Ki-Hong Yoon

2.5-Gb/s hybridly-integrated tunable external cavity laser using a superluminescent diode and a polymer Bragg reflector

We presented a hybridly-integrated tunable external cavity laser with 0.8 nm mode spacing 16 channels operating in the direct modulation of 2.5-Gbps for a low-cost source of a WDM-PON system. The tunable laser was fabricated by using a superluminescent diode (SLD) and a polymer Bragg reflector. The maximum output power and the power slope efficiency of the tunable laser were 10.3 mW and 0.132 mW/mA, respectively, at the SLD current of 100 mA and the temperature of 25 degrees C. The directly-modulated tunable laser successfully provided 2.5-Gbps transmissions through 20-km standard single mode fiber. The power penalty of the tunable laser was less than 0.8 dB for 16 channels after a 20-km transmission. The power penalty variation was less than 1.4 dB during the blue-shifted wavelength tuning.

Tunable External Cavity Laser by Hybrid Integration of a Superluminescent Diode and a Polymer Bragg Reflector

We report a tunable external cavity laser (T-ECL) using a superluminescent diode (SLD) and a polymer Bragg reflector with 0.8-nm mode spacing 25 channels operating in the direct modulation of 2.5 Gb/s for a low-cost source of a wavelength division multiplexed passive optical network (WDM-PON) system. The maximum output power is 12.2 mW and the slope efficiency of the T-ECL is about 0.12-0.17 mW/mA in the tuning range of 20 nm at the SLD current of 50 mA and at the temperature of 25°C. The T-ECL successfully operated in the direct modulation for 2.5-Gb/s transmission through 20-km standard single-mode fiber. The power penalty of the T-ECL is less than 0.8 dB for 25 channels after the 20-km transmission. The power penalty variation is less than 1.5 dB in the wavelength-tuning range of 20 nm. The performance of the T-ECL satisfies the requirements of the WDM-PON system.

Monolithically Integrated Tunable Laser Using Double-Ring Resonators With a Tilted Multimode Interference Coupler

A monolithically integrated tunable semiconductor ring laser consisting of a semiconductor optical amplifier and two ring resonators with tilted multimode interference (MMI) couplers is presented. The characteristic response of the ring resonators is discussed for various cross coupling strengths by adjusting the angle of the tilted MMI couplers. The ring laser has a wavelength tuning range of 11 nm and a sidemode suppression ratio larger than 40 dB for a cross coupling strength of 0.09. The peak power of the laser is larger than -3 dBm for chip-to-fiber coupling.

Tunable external cavity laser employing uncooled superluminescent diode.

We have fabricated a tunable external cavity laser (T-ECL) based on a superluminescent diode and a polymeric waveguide Bragg reflector, providing a cost-effective solution for wavelength division multiplexing-passive optical network (WDM-PON) systems. The wavelength of the T-ECL is tuned through 100 GHz-spacing 16 channels by the thermo-optic tuning of the refractive index of the polymer waveguide at a low input power of 70 mW. The maximum output power and the slope efficiency of the uncooled diode at 20 (75) degrees C are 8.83 (3.80) mW and 0.107 (0.061) W/A, respectively. The T-ECL operated successfully in the direct modulation for 1.25 Gbit/s transmissions over 20 km.

10-Gb/s direct modulation of polymer-based tunable external cavity lasers

We demonstrate a directly-modulated 10-Gb/s tunable external cavity laser with a polymer Bragg reflector and a high speed superluminescent diode. 20 km transmission through the standard single mode fiber was carried out with a power penalty of less than 2.8 dB..

L-band tunable external cavity laser based on 1.58 μm superluminescent diode integrated with spot-size converter

We report a 1.58 μm superluminescent diode (SLD) with a spot-size converter (SSC) designed and fabricated as a light source for a tunable external cavity laser (T-ECL). The active section of the SLD is fabricated by using a planar buried heterostructure (PBH) for low-threshold current and high-output power operation at a low injection current. The SSC structure of the SLD is designed to possess a buried deep-ridge waveguide (BD-RWG) and show a beam of less divergence. The full-width at half maximum (FWHM) of the horizontal and vertical far-field patterns (FFPs), due to the beam of the less divergence, are 14° and 13°, respectively. We also confirm that an L-band T-ECL employing the SSC SLD operates well enough to prove the characteristics of high performance.

2.5 Gbps Direct Modulation of Reflective Semiconductor Optical Amplifier for Wavelength Division Multiplexing Passive Optical Network Colourless Sources

We present fabrication results of a planar-buried-heterostructure (PBH)-type reflective semiconductor optical amplifier (R-SOA). Active and passive waveguides forming R-SOA were integrated by butt-coupling. The optical gain and 3 dB amplified spontaneous emission (ASE) bandwidth were about 25 dB and 35 nm, respectively. The polarization-dependent gain (PDG) was about 0.8 dB. We could obtain a clearly opened eye diagram under 2.5 Gbps direct modulation. In a bit-error-rate (BER) test, the receiver sensitivity and power penalty after 20 km transmission were about -27 dBm and 2 dB, respectively.

Directly Modulated Tunable External Cavity Laser Transmitter Optical Sub-Assembly

A compact-size and low-cost tunable external cavity laser transmitter optical sub-assembly with butt-coupled superluminescent diode and polymer Bragg reflector (PBR) is described. The output wavelength of the laser is widely tuned over 16 nm by a heater of the PBR and is finely tuned by a phase of the PBR. The threshold current and output power slope of the laser are 8 mA and 0.117 W/A, respectively, at the temperature of 25 °C. The directly-modulated tunable laser provides 2.5-Gb/s transmission through a 80-km standard single-mode fiber without an error-flow by controlling the phase power of the PBR and its dispersion power penalty is .

Ring-resonator-integrated tunable external cavity laser employing EAM and SOA.

We propose and demonstrate a tunable external cavity laser (ECL) composed of a polymer Bragg reflector (PBR) and integrated gain chip with gain, a ring resonator, an electro-absorption modulator (EAM), and a semiconductor optical amplifier (SOA). The cavity of the laser is composed of the PBR, gain, and ring resonator. The ring resonator reflects the predetermined wavelengths into the gain region and transmits the output signal into integrated devices such as the EAM and SOA. The output wavelength of the tunable laser is discretely tuned in steps of about 0.8 nm through the thermal-optic effect of the PBR and predetermined mode spacing of the ring resonator.

Fiber Length Measurement Technique Employing Self-Seeding Laser Oscillation of Fabry–Perot Laser Diode

A simple fiber length measurement technique has been proposed and demonstrated that uses the self-seeding laser oscillation of a Fabry–Perot laser. We measured the length of an optical fiber from the modulation frequency changes required to induce single-mode laser oscillations through an optical closed-loop including the fiber and the laser diode. The maximum error of the proposed technique was less than 0.24% for various fiber lengths from 0.1 to 75 km.