Hiroto Kawakami

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.

409-Tb/s + 409-Tb/s crosstalk suppressed bidirectional MCF transmission over 450 km using propagation-direction interleaving

We demonstrate bidirectional transmission over 450 km of newly-developed dual-ring structured 12-core fiber with large effective area and low crosstalk. Inter-core crosstalk is suppressed by employing propagation-direction interleaving, and 409-Tb/s capacities are achieved for both directions.

Dense SDM (12-Core

We propose long-haul space-division-multiplexing (SDM) transmission systems employing parallel multiple-input multiple-output (MIMO) frequency-domain equalization (FDE) and transmission fiber with low differential mode delay (DMD). We first discuss the advantages of parallel MIMO FDE technique in long-haul SDM transmission systems in terms of the computational complexity, and then, compare the complexity required for parallel MIMO FDE as well as the conventional time-domain equalization techniques. Proposed parallel MIMO FDE that employs low baud rate multicarrier signal transmission with a receiver-side FDE enables us to compensate for 33.2-ns DMD with considerably low-computational complexity. Next, we describe in detail the newly developed fiber and devices we used in the conducted experiments. A graded-index (GI) multicore few-mode fiber (MC-FMF) suppressed the accumulation of DMD as well as intercore crosstalk. Mode dependent loss/gain effect was also mitigated by employing both a ring-core FM erbium-doped fiber amplifier and a free-space optics type gain equalizer. By combining these advanced techniques together, we finally demonstrate 12-core × 3-mode dense SDM transmission over 527-km GI MC-FMF without optical DMD management.

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ABC (Auto Bias Control) technique for QAM (Quadrature Amplitude Modulation) transmitter is demonstrated. 16-QAM (10G baud) is generated and controlled using a single IQ modulator and asymmetric bias dithering technique. Measured penalty is 0.3dB.

3-Mode) Transmission Over 527 km With 33.2-ns Mode-Dispersion Employing Low-Complexity Parallel MIMO Frequency-Domain Equalization

This paper describes a simple and highly sensitive auto bias control (ABC) technique based on asymmetric bias dithering for optical quadrature phase shift keying (QPSK) modulation and QPSK variants. Using our asymmetric bias dithering proposal, the required bandwidth of the ABC circuit is only dc ~ 2fd, where fd is the frequency of dithering, fd <; 1 kHz. Thus, the circuit can be constructed without using high-speed components, and bias control performance is not limited by the signal bit rate. In this paper, we detail the concept of asymmetric bias dithering. We describe experiments that confirm bias monitoring and ABC operation, using a 20-64 Gbit/s optical QPSK signal. Its typical penalty is 0.1 dB, and Q factor fluctuation is negligible over 6 h of operation.

Auto bias control technique for optical 16-QAM transmitter with asymmetric bias dithering

We propose a novel polarization dependent frequency shift (PDf) reduction method for fabricating a silica-based PLC DQPSK demodulator incorporating an asymmetrically positioned half-wave plate, and demonstrate error-free 43-Gbit/s demodulation for any incident SOP. The PDf has a detrimental effect on the demodulation performance of a DQPSK signal, and it is degraded by various kinds of PLC fabrication errors. In this paper, we focus on the polarization crosstalk in the coupler, which is one of the main causes of PDf. To eliminate such PDf, we controlled both the position of the half-wave plate in the MZI and the polarization of the propagated light. We describe the principle of this PDf reduction method in detail and provide a theoretical and experimental discussion. In addition, we describe a compact DQPSK demodulator composed of a single MZI based DQPSK demodulator with a 90-degree optical hybrid. This demodulator configuration can reduce the receivers footprint. Finally we achieved a compact DQPSK demodulator with a low PDf of less than 0.10 GHz in the L-band.

Auto Bias Control Technique Based on Asymmetric Bias Dithering for Optical QPSK Modulation

We propose a new hybrid integrated optical front-end module for a 100-Gb/s-class coherent receiver using silica-based planar lightwave circuit (PLC) technology. We have developed an integrated structure composed of multichannel microcollimator optics between PLC waveguides and photodiodes (PDs), and compact hermetically sealed optical-to-electrical converters with a PD array and a transimpedance amplifier array to maintain reliability. We used the technology to fabricate an all-in-one optical front-end module for a dual polarization quadrature phase-shift-keying (DP-QPSK) coherent receiver, and confirmed that the module operated successfully for 112-Gb/s DP-QPSK signal detection.

Asymmetric Half-Wave Plate Configuration of PLC Mach–Zehnder Interferometer for Polarization Insensitive DQPSK Demodulator

We propose a new PLC design for a 43 Gb/s DQPSK demodulator. The design reduces both the module size and the power consumption without degrading any of the module characteristics.

All-in-One 112-Gb/s DP-QPSK Optical Receiver Front-End Module Using Hybrid Integration of Silica-Based Planar Lightwave Circuit and Photodiode Arrays

We propose a novel monitoring technique targeting chromatic dispersion (CD) in a DQPSK system. A signed non-intrusive monitor can be realized by using asymmetric waverform distortion in a 43 Gbit/s DQPSK system without pilot tone.

Compact DQPSK demodulator with interwoven double Mach-Zehnder interferometer using planar lightwave circuit

We demonstrate 120.7-Tb/s SDM/WDM unrepeatered transmission over a 204-km 7-core fiber with aggregate spectral efficiency of 53.6 b/s/Hz using a remotely pumped 7-core EDFA and Raman amplification. 17.2-Tb/s (180 × 95.8 Gb/s) PDM-32QAM signals have been transmitted at each core.