U.S. Philips Corporation

Johannes T Kluitmans

Pieter W Hooijmans

Hindrik Tjassens

Giok D Khoe

Hendrikus G Kock

Abram Van De Grijp

In an optical telecommunication system having a direct-access optical transmission medium, a plurality of send/receive terminals may communicate with each other on different optical carriers. In order to make it possible for a terminal which is already in communication with a second terminal to also transmit to or receive a message from a third terminal, each terminal includes modulation and demodulation circuits for modulating/demodulating particular message signals on particular subcarriers. Signals received from different terminals can thereby be distinguished from each other on the basis of their respective subcarriers.

Coherent optical telecommunication network wherein each send/receive

A bidirectional coherent optical transmission system comprises two stations (I and II) each having only a single laser (2, 9), part of the light signal generated by the laser being fed to a glass fibre T and another part of the light signal generated by the laser being used for mixing the received light signal down to an intermediate frequency by means of a photoelectric diode (4, 11). In contradistinction to the prior art transmission system, in the system according to the invention the light signal is modulated by applying a modulation signal to each of the lasers (2, 9).

Coherent optical heterodyne transmission system

A laser diode module includes a rectangular box-shaped metal casing having a bottom (B), an even number of guide pins (1-14) being led through the bottom (B) in a standardized DIL order. In addition to the laser diode itself (LD) the laser diode module further includes a metal base carrier (BC) on which the laser diode (LD), a photo diode (PD) and a support (S) for the glass fiber (F) are installed. The laser diode module further includes a guide pin (9) which is inserted in the bottom (B) by means of a feedthrough insulator for electrically connecting the laser diode module to an external transmission line (MT). In order to achieve a proper matching of the laser diode module and the characteristic impedance of the external transmission line (MT), so that reflection phenomena are avoided and the laser diode module is made suitable for use in systems with considerably higher bit rates than 1 Gbit/s, the aforesaid guide pin (9) forms the inner guide of a coaxial transmission line situated inside the casing, of which transmission line the outer guide (CBL) is electrically conductively connected to the casing, whereas in the connecting line between the inner guide (9) and the laser diode (LD) a resistor (CS) is inserted having a value such that the sum of the resistances of this resistor (CS) and the laser diode (LD) is substantially equal to the characteristic impedance of the coaxial transmission line (9, CBL).

Laser diode module

A laser diode module comprises a rectangular, box-like metal casing having a bottom (B), whereas an even number of guide pins (1-14) are passed through the bottom (B) in a standardized DIL order and no less than one guide pin (5) is electroconductively connected to the bottom (B). In addition to the laser diode (LD) itself the module further includes a Peltier cooler (TEC) and a thermal metal base carrier (BC) coupled thereto, which base carrier accommodates the laser diode (LD), a photodiode (PD), a support (S) for the glass fibre (F) and a thermistor (TH). In order to render this laser diode module suitable for use in communication systems with bit rates that exceed by far 1 Gbit/s, the said guide pin (5) has inside the casing a portion in the form of a rod with a constant cross-section and with no less than one flat side face which over its entire surface has an electroconductive coupling with the relevant long sidewall (SW.sub.1) of the casing, an electroconductive interconnecting strip being provided between the head face of the rod and the base carrier (BC).

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Eindhoven, Netherlands

Johannes T Kluitmans