Commercial Transponders Research Articles

Aiming for high-capacity multi-modal free-space optical transmission leveraging complete modal basis sets

Free-space optical (FSO) communication has gained much interest due to its capability of providing not only a cost-efficient solution where the optical fiber is too expensive or too difficult to deploy but also a much higher system capacity than its radio-frequency competitor. In addition to conventional polarization-division multiplexing and coherent detection, combining with mode-division multiplexing can unlock the full potential of FSO communications and achieve ultra-high spectral efficiency. In this paper, we review the recent progress of multi-modal FSO communication systems leveraging complete modal basis sets. Some practical issues for system design are discussed. We also present two latest demonstrations that achieved the record-high single-wavelength data rate using a commercial transponder and a pair of commercial multiplexer/demultiplexer for multi-modal FSO transmission without turbulence and in atmospheric turbulence, respectively, showing the potential of such a technique.

Enhanced Atmospheric Turbulence Resiliency With Successive Interference Cancellation DSP in Mode Division Multiplexing Free-Space Optical Links

We experimentally demonstrate the enhanced atmospheric turbulence resiliency in a 137.8 Gbit/s/mode mode-division multiplexing free-space optical communication link through the application of a successive interference cancellation digital signal processing algorithm. The turbulence resiliency is further enhanced through redundant receive channels in the mode-division multiplexing link. The proof of concept demonstration is performed using commercially available mode-selective photonic lanterns, a commercial transponder, and a spatial light modulator based turbulence emulator. In this link, 5 spatial modes with each mode carrying 34.46 GBaud dual-polarization quadrature phase shift keying signals are successfully transmitted with an average bit error rate lower than the hard-decision forward error correction limit. As a result, we achieved a record-high mode- and polarization-division multiplexing channel number of 10, a record-high line rate of 689.23 Gbit/s, and a record-high net spectral efficiency of 13.9 b/s/Hz in emulated turbulent links in a mode-division multiplexing free-space optical system.

Semiconductor optical amplifiers: recent advances and applications

Owing to advances in fabrication technology and device design, semiconductor optical amplifiers (SOAs) are evolving as a promising candidate for future optical coherent communication links. This review article focuses on the fundamentals and broad applications of SOAs, specifically for optical channels with advanced modulation formats, as an integrable broadband amplifier in commercial transponders and as a nonlinear medium for optical signal processing. We discuss the basic functioning of an SOA and distortions of coherent signals when SOAs are used as amplifiers. We first focus on the techniques used for low-distortion amplification of phase-modulated signals using SOAs. Then we discuss optical signal processing techniques enabled by SOAs with an emphasis on all-optical wavelength conversion, optical phase conjugation, and phase quantization of coherent optical signals.

Cybersecurity Attacks on Software Logic and Error Handling Within AIS Implementations: A Systematic Testing of Resilience

To increase situational awareness of maritime vessels and other entities and to enable their exchange of various information, the International Maritime Organization mandated the use of the Automatic Identification System (AIS) in 2004. The AIS is a self-reporting system that uses the VHF radio link. However, any radio-based self-reporting system is prone to forgery, especially in situations where authentication of the message is not designed into the architecture. As AIS was designed in the 1990s when cyberattacks were in their infancy, it does not implement authentication or encryption; thus, it can be seen as fundamentally vulnerable against cyberattacks. This paper demonstrates and evaluates the impact of multiple cyberattacks on AIS via remote radio frequency (RF) links using transmission-enabled software-defined radio (SDR). Overall, we implemented and tested a total of 11 different tests/attacks on 19 AIS setups, using a controlled environment. The tested configurations were derived from heterogeneous platforms such as Windows, Android, generic receivers, and commercial transponders. Our aim is to enhance the early discovery of new vulnerabilities in AIS to effectively address AIS attacks in the nearest future. The results showed that approximately 89% of the setups were affected by Denial-of-Service (DoS) attacks at the AIS protocol level. Besides implementing some existing attack ideas (e.g., spoofing, DoS, and flooding), we showed some novel attack concepts in the AIS context such as a coordinated attack, overwhelming alerts, and logical vulnerabilities, all of which have the potential to cause software/system crashes in the worst-case scenarios. Moreover, an implementation/specification flaw related to the AIS preamble was identified during the experiments, which may affect the interoperability of different AIS devices. The error-handling system in AIS was also investigated. Unlike the aviation sector’s Automatic Dependent Surveillance-Broadcast (ADS-B), the maritime sector’s AIS does not effectively support any error correction method, which may contribute to RF pollution and less effective use of the overall system. The consistency of our results for a comprehensive range of hardware-software configurations indicated the reliability of our approach, test system, and evaluation results.

