Abstract: A reflective semiconductor optical amplifier (RSOA) and an operating system based on a downstream optical signal reuse method with feed-forward current injection are provided. The RSOA has two active regions and includes a reflecting plane that reflects an input optical signal; and an optical amplifying semiconductor including a rear portion, which is positioned at a side of the reflecting plane and to which a signal having polarity opposite to that of the input optical signal is injected, and a front portion, which is positioned at a side opposite to the side of the rear portion facing the reflecting plane and which the input optical signal is passed though and a signal used to modulate a reflected input optical signal from the reflecting plane to an output optical signal is injected into.

Abstract: A Reflective Semiconductor Optical Amplifier (RSOA) for compensating for light loss in an optical link, an RSOA module for improving polarization dependency using the RSOA, and a Passive Optical Network (PON) for increasing economical efficiency and practical use of a bandwidth using the RSOA are provided. The PON includes a central office comprising a plurality of optic sources transmitting a downstream signal and a plurality of first receivers receiving an upstream signal; at least one optical network terminal (ONT) including a second receiver receiving the downstream signal and an RSOA which receives the downstream signal, remodulates the downstream signal into the upstream signal, and transmits the upstream signal in loopback mode; and a remote node interfacing the central office with the ONT. The upstream signal and the downstream signal are transmitted between the remote node and the ONT via a single optical fiber. The remote node includes an optical power splitter at its port connected to the ONT.

Abstract: Provided is an athermal external cavity laser (ECL), whose output optical power and output wavelength can be kept regular irrespective of temperature changes without using additional temperature controlling components. The ECL comprises: a semiconductor amplifier; an optical fiber comprising a core in which a Bragg grating is formed and a cladding surrounding the core; and a thermosetting polymer that fixes the optical fiber to a ferrule and has a negative thermooptical coefficient, wherein the thickness of the cladding surrounding the core in which the Bragg grating is formed is smaller than the portion of the cladding surrounding the portion of the core where the Bragg grating is not formed, and the thermosetting polymer the negative thermooptical coefficient surrounds the cladding.

Abstract: Hybrid-type external cavity lasers designed to have a semiconductor laser diode mounted on a planar waveguide platform by a flip-chip bonding method. The temperature independent external cavity laser comprises a semiconductor laser diode, a planar waveguide platform, and a thin film multi-layered reflection filter. The semiconductor laser diode includes an active region to generate light, and at least one light-emitting surface. The planar waveguide platform includes a substrate, a metallic pattern formed on a predetermined region of the substrate, a waveguide structure, and a trench portion. The waveguide structure comprises a lower clad layer, a core, and an upper clad layer sequentially stacked in this order on a region of the substrate excluding the predetermined region formed of the metallic pattern. The trench portion has opposite side surfaces on which the core is exposed.

Abstract: A hybrid type integrated optical device has a semiconductor laser mounted on a planar waveguide platform by flip-chip bonding. The optical device comprises a semiconductor laser and a planar waveguide platform. The semiconductor laser includes a first structure, which has an active region and a light emission surface formed on at least one side surface of the first structure, and a second structure, which is formed below the first structure and has upper surfaces exposed at the light emission surface of the first structure and/or to a surface opposite to the light emitting surface. The planar waveguide platform includes a substrate, a lower clad layer, a core layer, and an upper clad layer, being sequentially stacked on the substrate. The semiconductor laser is flip-chip bonded on the substrate, such that the exposed upper surfaces of the second structure contact the upper surface of the upper clad layer.

Abstract: Disclosed herein is a tunable wavelength optical transmission module, the wavelength of which can be tuned over the wide wavelength region of a C band and which can be implemented at a low price and, thus, can be applied to an optical network terminal. Bragg gratings having different grating periods are arranged in parallel or series and the temperatures of Bragg grating regions are then controlled, so that the wavelength of an optical signal can be tuned over a wide wavelength range through the small variation in temperature.