The invention relates to a method of taking measurements along an optical transmission path by means of an optical sensor. The optical sensor includes an optical converter whose optical attenuation properties can be influenced according to the value to be measured and through which a first beam portion of a high-frequency amplitude-modulated optical transmission beam is passed. A second beam portion of this transmission beam is conveyed via a delay element. The second beam portion is applied together with the first beam portion outputted by the optical converter, via the transmission path as a receive beam to the receiver arrangement. In this way the modulation change produced by the sensor is processed and evaluated as an information about the measure value. Measuring a value at the transmitter end is possible with any optical transmission path of an undefined length, without recalibration of the receiver arrangement, because the optical transmitter beam is additionally subjected to low-frequency modulation. An original modulation factor m.sub.o of the transmission beam is preset as the ratio of the high-frequency (I.sub.HF) to the low-frequency (I.sub.NF) modulation amplitude and is fed the receiver arrangement 3. The received sensor-influenced modulation factor of the receive beam is measured by the receive arrangement 3. The received-to-original modulation signal ratio is evaluated as information about the measuring value (M).
In a tool for measuring optical power on a fiber optic cable link, optical conditioning means in conjunction with a splitter are used to achieve measurement consistency and repeatability. In accordance with preferred embodiments of the present invention, light conditioning means are provided by disposing the optical fiber cable in a position so as to achieve mode filtering. This may be accomplished either by disposing the optical fiber in a coil, as for example in a mandrel, or disposing the coil in a series of serpentine or zig-zag paths.
A system for transmitting, over an optical transmission path using an optical fiber, wavelength-multiplex signals of a plurality of channels to which different wavelengths are assigned, the system comprising an optical transmission terminal station for transmitting the wavelength-multiplex signals to the optical transmission path, an optical reception terminal station for receiving the wavelength-multiplex signals from the optical transmission path, and at least one of ADD/Drop-Multiplexer nodes each including at least a demultiplexer unit for demultiplexing a plurality of channels to a channel in accordance with a given wavelength and a multiplexer unit for multiplexing a plurality of channels in accordance with a given wavelength, wherein optical pulses having pulse waveforms with an equal full-width at half-maximum are applied to the optical signals.
