Distance Optical Fiber Research Articles

Application Research of Ultra-Long Span Optical Communication Technique in Power Emergency Communication

This paper presents a power emergency communication solution based on long distance optical fiber communication technology. It use a portable ultra-long span optical amplifying device composed by optical components, by configuring different optical amplification scheme, using redundancy fiber to set up a new transport channel quickly, it achieve the function of emergency communication. Specific configurations are proposed for 2.5G and 10G SDH optical transmission system, and conducted field test and validation. The solution is flexible to configure and easy to install, it provides a convenient emergency communication solution for fast failure recovery of fiber line interruption, damage of relay stations, and fiber aging in electric system.

85-fJ Dissipated Energy Per Bit at 30 Gb/s Across 500-m Multimode Fiber Using 850-nm VCSELs

We present important progress in energy efficiency for oxide-confined 850-nm single mode and quasi single mode vertical-cavity surface-emitting lasers (VCSELs) suitable for optical interconnects. Error-free operation at 30 Gb/s across 500 m of multimode optical fiber is achieved with 85 fJ of dissipated energy per bit. At 25 Gb/s, the maximum multimode fiber distance is 1000 m. These VCSELs are presently the most energy efficient directly modulated light-sources for data transmission across multimode optical fiber distances up to 1 km.

Very low input voltage cascaded travelling wave electroabsorption modulator (CTWEAM) for more than 100 Gbps

This paper presents the large signal modeling and simulation of two segmented travelling wave electroabsorption modulators (TWEAM) as a cascaded TWEAM (CTWEAM) structure. It will be demonstrated that a mushroom shaped mesa structure with low series resistance (0.69Ω-mm) will have 3dB bandwidth more than sufficient for 100Gbps operation. For a CTWEAM device with 990μm active segment length, 1.1V bias voltage and only 0.4V peak-to-peak (Vp–p) modulating voltage has a bandwidth of 110GHz, extinction ratio >4dB and flat frequency response. This device would be an attractive candidate for short distance optical fiber communication as well as long distance telecommunication at 0.4Vp–p and 1Vp–p input RF signal, respectively.

CONTINUOUS-VARIABLE QUANTUM KEY DISTRIBUTION PROTOCOLS WITH EIGHT-STATE DISCRETE MODULATION

We propose a continuous variable quantum key distribution protocol based on discrete modulation of eight-state coherent states. We present a rigorous security proof against the collective attacks by taking into consideration the realistic lossy and noisy quantum channel, the imperfect detector efficiency, and the detector electronic noise. This protocol shows high tolerance against excess noise and promises to achieve over 100 km distance of optical fiber.

A new type of bidirectional long distance optical fiber chaotic secure communication system

Based on the chaotic synchronization of two response semiconductor lasers (RLs) under the injection from a common chaotic signal of a drive laser (DL), a new type of secure communication system, which allows bidirectional and long-distance information transmissions, is proposed. A corresponding theoretical model is established to study the bidirectional transmission performance, security performance and the system performance under different transmission distances. The results show that when two RLs receive chaotic light injected from a DL, the chaotic outputs of two RLs achieve a fairly good isochronal synchronization without any time delay, while there is a big difference between the signals of RLs and the signal of DL; the system owns high security level after having analyzed the various ways from which eavesdropper may obtain message; if the ordinary single mode optical fiber is used as a transmission channel, the Q factor of decoded message can reach more than 6 after a propagation over 50km; if the dispersion-shifted fiber is employed, the Q factor of decoded message can still reach more than 6 after a propagation over 200km.

Compact optical fiber whitelight interferometric distance sensor for arbitrary small distance measurement

A compact optical fiber distance sensor that is capable of measuring arbitrary small distance is produced by fabricating a microsized polymer core at the end of a single mode fiber. The polymer core introduces an additional reflective interface to a conventional Fabry-Perot cavity. As such, sufficient fringes are presented in the whitelight reflectance spectrum of the distance sensor so that arbitrary small distances can be demodulated using the Fourier transformation technique. The performance of the distance sensor is verified experimentally.

