Abstract: As is described above, an optical wavelength division multiplexing and transmission apparatus according to the present invention has the configuration in which a plurality of slave racks coupling to a master rack can be additionally installed one after another with the master rack. Therefore, in cases where it is desired to expand a function of a transmitter and a function of a receiver due to the increase of a quality of information to be transmitted, the additional installation of the slave rack can be performed without exerting influence on a communication means installed in advance and currently used. Accordingly, it can be expected that the optical wavelength division multiplexing and transmission apparatus is adapted for the optical communication service which is more and more increased in the future.

Abstract: A communication apparatus includes a transmitter and a receiver, wherein the transmitter further includes: an interleaver that rearranges positions of bits of an information frame; an FEC encoder that performs an error correction encoding to the information frame whose bit positions have been rearranged; and a selector that inserts FEC parity into predetermined positions of the information frame, to thereby generate a transmission signal, whereas the receiver includes: a selector that extracts an information frame part and an FEC parity part from a reception signal; an interleaver that rearranges positions of the bits of the information frame part using the same rule as that used at that transmitter side; an FEC decoder that corrects an error of bits rearranged based on the error correction parity part; and a de-interleaver that reproduces an information frame by returning positions of error-corrected bits to original bit positions.

Abstract: An optical repeating system includes an optical transmitter and a plurality of optical amplifying repeaters. The optical transmitter specifies a part or all of the optical amplifying repeaters, and transmits a supervisory command to the specified optical amplifying repeaters as a first sub-signal via an uplink or downlink optical transmission line. The supervisory command is a command to supervise internal circuits of the optical amplifying repeaters. Receiving the supervisory command addressed thereto via the uplink or downlink optical transmission line, the optical amplifying repeaters each transmit a supervisory signal indicating a supervisory result corresponding to the supervisory command to optical receivers via the uplink and downlink optical transmission lines as a second sub-signal. The optical system can reduce the time take to acquire the supervisory information about the plurality of the optical amplifying repeaters.

Abstract: A differential encoder generates a differentially encoded signal based on a data signal. An RZ (return to zero) encoder generates an electric RZ differential signal as an RZ signal in an electric area based on the differentially encoded signal. A Mach-Zehnder interferometer type intensity modulator generates an optical RZ-DSPK (differential phase shift keying) signal as an RZ signal in an optical area based on the electric RZ differential signal.

Abstract: An optical repeating system includes an optical transmitter and an optical amplifying repeater. The optical transmitter transmits a supervisory command and a control command to the optical amplifying repeater as a first sub-signal. The supervisory command is a command to supervise internal circuits of the optical amplifying repeater, and the control command is a command to control the optical amplifying repeater. The optical amplifying repeater includes multiple sub-modules each for amplifying and repeating main signals on multiple sets of optical transmission lines. When receiving the supervisory command via the optical transmission line, each sub-module transmits a supervisory signal indicating the supervisory result associated with the supervisory command to an optical receiver as a second sub-signal.

Abstract: Binary information is subjected to RZ encoding and multi-level encoding, and the encoded signal is optically modulated.

Abstract: An optical fiber propagates and amplifies a second signal light that is a wavelength-multiplexed signal of a first signal light of a plurality of wavelengths and a reference light that is out of a wavelength range of amplification. An excitation light source outputs an excitation light for amplifying the second signal light. A beam splitter splits a portion of the second signal light into the first signal light and the reference light. A signal light level detecting unit detects a level of the first signal light. A reference light level detecting unit detects a level of the reference light. A signal level setting unit calculates a target value for constantly maintaining a Raman gain, and controls the output level of the excitation light in such a way that the first signal level matches with the target value.

Abstract: An optical repeater is provided between a first optical fiber transmission path and a second optical fiber transmission path having a zero-dispersion wavelength different from the first optical fiber transmission path. This optical repeater wave-converts a wavelength division multiplex signal input from the first optical fiber transmission path with respect to respective wavelengths thereof, and outputs the wave-converted signal to the second optical fiber transmission path.

Abstract: In a one-fiber bidirectional optical transmission system in which output optical signals of optical transmitter-receivers respectively connected to the opposite ends of one optical fiber transmission line are bidirectionally transmitted in the optical fiber transmission line, which utilizes a Raman amplification effect by backward pumping, a frequency satisfying the conditions of |fs1?f0|?|fp2?f0| and |fs2?f0|?|fp1?f0| is selected, where f0 is a zero dispersion frequency of the optical fiber transmission line, fs1 and fs2 are the frequencies of the first signal and the second signal, respectively, and fp1 and fp2 are frequencies of the first Raman pump light and the second Raman pump light, respectively.

Abstract: In an optical repeating system including an optical transmitter and optical amplifying repeaters, the optical transmitter specifies one optical amplifying repeater, and transmits to the optical amplifying repeater a supervisory command to supervise internal circuits of the optical amplifying repeater and a control command to control amplification factors of optical amplifiers of the optical amplifying repeater as a first sub-signal. Receiving the supervisory command via an optical transmission line, the optical amplifying repeater transmits a supervisory signal indicating a supervisory result corresponding to the supervisory command to optical receivers via optical transmission lines as a second sub-signal. Receiving the control command via the optical transmission line, the optical amplifying repeater is controlled to change amplification factors of the optical amplifiers in response to the control command.

