Kilometers Of Fiber Research Articles

Polymeric Photonic Crystal Fibers for Textile Tracing and Sorting

AbstractCircular supply chains require more accurate product labeling and traceability. In the apparel industry, product life cycle management is hampered in part by inaccurate, poorly readable, and detachable standard care labels. Instead, this article seeks to enable a labeling system capable of being integrated into the fabric itself, intrinsically recyclable, low‐cost, encodes information, and allows rapid readout after years of normal use. In this work, all‐polymer photonic crystals are designed and then fabricated by thermal drawing with >100 layers having sub‐micrometer individual thickness and low refractive index contrast (Δn = 0.1). The fibers exhibit reflectance features in the 1–5.5 µm wavelength range, characterized using insitu Fourier transform infrared spectroscopy. Drawn photonic fibers are then woven into fabrics, characterized by near‐infrared spectroscopy and short‐wave infrared imaging, techniques commonly used in industrial facilities for sorting materials. The fibers’ optical design also enables the use of overtone peaks to avoid overlap with parasitic molecular absorption, substantially improving the signal‐to‐noise ratio (and therefore ease and speed) of readout. The ability to produce kilometers of fiber that are compatible with existing textile manufacturing processes, coupled with low input material cost, make these a potential market‐viable improvement over the standard care label.

Development of Quantum Protocol Modification CSLOE–2022, Increasing the Cryptographic Strength of Classical Quantum Protocol BB84

Quantum cryptography protocols make it possible not only to ensure the protection of data transmitted in a communication channel from unauthorized access by intruders, but also to detect the existence of any attempted interception. This scientific direction is currently relevant, since it is related to the problem of security and data protection in current information and communication networks. The article is devoted to quantum cryptography; it describes the development of quantum protocols as quantum key distribution systems. Grounded on the laws of quantum mechanics, the elaboration of modifications of secure data transfer protocols is shown. The authors considered the best-known protocol to be BB84 of quantum key distribution; a more modern modification of this protocol is BB84 Info-Z. Comparative analysis of these has also been carried out. It has been established that the BB84-Info-Z quantum protocol works more efficiently than BB84 since its lower error threshold allows the interceptor to obtain much less information about the secret key. The authors put forward a new idea to improve the BB84 protocol (which has been quite outdated for almost 40 years), due to the increase in modern requirements for quantum cryptography protocols. The modification is called CSLOE-2022. It enables significant intensification of cryptographic strength and the entanglement degree of the interceptor (cryptanalyst), which greatly complicates the very possibility of intercepting information. The ultimate goal of the CSLOE-2022 modification is to complicate the eavesdropping process so much that it can be considered completely useless for an attacker in terms of wasting time and resources. The modification allows exceeding the known speed limit of key generation without repeaters since it uses two sources, the phases of which, in addition to the hundreds of kilometers of fiber between them, are very difficult to stabilize. Comparison of the protocols by working distance showed that for BB84, this distance does not exceed 70 km; for BB84-Info-Z it is similar, at no more than 70 km, and the modification of CSLOE-2022 proposed by the authors theoretically allows increasing the working distance of the quantum protocol to 511 km (7.3 times).

Cascaded Microwave Frequency Transfer over 300-km Fiber Link with Instability at the 10−18 Level

Comparing and synchronizing atomic clocks between distant laboratories with ultra-stable frequency transfer are essential procedures in many fields of fundamental and applied science. Existing conventional methods for frequency transfer based on satellite links, however, are insufficient for the requirements of many applications. In order to achieve high-precision microwave frequency transfer over a thousand kilometers of fiber and to construct a fiber-based microwave transfer network, we propose a cascaded system for microwave frequency transfer consisting of three 100-km single-span spooled fiber links using an improved electronic phase compensation scheme. The transfer instability measured for the microwave signal reaches 1.1 × 10−14 at 1 s and 6.8 × 10−18 at 105 s, which agrees with the root-sum-square of each span contribution. It is feasible to extend the length of the fiber-based microwave frequency transfer up to 1200 km using 4 stages of our cascaded system, which is still sufficient to transfer modern cold atom microwave frequency standards. Moreover, the transfer instability of 9.0 × 10−15 at 1 s and 9.0 × 10−18 at 105 s for a 100-MHz signal is achieved. The residual phase noise power spectral density of the 300-km cascaded link measured at 100-MHz is also obtained. The rejection frequency bandwidth of the cascaded link is limited by the propagation delay of one single-span link.

