Yoichi Oikawa

Microsecond switching of parametric tunable dispersion compensator

A record-fast, 2 μs switching operation of an optical tunable dispersion compensator is demonstrated with a parametric tunable dispersion compensation scheme. We alternately switch two optical paths having different net dispersions with a microsecond guard interval of the compensator response and achieve successful transmissions of 43 Gbit/s non-return-to-zero on-off-keying optical signals. The error-free guard time for the switching of the two optical paths is 125 μs, limited mostly by the clock synchronization of the bit-error detector. The power penalty due to the switching of the compensator is less than 0.5 dB.

Counter-Dithering Pump Scheme for Cascaded Degenerate FWM Based Wavelength Converter

We demonstrate counter-dithering of pumps between two cascaded FWM processes for highly-efficient format-independent wavelength conversion. Up-to -1.2dB FWM conversion efficiency is obtained over 32-nm. 86-Gbps DP-QPSK are converted with OSNR penalty below 0.3dB at 10-3 BER.

Less than 0.19-dB transient gain excursion AGC-EDFA with digital control for 20-channel add/drop equivalent operation

We have developed a digitally controlled AGC-EDFA by combining an FF-controlled pump-LD and an FB-controlled VOA. An FPGA is used to finely tune the gain setting of the pump current with a wide dynamic range for input burst signals and to precisely configure the gain and cutoff bandwidth for the loop control of the VOA. We realized a gain excursion of less than 0.19 dB at the AGC-EDFA with the VOA for a 20-channel add/drop equivalent operation. We believe 0.19 dB to be the smallest value yet reported.

On the Cascadability of All-Optical Wavelength Converter for High-Order QAM Formats

With the evolution to ever more complex modulation formats for optical signals, all-optical wavelength converters offer great benefits to optical networks, thanks to the possibility of translating the wavelength of an optical signal regardless of its data rate or modulation format. To deliver its full advantages over conventional optical-electrical-optical conversion, an all-optical wavelength converter has to possess important features in terms of transparency, bandwidth, and cascadability for practical applications in real systems. In this paper, we review a recent development of an all-optical wavelength converter, which exhibits seamless conversion in the C-band with a low noise figure of 6.2 dB for dual-polarization (DP) phase-modulated signals. We then carry out an investigation by both experiment and calculation of the cascaded operation of the developed wavelength converter for high-order quadrature amplitude modulation (QAM) formats. A cascadability comparable to an erbium-doped fiber amplifier is achieved for DP-QPSK, DP-16QAM, and DP-64QAM signals, thanks to the exemplary characteristics of the wavelength converter.

High-Speed Optical and Millimeter-Wave Wireless Link for Disaster Recovery

A government-funded R and D program aiming at a resilient optical and millimeter-wave wireless link for a novel span protection scheme in a disaster recovery is presented. We also describe the key enabling technologies of both optical and wireless sub- systems and devices, including MIMO radio-over- fiber system, optical two-tone generation, and the transceiver and power amplifier in W-band.

Sub-millisecond timing-jitter-free tuning of parametric dispersion compensator.

We demonstrate sub-millisecond tuning of a prototype parametric tunable dispersion compensator (P-TDC) based on cascaded polarization-diverse four-wave mixing (FWM) process with a fast tunable and highly wavelength-stable pump light source. The pump light source is developed using a tunable distributed amplification chirped sampled grating distributed reflector laser that is fully wavelength tunable by on-chip heaters with a 3-dB frequency response of 45 kHz, resulting in fast dispersion tuning of less than 50 μs without additional timing jitter. The P-TDC is developed as the first prototype to satisfy essential requirements for practical network uses: stable input-polarization diversity, input-wavelength preservation, and seamless dispersion tunability for entire C-band input wavelengths are simultaneously achieved.

Dynamic parametric dispersion compensation using FPGA pump controller and dispersion monitor

We demonstrate an autonomous fast parametric dispersion compensator with a fast TDA-CSG-DR laser and a dispersion monitor based on spectral shearing interferometer. A response time of less than 17 ms, potentially sub millisecond, is achieved.

0.2-dB gain excursion AGC-EDFA with a high speed VOA for 100-channel add/drop equivalent operation

We have developed a digitally controlled AGC-EDFA by combining an FF-controlled pump-LD and an FF-controlled VOA. We realized a gain excursion of less than 0.2 dB at a 100-channel add/drop equivalent operation.

Suppression of transients in an EDFA chain using feed-forward pump control and a high-speed VOA

We report on an error-free operation of the survivor channel during instantaneous load and unload of a 7-ms burst signal with 16-dB dynamic range, in cascaded six fast feed-forward AGC-EDFAs assisted by a fast VOA.

Autonomous Parametric Tunable Dispersion Compensation for Dynamic Optical Switching

We demonstrate dynamic parametric optical dispersion compensation in dynamic optical path networks (DOPNs). A fully automatic parametric tunable dispersion compensator (P-TDC) based on four-wave mixing process is developed with a fast tunable distributed amplification chirped sampled grating distributed reflector laser, a field-programmable gate array (FPGA) pump controller, and a fast dispersion monitor based on spectral shearing interferometer. The dispersion monitor detects a change in the dispersion of a path, and the monitoring signal is fed forward to the FPGA controller. The fast tunable laser sets its wavelength accordingly for the dispersion compensation through parametric process. A response time of <;17 ms is demonstrated in a testbed of DOPN. The autonomous P-TDC has a potential response of submillisecond.