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.

We proposed and demonstrated a novel wavelength stabilization technique for dense wavelength division multiplexing (DWDM) systems using dithering-induced AM cancellation which improves both wavelength stability and data transmission performance. Our wavelength stabilization technique consists of an optical frequency discriminating function and a function for canceling AM components induced by frequency dithering of the light source. The frequency discrimination in this technique is based on an FM-AM conversion effect, obtained by interaction from frequency dithering of the light with the bandpass characteristic of an arrayed-waveguide grating (AWG) multiplexer. The AM cancellation function was added to suppress optical frequency discriminating errors occurring due to AM components induced by frequency dithering in this wavelength stabilization architecture. In this scheme, an electro-absorption (EA) modulator is employed not only for modulating high-speed data traffic but also for suppressing AM components induced by frequency dithering on the light signal. Since the EA modulator is usually used for modulating high-speed data traffic, dedicated optical devices are not required for suppressing the AM components. The wavelength stability of a light source can therefore be enhanced with simple architecture. In the demonstration, a reduction of fluctuations within 50 MHz versus changes in the modulation index, and long-term stability within 320 MHz after more than 60 hours was achieved in 10 Gbit/s NRZ transmission. We also confirmed that the proposed AM cancellation technique effectively reduces the transmission penalties due to frequency dithering in 10 Gbit/s NRZ data transmission performance.

We proposed and demonstrated a novel wavelength stabilization technique for dense wavelength division multiplexing (DWDM) systems using dithering-induced AM cancellation which improves both wavelength stability and data transmission performance. Our wavelength stabilization technique consists of an optical frequency discriminating function and a function for canceling AM components induced by frequency dithering of the light source. The frequency discrimination in this technique is based on an FM-AM conversion effect, obtained by interaction from frequency dithering of the light with the bandpass characteristic of an arrayed-waveguide grating (AWG) multiplexer. The AM cancellation function was added to suppress optical frequency discriminating errors occurring due to AM components induced by frequency dithering in this wavelength stabilization architecture. In this scheme, an electro-absorption (EA) modulator is employed not only for modulating high-speed data traffic but also for suppressing AM components induced by frequency dithering on the light signal. Since the EA modulator is usually used for modulating high-speed data traffic, dedicated optical devices are not required for suppressing the AM components. The wavelength stability of a light source can therefore be enhanced with simple architecture. In the demonstration, a reduction of fluctuations within 50 MHz versus changes in the modulation index, and long-term stability within 320 MHz after more than 60 hours was achieved in 10 Gbit/s NRZ transmission. We also confirmed that the proposed AM cancellation technique effectively reduces the transmission penalties due to frequency dithering in 10 Gbit/s NRZ data transmission performance.

This paper describes short pulse generation at over 40 GHz using monolithic mode-locked lasers integrated with electroabsorption modulators. The electroabsorption modulator using strained-InGaAsP multiquantum wells provides a pulse shortening gate at a high-repetition frequency. Pulse generation around 4 ps has been realized at a repetition frequency of 43. 5 GHz. Pulse compression using a 1. 3 µm single mode fiber is performed and a 0. 87 ps pulse is obtained.