Experimental Demonstration of Local Quasi-TEM Gap Modes in Single-Hard-Wall Waveguides

This letter reports an experimental study of a gap waveguide which is able to support a plurality of degenerate local quasi-TEM modes. No sidewalls are needed to separate these modes, which is a very useful property in the upper microwave and millimeter-wave bands. The waveguiding media is formed in the gap between a conducting plate and a hard surface. The working principle is described first. Next a practical realization is explained and tested experimentally.      

Experimental Demonstration of a Holographic Demultiplexer With Low Polarization-Dependence Loss Using a Long-Period Diffraction Grating

We describe the results of a holographic demultiplexer (DeMux) focused on the low polarization-dependence loss (PDL) using long-period volumetric diffraction grating. A 0.8-nm-spaced 21-channel holographic DeMux with PDL of less than -0.38 dB, channel uniformity of 0.495 dB, and channel crosstalk of -13 dB has been demonstrated     

Demonstration of a WDM/TDM hybrid PON based on a colorless frame-level reach extender

We propose a hybrid passive optical network (PON) consisting of a 2.5 Gb/s reflective semiconductor optical amplifier (RSOA)-based 32 channel loopback wavelength division multiplexing-passive optical network (WDM–PON) and a colorless OEO-based frame-level reach extender (RE). This hybrid PON is designed to support a 128-way split over a 50 km transmission distance per single wavelength channel. We experimentally demonstrate the feasibility of this design through downstream and upstream packet transmission with a commercial gigabit-capable PON (GPON) product. Even if the colorless frame-level RE uses active devices at the remote node, it is still possible to increase the optical link budget through backward compatibility with existing GPON products. This design also provides wavelength conversion and an upstream burst-to-continuous mode conversion between the WDM–PON and GPON. The proposed hybrid PON can satisfy a packet loss ratio (PLR) of 10^?10 at the downstream and upstream transmission including the use of forward error correction (FEC).     

Experimental Demonstration of All-Optical Analog-to-Digital Conversion With Balanced Detection Threshold Scheme

A novel balanced detection threshold scheme for all-optical analog-to-digital conversion is experimentally demonstrated. A 4-bit 10-GSamples/s all-optical analog-to-digital converter based on phase-shifted optical quantization and a balanced detection threshold scheme is realized to quantize a 9.9-GHz sinusoidal electrical signal, achieving a spur-free dynamic range of 24.2 dB. Compared with single-ended detection, the quantization result is improved with the balanced threshold scheme due to reducing the influence of the power fluctuation and improving the receiver sensitivity.      

Design of WDM PON With Tunable Lasers: The Upstream Scenario

Tunable lasers are potential upstream optical light generators for wavelength-division-multiplexing (WDM) passive optical network (PON), which is a promising solution for next-generation broad-band optical access. The wavelength provisioning flexibility of tunable lasers can increase the admissible traffic in the network as compared to wavelength-specific lasers. Generally, the broader the lasers' tuning ranges, the more the traffic can be admitted to the network. However, broad tuning range requires sophisticated technology, and probably high cost. To achieve the optimal tradeoff between the admissible traffic and the cost, we investigate the relationship between lasers' tuning ranges and the network's admissible traffic and then design WDM PON by selecting lasers with proper tuning ranges for the upstream data transmission. Specifically, we focus on addressing two issues under three scenarios. The two issues are: how to admit the largest traffic by properly selecting lasers, and how to admit given upstream traffic using lasers with tuning ranges as narrow as possible. The three scenarios are: full-range tunable and wavelength-specific lasers are available, limited-range tunable lasers are available, and the exact number of lasers with specific tuning ranges are given.      

Simulation Demonstration and Experimental Fabrication of a Multiple-Slot Waveguide

A multiple-slot waveguide is presented and demonstrated through theoretical simulation. Taking a double-slot waveguide as an example, the results show a nearly 30% enhancement of optical intensity compared with the traditional single-slot waveguide with the same slot gap width. Therefore, the E-field intensity of the slot can be increased by adding another smaller slot. A double-slot waveguide with oxide and air as low index slot materials is realized experimentally and the formation processes of the slots are analyzed.     

