Alcatel N.v.

Alcatel

Alcatel Alsthom Compagnie Generale D'electricite

Bernhard Junginger

Rolf Heidemann

Heinz G Krimmel

Joachim Selinger

Rainer Fritschi

A driver circuit for a polarization scrambler () having a number of electrodes () is characterized in that the driver circuit comprises at least one pulse source () emitting a pulsed signal at a fundamental frequency, that the driver circuit further comprises a plurality of passive filter and matching circuits () for said number of electrodes () of said polarization scrambler (), wherein each passive filter and matching circuit () is designed for driving one or several of the electrodes (), and wherein each passive filter and matching circuit () is designed such that it filters out at least one harmonic mode frequency of said pulsed signal. The inventive driver circuit has a low power consumption and generates only few heat.

Low power driver circuit for a polarization scrambler

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 optical communication system is described wherein a center (1) and distant terminals (3, 4) are connected to a fiber-optic network (2). Each of the terminals (3, 4) has a light source (5, 7) and a modulator (6, 8) connected thereto for transmitting optical signals to the center (1). Each of the modulators (6, 8) controls the respective light source (5, 7) in such a way that the light source (5, 7) emits light only within successive first time intervals T.sub.1L, T.sub.2L which are separated by second time intervals T.sub.1D, T.sub.2D and that the first time intervals T.sub.1L, T.sub.2L are shorter than the second time intervals T.sub.1D, T.sub.2D.

Optical communication system wherein optical beat interference at the

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

In an optical receiver of the prior art, a multistage fiber-optic amplifier in which optical signal components propagating along different paths in the same direction beat with one another generate noise in addition to the noise due to spontaneous emission in the amplifier. A two-stage fiber-optic amplifier, according to the invention is provided in which a first section of optical fiber (F1) is pumped opposite to or in the direction of propagation of the optical signal and a second section of optical fiber (F2) is pumped in or opposite to the direction of propagation. A pump-light source (1), the sections of optical fiber (F1, F2), and couplers (K1, K2, K3) are arranged in such a way that any signal components propagating along different paths in the same direction will not beat with one another.

Multistage fiber-optic amplifier

In a fiber-optic amplifier, which consists of at least one pump coupler (2) with a pumping light source (1) and an erbium-doped fiber length (7) which is spliced to the pump coupler (2), at least one detector is located in the splice area (12) between the fiber length (7) and the outgoing transmission line, to monitor the amplifier by measuring the scattered light coming from this splice area (12). An electrical evaluating device follows the detector.

Fiber optical amplifier having a detector for measuring scattered light

To compensate for nonlinear signal distortions in analog optical communication transmission systems, caused by laser chirps and the chromatic dispersion of the optical fiber, an equalizer in the form of an LC component is known, whose capacitance is formed by a variable capacitance diode. However, the known equalizer functions only when the capacitance has the proper polarity, which cannot be predicted because of possible polarity inversion during signal transmission. According to the invention, the variable capacitance diode (C.sub.a) has another variable capacitance diode (C.sub.b), with the opposite polarity, connected in parallel, and is equally biased in the high-resistance direction. By adjusting the bias voltage of both capacitances, it can be achieved that one of the two variable capacitance diodes takes over the equalization function, and the other is practically inoperative. Further developments of this solution concern keeping the frequency response constant during adjustment of the equalization, by means of a capacitance connected in parallel to the variable capacitance diodes (C.sub.a, C.sub.b), and the equalization of large bandwidth signals by an LC chain circuit with LC components according to the invention.

Equalizer for optical communication systems

To compensate for nonlinear distortions in analog optical communication transmission systems, caused by laser chirps and the chromatic dispersion of the optical fiber, an equalizer in the form of an LC component is known, whose capacitance is formed by a variable capacitance diode. If this equalizer is to be adjusted for considerable signal distortions (long transmission path length), it must operate at great capacitance, which reduces its bandwidth. In order to be able to equalize large bandwidth signals (e.g. 600 MHz) containing considerable distortions, the invention indicates an LC chain circuit with LC components of the known type, as the equalizer. Further developments of this solution concern the appropriate polarizing of the variable capacitance diode and maintaining the frequency response constant, when adjusting the equalization.

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Herrenberg, Germany

Bernhard Junginger