Long-range acoustic communication is crucial to underwater applications such as collection of scientific data from benthic stations, ocean geology, and remote control of off-shore industrial activities. However, the transmission rate of acoustic communication is always limited by the narrow-frequency bandwidth of the acoustic waves because of the large attenuation for high-frequency sound in water. Here, we demonstrate a high-throughput communication approach using the orbital angular momentum (OAM) of acoustic vortex beams with one order enhancement of the data transmission rate at a single frequency. The topological charges of OAM provide intrinsically orthogonal channels, offering a unique ability to multiplex data transmission within a single acoustic beam generated by a transducer array, drastically increasing the information channels and capacity of acoustic communication. A high spectral efficiency of 8.0 ± 0.4 (bit/s)/Hz in acoustic communication has been achieved using topological charges between -4 and +4 without applying other communication modulation techniques. Such OAM is a completely independent degree of freedom which can be readily integrated with other state-of-the-art communication modulation techniques like quadrature amplitude modulation (QAM) and phase-shift keying (PSK). Information multiplexing through OAM opens a dimension for acoustic communication, providing a data transmission rate that is critical for underwater applications.

https://www.pnas.org/content/pnas/114/28/7250.full.pdf

High-speed acoustic communication by multiplexing orbital angular momentum.

Although vast amounts of information are conveyed by photons in optical fibers, the majority of data processing is performed electronically, creating the infamous ‘information bottleneck’ and consuming energy at an increasingly unsustainable rate. The potential for photonic devices to directly manipulate light remains unfulfilled due largely to a lack of materials with strong, fast optical nonlinearities. In this paper, we show that small-signal amplifier, summator and invertor functions for optical signals may be realized using a four-port device that exploits the coherent interaction of beams on a planar plasmonic metamaterial, assuming no intrinsic nonlinearity. The redistribution of energy among ports can provide nonlinear input-output signal dependencies and may be coherently controlled at very low intensity levels, with multi-THz bandwidth and without introducing signal distortion, thereby presenting powerful opportunities for novel optical data processing architectures, complexity oracles and the locally coherent networks that are becoming part of the mainstream telecommunications agenda. An all-optical device based on a planar plasmonic metamaterial is proposed that has summator, inverter and small-signal amplifier functions. Optical processing of optical data signals is strongly needed to overcome the ‘electronic bottleneck’ in current optical communication systems. Now, researchers at the University of Southampton in the UK and Nanyang Technological University in Singapore have theoretically demonstrated the feasibility of exploiting the coherent interaction of light beams in an ultrathin (substantially subwavelength) plasmonic metamaterial to achieve this. As the proposed device does not use nonlinear optical media, it should be possible to operate it at very low power levels. The energy redistribution between the four ports of the device can provide nonlinear input-output signal dependencies and may be controlled at very low intensity levels with multi-terahertz bandwidth and without distorting the signal.

/pdf/controlling-light-with-light-using-coherent-metadevices-all-4zzng6ld9x.pdf

Controlling light with light using coherent metadevices: all-optical transistor, summator and invertor

We measure the Brillouin gain spectra in two cores (the central core and one of the outer cores) of a ~3-m-long, silica-based, 7-core multi-core fiber (MCF) with incident light of 1.55 μm wavelength and investigate the Brillouin frequency shift (BFS) and its dependence on strain and temperature. The BFSs of both the cores are ~10.92 GHz and the strain- and temperature-dependence coefficients of the BFS in the central core are 484.8 MHz/% and 1.08 MHz/°C, respectively, whereas those in the outer core are 516.9 MHz/% and 1.03 MHz/°C. All of these values are not largely different from those in a silica single-mode fiber, which is expected because the cores are basically composed of the same material (silica). We then analyze the difference in structural deformation between the two cores when strain is applied to the fiber and show that it does not explain the difference in the BFS dependence of strain in this case. The future prospect on distributed strain and temperature sensing based on Brillouin scattering in MCFs is finally presented.

/pdf/brillouin-scattering-in-multi-core-optical-fibers-for-2l6hzdbw3h.pdf

Brillouin scattering in multi-core optical fibers for sensing applications

In this paper, we examine how energy constraints might shape future optical communication networks and the impact that current technology trends may have on future energy use. Historical factors and prevailing complications associated with fiber capacity point to an increased focus on energy to enable tighter photonic and electronic component integration and larger networks. Energy requirements and associated challenges are described at the component, system, and network level.

Energy Challenges in Current and Future Optical Transmission Networks

We demonstrate photonic circuits monolithically integrated on an InP-based platform for use in coherent communication links. We describe a technology platform that allows for the integration of numerous circuit elements. We show examples of an integrated transmitter which offers an on-chip wavelength-division-multiplexing source with a flat gain profile across a 2 THz band and a new device design to provide a flatted gain over a 5 THz band. We show coherent receivers incorporating an integrated widely tunable local oscillator as well as an optical PLL. Finally, we demonstrate a tunable optical bandpass filter for use in analog coherent radio frequency links with a measured spurious-free dynamic range of 86.3 dB-Hz2/3 as well as an improved design to exceed 117 dB-Hz2/3.

