Alcatel N.v.

Alcatel

Alcatel Sel Aktiengesellschaft

Other

Alcatal N.v.

Rolf Heidemann

Heinz G Krimmel

Jurgen Otterbach

Bernhard Junginger

Thomas Pfeiffer

Henning Bulow

Rainer Fritschi

Rolf Rossberg

Gustav Veith

Berthold Wedding

Horst Ohnsorge

Manfred Kaiser

Klaus Braun

Adolf Weygang

In a hybrid fiber/coax access network (NET) with downstream and upstream channels, the upstream channel serves to transmit voice and video signals as well as data signals from groups of customer locations (END) to a subcenter (HUB). A demarcation point (UP) provides the interface between the access network (NET) and the private network of the customer location (END). It contains at least two devices (BP,, BP,, BP,) for frequency-splitting received signals in the upstream frequency band, at least two switches (S,, S,, S,) following the at least two devices (BP,, BP,, BP,) and serving to block or unblock individual upstream frequency ranges, a measuring unit (MESS,) for measuring the amplitudes or intensities of the signals in the split frequency ranges, and a control unit (CTRL) for evaluating the measured values and controlling the at least two switches (S,, S,, S,). For a customer location (END), individual upstream frequency ranges can thus be telemetrically blocked for a limited time. Decentralized and autonomous monitoring of individual upstream frequency ranges is accomplished by a measuring unit which is controlled by the demarcation point (UP) itself.

Active demarcation point of an access network

Stationary interference signals from radio stations, for example, enter a transmission network (NET), e.g., a coaxial cable network with return channel, and impair the transmission of broadband signals, e.g., data, in the upstream frequency band, since they lie in the same frequency range. The tranmitting/receiving unit (SE,) of a terminal (END) contains a receiving unit (EMP,) for receiving frequency values of stationary interference signals induced in the transmission link, a memory (MEMO,) for storing the received frequency values, a generator (SG,, NG,) for generating a spreading function with spectral zeros at frequency values which are determined from the stored frequency values, and a multiplier (MUL,) for multiplying the broadband signals to be transmitted by the generated spreading function with spectral zeros. The spectral zeros are so generated that, if the spreading function with the spectral zeros is multiplied by the individual interference signals, at least one of the spectral zeros is located in the frequency range of the broadband signals, so that when the broadband signals are despread at a center (ZE), the impairment caused by the interference signals is reduced.

Transmitting/receiving facility and method for transmitting broadband signals as well as transmitting/receiving facility for receiving broadband signals

A transition between a microstrip line and waveguide is proposed, wherein the ground surface of the microstrip line has an aperture and the ground surface of the microstrip line forms at least part of a wall of the waveguide.

Transition from a microstrip line to a waveguide and use of such

An electrical transmission system is indicated, in which a broadband distribution network (2) has a center (1) and a number of terminals (26) connected thereto, which can receive TV and Audio signals emitted by the center (1), and individual subscriber signals, and which can send upstream signals to the center (1). The broadband distribution network (2) has a number of amplifiers (10) that are close to the subscribers, to which a group of terminals (26) is connected, each of which is connected to a back-channel facility (4). The back-channel facility (4) is connected to a two-wire line (21) which is indirectly connected to the center (1). The back-channel facility (4) evaluates the upstream signals sent by a group of terminals (26).

Electrical transmission system with a broadband distribution network for

Stationary interference signals from radio stations, for example, enter a transmission network (NET), e.g., a coaxial cable network with return channel, and impair the transmission of broadband signals, e.g., data, in the upstream frequency band, since they lie in the same frequency range. The transmitting/receiving unit (SE1) of a terminal (END) contains a receiving unit (EMP1) for receiving frequency values of stationary interference signals induced in the transmission link, a memory (MEMO1) for storing the received frequency values, a generator (SG1, NG1) for generating a spreading function with spectral zeros at frequency values which are determined from the stored frequency values, and a multiplier (MUL1) for multiplying the broadband signals to be transmitted by the generated spreading function with spectral zeros. The spectral zeros are so generated that, if the spreading function with the spectral zeros is multiplied by the interference signals, at least one of the spectral zeros is located in the frequency range of the broadband signals, so that when the broadband signals are despread at a center (ZE), the impairment caused by the interference signals is reduced.

Transmitting/receiving facility and method for transmitting broadband

In an optical communication system in which cable-television signals and subscriber-assigned tele-communication signals are transmitted over a passive optical network (4, 5) to at least one optical network termination (6), each optical network termination (6) requires two optical-to-electrical transducers. An optical network termination (6) is disclosed which requires only one optical-to-electrical transducer (24). The system has two transmitting devices (1, 2) which each transmit a respective optical signal (O.sub.TV, O.sub.D). In the second transmitting device (2), a second electric signal (S.sub.D), whose energy occupies a second frequency band (FB2), is processed in such a way that the energy is concentrated in a subband lying outside the first frequency band (FB1) of a first electric signal (S.sub.TV). The optical-to-electrical transducer (24) in the optical network termination (6) converts the received optical signals (O.sub.TV, O.sub.D) to an electric multiplex signal (E.sub.MUX), from which the two electric signals (S.sub.TV, S.sub.D) are recovered.

Optical communication system for cable-television signals and for

In known optical distribution systems, a signal intended for the subscribers is distributed from a transmitting point to all network terminations (point-to-multipoint transmission). The receivers, which are connected to a passive optical network, are adapted to a common bit rate. If a need for a higher data rate arises at a network termination, this need can only be satisfied in the prior art by converting all receivers. This is not possible without interrupting the service. Furthermore, the conversion entails great expense, since the receivers of these network terminations where the need for information is unchanged have to be converted as well. By a time-division-multiplexing method, a time-division multiplex signal is generated which has a frame whose duration is equal to one bit period (T) of a digital signal, and which is divided into k time slots (ZS). At least two time slots (ZS) are used for one digital signal, and one respective time slot (ZS) is used for each of the remaining digital signals.

