Km Of Optical Fiber Research Articles

IJARCCE - Computer and Communication Engineering

2 Abstract: In this paper, dispersion compensating fibers (DCF) are used to compensate the positive dispersion accumulated over the length of the fiber at 10Gbits/sec and 250 km of optical fiber with 50 km of DCF. Three schemes (Pre-compensation, post-compensation and symmetrical-compensation) of dispersion compensation with DCF are proposed. The simulated transmission system has been analyzed on the basic of different parameters by using OptiSystem 7.0 simulator. The results of three dispersion compensation methods are compared in terms of four parameter, which are Q-factor, BER, Eye height and threshold value, investigated at the receiver end. Further, it has been observed that the system needs proper matching between EDFA gain and the length of the fiber for the optimum performance.

Provably secure and practical quantum key distribution over 307 km of optical fibre

Proposed in 1984, quantum key distribution (QKD) allows two users to exchange provably secure keys via a potentially insecure quantum channel. Since then, QKD has attracted much attention and significant progress has been made in both theory and practice. On the application front, however, the operating distance of practical fibre-based QKD systems is limited to about 150 km, which is mainly due to the high background noise produced by commonly used semiconductor single-photon detectors (SPDs) and the stringent demand on the minimum classical- post-processing (CPP) block size. Here, we present a compact and autonomous QKD system that is capable of distributing provably-secure cryptographic key over 307 km of ultra-low-loss optical fibre (51.9 dB loss). The system is based on a recently developed standard semiconductor (inGaAs) SPDs with record low background noise and a novel efficient finite-key security analysis for QKD. This demonstrates the feasibility of practical long-distance QKD based on standard fibre optic telecom components.

Photonic Integrated Multichannel WDM Modulators for Data Read-Out Units

This study presents the recently developed monolithic photonic-integrated circuits that provide efficient amplitude modulation for wavelength division multiplexed optical channels. The circuits were designed for application as a read-out unit in a high-energy physics experiment, and are sufficiently general to be applied in various types of high-speed photonic transmitters. They were constructed using basic building blocks provided in an indium phosphide-based generic integration technology process and fabricated in a multi-project wafer run. Two variants of the circuits, utilizing modulators in Mach-Zehnder and Michelson interferometer configuration, are discussed. A modulation bandwidth of 18.6 GHz was measured and error-free transmission of a 10-Gb/s signal through 85 km of optical fiber was achieved.

A novel dispersion monitoring technique in W-band radio-over-fiber signals using clustering on asynchronous histograms

Radio over Fiber (RoF) systems have been proposed as a promising solution for transmitting radiofrequency signals at high data rates over long distances. To reach data rates in the Gbps range, studies indicate using the W-Band (75 -110 GHz). However, in this frequency band, chromatic dispersion becomes an issue that increases the bit-error-rate. This paper presents a novel digital dispersion monitoring technique for RoF systems based on asynchronous histogram analysis. This method quantifies the intensity level of the distortion of a radiofrequency demodulated signal by a dispersion factor. This dispersion factor is calculated using an enhanced clustering approach, which carries out a Gaussian fitting technique through the expectation-maximization algorithm. Dispersion monitoring was performed on radiofrequency transmission simulations using non-return-to-zero and binary phase-shift keying modulated signals over 80 km of optical fiber at 60, 75 and 100 GHz. The bit error rate is estimated and compared to the dispersion factor, showing that the behavior of the dispersion effects are not proportional to the increase of carrier frequency, bit rate and distances. This novel monitoring method can be used to estimate the feasibility of RoF systems for future hybrid networks under specific transmission parameters such as fiber length, modulation format, and carrier frequency.

10-Gb/s All-Optical VPN in WDM-PON Using Injection-Locked Fabry–Pérot Laser Diodes

A 10-Gb/s reconfigurable all-optical virtual private network (VPN) scheme in wavelength-division-multiplexed passive optical networks is proposed. The upstream VPN optical signal from the source optical network unit (ONU) is wavelength converted by mutual injection locking of a Fabry-Pérot laser diode at the optical line terminal to a different wavelength and then transmitted to the target ONU. The proposed scheme is power efficient and reconfigurable. In the experiment, the power penalty at a bit error rate of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> is 1.4 dB after transmission in 25 km of optical fiber. The impact of detunes and powers of the injected light on the system performance are also studied. The experimental results show that the wavelength detunes and signal powers should be selected appropriately to achieve optimal system performance.

