Yongsoon Baek

Fabrication of 10-Channel Polymer Thermo-Optic Digital Optical Switch Array

We present a 10-channel polymer thermo-optic digital optical switch (DOS) array with very low optical crosstalk. The 10-channel DOS array has a crosstalk-improved structure in which radiation-type attenuators are integrated in a series with a conventional 1 times 2 DOS. It is fabricated using a quartz substrate on which grid patterns for dispersion of stray light are formed to reduce the optical crosstalk. The measured crosstalk values are as low as -45 dB at a low electrical power of 50 mW. Insertion losses of less than 1.35 dB are achieved for all channels.

Optical components for 100G ethernet transceivers

Optical sub-assemblies for 100G Ethernet transceivers are presented. Compact and low cost 100G TOSA and ROSA for the second generation CFP2 type transceivers are designed and fabricated.

N × N polymer matrix switches using thermo-optic total-internal-reflection switch.

We have developed fully non-blocking optical matrix switches using a thermo-optic polymer 1 × 2 total-internal-reflection (TIR) switch as a unit switching element. The TIR switch consists of crossed multimode polymer waveguides and an offset heater electrode at the switching node. The fabricated 4 × 4 and 8 × 8 optical matrix switch chips show excellent switching performances. The insertion losses are less than 2.5 and 4.5 dB for the 4 × 4 and 8 × 8 matrix switches, respectively, and their switching isolations during a turned-off state are higher than 38 dB. The switching time is about 3 ms, and the power consumption for each switching element is below 30 mW. Compact integration of the 4 × 4 and 8 × 8 switch chips is achieved at sizes of 25 mm × 4.25 mm, and 42.4 mm × 5 mm, respectively, through an optimization of the waveguide and heater geometries.

Fabrication of a TFF-Attached WDM-Type Triplex Transceiver Module Using Silica PLC Hybrid Integration Technology

An optical triplex transceiver (TRx) module, which consists of thin-film filter (TFF)-attached wavelength-division multiplexer (WDM) and photodiode (PD) carriers, has been fabricated using a silica planar lightwave circuit (PLC) hybrid integration technology. Two types of TFFs were attached to a diced sidewall of a silica-terraced PLC platform to realize the TFF-attached WDM. The PD carriers with a 45deg mirror, on which receiving surface-illuminated PDs were bonded, were assembled with the PLC platform to form receiver (Rx) parts. As the main performances of the packaged TRx module, a very clear transmitter (Tx) eye pattern and minimum Rx sensitivity of -25.7 dBm were obtained under a 1.25-Gb/s Tx-Rx operation for digital applications. For an analog Rx application, a module responsivity of about 0.8 A/W was achieved, and a second-order intermodulation distortion value of less than -70 dBc at an optical modulation index of 40% was obtained under a two-tone test of 400 and 450 MHz

200 GHz-spacing 8-channel multi-wavelength lasers for WDM-PON optical line terminal sources.

We have fabricated modules of 8-channel multi-wavelength lasers (MWLs) with a wavelength separation of 200 GHz for the wavelength division multiplexed-passive optical network (WDM-PON) optical line terminal sources. The variation in the output power is minimized by inserting silicone between the superluminescent diode (SLD) and the silica waveguide. The wavelength shift of each channel is less than 0.21 nm from the ITU grid and can be controlled in the range of 0.36 nm without any reductions of the output power by a tuning heater. MWLs operated successfully in the direct modulation for 1.25 Gbit/s transmissions over 20 km.

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We present a novel 2 × 2 polymer thermo-optic digital optical switch (DOS) using the total-internal-reflection (TIR) effect. The switch consists of four 1 × 2 TIR-DOSs cascaded with each other. These TIR-DOSs have two branched multimode waveguides and an offset heater electrode in the branched region. Our switch does not have any bent waveguides, and has tapered waveguides and single-mode waveguides only in the input-output fiber coupling region. The fabricated 2 × 2 TIR-DOSs exhibit excellent properties, with very low insertion losses of <; 1.4 dB and switching isolations of >; 50 dB in both turned-off and turned-on states.

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We propose and demonstrate very compact multiwavelength lasers (MWLs) with a novel configuration designed to remove the mode hopping in the modulation region and separate the wavelength-tuning of each channel for cost-effective optical line termination sources in the wavelength-division-multiplexing passive optical network. The mode hopping of MWLs in the modulation region was eliminated by wavelength trimming using a tuning heater. The MWLs operated successfully in direct modulation for 1.25-Gb/s transmission over 20 km.

2 Polymer Thermo-Optic Digital Optical Switch Using Total-Internal-Reflection in Bend-Free Waveguides

We present a cost-effective 25-Gb/s electro-absorption modulator integrated laser (EML) transmitter optical sub-assembly (TOSA) using all-in-one flexible printed circuit board (FPCB) wiring and a metal optical bench (MOB). For a low cost and high bandwidth TOSA, internal and external wirings and feed-through of the TOSA to transmit radio-frequency (RF) signal are configured all-in-one using the FPCB. The FPCB is extended from an exterior of the TOSA package up to an EML chip inside the package through the slit formed on a rear sidewall of the package and die-bonded on the MOB. The EML TOSA shows a modulated output power of more than 3.5 dBm and a clear eye pattern with a dynamic extinction ratio of ~8.4 dB at a data rate of 25.78 Gb/s.

Wavelength-Tuning of Hybrid Integrated Multiwavelength Lasers Using a Heater

A very compact 16-channel 200 GHz-spacing transmitter module was fabricated for wavelength division multiplexing-passive optical network (WDM-PON) optical line termination (OLT) source. The transmitters are composed of reflection gratings and hybrid integrated superluminescent laser diodes (SLD) to construct 16-channel external cavity lasers (ECLs) on the planar lightwave circuit (PLC) chip.

A cost-effective 25-Gb/s EML TOSA using all-in-one FPCB wiring and metal optical bench.

We report 10 Gbit s−1 operation of an electroabsorption modulator (EAM) integrated with a distributed Bragg reflector (DBR) laser. The selective area growth technique was first employed in the 10 Gbit s−1 EAM fabrications to grow an active layer in the regions of the laser and the modulator. High side mode suppression ratios (SMSRs) over 45 dB and a 3 dB bandwidth of 12 GHz were observed. A clearly opened eye-diagram was also observed with 10 Gbit s−1 non-return to zero (NRZ) modulation signals.