Abstract: An optical code division multiplexing module includes a superstructured fiber Bragg grating having equally spaced unit fiber Bragg gratings that convert an optical pulse into an optical chip train with equal inter-chip phase differences. A thermo-module heats or cools the mounting plate to which the superstructured fiber Bragg grating is secured. A temperature sensor measures the temperature of the mounting plate, and a temperature controller adjusts the temperature, thereby adjusting the inter-chip phase difference. The optical code division multiplexing module can be used for both coding and decoding. The inter-chip phase difference defines the code. Operation is stable despite environmental variations, and the code can be changed by changing the temperature setting, without replacement of any physical parts.

Abstract: An optical pulse time spreading device includes S optical pulse time spreading elements that spread input optical pulses into trains of (N×j) chip pulses, where j is an integer greater than zero, S is an integer greater than one, and N is an integer equal to or greater than S. In the chip pulse trains output by the n-th optical pulse time spreading element (n=1, 2, . . . , S), the light in successive chip pulses is shifted in phase by successive integer multiples of the quantity 2?{a+(n?1)/N}, where a is an arbitrary constant (0?a<1). In an optical code-division multiplexing system, this optical pulse time spreading device produces an autocorrelation wave with a high energy and a high signal-to-noise ratio.

Abstract: A method for manufacturing a single stone into a regular dodecahedral ornament or a regular icosahedral ornament, and the ornament manufactured according to the method are provided. The method enables the ornament to be manufactured at low costs with ease without using a complicated, numerically computer-controlled shaping machine. The geometric features determining the faces and ridges of a regular dodecahedron or a regular icosahedron are drawn as cutting base lines on each surface of a cubic workpiece. On a face formed by cutting based on the cutting base lines, new auxiliary cutting lines are sequentially drawn by marking. Then, based on these auxiliary cutting lines and the remaining cutting base lines, a possible cut face is determined, which is in turn cut using a cutting tool. The cutting base lines which are erased after each cutting are complemented by auxiliary cutting lines to find a new possible cut face, which is in turn cut in sequence, thereby manufacturing the regular polyhedral ornament.

Abstract: An optical pulse time spreader which can generate a chip pulse string of which intensity is equalized. The reflectances R1, R2 and Rk of the first, second and k-th (k is an integer which satisfies 3?k?J) unit FBG are given by the following formulae respectively. R1=Pc(constant) ??(a) R2=Pc/(1?R1)2 ??(b) Rk=(Pc1/2?Pk1/2)2/{(1?R1)2·(1?R2)2 . . . (1?Rk-1)2} ??(c-1) Rk=(Pc1/2+Pk1/2)2/{(1?R1)2 ·(1?R2)2 . . . (1?Rk-1)2} ??(c-2) Here Pc is an arbitrary constant, and Pk is an intensity of a triple reflection chip pulse which is output for the k-th time. The formulae (c-1) and (c-2) are the reflectance of the k-th unit diffraction grating when the phase difference between the single reflection chip pulse, which is output for the k-th time, and the triple reflection chip pulse, which is output for the k-th time, is 0 and ? respectively.

Abstract: An optical code division multiplexing communication method includes the steps of: producing a multi-wavelength optical pulse train from wavelength multiplexing pulse; transmitting the multi-wavelength optical pulse train through a transmission line using a time-spreading/wavelength-hopping method; decoding wavelength multiplexing pulse from the multi-wavelength optical pulse train transmitted through the transmission line; compensating delay time differences between individual optical pulses of the multi-wavelength optical pulse train, the delay time differences occurring in the step of transmitting the multi-wavelength optical pulse train through the transmission line; and compensating optical pulse spread in a time direction, which occurs in each of the optical pulses of the multi-wavelength optical pulse train in the step of transmitting the multi-wavelength optical pulse train through the transmission line.

Abstract: An FBG system with lower power supplied to a temperature controller, while allowing for precise temperature control of an FBG grating. The FBG system includes a high temperature FBG-mounting structure and a low temperature FBG-mounting structure, and a housing containing them. The high temperature FBG-mounting structure includes an FBG module and a thermo module. The temperature of the FBG in the FBG module may be made higher than the environmental temperature by supplying heat from a heat-conducting portion to the thermo module. The low temperature FBG-mounting structure includes an FBG module and a thermo module. The temperature of the FBG in the latter FBG module may be made lower than the environmental temperature by supplying heat from the latter thermo module to the heat-conducting portion. The FBG-mounting structures are provided in parallel on the inner bottom surface of the heat-conducting portion, part of the housing.

Abstract: The present invention is an SSFBG with which there are few restrictions on the code that can be set and the overall length of which is short. This SSFBG has four unit FBGs the Bragg reflection wavelengths of which are ?1, ?2, ?3, and ?4 disposed with a part where the unit FBGs overlap one another in the waveguide direction of the optical fiber. The left end of the horizontal axis corresponds to the position of the I/O terminal of the SSFBG and the right end of the horizontal axis corresponds to the terminal on the opposite side from the I/O terminal of the SSFBG. The Bragg reflection wavelengths ?1, ?2, ?3, and ?4 of the four unit FBGs are ?1=1543.28 nm, ?2=1543.60 nm, ?3=1543.92 nm, and ?4=1544.24 nm respectively. Codes (?1, ?2, ?3, and ?4) used in the time-spreading/wavelength hopping system are established for the SSFBG by disposing the four unit FBGs at equal intervals such that the interval therebetween is 12.8 mm.

