Abstract: A CATV station apparatus subjects received optical signals to processes such as optical-electrical conversion, signal separation, coupling, and demodulation for obtaining an uplink signal. A received photocurrent monitoring section compares a received photocurrent at a optical receiving section with a predetermined reference current. If the received photocurrent is equal to or higher than the reference current, an amplifying section amplifies a signal output from a signal separating section at a predetermined level. If the received photocurrent is lower than the reference current, on the other hand, it is determined that a non-linear phenomenon, such as stimulated Brillouin scattering, has occurred in an optical fiber. The amplifying section then outputs a signal at a level which does not affect, even after being coupled with other signals, communications performed by other optical transmission systems.

Abstract: Provided is a multimode optical transmission system capable of reducing an influence of multimode dispersion occurring when an optical signal is transmitted in multimode. Light sources (101 to 10m) respectively convert inputted electrical signals into a plurality of optical signals respectively having different wavelengths, and respectively output the plurality of optical signals. A wavelength multiplexing section (200) performs wavelength multiplexing of the plurality of optical signals outputted from the light sources (101 to 10m), and outputs a resultant signal as a wavelength multiplexed signal. A multimode optical transmission path (300) optically transmits the wavelength multiplexed signal in multimode. A mode processing section (400) extracts, from the wavelength multiplexed signal transmitted through the multimode optical transmission path (300), a plurality of optical signals each being in a mode having a particular wavelength and a particular propagation constant.

Abstract: An angle modulator having an excellent noise characteristic and an excellent distortion characteristic independent of an unwanted wave component of an optical modulation signal is provided. The angle modulator (10) includes an optical SSB modulation section (103a), an optical SSB-SC modulation section (104a), and an optical angle modulation section (105). By performing intensity modulation on an output signal of the optical SSB modulation section (103a) at the optical SSB-SC modulation section (104a), an unwanted angle modulated signal is prevented from overlapping with an angle modulated signal outputted from an optical detection section (107). Further, by a filter (108) filtering only an angle modulated signal component which does not include the unwanted wave component among the angle modulated signal components outputted from the optical detection section (107), a distortion characteristic after angle demodulation can be prevented from deteriorating.

Abstract: A wireless communication system capable of keeping a level of a wireless signal received by a relay apparatus within a predetermined dynamic range. In a control apparatus, a transmitting section converts a downstream electric signal into a downstream optical signal and transmits the downstream optical signal to the relay apparatus via an optical transmission path. The relay apparatus converts the received downstream optical signal into a downstream electric signal and transmits the downstream electric signal as a wireless signal to a wireless communication terminal from a transmitting/receiving antenna section. In the relay apparatus, a level adjustment section adjusts the level of the wireless signal transmitted by the relay apparatus such that the receiving level of the wireless signal received by the relay apparatus is kept within a predetermined range.

Abstract: A wireless access system is provided which prevents the occurrence of a hidden terminal problem and minimizes the reduction in throughput. In the wireless access system, an access point divides terminals into groups such that terminals in one group cannot recognize radio waves sent from terminals in another group, and performs communication with the terminals on a per-group basis. By this, the wireless access system avoids the occurrence of the hidden terminal problem. RTS/CTS packets used to avoid the occurrence of the hidden terminal problem are exchanged between the access point and the terminals on a per-group basis, whereby overhead is reduced and the reduction in throughput is minimized.

Abstract: A multimode optical transmission system reduces a deterioration of a noise characteristic and a distortion characteristic caused by an interference between modes. In an optical transmitter, a signal output section outputs a predetermined signal based on an inputted electrical signal. A control section controls the signal output section so as to adjust a frequency component of the signal outputted by the signal output section based on group delay information of modes which propagate in a multimode optical transmission line. An electric-optic conversion section converts, into an optical signal, the signal outputted by the signal output section, and transmits the optical signal via the multimode optical transmission line.