Time-division-multiplexing method and apparatus

The invention relates to a heterodyne receiver, preferably for multichannel reception, especially for the reception of optical signals, in which the received signal is mixed with an oscillator signal of an oscillator in a mixing stage, to generate an intermediate frequency in an intermediate frequency stage (IF stage). According to the invention, the frequency (f.sub.LO) of the oscillator is tuneable discontinuously in jumps (Sp1, Sp2), and the intermediate frequency stage is tuneable continuously.

Apparatus for the optical heterodyne reception of signals

A laser (2) of an optical transmitter (1) for the transmission of an analog broadband signal for CATV in particular, can be amplitude-modulated in two different manners with an intelligence signal (N). Direct modulation can lead to an undesired additional frequency modulation. With indirect modulation by means of an optical intensity modulator (3), Brillouin scattering occurs at powers of approximately 10 mW in an optical fiber of the transmission path connected to the optical transmitter (1). Both modulations lead to distortions of the transmitted signal. In order to avoid the disadvantages of both modulations in a technically simple fashion, the carrier emitted from a laser (2) is indirectly modulated with an intelligence signal (N) and the laser (2) also faintly directly modulated with an energy-dispersing signal (V). The faint direct modulation leads to a constant, limited wave length alteration of the optical signal, such that Brillouin scattering is reduced, simultaneously with the avoidance of dispersion distortions.

Optical transmitter

The input light in fiber-optic amplifiers is monitored in order to turn off the system in which it is contained, or individual components of the system, e.g. the fiber-optic amplifier itself, when input light is lacking. To that effect, in known fiber-optic amplifiers, a portion of the input light is coupled out by a coupler. However, this coupler has disadvantages; e.g. the signal-to-noise ratio deteriorates. To monitor the input light, the fiber-optic amplifier of the present invention uses a device (4), which couples out and evaluates the pump light that was not absorbed by the section of the optical waveguide (2).

Fiber-optic amplifier with a device for monitoring the input power

It is desirable to offer the subscribers of a cable television distribution network, in addition to the cable TV service, a video-on-demand service. Since, in the foreseeable future, the fiber-optic portion of the cable television distribution networks will not extend to the subscribers (111) but will terminate in optical network terminations (ONT.sub.i) from which a respective optical access network (108-110) will extend to the subscribers, the problem arises how to transmit the entirety of subscriber-assigned video signals to the subscribers so that the latter can receive the requested video signals. According to the invention, the transmission from the center (100) through the fiber-optic distribution network (101-107) to the optical network terminations (ONT.sub.i) is digital, using time- and wavelength-division multiplexing. In each optical network termination, only that portion of subscriber-assigned video signals is removed which is intended for subscribers connected to the optical network termination (ONT.sub.i). The removed subscriber-assigned video signals are modulated onto subcarriers (M.sub.1 -M.sub.6) and frequency-division-multiplexed with the cable TV signals which are distributed over the electrical access network (108-110) to the subscribers ( 111) connected to the optical network termination.

Cable television distribution network with video-on-demand transmission

Known optical amplifiers, which are used in a light transmission path to amplify the light signals to be transmitted, have the disadvantage that the semiconductor lasers, used as pump lasers therein, are very sensitive to feedback. According to the invention, the operating current of such pump lasers (4) is modulated at a high frequency, which causes the pump laser to operate in a multi-mode, thereby making it insensitive to feedback. For example, the operating current is DC, on which AC is superimposed. In the event the optical amplifier has two pump lasers, their operating current is also modulated. Both pump lasers are then advantageously alternately switched on and off at a sufficiently high switching frequency, which also prevents reciprocal interference.

Optical amplifier

If, in optical communication systems using fiber-optic amplifiers, the optical isolator at the input is omitted on cost grounds and because of the deterioration of the noise characteristics caused by the insertion loss, a giant pulse may be developed when a fiber-optic connector at the input is being separated. To avoid this occurrence, use is made of a monitoring device (7) which, when the power input to the fiber-optic amplifier (4, 5, 3, 6) drops below a given threshold, quickly turns off the current of the pump laser (4) or interrupts the light path of the pump laser (4).

Optical communication system with monitoring device for avoiding giant

A microwave generator has its microwave frequency optically phase-locked by means of a reference frequency of a reference signal, wherein at least one portion of an electronic circuit arrangement is supplied with an optical reference carrier signal modulated with the reference frequency. The circuit arrangement (16) includes two components (Q1 to Q6; Q10, Q11) based on different semiconductor types which are chosen so that one of them, the first component, which is of a first semiconductor type, optically responds to the reference carrier signal (3) and, thus, to the reference frequency (f.sub.1 Mod1. . . Modn) for achieving synchronization, and that--independently of the response of the first component--the other, second component, which is of a second semiconductor type, responds to an optical control carrier signal (6) differing in frequency from the reference carrier signal (3). The amplitude of the first component is controlled by means of a control signal (7) modulated onto the optical control carrier signal (6).

Microwave generator circuit having oscillator and controller responsive

An optical system includes a fiber-optic amplifier having a section of optical waveguide doped with a rare-earth element and a pump-light source for emitting pump light, the fiber-optic amplifier receiving signal light of a first wavelength and outputting at least signal light of a second wavelength. An optical-to-electrical transducer receives the signal light of the second wavelength from the fiber-optic amplifier and produces an electrical output signal. The signal light of the second wavelength is pump light which is unabsorbed in the section of optical waveguide.

Growing community of inventors

Tamm, Germany

Rolf Heidemann