Siemens Aktiengesellschaft

Herwig Trimmel

Siegfried Schoen

Baldur Stummer

Gerhard Thanhaeuser

Gerhard Kunde

Heinrich Keil

A phase-locked loop for controlling the phase of an output signal S,dependent on a reference signal S,with only a small phase timing error has a sampling circuit for sampling the reference signal S,with the output signal S,and for generating a sampling signal S,A, a jitter modulation circuit (,) for generating a sampling signal S,AJ delayed by a defined time duration and for alternating output of the undelayed sampling signal S,A and the delayed sampling signal S,AJ, a phase detector for acquiring an average phase difference between the output signal S,and the delayed and undelayed sampling signals S,A and S,AJ, and a controllable oscillator for generating the output signal S,with a frequency that is controllable dependent on the average phase difference acquired by the phase detector.

Phase-locked loop with small phase error

A desire exists in the optical transmission of optical signals to co-transmit a service channel or telemetry signals in the form of an additional low frequency signal over the light conductor, since a remote feed line or a service channel is not always installed parallel to the light conductor length. The requirement exists for the transmission of the additional signal that, in addition to a low additional expense, no disruption of the actual useful signal can occur. To this end, the control signal of a laser diode transmitter is modulated with the signal to be additionally transmitted and this light component is coupled out at the receiving side. The structure is particularly useful in optical transmission systems for very high frequency digital signals with bit rates above 100 Mbit/s.

Optical transmission system for high frequency digital signals

The invention relates to a method for the control of the preconduction current for laser diodes which are employed as light transmitters in the transmission stages of light wave guide transmission systems. In such laser diodes, a sharp bend occurs in the lower part of the light current characteristic curve which separates an upper characteristic curve area with great steepness from a lower characteristic curve area with minimum steepness and comparatively high cut-in retardation. Therefore, such laser diodes are operated with a preconduction current whose magnitude corresponds to the threshold current occurring in the characteristic curve bend. Due to aging and temperature influences, displacements of the characteristic curve bend can occur so that a control of the preconduction current is required. To this end, the invention provides that an oscillation of comparatiely lower frequency and low amplitude be superimposed on the preconduction current. A part of the light emitted by the laser diode is monitored for the occurrence of this additional oscillation. The inventive preconduction current regulation of laser diodes is particularly employable in light wave guide transmission systems with high transmission velocities.

Preconduction current control of laser diodes

A telephone subscriber station has a base set and a cordless hand set. The transmission between the base and hand set occurs by way of infrared transmitters and infrared receivers. Pulse phase modulation who is particularly suited for the speech transmission. Various functions are remotely controlled from the cordless hand set by the transmission of special characters. The special characters are transmitted as pulse sequences having differing frequencies. Thereby, a specific frequency is assigned to each special character. A call device comprises keys and a controllable pulse generator. A frequency recognition circuit is provided in the receiver at the base set and assigns the received pulse sequences to the special characters and has corresponding control functions. A monitoring circuit monitors the synchronization between the hand set and the base set and disconnects the telephone connection given a transmission which is disrupted over a longer interval.

Telephone subscriber station

A circuit which senses the time intervals during which a total current applied to a laser diode exceeds a second breakpoint value on the light-current characteristic curve and which generates an error signal that may be fed back to adjust a current modulator.

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Puchheim, Germany

Herwig Trimmel