Abstract: An apparatus and method for monitoring quality of an optical signal in an optical network based on wavelength division multiplexing optical transmission technology are provided, which are capable of monitoring the quality of an optical signal with higher accuracy. The apparatus includes: a signal extractor extracting an optical signal having a specific wavelength from input optical signals; an optical-electrical converter converting the extracted optical signal having the specific wavelength into an electrical signal; an overhead parser extracting a part of an overhead of the electrical signal to parse whether or not the quality of the signal is degraded; and a controller monitoring the quality of the optical signal according to the parsing result of the extracted overhead and restoring the optical signal whose quality is lower than a predetermined reference value.

Abstract: An apparatus and method for protection switching of an optical channel at each node in an optical network based on wavelength division multiplexing optical transmission technology are provided. The method can be applied to any node having at least two optical fiber inputs and outputs. The apparatus includes: a splitter receiving an electrical signal and splitting the received electrical signal into a plurality of electrical signals which are substantially identical to the received electrical signal; an output switching unit selecting output paths of the electrical signals split by the splitter according to an optical channel path control command of the optical network; and a plurality of optical transponders being assigned to the respective output paths of the electrical signals, converting the electrical signal input by the selection of the output switching unit to an optical signal, and transmitting the converted optical signal to another node of the optical network.

Abstract: Provided is a multi-ring network operating method of cross-connecting at least two ring networks, the method including connecting an input working ring and an input protection ring of a ring network to an output working ring and an output protection ring of another ring network and then performing cross-connection between the same or different ring networks by using a multi-dimensional cross-connect apparatus. In the multi-ring operating method, a plurality of ring networks can be connected regardless of the protection method used by the ring networks, and the original protection method of each ring network can remain after they are connected.

Abstract: Provided is a hybrid optical amplifier using a gain-clamped semiconductor optical amplifier enabling Raman amplification. The hybrid optical amplifier comprises a spool of optical fiber used as transmission line in the optical communication, a GCSOA amplifying optical signal input via the optical fiber and generating a self-oscillation laser beam for gain-clamping through the gain medium, and a backward pumping Raman optical amplifier inducing Raman amplification by emitting the self-oscillation laser beam generated by the GCSOA into the optical fiber. Therefore, the Raman amplification can be obtained with a relatively simple structure using the GCSOA.

Abstract: Provided is an optical network node device. According to the optical network node device, a planar lightwave circuit (PLC) based or a blocker based 4-terminals ROADM can be used in a node of at least degree 3, a proceeding direction of a wavelength channel can be changed in an electrical cross connect switch, and transmission in a unit smaller than a wavelength channel can be cross connected, dropped, and added, or transmission capacity can be redistributed in the electrical cross connect switch. Accordingly, efficient transmission in a small capacity and large capacity transmission of a wavelength channel can be performed simultaneously, and thus an optical network can be effectively managed. Also, since the node of at least degree 3 uses the PLC based or a blocker based reconfigurable optical add drop multiplexer (ROADM), the node of at least degree 3 can use the same ROADM module as a node of degree 2. Accordingly, the optical network node device has an advantage in manufacturing and managing a node.

Abstract: An optical node capable of supporting a mesh-type optical network is provided.

Abstract: Provided are a photonic cross-connector system, a wavelength division multiplexing (WDM) system using the photonic cross-connector system, and an optical communication network based on the WDM system. The photonic cross-connector system includes: an optical coupler branching an input optical signal into a plurality of paths; a wavelength selective switch (WSS) extracting at least one wavelength signal from the input optical signal and outputting the extracted wavelength signal to at least one port; a WDM multi-casting apparatus simultaneously copying and reproducing the input optical signal into different wavelengths and changing modulation methods of the input optical signal into different types of modulation methods; an optical transmitter and/or receiver branching and coupling the input optical signal; and a control system controlling the optical coupler, the WSS, the WDM multicasting apparatus, and the optical transmitter and/or receiver.

Abstract: Provided are a Raman amplifier and a Raman pumping method. A light source unit outputs a pumping light having a wavelength that periodically changes. A light intensity control unit varies a light intensity of the pumping light using the pumping light to improve the gain flatness of a Raman gain. A control unit directs the light intensity control unit to control the light intensity of the pumping light in synchronization with changes in the wavelength of the pumping light.

