Abstract: Provided are a marine testbed and a marine test method for providing marine verification and securing a track record of an eco-friendly propulsion system for a ship, wherein the marine testbed and the marine test method test and evaluate applicability of a hybrid propulsion system to the ship and facilitate securing of a track record, the hybrid propulsion system utilizing a battery, a fuel cell, a zero-carbon fuel engine, a zero-carbon fuel mixed-combustion engine, and a heterogeneous eco-friendly alternative fuel for the ship which are essential for developing an eco-friendly ship.

Abstract: An electroabsorption (EA) duplexer in which an optical amplifier, a photodetector, and an optical modulator are monolithically integrated to obtain a high radio frequency (RF) gain in radio-over fiber (RoF) link optical transmission technology is provided. The EA duplexer includes a substrate, a separation area, an optical detection/modulation unit, and an optical amplification unit. The separation area includes a first epitaxial layer formed of at least one material layer on the substrate. The first epitaxial layer functions as a first optical waveguide. The optical detection/modulation unit includes a second epitaxial layer formed of at least one material layer on the first epitaxial layer to detect and modulate an optical signal. The second epitaxial layer functions as a second optical waveguide. The optical amplification unit includes the second optical waveguide and a third epitaxial layer formed of at least one material layer on the second epitaxial layer to amplify an optical signal.

Abstract: Provided is an optical module used in a communication system employing a radio over fiber (ROF) technology delivering a radio frequency (RF) signal through an optical fiber. The optical module includes: an optical device; a signal line for transporting a radio frequency (RF) signal input from an external circuit to the optical device; and a resistor separately disposed from the signal line and having one end connected with the optical device, wherein the input impedance seen from the signal line is matched by the resistor. A bias voltage supplied to operate the optical device is applied through an inductor connected to the signal line between the optical device and a filter. Here, the filter formed by a pattern of the signal line prevents the bias voltage from being supplied to the external circuit. In order to amplify the RF signal input from the external circuit, an amplifier may be connected between the external circuit and the filter.

Abstract: Provided is a double waveguide electroabsorption modulator, in which two spot size converters are integrated between first and second optical waveguides, thereby reducing an insertion loss between an optical fiber and an optical modulator while favorably operating even in high input optical power. Therefore, the electroabsorption modulator can stably operate in higher input optical power while reducing an optical coupling loss and an optical confinement factor (OCF).

Abstract: Provided is an optical module including a microstrip line, a traveling wave type optical device positioned in the end of the microstrip line, and at least one balanced open stub connected to the microstrip line for the impedance matching at a specific frequency such as 40 GHz and 60 GHz. For the fine tuning, laser trimming can be applied to the stub. A transition region is formed between the optical device and the microstrip line. A termination resistor is formed to face the microstrip line with the optical device therebetween. A bandwidth can be controlled at a specific frequency by adjusting a number of the stubs or a value of the termination resistor.

Abstract: An electroabsorption (EA) duplexer in which an optical amplifier, a photodetector, and an optical modulator are monolithically integrated to obtain a high radio frequency (RF) gain in radio-over fiber (RoF) link optical transmission technology is provided. The EA duplexer includes a substrate, a separation area, an optical detection/modulation unit, and an optical amplification unit. The separation area includes a first epitaxial layer formed of at least one material layer on the substrate. The first epitaxial layer functions as a first optical waveguide. The optical detection/modulation unit includes a second epitaxial layer formed of at least one material layer on the first epitaxial layer to detect and modulate an optical signal. The second epitaxial layer functions as a second optical waveguide. The optical amplification unit includes the second optical waveguide and a third epitaxial layer formed of at least one material layer on the second epitaxial layer to amplify an optical signal.

Abstract: Disclosed is an electro-absorption optical modulator using a semiconductor device. The optical modulator makes use of a change in light absorption caused by displacement of an absorption curve depending on a bias voltage applied to the device. Here, a level of the light absorption depending on the bias voltage is expressed as a transfer function of output light to the applied bias, and the transfer function has a non-linear profile due to a characteristic of a material. Unlike signal modulation of a digital optical communication system, an analog optical transmission system can be subjected to deterioration in performance, because the non-linear characteristic of the transfer function for the optical modulator generates signal distortion when an electrical signal is converted into an optical signal. The typical optical modulator has an absorption layer constituted of quantum wells having the same width.

Abstract: Disclosed is a wavelength stabilizing method in which a first QCSE photodetector and a second QCSE photodetector receive a light outputted from a single light source, a first wavelength-photocurrent graph obtained when a selected bias voltage is applied to the first QCSE photodetector and a second wavelength-photocurrent graph obtained when a selected bias voltage is applied to the first QCSE photodetector are overlapped at a predetermined reference wavelength, a photocurrent outputted from the first QCSE photodetector is greater than a photocurrent outputted from the second QCSE photodetector at wavelengths shorter than the overlapped point while the photocurrent outputted from the second QCSE photodetector is greater than the photocurrent outputted from the first QCSE photodetector at wavelengths longer than the overlapped point, and if the photocurrent outputted from the first QCSE photodetector is greater than the photocurrent output from the second QCSE photodetector, output wavelengths are moved to the