Fiber Optic Telecommunication Research Articles

Optical neural networks based on optical fiber-communication system

In this work, we propose a novel design for optical neural network system based on reservoir computing. The optical neurons in the system consist of directional couplers, optical fibers, and optical amplifiers. The nonlinear activation function of optical neuron can be obtained by the optical amplifiers. Mach–Zehnder phase modulators and the directional couplers are used to build the readout matrix in the output layer. The performance of the system is studied by a commercial software of optical fiber telecommunication system. The results show that the randomly connected optical neuron networks of the reservoir computing can provide a better performance.

Methods of mechanical noise impact suppression during streamer towing process using fiber Bragg gratings

Subject of Research. The paper deals with the problem of seismic streamers towing process during marine geological exploration. Classification of the mechanical noise effects during towing process is presented. A brief overview of the main technical solutions is performed for suppression of each impact type. Method. A method is proposed for calculating the parameters of elastic sections for suppression of noise effects, which takes into account towed body tension level. We show the possibility and prospects of applying for this purpose a fiber-optic strain measurement system based on Bragg gratings inscribed in the G.657.A1 standard SMF-28 telecommunication optical fiber with a sampling rate of 5 kHz as part of a fiber-optic seismic streamer design. Main Results. Experimental data on the prototype research are given. With the relative elongation of the uniform-strength bar in the range up to 1030 μm/m, an average sensitivity of 0.68 pm (μm/m) is achieved, and the spread of values is ±1 pm. It is shown that the work of fiber Bragg gratings is practically non-inertial itself. The response time and dynamic range of the sensor amplitude is largely determined by the properties of metal bars and tool set where optical fibers are fixed. Practical Relevance. Application of the method provides opportunities for the solid construction of the towed body. The possibilities for calculation of the elastic section parameters to the specific conditions of marine geological exploration and continuous state monitoring of the towed body are presented. The method makes it possible to control the quality of the recorded seismic data and partially compensate the undesirable effects during signal processing. Proposed measures will increase significantly the accuracy and reliability of the obtained geological data.

All-optical wavelength reservation for flexible spectrum networks using amplifier saturation and VCSEL injection

Advanced metro-access WDM optical fiber telecommunication networks use integrated wavelength switching nodes to provide efficient, flexible wavelength allocation along the link. Recent developments, together with the increase in bandwidth intense applications, have sparked great interest in flexible, grid-like optical network systems. Flexible spectrum optical network systems with nonstatic channel bandwidth, wavelength allocation, switching, and routing permit the optimum distribution of data with variable rates and modulation formats. We describe a unique technique for all-optical wavelength reservation at a forwarding flex spectrum node. The outgoing signal is locked to the incoming signal at the node, thereby guaranteeing automatic wavelength reservation and allocation. A saturated erbium-dope fiber amplifier (EDFA) is used to erase data from the incoming signal, which is then used to lock the wavelength of the forwarding node through vertical cavity surface emitting laser injection. The EDFA is shown to reduce the extinction ratio of the incoming signal from 7.3 dB to less than 1 dB (560 mdB). We show automatic wavelength reservation over 1.68 nm within the C-band, with 25.5-km transmission over G. 655 single mode fiber. Considering 50-GHz per-channel bandwidth allocations, this technique translates to four-channel operation in a typical metro-access type configuration.

A proposal for distributed humidity sensor based on the induced LPFG in a periodic polymer coated fiber structure

In this paper, a distributed relative humidity (RH) or moisture sensor is proposed. The proposed structure is a single mode telecommunication optical fiber coated by humidity sensitive and insensitive polymers periodically. The polymer coated fiber is surrounded by a high Young’s modulus material such as stainless steel mesh. The swelling of the coated Humidity Sensitive Polymers (HSPs) as a result of moisture absorption induces fiber gratings in the single mode fiber. Depending on the coating period relative to the light wavelength, the induced fiber grating can be Fiber Bragg Grating (FBG) or Long Period Fiber Grating (LPFG). The light reflected by the induced FBG or losses due to the coupled energy to the cladding modes in the induced LPFG can be employed to describe the sensor operation. Since long period length (LPFG) manufacturing is much simpler than short period length (FBG) sensors, this investigation is concentrated on the long period length sensors.

