Mitsunobu Gotoda

Tunable DFB Laser Array Integrated With Mach–Zehnder Modulators for 44.6 Gb/s DQPSK Transmitter

A tunable distributed feedback (DFB) laser array integrated with Mach-Zehnder modulators (TLA-MZMs) for a 44.6 Gb/s differential quadrature phase shift keying (DQPSK) transmitter has been developed. The TLA-MZMs covers 98 wavelength channels with the 50 GHz ITU-T grid in the L-band. The side-mode suppression ratio for all channels was over 47 dB. DC extinction ratios over 25 dB were achieved for the MZMs. Our design achieves both the low modulation voltage (2 Vπ) less than 3 Vpp and the low-excess loss less than 1 dB. 44.6 Gb/s DQPSK modulation with a low driving voltage of 3 V was successfully demonstrated.

Highly External Optical Feedback-Tolerant 1.49-

A 1490 nm InGaAsP single-mode laser diode, with high endurance against external optical feedback, was realized utilizing an optimized partially corrugated grating and a window-mirror-structure. The gratingpsilas length and the coupling coefficient were designed to enable moderate output power, low feedback sensitivity and a SMSR of 40 dB simultaneously. The relative intensity noise (RIN) was maintained less than -120 dB/Hz under strong external optical feedback as high as -10 dB.

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A 30 nm tunable laser diode utilizing front SG-DBR and rear SSG-DBR was demonstrated for the first time. High output power over 45 mW as well as good wavelength control was achieved with SMSR greater than 40 dB.

m Single-Mode Lasers With Partially Corrugated Gratings

An optical high-frequency pulse generation method with wavelength tunability is presented by taking advantage of vernier-type gratings in a distributed Bragg reflector laser diode. Experimental results showed that sinusoidal optical pulses, whose lasing wavelengths were tunable, were created with repetition frequencies around 30 GHz. The widths of the radio frequency spectra, furthermore, were drastically reduced by means of mode locking with externally injected optical pulses.

Widely tunable SOA-integrated DBR laser with combination of sampled-grating and superstructure grating

We report on the development of the first 30 nm tunable laser diode utilizing a front sampled grating-distributed Bragg reflector (SG-DBR) and a rear superstructure grating DBR (SSG-DBR). A high output power greater than 18 mW was achieved with superior longitudinal mode stability, as well as an overall power variation of less than 3 dB for the well-defined laser. Furthermore, lasers integrated with a semiconductor optical amplifier (SOA) enabled the output power to be controlled independently both by the active current and the SOA current, as well as achieving a maximum output power of 45 mW. The side-mode suppression ratio was in excess of 40 dB for all the 50 GHz spaced wavelength channels.

Optical high-frequency pulse generation with wavelength tunability by using a DBR laser with vernier-type gratings

A low power consumption tunable DFB laser diode array, integrated with backside waveguides, is experimentally demonstrated. Fiber output power of 14 dBm was obtained in full L-band with module power consumption less than 3 W.

A widely tunable SOA-integrated DBR laser by combination of sampled and superstructure gratings

Three-electrode-type self-pulsating (SP) distributed feedback (DFB) laser diodes (LDs) were fabricated. Lasing mode selectivity and pulsating frequency of SP-DFB LDs were investigated experimentally and device parameter dependences were well explained by numerical simulations.

Low Power Consumption L-Band Tunable Laser Diode with Backside Waveguides

We propose a versatile optical clock generation method with 10 nm wavelength tunability using widely tunable DBR lasers. Injection locking was experimentally demonstrated for 30 GHz sinusoidal pulses at 1545 and 1560 nm as well.