Tatsuro Kurobe

Reduction of spectral-linewidth in high power SOA integrated wavelength selectable laser

The effect of optical feedback from various reflected points on the spectral-linewidth was analyzed for a wavelength selectable laser consisting of a 12 distributed feedback (DFB) laser array, multimode interference coupler, and semiconductor optical amplifiers (SOA). For all 12 DFB lasers, a narrow linewidth of less than 2 MHz was achieved with over 50 mW by reducing facet reflectivity.

Optical Burst Switching Router With 40-,10-Gb/s Bit-Rate Transparent Contention Resolution

We report a bit-rate transparent optical burst switching (OBS) router prototype using a fast 5 times 5 PLZT [(Pb,La)(Zr,Ti)O3 ] optical matrix switch. Dynamic switching in a two-wavelength, 2 times 2 OBS switch is demonstrated. Contention resolution using a tunable Mach-Zehnder interferometer wavelength converter for both 40- and 10-Gb/s bursts is demonstrated for the first time. Error-free operation was achieved for both bit rates under the same settings, as required in autonomous networks

Optical Burst Switching Node with Sub-millisecond Granularity Equipped with Agile Tunable Wavelength Converter and Waveguide Amplifier

An optical switching node with sub-millisecond granularity is demonstrated. The node is equipped with shared wavelength converter for contention resolution with microsecond tuning speed and compact gain block for loss compensation based on erbium-doped waveguide.

Tunable laser source for fast wavelength switching using a short-cavity DBR laser packaged with wavelength locker

Simple switching scheme of frequency with precise feedback control of robust wavelength locker has been presented for a short-cavity DBR laser array. Switching time was less than 13 musec within +/- 2.5GHz from ITU grid.

1550 nm AlGaInAs/InP widely tunable BH laser based on arrayed DFB

We have fabricated high performance 1550nm both solitary lasers and the 12-channel arrayed DFB/SOA integrated widely tunable lasers with buried-heterostructure configuration in the AlGaInAs/InP system. An output power of 100mW was obtained for tunable lasers at 20°C.

High output power widely tunable laser module

We have developed highly reliable widely tunable module, whose performances were comparable with fixed-wavelength DFB laser module. To realize wide tunability, 12 l/4-shifted DFB laser array, S-bend waveguides, MMI coupler and an SOA were integrated on a chip. We could achieve 37nm tunability by controlling each chip temperature in the range of 5 to 45°C. High output fiber coupled power of 30mW and very uniform L-I curves out of 12 DFB lasers were achieved even at 50°C. Good quality of lasing spectrum was obtained. Side mode suppression ratio (SMSR) > 45dB. The well-suppressed reflection at chip front facet contributed to the lower noise characteristics, such as RIN < -140dB/Hz and linewidth < 4MHz. The shift of locked frequency was less than 0.4GHz as the case temperature varied from -5 to 75°C. Very small frequency shift was realized by controlling the temperature of locker part, independently. By optimizing TEC design, we could achieve low TEC power consumption less than 4W under Tcase=75°C and the end of life condition of SOA current. The new function by incorporating SOA was VOA. By changing the operating SOA current, we could vary output power from 1mW to 20mW, maintaining SMSR > 40dB, RIN < -135dB/Hz, linewidth < 4MHz. We also performed optical blocking > 40dB, when SOA current was turned off. We examined modules reliability under high temperature storage of 85°C. The change of output power was < ± 10%, and the shift of locked frequency was < ± 5pm after 2000 hours.

Widely tunable lasers based on mode-hop-free semiconductor laser array

Integration of mode-hop-free tunable laser array and a semiconductor optical amplifier is most reliable approach to realize widely tunable lasers. We have developed two types of tunable lasers, one is a thermally tunable DFB laser array for DWDM tunable transponders, which has shown high power and wide tunability covering Cband or L-band, housing in compact butterfly packages with robust wavelength locker. Another is a short-cavity DBR laser array for optical burst switching, whose lasing frequency can be monotonously tuned and locked on the ITU grid within 5 microseconds. Both lasers have demonstrated superior performances in system experiments.