Abstract: An optical pulse time spreader which can generate a chip pulse string of which intensity is equalized. The reflectances R1, R2 and Rk of the first, second and k-th (k is an integer which satisfies 3?k?J) unit FBG are given by the following formulae respectively. R1=Pc(constant) ??(a) R2=Pc/(1?R1)2 ??(b) Rk=(Pc1/2?Pk1/2)2/{(1?R1)2·(1?R2)2 . . . (1?Rk-1)2} ??(c-1) Rk=(Pc1/2+Pk1/2)2/{(1?R1)2 ·(1?R2)2 . . . (1?Rk-1)2} ??(c-2) Here Pc is an arbitrary constant, and Pk is an intensity of a triple reflection chip pulse which is output for the k-th time. The formulae (c-1) and (c-2) are the reflectance of the k-th unit diffraction grating when the phase difference between the single reflection chip pulse, which is output for the k-th time, and the triple reflection chip pulse, which is output for the k-th time, is 0 and ? respectively.

Abstract: The ratio P/W between the peak value P and the subpeak value W of the autocorrelation waveform, and the ratio P/C between the peak value P of the autocorrelation waveform and the maximum peak value C of the cross correlation waveform are both large. The present invention comprises phase control means of a structure in which an SSFBG 40 having fifteen unit FBGs arranged in series in the waveguide direction is fixed to the core of the optical fiber 36 that comprises the core 34 and cladding 32. The difference ?n between the maximum and minimum of the effective refractive index of the optical fiber is 6.2×10?5. The phase difference of Bragg reflected light from two unit diffraction gratings that adjoin one another from front to back and provide equal code values is given by 2?M+(?/2) where M is an integer.

Abstract: A wavelength tuning device of the invention tunes the reflected wavelength of a fiber Bragg grating, and includes: an optical fiber (102) in which a fiber Bragg grating (106) is formed; a base member (104) to which the optical fiber (102 is fixed; a first temperature sensor (112) that detects a temperature of the base member (104); a thermo-module (116) that adjust the temperature of the base member (104) such that the temperature detected by the first temperature sensor (112) is maintained at a desired temperature; a second temperature sensor (126) that detects an external temperature of the wavelength tuning device; and a temperature controller (130) that controls the thermo-module (116) such that the temperature of the base member (104) is maintained at the desired temperature based on the external temperature detected by the second temperature sensor (126).

Abstract: A wavelength tuning device of the invention tunes the reflected wavelength of a fiber Bragg grating, and includes: an optical fiber (102) in which a fiber Bragg grating (106) is formed; a base member (104) to which the optical fiber (102 is fixed; a first temperature sensor (112) that detects a temperature of the base member (104); a thermo-module (116) that adjust the temperature of the base member (104) such that the temperature detected by the first temperature sensor (112) is maintained at a desired temperature; a second temperature sensor (126) that detects an external temperature of the wavelength tuning device; and a temperature controller (130) that controls the thermo-module (116) such that the temperature of the base member (104) is maintained at the desired temperature based on the external temperature detected by the second temperature sensor (126).

Abstract: The present invention is an SSFBG with which there are few restrictions on the code that can be set and the overall length of which is short. This SSFBG has four unit FBGs the Bragg reflection wavelengths of which are ?1, ?2, ?3, and ?4 disposed with a part where the unit FBGs overlap one another in the waveguide direction of the optical fiber. The left end of the horizontal axis corresponds to the position of the I/O terminal of the SSFBG and the right end of the horizontal axis corresponds to the terminal on the opposite side from the I/O terminal of the SSFBG. The Bragg reflection wavelengths ?1, ?2, ?3, and ?4 of the four unit FBGs are ?1=1543.28 nm, ?2=1543.60 nm, ?3=1543.92 nm, and ?4=1544.24 nm respectively. Codes (?1, ?2, ?3, and ?4) used in the time-spreading/wavelength hopping system are established for the SSFBG by disposing the four unit FBGs at equal intervals such that the interval therebetween is 12.8 mm.

Abstract: A method for fabricating fiber Bragg gratings including: scanning a photosensitive optical fiber with ultraviolet laser light in a longitudinal direction of the optical fiber by means of a phase mask method, thereby forming periodic refractive index modulation structure in a core of the optical fiber in the longitudinal direction; and instantaneously moving a phase mask used in the phase mask method by a predetermined distance in the longitudinal direction, thereby forming a phase shift portion in the periodic refractive index modulation structure formed in the core of the optical fiber, when a radiation position of the ultraviolet laser light reaches a predetermined position, in the middle of the scanning step using the ultraviolet laser light.