Distribution of Entangled Photon Pairs over 300 km of Optical Fiber

Distribution of Entangled Photon Pairs over 300 km of Optical Fiber

A fiber-based quasi-continuous-wave quantum key distribution system

We report a fiber-based quasi-continuous-wave (CW) quantum key distribution (QKD) system with continuous variables (CV). This system employs coherent light pulses and time multiplexing to maximally reduce cross talk in the fiber. No-switching detection scheme is adopted to optimize the repetition rate. Information is encoded on the sideband of the pulsed coherent light to fully exploit the continuous wave nature of laser field. With this configuration, high secret key rate can be achieved. For the 50 MHz detected bandwidth in our experiment, when the multidimensional reconciliation protocol is applied, a secret key rate of 187 kb/s can be achieved over 50 km of optical fiber against collective attacks, which have been shown to be asymptotically optimal. Moreover, recently studied loopholes have been fixed in our system.

Measurement-based noiseless linear amplification for quantum communication

Entanglement distillation is an indispensable ingredient in extended quantum communication networks. Distillation protocols are necessarily non-deterministic and require advanced experimental techniques such as noiseless amplification. Recently it was shown that the benefits of noiseless amplification could be extracted by performing a post-selective filtering of the measurement record to improve the performance of quantum key distribution. We apply this protocol to entanglement degraded by transmission loss of up to the equivalent of 100km of optical fibre. We measure an effective entangled resource stronger than that achievable by even a maximally entangled resource passively transmitted through the same channel. We also provide a proof-of-principle demonstration of secret key extraction from an otherwise insecure regime. The measurement-based noiseless linear amplifier offers two advantages over its physical counterpart: ease of implementation and near optimal probability of success. It should provide an effective and versatile tool for a broad class of entanglement-based quantum communication protocols.

A fast and versatile quantum key distribution system with hardware key distillation and wavelength multiplexing

We present a compactly integrated, 625 MHz clocked coherent one-way quantum key distribution system which continuously distributes secret keys over an optical fibre link. To support high secret key rates, we implemented a fast hardware key distillation engine which allows for key distillation rates up to 4 Mbps in real time. The system employs wavelength multiplexing in order to run over only a single optical fibre. Using fast gated InGaAs single photon detectors, we reliably distribute secret keys with a rate above 21 kbps over 25 km of optical fibre. We optimized the system considering a security analysis that respects finite-key-size effects, authentication costs and system errors for a security parameter of εQKD = 4 × 10−9.

Transmission of O-band wavelength-division-multiplexed heralded photons over a noise-corrupted optical fiber channel

We transmitted O-band heralded photons over 10 km of optical fiber in a proof-of-concept experiment demonstrating the feasibility of using heralded photons to improve the noise tolerance of quantum key distribution. In our experiment, the optical fiber channel was corrupted by noise photons to the extent that if we had used an attenuated laser as the photon source, a photon signal-to-noise ratio of < 4.0 at the receiver, corresponding to a quantum bit-error rate of > 10.0%, would have prevented the effective generation of secure keys. Using a photon heralding scheme, the photon signal-to-noise ratio in our experiment was shown to be > 7.8. This corresponds to a quantum bit-error rate of < 5.7%, which is good enough for distilling secure keys. In addition, we showed that it is possible to incorporate wavelength-division-multiplexing into the photon heralding scheme to improve overall key rate. We discussed and clarified the prospects and limitations of the photon heralding scheme for noise-tolerant quantum key distribution.

Entanglement distribution over 300 km of fiber

We report the distribution of time-bin entangled photon pairs over 300 km of optical fiber. We realized this by using a high-speed and high signal-to-noise ratio entanglement generation/evaluation setup that consists of periodically poled lithium niobate waveguides and superconducting single photon detectors. The observed two-photon interference fringes exhibited a visibility of 84%. We confirmed the violation of Bell's inequality by 2.9 standard deviations.

