Toshimitsu Kaneko

Single-stripe tunable laser with Chirped Sampled Gratings fabricated by nanoimprint lithography

Fabrication of diffraction gratings of Chirped Sampled Grating Distributed Reflector (CSG-DR) laser by nanoimprint lithography (NIL) has been demonstrated. The diffraction gratings with highly uniform linewidth and period have been successfully fabricated by the combination of the reverse-tone NIL and precise etching techniques. The fabricated CSG-DR laser using NIL shows sufficiently wide tuning range of 40 nm as we designed.

High-power and low phase noise full-band tunable LD for coherent applications

High output power and low noise performances of CSG-DR-LD have been investigated. Kink-free fiber output power > 60 mW over C-band with high SMSR have been demonstrated. Measured phase noise is lower than 170 kHz, exhibiting excellent noise properties as a monolithic and single stripe tunable LD. These characteristics reveal that CSG-DR-LD is a promising light source for the future digital coherent applications.

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.

Optical-comb-line selection from a low-power/low-OSNR comb using a low-coherence semiconductor laser for flexible ultra-dense short range transceivers

6.25GHz-spaced optical-comb-line selection either by low-coherence injection-locked laser (LC-ILLD) or with a combination ultra-narrow-filter and low-noise-fiber-amplifier (UNF-FA) is assessed. In a 144Gbps DP-64QAM transmission the LC-ILLD outperforms the UNF-FA approach for comb-OSNR-levels below 30dB.

High-power and narrow-linewidth tunable distributed-reflector laser

Deployment of digital coherent transmission technologies to metro networks drives the use of higher-order modulation formats such as PDM-16QAM and downsizing of optical transceivers. A narrow-linewidth (<300 kHz) tunable laser with high output power (>+17 dBm) is very attractive for such purposes, not only because it can compensate for the modulation loss increase caused by a high-peak-to-average ratio of the electrical driving signal of higher-order modulation formats, but also because it can be shared between transmitter and receiver saving the foot-print and power dissipation. This paper reviews the Tunable Distributed Amplification — Chirped Sampled Grating — Distributed Reflector (TDA-CSG-DR) laser being developed for metro application.

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.

Autonomously controlled all-optical signal conditioning for dynamic optical path networks

We develop an autonomous parametric dispersion compensator with a fast tunable pump light source and a fast dispersion monitor. Fully automatic dispersion management is demonstrated in dynamic optical path testbed networks.

All-optical carrier recovery using a single injection locked semiconductor laser stabilized by an incoherent optical-feedback

Novel all-optical-hardware-efficient carrier recovery unit for carrier-suppressed BPSK signals is demonstrated. For the first time, carrier recovery with an optically stabilised injection-locked semiconductor laser enabled successful homodyne detection of 32-Gbit/s carrier-suppressed BPSK signals.

Hardware efficient QAM16 all-optical carrier recovery using a single optically-stabilized injection-locked semiconductor laser

A compact, low-complexity all-optical carrier-recovery-unit for carrier-unsuppressed QAM signals is demonstrated for the first time. The carrier regeneration by laser injection-locking and recovered-carrier stabilization by linewidth sharpening have enabled successful homodyne-detection of 12 GBd carrier-unsuppressed QAM4 and QAM16 signals.