Indium Phosphide Photonic Integrated Circuits for Coherent Optical Links

Overview and System Technologies- Social Demand of New Generation Information Network: Introduction to High Spectral Density Optical Communication Technology- Coherent Optical Communications: Historical Perspectives and Future Directions- Ultrahigh Spectral Density Coherent Optical Transmission Technologies- "Quasi Ultimate" Technique- High-Speed and High-Capacity Optical Transmission Systems- Advanced Modulation Formats- Multilevel Signaling with Direct Detection- High Spectral Efficiency Coherent Optical OFDM- Polarization-Division-Multiplexed Coherent Optical OFDM Transmission Enabled by MIMO Processing- No-Guard-Interval Coherent Optical OFDM with Frequency Domain Equalization- QPSK-Based Transmission System: Trade-Offs Between Linear and Nonlinear Impairments- Real-Time Digital Coherent QPSK Transmission Technologies- Challenge for Full Control of Polarization in Optical Communication Systems- Opto-Electronics Devices- Semiconductor Lasers for High-Density Optical Communication Systems- Monolithic InP Photonic Integrated Circuits for Transmitting or Receiving Information with Augmented Fidelity or Spectral Efficiency- Integrated Mach-Zehnder Interferometer-Based Modulators for Advanced Modulation Formats- Key Devices for High-Speed Optical Communication and Their Application to Transceiver Module- Forward Error Correction

High spectral density optical communication technologies

PROBLEM TO BE SOLVED: To stabilize absolute frequencies of all longitudinal modes. SOLUTION: The frequency interval of a longitudinal mode spectrum of laser oscillation by a laser light source 1, and one longitudinal mode oscillation frequency of the longitudinal mode spectrum are independently fed back to the laser light source 1. A signal for adjusting repetition frequencies from a clock extraction circuit 5 and a PLL circuit 6, and a signal for adjusting absolute frequencies from a light filter 2, a frequency reference cell 3, and a phase sensitive detector circuit (optical phase modulator 41, oscillator 42, photodetector 43, lock-in amplifier 44) are independently fed back to the laser light source 1. Thus, stabilization is achieved, and the absolute frequencies of all longitudinal modes are simultaneously stabilized. COPYRIGHT: (C)2006,JPO&NCIPI

Double frequency stabilization mode synchronization laser light source

PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical fiber with vacancy which has vacancy having a desired diameter by measuring the diameter of the vacancy on real time during the drawing of a preform. SOLUTION: The method of manufacturing the optical fiber 1 with vacancy which has the vacancy 4 extended to the longitudinal direction of the optical fiber includes a process of imparting a prescribed physical change to the optical fiber 1 during a drawing process of the preform 14, measuring the amount of the physical change and measuring the diameter of the pores in the optical fiber 1 based on the resultant amount of the physical change. COPYRIGHT: (C)2005,JPO&NCIPI

Method of manufacturing optical fiber with vacancy

PROBLEM TO BE SOLVED: To realize an optical saturable absorber excellent in low loss and optical damage resistance or the non-linear optical waveguide structure of the absorber and to realize a super-short optical pulse laser and a small-sized optical switch capable of performing stable pulse oscillation and low-cost optical communication. SOLUTION: In the method for manufacturing an SWNT (Single Walled Carbon Nanotube) saturable absorption optical material, a chlorobenzene or tetrahydrofuran (THF) is used as a dispersion solvent. At first, ultrasonic processing is applied to an SWNT solution completely dissolved in the solvent or an SWNT solution to which surface processing is applied by radical addition. Then one of transparent polymers is added to the dispersion solvent and the dispersion solvent is surely agitated while applying ultrasonic waves so that the SWNT is uniformly dispersed into plastic. Finally, the dispersion solution is slowly and sufficiently dried in atmosphere heated to several tens °C. COPYRIGHT: (C)2007,JPO&INPIT

Method for manufacturing swnt saturable absorption optical material, pulse laser apparatus and all-optical type optical switch device

PROBLEM TO BE SOLVED: To provide an OTDM transmission method/device for realizing OTDM non-distortion transmission which substantially does not depend on spreading. SOLUTION: An OTDM signal which is time-divisionally multiplexed from an OTDM signal transmitter 1 is made incident on an optical Fourier transformer 2. When an optical pulse is a Fourier transformation limit pulse without chirp, optical Fourier transformation can be performed most correctly. The optical Fourier transformer 2 transforms the time waveform of the pulse into a signal on a frequency axis. An optical inverse Fourier transformer 2' transforms a spectral shape on the frequency axis into the time waveform (pulse). An optical fiber transmission path 3 has arbitrary dispersion and polarization mode dispersion. The spread amounts can be accompanied by timewise fluctuation. An OTDM signal receiver 4 multiplexes/separates a transmission signal to low speed optical signals in an optical region, receives the optical pulse at every channel and transforms it into an electric signal. COPYRIGHT: (C)2005,JPO&NCIPI

正隆中沢

Papers

High spectral density optical communication technologies

Double frequency stabilization mode synchronization laser light source

Method of manufacturing optical fiber with vacancy

Method for manufacturing swnt saturable absorption optical material, pulse laser apparatus and all-optical type optical switch device

Otdm transmission method and device

正隆 中沢

Papers

High spectral density optical communication technologies

Double frequency stabilization mode synchronization laser light source

Method of manufacturing optical fiber with vacancy

Method for manufacturing swnt saturable absorption optical material, pulse laser apparatus and all-optical type optical switch device

Otdm transmission method and device

正隆中沢