胸腔鏡下手術のための位相差強調型腫瘍イメージャ

This paper discusses an availability of proposed Non-Contact Phase Difference type Imager capable of detecting a lung tumor based on phase differential technique for Video-Assisted Thoracic Surgery called VATS. The developed sensor is composed of an air supply system and an optical fiber distance sensor next to the air nozzle. A removed human lung is used to verify the performance of the developed sensor. Toward clinical application, it is confirmed that both a tumor detection capability and a safety to the lung tissues of the developed sensor through in vivo experiments by using pig lungs. Finally, we also show a newly sensing system for clinical application.

Polarization maintaining fibers for application in magnetic field measurements

Optical fibers may be applied in measurements of electrical current, particularly as so-called optical current transformers. Electric current sensors, in which optical fibers are used are small, light, cheap and safe. Their sensitivity is, however, due to the restricted magnetootpic properties of optical fibers, rather small. Moreover, these sensors are susceptible to deformations of the optical fiber. An increase of their sensitivity consists in lengthening the distance of optical fiber on which the magnetic field acts. However, this can lead to an increase of disturbances caused by changes of internal stresses. The negative effects can be reduced by applying optical fibers with a higher magnetooptic sensitivity and a lower susceptibility to mechanical stresses and deformations. The present paper deals with side-hole optical fibers with a decreased birefringence reducing the susceptibility to deformations. The optical fibers consist of a multicomponent glass with a higher value of the refractive index, thanks to which the sensitivity to the effect of the external magnetic field is increased. In future such optical fibers are planed to be applied in magnetooptic sensors.

An angular offset launching technique for bandwidth enhancement in multimode fiber links

AbstractWe propose an angular offset technique for launching optical signals into multimode fibers (MMFs) used in short distance optical fiber links. The signal is launched onto the angled facet of an MMF. The presented method shows better bandwidth enhancement in comparison with the conventional lateral offset launching method with a little power penalty. This method is simple and can be easily adopted in transmitters for high‐speed MMF links. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 165–168, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22988

THE PULSE BROADENING STUDY OF GAUSS-CHIRPED PULSE IN OPTICAL FIBERS

The pulse broadening due to dispersion in optical fiber is studied by solving the nonlinear Schrödinger equation through the Fourier transform method. The expression of pulse width in terms of its root-mean-square and the pulse broadening factor of the Gauss-chirped pulse are given. Meanwhile, the influence of the propagating optical fiber distance on the pulse broadening is given. The influence of the chirped factor on the pulse broadening and the optical fiber dispersion on pulses with different widths are analyzed and discussed.

Practical quantum key distribution over 60 hours at an optical fiber distance of 20km using weak and vacuum decoy pulses for enhanced security

Experimental one-way decoy pulse quantum key distribution running continuously for 60 hours is demonstrated over a fiber distance of 20km. We employ a decoy protocol which involves one weak decoy pulse and a vacuum pulse. The obtained secret key rate is on average over 10kbps. This is the highest rate reported using this decoy protocol over this fiber distance and duration.

Evaluation of restoration techniques incorporating optimal principle in WDM optical networks

Numerous researchers have proposed restoration techniques incorporating the concept of shortest disjoint paths in Wavelength Division Multiplexing (WDM) optical networks. The concept of shortest disjoint paths that obeys the strong optimal principle and the weak optimal principle is very important because shorter wavelength mileage including optical fiber distances is a dominant factor for the design of a survival WDM optical network. Even if restoration techniques incorporating the concept of shortest disjoint paths are faster, simpler, and easier than any other restoration techniques, we need to evaluate how well the concept of shortest disjoint paths is incorporated for the design of a survivable WDM optical network. In this paper, topology dependencies related to the concept of shortest disjoint paths are first developed. Then, seven objective functions that yield objective goals significant to the optimal design of a survivable WDM optical network are proposed and mathematically formulated. Finally, we develop ASDP (Near-Optimally Annealed k-Shortest Disjoint Path Restoration) and BBD (Branch-and-Bound with Dynamic Programming Principle) restoration algorithms that examine the proposed objective functions. Numerical results by experimenting ASDP and BBD algorithms show that the concept of shortest disjoint paths yields the best performance in terms of total and average restoration time. However, the concept of shortest disjoint paths does not seem to be an optimal technique in terms of significant optimal objective goals: minimal wavelengths, minimal wavelength link distance, minimal wavelength mileage costs, and even distribution of traffic flows.