Abstract: An FBG encoder as an optical waveguide device includes plural unit FBGs respectively including a periodic refractive index modulation structure in a longitudinal direction of an optical fiber and aligned in the longitudinal direction of the optical fiber; and a phase shift section formed between any two adjacent unit FBGs among the plural unit FBGs, thereby producing a predetermined phase difference between the periodic refractive index modulation structures of two adjacent unit FBGs, wherein the unit FBGs respectively have a structure wherein a period of the periodic refractive index modulation of the plural unit diffraction grating sections gradually increases or decreases in the longitudinal direction of the optical fiber or a structure wherein amplitude of the periodic refractive index modulation is varied relative to the longitudinal direction of the optical fiber so that an envelope of the periodic refractive index modulation is a predetermined window function.

Abstract: The present invention is an optical pulse time spreading device comprising a plurality of optical pulse time spreaders that output an input optical pulse as a series of chip pulses stream that are sequentially arranged time-spread on a time axis in accordance with optical phase code. Each of the optical pulse time spreaders comprises phase control means that supplies a phase difference between adjacent chip pulses. Identification parameters are introduced to realize channel discrimination by changing the phase difference conditions supplied between adjacent chip pulses for each of the phase control means. The phase control means have a structure in which an SSFBG is fixed to the core of the optical fiber, for example. The SSFBG has unit FBGs that are arranged in series in the waveguide direction of the core. The code values of the optical phase code established for the phase control means correspond each one-on-one with each of the unit FBGs.

Abstract: In coupling a control station transmitting a radio signal to a plurality of base stations each transmitting the radio signal to a terminal station by an optical fiber, and dependently connecting the plurality of base stations to the optical fiber, the control station includes a radio signal transmitter and an electrical-to-optical converter. Each of the base stations including an SOA-EAM comprises a semiconductor optical amplifier (SOA) and an electro-absorption modulator (EAM), a down link radio signal amplifier, and a down link antenna, the SOA-EAM receiving an optical signal from the control station. The optical transmission system can prevent optical power from lowering even if the number of base stations increases and can facilitate adding a base station since an optical coupler is not used.

Abstract: A method for manufacturing a single stone into a regular dodecahedral ornament or a regular icosahedral ornament, and the ornament manufactured according to the method are provided. The method enables the ornament to be manufactured at low costs with ease without using a complicated, numerically computer-controlled shaping machine. The geometric features determining the faces and ridges of a regular dodecahedron or a regular icosahedron are drawn as cutting base lines on each surface of a cubic workpiece. On a face formed by cutting based on the cutting base lines, new auxiliary cutting lines are sequentially drawn by marking. Then, based on these auxiliary cutting lines and the remaining cutting base lines, a possible cut face is determined, which is in turn cut using a cutting tool. The cutting base lines which are erased after each cutting are complemented by auxiliary cutting lines to find a new possible cut face, which is in turn cut in sequence, thereby manufacturing the regular polyhedral ornament.

Abstract: An optical code division multiplexing communication method includes the steps of: producing a multi-wavelength optical pulse train from wavelength multiplexing pulse; transmitting the multi-wavelength optical pulse train through a transmission line using a time-spreading/wavelength-hopping method; decoding wavelength multiplexing pulse from the multi-wavelength optical pulse train transmitted through the transmission line; compensating delay time differences between individual optical pulses of the multi-wavelength optical pulse train, the delay time differences occurring in the step of transmitting the multi-wavelength optical pulse train through the transmission line; and compensating optical pulse spread in a time direction, which occurs in each of the optical pulses of the multi-wavelength optical pulse train in the step of transmitting the multi-wavelength optical pulse train through the transmission line.

Abstract: An FBG encoder as an optical waveguide device includes plural unit FBGs respectively including a periodic refractive index modulation structure in a longitudinal direction of an optical fiber and aligned in the longitudinal direction of the optical fiber; and a phase shift section formed between any two adjacent unit FBGs among the plural unit FBGs, thereby producing a predetermined phase difference between the periodic refractive index modulation structures of two adjacent unit FBGs, wherein the unit FBGs respectively have a structure wherein a period of the periodic refractive index modulation of the plural unit diffraction grating sections gradually increases or decreases in the longitudinal direction of the optical fiber or a structure wherein amplitude of the periodic refractive index modulation is varied relative to the longitudinal direction of the optical fiber so that an envelope of the periodic refractive index modulation is a predetermined window function.

Abstract: A method for fabricating fiber Bragg gratings including: scanning a photosensitive optical fiber with ultraviolet laser light in a longitudinal direction of the optical fiber by means of a phase mask method, thereby forming periodic refractive index modulation structure in a core of the optical fiber in the longitudinal direction; and instantaneously moving a phase mask used in the phase mask method by a predetermined distance in the longitudinal direction, thereby forming a phase shift portion in the periodic refractive index modulation structure formed in the core of the optical fiber, when a radiation position of the ultraviolet laser light reaches a predetermined position, in the middle of the scanning step using the ultraviolet laser light.