Feasibility Study and Experimental Verification of Simplified Fiber-Supported 60-GHz Picocell Mobile Backhaul Links

We propose and experimentally demonstrate a fiber-wireless transmission system for optimized delivery of 60-GHz radio frequency (RF) signals through picocell mobile backhaul connections. We identify advantages of 60-GHz links for utilization in short-range mobile backhaul through feasibility analysis and comparison with an alternative E-band (60-90 GHz) technology. The 60-GHz fiber-wireless-fiber setup is then introduced: two spans of up to 20 km of optical fiber are deployed and bridged by up to 4 m of wireless distance. The 60-GHz radio-over-fiber technology is utilized in the first span of fiber transmission. The system is simplified and tailored for delivery of on-off keying data signals by employing a single module for lightwave generation and modulation combined with a simplified RF downconversion technique by envelope detection. Data signals of 1.25 Gb/s are transmitted, and a bit-error-rate performance below the 7% overhead forward-error-correction limit is achieved for a range of potential fiber deployment scenarios. A spurious free dynamic range of 73 dB-Hz2/3 is attained for a frequency-doubling photonic RF upconversion technique. The power budget margin that is required to extend the wireless transmission distance from 4 m to a few hundred meters has been taken into account in the setup design, and the techniques to extend the wireless distance are analyzed.

Phase-conjugated twin waves for communication beyond the Kerr nonlinearity limit

The transmission of a pair of phase-conjugated beams is shown to mitigate nonlinear distortion during optical fibre communication, allowing a 400 Gbit s−1 superchannel to be sent over 12,800 km of optical fibre.

Optical time domain reflectometry with low noise waveguide-coupled superconducting nanowire single-photon detectors

We demonstrate optical time domain reflectometry over 200 km of optical fiber using low-noise NbTiN superconducting single-photon detectors integrated with Si3N4 waveguides. Our small detector footprint enables high timing resolution of 50 ps and a dark count rate of 3 Hz with unshielded fibers, allowing for identification of defects along the fiber over a dynamic range of 37.4 dB. Photons scattered and reflected back from the fiber under test can be detected in free-running mode without showing dead zones or other impairments often encountered in semiconductor photon-counting optical time domain reflectometers.

Experimental demonstration of long-distance continuous-variable quantum key distribution

Distributing secret keys with information-theoretic security is arguably one of the most important achievements of the field of quantum information processing and communications. The rapid progress in this field has enabled quantum key distribution (QKD) in real-world conditions and commercial devices are now readily available. QKD systems based on continuous variables present the major advantage that they only require standard telecommunication technology, and in particular, that they do not use photon counters. However, these systems were considered up till now unsuitable for long-distance communication. Here, we overcome all previous limitations and demonstrate for the first time continuous-variable quantum key distribution over 80 km of optical fibre. The demonstration includes all aspects of a practical scenario, with real-time generation of secret keys, stable operation in a regular environment, and use of finite-size data blocks for secret information computation and key distillation. Our results correspond to an implementation guaranteeing the strongest level of security for QKD reported to date for such long distances and pave the way to practical applications of secure quantum communications.

ElectroAbsorption Modulated Laser Integrated with a Semiconductor Optical Amplifier for 100-km 10.3 Gb/s Dispersion-Penalty-Free Transmission

We report, for the first time, a transmission experiment over standard fiber at 1.55 μ m using an electroabsorption modulated laser (EML) integrated with a semiconductor optical amplifier (SOA). We show clearly that negative pre-chirped signals can be obtained by adjusting both modulator and amplifier driving parameters. Negative chirp operation is evaluated through small-signal chirp measurement as well as through time-resolved dynamic chirp measurement. Signal chirp control at emission enhances transmission and increases optical reach. Thanks to the SOA gain and chirp compensation for modulator loss and chirp, dispersion-penalty-free with clear open eye diagrams over 100 km of optical fiber at 10.3 Gb/s is achieved. A transmission up to 125 km is also obtained. This novel fully integrated EML-SOA is very promising as a high-performance, compact and low-cost optical transmitter for the future access-metropolitan network convergence.

