Full-duplex Transmission Research Articles

A 12.5+12.5 Gb/s Full-Duplex Plastic Waveguide Interconnect

A new interconnect solution with plastic waveguide is demonstrated. The system consists of a pair of transceivers and a plastic waveguide. Millimeter wave signal is transmitted in a low-cost long piece of solid plastic dielectric acting as a waveguide. The plastic waveguide medium offers a large bandwidth for data communication using mm-wave carrier frequencies. Plastic waveguide interconnects do not require costly electrical-to-optical and optical-to-electrical conversion devices or precise alignment and offer longer transmission distances than wireless solutions due to better field confinement and lower path loss. Multiple plastic waveguides can be used in parallel and the modulated data at different frequencies can be multiplexed to increase the data rate. The demonstrated transceiver chips operate at carrier frequencies of 57 GHz and 80 GHz, and are fabricated in 40 nm low-power logic CMOS. The total area and power consumption of two transceivers are 0.41 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 140 mW, respectively. The fabricated demonstrator with Yagi-couplers achieves full-duplex transmission of 12.5 Gb/s ASK modulated signal in each direction over the 120 mm polystyrene waveguide with no equalization. The observed bit error rates for both channels are less than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> for a PRBS length of 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> -1 at the total data rate of 25 Gb/s. This paper shows the feasibility of the plastic waveguide interconnect as a promising alternative to electrical, optical, and wireless interconnects.

An All-Optical Carrier Recovery Scheme for Access Networks With Simple ASK Modulation

We theoretically investigate and experimentally demonstrate a scheme for all-optical carrier recovery in loopback access networks that avoids orthogonal or complex modulation formats for the downstream or upstream signals. The applied technique is based on a passive resonating circuit that is capable of recovering the optical carrier of the amplitude-shift-keyed downstream signal for remodulation with a reflective modulator as upstream transmitter enabling full-duplex 10 Gb/s operation. The scheme is compared with alternative pattern suppression techniques based on optical gain saturation and electro-optical feed-forward injection for the stringent requirements of next-generation access networks, namely, an extended loss budget and high upstream data rates. Operation at downstream modulation depths of ∼3 dB is reported with the feed-forward approach, while higher modulation depths of up to 9 dB are demonstrated with the all-optical carrier recovery technique, for which the dependence on longer sequences of consecutive identical bits is investigated. Finally, the feasibility of the all-optical downstream cancelation technique for optical access networks is evaluated in a wavelength division multiplexed passive optical network, showing full-duplex transmission with margins of at least 9 dB.

Dual-Operability and Bandwidth Partitioning Enabled by an ONU With Tandem-Modulator

An upgrade at the physical layer regarding unbundling and dynamic bandwidth provisioning of a wavelength division multiplexed access network is presented. The capability of a reflective modulator to act as a photodetector is exploited and allows a tandem configuration to be used at the optical network unit (ONU) for flexible switching of the detection and modulation branch. Consequently, a mechanism for service operator selection and for dynamic bandwidth partitioning up to twice the nominal data rate is provided. The scheme is experimentally evaluated for different kinds of modulators and shows, together with a full-duplex transmission at 10 Gb/s, additional operation modes, featuring unidirectional downstream and upstream burst-mode transmission with up to 20 Gb/s for ONUs based on a combination of a semiconductor optical amplifier and a reflective electro-absorption modulator.

Experimental Demonstration of Multi-Service Hybrid Fiber-Radio System Using Digitized RF-Over-Fiber Technique

An efficient multi-channel hybrid fiber-radio scheme for both down and up-link paths is demonstrated based on digitized RF-over-fiber technique, where the frequency translation stages are implemented using a single analog-to-digital converter (ADC) and digital-to-analog converter (DAC) instead of mixers and local oscillators. The simultaneous transmission of GSM, UMTS and WiMAX services is demonstrated with error-free reception. With a minimum sampling rate of 50 MHz and an overall optical data rate of 400 Mb/s, all the three wireless services can be successfully recovered in a full-duplex transmission. In the downlink direction, the performance is dependent on the amount of amplification required for the wireless signal at the desired carrier frequency. The amount of amplification on the other hand is dependent on the location of the wireless signal within the Nyquist zone which increases significantly with the order of the Nyquist zone. In the uplink direction, the performance is limited by inter-channel interference as a result of spectra aliasing of the regenerated IF signals which limits the signal-to-noise-ratio. With proper system design that optimizes downlink amplification and minimizes inter-channel interference, simultaneous multi-service transmission using digitized RF-over-fiber technique is able to improve spectral efficiency and minimize hardware count.