Proof-of-Principle Experimental Demonstration of Twin-Field Type Quantum Key Distribution.

The twin-field (TF) quantum key distribution (QKD) protocol and its variants are highly attractive because they can beat the well-known fundamental limit of the secret key rate for point-to-point QKD without quantum repeaters (repeaterless bound). In this Letter, we perform a proof-of-principle experimental demonstration of TFQKD based on the protocol proposed by Curty, Azuma, and Lo, which removes the need for postselection on the matching of a global phase from the original TFQKD scheme and can deliver a high secret key rate. Furthermore, we employ a Sagnac loop structure to help overcome the major difficulty in the practical implementation of TFQKD, namely, the need to stabilize the phase of the quantum state over kilometers of fiber. As a proof-of-principle demonstration, the estimated secure key rate from our experimental TFQKD data at the high loss region surpasses the repeaterless bound of QKD with current technology.

Photonic-Delay Line Cross Correlation Method Based on DWDM for Phase Noise Measurement

A dual photonic-delay line cross-correlation method for phase noise measurement of microwave signal based on dense wavelength division multiplexing (DWDM) is proposed and experimentally demonstrated. The kilometer-long delay fiber is used together by the two mutually independent channels through the DWDM technology, which makes it easier to get the same delay between two channels. And it reduces the cost of the system by reducing the use of several kilometers of fiber and a Mach-Zendher modulator. Then, it uses variable optical fiber delay lines to replace the electronic phase shifters and a broader operation bandwidth can be obtained. A lower phase noise floor has been obtained by more averaging of the cross-correlation spectrum. In the experiments, the phase noise of a 10-GHz microwave signal has been measured accurately. A large operation bandwidth of 4-11 GHz is achieved and a measurement phase noise floor of -152.6 dBc/Hz at 10 kHz offset at 10 GHz in a 20 μs delay measurement system is realized by averaging 100 times.

Equalization-Enhanced Phase Noise in Stokes-Vector Direct Detection Systems

In this work, we provide both numerical and experimental investigations of equalization-enhanced phase noise (EEPN) in Stokes-vector direct detection (SV-DD) systems. We show that the influence of EEPN cannot be neglected in high symbol rate SV-DD systems after transmission over several hundred kilometers of fibers when electronic chromatic dispersion compensation and lasers with linewidths of the order of Megahertz are employed. Simulation results are presented to evaluate the dependence of EEPN effects on laser linewidth, transmission distance, and symbol rate. Experiments are then conducted in a 56-Gbaud 16-quadrature amplitude modulation (QAM) SV-DD system to demonstrate the EEPN-induced performance degradation after 320-km transmission over standard single mode fiber (SSMF).

Brillouin Optical Correlation Domain Analysis Addressing 440 000 Resolution Points

The distributed Brillouin analysis of an 8.8-km-long fiber with a spatial resolution of 2 cm is presented. All 440 000 potential resolution points are addressed in the measurement. A 7-cm-long hot-spot, located toward the output end of the pump wave, is properly identified in the experiment. The experimental error in the estimate of the local values of the Brillouin frequency shift is ±3.5 MHz. The analysis is based on the simultaneous generation and analysis of Brillouin interaction in more than 2000 correlation peaks, induced by periodic phase modulation of the pump and signal waves. The Brillouin amplifications at individual peaks are resolved using radar-like coding of pump wave magnitude by a 10000 bit-long aperiodic sequence, and postdetection compression at the receiver end. Extensive numerical simulations of the Brillouin interactions over kilometers of fiber with centimeter resolution are reported as well. The results are at the state of the art for high-resolution distributed Brillouin sensors.

Reflective-SOA Fiber Cavity Laser as Directly Modulated WDM-PON Colorless Transmitter

Reflective semiconductor optical amplifier (RSOA) fiber cavity lasers are attractive colorless, self-seeded, self-tuning, and directly modulatable sources for passive optical networks (PONs). They comprise of an RSOA in the optical network unit as the active element, a distribution fiber as the laser cavity, a waveguide grating router, and a common reflective mirror with the latter two positioned at the remote node. In this paper, we introduce a model and perform simulations to elucidate the recently discovered successful operation of this new PON source. The results are in agreement with experiments; the formation of a narrow laser spectrum with a relatively constant output power is seen despite a relatively broad passband window of the waveguide grating router. We further study mode competition and mode partition noise. It is shown that proper chromatic dispersion management can overcome mode partition noise limitations. The quality of the RSOA fiber cavity laser does not degrade when being directly modulated and as a result these highly multimode lasers offer an economic way to transport Gbit/s upstream data over kilometers of fiber in a wavelength division multiplexing-PON.

