Efficient Power‐Saving 10‐Gb/s ONU Using Uplink Usage‐Dependent Sleep Mode Control Algorithm in WDM‐PON

We propose and demonstrate an efficient power‐saving optical network unit (ONU) based on upstream traffic monitoring for 10‐Gb/s wavelength division multiplexed passive optical networks (WDM‐PONs). The power‐saving mode controller uses a μ‐processor and traffic monitoring modules followed by the proposed power‐saving processes to operate the sleep mode ONU. The power consumption of the ONU is effectively reduced from 19.3 W to 6.4 W when no traffic from the users is detected. In addition, we design a power‐saving mechanism based on a cyclic sleep mode operation to allow a connectivity check between the optical line terminal and ONU. Our calculation results show that the WDM‐PON ONU reduces the power consumption by around 60% using the proposed mechanism.     

Effects of Upstream Incoherent Crosstalk Caused by ASE Noise from Tx‐Disabled ONUs in XG‐PONs and TWDM‐PONs

A large incoherent crosstalk (IC) caused by amplified spontaneous emission (ASE) noise power from Tx‐disabled optical network units and a differential path loss has been shown to degrade upstream transmission performance in time‐division multiplexing passive optical networks. This paper considers the IC‐induced power penalty of an upstream signal both in an XG‐PON and in a TWDM‐PON. We investigate the degradation of the extinction ratio and relative intensity noise through a simulation and experiments. For the XG‐PON case, we observe a 9.6 dB difference in the level of ASE noise power from Tx‐disabled ONUs (hereafter known simply as ASE noise) between our result and the ITU‐T XG‐PON PMD recommendation. We propose an optical filtering method to mitigate an IC‐induced power penalty. In the TWDM‐PON case, the IC‐induced power penalty is naturally negligible because the ASE noise is filtered by a wavelength multiplexer at the optical line terminal. The results provide design guidelines for the level of ASE noise in both XG‐PONs and TWDM‐PONs.     

Low‐Cost,Low‐Power,High‐Capacity 3R OEO‐Type Reach Extender for a Long‐Reach TDMA‐PON

This paper proposes a low‐cost, low‐power, and high‐capacity optical‐electrical‐optical‐type reach extender that can provide 3R frame regeneration and remote management to increase the reach and split ratio with no change to a legacy time division multiple access passive optical network. To provide remote management, the extender gathers information regarding optical transceivers and link status per port and then transmits to a service provider using a simple network management protocol agent. The extender can also apply to an Ethernet passive optical network (E‐PON) or a gigabit‐capable PON (G‐PON) by remote control. In a G‐PON, in particular, it can provide burst mode signal retiming and burst‐to‐continuous mode conversion at the upstream path through a G‐PON transmission convergence frame adaptor. Our proposed reach extender is based on the quad‐port architecture for cost‐effective design and can accommodate both the physical reach of 60 km and the 512 split ratios in a G‐PON and the physical reach of 80 km and the 256 split ratios in an E‐PON.     

Demonstration of RSOA‐Based 20 Gb/s Linear Bus WDM‐PON with Simple Optical Add‐Drop Node Structure

We demonstrate a linear bus wavelength‐reused gigabit wavelength‐division multiplexing passive optical network (WDM‐PON) with multiple optical add‐drop nodes. A commercially available reflective semiconductor optical amplifier‐based WDM‐PON has a sufficient power budget to provide multiple optical add/drop nodes in 16 WDM channels. Sixteen 1.25 Gb/s WDM channels are successfully transmitted over 20 km of single‐mode fiber with four optical add/drop multiplexers, even with 32 dB reflection and chromatic dispersion in the link.     

Design of a Cost‐Effective Hybrid‐Type PBEx Providing a High Power Budget in an Asymmetric 10G‐EPON

This paper proposes a cost‐effective hybrid‐type power budget extender (PBEx) that can provide a high power budget of over 45 dB in an asymmetric 10‐Gb/s Ethernet passive optical network (10/1G‐EPON). The hybrid‐type 10/1G‐EPON PBEx comprises a central office terminal (COT) and remote terminal (RT) module supporting four channels and uses a coarse wavelength division multiplexing (CWDM) technology between the COT and RT for a reduction of fiber cost and efficient access network design. The proposed 10/1G‐EPON PBEx can provide over a 40‐km reach and 128‐way split per CWDM wavelength with no modification of a legacy 10/1G‐EPON system and can satisfy the error‐free service in 10¹⁰ packet transmission.     

