Abstract: 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.

Abstract: 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).

Abstract: 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).

Abstract: 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.