High-sensitivity temperature sensing using higher-order Stokes stimulated Brillouin scattering in optical fiber

In an effort to reduce the cost of sensing systems and make them more compact and flexible, Brillouin scattering has been demonstrated as a useful tool, especially for distributed temperature and strain sensing (DTSS), with a resolution of a few centimeters over several tens of kilometers of fiber. However, sensing is limited by the Brillouin frequency shift's sensitivity to these parameters, which are of the order of ~1.3 MHz/°C and of ~0.05 MHz/με for standard fiber. In this Letter, we demonstrate a new and simple technique for enhancing the sensitivity of sensing by using higher-orders Stokes shifts with stimulated Brillouin scattering (SBS). By this method, we multiply the sensitivity of the sensor by the number of the Stokes order used, enhanced by six-fold, therefore reaching a sensitivity of ~7 MHz/°C, and potentially ~0.30 MHz/με. To do this, we place the test fiber within a cavity to produce a frequency comb. Based on a reference multiorder SBS source for heterodyning, this system should provide a new distributed sensing technology with significantly better resolution at a potentially lower cost than currently available DTSS systems.

The Human Brain Project and neuromorphic computing.

Understanding how the brain manages billions of processing units connected via kilometers of fibers and trillions of synapses, while consuming a few tens of Watts could provide the key to a completely new category of hardware (neuromorphic computing systems). In order to achieve this, a paradigm shift for computing as a whole is needed, which will see it moving away from current "bit precise" computing models and towards new techniques that exploit the stochastic behavior of simple, reliable, very fast, lowpower computing devices embedded in intensely recursive architectures. In this paper we summarize how these objectives will be pursued in the Human Brain Project.

Soft capacitor fibers using conductive polymers for electronic textiles

A novel, highly flexible, conductive polymer-based fiber with high electric capacitance isreported. In its cross section the fiber features a periodic sequence of hundreds of conductiveand isolating plastic layers positioned around metallic electrodes. The fiber is fabricatedusing the fiber drawing method, where a multi-material macroscopic preform is drawn intoa sub-millimeter capacitor fiber in a single fabrication step. Several kilometers of fibers canbe obtained from a single preform with fiber diameters ranging between 500 and1000 µm. A typical measured capacitance of our fibers is60–100 nF m−1 and it is independent of the fiber diameter. Analysis of the fiber frequency response showsthat in its simplest interrogation mode the capacitor fiber has a transverse resistance of5 kΩ m L−1, which is inversely proportional to the fiber lengthL and is independent of the fiber diameter. Softness of the fiber materials, the absence ofliquid electrolyte in the fiber structure, ease of scalability to large productionvolumes and high capacitance of our fibers make them interesting for varioussmart textile applications ranging from distributed sensing to energy storage.

Experimental comparison of Raman gain efficiency of a dispersion compensating fiber in C and O‐bands

AbstractWe measured the Raman gain efficiency (RGE) of a dispersion compensating fiber in the C (1530–1565 nm) and O‐bands (1260–1360 nm) and the results revealed that the RGE reaches its maximum value inside the O‐band. The spectral analysis of the fiber loss and Raman efficiency shows that the increase in Raman gain efficiency toward short wavelengths is balanced by the increasing of the fiber attenuation which leads the RGE to be maximum around 1310 nm. In addition, we characterized the gain of a Raman amplifier in the O‐band with a moderate pump power and a few kilometers of fiber. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 151–154, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24865

Direct spinning of carbon nanotube fibres from liquid feedstock

Carbon nanotubes are regarded by many as being the next generation in high performance materials due to their unique properties. The Cambridge Process was developed to utilize these unique properties by directly spinning carbon nanotube fibres drawn from an aerogel sock. The sock is formed from carbon nanotubes grown via a catalytic chemical vapour deposition (CVD) process. Due to the nature of CVD, the process is readily scalable. Kilometres of fibre can be made at a rate of 20 m/min. Altering process parameters (catalyst concentration, feedstock injection rate, furnace temperature, and gas flow rate) allows the production of nanotubes of a desired morphology. The fibres have been characterized with scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman Spectroscopy in order to confirm nanotube composition and orientation. The fibre possesses mechanical and electrical properties that rival or exceed those of present-day materials. Mechanical properties can be enhanced by increasing the degree of orientation of the nanotubes with the long axis of the fibre and by overall densification. These effects can be accomplished through drawing the fibre and solvent treatment.