A New Automatic Compensation Network for System‐on‐Chip Transceivers

This paper proposes a new automatic compensation network (ACN) for a system‐on‐chip (SoC) transceiver. We built a 5 GHz low noise amplifier (LNA) with an on‐chip ACN using 0.18 µm SiGe technology. This network is extremely useful for today's radio frequency (RF) integrated circuit devices in a complete RF transceiver environment. The network comprises an RF design‐for‐testability (DFT) circuit, capacitor mirror banks, and a digital signal processor. The RF DFT circuit consists of a test amplifier and RF peak detectors. The RF DFT circuit helps the network to provide DC output voltages, which makes the compensation network automatic. The proposed technique utilizes output DC voltage measurements and these measured values are translated into the LNA specifications such as input impedance, gain, and noise figure using the developed mathematical equations. The ACN automatically adjusts the performance of the 5 GHz LNA with the processor in the SoC transceiver when the LNA goes out of the normal range of operation. The ACN compensates abnormal operation due to unusual thermal variation or unusual process variation. The ACN is simple, inexpensive and suitable for a complete RF transceiver environment.     

Two‐Stage Resource Allocation to Improve Utilization of Synchronous OFDM‐PON Supporting Service Differentiation

We propose a two‐stage resource allocation algorithm for the high link utilization of an orthogonal frequency‐division multiplexing passive optical network (OFDM‐PON). An OFDM‐PON is assumed to use a synchronous frame structure in supporting service differentiation. In distributing resources, the proposed algorithm first allocates a time window for each optical network unit (ONU), and then it arranges a subchannel, which is a group of subcarriers. This algorithm needs to satisfy two constraints. First, computations for the resource allocation should be done using a frame unit. Second, an ONU has to use a single subchannel to send upstream data for multiple services within a frame duration. We show through a computer simulation that the proposed algorithm improves the link utilization.     

Physical Media Dependent Prototype for 10‐Gigabit‐Capable PON OLT

In this work, we study the physical layer solutions for 10‐gigabit‐capable passive optical networks (PONs), particularly for an optical link terminal (OLT) including a 10‐Gbit/s electroabsorption modulated laser (EML) and a 2.5‐Gbit/s burst mode receiver (BM‐Rx) in a novel bidirectional optical subassembly (BOSA). As unique features, a bidirectional mini‐flat package and a 9‐pin TO package are developed for a 10‐gigabit‐capable PON OLT BOSA composed of a 1,577‐nm EML and a 1,270‐nm avalanche photodiode BM‐Rx, including a single‐chip burst mode integrated circuit that is integrated with a transimpedance and limiting amplifier. In the developed prototype, the 10‐Gbit/s transmitter and 2.5‐Gbit/s receiver characteristics are evaluated and compared with the physical media dependent (PMD) specifications in ITU‐T G.987.2 for XG‐PON1. By conducting the 10‐Gbit/s downstream and 2.5‐Gbit/s upstream transmission experiments, we verify that the developed 10‐gigabit‐capable PON PMD prototype can operate for extended network coverage of up to a 40‐km fiber reach.     

A mode transformation algorithm based on traffic prediction in virtual multi‐OLT PON

In this paper, a mode transformation algorithm based on traffic prediction in virtual multiple optical line terminal (OLT) passive optical network (PON) is proposed. By proposing exponential smoothing algorithm based on weight update (WU‐ESA), user traffic is predicted well. WU‐ESA is a combination of two algorithms: exponential smoothing algorithm (ESA) and genetic algorithm (GA). The weight in ESA is optimized by GA based on real‐number encoding. By setting two periods, GA part and ESA part can be separated effectively. By presenting elastic packing algorithm (EPA), the load balance problem in virtual multi‐OLT PON is solved. EPA is implemented based on WU‐ESA. By the simulation and analysis, the effectiveness of the proposed algorithms is demonstrated. Compared with traditional mode transformation algorithm, EPA shows good performances in delay, throughput, and packet loss. Compared with traditional mode transformation algorithm, the EPA makes the packet loss decrease by at least 5% when the system load is greater than 0.9. Meanwhile, the delay of the two subsystems can be kept at a relatively balanced level by the implement of EPA. For throughput, the use of EPA improves the throughput by 20% when the system load is high.     