Real-time ultra-wideband video streaming in long-reach passive optical networks with wireless radiation in the 10 and 60 GHz Bands

Real-time video streaming using ultra-wideband (UWB) technology is experimentally demonstrated along long-reach passive optical networks (LR-PONs) with different wired and wireless reaches. Experimental tests using external and direct modulation with UWB wireless radiation in the 10- and 60-GHz bands are performed. An ultra-bendable fiber is also considered for a last-mile distribution. The video quality at the output of the optical fiber infrastructure of the LR-PON is assessed using the error vector magnitude (EVM), and the link quality indicator (LQI) is used as a figure of merit after wireless radiation. An EVM below -17 dB is achieved for both externally and directly modulated LR-PONs comprising up to 125 km of optical fiber. EVM improvement is observed for longer LR-PONs when directly modulated lasers (DMLs) are used because of the amplitude gain provided by the combined effect of dispersion and DML's chirp. Compared with optical back-to-back operation, the LQI level degrades to the maximum around 20% for LR-PONs ranging between 75 and 125 km of fiber reach and with a wireless coverage of 2 m in the 10-GHz UWB band. The same level of LQI degradation is observed using the 60-GHz UWB band with a LR-PON integrating 101 km of access network, a last-mile distribution using ultra-bendable fiber, and a 5.2-m wireless link.

Coherent Radio-Over-Fiber and Millimeter-Wave Radio Seamless Transmission System for Resilient Access Networks

We propose a millimeter-wave (MMW) coherent radio-over-fiber (RoF) transmission system for application to an access network with a direct broadband last-mile wireless connection to an optical fiber network. The coherent RoF system comprises an optical two-tone RoF signal generator with an advanced modulation format for high-throughput transmission and employs a digital-signal-processing-aided coherent detection technique for MMW radio, which is a technique similar to that of optical digital coherent detection. As proof of concept, a 20-GBd quadrature phase-shift keying RoF transmission over 20 km of optical fiber before a radio transmission over 20 m of air is demonstrated. The results of the radio transmissions using Cassegrain-type antenna pairs with a gain of 50 dBi are consistent with theoretical estimations; this suggests the possibility of developing a midrange transmission system using a high-power MMW amplifier.

Optical Switching for Dynamic Distribution of Wireless-Over-Fiber Signals in Active Optical Networks

In this paper, we report on an experimental validation of dynamic distribution of wireless-over-fiber by employing optical switching using semiconductor optical amplifiers; we also provide a channel distribution scheme and a generic topology for such an optical switch. The experiment consists of a four wavelength-division-multiplexed channel system operating on a WiMax frequency band and employing an orthogonal-frequency-division-multiplexing modulation at 625&#x00A0;Mbits/s per channel, transmission of the data over 20&#x00A0;km of optical fiber, and active switching in a 1&#x00A0;&#x00D7;&#x00A0;16 active optical switch. The results show a negligible power penalty on each channel for both the best and the worst case in terms of inter-channel crosstalk. The presented system is highly scalable both in terms of port count and throughput, a desirable feature in highly branched access networks, and is modulation- and frequency-band independent.

Arbitrarily Loss-Tolerant Einstein-Podolsky-Rosen Steering Allowing a Demonstration over 1 km of Optical Fiber with No Detection Loophole

Demonstrating nonclassical effects over longer and longer distances is essential for both quantum technology and fundamental science. The main challenge is loss of photons during propagation, because considering only those cases where photons are detected opens a "detection loophole" in security whenever parties or devices are untrusted. Einstein-Podolsky-Rosen (EPR) steering is equivalent to an entanglement-verification task in which one party (device) is untrusted. We derive arbitrarily loss-tolerant tests, enabling us to perform a detection-loophole-free demonstration of EPR-steering with parties separated by a coiled 1 km optical fiber, with a total loss of 8.9 dB (87%).