Real-time optical transponder prototype with autonegotiation protocol for software defined networks

We present a prototype transponder with fast synchronized change of parameters in the case of traffic quality degradation thanks to link impairment detection and autonegotiation capabilities. This concept has been implemented and validated in real time using a field programmable gate array (FPGA) platform, a Raspberry Pi, and a commercial transponder. We introduce an autonegotiation protocol for local decision-making between two transponders. We measure the latency added by this protocol processing cores inside the FPGA. We then integrate this transponder prototype inside a network testbed, where we compare its performance in detecting and resolving a soft failure against a centralized software-defined network control and management plane. Our solution proves to be 2 times faster and shows less variability on average than a centralized one. This work is complementary to control plane decision-making and brings further flexibility with the idea in mind to promote wider use of reconfigurations toward close-to-zero-margin optical networks.

Screen-printed and spray coated graphene-based RFID transponders

We report ultra-high-frequency (UHF, 800 MHz–1 GHz) radio frequency identification (RFID) transponders consisting of printed dipole antennas combined with RFID microchips. These are fabricated on Kapton via screen printing and on paper via spray coating, using inks obtained via microfluidization of graphite. We introduce a hybrid antenna structure, where an Al loop (small compared to the overall size of the antenna) is connected to a microchip with the double function of matching the impedances of antenna and microchip and avoiding bonding between exfoliated graphite and chip. The transponders have reading distance ∼11 m at UHF RFID frequencies, larger than previously reported for graphene-based RFID and comparable with commercial transponders based on metallic antennas.

The Implementation of Sub-1GHz Wireless Personal Area Monitoring System

This paper presents the development of a brand new hardware framework of low-cost, tiny and power-efficient wireless monitoring system. The framework of this wireless personal area monitoring system (WPAMS) includes sub-1GHz RFID interrogator subsystem, antenna subsystem and passive RFID transponder subsystem. Compare to other interrogators, sub-1GHz interrogator achieves larger communication range and suffers fewer reflections in the indoor space. The sophisticated commercial transponder can be easily embedded in the personal belongings without any battery inside. In addition, a lightweight three-pass authentication process helps to form a simple point-to-point short-range identification network which makes our monitoring system is superior to other monitoring systems using active communication technologies, such as Bluetooth, ZigBee, UWB, Wi-Fi, and so on. Six experimental scenarios have been developed to demonstrate the performance on item-level identification. By connecting +5.7/5.5dBi right-hand circularly polarized commercial antennas and +1.7dBi linear polarized antenna, under 1 watt power limitation, the proposed WPAMS has successfully identified all the items within 2-meter range. The current PCB size of interrogator is 2-inch×3.25-inch×0.25-inch and can be reduced in the near future.

The Performance Comparison of Sub-1GHz Wireless Personal Area Monitoring Systems

This paper presents a brand new hardware framework of wireless personal area monitoring system (WPAMS) in order to form a point-to-point simply connected personal area identification network with the applications of ubiquitous monitoring personal valuable belongings. The WPAMS consists of sub-1GHz radio frequency identification (RFID) interrogator subsystem, antenna subsystem and passive RFID transponder subsystem with salient features of low-cost, tiny and power-efficient. The hardware frameworks of two commercial interrogator prototypes have been identified and simulated. With the connection of 5.7dBi right-hand circularly polarized antenna and in the adherence of local power regulation (within 1watt), the identified range of all types of commercial transponders from sideward and upward directions can be reached to 2 meters. The current PCB size of interrogator is 88mm45mm and can be reduced in the near future.

DWDM 43 Gbit/s DPSK transmission over 1200 km with no inline dispersion compensation

Error-free dense wavelength division multiplexed (DWDM) transmission of 43 Gbit/s DPSK signals transmitted and detected by a commercial transponder is demonstrated over 1200 km of NZ-DSF with 50 GHz channel spacing and no inline dispersion compensation. Custom slope-matched dispersion compensation modules provide terminal-only compensation, facilitating a simple system configuration with performance >3 dB above the forward error correction threshold.