High Customer Density PON With Passive Amplification Through Distributed Pump for ${&gt;}$1:1000 Tree Split

A network architecture for tree-like passive optical networks (PONs) with high splitting ratios is proposed and experimentally demonstrated. Splits >;1000 are shown to be feasible thanks to a noise-powered amplifier that is built-in inside the power splitter. The proposed noise pumping technique recycles the natural amplified spontaneous emission (ASE) of a semiconductor optical amplifier at the customer premises, avoiding the use of an electrical power supply in the fiber plant. The impact of the location of this noise-powered extender box inside the signal distribution element of the tree is analyzed in terms of obtained signal gain, ASE accumulation among multiple extender boxes, and transmission performance. Finally, full-duplex transmission at 10 Gb/s with burst-mode upstream is demonstrated in a particular scenario with a split of 1:1000 and a loss budget of 39.5 dB, revealing that power margins of >;3 dB can be provided.

Remotely Pumped Long-Reach Hybrid PON With Wavelength Reuse in RSOA-Based ONUs

Symmetrical full-duplex transmission in a Passive Optical Network (PON) is demonstrated over a 100 km dual-fiber ring with 1:16 split trees. The customer premises equipment is based on a Reflective Semiconductor Optical Amplifier (RSOA), which reuses the wavelength of the intensity modulated downstream signal for upstream data transmission. A commercial RSOA was used together with optical offset filtering at the upstream receiver to operate at data rates of 5 and 10 Gb/s. Margins of >; 8 dB are left at a data rate of 5 Gb/s, proving that the utilized downstream suppression scheme and therefore the intensity modulation format for both, down- and upstream, is suitable for its application in long-reach hybrid access networks. The signal degradation along the PON and the transmitted pump that features means of remote amplification in its conjunction points between the metro ring and the local trees are discussed and further possibilities for an improvement of the transmission performance are proposed.

一种基于反射型半导体光放大器和迈克逊干涉仪的无色远端节点的设计和分析

A scheme of flexible colorless remote note with reflective semiconductor optical amplifier (RSOA) assisted Michelson interferometer is proposed. This is capable of generating an optical carrier suppressed signal at a specific radio frequency to suppress the penalty brought about by Rayleigh backscattering and reflection in a full-duplex single fiber transmission network. Simulations are conducted, and the validation of the proposal is discussed by observing the penalty eye opening factor. The results are useful for designing cost-effective multi-wavelength passive optical network (PON) or radio-over-fiber (RoF) systems.

Rayleigh Scattering Tolerant PON Assisted by Four-Wave Mixing in SOA-based ONUs

A scheme for the mitigation of Rayleigh backscattering (RB) in hybrid passive optical networks (PON) is presented. Semiconductor optical amplifiers (SOA) of the optical network units (ONU) are advantageously used as nonlinear elements, exploiting Four-Wave Mixing (FWM) between the downstream signals to create a spectrally displaced optical upstream carrier. The proposed technique is experimentally proven in a long reach and high split PON, and the suppression of the pumps and further FWM products, obtained via a modified filtering scheme inside the PON, is analyzed. Full-duplex transmission at 10/2.5 Gb/s is demonstrated, showing that upstream transmission is possible despite low optical signal-to-RB ratios (OSRR) of ~ 12 dB.

Hierarchical modulation-based cooperation utilizing relay-assistant full-duplex diversity

In this paper, we present a hierarchical modulation-based cooperation (HMC) scheme to overcome capacity degradation due to half-duplex transmissions in conventional cooperative relay systems. In the HMC scheme, two relay terminals are used for both transmit and receive operations, i.e., full-duplex transmission. This scheme reduces the required number of time slots for cooperation. Utilizing this cooperative mechanism, the HMC scheme achieves cooperative diversity at the destination node by combining the signals delivered from the source and relay nodes. In addition, we derive a closed form of the end-to-end bit error rate for the HMC scheme, which is utilized to determine an optimal power ratio for hierarchical signals at the source node. In concurrence with the HMC scheme, we develop the best relay selection scheme for a practical wireless communication networks.

Converged delivery of WiMAX and wireline services over an extended reach passive optical access network

In this paper we present long-reach fiber access links supporting transmission of Worldwide Interoperability for Microwave Access (WiMAX) compliant signals. We present bi-directional full-duplex transmission of 256-state quadrature amplitude modulation (256-QAM) modulated WiMAX-compliant signals on a 2.4-GHz RF carrier over an 80-km long-reach access link at 100 Mb/s (down) and 64 Mb/s (up). Transmission of 64-QAM and 256-QAM-modulated signals on a 5.8-GHz RF carrier over a 118.8-km access link converged with four baseband differential quadrature phase shift keying (DQPSK) modulated wireline channels, along with ultra-wide band (UWB) and phase shift keying (PSK) radio-over-fiber (RoF) wireless signals over a deployed optical fiber link is also presented.

