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Wavelength Division Multiplexing (WDM) is used in fiber optic communications; it is a
technology which multiplexes a number of optical carrier signals onto a single optical fiber by
using different wavelengths (i.e., colors) of laser light. This technique enables bidirectional
communications over one strand of fiber, as well as multiplication of capacity.

Time-division multiplexing (TDM) is a digital (or in rare cases, analogue) technology which uses
time, instead of space or frequency, to separate the different data streams. TDM involves
sequencing groups of a few bits or bytes from each individual input stream, one after the other,
and in such a way that they can be associated with the appropriate receiver.

3.5 Machining – process and equipment in digital version

Machining is a manufacturing process involving different types of cutting tools, or discs, or
abrasive wheels, in order to remove material from a workpiece. Due to this characteristic, it is
considered as being a subtractive process. The removed material is the excess material over the
material which creates the final piece. The workpiece is usually a laminated or cast piece, but
the process is not limited to these two types.

Machining process is actually a family of processes that are presented in Table 3.1.

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