Abstract: The present invention includes an optical band-limiting filter which imposes a band-limitation on an input optical signal, an opto-electric converter which converts the optical signal output from the optical band-limiting filter into an electric signal, a lowpass filter which imposes the band-limitation on the electric signal output from the opto-electric converter, an amplifier which amplifies the output signal of the lowpass filter, and an electric equalizer which performs an equalization processing on a waveform of the electric signal output from the opto-electric converter are provided, and a full width at half maximum of the optical band-limiting filter is set to be equivalent to or smaller than a bit rate frequency of the optical signal.

Abstract: An optical fiber propagates and amplifies a second signal light that is a wavelength-multiplexed signal of a first signal light of a plurality of wavelengths and a reference light that is out of a wavelength range of amplification. An excitation light source outputs an excitation light for amplifying the second signal light. A beam splitter splits a portion of the second signal light into the first signal light and the reference light. A signal light level detecting unit detects a level of the first signal light. A reference light level detecting unit detects a level of the reference light. A signal level setting unit calculates a target value for constantly maintaining a Raman gain, and controls the output level of the excitation light in such a way that the first signal level matches with the target value.

Abstract: An optical signal switching unit causing no instantaneous cutoff in switching without a latency time. The optical signal switching unit has input waveguides and output waveguides, optical switches for switching the course of each optical signal, located at intersections between the waveguides and outputting the optical signal to the output waveguides. This optical signal switching unit includes optical switches and a switch state control part controlling the states of the optical switches, thereby controlling formation of the output optical signal. The optical switches take binary states including a first route state providing the optical signal with a first course and a second course state providing the optical signal with a second course, and an intermediate state including part of both of the first and second course states.

Abstract: A supervisory system and supervisory method of an optical amplifier repeater are proposed that can implement operation supervision taking account of the characteristics of individual supervisory targets of the optical amplifier repeater, thereby achieving higher reliability.

Abstract: The present invention has an object to obtain an optical signal quality supervisory device that supervises the quality of an optical signal simply, efficiently and with high accuracy without inviting an increase in cost, an increase in circuit scale and increase in power consumption. The bit rate of the optical supervisory channel is made lower than the bit rate of the optical main channel that is transmitted over an optical communication system, but the reception electric band width of a receiver that receives the optical supervisory channel is made equal to or wider than the reception electric band width of a receiver that receives the optical main channel. Also, the optical supervisory channel is made up of an SOH (section over head) frame to detect an error of the BIP (bit interleaved parity) byte of SOH, thereby supervising the quality of the optical communication system, in particular, the light wave network.

Abstract: In a one-fiber bidirectional optical transmission system in which output optical signals of optical transmitter-receivers respectively connected to the opposite ends of one optical fiber transmission line are bidirectionally transmitted in the optical fiber transmission line, which utilizes a Raman amplification effect by backward pumping, a frequency satisfying the conditions of |fs1−f0|≠|fp2−f0| and |fs2−f0|≠|fp1−f0| is selected, where f0 is a zero dispersion frequency of the optical fiber transmission line, fs1 and fs2 are the frequencies of the first signal and the second signal, respectively, and fp1 and fp2 are frequencies of the first Raman pump light and the second Raman pump light, respectively.

Abstract: An optical receiver includes a soft-decision deciding means (7) for deciding an electric received signal according to a plurality of decision levels so as to output a multivalued decision signal, a demultiplexing means (5) for serial-to-parallel converting the multivalued decision signal so as to output a multivalued parallel signal, a soft-decision error correction decoding means (8) for making an error correction to the multivalued parallel signal based on reliability information so as to output an error-corrected parallel received signal and decision results indicating the decision of the electric received signal according to the plurality of decision levels, a probability density distribution estimation means (9) for estimating probability density distributions based on distributions of the decision results indicating the decision of the electric received signal according to the plurality of decision levels, and a decision level control means (10) for controlling the plurality of decision levels in the so

Abstract: If no alarm information is input from an optical receiver (12), an FEC decoder (13), or a client signal monitor (14), a control circuit (15) controls a variable dispersion equalizer (11) such that a transmission error becomes smaller using information on the number of error corrections obtained from the FEC decoder (13) and fixes a dispersion equalization value in the event that the error becomes equal to or lower than a specified value. If the alarm information is input, the control circuit (15) switches control over the variable dispersion equalizer (11) from an ordinary control to a search mode control for searching an optimal dispersion equalization value in a wide range to thereby search the optimal dispersion equalization value at a higher speed.

Abstract: An optical modulation processing section is provided which, in turn, includes a signal carrier-suppressed pulse modulating unit that performs signal carrier-suppressed pulse modulation on a light source signal to thereby create a CS-RZ signal, a phase modulating unit that performs phase modulation on a data signal based on the CS-RZ signal to thereby convert the data signal to a phase-modulated signal, and an optical filtering unit that filters out redundant frequency components included in the phase modulation signal.

Abstract: An optical signal switching unit causing no instantaneous cutoff in switching without providing a latency time is obtained. The optical signal switching unit has a plurality of input waveguides and a plurality of output waveguides for switching the course of each optical signal on intersections between the waveguides and outputting the optical signal to the output waveguides. This optical signal switching unit comprises a plurality of optical switches and a switch state control part controlling the states of the plurality of optical switches thereby controlling formation of the output optical signal, while the optical switches take binary states including a first route state providing the optical signal with a course and a second course state providing the optical signal with another course as well as an intermediate state partially including both of the binary states.