Design Characteristics for a Full-Duplex IM/IM Bidirectional Transmission at 10 Gb/s Using Low Bandwidth RSOA

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, the optimum design characteristics and the transmission performance limits of an intensity modulation full-duplex bidirectional transmission system at 10 Gb/s are experimentally studied and presented for application in next-generation-extended wavelength-division-multiplexed passive optical networks. A low-bandwidth (<formula formulatype="inline"><tex Notation="TeX">${\sim} {\hbox {1.2}}$</tex></formula> GHz) reflective semiconductor optical amplifier (RSOA) is utilized at the optical network unit (ONU) site of the system. Its remodulation properties and performance are examined for both continuous wave and modulated downstream signal, stemming from the optical line terminal (OLT). The techniques adopted to optimize performance are: 1) the use of detuned optical filtering at the OLT receiver that takes advantage of the RSOA chirp and 2) the use of decision feedback equalization (DFE). The extinction ratio of the downstream signal and the driving operation point of the RSOA are examined experimentally in order to find the optimum conditions for the bidirectional transmission. Moreover, the impact of patterning effects in the performance of the system is evaluated. Finally, the additional performance improvement that is achieved with the use of DFE technique is shown. </para>

A novel scheme to generate multiband millimeter wave signals for 40 GHz full duplex radio-over-fiber system

This paper proposes a new scheme to generate frequency-diversity binary phase shift keying (BPSK) signals for radio-over-fiber (RoF) system. As is well known, the frequency diversity technology has the anti frequency selective fading characteristic and RoF system is a practical solution to increase the capacity and mobility of future-proof contents delivery and serve both fixed and mobile users. In this paper, our proposal can generate 20 GHz and 40 GHz millimeter-wave (mm-wave) signals simultaneously with the data rate of 1.25 Gbit/s employing only one electrical optical phase modulator (EOPM) and one Mach-Zehnder modulator (MZM) at the central station. With one additional MZM at the base station, the full duplex transmission can be accomplished. As the downstream data is phase modulated, the optical signal can be re-used to load the upstream data and no laser diode (LD) is needed at the base station, which simplify the structure of the base station. The 20 GHz electrical carrier is also generated which can be used to demodulate the BPSK signal. The whole scheme can be used in the future duplex RoF system.

10 Gb/s full-duplex bidirectional transmission with RSOA-based ONU using detuned optical filtering and decision feedback equalization

Full-duplex bidirectional transmission at 10 Gb/s is demonstrated for extended wavelength division multiplexed passive optical network (WDM-PON) applications, achieving transmission distances up to 25 km of standard single mode fiber (SSMF) when using a low-bandwidth (approximately 1.2 GHz) reflective semiconductor optical amplifier (RSOA) for signal re-modulation at the optical network unit (ONU). The system is assisted by optimum offset filtering at the optical line terminal (OLT)-receiver and the performance is further improved with the use of decision-feedback equalization (DFE). Chromatic dispersion (CD) and Rayleigh Backscattering (RB) effects are considered and analyzed.

Constrained Adaptive Echo Cancellation for Discrete Multitone Systems

In communication systems where full-duplex transmission is required, echo cancellers are deployed to cancel the interference of the transmitted signal at the collocated receiver. For systems using discrete multitone (DMT) modulation, echo cancellation is performed partially in the time and frequency domains to decrease the processing complexity. In this paper, echo cancellation for DMT systems is reformulated as a constrained optimization problem, where a cost function is minimized over an extended linear space. This extended space contains the weights of the finite-impulse-response (FIR) filter emulating the echo channel in the time and the frequency domains, while linear constraints are used to ensure the proper mapping between these two domains. Based on this proposed formulation, a new constrained adaptive echo cancellation structure for DMT-based digital subscriber lines (DSL) systems is proposed. The proposed formulation provides a unifying framework for different practical DSL systems (i.e., frame asynchronous and multirate), as well as additional flexibility in implementation by allowing the incorporation of supplementary constraints that can improve the performance of the system. As an illustrative example, we show how the robustness of the echo canceller can be improved in the presence of radio frequency interference by adding appropriate constraints on the extended linear space.

Employing mutually injection-locked FP LDs scheme over full-duplex radio-on-fiber transport systems

A full-duplex radio-on-fiber (ROF) transport system based on mutually injection-locked Fabry-Perot laser diodes (FP LDs) as light source is proposed and demonstrated. Transmission performances over a 40-km standard single-mode fiber (SMF) for full-duplex transmission were investigated. Good performance of bit error rate (BER) was achieved in our proposed systems. We directly modulate the FP LDs in mutually injection-locked scheme instead of using expensive external modulator and sophisticated optical carrier suppression technique; it reveals an outstanding alternative with advantages in simplicity and cost.