Effects of Upstream Bit Rate on a Wavelength‐Remodulated WDM‐PON Based on Manchester or Inverse‐Return‐to‐Zero Coding

We compare the performance of a wavelength remodulated wavelength‐division‐multiplexed passive optical network implemented using Manchester‐coded or inverse‐return‐to‐zero (IRZ)‐coded signal downstream and non‐return‐to‐zero remodulated signal upstream. We investigate the effects of varying differences between downstream and upstream bit rates on the two coding schemes. When the bit rate ratio of upstream to downstream is less than or equal to 50%, the performance of Manchester coding is better than that of IRZ coding. However, when the bit rate ratio of upstream to downstream is higher than 50%, Manchester code requires appropriate time delay between upstream and downstream signals, whereas IRZ code needs reduced extinction ratio in the downstream signal.     

MMSE‐based transceiver design for distributed MIMO amplify‐and‐forward cooperative networks in correlated channels

In this paper, the source‐precoder, multiple‐relay amplifying matrices, and destination‐equalizer joint optimization is investigated in distributed MIMO amplify‐and‐forward multiple‐relay networks with direct source–destination transmission in correlated fading channels. With the use of taking both the direct link and spatial correlation between antenna elements into account, the cooperative transceiver joint design is developed based on the minimum mean‐squared error criterion under individual power constraints at the source and multiple‐relay nodes. Simulation results demonstrate that the cooperative transceiver joint design architecture for an amplify‐and‐forward MIMO multiple‐relay system outperforms substantially the noncooperative transceiver design techniques on the BER performance under the spatial‐correlation channels.Copyright © 2012 John Wiley & Sons, Ltd.     

An All‐Optical Gain‐Controlled Amplifier for Bidirectional Transmission

A novel all‐optical gain‐controlled (AOGC) bidirectional amplifier is proposed and demonstrated in a compact structure. The AOGC function using fiber Bragg grating (FBG) pairs controls both directional signals independently, and combinations of optical interleavers and isolators suppress Rayleigh backscattering (RB) noise. The amplifier achieves high and constant gain with a wide dynamic input signal range and low noise figure. The performance does not depend on the input signal conditions, whether static‐state or transient signals, or whether there is symmetric or asymmetric data traffic on bidirectional transmission. Transmission comparison experiments between invariable symmetrical and random variable asymmetric bidirectional data traffic verify that the all‐optical gain control and bidirectional amplification functions are successfully combined into this proposed amplifier.     

Bidirectional Hybrid DWDM‐PON for HDTV/Gigabit Ethernet/CATV Applications

A new scheme for bi‐directional HDTV/Gigabit Ethernet/CATV transmission over a hybrid dense‐wavelength‐division‐multiplexing passive optical network (DWDM‐PON) is proposed and demonstrated. It is based on injection‐locked vertical‐cavity surface‐emitting lasers and distributed‐feedback laser diodes as transmitters. Services with 129 HDTV channels, a 1.25 Gbps Gigabit Ethernet connection, and 77 CATV channels are successfully demonstrated over 40 km single‐mode fiber links. Good performance of bit error rate, carrier‐to‐noise ratio, composite second order, and composite triple beat is achieved in our proposed bidirectional DWDM‐PON.     

Noise Suppression of Spectrum‐Sliced WDM‐PON Light Sources Using FP‐LD

We improved the performance of the spectrum‐sliced light source for wavelength‐division‐multiplexed passive optical networks by employing a Fabry‐Perot laser diode (FP‐LD). We found that FP‐LDs can suppress the intensity noise as significantly as using a gain‐saturated semiconductor optical amplifier. The transmission characteristics were measured and analyzed both with and without employing an FP‐LD.     

Memristive Logic‐in‐Memory Integrated Circuits for Energy‐Efficient Flexible Electronics

A memristive nonvolatile logic‐in‐memory circuit can provide a novel energy‐efficient computing architecture for battery‐powered flexible electronics. However, the cell‐to‐cell interference existing in the memristor crossbar array impedes both the reading process and parallel computing. Here, it is demonstrated that integration of an amorphous In‐Zn‐Sn‐O (a‐IZTO) semiconductor‐based selector (1S) device and a poly(1,3,5‐trivinyl‐1,3,5‐trimethyl cyclotrisiloxane) (pV3D3)‐based memristor (1M) on a flexible substrate can overcome these problems. The developed a‐IZTO‐based selector device, having a Pd/a‐IZTO/Pd structure, exhibits nonlinear current–voltage (I–V) characteristics with outstanding stability against electrical and mechanical stresses. Its underlying conduction mechanism is systematically determined via the temperature‐dependent I–V characteristics. The flexible one‐selector?one‐memristor (1S–1M) array exhibits reliable electrical characteristics and significant leakage current suppression. Furthermore, single‐instruction multiple‐data (SIMD), the foundation of parallel computing, is successfully implemented by performing NOT and NOR gates over multiple rows within the 1S–1M array. The results presented here will pave the way for development of a flexible nonvolatile logic‐in‐memory circuit for energy‐efficient flexible electronics.     

