Measuring probe adapted to be mounted to a probe head of a coordinate measuring machine for determination of at least one spatial coordinate of a measurement point on an object to be measured, the measuring probe comprising • an optical measuring unit adapted to provide distance measurements of measuring points at the object, an optical probe ferrule (24, 47, 48, 73), • a probe interface (21,31,41,42,51,52,71) which provides □ modular mounting of the measuring probe to a probe head of the coordinate measuring machine and □ transmission, in particular bidirectional transmission, of optical signals between the probe and the coordinate measuring machine, and • a protection unit (82,92) for the optical probe ferrule (24,47,48,73), the probe ferrule (24,47,48,73) being adapted and arranged to bi-directionally transmit optical signals from and to the measuring probe, characterised in that • the protection unit (82,92) is adapted to provide for dust-protection of the optical probe ferrule (24,47,48,73) of the measuring probe in an un-mounted state of the measuring probe, • the protection unit (82,92) comprises a protection element (83, 93) and is designed so that □ the probe ferrule (24,47,48,73) - in the un-mounted state - is protectable against contamination, in particular by dust, by the protection element (83,93) being positioned in a block-position so that the ferrule (24,47,48,73) is at least partly covered and a path for transmitting the optical signals is at least partly blocked and □ transmission of the optical signals by means of the probe ferrule (24,47,48,73) - in a mounted state - is provideable by the protection element (83,93) being positioned in an open-position so that the path is unblocked and • the protection unit (82,93) comprises a displacement mechanism which provides automatic displacement of the protection element (83,93) from the block-position into the open-position in the course of mounting of the optical probe to the probe head of the coordinate measuring machine. • an optical measuring unit adapted to provide distance measurements of measuring points at the object, an optical probe ferrule (24, 47, 48, 73), • a probe interface (21,31,41,42,51,52,71) which provides □ modular mounting of the measuring probe to a probe head of the coordinate measuring machine and □ transmission, in particular bidirectional transmission, of optical signals between the probe and the coordinate measuring machine, and □ modular mounting of the measuring probe to a probe head of the coordinate measuring machine and □ transmission, in particular bidirectional transmission, of optical signals between the probe and the coordinate measuring machine, and • a protection unit (82,92) for the optical probe ferrule (24,47,48,73), the probe ferrule (24,47,48,73) being adapted and arranged to bi-directionally transmit optical signals from and to the measuring probe, characterised in that • the protection unit (82,92) is adapted to provide for dust-protection of the optical probe ferrule (24,47,48,73) of the measuring probe in an un-mounted state of the measuring probe, • the protection unit (82,92) comprises a protection element (83, 93) and is designed so that □ the probe ferrule (24,47,48,73) - in the un-mounted state - is protectable against contamination, in particular by dust, by the protection element (83,93) being positioned in a block-position so that the ferrule (24,47,48,73) is at least partly covered and a path for transmitting the optical signals is at least partly blocked and □ transmission of the optical signals by means of the probe ferrule (24,47,48,73) - in a mounted state - is provideable by the protection element (83,93) being positioned in an open-position so that the path is unblocked and □ the probe ferrule (24,47,48,73) - in the un-mounted state - is protectable against contamination, in particular by dust, by the protection element (83,93) being positioned in a block-position so that the ferrule (24,47,48,73) is at least partly covered and a path for transmitting the optical signals is at least partly blocked and □ transmission of the optical signals by means of the probe ferrule (24,47,48,73) - in a mounted state - is provideable by the protection element (83,93) being positioned in an open-position so that the path is unblocked and • the protection unit (82,93) comprises a displacement mechanism which provides automatic displacement of the protection element (83,93) from the block-position into the open-position in the course of mounting of the optical probe to the probe head of the coordinate measuring machine.