Simultaneous Generation of Centralized Lightwaves and Double/Single Sideband Optical Millimeter-Wave Requiring Only Low-Frequency Local Oscillator Signals for Radio-Over-Fiber Systems

We have designed and experimentally demonstrated radio-over-fiber (ROF) systems to simultaneously generate optical millimeter-wave (mm-wave) and centralized lightwaves using one low-bandwidth intensity modulator (IM) with low-frequency local oscillator (LO) signals while simplifying the transmission design and reducing the cost of the base station (BS). The techniques based on double-sideband (DSB) and single-sideband (SSB) signals for ROF systems are discussed in detail in terms of architecture efficiency, bandwidth requirement, and fiber transmission performance. The repetitive frequency of the optical mm-wave carriers are four times of that of the LO in central office (CO) by using DSB scheme. Full-duplex transmission services have been successfully realized over 20-km single-mode fiber (SMF) based on wavelength-reuse technique. In order to mitigate chromatic dispersion, the SSB technique has also been investigated in this paper. We had realized an ROF system that attained dispersion-free transmission and a negative power penalty by using SSB generation. We also quantified the optical carrier-to-sideband ratio (CSR) of downstream transmission in this ROF link and established that the performance of ROF system can be significantly improved when the optical signals are transmitted at a CSR value of 0 dB. The proposed architectures require much less bandwidth of the modulators, receiver sensitivity, system operation efficiency, and reliability.

Full-Duplex 1.0 Gbit/s Data Transmission Over 60 GHz Radio-on-Fiber Access System Based on the Loop-Back Optical Heterodyne Technique

Full-duplex transmission over a 60 GHz radio-on-fiber access system based on the optical heterodyne technique is verified in this paper. With this technique, an optical carrier generator on the transmitting side consolidates the functions of wavelength and polarization control for optical heterodyne detection in uplinks and optical millimeter-wave generation in downlinks, on behalf of each optical transmitter/receiver. Therefore, the whole system configuration can be significantly simplified. A full-duplex 1.0 Gbit/s transmission experiment over 10 km of single-mode fiber, which represents an access network transmission, is demonstrated using the simultaneous modulation/photodetection operation of an electroabsorption modulator (EAM). Bit error rates of less than 10-9 were obtained in both the uplink and downlink without noticeable mutual interference, even though the laser source and the EAM is shared by both links, and no significant dispersion-induced degradation was observed. Moreover, the experimental results showed that an optical link budget of 9.2 dB can be achieved with the experimental configuration.

Full-duplex radio-over-fiber transport systems based on two modes injection-locked FP LD

A full-duplex radio-over-fiber (ROF) transport system based on two modes injection-locked Fabry–Perot laser diode (FP LD) is proposed and demonstrated. Performances over a 40-km standard single-mode fiber (SMF) full-duplex transmission were investigated. Good performances of bit error rate (BER) and error vector magnitude (EVM) were obtained in our proposed systems. Since our proposed systems use only one FP LD as light source for both down-link and up-link transmissions, it reveals a prominent alternative with advantages in simplicity and cost.

Research for a Emergency Medical Information Transmission System using High-Speed Downlink Packet Access

Objective: In this research, a full-duplex transmission system was developed in order to send real time medical information(i.e. patient vital signs, real-time patient video/audio data) using HSDPA(High-Speed Downlink Packet Access), a 3.5th generation mobile communication system. Methods: Transmission tests were conducted in an environment simulating that of the inside of a moving ambulance, transporting an emergency patient. The capability of the HSDPA system to transmit emergency medical information has been verified by comparing the prolonged cumulative data, calculating packet loss, and measuring transmission speed. Results: Test results show that the system is capable of transmitting vital signal data, including 12 waveform data, 20 numeric data and 113 events. This provides enough information needed for medical guidance, reading the affected part of the patient, and forwarding 320×420 pixel images at 2fps. Full-duplex voice transmission at 8bit/64kbps is enough to permit reliable communication between emergency medical technicians and hospital professionals. A total of 11.43 kilobytes were lost out of 81.25 megabytes. Therefore, the packet loss was 0.013%. Conclusion: The medical transmission system using HSDPA performs well in data transmission speed and communication quality during emergency medical transportation. It is also expected to further improve emergency medical conditions if supplementary systems such as the standard protocol establishment.

Call Admission Control in Wireless Ad-hoc Networks with Multiple Channels and Radios

In this paper, an Ad-hoc Routing Protocol that works in wireless Ad-hoc communication networks with multiple radios and multiple channels and that controls call admission based on bandwidth measurement is proposed. Unlike the conventional Ad-hoc node with a single radio using a single channel, an Ad-hoc node of the protocol proposed, the MCQosR(Multiple Channel Quality of Service Routing), has multiple radios and uses multiple channels, which allows full duplex transmission between wireless Ad-hoc nodes, and reduces intra interference on the route. Also, a fixed channel only for reception at each node enables the estimation of the available bandwidth, which is used to control the call admission for QoS provision. The performance of the MCQosR was verified by simulation.