Long-distance entanglement swapping with photons from separated sources

We report the first experimental realization of entanglement swapping over large distances in optical fibers. Two photons separated by more than two km of optical fibers are entangled, although they never directly interacted. We use two pairs of time-bin entangled qubits created in spatially separated sources and carried by photons at telecommunication wavelengths. A partial Bell state measurement is performed with one photon from each pair which projects the two remaining photons, formerly independent onto an entangled state. A visibility high enough to violate a Bell inequality is reported, after both photons have each travelled through 1.1 km of optical fiber.

EFFECT OF PHONONS IN STIMULATED BRILLOUIN SCATTERING ON OPTICAL FIBER COMMUNICATION

Stimulated Brillouin scattering (SBS) can be used for phase conjugation mirrors in many laser systems1,5 and it also often appears in long distance optical fiber communication systems because the threshold of SBS is normally inversely proportional to the interaction length.2 In this paper, the effect of phonon loss is investigated. Our study shows that phase conjugation systems do require lower phonon loss and higher nonlinearity as expected but higher phonon loss and lower nonlinearity are actually desirable for long distance optical fiber communications.

Broad-band millimeter-wave (38 GHz) fiber-wireless transmission system using electrical and optical SSB modulation to overcome dispersion effects

A spectrally efficient millimeter-wave (mm-wave) fiber-wireless transmission system is presented demonstrating downstream transportation of 155-Mb/s BPSK data at 38 GHz over 50 km of standard single-mode fiber and a 5-m wireless link. The effect of fiber chromatic dispersion on the transmission of the mm-wave optical carrier was overcome by using a single dual-electrode Mach-Zehnder modulator to generate optical single-sideband (SSB) modulation with carrier. We also demonstrate a simple technique for obtaining electrical SSB that will allow the effect of fiber dispersion across the bandwidth of the information to be overcome with simple electrical delay equalization. We predict that this fiber-wireless system could permit the transportation of mm-wave signals with large bit rates over long optical fiber distances.

Optimal Solitary Pulse Stabilisation in a Gradient Distributed Rare-Earth Doped Fiber Amplifier

In this paper a new kind of device — a gradient distributed fiber amplifier — is proposed and analysed. In such an amplifier the concentration of the dopant ions increases along its length in the direction of pump power decrement, in a way that ensures nearly constant signal gain coefficient in every point of the fiber. Hence, an optimal amplification configuration that simultaneously stabilises the pulses against the background attenuation, the soliton self- frequency shift and the third order dispersion can be chosen and maintained globally in such a device. The results of the computer model clearly show that a gradient fiber amplifier can be designed as a completely transparent transport media for high-speed, long distance optical fiber communications.

Compensation of dispersion in optical fibers for the 1.3-1.6 mu m region with a grating and telescope

The transmission of ultrashort optical pulses over long distances in optical fibers is limited by pulse broadening due to group velocity dispersion. A grating and telescope dispersion compensator with group velocity dispersion of equal magnitude and opposite sign can compensate for the fiber dispersion. The possible benefits of such dispersion compensation in the 1.3-1.6- mu m wavelength region are investigated. The results show that compensation of first-order dispersion at 1.55 mu m in a fiber with zero dispersion near 1.3 mu m is primarily limited by the second-order dispersion of the grating and the telescope compensator. For a wavelength slightly greater than the zero dispersion wavelength, both the first- and second-order group velocity dispersion can be canceled by the grating and telescope dispersion compensator, allowing transmission exceeding 100 Gb/s over 100 km.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Solitons in optical communications

In this paper we have calculated the effects of loss on the propagation of soliton solutions of the nonlinear Schrodinger equation. Since we are interested in the application of these results to optical communications, it is necessary to go beyond perturbative results. This is due to the fact that propagation distances in optical fibers are significantly greater than the decay length of the energy in the pulses. Some conclusions are drawn about the application of solitons in long-distance communications.