Hiromi Tsuji

EA-Modulator-Based Optical Time Division Multiplexing/Demultiplexing Techniques for 160-Gb/s Optical Signal Transmission

In this paper, 160-Gb/s optical-time-division-multiplexing (OTDM) techniques employing electroabsorption (EA)-modulator-based optical multiplexer are described. The optical multiplexer integrates four EA modulators with free-space optics and enables, stably, to generate an authentic 160-Gb/s OTDM signal. The optical multiplexer possesses a switching capability of modulation format, which originates in the thermo-optic effect in EA waveguide, so that it is possible to generate various phase-coded OTDM signals such as carrier-suppressed return-to-zero (CS-RZ) signal by tuning operation temperatures of the EA modulators. By employing the novel 160-Gb/s optical multiplexer, prototypes of 160-Gb/s OTDM transmitter and receiver were developed. EA modulators are also adopted to optical short pulse source at transmitter side, optical time division demultiplexer, and phase-locked loop (PLL) circuit for clock recovery at the receiver side. The 160-Gb/s system prototype exhibited a superior performance maintaining high stability, and its applicability to practical use is discussed, showing experimental results of 160-Gb/s 635 km field trial on Japan Gigabit Network II (JGN II) optical testbed

EA Modulator-Based Optical Multiplexing/Demultiplexing Techniques for 160 Gbit/s OTDM Signal Transmission

160 Gbit/s optical-time-division-multiplexing (OTDM) transmitter/receiver employing electroabsorption (EA) modulators are described. In the 160 Gbit/s OTDM transmitter, the optical multiplexer, which implemented four EA modulators, is used and the generation of authentic 160 Gbit/s OTDM signal is realized. The optical multiplexer also enables to generate the phase-coded OTDM signal such as carrier-suppressed return-to-zero (CS-RZ) signal at 160 Gbit/s by changing driving temperatures of the EA modulators. In the 160 Gbit/s receiver, the EA modulator is also used in an optical demultiplexer and a phase-locked-loop (PLL) for clock extraction. As both optical demultiplexer and PLL are insensitive to polarization state of incoming signal, highly stable operation is achieved. We also show some results of transmission experiment using the developed OTDM transmitter/receiver and discuss the advantage of a switching capability of modulation format in the 160 Gbit/s signal transmission.

80-Gb/s error-free transmission over 5600 km using a cross absorption Modulation based optical 3R regenerator

Transoceanic transmission at 80 Gb/s was successfully demonstrated by introducing an optical retiming, reshaping, reamplifier (3R)-signal regenerator using cross-absorption-modulation gate and self-phase-modulation-based wavelength converter. At the 3R repeater spacing of 160 km, 80-Gb/s error-free transmission over 5600 km was achieved. The power penalty at 5600 km was 2 dB, and very clear eye-opening was observed even after 11 200-km transmission.

Control and Stabilization of bit-wise phase correlation in 160 (4 x 40) Gbit/s OTDM signal and its impact on transmission.

Detail of control technique of bit-wise phase correlation in 160 (4 x 40) Gbit/s optical time division multiplexing (OTDM) signal using a phase-correlation monitor based on 1-bit delay asymmetric interferometers (AIFs) is described. The 1-bit delay AIF transforms a bit-by-bit optical phase discontinuity to an optical power variation, so that it enables to quantify the phase-jump between adjacent bits. By use of this unique technique, we experimentally demonstrated stable generation of bitwisely phase-controlled 160 Gbit/s periodical alternate-phase return-to-Zero (APRZ) signal in addition to other different modulation formats such as conventional RZ, carrier suppressed RZ (CS-RZ), pair-wise alternate-phase CSRZ (PAP-CSRZ) and pi/2-APRZ. And long term stability was observed with CS-RZ signal. Also, we show some experimental results of 120 km un-repeatered transmission using standard single mode fiber (SSMF) and then discuss the impact of bit-wise phase change on 160 Gbit/s OTDM transmission performance.

All-optical 3R-signal regeneration at 80 Gbit/s using high-speed electro-absorpsion modulator

An all-optical 3R-signal regeneration using cross-absorption modulation in EAM was investigated and the error free signal regeneration at the bit rate of 80 Gbit/s was achieved with a proper operating condition.

A Study of 160Gbps PON System Using OTDM and OCDM Technologies

First demonstration of asymmetric PON system (10 Gbps × 16 ch downstream) using OTDM and OCDM technologies is presented. We accomplished a transmission over 20 km SMF with optimized dispersion tolerance.

Monitoring technique for waveform distortion of 160 Gb/s signal by prescaled-clock tone detection using EA modulator.

In order to monitor quality of ultra high bit-rate optical signals in a future optical network, such as 160 Gb/s, a simple monitoring technique is required. Therefore, a novel waveform monitoring technique by prescaled-clock tone detection was proposed in a previous report. In this paper, detailed principle of the proposed technique was explained. The monitoring technique is based on an asynchronous beat signal generation using an elecro-absorption modulator (EAM) and is able to separately observe waveform distortion caused by accumulated chromatic dispersion (CD), polarization mode dispersion (PMD) and optical signal-to-noise ratio (OSNR) degradation. The verification of concepts was performed by experiments, in which 1 GHz pre-scaled signals were employed to monitor distortion of OTDM 160 Gb/s carrier suppressed return-to-zero (CS-RZ) signals. Furthermore, applicability to Q factor estimation was verified by an experiment. In addition, an observation of 160 Gb/s signal by the proposed monitor was demonstrated over 120 minutes using an installed fiber in JGNII testbed.

Waveform Distortion Monitor for 160 Gbit/s Signal by Prescaled-clock Measurement using EA Modulator

Novel waveform monitoring technique for 160 Gbit/s OTDM signal using an asynchronous EAM prescaler is proposed. This waveform monitor can detect waveform distortion caused by residual dispersion, PMD and OSNR degradation separately. And the feasibility of the monitor was examined by experiments and numerical estimations.