Abstract: An optical modulator comprises an electrode 21 which applies to an optical waveguides 12 of a Mach-Zehnder type optical interference system a first electric signal based on an alternating current signal S1 and a direct current bias V1, an electrode 22 which applies to an optical waveguide 13 of the Mach-Zehnder type optical interference system a second electric signal based on an alternating current signal S2 and a direct current bias V2, and a bias setting section 41 which sets average direct current levels of the first and second electric signals based on signal frequency information D1 which indicates a magnitude relation between a maximum frequency of the alternating current signal S1 and a maximum frequency of the alternating current signal S2.

Abstract: An optical transmission device is provided with an external optical modulator including three or more Mach-Zehnder interferometers and outputs a single-sideband optical intensity-modulated signal with suppressed optical carrier component, wherein an optical carrier component and an unnecessary one sideband component contained in the outputted optical signal are suppressed. A light branching section (51) branches an optical signal outputted by an external optical modulator (4) into two signals. A photodetector section (52) converts one of the optical signals to an electric signal. An optical carrier component extracting section (54) extracts an optical carrier component signal that is in the vicinity of a frequency f1 from the electric signal. An optical carrier component suppressing section (56) applies a bias voltage for suppressing the optical carrier component to the external optical modulator (4) based on the signal level of the optical carrier component.

Abstract: The present invention provides a wideband modulated signal generating device capable of realizing an always stable operation and obtaining an intended wideband modulated signal in spite of a shift in the optimal bias voltage due to DC drift occurring in an optical intensity modulation section. In the wideband modulated signal generating device, a DC power supply control section 50 controls a first DC power supply 51 and a second DC power supply 52 for applying first and second bias voltages to an optical intensity modulation section 30 based on a signal level detected by a level detecting section 70, and controls a third DC power supply 53 for applying a third bias voltage to an optical intensity modulation section 30 based on a distortion level detected by a distortion level detecting section 81, thus compensating for a shift in the optimal bias voltage occurring due to DC drift.

Abstract: An optical SSB-SC modulation section 13 subjects an optical signal fa outputted from an optical source 11 to an optical SSB-SC modulation based on the amplitude of an external electric signal fc to thereby output an optical intensity-modulated signal. An optical phase modulation section 14 subjects the optical signal fa to an optical phase modulation based on the amplitude levels of the first to nth external electric signals having frequencies f1 to fn to thereby output the resultant signal as an optical phase-modulated signal. An optical combining section 15 combines together the optical intensity-modulated signal and the optical phase-modulated signal. An optical detecting section 16 performs an optical homodyne detection through a squared detection of the optical intensity-modulated signal and the optical phase-modulated signal combined together to thereby produce a wideband modulated signal, being the difference beat signal between the two optical signals.

Abstract: The present invention provides an optical transmission device 100 capable of solving the problem of an unnecessary residual sideband components to thereby obtain a high-quality optical intensity-modulated signal in a case where an SSB optical modulation section 20 has wavelength dependence and a manufacturing error. In the optical transmission device 100, where the SSB optical modulation section 20 cannot evenly branch the intensity of the optical carrier into two routes of optical waveguide, the amplitude adjusting section 62 adjusts the amplitude of an electric signal that changes the refractive index of the SSB optical modulation section 20 so that the unnecessary sideband component of the optical intensity-modulated signal outputted from the SSB optical modulation section 20 disappears.

Abstract: Provided in a wireless LAN transmission system, having convenience and improved security, in which a wireless communication terminal located in a wireless communication area is capable of changing a setting of a connection, and capable of disconnecting the wireless communication terminal from the connection if the connection is unnecessary. A control management section (7) controls a switching section (5) based on an initial setting (S001). When a beacon signal transmitted from the wireless communication terminal is detected in a signal monitoring block (8) (S002), the control management section switches an operation of the switching section (5) so as to transmit signals outputted from all of at least one access point (4) to the wireless communication terminal (S003).

Abstract: The invention provides a NOx removal system for use in a boiler for realizing further reduction in NOx. Loading means for loading a reducing agent is provided at the outlet of a gas passageway in the boiler body, and a NOx removal catalyst is provided downstream of the loading means.

