Abstract: Provided is a gain-clamped fiber amplifier for amplifying the magnitude of an input optical signal in an optical communication system. The gain-clamped fiber amplifier includes a first amplifier for amplifying a predetermined optical signal and a second amplifier for compensating for a noise figure characteristic of the first amplifier and for separating remaining pumping light whose intensity changes in accordance with an optical signal. Therefore, it is possible to improve the noise figure and dynamic range characteristics and the performance of the amplifier.

Abstract: Provided is an optical fiber. The optical fiber includes a core and a cladding, the core containing a first element for inducing non-linear Raman phenomenon, either of the core and the cladding containing a second element which is a rare earth element, wherein when the optical fiber is pumped by two pumping light sources having different wavelengths with each other, the optical signals in the first and third band are Raman-amplified by the first element and the signals in the second band are amplified by a direct transition of the second element.

Abstract: Provided is a gain-clamped fiber amplifier for amplifying the magnitude of an input optical signal in an optical communication system. The gain-clamped fiber amplifier includes a first amplifier for amplifying a predetermined optical signal and a second amplifier for compensating for a noise figure characteristic of the first amplifier and for separating remaining pumping light whose intensity changes in accordance with an optical signal. Therefore, it is possible to improve the noise figure and dynamic range characteristics and the performance of the amplifier.

Abstract: The invention relates to a hard decision demodulation of a square type of a quadrature amplitude modulation signal, in particular, to a hard decision demodulation method and apparatus capable of performing fast and accurate demodulation, by demodulating a received signal in bit unit when demodulating it. In a hard decision demodulation method of a square type of quadrature amplitude modulation signal, by determining in bit unit, not in symbol unit a corresponding output value from a quadrature phase component value and an in-phase component value, it is possible to develop a more useful demodulation technique and to give a secondary function by independently processing each bit, according to the demodulation of bit unit. Further, the invention can be constituted of merely a comparison circuit without having arithmetic in demodulation process, and therefore, can enhance flexibility of actual configuration and processing speed.

Abstract: The present invention relates to a demodulation method using soft decision for QAM (Quadrature Amplitude Modulation). In a soft decision method for demodulation of a received signal of square QAM comprised of the same phase signal component and a orthogonal phase signal component, the demodulation method using soft decision has a characteristic wherein the processing speed is improved, and the manufacturing expense is reduced by gaining a condition probability vector value, which is each soft decision value, corresponding to a beat position of hard decision using a function which includes a condition judgement operation from a orthogonal phase component value of a received signal and the same phase component value.

Abstract: The present invention is a thulium doped silicate glass having an excellent fluorescent emission in the 1.4 ?m band, and the usage thereof. The silicate glass of this invention includes: 65˜95 mol % SiO2; 0.5˜30 mol % bivalent metal oxide consisting of one or more material selected from ZnO, BaO, SrO and PbO; and 1˜15 mol % of SnO2 or TiO2, wherein 3˜30 mol % oxygen of the glass composition are replaced with fluorine, and 0.01˜1 mol % of thulium ions are doped, and the fluorescence lifetime of the 3H4 level of the Tm3+ is more than 50 ?s. The silicate glass can be easily formed into a waveguide, such as optical fiber, and it has an excellent ability to splice with the optical fiber for transmission. They have excellent chemical durability and the characteristic of 1.4 ?m band fluorescent emission by suppressing the non-radiative transition through multi-phonon relaxation. Thus they have long fluorescence lifetime of the 3H4 of Tm3+.

Abstract: The present invention relates to a transmission optical fiber. The transmission optical fiber including a core and a cladding made of SiO2 is characterized in that GeO2 and F are doped in SiO2 of the core and the cladding. Therefore, a high Raman gain coefficient could be obtained while a desired dispersion value and a non-linearity are maintained, by controlling the refractive index of the core and the cladding. Further, the pump power of the laser diode could be reduced and the cost of the laser diode could be lowered accordingly. In addition, the life of the laser diode is extended since the laser diode needs not to be operated at a high output.

