Rieko Sato

Optical packet synchronizer using wavelength and space switching

The authors develop and demonstrate an optical packet synchronizer. Synchronization with a time resolution of 16 ns is achieved by selecting one of 64 optical paths, each with a different length, using wavelength and space switching based on a tunable distributed Bragg reflector laser diode and eight semiconductor optical amplifier gates per channel. Asynchronous optical packet signals are successfully aligned in a series of common time slots.

40-gb/s burst-mode optical 2R regenerator

We have developed a 40-Gb/s burst-mode all-optical 2R regenerator using a limiting amplifier and a monolithic integrated wavelength converter. A limiting amplifier using a gain-saturated semiconductor optical amplifier with an inverted-mode signal can mitigate the pattern effect caused by the a burst-mode signal. By using this 2R regenerator, the 8-dB packet-to-packet power fluctuation of a return-to-zero (RZ) format signal was successfully equalized and the bit-error rate was greatly improved. In addition, we confirmed that a nonreturn-to-zero format signal was equalized by the limiting amplifier as well as the RZ format signals.

10-Gb/s low-input-power SOA-PLC hybrid integrated wavelength converter and its 8-slot unit

We achieved successful low-input-power (-10 dBm) wavelength conversion at 10 Gb/s by using a hybrid integrated cross-phase modulation wavelength converter (XPM-WC). The input CW power was also -10 dBm and the total current was only 215 mA, and no signal preamplifiers were used. From the relationship between the eye-opening ratio and the injection current to the SOA, we clarified the optimal current condition for low-input-power operation. The XPM-WC consists of a two-channel spot-size converter integrated semiconductor optical amplifier (SS-SOA), which is mounted on a planar lightwave circuit (PLC) platform. We also fabricated an 8-slot unit. XPM-WC modules are inserted in every slot and can operate independently. Stable and uniform low-input-power operation is confirmed in all slots.

Demonstration of an optical packet synchronizer for an optical packet switch

We have demonstrated a compact optical packet synchronizer. With a tunable DBR LD and SOA gates, the synchronization is successfully achieved with simple electric circuits by controlling the switching timing. Because OFCs are used, the OPSy is compact and the delay time can be controlled precisely. in this architecture, by increasing the number of wavelengths, finer resolution can be obtained without much increase in the losses and crosstalk.

Demonstration of packet-by-packet wavelength conversion from FP-LD light to ITU-T grid wavelengths

We demonstrated packet-by-packet wavelength conversion from Fabry-Perot laser diode (FP-LD) light to four ITU-T grid wavelengths. To achieve this we used a cross-phase modulation (XPM) wavelength converter and an arrayed-waveguide grating (AWG) router. Good feasibility was obtained at 2.5-Gb/s modulation. Selective wavelength conversion as described here is indispensable for the all-optical networks of future, in which optical signal sources without wavelength control will be used at user-end terminals.

Novel bit-rate-free and format-free PMD compensation with a differential group delay monitoring using a SOA/PLC hybrid integrated wavelength converter

A novel bit-rate-free and format-free differential group delay (DGD) monitoring technique using a hybrid wavelength converter (WC) as an exOR circuit was proposed. Using this method, the polarization mode dispersions (PMDs) of 40-Gb/s RZ format, 40-Gb/s NRZ format, and 20-Gb/s Manchester format were successfully equalized. The minimum received optical power at a BER of 10/sup -9/ was lower than -33 dBm, and the power penalty was less than 0.8 dB. This technique has a possibility to work even for input signal of more than a 100-Gb/s as well as for high-speed burst signal.

Full bit-rate conversion from 10-Gb/s random WDM channels to a 40-Gb/s channel using a Sagnac interferometer integrated with parallel amplifiers structure

Full bit-rate conversion from 10-Gb/s random WDM channels to a 40-Gb/s channel, including NRZ to RZ format conversion and reconversion, as well as phase adjusting procedure, is successfully demonstrated. Wavelength conversion in a monolithic Sagnac Interferometer integrated with Parallel Amplifiers Structure (SIPAS) is used.