We propose an ultra-broadband full-mesh wavelength router supporting the T- and O-bands using 3 stages of cascaded arrayed waveguide gratings (AWGs). The router architecture is based on a combination of waveband and channel routing by coarse and fine AWGs, respectively. We fabricated several T-band-specific silica-based AWGs and quantum dot semiconductor optical ampliers as part of the router, and demonstrated 10 Gbps data transmission for several wavelengths throughout a range of 7.4 THz. The power penalties were below 1 dB. Wavelength routing was also demonstrated, where tuning time within a 9.4-nm-wide waveband was below 400 ms.

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We demonstrate a narrow-linewidth, low-intensity noise, widely wavelength-tunable LD for which we adopted a long external cavity configuration (ECLD) with a tunable optical filter. By employing a simultaneous tuning circuit between the optical filter and the Fabry-Perot mode caused by the external cavity, the oscillation wavelength was successfully tuned over the full C-band without mode hopping. The tunable optical filter bandwidth was 0.55 nm (1530~1570 nm). We achieved a linewidth of less than 8 kHz obtained with a delayed self-heterodyne method. On the other hand, the linewidth estimated from the white noise level of the optical frequency modulation noise power spectrum of the laser output was as narrow as 314 Hz. A relative intensity noise (RIN) below -130 dB/Hz was simultaneously achieved over the C-band range. With the same configuration except for an optical filter with a filter bandwidth of 0.6 nm for L-band operation (1570~1610 nm), we also realized a full L-band wavelength tunable ECLD with a linewidth of less than 7.7 kHz and a RIN of below -126 dB/Hz.

A two-wavelength emission laser (two-mode laser) has been fabricated using semiconductor quantum dots as the gain medium in the external cavity configuration. Two-mode laser emission with a separation of 98.8 GHz has been achieved by controlling the etalon and narrow-band filter setting. A 98.4 GHz beat signal was observed using the Michelson interferometer configuration, indicating that these emissions occurred simultaneously. #

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