Experimental Demonstration of a Linearized Polymeric Directional Coupler Modulator

A linearized directional coupler modulator based on electrooptic polymer was fabricated and tested. The linearity was obtained by tailoring the coupling coefficient of the device using the photobleaching technique. A two-tone test of the device was presented and it demonstrated an enhancement in intermodulation distortion compared to a Mach-Zehnder modulator.     

Experimental Demonstration of a Detection-Time-Bin-Shift Polarization Encoding Quantum Key Distribution System

Detection-time-bin-shift (DTBS) is a scheme that uses time division multiplexing of a single photon detector between two photon bases in a quantum key distribution (QKD) system. This scheme can simplify the structure of a QKD system, reduce its cost and overcome the security problems caused by the dead-time induced self-correlation and the unbalanced characteristics of detectors. In this paper, we introduce an improved DTBS scheme and implement it based on our previously developed conventional fiber-based QKD system using the B92 protocol. Our DTBS QKD system generates sifted keys at a rate of more than 1 Mbit/s with a quantum bit error rate (QBER) lower than 2% over 1.1 km of fiber.     

Demonstration of a Bidirectional 80-km-Reach DWDM-PON With 8-Gb/s Capacity

A bidirectional 80-km-reach 64-channel dense wavelength-division-multiplexing passive optical network with 50-GHz channel spacing based on wavelength-locked Fabry-Peacuterot laser diodes is demonstrated. By changing the position of the broadband light source (BLS) for the upstream channels to the remote node, both the need for a high-power BLS and the power penalties induced by backscattering are overcome. Packet-loss-free transmission is obtained, guaranteeing 125 Mb/s per channel (8-Gb/s capacity in a single direction) without the support of an optical amplifier     

Enhancement of the Performance of a Reflective SOA-Based Hybrid WDM/TDM PON System With a Remotely Pumped Erbium-Doped Fiber Amplifier

A passive optical network (PON) architecture based on a hybrid wavelength-division multiplexing (WDM) and time-division multiplexing (TDM) PON system with a remotely pumped erbium-doped fiber amplifier (EDFA) is presented as an excellent candidate for use in a next-generation optical access network. The remotely pumped EDFA operates as a bidirectional amplifier and provides a 15-dB gain to both upstream signals and seed light sources, so the sensitivity of upstream transmission is greatly improved. An upstream transmission of 1.25 Gb/s with a low seed channel power of -14 dBm is made feasible over a total reach of 25 km for 32-WDM channels and 16-TDM splits by the use of the remotely pumped EDFA. This scheme has advantages that it uses a single transmission fiber for both down-and up-stream signals and that it reduces the Rayleigh scattering contribution.     

Low Voltage Ride Through of Wind Farms With Cage Generators: STATCOM Versus SVC

This paper analyzes the extent to which the low voltage ride through (LVRT) capability of wind farms using squirrel cage generators can be enhanced by the use of a STATCOM, compared to the thyristor controlled static var compensator (SVC). The transient stability margin is proposed as the indicator of LVRT capability. A simplified analytical approach based on torque-slip characteristics is first proposed to quantify the effect of the STATCOM and the SVC on the transient stability margin. Results from experiments with a STATCOM and a 7.5 kW induction machine emulating a wind turbine are used to validate the suggested analytical approach. Further verifications based on detailed time-domain simulations are also provided. Calculations, simulations and measurements confirm how the increased STATCOM rating can provide an increased transient stability margin and thus enhanced LVRT capability. Compared to the SVC, the STATCOM gives a larger contribution to the transient margin as indicated by both calculations and simulations. The inaccuracies introduced by neglecting the flux transients in the suggested approach are discussed and found reasonable for an estimation method when considering the simplicity compared to detailed time-domain simulation studies. A method for estimating the required rating of different compensation devices to ensure stability after a fault is suggested based on the same approach.     