Frequency shift filter‐based multi‐carrier transceiver

It is well known that orthogonal frequency division multiplexing (OFDM) is sensitive to carrier frequency offset (CFO) and suffers from a high peak‐to‐average ratio. In addition, the performance of OFDM is severely affected by strong co‐channel interference and strong narrowband interference. To mitigate the limitations of OFDM, we propose a new multi‐carrier transceiver based on frequency‐shift filter. A frequency‐shift filter can separate spectrally overlapping sub‐carrier signals by exploiting the spectral correlation inherent in the cyclostationary modulated signals. To increase spectral efficiency, we increase the percentage of spectral overlap between two adjacent sub‐channels. We derive an upper bound and a lower bound on the bit error rate performance of the proposed multi‐carrier transceiver in additive white Gaussian noise channel and frequency‐nonselective Rayleigh fading channel, respectively. Compared with OFDM, our simulation results show that the proposed multi‐carrier transceiver is much less sensitive to CFO and has a lower peak‐to‐average ratio; moreover, without any additional interference suppression technique, the proposed transceiver has the advantage of being able to mitigate strong co‐channel interference with CFO from the intended multi‐carrier signal and mitigate strong narrowband interference in additive white Gaussian noise channel and in Rayleigh fading channel in which a large CFO between the transmitted signal and the received signal often occurs. Copyright © 2011 John Wiley & Sons, Ltd.     

Compact 2.5 Gb/s Burst‐Mode Receiver with Optimum APD Gain for XG‐PON1 and GPON Applications

This letter presents a compact 2.5 Gb/s burst‐mode receiver using the first reported monolithic amplifier IC developed with 0.25 …m SiGe BiCMOS technology. With optimum avalanche photodiode gain, the receiver module can obtain a fast response, high sensitivity and wide dynamic range, satisfying the overhead timing and various power specifications for a 2.5 Gb/s next‐generation passive optical network (PON), as well as a legacy 1.25 Gb/s PON in the upstream.     

Next‐generation global satellite system with mega‐constellations

Mega satellite constellations in low earth orbit (LEO) will provide complete global coverage; rapidly enhance overall capacity, even for unserved areas; and improve the quality of service (QoS) possible with lower signal propagation delays. Complemented by medium earth orbit (MEO) and geostationary earth orbit (GEO) satellites and terrestrial network components under a hybrid communications architecture, these constellations will enable universal 5G service across the world while supporting diverse 5G use cases. With an unobstructed line‐of‐sight visibility of approximately 3 min, a typical LEO satellite requires efficient user terminal (UT), satellite, gateway, and intersatellite link handovers. A comprehensive mobility design for mega‐constellations involves cost‐effective space and ground phased‐array antennas for responsive and seamless tracking. An end‐to‐end multilayer protocol architecture spanning space and terrestrial technologies can be used to analyze and ensure QoS and mobility. A scalable routing and traffic engineering design based on software‐defined networking adequately handles continuous variability in network topology, differentiated user demands, and traffic transport in both temporal and spatial dimensions. The space‐based networks involving mega‐constellations will be better integrated with their terrestrial counterparts by fully leveraging the multilayer 5G framework, which is the foundational feature of our hybrid architecture.     

Intra‐spacecraft optical communication solutions using discrete transceiver

The ever‐decreasing size of the small satellites with more demanding payloads has opened new research areas to investigate innovative onboard data‐handling solutions. This paper presents the use of optical intra‐satellite communication using discretely designed transceivers. The transceiver can handle large variations in the received photocurrents and implements filtration against the ambient light. The designed transceiver has been tested with selected optical components including infrared diodes, photo detectors, and optical guides to validate its functionality. The displacement damage testing on selected optical components was performed to validate their suitability for use in space. The experimental communication schemes have been presented for free space as well as glass fiber‐based intra‐spacecraft communication.     

Bidirectional Artificial Neural Networks for Mobile‐Phone Fraud Detection

We propose a system for mobile‐phone fraud detection based on a bidirectional artificial neural network (bi‐ANN). The key advantage of such a system is the ability to detect fraud not only by offline processing of call detail records (CDR), but also in real time. The core of the system is a bi‐ANN that predicts the behavior of individual mobile‐phone users. We determined that the bi‐ANN is capable of predicting complex time series (Call_Duration parameter) that are stored in the CDR.