Abstract: In an optical network unit, an optical-intensity monitor monitors the received optical intensity of a received light beam input thereto, and a controller uses the received optical intensity to produce an intensity control signal, in response to which a semiconductor optical amplifier selectively amplifies or attenuates the optical intensity of the received light to produce an intensity-adjusted light beam, which a receiver can receive within its receivable-intensity range.

Abstract: An optical pulse time spreading apparatus wherein an optical splitter divides an input optical pulse into first to U-th input optical pulses; first to U-th optical pulse time spreaders respectively have the first to U-th input optical pulses input thereto and output first to U-th chip pulse sequences each consisting of N chip pulses from a first to an N-th chip pulse arranged in order on a time axis into which the input optical pulse is time-spread; and an interval between adjacent ones of unit FBGs arranged in a p-th optical pulse time spreader and a Bragg reflection wavelength of the unit FBGs in the p-th optical pulse time spreader are set such that spectra of the first to U-th chip pulse sequences are different from each other.

Abstract: An optical code division multiplexing signal generator provided with an optical pulse light source, a first encoder to an Nth encoder, a first optical modulator to an Nth optical modulator, and a first optical circulator to an Nth optical circulator. The first optical circulator inputs an input optical pulse train to a first encoder, and inputs a first encoded optical pulse train output by Bragg reflection from the first encoder to the first optical modulator. The kth optical circulator inputs an input (k?1)th optical pulse train which has passed through the (k?1)th encoder to a kth encoder, and inputs a kth encoded optical pulse train output by Bragg reflection from the kth encoder to the kth optical modulator. Herein k takes all integers from 2 to N, and N is a positive integer of 2 or more.

Abstract: An optical pulse time spreading apparatus wherein an optical splitter divides an input optical pulse into first to U-th input optical pulses; first to U-th optical pulse time spreaders respectively have the first to U-th input optical pulses input thereto and output first to U-th chip pulse sequences each consisting of N chip pulses from a first to an N-th chip pulse arranged in order on a time axis into which the input optical pulse is time-spread; and an interval between adjacent ones of unit FBGs arranged in a p-th optical pulse time spreader and a Bragg reflection wavelength of the unit FBGs in the p-th optical pulse time spreader are set such that spectra of the first to U-th chip pulse sequences are different from each other.

Abstract: An optical code division multiplexing signal generator provided with an optical pulse light source, a first encoder to an Nth encoder, a first optical modulator to an Nth optical modulator, and a first optical circulator to an Nth optical circulator. The first optical circulator inputs an input optical pulse train to a first encoder, and inputs a first encoded optical pulse train output by Bragg reflection from the first encoder to the first optical modulator. The kth optical circulator inputs an input (k?1)th optical pulse train which has passed through the (k?1)th encoder to a kth encoder, and inputs a kth encoded optical pulse train output by Bragg reflection from the kth encoder to the kth optical modulator. Herein k takes all integers from 2 to N, and N is a positive integer of 2 or more.

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: An optical pulse time spreading device includes an optical fiber and a superstructured fiber Bragg grating (SSFBG) formed in the optical fiber. The SSFBG includes unit fiber Bragg gratings (FBGs) having the effective refractive index of the optical fiber periodically varying in the longitudinal direction of the fiber, and phase shifters having a constant effective refractive index. Each unit FBG is arranged between the adjacent phase shifters in the longitudinal direction. The unit FBG having its unit grating length in the longitudinal direction shorter than the unit segment length which is the distance between the unit FBGs next to each other. The optical pulse time spreading device provides the peak intensity of the autocorrelation wave less dependent on a code used for encoding and decoding.

Abstract: An optical communication system uses superstructured fiber Bragg gratings (SSFBGs) to encode and decode an optical pulse signal transmitted between two optical communication devices. Each SSFBG has uniformly spaced fiber Bragg gratings, producing a chip pulse train with a uniform phase difference between chips. The phase difference defines a code. There is one SSFBG at one of the two devices and two or more SSFBGs at the other device, using different codes to encode or decode the same optical signal. Using one code to encode and multiple codes to decode, or multiple codes to encode and one code to decode, provides a high signal-to-noise ratio and permits stable performance despite environmental temperature variations. For bidirectional communication, each communication device has at least three SSFBGs, divided into a transmitting group and a receiving group, mounted on a mounting plate with a negative thermal expansion coefficient.

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 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: An object of the present invention is to adjust the operating wavelength of a decoder, in order to coordinate the operating characteristics of an encoder and the decoder. To this end, an optical code division multiplex transmission device of the present invention comprises a second SSFBG in the decoder, and has a mechanism to perform adjustment (phase adjustment step) of the fixation portion interval L which is the interval between a first and second fixation portions fixing in place the second SSFBG, such that the extent of the eye opening of optical pulses output from the second SSFBG is maximum. The extent of the eye opening is measured using a correlation waveform monitor, and the measurement data is sent to the wavelength control portion. A signal is sent from the wavelength control portion to the movement control portion to set the fixation portion interval L, based on data relating to the extent of the eye opening sent from the correlation waveform monitor.

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: 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: There is provided a fiber Bragg grating devise comprising an FBG mount that is constituted by sequentially stacking a temperature control plate, a base plate, and a mounting plate, and an SSFBG in which a plurality of FBG units of the same constitution and a plurality of phase modulation portions are alternately formed in the same optical fiber. The temperature control plate is constituted by a thermo module and a heat-insulating member. The base plate is fixed in contact with the upper face of the temperature control plate and the mounting plate is in contact with the upper face of the base plate in a state where the mounting plate is able to glide over the upper face of the base plate. The SSFBG is fixed to contact an FBG contact portion that is established on the upper face of the mounting plate.

Abstract: There is provided a fiber Bragg grating devise comprising an FBG mount that is constituted by sequentially stacking a temperature control plate, a base plate, and a mounting plate, and an SSFBG in which a plurality of FBG units of the same constitution and a plurality of phase modulation portions are alternately formed in the same optical fiber. The temperature control plate is constituted by a thermo module and a heat-insulating member. The base plate is fixed in contact with the upper face of the temperature control plate and the mounting plate is in contact with the upper face of the base plate in a state where the mounting plate is able to glide over the upper face of the base plate. The SSFBG is fixed to contact an FBG contact portion that is established on the upper face of the mounting plate.