us to implement proposed construction as an acoustic shock absorber or an acoustic filter with external impact level dependent transfert characteristic for sensitive fiber optic components.

АннотацияПредмет исследования.Исследована проблема осуществления буксировки сейсмических кос при проведении морских геологоразведочных работ.Представлена классификация возникающих при осуществлении буксировки механических шумовых воздействий.Выполнен обзор основных технических решений для борьбы с каждым видом таких воздействий.Метод

Theoretical calculations and experimental study of the acoustic sensitivity suppression level of optical fiber inside the cables of a special design in the frequency range 20-20000 Hz were carried out. A high degree of reduction in acoustic sensitivity has been achieved. It was more than 29 dB suppression relatively to the standard single-mode SMF - 28 fiber in a polymer shell. This result can significantly increase the sensitivity of measuring systems based on fiber-optic interferometers.

Subject of Research. This paper presents the results of an experimental study on the possibility of applying single fiber Bragg gratings as sensitive elements for detecting ultrasonic impacts in gaseous or liquid media and at placing fiber Bragg gratings into various materials and structures for their status monitoring. Method. During the experiment, an ultrasonic impact with a fundamental frequency of 65 kHz was alternately turned on two sensitive elements based on two fiber Bragg gratings with different parameters: the physical grating length, reflection coefficient, and slope of the linear part of spectral characteristics. Comparative analysis of the obtained data with data from the reference piezoelectric ultrasonic sensor was performed. The results were evaluated in the frequency domain, at the range up to 200 kHz. The three first harmonics of the signal were studied: 65, 130 and 195 kHz. The signal-to-noise ratio for each sensor element and the ratio of signal values obtained from various sensor elements were evaluated. Main Results. The measurement setup was created on the basis of a small-sized tunable VCSEL and FPGA. It is shown that single fiber Bragg gratings are suitable for creation of sensitive elements for ultrasonic sensors and have values of sensitivity and dynamic range comparable to piezoelectric sensors. The range of detected frequencies was theoretically estimated and the assessment of the FBG parameters effect on the sensor sensitivity to ultrasonic action was performed. The ratios of the signals measured by the Bragg grating with a slope of the spectral characteristics equal to 142 1/nm and a reflection coefficient equal to 100%, to the signals from the grating with a slope of 44 1/nm and a reflection of 40% are equal to 5.8, 3.8, 7.1 for 65, 130 and 195 kHz, respectively. The ratios of the signals measured by the reference piezoelectric sensor to the signals measured by Bragg grating with a slope of the spectral characteristics equal to 142 1/nm and a reflection coefficient of 100% are 3.8, 6.2, 7.7 for 65, 130 and 195 kHz, respectively. Practical Relevance. The results of this study show the possibility of applying fiber Bragg gratings as the sensitive elements of threshold and measuring ultrasonic sensors for the placement in the volume and on the surface of the materials under study. The features and advantages of fiber-optic measuring systems provide the ease of installation for the arrays of sensors in the material or structure under research during production, insensitivity to external electromagnetic interference and the possibility of multiplexing a large number of sensitive elements on a single optical fiber.

The article presents an option of optoelectronic system for remote measurement of parameters of landing area for helicopter or convertaplane.

Исследованы процессы возбуждения и воздействия акустических колебаний на оптические сигналы в интегральных электрооптических модуляторах на подложках ниобата лития. Определены резонансные частоты возбуждения колебательных мод подложки. Показано, что акустические колебания могут вносить значительный вклад в передаточную характеристику модулятора на частотах до нескольких сотен мегагерц, что должно учитываться при использовании модуляторов на низких частотах, например, в составе волоконно-оптических датчиков. DOI: 10.21883/PJTF.2017.21.45166.16559