Abstract: A dispersion compensating fiber (DCF), which is an amplification medium of an S-band discrete Raman amplifier (RA), has a trapezoid core, an inner cladding surrounding the trapezoid core; and an outer cladding surrounding the inner cladding. A ring is disposed between the inner cladding and the outer cladding. The refractive index plotted across the diameter of the trapezoid core as a function of distance is substantially trapezoidal in shape. The difference in refractive index between the trapezoid core and the outer cladding is 1.2 to 1.6%; between the inner cladding and the outer cladding is 0.4 to 0.8%; and between the ring and the outer cladding is 0.2 to 0.6%. The thickness of the ring is 0.8 to 1.2 times the radius of the trapezoid core, and the thickness of the inner cladding is 1 to 3 times the radius of the trapezoid core.

Abstract: A method for realizing, in a fiber amplifier with three stages of amplifiers, automatic gain control in which a constant gain is obtained when channels are varied, and automatic level control in which a constant output per channel is obtained when a light power is varied because of variations in span loss. A light power or another light power of a specific wavelength is monitored to determine when variations in these light powers take place, current values of pump laser diodes appropriate for an input is read from a lookup table, and pump laser diodes are driven. During this operation, a pump power of the first stage amplifier is constantly maintained, and those of the second or third stage amplifier are controlled.

Abstract: The present invention provides an apparatus and method for compensating for the variation of a gain spectrum attributable to the temperature variation of a fiber amplifier, and a long-wavelength band dispersion-compensating hybrid amplifier equipped with the gain spectrum compensating apparatus. The apparatus includes a DCF located between a first amplification stage and a second amplification stage to compensate for dispersion of an optical signal output from the first amplification stage and perform Raman amplification of the optical signal using input pumping light; at least one pumping light provision means for providing forward or backward pumping light to the DCF; first and second temperature detection means for detecting temperature variations of the first and second amplification stages, respectively; and control means for controlling intensity of the pumping light of the pumping light provision means according to the detected temperature variations.

Abstract: Provided are a Raman amplifier and a Raman pumping method. A light source unit outputs a pumping light having a wavelength that periodically changes. A light intensity control unit varies a light intensity of the pumping light using the pumping light to improve the gain flatness of a Raman gain. A control unit directs the light intensity control unit to control the light intensity of the pumping light in synchronization with changes in the wavelength of the pumping light.

Abstract: Optical fiber amplifier with wide input power dynamic range is employed to make a first gain block and an optical fiber pumped by Raman pump have opposite spectral gain profiles each other, thereby obtaining flat output gain profile. The optical fiber amplifier includes: a first and a second gain blocks, wherein each gain block has a gain medium and at least one optical pump; an optical fiber disposed between the first and the second gain blocks; a Raman pump for generating a pumping light; and a coupling means for coupling the pumping light to the optical fiber.

Abstract: A method for realizing, in a fiber amplifier with three stages of amplifiers, automatic gain control in which a constant gain is obtained when channels are varied, and automatic level control in which a constant output per channel is obtained when a light power is varied because of variations in span loss. A light power or another light power of a specific wavelength is monitored to determine when variations in these light powers take place, current values of pump laser diodes appropriate for an input is read from a lookup table, and pump laser diodes are driven. During this operation, a pump power of the first stage amplifier is constantly maintained, and those of the second or third stage amplifier are controlled.

Abstract: This invention relates to a laser gyroscope. This invention provides a direction-switched mode-locked laser gyroscope, comprising: a laser resonator including a laser gain medium and an optical path, one end of the resonator being connected to a reflector and the other end of the resonator being composed of a Sagnac loop; wherein the gyroscope is operated by pulses generated from an optical switch connected to the Sagnac loop. The laser gyroscope according to the invention has a better durability than a conventional He-Ne type laser gyrocope. It can produce an output signal which can be processed more simply than that of the interferometric fiber-optic gyroscope since the output signal is characterized by frequencies corresponding to the rotation rate. The gyroscope operates to produce a pulse output, reducing lock-in effect compared with a gyroscope producing continuous wave output.