Cryptography in coherent optical information networks using dissipative metamaterial gates

All-optical encryption of information in fibre telecommunication networks offers lower complexity and far higher data rates than electronic encryption can deliver. However, existing optical layer encryption methods, which are compatible with keys of unlimited length, are based on nonlinear processes that require intense optical fields. Here, we introduce an optical layer secure communication protocol that does not rely on nonlinear optical processes but instead uses energy redistribution of coherent optical waves interacting on a plasmonic metamaterial absorber. We implement the protocol in a telecommunication optical fibre information network, where signal and key distribution lines use a common coherent information carrier. We investigate and demonstrate different encryption modes, including a scheme providing perfect secrecy. All-optical cryptography, as demonstrated here, exploits signal processing mechanisms that can satisfy optical telecom data rate requirements in any current or next-generation frequency band with bandwidth exceeding 100 THz and a switching energy of a few photons per bit. This is the first demonstration of an optical telecommunications application of metamaterial technology.

Photodetector device for fiber optical telecommunication systems

Photodetector device for fiber optical telecommunication systems

Toward High-Performing Topological Edge-State Optical Isolators

The development of on-chip optical isolators for integrated photonic circuits has been actively pursued for several decades now, especially since the advent of optical-fiber telecommunication. This article reports the experimental realization, practical implementation, and performance of a $t\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}p\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}g\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l$ $e\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}g\phantom{\rule{0}{0ex}}e\ensuremath{-}s\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}e$ $i\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}r$, based on the Su-Shrieffer-Heeger model in the optical regime. Such isolators have been predicted to deliver superior isolation ratios (up to -50 dB at telecom wavelengths), due to the existence of a topological edge state in the forward propagation direction, and its destruction in the reverse direction via the magneto-optical nonreciprocal phase-shift effect.

An ultra-sensitive aptasensor on optical fibre for the direct detection of bisphenol A

We present a plasmonic biosensor capable of detecting the presence of bisphenol A in ultra-low concentrations, yielding a wavelength shift of 0.15 ± 0.01 nm in response to a solution of 1 fM concentration with limit of detection of 330 ± 70 aM The biosensing device consists of an array of gold nano-antennae with a total length of 2.3 cm that generate coupled localised surface plasmons (cLSPs) and is covalently modified with an aptamer specific for bisphenol A recognition. The array of nano-antennae is fabricated on a lapped section of standard telecommunication optical fibre, allowing for potential multiplexing and its use in remote sensing applications. These results have been achieved without the use of enhancement techniques and therefore the approach allows the direct detection of bisphenol A, a low molecular weight (228 Da) target usually detectable only by indirect detection strategies. Its detection at such levels is a significant step forward in measuring small molecules at ultra-low concentrations. Furthermore, this new sensing platform paves the way for the development of portable systems for in-situ agricultural measurements capable of retrieving data on a substance of very high concern at ultra-low concentrations.

Quantum optical microcombs

A key challenge for quantum science and technology is to realise large-scale, precisely controllable, practical systems for non-classical secured communications, metrology and ultimately meaningful quantum simulation and computation. Optical frequency combs represent a powerful approach towards this, since they provide a very high number of temporal and frequency modes which can result in large-scale quantum systems. The generation and control of quantum optical frequency combs will enable a unique, practical and scalable framework for quantum signal and information processing. Here, we review recent progress on the realization of energy-time entangled optical frequency combs and discuss how photonic integration and the use of fiber-optic telecommunications components can enable quantum state control with new functionalities, yielding unprecedented capability.

Distributed Acoustic Sensing Using Dark Fiber for Near-Surface Characterization and Broadband Seismic Event Detection

We present one of the first case studies demonstrating the use of distributed acoustic sensing deployed on regional unlit fiber-optic telecommunication infrastructure (dark fiber) for broadband seismic monitoring of both near-surface soil properties and earthquake seismology. We recorded 7 months of passive seismic data on a 27 km section of dark fiber stretching from West Sacramento, CA to Woodland, CA, densely sampled at 2 m spacing. This dataset was processed to extract surface wave velocity information using ambient noise interferometry techniques; the resulting VS profiles were used to map both shallow structural profiles and groundwater depth, thus demonstrating that basin-scale variations in hydrological state could be resolved using this technique. The same array was utilized for detection of regional and teleseismic earthquakes and evaluated for long period response using records from the M8.1 Chiapas, Mexico 2017, Sep 8th event. The combination of these two sets of observations conclusively demonstrates that regionally extensive fiber-optic networks can effectively be utilized for a host of geoscience observation tasks at a combination of scale and resolution previously inaccessible.

