Abstract: Provided is a digital twin disaster management system customized to keep safety for urban underground tunnels, including: a sensor sub-system configured to detect environmental information, status information and image information in the urban underground tunnels; a digital twin model management sub-system configured to create and update a virtual space corresponding to the urban underground tunnels using information provided from the sensor sub-system and 3D space, insert various types of attributes into the virtual space, detect tagging information, predict the spread of each disaster, and infer a degree of risk of a management facility; a disaster management sub-system having a control function of conducting centralized supervision by displaying information about components installed in the urban underground tunnels in the metaverse space and recording a situation; and a network sub-system configured to provide the virtual space to a user terminal of an external inspector.

Abstract: Provided is a digital twin disaster management system customized to keep safety for urban underground tunnels, including: a sensor sub-system configured to detect environmental information, status information and image information in the urban underground tunnels; a digital twin model management sub-system configured to create and update a virtual space corresponding to the urban underground tunnels using information provided from the sensor sub-system and 3D space, insert various types of attributes into the virtual space, detect tagging information, predict the spread of each disaster, and infer a degree of risk of a management facility; a disaster management sub-system having a control function of conducting centralized supervision by displaying information about components installed in the urban underground tunnels in the metaverse space and recording a situation; and a network sub-system configured to provide the virtual space to a user terminal of an external inspector.

Abstract: A communication method in a wireless communication system includes receiving, by a resonator unit of a first signal transfer apparatus, a wireless signal transmitted from a transmission apparatus, acquiring resonance energy from the wireless signal using at least one of a matcher unit and the resonator unit of the first signal transfer apparatus, transferring the wireless signal to one end of a transmission line via the matcher unit of the first signal transfer apparatus using the acquired resonance energy, transferring the wireless signal to a second signal transfer apparatus connected to an opposite end of the transmission line, and transmitting the wireless signal to a reception apparatus having a wireless link established with the second signal transfer apparatus using a matcher unit and a resonator unit of the second signal transfer apparatus.

Abstract: A communication method in a wireless communication system includes receiving, by a resonator unit of a first signal transfer apparatus, a wireless signal transmitted from a transmission apparatus, acquiring resonance energy from the wireless signal using at least one of a matcher unit and the resonator unit of the first signal transfer apparatus, transferring the wireless signal to one end of a transmission line via the matcher unit of the first signal transfer apparatus using the acquired resonance energy, transferring the wireless signal to a second signal transfer apparatus connected to an opposite end of the transmission line, and transmitting the wireless signal to a reception apparatus having a wireless link established with the second signal transfer apparatus using a matcher unit and a resonator unit of the second signal transfer apparatus.

Abstract: A method of measuring inter-device relative coordinates performed by a first device communicating with at least one second device belonging to a group to which the first device belongs includes measuring a range between the first device and the second device through communication with the second device; receiving range information between a plurality of second devices from the second device; calculating a plurality of solutions for inter-device relative coordinates using information about the range between the first device and the second device and the range information between the plurality of second devices; and deducing a true solution among the plurality of solutions for the inter-device relative coordinates using coordinates of each of the first device and the at least one second device with respect to a reference origin that is calculated using a Pedestrian Dead Reckoning (PDR) technique.

Abstract: A method of measuring inter-device relative coordinates performed by a first device communicating with at least one second device belonging to a group to which the first device belongs includes measuring a range between the first device and the second device through communication with the second device; receiving range information between a plurality of second devices from the second device; calculating a plurality of solutions for inter-device relative coordinates using information about the range between the first device and the second device and the range information between the plurality of second devices; and deducing a true solution among the plurality of solutions for the inter-device relative coordinates using coordinates of each of the first device and the at least one second device with respect to a reference origin that is calculated using a Pedestrian Dead Reckoning (PDR) technique.

Abstract: An information image display apparatus includes an illuminance sensor sensing illuminance of incident light; a processor for determining a transmittance of a polarizer according to the illuminance sensed by the illuminance sensor, outputting a control signal according to the sensed illuminance, analyzing an entire or partial area of a foreground image of external environment to determine a dominant color of the entire or partial area, and displaying an information image using a color contrasted with dominant color; and a polarizer for selectively transmitting the incident light by adjusting a degree of polarization according to the control signal input from the processor.

Abstract: An apparatus and method for driving an optical source for an optical fiber link monitoring apparatus. The apparatus for driving an optical source for an optical fiber link monitoring apparatus includes a laser part configured to output probe light that corresponds to a bipolar code probe signal; an optical receiver configured to convert reflected light, which has travelled back from an optical fiber link after transmission of the bipolar probe light, into an electrical signal; and a direct-current (DC) canceller configured to remove a DC offset component from the electrical signal generated by the optical receiver.

Abstract: Disclosed is an optical fiber cable monitoring apparatus using a dual light source. The optical fiber cable monitoring apparatus includes: an optical transmitter configured to comprise a first light source and a second light source, which output light of different wavelengths, and to operate the first light source and the second light source to propagate first probe light and second probe light to an optical fiber cable; and an optical receiver configured to comprise a first light receiving module and a second light receiving module, each receiving first reflected light and second reflected light which are reflected from the optical fiber cable.

