Koninklijke Philips Corporation N.v.

Aircision B.v.

John J E Reid

Daniele Raiteri

Robert C J Smets

Bas Van Der Wielen

FSO systems rely on line-of-sight, and thus can be easily impaired due to disruptions such as atmospheric turbulence. There is a need for a more robust communication system allowing longer distances to be bridged and/or downtime to be reduced. An optical transmitter is provided generating at least one optical alignment beam. The transmitter comprises at least one alignment modulator, to modulate the alignment beam with transmitter directional data. A suitable receiver may demodulate this information and use the directional data from the transmitter to simplify the attainment and/or maintenance of a sufficient degree of alignment. Additionally or alternatively, the at least one alignment beam may be used to detect, characterize and/or monitor one or more environmental parameters.

Optical communication transmitter and receiver with misalignment measurement and correction

In an optical transmission system a transmitter ( ) generates a sequence of time domain division multiplexed pulses and transmits them via an optical transmission medium ( ) to a receiver ( ). In the receiver ( ) the received optical multiplex signal is applied to an optical demultiplexer ( ) and to a clock recovery element ( ). The clock recovery element ( ) generates optical clock pulses which are used to control optically controlled optical switches ( ) which demultiplex the optical signal. The optical clock recovery circuit is based on a laser which is mode locked by the received optical signal. The mode locked laser comprises an optical amplifier ( ) having its output coupled to its input by a feedback loop comprising a polarization controller ( ), a saturable absorber ( ), a coupling element ( ) and a adjustable delay ( ). The received optical signal is coupled into the feedback loop by means of the coupling element ( ). The saturable absorber ( ) comprises a 3 dB, 90&deg; coupling element ( ) being coupled to a secondary loop. Said secondary loop comprises an attenuator ( ) and an amplifier ( ). The amplifier ( ) is placed asymmetrically in the secondary loop. Due to the non-linearity in the secondary loop, the optical pulses propagating in the secondary loop interfere destructively for low signal levels, and interfere constructively for high signal levels.

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Eindhoven, Netherlands

John J E Reid