Low Batch Size Production of Glass Products requiring Micrometer Precision

Abstract With the fourth industrial revolution manufacturing industry faces new challenges. Small batches of personalized parts must be produced in an economically viable manner. In this study, we show the feasibility of an approach using Spark Assisted Chemical Engraving to achieve personalized parts of hard-to-machine materials like glass with a low-cost setup. This glass machining process reduces machining overhead as the tool - substrate interaction force is nearly zero. This approach can be used for on-demand manufacturing of personalized high precision applications of glass such as sensors, smartphone covers, advanced medical devices or fiber optic telecommunications.

Acoustic Fiber Bragg Grating and Its Application in High Temperature Sensing

A novel concept of acoustic fiber Bragg grating (AFBG) was conceived and experimentally validated as an effective technique for high-temperature sensing. Similar to the well-known optical fiber Bragg grating, the AFBG employs interactions between waves and periodic structures on an elongated waveguide. Acoustic waves reflected from periodic structures interfere with each other and result in the emergence of resonance frequency when acoustic wavelength matches with pitch length of the periodic structures. When the single-mode operation condition is satisfied, the resonance frequency location can be accurately resolved and thus be used as an effective indicator for temperature sensing. To demonstrate this concept, an AFBG sample was fabricated on a telecommunication optical fiber (125- $\mu \text{m}$ diameter) with femtosecond laser micromachining setup, and it demonstrated sensing capability up to 700 °C, which was limited by the fiber material (fused silica) and could be over 1400 °C if other material, such as sapphire, was used as the waveguide. With the features of various applicable material, low system cost, and potential multiplexing capability, this AFBG technology is a promising candidate for high-temperature sensing, even in a distributed manner.

FDTS as Dewetting Coating for an Electrowetting Controlled Silicon Photonic Switch

The self-assembled monolayer FDTS (1H,1H,2H, 2H-Perfluorodecyltrichlorosilane) is presented as suitable dewetting coating material for an electrowetting on dielectrics (EWOD) controlled silicon photonics switch deployed in fiber optic telecommunication systems. The anti-sticking characteristics of Perfluorodecyltrichlorosilane (FDTS) are compared to those of polytetrafluoroethylene (PTFE) as most common dewetting coating for EWOD devices. It is shown that FDTS could outperform other materials such as PTFE when an extremely thin, long-term stable, and uniform layer is required. In the specific case, FDTS is applied in vapor phase as anti-sticking coating to the active optical surface of the integrated silicon photonics switch thus enabling the EWOD driven liquid motion. The suitability of the coating is presented by contact angle measurements and durability tests carried out with the switching liquids. Finally, it is demonstrated by optical measurements that the FDTS coating has a neglectable influence on the optical switching performance.

Noise Analysis of Group IV Material-Based Heterojunction Phototransistor for Fiber-Optic Telecommunication Networks

This paper presents an analytical study of the noise behavior and spectral responsivity of Ge1− x Sn x alloy-based heterojunction phototransistors (HPTs) for different Sn compositions and base doping concentrations. The structure consists of n-Ge/p+ − Ge1− x Sn x /n− − Ge1− x Sn x layers pseudomorphically grown on Si substrate via Ge virtual substrate, compatible with complementary metal-oxide-semiconductor technology. The high absorption coefficient of the alloy in base significantly improves signal-to-noise ratio in the high-frequency region, leading to efficient photodetection in the $C$ - and $L$ -bands of fiber-optic telecommunication window. A comparison is made between the theoretical findings for GeSn HPTs and the available data for currently employed group III–V compound-based HPTs, to examine if GeSn-based HPT can be a good alternative.

