Shogo Yamanaka

Bio: Shogo Yamanaka is an academic researcher from Nippon Telegraph and Telephone. The author has contributed to research in topics: Signal & Analog signal. The author has an hindex of 13, co-authored 53 publications receiving 789 citations. Previous affiliations of Shogo Yamanaka include Harvard University.

102.3-Tb/s (224 × 548-Gb/s) C- and extended L-band all-Raman transmission over 240 km using PDM-64QAM single carrier FDM with digital pilot tone

Abstract: We demonstrate 1023 Tb/s transmission over 3×80 km of PSCF by employing 548-Gb/s PDM-64QAM single-carrier frequency-division-multiplexing (SC-FDM) signals with pilot tone and 112-THz ultra-wideband low-noise amplification in the C- and extended L-bands

Fast optical channel recovery in field demonstration of 100-Gbit/s Ethernet over OTN using real-time DSP.

Abstract: A field trial of 100-Gbit/s Ethernet over an optical transport network (OTN) is conducted using a real-time digital coherent signal processor. Error free operation with the Q-margin of 3.2 dB is confirmed at a 100 Gbit/s Ethernet analyzer by concatenating a low-density parity-check code with a OTN framer forward error correction, after 80-ch WDM transmission through 6 spans x 70 km of dispersion shifted fiber without inline-dispersion compensation. Also, the recovery time of 12 msec is observed in an optical route switching experiment, which is achieved through fast chromatic dispersion estimation functionality.

100 × 120-Gb/s PDM 64-QAM transmission over 160 km using linewidth-tolerant pilotless digital coherent detection

Abstract: We demonstrate 11.2-Tb/s transmission of 12.5-GHz spaced 120-Gb/s PDM 64-QAM signals over 160 km by using a digital coherent receiver with pilotless demodulation algorithms. The spectral efficiency of 9.0 b/s/Hz is the highest reported for 100-Gb/s/ch-class transmission.

Vector sum phase shifter, optical transceiver, and control circuit

Abstract: A vector sum phase shifter includes a 90° phase shifter ( 1 ) which generates an in-phase signal (VINI) and a quadrature signal (VINQ) from an input signal (VIN), a four-quadrant multiplier ( 2 I) which changes the amplitude of the in-phase signal (VINI) based on a control signal (CI), a four-quadrant multiplier ( 2 Q) which changes the amplitude of the quadrature signal (VINQ) based on a control signal (CQ), a combiner ( 3 ) which combines the in-phase signal (VINI) and the quadrature signal (VINQ), and a control circuit ( 4 ). The control circuit ( 4 ) includes a voltage generator which generates a reference voltage, and a differential amplifier which outputs the difference signal between a control voltage (VC) and the reference voltage as the control signal (CI, CQ). The differential amplifier performs an analog operation of converting the control voltage (VC) into the control signal (CI, CQ) similar to a sine wave or a cosine wave.

11 × 171 Gb/s PDM 16-QAM transmission over 1440 km with a spectral efficiency of 6.4 b/s/Hz using high-speed DAC

Abstract: We demonstrate 25-GHz-spaced eleven-channel 171 Gb/s PDM 16-QAM transmission over 1440 km. 16-QAM signals were generated by high-speed digital-to-analog converters. We achieved a record spectral efficiency-distance product of 9216 b/s/Hz-km (6.4 b/s/Hz × 1440 km) in the 16-QAM format.

Microresonator-based solitons for massively parallel coherent optical communications

Abstract: Solitons are waveforms that preserve their shape while propagating, as a result of a balance of dispersion and nonlinearity. Soliton-based data transmission schemes were investigated in the 1980s and showed promise as a way of overcoming the limitations imposed by dispersion of optical fibres. However, these approaches were later abandoned in favour of wavelength-division multiplexing schemes, which are easier to implement and offer improved scalability to higher data rates. Here we show that solitons could make a comeback in optical communications, not as a competitor but as a key element of massively parallel wavelength-division multiplexing. Instead of encoding data on the soliton pulse train itself, we use continuous-wave tones of the associated frequency comb as carriers for communication. Dissipative Kerr solitons (DKSs) (solitons that rely on a double balance of parametric gain and cavity loss, as well as dispersion and nonlinearity) are generated as continuously circulating pulses in an integrated silicon nitride microresonator via four-photon interactions mediated by the Kerr nonlinearity, leading to low-noise, spectrally smooth, broadband optical frequency combs. We use two interleaved DKS frequency combs to transmit a data stream of more than 50 terabits per second on 179 individual optical carriers that span the entire telecommunication C and L bands (centred around infrared telecommunication wavelengths of 1.55 micrometres). We also demonstrate coherent detection of a wavelength-division multiplexing data stream by using a pair of DKS frequency combs-one as a multi-wavelength light source at the transmitter and the other as the corresponding local oscillator at the receiver. This approach exploits the scalability of microresonator-based DKS frequency comb sources for massively parallel optical communications at both the transmitter and the receiver. Our results demonstrate the potential of these sources to replace the arrays of continuous-wave lasers that are currently used in high-speed communications. In combination with advanced spatial multiplexing schemes and highly integrated silicon photonic circuits, DKS frequency combs could bring chip-scale petabit-per-second transceivers into reach.

