As a promising platform technology for optical switches, silicon photonics is recently attracting much attention. In this paper, we demonstrate compact 8 × 8 silicon photonic switch modules with low loss, low polarization sensitivity, and low cross-talk properties. An optical circuit including 152 thermo-optical switch elements and spot size converters were formed within a silicon chip size of 12 mm × 14 mm. The developed module where a silicon photonic chip was assembled with a fiber array showed about 6-dB average excess optical loss, including optical coupling loss, on all 64 paths of the 8 × 8 optical switch. Measured polarization dependent loss was about 0.6 dB on average over 64 paths and cross-talk was less than -35 dB. These optical switch modules are intended for applying to ROADMs in telecom optical networks, but, the port count extensibility using multiple compact modules and the faster switching capability of the optical switch are also useful for datacenter applications where hybrid network scheme with electronic packet switches and optical circuit switches is intensively investigated.
Silicon photonic-wire waveguide is one of the most promising platforms in constructing compact optical devices, since
the waveguide can be bent with a radius of less then several microns. Recently, we have demonstrated various optical
devices based on silicon photonic-wire waveguides, which include a directional coupler, a tunable optical add-drop
multiplexer, and some ultra-compact 1 x <i>N</i> optical switches. The optical coupling length of the directional coupler was
just around 10 microns, due to its high coupling efficiency. The tunable optical add-drop multiplexer was constructed
with Bragg grating waveguides. It was about 700-μm-long, and was controlled through thermo-optic effect. The
maximum center-wavelength shift of the tunable optical add-drop multiplexer was 6.6 nm, which was obtained at a
tuning power of 0.82 W. The 1 x <i>N</i> optical switches were Mach-Zehnder interferometer types and were also thermally
controlled. The 1 x 2 switch was compact with a footprint of 85 x 30 µm2. Its maximum extinction ratio exceeded 30 dB.
The switching power and switching time was about 90 mW and 100 μsec, respectively. The 1 x 4 optical switch was
constructed based on the 1 x 2 switch. Its operation was successfully demonstrated. The 1 x 4 optical switch was
believed to be the smallest switch in the world. A 1 x 8 optical switch was also demonstrated with its switching
operations. Further, we are fabricating a compact packaged switch module with a size of 15 x 8 x 5 (height) mm<sup>3</sup>, which
includes a 1 x 4 optical switch and the input and output fiber couplers assembly.
We investigated ultrafast optical signal processing schemes utilizing mode-locked semiconductor laser diodes (MLLDs) for optical time-division multiplexing (OTDM) transmission at over 100 Gbit/s and developed a polarization-insensitive all-optical clock recovery scheme for an optical-electrical hybrid phase-locked loop (PLL) operating at 160 Gbit/s. In this scheme, the MLLD functions as a voltage-controlled oscillator to which the error signal is fed back by forming a closed loop with a semiconductor optical amplifier (SOA) used as a phase comparator and with a low-frequency component used as a filter. Cross-gain modulation in the SOA enables high-frequency PLL operation at 160 Gbit/s. A bulk active layer in the SOA with small polarization dependency is the origin of the polarization insensitive clock extraction. Testing of all-optical clock extraction on an OTDM transmission test bed of 254-km field-installed fibers (Dojima-Keihanna, 63.5 km, and four spans) at 160 Gbit/s showed that the measured root-mean-square timing jitter of the recovered clock signal was as low as 240 fs. This clock extraction scheme is thus practical for use in OTDM systems operating at over 100 Gbit/s.
We report on various types of ultrafast all-optical signal processing with hybrid-integrated Symmetric-Mach-Zehnder (HI-SMZ) all-optical switches driven by 40-Gb/s or 40-GHz optical pulses. To operate HI-SMZ switches with such high-repetition excitation, we use longer semiconductor optical amplifiers (SOAs) as nonlinear phase shifters than we previously used. We demonstrate that extending the SOA length is useful for increasing carrier injection and thus enhancing the nonlinear phase shift in SOAs. We show 3R regeneration and wavelength conversion at 42 Gb/s using HI-SMZ switches with longer SOAs. We also show error-free optical demultiplexing of 168- or 336-Gb/s signal pulses with HI-SMZ switches driven by 42-GHz control pulses.
We demonstrate various types of ultrafast all-optical signal processing with Symmetric-Mach-Zehnder (SMZ) all-optical switches incorporating semiconductor optical amplifiers. By using a hybrid-integrated SMZ switch, error-free operations of 336-Gb/s demultiplexing, 42-Gb/s pulse regeneration, and 42-Gb/s wavelength conversion have been achieved. We have also verified the capability of higher bit rate operation by showing 84-Gb/s pulse regeneration and 168-Gb/s wavelength conversion with the variants of the SMZ switch.
Conference Committee Involvement (3)
Optoelectronic Integrated Circuits X
23 January 2006 | San Jose, California, United States
Optoelectronic Integrated Circuits IX
25 January 2005 | San Jose, California, United States