Dynamic strain determination using fibre-optic cables allows imaging of seismological and structural features

Natural hazard prediction and efficient crust exploration require dense seismic observations both in time and space. Seismological techniques provide ground-motion data, whose accuracy depends on sensor characteristics and spatial distribution. Here we demonstrate that dynamic strain determination is possible with conventional fibre-optic cables deployed for telecommunication. Extending recently distributed acoustic sensing (DAS) studies, we present high resolution spatially un-aliased broadband strain data. We recorded seismic signals from natural and man-made sources with 4-m spacing along a 15-km-long fibre-optic cable layout on Reykjanes Peninsula, SW-Iceland. We identify with unprecedented resolution structural features such as normal faults and volcanic dykes in the Reykjanes Oblique Rift, allowing us to infer new dynamic fault processes. Conventional seismometer recordings, acquired simultaneously, validate the spectral amplitude DAS response between 0.1 and 100 Hz bandwidth. We suggest that the networks of fibre-optic telecommunication lines worldwide could be used as seismometers opening a new window for Earth hazard assessment and exploration.

Ultrastable laser interferometry for earthquake detection with terrestrial and submarine cables.

Detecting ocean-floor seismic activity is crucial for our understanding of the interior structure and dynamic behavior of Earth. However, 70% of the planet's surface is covered by water, and seismometer coverage is limited to a handful of permanent ocean bottom stations. We show that existing telecommunication optical fiber cables can detect seismic events when combined with state-of-the-art frequency metrology techniques by using the fiber itself as the sensing element. We detected earthquakes over terrestrial and submarine links with lengths ranging from 75 to 535 kilometers and a geographical distance from the earthquake's epicenter ranging from 25 to 18,500 kilometers. Implementing a global seismic network for real-time detection of underwater earthquakes requires applying the proposed technique to the existing extensive submarine optical fiber network.

Observation of a group of dark rogue waves in a telecommunication optical fiber

Over the past decade, the rogue wave debate has stimulated the comparison of predictions and observations among different branches of wave physics, particularly between hydrodynamics and optics, in situations where analogous dynamical behaviors can be identified, thanks to the use of common universal models. Although the scalar nonlinear Schroedinger equation (NLSE) has constantly played a central role for rogue wave investigations, moving beyond the standard NLSE model is relevant and needful for describing more general classes of physical systems and applications. In this direction, the coupled NLSEs are known to play a pivotal role for the understanding of the complex wave dynamics in hydrodynamics and optics. Benefiting from the advanced technology of high-speed telecommunication-grade components, and relying on a careful design of the nonlinear propagation of orthogonally-polarized optical pump waves in a randomly birefringent telecom fiber, this work explores, both theoretically and experimentally, the rogue wave dynamics governed by such coupled NLSEs. We report, for the first time, the evidence of a group of three dark rogue waves, the so-called dark three-sister rogue waves, where experiments, numerics, and analytics show a very good consistency.

Liquid crystal optrode arrays: a novel approach to neural interfaces

Liquid crystal optrode arrays: a novel approach to neural interfaces

Investigation of the Static and Dynamic Characteristics for a Wafer-Fused C-band VCSEL in the Mode of the Optical-Electric Converter

The results of an experimental study for a long wavelength vertical cavity surface-emitting laser of a wafer-fused construction as an effective resonant cavity enhanced photodetector of analog optical signals are described. The device is of interest for a number of promising microwave photonics applications and for creation of a low-cost photoreceiver in a high-speed fiber optics telecommunication system with dense wavelength division multiplexing. The schematic of the testbed, the original technique allowing to calculate the passband of the built-in optical cavity, and the results of measuring dark current, current responsivity, amplitude- and phase-frequency characteristics during the process of photo-detection are demonstrated.

Исследование статических и динамических характеристик сплавного VCSEL C-диапазона в режиме оптико-электрического преобразователя

AbstractThe results of an experimental study for a long wavelength vertical cavity surface-emitting laser of a wafer-fused construction as an effective resonant cavity enhanced photodetector of analog optical signals are described. The device is of interest for a number of promising microwave photonics applications and for creation of a low-cost photoreceiver in a high-speed fiber optics telecommunication system with dense wavelength division multiplexing. The schematic of the testbed, the original technique allowing to calculate the passband of the built-in optical cavity, and the results of measuring dark current, current responsivity, amplitude- and phase-frequency characteristics during the process of photo-detection are demonstrated.