Abstract: In a downstream channel communication, an individual downstream channel wavelength is allocated to each group of user nodes, and for user nodes in a same group, a central office performs a downstream-signal communication by a same communication method using the individual downstream channel wavelength. In an upstream channel communication, all user nodes perform an upstream-signal communication with the central office using a single upstream channel. A downstream signal from the central office is distributed to the groups for each individual downstream channel wavelength, and upstream signals from the user nodes are transmitted to the central office in a multiplexing manner.

Abstract: The invention is applied to a PON system including an optical line terminal (OLT) at a center station, a plurality of optical network units (ONUs) at subscribers' sites, and an optical transmission line shared by the plurality ONUs to optically connect between the OLT and the plurality of ONUs. Each of the ONUs requests the OLT to assign a logical link according to start-up of an application.

Abstract: To inform a location of a caller to the other party in an IP phone system, a wireless IC tag preserving unique ID information is attached to an optical connector of a user connection port. The relations between locations of the optical connectors and ID information of corresponding wireless IC tags are stored in a port control database. An IC tag reader in an optical network unit (ONU) reads the ID information in the wireless IC tag attached to the optical connector to which the ONU is connected. When an emergency call is initialed, the ONU transmits destination information of the emergency call and the ID information of the wireless IC tag to a central station. A control terminal in the central station compares the ID information of the wireless IC tag against the port control database to determine a location of the optical connector. The central station adds the determined location information to the destination information of the emergency call and transmits the information to an IP network.

Abstract: To inform a location of a caller to the other party in an IP phone system, a wireless IC tag preserving unique ID information is attached to an optical connector of a user connection port. The relations between locations of the optical connectors and ID information of corresponding wireless IC tags are stored in a port control database. An IC tag reader in an optical network unit (ONU) reads the ID information in the wireless IC tag attached to the optical connector to which the ONU is connected. When an emergency call is initiated, the ONU transmits destination information of the emergency call and the ID information of the wireless IC tag to a central station. A control terminal in the central station compares the ID information of the wireless IC tag against the port control database to determine a location of the optical connector. The central station adds the determined location information to the destination information of the emergency call and transmits the information to an IP network.

Abstract: The invention is applied to a PON system including an optical line terminal (OLT) at a center station, a plurality of optical network units (ONUs) at subscribers' sites, and an optical transmission line shared by the plurality ONUs to optically connect between the OLT and the plurality of ONUs. Each of the ONUs requests the OLT to assign a logical link according to start-up of an application.

Abstract: To inform a location of a caller to the other party in an IP phone system, a wireless IC tag preserving unique ID information is attached to an optical connector of a user connection port. The relations between locations of the optical connectors and ID information of corresponding wireless IC tags are stored in a port control database. An IC tag reader in an optical network unit (ONU) reads the ID information in the wireless IC tag attached to the optical connector to which the ONU is connected. When an emergency call is initialed, the ONU transmits destination information of the emergency call and the ID information of the wireless IC tag to a central station. A control terminal in the central station compares the ID information of the wireless IC tag against the port control database to determine a location of the optical connector. The central station adds the determined location information to the destination information of the emergency call and transmits the information to an IP network.

Abstract: According to one embodiment of the invention, a control method of an xDSL modem to transmit/receive signals to/from an outer xDSL modem through an analog transmission line such as a telephone line is provided. A line quality of the analog transmission line is measured by training. A line profile is determined as a current profile of the analog transmission line according to the results from the training. A link is established with the determined current profile. Disconnected link is recovered with a standby profile.

Abstract: The optical amplifier according to the present invention is constructed such that the amount of the electric current fed to the power feeding line 2a is first detected by the current detection means, and then a setting signal is generated to each of the bypass circuits 22 and 23 in accordance with the thus detected amount of the fed current, and thereafter the output level of each of the optical repeater circuits 11 and 12 is controlled respectively by the bypass circuits 22 and 23, so that the output level of these repeater circuits 11 and 12 can be controlled in accordance with the amount of the current fed to the power feeding line 2a.

Abstract: An optical TDM multiplexing apparatus to multiplex a plurality of input signals in the optical stage in the time domain according to the invention comprise a plurality of signal light sources to generate optical signals each having a wavelength different from the others to carry each of the plurality of the input signals, a timing adjuster to adjust timings between the respective optical signals so that each optical signal output from the plurality of the signal light sources is disposed on a time slot different from the others in the time domain, an optical multiplexer to multiplex each optical signal output from the timing adjuster in the wavelength domain and a wavelength converter to convert each wavelength of the output light from the optical multiplexer into a predetermined wavelength.

Abstract: An optical transmitter outputs WDM signal lights comprising signal lights with 100 wavelengths of 10 Gbit/s, onto an optical transmission fiber. In the optical transmission line, a transmission fiber and a local area dispersion compensation fiber are disposed per repeater span defined by an optical amplification repeater, the local area dispersion compensation fiber is for compensating the average chromatic dispersion in the repeater span to become 2 ps/nm/km as well as a dispersion slope to become zero, and a wide area dispersion compensation fiber for compensating the average chromatic dispersion to become −0.2 ps/nm/km as well as the dispersion slope to become zero is disposed per predetermined number of optical repeater spans. The optical transmission fiber comprises a single mode optical fiber with large core diameter having a zero dispersion wavelength at a 1.3 &mgr;m band and plus chromatic dispersion at a signal wavelength band (a 1.55 &mgr;m band).