Determination of the optimum electrical bandwidth for spectral slicing

The implementation of wavelength division multiplexing (WDM) in communication access networks is dependent upon the availability of low cost optical sources. One possible alternative to lasers is to employ slices of a broadband optical source obtained via optical filters, which may be tuneable. This paper considers the behaviour of such a spectrally sliced optical transmission system as a function of the bandwidth of a realistic receiver electrical filter for the first time. The treatment includes distortion from optical fibre dispersion over several kilometres of fibre. The optimum ratio between the electrical bandwidth and the optical bit rate is found to be ~0.6 for a fifth-order Bessel filter

Fiber Bragg gratings for dispersion compensation in optical communication systems

Dispersion compensating fibers (DCF) are the most widely used technology for dispersion compensation. A DCF without Raman amplification introduces extra loss in the system, thus increasing the need for gain in the discrete amplifiers and degrading the noise performance. The idea to additionally use the DCF as a Raman gain medium was originally proposed by Hansen et al. in 1998. [1] This was quickly followed by Emori et al., who demonstrated a broadband, loss less DCF using multiple-wavelength Raman pumping. [2] DCF is a good Raman gain medium, due to a relatively high germanium doping level and a small effective area. To get sufficient gain with a reasonable pump power, a discrete Raman amplifier has to contain several kilometers of fiber, adding extra dispersion to the system that must be handled in the overall dispersion management. Dispersion compensating Raman amplifiers integrates two key functions: dispersion compensation and discrete Raman amplification into a single component.

High Spectral Density Long-Haul 40-Gb/s Transmission Using CSRZ-DPSK Format

This paper presents an experimental investigation of 40-Gb/s DWDM transmission technologies that can potentially transport multiple terabits of aggregate capacity with ultrahigh spectral efficiency over several thousand kilometers of fiber in a terrestrial optical network. By using carrier-suppressed return-to-zero (CSRZ) differential-phase-shift-keyed (DPSK) modulation format with optimized signal filtering, we have demonstrated transmission of 6.4-Tb/s capacity with 0.8-bit/s/Hz spectral efficiency over 3200 km of fiber using 100-km amplified spans. This transmission was conducted using 160 50-GHz-spaced wavelength channels, each at 42.7 Gb/s, in the standard C + L wavelength bands. Low dispersion-slope TrueWave REACH fiber plus slope-matched dispersion compensating fiber with all-Raman amplification were also employed to achieve this record 20-Pbit/s/km capacity-distance product for terrestrial 40-Gb/s systems. In addition, we used a loop-synchronous polarization controller (PC) to better emulate the polarization effects of a straight-line system.

Chemical Reactions in the Manufacture of Waveguides for Long Distance Optical Data Transmission

One of the modern high technologies which has advanced enormously in the last few years is glass fiber technology. This is used in the manufacture of glass fibers for lighting purposes and for the optical transfer of analog and digital data with a high transfer density. The technical demands made on the glass fibers required for data transfer, the optical waveguides, are extremely high and are already fulfilled to a large extent by industry. At present about four million kilometers of fiber, worth ca. 800 million DM are produced worldwide (10% in the Federal Republic of Germany). Numerous chemical processes take place during the manufacture of optical waveguides. However, in contrast both to the high and constantly growing demands on the quality and to the increasing production volume of such fibers, little is in fact known about the reactions involved. The present article will attempt to develop a picture of the multifarious reactions occurring in the course of this technical process on the basis of literature data and our own studies.

Design methodology for the mechanical reliability of optical fiber

An engineering methodology for the mechanical reliability of optical fiber is developed within a fracture-mechanics framework. The model expresses allowable in-service and installation stresses as a fraction of fiber strength in a fatigue environment for a range of n values and fiber types. Failure probability is incorporated into the model by the measurement of the fiber-strength distribution appropriate to the application. For long-length applications, strength distributions of hundreds to thousands of kilometers of fiber are needed. A 400-km strength distribution captures the beginnings of the truncated portion of the distribution.

Method for obtaining long-length strength distributions for reliability prediction

A technique for measuring the fiber strength distribution of many kilometers of fiber was developed. The strength distribution of 100 km can be generated in a week's time by a single operator. A strength distribution for 400 km of fiber is shown to depart from the high-strength region around the 1% failure probability level and the data exhibit the beginnings of the truncated portion of the strength distribution. Such data are believed to be useful in making failure probability predictions, process improvements, and aid in the understanding of crack-growth behavior during proof testing.