Abstract: A NOx removal system for boilers in which the need for any special heat retainer or any warming mechanism is eliminated. Ammonia jet nozzles are disposed on a gas passage of a boiler or flue, and an ammonia generator connected to the jet nozzles is disposed within the flue.

Abstract: A light emitting section outputs an optical signal having an intensity corresponding to a transmission timing signal, the optical signal modulated based on a radio transmission signal. A received photocurrent detection section detects an intensity of an optical signal received by a light receiving section. In accordance with the detected intensity, a high frequency amplification section amplifies the output signal of the light receiving section, and a transmission timing signal reconstruction section reconstructs the transmission timing signal.

Abstract: Provided is a multimode optical transmission system for reducing a deterioration of a noise characteristic and a distortion characteristic caused by an interference between modes. In an optical transmitter 11, a signal output section outputs a predetermined signal based on an inputted electrical signal. A control section 130 controls the signal output section so as to adjust a frequency component of the signal outputted by the signal output section based on group delay information of modes which propagate in a multimode optical transmission line 310. An electric-optic conversion section 110 converts, into an optical signal, the signal outputted by the signal output section, and transmits the optical signal via the multimode optical transmission line 310.

Abstract: A wireless access system is provided which prevents the occurrence of a hidden terminal problem and minimizes the reduction in throughput. In the wireless access system, an access point (12) divides terminals into groups such that terminals in one group cannot recognize radio waves sent from terminals in another group, and performs communication with the terminals on a per-group basis. By this, the wireless access system avoids the occurrence of the hidden terminal problem. RTS/CTS packets used to avoid the occurrence of the hidden terminal problem are exchanged between the access point (12) and terminals (131 to 133, 141 to 142) on a per-group basis, whereby overhead is reduced and the reduction in throughput is minimized.

Abstract: A SW (70) receives an Ethernet® signal from an outside of areas E and F. The SW (70) selects and outputs the obtained Ethernet® signal to any one of APs (91a to 91e) in accordance with a network structure managed by the SW (70). The AP (91a to 91e) converts the Ethernet® signal to an electrical signal type wireless LAN signal, which is in turn output to a main station (10). The main station (10) frequency-multiplexes the signal output from each of the APs (91a to 91e), and converts the signal to an optical signal, which is in turn output to sub-stations (20a and 20b) The sub-station (20a and 20b) transmits the signal transmitted from the main station (10) to a terminal in the form of a wireless radio wave. Thereby, when a plurality of communication areas are present, the accommodation capacity of an AP can be effectively utilized in each communication area.

Abstract: The present invention aims to provide a radio frequency optical transmission system having a simple structure while allowing a signal to be prevented from being lost due to the influence of chromatic dispersion without requiring considerably high adjustment accuracy. An optical intensity modulation section (14) of a control station (10) modulates an intensity of an optical signal generated by a light source (12) with a radio frequency signal, and divides the optical signal having its intensity modulated into two optical signals. The optical intensity modulation section (14) outputs one of the two optical signals without processing it, and the other optical signal is inverted (i.e. 180 out of phase) and outputted. The two optical signals are transmitted through two separate optical fibers (31 and 32) to base stations (21 through 2n). Each of the base stations (21 through 2n) receives one of the two optical signals transmitted via the two optical fibers (31 and 32).

Abstract: The present invention is directed to a wireless communication system capable of keeping a level of a wireless signal received by a relay apparatus (20) within a predetermined dynamic range. In a control apparatus (10), a transmitting section (102) converts a downstream electric signal into a downstream optical signal and transmits the downstream optical signal to the relay apparatus (20) via an optical transmission path (40). The relay apparatus (20) converts the received downstream optical signal into a downstream electric signal and transmits the downstream electric signal as a wireless signal to a wireless communication terminal (30) from a transmitting/receiving antenna section (204). In the relay apparatus (20), a level adjustment section (207) adjusts the level of the wireless signal transmitted by the relay apparatus (20) such that the receiving level of the wireless signal received by the relay apparatus is kept within a predetermined range.