Abstract: An optical fiber link monitoring apparatus for detecting a failure in an optical fiber link by analyzing a trace of a received signal that has been transmitted to and reflected from said optical fiber link. The optical fiber link monitoring apparatus includes a variable gain amplifier (VGA), an analog/digital converter (ADC), and a controller. The VGA amplifies a gain of the received signal, for which the ADC converts the gain-amplified signal into a digital signal. The controller then analyzes a digital signal trace and adjusts the gain of the VGA according to the analysis result.

Abstract: Provided is a hybrid passive optical network (PON) system. The hybrid PON system of wavelength division multiplexing (WDM)/time division multiplexing (TDM) may include an optical line terminal (OLT) and an optical network unit (ONU). The OLT and the ONU may transmit a signal based on wavelength reuse using a seed light source and a reflective modulator. The light source may include a seed light source having a single wavelength, two seed light sources having different wavelength bands, and a light source having a wavelength tunable characteristic.

Abstract: There are provided a method of allocating upstream bandwidth resources and a method of transmitting upstream data in an orthogonal frequency division multiple access-open optical subscriber network. The method of allocating an upstream bandwidth resource according to an embodiment of the invention includes receiving queue status information from each optical network unit (ONU), and allocating an upstream bandwidth by providing to each ONU a 2-D upstream bandwidth map on a subcarrier-time resource through a frame synchronized at constant cycles, based on the queue status information received from each ONU.

Abstract: A converged passive optical network (CPON) and a data transmission method are disclosed. The CPON is a combination of a time division multiple access-passive optical network (TDMA-PON) and an orthogonal frequency division multiple access-passive optical network (OFDMA-PON) and is able to dynamically controlling a bandwidth for upstream signal transmission through allocation of multiple subcarriers to each single optical network unit (ONU).

Abstract: Provided is a method of selecting a wavelength of an optical network unit including selecting a pre-loaded default wavelength as an available wavelength candidate or the wavelength that has been changed when a preset wavelength changing condition is satisfied as the available wavelength candidate, acquiring frame synchronization for a downstream signal having the same wavelength as the selected available wavelength candidate, and transmitting a registration request message to an optical line terminal (OLT) from which the downstream signal has been transmitted when the frame synchronization is acquired, assigning the available wavelength candidate to an available wavelength used for communication with the OLT and registering the terminal in the OLT when a registration allowance message is received from the OLT.

Abstract: An orthogonal frequency division multiple access-passive optical network including a plurality of optical network units each configured to generate orthogonal frequency division multiplexed signals, which are allocated thereto, based on a central frequency for frequency division multiplexing that is allocated in advance, and to use the generated signals in upstream transmission.

Abstract: Provided is an apparatus and a method for partial monitoring of an optical fiber, wherein the optical fiber monitoring apparatus includes a monitoring light transmitter to continuously output a monitoring light to the optical fiber based on a number of measuring time sections generated by dividing an optical fiber monitoring time section, a monitoring light receiver to receive a monitoring light fed back from the optical fiber, measure a monitoring light received based on different measuring time sections for each monitoring light, and store a result of the measuring in a storage medium, and an optical fiber monitor to monitor a status of the optical fiber based on the result of the measuring stored in the storage medium.

Abstract: A wired/wireless converged media access control (MAC) adaptor and a method for transmitting a frame using the same. The wired/wireless converged MAC adaptor may include a service network interface (SNI) to transmit a MAC frame corresponding to a wired or wireless service, or common public radio interface (CPRI) data, a frame conversion unit to convert, into an orthogonal frequency division multiplexing (OFDM) frame, a wired/wireless converged MAC frame having a common frame structure of the MAC frame corresponding to the wired or wireless service or the CPRI data, and an OFDM interface configured to transmit the OFDM frame to an optical OFDM modem by dynamically allocating sub-carriers based on data transmission characteristics.

Abstract: An optical layer monitoring apparatus and method thereof are provided. According to an embodiment of the present invention, an optical layer monitoring apparatus including an optical time domain reflectometer (OTDR) function so as to monitor an optical path of a passive optical network (PON), and a method for improving accuracy of measured monitoring results using the optical layer monitoring apparatus are provided. Therefore, it is possible to enable a user to continuously detect distortion or attenuation along the optical path, and to quickly recover from the distortion or attenuation along the optical path when distortion or attenuation is detected.

Abstract: A modulation method of an optical modem and a signal transmission apparatus performing the method are disclosed. The modulation method of the optical modem includes an optical interface providing a signal to a light source, a photo detector receiving reflected light by an optical link when output light from the light source based on the provided signal is reflected by the optical link, the photo detector measuring and determining characteristics of the optical link using the reflected light, and the optical modem determining a power level and a modulation method for each subcarrier based on the characteristics of the optical link.

Abstract: Provided are a user-selectable laser and an optical transmitter including the same. The user-selectable laser is an external cavity laser including a semiconductor laser diode for outputting an optical signal, and a wavelength selection filter. The user-selectable laser may allow a user to select a wavelength selection filter which is optically coupled with the semiconductor laser diode and selectively causes oscillation at the wavelength of an optical signal output from the semiconductor laser diode.