Abstract: An optical fiber transmission line for realizing satisfactory long haul transmission characteristics using two kinds of optical fibers. The optical fiber transmission line includes a plurality of local dispersion compensating spans, wide dispersion compensating spans disposed at predetermined intervals, and optical repeating amplifiers to connect each span. The local dispersion compensating span includes a first optical fiber with positive dispersion having an effective core area of 130 &mgr;m2 or more and a second optical fiber with a negative dispersion value of −50 ps/nm/km or less to transmit the light output from the first optical fiber. The wide dispersion compensating span consists of a third optical fiber having the same configuration and composition with the first optical fiber.

Abstract: An optical fiber (12a) with a large effective core area and a large chromatic dispersion value is disposed on an input side of signal light, and an optical fiber (12b) with a small effective core area and a small chromatic dispersion value or a chromatic dispersion value of negative polarity is disposed on an output side of the signal light. A pumping light source (14) generates pumping light of 1450 nm to cause Raman amplification of 1550 nm in the optical fiber (12b). The output light from the pumping light source (14) enters the optical fiber (12b) from the back through a WDM optical coupler (16). Provided that y=(Pin−&agr;)/(Pp·10 Log L) where input power of the optical fiber (12a) (i.e.

Abstract: An object of the present invention is to realize almost the same transmission characteristic in all wavelengths at a transmission rate of 10 Gb/s or more. An optical transmitter 10 outputs WDM signal light multiplexed with signal light of a plurality of wavelengths toward an optical transmission line 12. The optical transmission line 12 comprises an optical transmission fiber 14, an optical repeating amplifier 16 and a dispersion compensating fiber 18. The gain characteristic of the optical repeating amplifier 16 is set so that the gain becomes the maximum at the effective zero dispersion wavelength of the optical transmission line 12 and that lowers inversely proportional to the distance from the effective zero dispersion wavelength. The whole optical transmission line 12 is set so that the peak power deviation between the effective zero dispersion wavelength &lgr;0 and the wavelength &lgr;1 or &lgr;n on both end becomes approximately 4 dB.

Abstract: An object of this invention is to improve transmission characteristics in WDM transmission. An optical transmitter (10) wavelength-multiplexes signal lights of wavelengths &lgr;1 through &lgr;n and outputs them onto an optical transmission line (12). Optical powers of the signal lights of the respective wavelength &lgr;1 through &lgr;n are identical or become smaller proportional to the wavelength. One repeater span of the optical transmission line (12) is composed of an optical fibers (20, 22) and an optical amplifier (24), and a gain equalizer (26) is dispersed every several repeater spans. The optical amplifier (24) in the repeater span amplifies each signal light so that optical power of a signal on the shorter wavelength side becomes smaller than that of a signal on the longer wavelength side. The gain equalizer (26) equalizes optical powers of the respective signal lights.

Abstract: An object of the present invention is to prevent an increase of the degree of polarization of an output pumping light even if one of pumping light sources has a failure. Laser diodes (30a, 30b) are composed of FP-LDs made of InGaAsP to laser-oscillate at 1480 nm band. The outputs from the laser diodes (30a, 30b) enter a polarizing beam splitter (32) in orthogonal state of polarization and are combined there. The combined light by the polarizing beam splitter (32) enters a depolarizing element (34) and is depolarized there.

Abstract: To improve transmission characteristics of a CS-RZ signal, a laser diode (LD) (12) outputs a continuous light (CW light) having a wavelength &lgr;s (frequency f0). A CS-RZ pulse train shaper (14) generates a CS-RZ optical pulse train at a bit rate (B) from the CW output light from the LD (12). A data modulator (16) intensity-modulates an output optical pulse train from the shaper (14) according to a data (D) to be transmitted. An optical bandpass filter (18) passes through all of a component of carrier frequency (f0) and a component of frequency f1 (=f0+B/2) and transmits a small amount of component of frequency f2 (=f0−B/2).

Abstract: A system for monitoring a distributed Raman optical transmission line to optically amplify a signal light having a signal wavelength by pumping with a Raman pumping light having a Raman pumping wavelength comprises an optical demultiplexer to demultiplex an output light from the distributed Raman optical transmission line into the signal wavelength component and the Raman pumping wavelength, an optical power measuring unit to measure the optical powers of the signal wavelength component and the Raman wavelength component demultiplexed by the optical demultiplexer, and a judging unit to judge whether a fault exists in the Raman amplification in the distributed Raman optical transmission line and the cause of the fault.

Abstract: The optical amplifier according to the present invention is constructed such that the amount of the electric current fed to the power feeding line 2a is first detected by the current detection means, and then a setting signal is generated to each of the bypass circuits 22 and 23 in accordance with the thus detected amount of the fed current, and thereafter the output level of each of the optical repeater circuits 11 and 12 is controlled respectively by the bypass circuits 22 and 23, so that the output level of these repeater circuits 11 and 12 can be controlled in accordance with the amount of the current fed to the power feeding line 2a.

Abstract: The optical amplifier according to the present invention is constructed such that the amount of the electric current fed to the power feeding line 2a is first detected by the current detection means, and then a setting signal is generated to each of the bypass circuits 22 and 23 in accordance with the thus detected amount of the fed current, and thereafter the output level of each of the optical repeater circuits 11 and 12 is controlled respectively by the bypass circuits 22 and 23, so that the output level of these repeater circuits 11 and 12 can be controlled in accordance with the amount of the current fed to the power feeding line 2a.

Abstract: A dispersion compensating optical transmission line comprises a plurality of optical transmission fibers for transmitting signal light, at least one first dispersion compensator disposed at a first dispersion compensating cycle for compensating an accumulated chromatic dispersion of the signal light so that an average chromatic dispersion is equal to a first desired value, and a plurality of second dispersion compensators disposed at a second dispersion compensating cycle shorter than the first dispersion compensating cycle for compensating the accumulated chromatic dispersion of the signal light so that an average chromatic dispersion is equal to a second desired value which absolute value is larger than that of the first desired value.