Moriya Nakamura

Linewidth-tolerant 10-Gbit/s 16-QAM transmission using a pilot-carrier based phase-noise cancelling technique.

We experimentally demonstrated linewidth-tolerant 10-Gbit/s (2.5-Gsymbol/s) 16-quadrature amplitude modulation (QAM) by using a distributed-feedback laser diode (DFB-LD) with a linewidth of 30 MHz. Error-free operation, a bit-error rate (BER) of <10(-9) was achieved in transmission over 120 km of standard single mode fiber (SSMF) without any dispersion compensation. The phase-noise canceling capability provided by a pilot-carrier and standard electronic pre-equalization to suppress inter-symbol interference (ISI) gave clear 16-QAM constellations and floor-less BER characteristics. We evaluated the BER characteristics by real-time measurement of six (three different thresholds for each I- and Q-component) symbol error rates (SERs) with simultaneous constellation observation.

Ultra High Capacity Self-Homodyne PON With Simplified ONU and Burst-Mode Upstream

In this letter, we demonstrate a proof of concept fully loaded bidirectional ultrahigh capacity coherent passive optical network (2 × 1008 × 8.3 Gb/s). This was achieved using partial spectrum overlap, Nyquist shaping, digital frequency shifting, self-homodyne detection, and pilot tone remodulation. Upstream burst mode operation is also demonstrated.

30-Gbps (5-Gsymbol/s) 64-QAM self-homodyne transmission over 60-km SSMF using phase-noise cancelling technique and ISI-suppression based on electronic digital processing

Linewidth-tolerant 30-Gbit/s (5-Gsymbol/s) 64-QAM real-time transmission over 60-km SSMF without any dispersion compensation was experimentally demonstrated by ISI-suppression based on electronic digital processing and pilot-carrier aided optical phase-noise cancelling for the first time.

Ultimate Linewidth-Tolerant 20-Gbps QPSK-Homodyne Transmission using a Spectrum-Sliced ASE Light Source

We demonstrated ultimate linewidth-tolerant 20-Gbps QPSK-homodyne using a 3-nm spectrum-sliced ASE light source by an optical phase noise cancellation, attained BER less than 1 times 10-6 after 160-km transmission. We also characterized DGD and dispersion tolerances.

40-Gb/s QPSK and 20-Gb/s PSK with inserted pilot symbols using self-homodyne detection

We proposed and experimentally demonstrated 40-Gb/s quadrature phase-shifted keying (QPSK) and 20-Gb/s binary phase-shifted keying (PSK) transmission systems with inserted pilot symbols, using a return-to-zero radio frequency (RZ-RF) driving signal in the transmitter and self-homodyne direct detection in the receiver. Different from other existing homodyne or conventional differential PSK/QPSK systems, the proposed PSK and QPSK modulation formats do not need any complicated pre-coder, post-processor or local oscillator. In the proposed QPSK systems, simultaneous detection of in-phase and quadature components is successfully achieved by using one Mach-Zehnder delay interferometer and following balanced detector, which significantly reduces the system complexity and implementation cost.

16-QAM optical packet switching and real-time self-homodyne detection using polarization-multiplexed pilot-carrier.

We first demonstrated 20-Gbit/s 16-QAM optical packet switching and real-time detection. The modulated optical packets and pilot-carriers were simultaneously generated from a prototype pilot-carrier vector modulator and detected by simple self-homodyne receivers. Error-free operation was confirmed by a real-time error count using a packet BERT.

Self-Homodyne Detection-Based Fully Coherent Reflective PON Using RSOA and Simplified DSP

We investigate the power budget of a fully coherent reflective passive optical network, based on self-coherent upstream (US) and self-homodyne downstream (DS) detection schemes. We consider, for US, both binary phase-shift keyed (BPSK) and quadrature phase-shift keyed (QPSK) at 1 GBd generated by direct modulation of a low-cost reflective semiconductor optical amplifier having 1-GHz electrical bandwidth and using simplified digital signal processing (DSP). We find that the penalty of increasing the order of US modulation format from BPSK to QPSK for higher capacity can be reduced to 1 dB by means of DS digital spectral shifting and US static postequalization.

Linewidth-tolerant real-time 40-Gbit/s 16-QAM self-homodyne detection using a pilot carrier and ISI suppression based on electronic digital processing

We experimentally demonstrate linewidth-tolerant real-time 40-Gbit/s(10-Gsymbol/s) 16-quadrature amplitude modulation. We achieved bit-error rates of <10(-9) using an external-cavity laser diode with a linewidth of 200 kHz and <10(-7) using a distributed-feedback laser diode with a linewidth of 30 MHz, thanks to the phase-noise canceling capability provided by self-homodyne detection using a pilot carrier. Pre-equalization based on digital signal processing was employed to suppress intersymbol interference caused by the limited-frequency bandwidth of electrical components.

PMD- and Dispersion-Tolerance of QPSK Homodyne Detection using a Polarization-Multiplexed Pilot Carrier

PMD- and dispersion-tolerance of QPSK homodyne detection using a polarization-multiplexed pilot carrier was demonstrated for both NRZ and RZ formats. Receiver sensitivity penalty versus ratio of pilot carrier to total optical power was also investigated.

Digital Self-Homodyne Detection

This letter proposes and experimentally demonstrates a novel digital self-homodyne detection (DSHD) receiver for low-cost coherent detection of high-order modulation formats. The proposed approach is demonstrated for detection of 4-GBd quadrature phase shift keying, 16-quadrature amplitude modulation (QAM), 32-QAM, and 64-QAM signals with combined linewidths from 630 kHz up to 5.7 MHz without the need for optical filtering and polarization alignment. We describe the structure of the DSHD digital signal processing before evaluating the receiver performance in back-to-back, after single-span fiber transmission with both single-channel and multichannel transmitters, and after multispan transmission in a recirculating loop using a single channel. These results show that DSHD outperforms intradyne detection in the presence of fiber nonlinearity for QAM modulation formats of order 16 and higher.