Fundamentals of Coherent Optical Fiber Communications

Abstract: The recently developed digital coherent receiver enables us to employ a variety of spectrally efficient modulation formats such as $M$ -ary phase-shift keying and quadrature-amplitude modulation. Moreover, in the digital domain, we can equalize all linear transmission impairments such as group-velocity dispersion and polarization-mode dispersion of transmission fibers, because coherent detection preserves the phase information of the optical signal. This paper reviews the history of research and development related to coherent optical communications and describes the principle of coherent detection, including its quantum-noise characteristics. In addition, it discusses the role of digital signal processing in mitigating linear transmission impairments, estimating the carrier phase, and tracking the state of polarization of the signal in coherent receivers.

Capacity Trends and Limits of Optical Communication Networks Discussed in this paper are: optical communication network traffic evolution trends, required capacity and challenges to reaching it, and basic limits to capacity.

Abstract: Since the first deployments of fiber-optic com- munication systems three decades ago, the capacity carried by a single-mode optical fiber has increased by a staggering 10 000 times. Most of the growth occurred in the first two decades with growth slowing to ten times in the last decade. Over the same three decades, network traffic has increased by a much smaller factor of 100, but with most of the growth occurring in the last few years, when data started dominating network traffic. At the current growth rate, the next factor of 100 in network traffic growth will occur within a decade. The large difference in growth rates between the delivered fiber capacity and the traffic demand is expected to create a capacity shortage within a decade. The first part of the paper recounts the history of traffic and capacity growth and extrapolations for the future. The second part looks into the technological chal- lenges of growing the capacity of single-mode fibers by pre- senting a capacity limit estimate of standard and advanced single-mode optical fibers. The third part presents elementary capacity considerations for transmission over multiple trans- mission modes and how it compares to a single-mode trans- mission. Finally, the last part of the paper discusses fibers supporting multiple spatial modes, including multimode and multicore fibers, and the role of digital processing techniques. Spatial multiplexing in fibers is expected to enable system capacity growth to match traffic growth in the next decades.

Capacity Trends and Limits of Optical Communication Networks

Abstract: Since the first deployments of fiber-optic communication systems three decades ago, the capacity carried by a single-mode optical fiber has increased by a staggering 10 000 times. Most of the growth occurred in the first two decades with growth slowing to ten times in the last decade. Over the same three decades, network traffic has increased by a much smaller factor of 100, but with most of the growth occurring in the last few years, when data started dominating network traffic. At the current growth rate, the next factor of 100 in network traffic growth will occur within a decade. The large difference in growth rates between the delivered fiber capacity and the traffic demand is expected to create a capacity shortage within a decade. The first part of the paper recounts the history of traffic and capacity growth and extrapolations for the future. The second part looks into the technological challenges of growing the capacity of single-mode fibers by presenting a capacity limit estimate of standard and advanced single-mode optical fibers. The third part presents elementary capacity considerations for transmission over multiple transmission modes and how it compares to a single-mode transmission. Finally, the last part of the paper discusses fibers supporting multiple spatial modes, including multimode and multicore fibers, and the role of digital processing techniques. Spatial multiplexing in fibers is expected to enable system capacity growth to match traffic growth in the next decades.

Modeling of the Impact of Nonlinear Propagation Effects in Uncompensated Optical Coherent Transmission Links

Abstract: We address perturbative models for the impact of nonlinear propagation in uncompensated links. We concentrate on a recently-proposed model which splits up the signal into spectral components and then resorts to a four-wave-mixing-like approach to assess the generation of nonlinear interference due to the beating of the signal spectral components. We put its founding assumptions on firmer ground and we provide a detailed derivation for its main analytical results. We then carry out an extensive simulative validation by addressing an ample and significant set of formats encompassing PM-BPSK, PM-QPSK, PM-8QAM, and PM-16QAM, all operating at 32 GBaud. We compare the model prediction of maximum system reach and optimum launch power versus simulation results, for all four formats, three different kinds of fibers (PSCF, SMF, and NZDSF) and for several values of WDM channel spacing, ranging from 50 GHz down to the symbol-rate. We found that, throughout all tests, the model delivers accurate predictions, potentially making it an effective general-purpose system design tool for coherent uncompensated transmission systems.