Abstract: A phase control arrangement has a structure in which a Superstructured fiber Bragg Grating (SSFBG) 40 has fifteen unit Fiber Bragg Gratings (FBGs) arranged in series in a waveguide direction. The SSFBG 40 is fixed to the core of an optical fiber 36 that includes a 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. Further, the phase difference of the Bragg reflected light from two unit diffraction gratings that adjoin one another from front to back and provide different code values is given by 2?M+(2N+1)?+(?/2) where M and N are integers.

Abstract: An object of the present invention is to provide an OCDM transceiver with which the reduction amount of the intensity of the correlation waveform signal is smaller than that of a conventional device of the same type in the decoding step that comprises a time gate processing step. Hence, in the OCDM transceiver of the present invention that comprises an encoding portion and a decoding portion, the decoding portion is constituted comprising a decoder, clock extractor, and time gate. The decoder decodes an encoded optical pulse signal and separates the encoded optical pulse signal into a clock signal extraction signal and an optical pulse signal playback signal. The clock extractor extracts a clock signal from the clock signal extraction signal. Further, the time gate removes only the auto-correlation waveform component from the optical pulse signal playback signal. The auto-correlation waveform component is converted to an electrical signal by means of an optical receiver and generated as a reception signal.

Abstract: An object of the present invention is to provide an OCDM transceiver with which the reduction amount of the intensity of the correlation waveform signal is smaller than that of a conventional device of the same type in the decoding step that comprises a time gate processing step. Hence, in the OCDM transceiver of the present invention that comprises an encoding portion and a decoding portion, the decoding portion is constituted comprising a decoder, clock extractor, and time gate. The decoder decodes an encoded optical pulse signal and separates the encoded optical pulse signal into a clock signal extraction signal and an optical pulse signal playback signal. The clock extractor extracts a clock signal from the clock signal extraction signal. Further, the time gate removes only the auto-correlation waveform component from the optical pulse signal playback signal. The auto-correlation waveform component is converted to an electrical signal by means of an optical receiver and generated as a reception signal.

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 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: 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 time-spreading and wavelength-hopping optical encoder spreads each pulse in a modulated optical pulse signal into a predetermined pulse train including pulses with different wavelengths. The last pulse in the pulse train is delayed from the first pulse in the pulse train by an interval that is longer than the pulse period of the modulated optical pulse signal. Interference is avoided by dividing the pulse train into successive delay groups that are equal in length to the pulse period of the modulated data pulse signal, and having each wavelength appear in only one delay group. If encoders producing differently structured pulse trains are used in an optical multiplexer, interference is avoided by having the same wavelength appear only at different positions within the delay groups of different pulse trains. Long delays can be used to multiplex a relatively large number of channels, even at high transmission rates.

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 signal encoder/decoder includes a grating waveguide having an identical number of uniform pitch gratings to the number of code chips of a binary phase optical code, the uniform pitch gratings being formed in a waveguide direction to reflect light of a predetermined wavelength. Here, adjacent gratings corresponding to a position at which the optical code value changes are disposed a spacing apart from each other to give a phase shift of (2m+1)?/2 to the light, and the remaining adjacent gratings are disposed a spacing apart from each other to give a phase shift of n? to the light (m, n: integer).

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: 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: An object of the present invention is to provide an OCDM transceiver with which the reduction amount of the intensity of the correlation waveform signal is smaller than that of a conventional device of the same type in the decoding step that comprises a time gate processing step. Hence, in the OCDM transceiver of the present invention that comprises an encoding portion and a decoding portion, the decoding portion is constituted comprising a decoder, clock extractor, and time gate. The decoder decodes an encoded optical pulse signal and separates the encoded optical pulse signal into a clock signal extraction signal and an optical pulse signal playback signal. The clock extractor extracts a clock signal from the clock signal extraction signal. Further, the time gate removes only the auto-correlation waveform component from the optical pulse signal playback signal. The auto-correlation waveform component is converted to an electrical signal by means of an optical receiver and generated as a reception signal.

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: A method for generating an optical pulse train includes generating a source optical pulse train having a predetermined pulse period; optically combining a plurality of uniform pitch grating waveguides having a substantially identical Bragg wavelength and ?/4-phase-shift waveguides in an alternating sequence so as to form a multiple ?/4-phase-shift grating waveguide; inputting the source optical pulse train from one end of the multiple ?/4-phase-shifted grating waveguide; and extracting reflected optical pulses by the plurality of uniform pitch grating waveguides from the one end of the multiple ?/4-phase-shifted grating waveguide.

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 optical signal encoder/decoder includes a grating waveguide having an identical number of uniform pitch gratings to the number of code chips of a binary phase optical code, the uniform pitch gratings being formed in a waveguide direction to reflect light of a predetermined wavelength. Here, adjacent gratings corresponding to a position at which the optical code value changes are disposed a spacing apart from each other to give a phase shift of (2m+1)?/2 to the light, and the remaining adjacent gratings are disposed a spacing apart from each other to give a phase shift of n? to the light (m, n: integer).

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 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: An optical filter comprising a first CBG including a first end and a second end, a second CBG of the same structure as the first CBG, including a third end of the same structure as the first end and a fourth end of the same structure as the second end, and a circuit including an input port and an output port. The circuit receives a first optical signal via the input port and brings it to the first end of the first CBG, the circuit receives a second optical signal produced by reflecting the first optical signal from the first CBG and brings the second optical signal to the fourth end of the second CBG, and the circuit receives a third optical signal produced by reflecting the second optical signal from the second CBG and outputs the third optical signal via the output port.