Demonstration of a Novel WDM Passive Optical Network Architecture With Source-Free Optical Network Units

A novel wavelength-division multiplexing passive optical network architecture with the capability to provide triple-play services (TPS) with a source-free optical network unit has been proposed and experimentally demonstrated. TPS provision with two 2.5-Gb/s, 10-Gb/s downstream signals and 10-Gb/s upstream signals per channel has been successfully realized     

Experimental Demonstration of Multipoint Temperature Warning Sensor Using a Multichannel Matched Fiber Bragg Grating

A novel time-division-multiplexing fiber Bragg grating (FBG) sensor for multipoint temperature warning sensor is proposed and demonstrated. A multiwavelength pulsed laser based on a multichannel matched FBG is employed. The sensor array consists of multiple uniform FBGs at different positions and with different nominal wavelengths. When the temperature exceeds the threshold at a certain position, the light at the corresponding time slot and wavelength can be detected. The sensor provides a simple and flexible solution to locate the abnormal temperature increase with different tolerable thresholds at different locations.     

Demonstration of 20-Gb/s DQPSK With a Single Dual-Drive Mach–Zehnder Modulator

Using a single, dual-drive Mach-Zehnder modulator and high-speed electronics, differential quadrature phase-shift keying modulation and detection are demonstrated for a bit rate of 20 Gb/s. Back-to-back system performance is measured, and the receiver sensitivity is found to be -32.25 dBm.     

Experimental Demonstration of a Hybrid Link for Mitigating Atmospheric Turbulence Effects in Free-Space Optical Communication

Atmospheric turbulence causes severe performance degradation in free-space optical communication links. However, by using a reliable low-bandwidth wireline or RF link in parallel, the performance of such links can be improved significantly. This is achieved by using error correction codes at the transmitter and decoding the received data jointly over the two links at the receiver. Our work describes the feasibility study of such a hybrid link. It is observed that a 10% use of the wireline link can result in more than 8-dB performance gain in the optical link.      

Experimental Demonstration and Characterization of a Tunable CRLH Delay Line System for Impulse/Continuous Wave

A new tunable delay system is presented and demonstrated experimentally in this letter. This system, which incorporates a composite right/left-handed (CRLH) transmission line, two mixers, and a low-pass filter, achieves a tunable group delay for impulse and continuous-wave signals, controlled by a local oscillator. This group delay tunability follows from the dispersion property of the CRLH transmission line and is achieved without suffering from the drawbacks of conventional delay lines in terms of matching, frequency of operation, and planar circuit implementation. The realized prototype exhibits measured group delays tunable between 5.1 and 8.54 ns over a frequency range of 2-4.5 GHz.     

Analysis of a Two-Hop Centralized Packet Radio Network--Part I: Slotted ALOHA

The design of packet radio systems involves a large number of design variables that interact in a very complex fashion. As this design problem in its general form is quite complex, a viable approach is to analyze some simple but typical configurations in an attempt to understand the behavior of these systems. In this paper, a two-hop centralized configuration is considered in which traffic originates at terminals, is destined to a central station, and requires for its transport the relaying of packets by store-and-forward repeaters. The through-put-delay performance is derived, and its dependence on such key system variables as the network topology, the transmission protocol, and the repeaters' storage capacities, is given. In this part, devices are assumed to be utilizing the slotted ALOHA access mode. Carrier sense multiple access is treated in Part II of this series [1].     

Myoelectric Signal Processing: Optimal Estimation Applied to Electromyography?Part II: Experimental Demonstration of Optimal Myoprocessor Performance

This paper (Part II of two) presents an experimental demonstration of the performance achieved by implementing the mathematically derived optimal myoprocessor described in Part I. Almost an order-of-magnitude improvement over the common myoprocessor is obtained. Excellent agreement of the experimental results with the analytical predictions verifies the mathematical analysis. The relative contributions of each stage of the optimal myoprocessor are examined. A discussion and comparison of several existing and proposed techniques for myoprocessor improvement are presented.     

Analysis of a Two-Hop Centralized Packet Radio Network--Part II: Carrier Sense Multiple Access

We continue in this paper our study of two-hop centralized packet radio networks in view of understanding the behavior of these systems. Traffic originates at terminals, is destined to a central station, and requires for its transport the relaying of packets by store-and-forward repeaters. We consider here that all devices employ the nonpersistent carrier sense multiple-access mode. System capacity and through-put-delay tradeoffs are derived and compared to those obtained for slotted ALOHA in Part I [l].