Abstract: The present invention relates to a main wavelength band of a pump light source capable of improving the pump efficiency while using 1.6 ?m fluorescence emitted from Ho3+:5I5?5I7 transition as an optical amplifier, and an assistant pump wavelength band capable of accomplishing population inversion between 5I5 level and 5I7 level to improve the signal gain characteristics of such amplifier. The optical amplifier using optical materials to which holmium or holmium and terbium, holmium and europium, holmium and neodymium or holmium and dysprosium, etc. are doped can be pumped using a light source that emits light of 11,200˜11,500 cm?1 or a light source that emits light of 6,000˜6,500 cm?1.

Abstract: A multiple optical fiber coupler manufacturing apparatus which can manufacture a plurality of the optical fiber couplers is disclosed. The multiple optical fiber coupler manufacturing apparatus comprises multiple micro torch for heating portions of a plurality of optical fibers so as to fuse the optical fibers two by two; multiple optical fiber holders symmetrically arranged on the basis of said multiple micro torch, for fixing the plurality of the optical fibers two by two at a same interval; and a carrying stage having said multiple micro torch and said multiple optical fiber holders mounted thereon such that said multiple optical fiber holder can be moved.

Abstract: The present invention relates to a transmission optical fiber. The transmission optical fiber including a core and a cladding made of SiO2 is characterized in that GeO2 and F are doped in SiO2 of the core and the cladding. Therefore, a high Raman gain coefficient could be obtained while a desired dispersion value and a non-linearity are maintained, by controlling the refractive index of the core and the cladding. Further, the pump power of the laser diode could be reduced and the cost of the laser diode could be lowered accordingly. In addition, the life of the laser diode is extended since the laser diode needs not to be operated at a high output.

Abstract: The present invention relates to a main wavelength band of a pump light source capable of improving the pump efficiency while using 1.6 &mgr;m fluorescence emitted from Ho3+:5I5→5I7 transition as an optical amplifier, and an assistant pump wavelength band capable of accomplishing population inversion between 5I5 level and 5I7 level to improve the signal gain characteristics of such amplifier. The optical amplifier using optical materials to which holmium or holmium and terbium, holmium and europium, holmium and neodymium or holmium and dysprosium, etc. are doped can be pumped using a light source that emits light of 11,200˜11,500 cm−1 or a light source that emits light of 6,000˜6,500 cm−1.

Abstract: The present invention is a thulium doped silicate glass having an excellent fluorescent emission in the 1.4 &mgr;m band, and the usage thereof. The silicate glass of this invention includes: 65˜95 mol % SiO2; 0.5˜30 mol % bivalent metal oxide consisting of one or more material selected from ZnO, BaO, SrO and PbO; and 1˜15 mol % of SnO2 or TiO2, wherein 3˜30 mol % oxygen of the glass composition are replaced with fluorine, and 0.01˜1 mol % of thulium ions are doped, and the fluorescence lifetime of the 3H4 level of the Tm3+ is more than 50 &mgr;s. The silicate glass can be easily formed into a waveguide, such as optical fiber, and it has an excellent ability to splice with the optical fiber for transmission. They have excellent chemical durability and the characteristic of 1.4 &mgr;m band fluorescent emission by suppressing the non-radiative transition through multi-phonon relaxation. Thus they have long fluorescence lifetime of the 3H4 of Tm3+.

Abstract: A dispersive optical fiber having variable core-cladding refractive index differences depending on wavelength is provided. The dispersive optical fiber includes a core made of silica doped with a first dispersive material, and a cladding made of silica doped with a second dispersive material, wherein the refractive indices of the first and the second dispersive materials cross each other at a predetermined cross wavelength. The first and second dispersive materials include boron and fluorine. The dispersive optical fiber is attained by doping each dispersive material into the core and the cladding, respectively, thereby minimizing transmission loss, and is capable of being coupled to general optical fibers.

Abstract: The present invention relates to a hermetic rotary compressor. More particularly, since the conventional rotary compressor has problems that the effect of a surge recess for reducing noises due to pressure pulsation is insufficient, and it is impossible to obtain the maximum compression efficiency, the present invention is constructed such that noises due to pressure pulsation can be reduced to the maximum and at the same time the compressive driving force required for compressing gaseous refrigerant is decreased to thereby improve the compression efficiency.