Shogo Yamanaka

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

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.

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

We demonstrate 102.3 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 11.2-THz ultra-wideband low-noise amplification in the C- and extended L-bands.

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

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.

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

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.

A 20-Gs/s Track-and-Hold Amplifier in InP HBT Technology

This paper presents a 20-Gs/s track-and-hold amplifier (THA) fabricated InP HBT technology. This THA is capable of operating under relatively high input voltages. The THA uses a fully differential architecture with a switched emitter-follower. To mitigate the pedestal error due to the feedthrough attenuation network, we added degeneration resistors in the feedthrough attenuation block. Measured total harmonic distortion is below -40 dB at low input frequencies, and -18 dB at frequency of 9.9 GHz.

Ultrahigh-Speed Low-Power DACs Using InP HBTs for Beyond-100-Gb/s/ch Optical Transmission Systems

This paper presents the circuit designs and measured performance of two ultrahigh-speed low-power 6-b digital-to-analog converters (DACs) using InP-based heterojunction bipolar transistors (HBTs) for beyond-100-Gb/s/ch optical transmission systems. The first design is based on an R-2R ladder-based current-steering architecture with a novel double-sampling technique that relaxes the speed restraints for the DAC and helps achieve ultrahigh-speed operation. The DAC with the double-sampling technique achieves an excellent sampling speed of up to 32 GS/s with low power consumption of 1.4 W. The second design is based on a new timing alignment technique. The DAC with the timing alignment technique operates at a sampling rate of 28 GS/s with very low power consumption of 0.95 W and achieves an excellent figure of merit (0.53 pJ per conversion step). It provides a clear multilevel modulated signal for QAM transmission and can be applied to beyond-100-Gb/s/ch optical transmission systems.

Demonstration of translucent elastic optical network based on virtualized elastic regenerator

We propose a translucent elastic optical network based on a virtualized elastic regenerator. Using a real-time 128-Gb/s spectrum-selective subchannel regenerator, we verify the concept through mixed-rate superchannel regeneration and frequency-slot merger with spectrum conversion.

Ultra-compact coherent receiver with serial interface for pluggable transceiver

An ultra-compact integrated coherent receiver with a volume of 1.3 cc using a quad-channel transimpedance amplifier (TIA)-IC chip with a serial peripheral interface (SPI) is demonstrated for the first time. The TIA with the SPI and photodiode (PD) bias circuits, a miniature dual polarization optical hybrid, an octal-PD and small optical coupling system enabled the realization of the compact receiver. Measured transmission performance with 32 Gbaud dual-polarization quadrature phase shift keying signal is equivalent to that of the conventional multi-source agreement-based integrated coherent receiver with dual channel TIA-ICs. By comparing the bit-error rate (BER) performance with that under continuous SPI access, we also confirmed that there is no BER degradation caused by SPI interface access. Such an ultra-compact receiver is promising for realizing a new generation of pluggable transceivers.

Hybrid 40-Gb/s and 100-Gb/s PDM-QPSK DWDM transmission using real-time DSP in field testbed

We demonstrate hybrid 40-Gb/s and 100-Gb/s PDM-QPSK DWDM transmission using real-time DSP in 580-km DSF-installed field testbed. The nonlinear crosstalk penalty due to the hybrid transmission of less than 0.5 dB is confirmed.

An Ultrahigh-Speed Low-Power DAC Using InP HBTs for Multi-Level Optical Transmission Systems

This paper presents an ultrahigh-speed low-power digital-to-analog converter (DAC) for multi-level optical transmission systems. To achieve both high-speed and low-power operation, we used a simple R-2R ladder-based current-steering architecture and devised a timing alignment technique. The 6-bit DAC test chip was fabricated with our InP HBT technology, which yields a peak ft of 175 GHz and a peak fmax of 260 GHz. The measured differential and integral non-linearity (DNL and INL) are within +0.68/-0.16 LSB and +0.17/-0.68 LSB, respectively. The measured spurious-free dynamic range (SFDR) remains above 36 dB up to the Nyquist frequency at a sampling rate of 13.5 GS/s, which was the limit of our measurement setup. The expected linear ramp-wave outputs at a sampling rate of 27 GS/s are also obtained. The DAC chip was assembled into a metal package for use in an optical transmission experiment, where it provides a clear 4-level signal for 16-QAM optical transmission at a sampling rate of up to 28 GS/s. The DAC consumes only 0.95 W and has a better figure of merit (FOM) (0.53 pJ) than any other previously reported DAC with a sampling rate above 20 GS/s. Our DAC module can also be applied to beyond-100-Gb/s/ch multi-level optical transmission systems.